| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * linux/mm/filemap.c |
| 4 | * |
| 5 | * Copyright (C) 1994-1999 Linus Torvalds |
| 6 | */ |
| 7 | |
| 8 | /* |
| 9 | * This file handles the generic file mmap semantics used by |
| 10 | * most "normal" filesystems (but you don't /have/ to use this: |
| 11 | * the NFS filesystem used to do this differently, for example) |
| 12 | */ |
| 13 | #include <linux/export.h> |
| 14 | #include <linux/compiler.h> |
| 15 | #include <linux/dax.h> |
| 16 | #include <linux/fs.h> |
| 17 | #include <linux/sched/signal.h> |
| 18 | #include <linux/uaccess.h> |
| 19 | #include <linux/capability.h> |
| 20 | #include <linux/kernel_stat.h> |
| 21 | #include <linux/gfp.h> |
| 22 | #include <linux/mm.h> |
| 23 | #include <linux/swap.h> |
| 24 | #include <linux/swapops.h> |
| 25 | #include <linux/syscalls.h> |
| 26 | #include <linux/mman.h> |
| 27 | #include <linux/pagemap.h> |
| 28 | #include <linux/file.h> |
| 29 | #include <linux/uio.h> |
| 30 | #include <linux/error-injection.h> |
| 31 | #include <linux/hash.h> |
| 32 | #include <linux/writeback.h> |
| 33 | #include <linux/backing-dev.h> |
| 34 | #include <linux/pagevec.h> |
| 35 | #include <linux/security.h> |
| 36 | #include <linux/cpuset.h> |
| 37 | #include <linux/hugetlb.h> |
| 38 | #include <linux/memcontrol.h> |
| 39 | #include <linux/shmem_fs.h> |
| 40 | #include <linux/rmap.h> |
| 41 | #include <linux/delayacct.h> |
| 42 | #include <linux/psi.h> |
| 43 | #include <linux/ramfs.h> |
| 44 | #include <linux/page_idle.h> |
| 45 | #include <linux/migrate.h> |
| 46 | #include <linux/pipe_fs_i.h> |
| 47 | #include <linux/splice.h> |
| 48 | #include <asm/pgalloc.h> |
| 49 | #include <asm/tlbflush.h> |
| 50 | #include "internal.h" |
| 51 | |
| 52 | #define CREATE_TRACE_POINTS |
| 53 | #include <trace/events/filemap.h> |
| 54 | |
| 55 | /* |
| 56 | * FIXME: remove all knowledge of the buffer layer from the core VM |
| 57 | */ |
| 58 | #include <linux/buffer_head.h> /* for try_to_free_buffers */ |
| 59 | |
| 60 | #include <asm/mman.h> |
| 61 | |
| 62 | #include "swap.h" |
| 63 | |
| 64 | /* |
| 65 | * Shared mappings implemented 30.11.1994. It's not fully working yet, |
| 66 | * though. |
| 67 | * |
| 68 | * Shared mappings now work. 15.8.1995 Bruno. |
| 69 | * |
| 70 | * finished 'unifying' the page and buffer cache and SMP-threaded the |
| 71 | * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> |
| 72 | * |
| 73 | * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> |
| 74 | */ |
| 75 | |
| 76 | /* |
| 77 | * Lock ordering: |
| 78 | * |
| 79 | * ->i_mmap_rwsem (truncate_pagecache) |
| 80 | * ->private_lock (__free_pte->block_dirty_folio) |
| 81 | * ->swap_lock (exclusive_swap_page, others) |
| 82 | * ->i_pages lock |
| 83 | * |
| 84 | * ->i_rwsem |
| 85 | * ->invalidate_lock (acquired by fs in truncate path) |
| 86 | * ->i_mmap_rwsem (truncate->unmap_mapping_range) |
| 87 | * |
| 88 | * ->mmap_lock |
| 89 | * ->i_mmap_rwsem |
| 90 | * ->page_table_lock or pte_lock (various, mainly in memory.c) |
| 91 | * ->i_pages lock (arch-dependent flush_dcache_mmap_lock) |
| 92 | * |
| 93 | * ->mmap_lock |
| 94 | * ->invalidate_lock (filemap_fault) |
| 95 | * ->lock_page (filemap_fault, access_process_vm) |
| 96 | * |
| 97 | * ->i_rwsem (generic_perform_write) |
| 98 | * ->mmap_lock (fault_in_readable->do_page_fault) |
| 99 | * |
| 100 | * bdi->wb.list_lock |
| 101 | * sb_lock (fs/fs-writeback.c) |
| 102 | * ->i_pages lock (__sync_single_inode) |
| 103 | * |
| 104 | * ->i_mmap_rwsem |
| 105 | * ->anon_vma.lock (vma_merge) |
| 106 | * |
| 107 | * ->anon_vma.lock |
| 108 | * ->page_table_lock or pte_lock (anon_vma_prepare and various) |
| 109 | * |
| 110 | * ->page_table_lock or pte_lock |
| 111 | * ->swap_lock (try_to_unmap_one) |
| 112 | * ->private_lock (try_to_unmap_one) |
| 113 | * ->i_pages lock (try_to_unmap_one) |
| 114 | * ->lruvec->lru_lock (follow_page->mark_page_accessed) |
| 115 | * ->lruvec->lru_lock (check_pte_range->isolate_lru_page) |
| 116 | * ->private_lock (page_remove_rmap->set_page_dirty) |
| 117 | * ->i_pages lock (page_remove_rmap->set_page_dirty) |
| 118 | * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) |
| 119 | * ->inode->i_lock (page_remove_rmap->set_page_dirty) |
| 120 | * ->memcg->move_lock (page_remove_rmap->folio_memcg_lock) |
| 121 | * bdi.wb->list_lock (zap_pte_range->set_page_dirty) |
| 122 | * ->inode->i_lock (zap_pte_range->set_page_dirty) |
| 123 | * ->private_lock (zap_pte_range->block_dirty_folio) |
| 124 | * |
| 125 | * ->i_mmap_rwsem |
| 126 | * ->tasklist_lock (memory_failure, collect_procs_ao) |
| 127 | */ |
| 128 | |
| 129 | static void page_cache_delete(struct address_space *mapping, |
| 130 | struct folio *folio, void *shadow) |
| 131 | { |
| 132 | XA_STATE(xas, &mapping->i_pages, folio->index); |
| 133 | long nr = 1; |
| 134 | |
| 135 | mapping_set_update(&xas, mapping); |
| 136 | |
| 137 | /* hugetlb pages are represented by a single entry in the xarray */ |
| 138 | if (!folio_test_hugetlb(folio)) { |
| 139 | xas_set_order(&xas, folio->index, folio_order(folio)); |
| 140 | nr = folio_nr_pages(folio); |
| 141 | } |
| 142 | |
| 143 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| 144 | |
| 145 | xas_store(&xas, shadow); |
| 146 | xas_init_marks(&xas); |
| 147 | |
| 148 | folio->mapping = NULL; |
| 149 | /* Leave page->index set: truncation lookup relies upon it */ |
| 150 | mapping->nrpages -= nr; |
| 151 | } |
| 152 | |
| 153 | static void filemap_unaccount_folio(struct address_space *mapping, |
| 154 | struct folio *folio) |
| 155 | { |
| 156 | long nr; |
| 157 | |
| 158 | VM_BUG_ON_FOLIO(folio_mapped(folio), folio); |
| 159 | if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) { |
| 160 | pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", |
| 161 | current->comm, folio_pfn(folio)); |
| 162 | dump_page(&folio->page, "still mapped when deleted"); |
| 163 | dump_stack(); |
| 164 | add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
| 165 | |
| 166 | if (mapping_exiting(mapping) && !folio_test_large(folio)) { |
| 167 | int mapcount = page_mapcount(&folio->page); |
| 168 | |
| 169 | if (folio_ref_count(folio) >= mapcount + 2) { |
| 170 | /* |
| 171 | * All vmas have already been torn down, so it's |
| 172 | * a good bet that actually the page is unmapped |
| 173 | * and we'd rather not leak it: if we're wrong, |
| 174 | * another bad page check should catch it later. |
| 175 | */ |
| 176 | page_mapcount_reset(&folio->page); |
| 177 | folio_ref_sub(folio, mapcount); |
| 178 | } |
| 179 | } |
| 180 | } |
| 181 | |
| 182 | /* hugetlb folios do not participate in page cache accounting. */ |
| 183 | if (folio_test_hugetlb(folio)) |
| 184 | return; |
| 185 | |
| 186 | nr = folio_nr_pages(folio); |
| 187 | |
| 188 | __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr); |
| 189 | if (folio_test_swapbacked(folio)) { |
| 190 | __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr); |
| 191 | if (folio_test_pmd_mappable(folio)) |
| 192 | __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr); |
| 193 | } else if (folio_test_pmd_mappable(folio)) { |
| 194 | __lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr); |
| 195 | filemap_nr_thps_dec(mapping); |
| 196 | } |
| 197 | |
| 198 | /* |
| 199 | * At this point folio must be either written or cleaned by |
| 200 | * truncate. Dirty folio here signals a bug and loss of |
| 201 | * unwritten data - on ordinary filesystems. |
| 202 | * |
| 203 | * But it's harmless on in-memory filesystems like tmpfs; and can |
| 204 | * occur when a driver which did get_user_pages() sets page dirty |
| 205 | * before putting it, while the inode is being finally evicted. |
| 206 | * |
| 207 | * Below fixes dirty accounting after removing the folio entirely |
| 208 | * but leaves the dirty flag set: it has no effect for truncated |
| 209 | * folio and anyway will be cleared before returning folio to |
| 210 | * buddy allocator. |
| 211 | */ |
| 212 | if (WARN_ON_ONCE(folio_test_dirty(folio) && |
| 213 | mapping_can_writeback(mapping))) |
| 214 | folio_account_cleaned(folio, inode_to_wb(mapping->host)); |
| 215 | } |
| 216 | |
| 217 | /* |
| 218 | * Delete a page from the page cache and free it. Caller has to make |
| 219 | * sure the page is locked and that nobody else uses it - or that usage |
| 220 | * is safe. The caller must hold the i_pages lock. |
| 221 | */ |
| 222 | void __filemap_remove_folio(struct folio *folio, void *shadow) |
| 223 | { |
| 224 | struct address_space *mapping = folio->mapping; |
| 225 | |
| 226 | trace_mm_filemap_delete_from_page_cache(folio); |
| 227 | filemap_unaccount_folio(mapping, folio); |
| 228 | page_cache_delete(mapping, folio, shadow); |
| 229 | } |
| 230 | |
| 231 | void filemap_free_folio(struct address_space *mapping, struct folio *folio) |
| 232 | { |
| 233 | void (*free_folio)(struct folio *); |
| 234 | int refs = 1; |
| 235 | |
| 236 | free_folio = mapping->a_ops->free_folio; |
| 237 | if (free_folio) |
| 238 | free_folio(folio); |
| 239 | |
| 240 | if (folio_test_large(folio) && !folio_test_hugetlb(folio)) |
| 241 | refs = folio_nr_pages(folio); |
| 242 | folio_put_refs(folio, refs); |
| 243 | } |
| 244 | |
| 245 | /** |
| 246 | * filemap_remove_folio - Remove folio from page cache. |
| 247 | * @folio: The folio. |
| 248 | * |
| 249 | * This must be called only on folios that are locked and have been |
| 250 | * verified to be in the page cache. It will never put the folio into |
| 251 | * the free list because the caller has a reference on the page. |
| 252 | */ |
| 253 | void filemap_remove_folio(struct folio *folio) |
| 254 | { |
| 255 | struct address_space *mapping = folio->mapping; |
| 256 | |
| 257 | BUG_ON(!folio_test_locked(folio)); |
| 258 | spin_lock(&mapping->host->i_lock); |
| 259 | xa_lock_irq(&mapping->i_pages); |
| 260 | __filemap_remove_folio(folio, NULL); |
| 261 | xa_unlock_irq(&mapping->i_pages); |
| 262 | if (mapping_shrinkable(mapping)) |
| 263 | inode_add_lru(mapping->host); |
| 264 | spin_unlock(&mapping->host->i_lock); |
| 265 | |
| 266 | filemap_free_folio(mapping, folio); |
| 267 | } |
| 268 | |
| 269 | /* |
| 270 | * page_cache_delete_batch - delete several folios from page cache |
| 271 | * @mapping: the mapping to which folios belong |
| 272 | * @fbatch: batch of folios to delete |
| 273 | * |
| 274 | * The function walks over mapping->i_pages and removes folios passed in |
| 275 | * @fbatch from the mapping. The function expects @fbatch to be sorted |
| 276 | * by page index and is optimised for it to be dense. |
| 277 | * It tolerates holes in @fbatch (mapping entries at those indices are not |
| 278 | * modified). |
| 279 | * |
| 280 | * The function expects the i_pages lock to be held. |
| 281 | */ |
| 282 | static void page_cache_delete_batch(struct address_space *mapping, |
| 283 | struct folio_batch *fbatch) |
| 284 | { |
| 285 | XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index); |
| 286 | long total_pages = 0; |
| 287 | int i = 0; |
| 288 | struct folio *folio; |
| 289 | |
| 290 | mapping_set_update(&xas, mapping); |
| 291 | xas_for_each(&xas, folio, ULONG_MAX) { |
| 292 | if (i >= folio_batch_count(fbatch)) |
| 293 | break; |
| 294 | |
| 295 | /* A swap/dax/shadow entry got inserted? Skip it. */ |
| 296 | if (xa_is_value(folio)) |
| 297 | continue; |
| 298 | /* |
| 299 | * A page got inserted in our range? Skip it. We have our |
| 300 | * pages locked so they are protected from being removed. |
| 301 | * If we see a page whose index is higher than ours, it |
| 302 | * means our page has been removed, which shouldn't be |
| 303 | * possible because we're holding the PageLock. |
| 304 | */ |
| 305 | if (folio != fbatch->folios[i]) { |
| 306 | VM_BUG_ON_FOLIO(folio->index > |
| 307 | fbatch->folios[i]->index, folio); |
| 308 | continue; |
| 309 | } |
| 310 | |
| 311 | WARN_ON_ONCE(!folio_test_locked(folio)); |
| 312 | |
| 313 | folio->mapping = NULL; |
| 314 | /* Leave folio->index set: truncation lookup relies on it */ |
| 315 | |
| 316 | i++; |
| 317 | xas_store(&xas, NULL); |
| 318 | total_pages += folio_nr_pages(folio); |
| 319 | } |
| 320 | mapping->nrpages -= total_pages; |
| 321 | } |
| 322 | |
| 323 | void delete_from_page_cache_batch(struct address_space *mapping, |
| 324 | struct folio_batch *fbatch) |
| 325 | { |
| 326 | int i; |
| 327 | |
| 328 | if (!folio_batch_count(fbatch)) |
| 329 | return; |
| 330 | |
| 331 | spin_lock(&mapping->host->i_lock); |
| 332 | xa_lock_irq(&mapping->i_pages); |
| 333 | for (i = 0; i < folio_batch_count(fbatch); i++) { |
| 334 | struct folio *folio = fbatch->folios[i]; |
| 335 | |
| 336 | trace_mm_filemap_delete_from_page_cache(folio); |
| 337 | filemap_unaccount_folio(mapping, folio); |
| 338 | } |
| 339 | page_cache_delete_batch(mapping, fbatch); |
| 340 | xa_unlock_irq(&mapping->i_pages); |
| 341 | if (mapping_shrinkable(mapping)) |
| 342 | inode_add_lru(mapping->host); |
| 343 | spin_unlock(&mapping->host->i_lock); |
| 344 | |
| 345 | for (i = 0; i < folio_batch_count(fbatch); i++) |
| 346 | filemap_free_folio(mapping, fbatch->folios[i]); |
| 347 | } |
| 348 | |
| 349 | int filemap_check_errors(struct address_space *mapping) |
| 350 | { |
| 351 | int ret = 0; |
| 352 | /* Check for outstanding write errors */ |
| 353 | if (test_bit(AS_ENOSPC, &mapping->flags) && |
| 354 | test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
| 355 | ret = -ENOSPC; |
| 356 | if (test_bit(AS_EIO, &mapping->flags) && |
| 357 | test_and_clear_bit(AS_EIO, &mapping->flags)) |
| 358 | ret = -EIO; |
| 359 | return ret; |
| 360 | } |
| 361 | EXPORT_SYMBOL(filemap_check_errors); |
| 362 | |
| 363 | static int filemap_check_and_keep_errors(struct address_space *mapping) |
| 364 | { |
| 365 | /* Check for outstanding write errors */ |
| 366 | if (test_bit(AS_EIO, &mapping->flags)) |
| 367 | return -EIO; |
| 368 | if (test_bit(AS_ENOSPC, &mapping->flags)) |
| 369 | return -ENOSPC; |
| 370 | return 0; |
| 371 | } |
| 372 | |
| 373 | /** |
| 374 | * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range |
| 375 | * @mapping: address space structure to write |
| 376 | * @wbc: the writeback_control controlling the writeout |
| 377 | * |
| 378 | * Call writepages on the mapping using the provided wbc to control the |
| 379 | * writeout. |
| 380 | * |
| 381 | * Return: %0 on success, negative error code otherwise. |
| 382 | */ |
| 383 | int filemap_fdatawrite_wbc(struct address_space *mapping, |
| 384 | struct writeback_control *wbc) |
| 385 | { |
| 386 | int ret; |
| 387 | |
| 388 | if (!mapping_can_writeback(mapping) || |
| 389 | !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) |
| 390 | return 0; |
| 391 | |
| 392 | wbc_attach_fdatawrite_inode(wbc, mapping->host); |
| 393 | ret = do_writepages(mapping, wbc); |
| 394 | wbc_detach_inode(wbc); |
| 395 | return ret; |
| 396 | } |
| 397 | EXPORT_SYMBOL(filemap_fdatawrite_wbc); |
| 398 | |
| 399 | /** |
| 400 | * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
| 401 | * @mapping: address space structure to write |
| 402 | * @start: offset in bytes where the range starts |
| 403 | * @end: offset in bytes where the range ends (inclusive) |
| 404 | * @sync_mode: enable synchronous operation |
| 405 | * |
| 406 | * Start writeback against all of a mapping's dirty pages that lie |
| 407 | * within the byte offsets <start, end> inclusive. |
| 408 | * |
| 409 | * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
| 410 | * opposed to a regular memory cleansing writeback. The difference between |
| 411 | * these two operations is that if a dirty page/buffer is encountered, it must |
| 412 | * be waited upon, and not just skipped over. |
| 413 | * |
| 414 | * Return: %0 on success, negative error code otherwise. |
| 415 | */ |
| 416 | int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
| 417 | loff_t end, int sync_mode) |
| 418 | { |
| 419 | struct writeback_control wbc = { |
| 420 | .sync_mode = sync_mode, |
| 421 | .nr_to_write = LONG_MAX, |
| 422 | .range_start = start, |
| 423 | .range_end = end, |
| 424 | }; |
| 425 | |
| 426 | return filemap_fdatawrite_wbc(mapping, &wbc); |
| 427 | } |
| 428 | |
| 429 | static inline int __filemap_fdatawrite(struct address_space *mapping, |
| 430 | int sync_mode) |
| 431 | { |
| 432 | return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
| 433 | } |
| 434 | |
| 435 | int filemap_fdatawrite(struct address_space *mapping) |
| 436 | { |
| 437 | return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
| 438 | } |
| 439 | EXPORT_SYMBOL(filemap_fdatawrite); |
| 440 | |
| 441 | int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
| 442 | loff_t end) |
| 443 | { |
| 444 | return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
| 445 | } |
| 446 | EXPORT_SYMBOL(filemap_fdatawrite_range); |
| 447 | |
| 448 | /** |
| 449 | * filemap_flush - mostly a non-blocking flush |
| 450 | * @mapping: target address_space |
| 451 | * |
| 452 | * This is a mostly non-blocking flush. Not suitable for data-integrity |
| 453 | * purposes - I/O may not be started against all dirty pages. |
| 454 | * |
| 455 | * Return: %0 on success, negative error code otherwise. |
| 456 | */ |
| 457 | int filemap_flush(struct address_space *mapping) |
| 458 | { |
| 459 | return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
| 460 | } |
| 461 | EXPORT_SYMBOL(filemap_flush); |
| 462 | |
| 463 | /** |
| 464 | * filemap_range_has_page - check if a page exists in range. |
| 465 | * @mapping: address space within which to check |
| 466 | * @start_byte: offset in bytes where the range starts |
| 467 | * @end_byte: offset in bytes where the range ends (inclusive) |
| 468 | * |
| 469 | * Find at least one page in the range supplied, usually used to check if |
| 470 | * direct writing in this range will trigger a writeback. |
| 471 | * |
| 472 | * Return: %true if at least one page exists in the specified range, |
| 473 | * %false otherwise. |
| 474 | */ |
| 475 | bool filemap_range_has_page(struct address_space *mapping, |
| 476 | loff_t start_byte, loff_t end_byte) |
| 477 | { |
| 478 | struct folio *folio; |
| 479 | XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT); |
| 480 | pgoff_t max = end_byte >> PAGE_SHIFT; |
| 481 | |
| 482 | if (end_byte < start_byte) |
| 483 | return false; |
| 484 | |
| 485 | rcu_read_lock(); |
| 486 | for (;;) { |
| 487 | folio = xas_find(&xas, max); |
| 488 | if (xas_retry(&xas, folio)) |
| 489 | continue; |
| 490 | /* Shadow entries don't count */ |
| 491 | if (xa_is_value(folio)) |
| 492 | continue; |
| 493 | /* |
| 494 | * We don't need to try to pin this page; we're about to |
| 495 | * release the RCU lock anyway. It is enough to know that |
| 496 | * there was a page here recently. |
| 497 | */ |
| 498 | break; |
| 499 | } |
| 500 | rcu_read_unlock(); |
| 501 | |
| 502 | return folio != NULL; |
| 503 | } |
| 504 | EXPORT_SYMBOL(filemap_range_has_page); |
| 505 | |
| 506 | static void __filemap_fdatawait_range(struct address_space *mapping, |
| 507 | loff_t start_byte, loff_t end_byte) |
| 508 | { |
| 509 | pgoff_t index = start_byte >> PAGE_SHIFT; |
| 510 | pgoff_t end = end_byte >> PAGE_SHIFT; |
| 511 | struct folio_batch fbatch; |
| 512 | unsigned nr_folios; |
| 513 | |
| 514 | folio_batch_init(&fbatch); |
| 515 | |
| 516 | while (index <= end) { |
| 517 | unsigned i; |
| 518 | |
| 519 | nr_folios = filemap_get_folios_tag(mapping, &index, end, |
| 520 | PAGECACHE_TAG_WRITEBACK, &fbatch); |
| 521 | |
| 522 | if (!nr_folios) |
| 523 | break; |
| 524 | |
| 525 | for (i = 0; i < nr_folios; i++) { |
| 526 | struct folio *folio = fbatch.folios[i]; |
| 527 | |
| 528 | folio_wait_writeback(folio); |
| 529 | folio_clear_error(folio); |
| 530 | } |
| 531 | folio_batch_release(&fbatch); |
| 532 | cond_resched(); |
| 533 | } |
| 534 | } |
| 535 | |
| 536 | /** |
| 537 | * filemap_fdatawait_range - wait for writeback to complete |
| 538 | * @mapping: address space structure to wait for |
| 539 | * @start_byte: offset in bytes where the range starts |
| 540 | * @end_byte: offset in bytes where the range ends (inclusive) |
| 541 | * |
| 542 | * Walk the list of under-writeback pages of the given address space |
| 543 | * in the given range and wait for all of them. Check error status of |
| 544 | * the address space and return it. |
| 545 | * |
| 546 | * Since the error status of the address space is cleared by this function, |
| 547 | * callers are responsible for checking the return value and handling and/or |
| 548 | * reporting the error. |
| 549 | * |
| 550 | * Return: error status of the address space. |
| 551 | */ |
| 552 | int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, |
| 553 | loff_t end_byte) |
| 554 | { |
| 555 | __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| 556 | return filemap_check_errors(mapping); |
| 557 | } |
| 558 | EXPORT_SYMBOL(filemap_fdatawait_range); |
| 559 | |
| 560 | /** |
| 561 | * filemap_fdatawait_range_keep_errors - wait for writeback to complete |
| 562 | * @mapping: address space structure to wait for |
| 563 | * @start_byte: offset in bytes where the range starts |
| 564 | * @end_byte: offset in bytes where the range ends (inclusive) |
| 565 | * |
| 566 | * Walk the list of under-writeback pages of the given address space in the |
| 567 | * given range and wait for all of them. Unlike filemap_fdatawait_range(), |
| 568 | * this function does not clear error status of the address space. |
| 569 | * |
| 570 | * Use this function if callers don't handle errors themselves. Expected |
| 571 | * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
| 572 | * fsfreeze(8) |
| 573 | */ |
| 574 | int filemap_fdatawait_range_keep_errors(struct address_space *mapping, |
| 575 | loff_t start_byte, loff_t end_byte) |
| 576 | { |
| 577 | __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| 578 | return filemap_check_and_keep_errors(mapping); |
| 579 | } |
| 580 | EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors); |
| 581 | |
| 582 | /** |
| 583 | * file_fdatawait_range - wait for writeback to complete |
| 584 | * @file: file pointing to address space structure to wait for |
| 585 | * @start_byte: offset in bytes where the range starts |
| 586 | * @end_byte: offset in bytes where the range ends (inclusive) |
| 587 | * |
| 588 | * Walk the list of under-writeback pages of the address space that file |
| 589 | * refers to, in the given range and wait for all of them. Check error |
| 590 | * status of the address space vs. the file->f_wb_err cursor and return it. |
| 591 | * |
| 592 | * Since the error status of the file is advanced by this function, |
| 593 | * callers are responsible for checking the return value and handling and/or |
| 594 | * reporting the error. |
| 595 | * |
| 596 | * Return: error status of the address space vs. the file->f_wb_err cursor. |
| 597 | */ |
| 598 | int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte) |
| 599 | { |
| 600 | struct address_space *mapping = file->f_mapping; |
| 601 | |
| 602 | __filemap_fdatawait_range(mapping, start_byte, end_byte); |
| 603 | return file_check_and_advance_wb_err(file); |
| 604 | } |
| 605 | EXPORT_SYMBOL(file_fdatawait_range); |
| 606 | |
| 607 | /** |
| 608 | * filemap_fdatawait_keep_errors - wait for writeback without clearing errors |
| 609 | * @mapping: address space structure to wait for |
| 610 | * |
| 611 | * Walk the list of under-writeback pages of the given address space |
| 612 | * and wait for all of them. Unlike filemap_fdatawait(), this function |
| 613 | * does not clear error status of the address space. |
| 614 | * |
| 615 | * Use this function if callers don't handle errors themselves. Expected |
| 616 | * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
| 617 | * fsfreeze(8) |
| 618 | * |
| 619 | * Return: error status of the address space. |
| 620 | */ |
| 621 | int filemap_fdatawait_keep_errors(struct address_space *mapping) |
| 622 | { |
| 623 | __filemap_fdatawait_range(mapping, 0, LLONG_MAX); |
| 624 | return filemap_check_and_keep_errors(mapping); |
| 625 | } |
| 626 | EXPORT_SYMBOL(filemap_fdatawait_keep_errors); |
| 627 | |
| 628 | /* Returns true if writeback might be needed or already in progress. */ |
| 629 | static bool mapping_needs_writeback(struct address_space *mapping) |
| 630 | { |
| 631 | return mapping->nrpages; |
| 632 | } |
| 633 | |
| 634 | bool filemap_range_has_writeback(struct address_space *mapping, |
| 635 | loff_t start_byte, loff_t end_byte) |
| 636 | { |
| 637 | XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT); |
| 638 | pgoff_t max = end_byte >> PAGE_SHIFT; |
| 639 | struct folio *folio; |
| 640 | |
| 641 | if (end_byte < start_byte) |
| 642 | return false; |
| 643 | |
| 644 | rcu_read_lock(); |
| 645 | xas_for_each(&xas, folio, max) { |
| 646 | if (xas_retry(&xas, folio)) |
| 647 | continue; |
| 648 | if (xa_is_value(folio)) |
| 649 | continue; |
| 650 | if (folio_test_dirty(folio) || folio_test_locked(folio) || |
| 651 | folio_test_writeback(folio)) |
| 652 | break; |
| 653 | } |
| 654 | rcu_read_unlock(); |
| 655 | return folio != NULL; |
| 656 | } |
| 657 | EXPORT_SYMBOL_GPL(filemap_range_has_writeback); |
| 658 | |
| 659 | /** |
| 660 | * filemap_write_and_wait_range - write out & wait on a file range |
| 661 | * @mapping: the address_space for the pages |
| 662 | * @lstart: offset in bytes where the range starts |
| 663 | * @lend: offset in bytes where the range ends (inclusive) |
| 664 | * |
| 665 | * Write out and wait upon file offsets lstart->lend, inclusive. |
| 666 | * |
| 667 | * Note that @lend is inclusive (describes the last byte to be written) so |
| 668 | * that this function can be used to write to the very end-of-file (end = -1). |
| 669 | * |
| 670 | * Return: error status of the address space. |
| 671 | */ |
| 672 | int filemap_write_and_wait_range(struct address_space *mapping, |
| 673 | loff_t lstart, loff_t lend) |
| 674 | { |
| 675 | int err = 0, err2; |
| 676 | |
| 677 | if (lend < lstart) |
| 678 | return 0; |
| 679 | |
| 680 | if (mapping_needs_writeback(mapping)) { |
| 681 | err = __filemap_fdatawrite_range(mapping, lstart, lend, |
| 682 | WB_SYNC_ALL); |
| 683 | /* |
| 684 | * Even if the above returned error, the pages may be |
| 685 | * written partially (e.g. -ENOSPC), so we wait for it. |
| 686 | * But the -EIO is special case, it may indicate the worst |
| 687 | * thing (e.g. bug) happened, so we avoid waiting for it. |
| 688 | */ |
| 689 | if (err != -EIO) |
| 690 | __filemap_fdatawait_range(mapping, lstart, lend); |
| 691 | } |
| 692 | err2 = filemap_check_errors(mapping); |
| 693 | if (!err) |
| 694 | err = err2; |
| 695 | return err; |
| 696 | } |
| 697 | EXPORT_SYMBOL(filemap_write_and_wait_range); |
| 698 | |
| 699 | void __filemap_set_wb_err(struct address_space *mapping, int err) |
| 700 | { |
| 701 | errseq_t eseq = errseq_set(&mapping->wb_err, err); |
| 702 | |
| 703 | trace_filemap_set_wb_err(mapping, eseq); |
| 704 | } |
| 705 | EXPORT_SYMBOL(__filemap_set_wb_err); |
| 706 | |
| 707 | /** |
| 708 | * file_check_and_advance_wb_err - report wb error (if any) that was previously |
| 709 | * and advance wb_err to current one |
| 710 | * @file: struct file on which the error is being reported |
| 711 | * |
| 712 | * When userland calls fsync (or something like nfsd does the equivalent), we |
| 713 | * want to report any writeback errors that occurred since the last fsync (or |
| 714 | * since the file was opened if there haven't been any). |
| 715 | * |
| 716 | * Grab the wb_err from the mapping. If it matches what we have in the file, |
| 717 | * then just quickly return 0. The file is all caught up. |
| 718 | * |
| 719 | * If it doesn't match, then take the mapping value, set the "seen" flag in |
| 720 | * it and try to swap it into place. If it works, or another task beat us |
| 721 | * to it with the new value, then update the f_wb_err and return the error |
| 722 | * portion. The error at this point must be reported via proper channels |
| 723 | * (a'la fsync, or NFS COMMIT operation, etc.). |
| 724 | * |
| 725 | * While we handle mapping->wb_err with atomic operations, the f_wb_err |
| 726 | * value is protected by the f_lock since we must ensure that it reflects |
| 727 | * the latest value swapped in for this file descriptor. |
| 728 | * |
| 729 | * Return: %0 on success, negative error code otherwise. |
| 730 | */ |
| 731 | int file_check_and_advance_wb_err(struct file *file) |
| 732 | { |
| 733 | int err = 0; |
| 734 | errseq_t old = READ_ONCE(file->f_wb_err); |
| 735 | struct address_space *mapping = file->f_mapping; |
| 736 | |
| 737 | /* Locklessly handle the common case where nothing has changed */ |
| 738 | if (errseq_check(&mapping->wb_err, old)) { |
| 739 | /* Something changed, must use slow path */ |
| 740 | spin_lock(&file->f_lock); |
| 741 | old = file->f_wb_err; |
| 742 | err = errseq_check_and_advance(&mapping->wb_err, |
| 743 | &file->f_wb_err); |
| 744 | trace_file_check_and_advance_wb_err(file, old); |
| 745 | spin_unlock(&file->f_lock); |
| 746 | } |
| 747 | |
| 748 | /* |
| 749 | * We're mostly using this function as a drop in replacement for |
| 750 | * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect |
| 751 | * that the legacy code would have had on these flags. |
| 752 | */ |
| 753 | clear_bit(AS_EIO, &mapping->flags); |
| 754 | clear_bit(AS_ENOSPC, &mapping->flags); |
| 755 | return err; |
| 756 | } |
| 757 | EXPORT_SYMBOL(file_check_and_advance_wb_err); |
| 758 | |
| 759 | /** |
| 760 | * file_write_and_wait_range - write out & wait on a file range |
| 761 | * @file: file pointing to address_space with pages |
| 762 | * @lstart: offset in bytes where the range starts |
| 763 | * @lend: offset in bytes where the range ends (inclusive) |
| 764 | * |
| 765 | * Write out and wait upon file offsets lstart->lend, inclusive. |
| 766 | * |
| 767 | * Note that @lend is inclusive (describes the last byte to be written) so |
| 768 | * that this function can be used to write to the very end-of-file (end = -1). |
| 769 | * |
| 770 | * After writing out and waiting on the data, we check and advance the |
| 771 | * f_wb_err cursor to the latest value, and return any errors detected there. |
| 772 | * |
| 773 | * Return: %0 on success, negative error code otherwise. |
| 774 | */ |
| 775 | int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend) |
| 776 | { |
| 777 | int err = 0, err2; |
| 778 | struct address_space *mapping = file->f_mapping; |
| 779 | |
| 780 | if (lend < lstart) |
| 781 | return 0; |
| 782 | |
| 783 | if (mapping_needs_writeback(mapping)) { |
| 784 | err = __filemap_fdatawrite_range(mapping, lstart, lend, |
| 785 | WB_SYNC_ALL); |
| 786 | /* See comment of filemap_write_and_wait() */ |
| 787 | if (err != -EIO) |
| 788 | __filemap_fdatawait_range(mapping, lstart, lend); |
| 789 | } |
| 790 | err2 = file_check_and_advance_wb_err(file); |
| 791 | if (!err) |
| 792 | err = err2; |
| 793 | return err; |
| 794 | } |
| 795 | EXPORT_SYMBOL(file_write_and_wait_range); |
| 796 | |
| 797 | /** |
| 798 | * replace_page_cache_folio - replace a pagecache folio with a new one |
| 799 | * @old: folio to be replaced |
| 800 | * @new: folio to replace with |
| 801 | * |
| 802 | * This function replaces a folio in the pagecache with a new one. On |
| 803 | * success it acquires the pagecache reference for the new folio and |
| 804 | * drops it for the old folio. Both the old and new folios must be |
| 805 | * locked. This function does not add the new folio to the LRU, the |
| 806 | * caller must do that. |
| 807 | * |
| 808 | * The remove + add is atomic. This function cannot fail. |
| 809 | */ |
| 810 | void replace_page_cache_folio(struct folio *old, struct folio *new) |
| 811 | { |
| 812 | struct address_space *mapping = old->mapping; |
| 813 | void (*free_folio)(struct folio *) = mapping->a_ops->free_folio; |
| 814 | pgoff_t offset = old->index; |
| 815 | XA_STATE(xas, &mapping->i_pages, offset); |
| 816 | |
| 817 | VM_BUG_ON_FOLIO(!folio_test_locked(old), old); |
| 818 | VM_BUG_ON_FOLIO(!folio_test_locked(new), new); |
| 819 | VM_BUG_ON_FOLIO(new->mapping, new); |
| 820 | |
| 821 | folio_get(new); |
| 822 | new->mapping = mapping; |
| 823 | new->index = offset; |
| 824 | |
| 825 | mem_cgroup_migrate(old, new); |
| 826 | |
| 827 | xas_lock_irq(&xas); |
| 828 | xas_store(&xas, new); |
| 829 | |
| 830 | old->mapping = NULL; |
| 831 | /* hugetlb pages do not participate in page cache accounting. */ |
| 832 | if (!folio_test_hugetlb(old)) |
| 833 | __lruvec_stat_sub_folio(old, NR_FILE_PAGES); |
| 834 | if (!folio_test_hugetlb(new)) |
| 835 | __lruvec_stat_add_folio(new, NR_FILE_PAGES); |
| 836 | if (folio_test_swapbacked(old)) |
| 837 | __lruvec_stat_sub_folio(old, NR_SHMEM); |
| 838 | if (folio_test_swapbacked(new)) |
| 839 | __lruvec_stat_add_folio(new, NR_SHMEM); |
| 840 | xas_unlock_irq(&xas); |
| 841 | if (free_folio) |
| 842 | free_folio(old); |
| 843 | folio_put(old); |
| 844 | } |
| 845 | EXPORT_SYMBOL_GPL(replace_page_cache_folio); |
| 846 | |
| 847 | noinline int __filemap_add_folio(struct address_space *mapping, |
| 848 | struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp) |
| 849 | { |
| 850 | XA_STATE(xas, &mapping->i_pages, index); |
| 851 | int huge = folio_test_hugetlb(folio); |
| 852 | bool charged = false; |
| 853 | long nr = 1; |
| 854 | |
| 855 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| 856 | VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio); |
| 857 | mapping_set_update(&xas, mapping); |
| 858 | |
| 859 | if (!huge) { |
| 860 | int error = mem_cgroup_charge(folio, NULL, gfp); |
| 861 | VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio); |
| 862 | if (error) |
| 863 | return error; |
| 864 | charged = true; |
| 865 | xas_set_order(&xas, index, folio_order(folio)); |
| 866 | nr = folio_nr_pages(folio); |
| 867 | } |
| 868 | |
| 869 | gfp &= GFP_RECLAIM_MASK; |
| 870 | folio_ref_add(folio, nr); |
| 871 | folio->mapping = mapping; |
| 872 | folio->index = xas.xa_index; |
| 873 | |
| 874 | do { |
| 875 | unsigned int order = xa_get_order(xas.xa, xas.xa_index); |
| 876 | void *entry, *old = NULL; |
| 877 | |
| 878 | if (order > folio_order(folio)) |
| 879 | xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index), |
| 880 | order, gfp); |
| 881 | xas_lock_irq(&xas); |
| 882 | xas_for_each_conflict(&xas, entry) { |
| 883 | old = entry; |
| 884 | if (!xa_is_value(entry)) { |
| 885 | xas_set_err(&xas, -EEXIST); |
| 886 | goto unlock; |
| 887 | } |
| 888 | } |
| 889 | |
| 890 | if (old) { |
| 891 | if (shadowp) |
| 892 | *shadowp = old; |
| 893 | /* entry may have been split before we acquired lock */ |
| 894 | order = xa_get_order(xas.xa, xas.xa_index); |
| 895 | if (order > folio_order(folio)) { |
| 896 | /* How to handle large swap entries? */ |
| 897 | BUG_ON(shmem_mapping(mapping)); |
| 898 | xas_split(&xas, old, order); |
| 899 | xas_reset(&xas); |
| 900 | } |
| 901 | } |
| 902 | |
| 903 | xas_store(&xas, folio); |
| 904 | if (xas_error(&xas)) |
| 905 | goto unlock; |
| 906 | |
| 907 | mapping->nrpages += nr; |
| 908 | |
| 909 | /* hugetlb pages do not participate in page cache accounting */ |
| 910 | if (!huge) { |
| 911 | __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr); |
| 912 | if (folio_test_pmd_mappable(folio)) |
| 913 | __lruvec_stat_mod_folio(folio, |
| 914 | NR_FILE_THPS, nr); |
| 915 | } |
| 916 | unlock: |
| 917 | xas_unlock_irq(&xas); |
| 918 | } while (xas_nomem(&xas, gfp)); |
| 919 | |
| 920 | if (xas_error(&xas)) |
| 921 | goto error; |
| 922 | |
| 923 | trace_mm_filemap_add_to_page_cache(folio); |
| 924 | return 0; |
| 925 | error: |
| 926 | if (charged) |
| 927 | mem_cgroup_uncharge(folio); |
| 928 | folio->mapping = NULL; |
| 929 | /* Leave page->index set: truncation relies upon it */ |
| 930 | folio_put_refs(folio, nr); |
| 931 | return xas_error(&xas); |
| 932 | } |
| 933 | ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO); |
| 934 | |
| 935 | int filemap_add_folio(struct address_space *mapping, struct folio *folio, |
| 936 | pgoff_t index, gfp_t gfp) |
| 937 | { |
| 938 | void *shadow = NULL; |
| 939 | int ret; |
| 940 | |
| 941 | __folio_set_locked(folio); |
| 942 | ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow); |
| 943 | if (unlikely(ret)) |
| 944 | __folio_clear_locked(folio); |
| 945 | else { |
| 946 | /* |
| 947 | * The folio might have been evicted from cache only |
| 948 | * recently, in which case it should be activated like |
| 949 | * any other repeatedly accessed folio. |
| 950 | * The exception is folios getting rewritten; evicting other |
| 951 | * data from the working set, only to cache data that will |
| 952 | * get overwritten with something else, is a waste of memory. |
| 953 | */ |
| 954 | WARN_ON_ONCE(folio_test_active(folio)); |
| 955 | if (!(gfp & __GFP_WRITE) && shadow) |
| 956 | workingset_refault(folio, shadow); |
| 957 | folio_add_lru(folio); |
| 958 | } |
| 959 | return ret; |
| 960 | } |
| 961 | EXPORT_SYMBOL_GPL(filemap_add_folio); |
| 962 | |
| 963 | #ifdef CONFIG_NUMA |
| 964 | struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order) |
| 965 | { |
| 966 | int n; |
| 967 | struct folio *folio; |
| 968 | |
| 969 | if (cpuset_do_page_mem_spread()) { |
| 970 | unsigned int cpuset_mems_cookie; |
| 971 | do { |
| 972 | cpuset_mems_cookie = read_mems_allowed_begin(); |
| 973 | n = cpuset_mem_spread_node(); |
| 974 | folio = __folio_alloc_node(gfp, order, n); |
| 975 | } while (!folio && read_mems_allowed_retry(cpuset_mems_cookie)); |
| 976 | |
| 977 | return folio; |
| 978 | } |
| 979 | return folio_alloc(gfp, order); |
| 980 | } |
| 981 | EXPORT_SYMBOL(filemap_alloc_folio); |
| 982 | #endif |
| 983 | |
| 984 | /* |
| 985 | * filemap_invalidate_lock_two - lock invalidate_lock for two mappings |
| 986 | * |
| 987 | * Lock exclusively invalidate_lock of any passed mapping that is not NULL. |
| 988 | * |
| 989 | * @mapping1: the first mapping to lock |
| 990 | * @mapping2: the second mapping to lock |
| 991 | */ |
| 992 | void filemap_invalidate_lock_two(struct address_space *mapping1, |
| 993 | struct address_space *mapping2) |
| 994 | { |
| 995 | if (mapping1 > mapping2) |
| 996 | swap(mapping1, mapping2); |
| 997 | if (mapping1) |
| 998 | down_write(&mapping1->invalidate_lock); |
| 999 | if (mapping2 && mapping1 != mapping2) |
| 1000 | down_write_nested(&mapping2->invalidate_lock, 1); |
| 1001 | } |
| 1002 | EXPORT_SYMBOL(filemap_invalidate_lock_two); |
| 1003 | |
| 1004 | /* |
| 1005 | * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings |
| 1006 | * |
| 1007 | * Unlock exclusive invalidate_lock of any passed mapping that is not NULL. |
| 1008 | * |
| 1009 | * @mapping1: the first mapping to unlock |
| 1010 | * @mapping2: the second mapping to unlock |
| 1011 | */ |
| 1012 | void filemap_invalidate_unlock_two(struct address_space *mapping1, |
| 1013 | struct address_space *mapping2) |
| 1014 | { |
| 1015 | if (mapping1) |
| 1016 | up_write(&mapping1->invalidate_lock); |
| 1017 | if (mapping2 && mapping1 != mapping2) |
| 1018 | up_write(&mapping2->invalidate_lock); |
| 1019 | } |
| 1020 | EXPORT_SYMBOL(filemap_invalidate_unlock_two); |
| 1021 | |
| 1022 | /* |
| 1023 | * In order to wait for pages to become available there must be |
| 1024 | * waitqueues associated with pages. By using a hash table of |
| 1025 | * waitqueues where the bucket discipline is to maintain all |
| 1026 | * waiters on the same queue and wake all when any of the pages |
| 1027 | * become available, and for the woken contexts to check to be |
| 1028 | * sure the appropriate page became available, this saves space |
| 1029 | * at a cost of "thundering herd" phenomena during rare hash |
| 1030 | * collisions. |
| 1031 | */ |
| 1032 | #define PAGE_WAIT_TABLE_BITS 8 |
| 1033 | #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS) |
| 1034 | static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; |
| 1035 | |
| 1036 | static wait_queue_head_t *folio_waitqueue(struct folio *folio) |
| 1037 | { |
| 1038 | return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)]; |
| 1039 | } |
| 1040 | |
| 1041 | void __init pagecache_init(void) |
| 1042 | { |
| 1043 | int i; |
| 1044 | |
| 1045 | for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) |
| 1046 | init_waitqueue_head(&folio_wait_table[i]); |
| 1047 | |
| 1048 | page_writeback_init(); |
| 1049 | } |
| 1050 | |
| 1051 | /* |
| 1052 | * The page wait code treats the "wait->flags" somewhat unusually, because |
| 1053 | * we have multiple different kinds of waits, not just the usual "exclusive" |
| 1054 | * one. |
| 1055 | * |
| 1056 | * We have: |
| 1057 | * |
| 1058 | * (a) no special bits set: |
| 1059 | * |
| 1060 | * We're just waiting for the bit to be released, and when a waker |
| 1061 | * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up, |
| 1062 | * and remove it from the wait queue. |
| 1063 | * |
| 1064 | * Simple and straightforward. |
| 1065 | * |
| 1066 | * (b) WQ_FLAG_EXCLUSIVE: |
| 1067 | * |
| 1068 | * The waiter is waiting to get the lock, and only one waiter should |
| 1069 | * be woken up to avoid any thundering herd behavior. We'll set the |
| 1070 | * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue. |
| 1071 | * |
| 1072 | * This is the traditional exclusive wait. |
| 1073 | * |
| 1074 | * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM: |
| 1075 | * |
| 1076 | * The waiter is waiting to get the bit, and additionally wants the |
| 1077 | * lock to be transferred to it for fair lock behavior. If the lock |
| 1078 | * cannot be taken, we stop walking the wait queue without waking |
| 1079 | * the waiter. |
| 1080 | * |
| 1081 | * This is the "fair lock handoff" case, and in addition to setting |
| 1082 | * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see |
| 1083 | * that it now has the lock. |
| 1084 | */ |
| 1085 | static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg) |
| 1086 | { |
| 1087 | unsigned int flags; |
| 1088 | struct wait_page_key *key = arg; |
| 1089 | struct wait_page_queue *wait_page |
| 1090 | = container_of(wait, struct wait_page_queue, wait); |
| 1091 | |
| 1092 | if (!wake_page_match(wait_page, key)) |
| 1093 | return 0; |
| 1094 | |
| 1095 | /* |
| 1096 | * If it's a lock handoff wait, we get the bit for it, and |
| 1097 | * stop walking (and do not wake it up) if we can't. |
| 1098 | */ |
| 1099 | flags = wait->flags; |
| 1100 | if (flags & WQ_FLAG_EXCLUSIVE) { |
| 1101 | if (test_bit(key->bit_nr, &key->folio->flags)) |
| 1102 | return -1; |
| 1103 | if (flags & WQ_FLAG_CUSTOM) { |
| 1104 | if (test_and_set_bit(key->bit_nr, &key->folio->flags)) |
| 1105 | return -1; |
| 1106 | flags |= WQ_FLAG_DONE; |
| 1107 | } |
| 1108 | } |
| 1109 | |
| 1110 | /* |
| 1111 | * We are holding the wait-queue lock, but the waiter that |
| 1112 | * is waiting for this will be checking the flags without |
| 1113 | * any locking. |
| 1114 | * |
| 1115 | * So update the flags atomically, and wake up the waiter |
| 1116 | * afterwards to avoid any races. This store-release pairs |
| 1117 | * with the load-acquire in folio_wait_bit_common(). |
| 1118 | */ |
| 1119 | smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN); |
| 1120 | wake_up_state(wait->private, mode); |
| 1121 | |
| 1122 | /* |
| 1123 | * Ok, we have successfully done what we're waiting for, |
| 1124 | * and we can unconditionally remove the wait entry. |
| 1125 | * |
| 1126 | * Note that this pairs with the "finish_wait()" in the |
| 1127 | * waiter, and has to be the absolute last thing we do. |
| 1128 | * After this list_del_init(&wait->entry) the wait entry |
| 1129 | * might be de-allocated and the process might even have |
| 1130 | * exited. |
| 1131 | */ |
| 1132 | list_del_init_careful(&wait->entry); |
| 1133 | return (flags & WQ_FLAG_EXCLUSIVE) != 0; |
| 1134 | } |
| 1135 | |
| 1136 | static void folio_wake_bit(struct folio *folio, int bit_nr) |
| 1137 | { |
| 1138 | wait_queue_head_t *q = folio_waitqueue(folio); |
| 1139 | struct wait_page_key key; |
| 1140 | unsigned long flags; |
| 1141 | wait_queue_entry_t bookmark; |
| 1142 | |
| 1143 | key.folio = folio; |
| 1144 | key.bit_nr = bit_nr; |
| 1145 | key.page_match = 0; |
| 1146 | |
| 1147 | bookmark.flags = 0; |
| 1148 | bookmark.private = NULL; |
| 1149 | bookmark.func = NULL; |
| 1150 | INIT_LIST_HEAD(&bookmark.entry); |
| 1151 | |
| 1152 | spin_lock_irqsave(&q->lock, flags); |
| 1153 | __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
| 1154 | |
| 1155 | while (bookmark.flags & WQ_FLAG_BOOKMARK) { |
| 1156 | /* |
| 1157 | * Take a breather from holding the lock, |
| 1158 | * allow pages that finish wake up asynchronously |
| 1159 | * to acquire the lock and remove themselves |
| 1160 | * from wait queue |
| 1161 | */ |
| 1162 | spin_unlock_irqrestore(&q->lock, flags); |
| 1163 | cpu_relax(); |
| 1164 | spin_lock_irqsave(&q->lock, flags); |
| 1165 | __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
| 1166 | } |
| 1167 | |
| 1168 | /* |
| 1169 | * It's possible to miss clearing waiters here, when we woke our page |
| 1170 | * waiters, but the hashed waitqueue has waiters for other pages on it. |
| 1171 | * That's okay, it's a rare case. The next waker will clear it. |
| 1172 | * |
| 1173 | * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE, |
| 1174 | * other), the flag may be cleared in the course of freeing the page; |
| 1175 | * but that is not required for correctness. |
| 1176 | */ |
| 1177 | if (!waitqueue_active(q) || !key.page_match) |
| 1178 | folio_clear_waiters(folio); |
| 1179 | |
| 1180 | spin_unlock_irqrestore(&q->lock, flags); |
| 1181 | } |
| 1182 | |
| 1183 | static void folio_wake(struct folio *folio, int bit) |
| 1184 | { |
| 1185 | if (!folio_test_waiters(folio)) |
| 1186 | return; |
| 1187 | folio_wake_bit(folio, bit); |
| 1188 | } |
| 1189 | |
| 1190 | /* |
| 1191 | * A choice of three behaviors for folio_wait_bit_common(): |
| 1192 | */ |
| 1193 | enum behavior { |
| 1194 | EXCLUSIVE, /* Hold ref to page and take the bit when woken, like |
| 1195 | * __folio_lock() waiting on then setting PG_locked. |
| 1196 | */ |
| 1197 | SHARED, /* Hold ref to page and check the bit when woken, like |
| 1198 | * folio_wait_writeback() waiting on PG_writeback. |
| 1199 | */ |
| 1200 | DROP, /* Drop ref to page before wait, no check when woken, |
| 1201 | * like folio_put_wait_locked() on PG_locked. |
| 1202 | */ |
| 1203 | }; |
| 1204 | |
| 1205 | /* |
| 1206 | * Attempt to check (or get) the folio flag, and mark us done |
| 1207 | * if successful. |
| 1208 | */ |
| 1209 | static inline bool folio_trylock_flag(struct folio *folio, int bit_nr, |
| 1210 | struct wait_queue_entry *wait) |
| 1211 | { |
| 1212 | if (wait->flags & WQ_FLAG_EXCLUSIVE) { |
| 1213 | if (test_and_set_bit(bit_nr, &folio->flags)) |
| 1214 | return false; |
| 1215 | } else if (test_bit(bit_nr, &folio->flags)) |
| 1216 | return false; |
| 1217 | |
| 1218 | wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE; |
| 1219 | return true; |
| 1220 | } |
| 1221 | |
| 1222 | /* How many times do we accept lock stealing from under a waiter? */ |
| 1223 | int sysctl_page_lock_unfairness = 5; |
| 1224 | |
| 1225 | static inline int folio_wait_bit_common(struct folio *folio, int bit_nr, |
| 1226 | int state, enum behavior behavior) |
| 1227 | { |
| 1228 | wait_queue_head_t *q = folio_waitqueue(folio); |
| 1229 | int unfairness = sysctl_page_lock_unfairness; |
| 1230 | struct wait_page_queue wait_page; |
| 1231 | wait_queue_entry_t *wait = &wait_page.wait; |
| 1232 | bool thrashing = false; |
| 1233 | unsigned long pflags; |
| 1234 | bool in_thrashing; |
| 1235 | |
| 1236 | if (bit_nr == PG_locked && |
| 1237 | !folio_test_uptodate(folio) && folio_test_workingset(folio)) { |
| 1238 | delayacct_thrashing_start(&in_thrashing); |
| 1239 | psi_memstall_enter(&pflags); |
| 1240 | thrashing = true; |
| 1241 | } |
| 1242 | |
| 1243 | init_wait(wait); |
| 1244 | wait->func = wake_page_function; |
| 1245 | wait_page.folio = folio; |
| 1246 | wait_page.bit_nr = bit_nr; |
| 1247 | |
| 1248 | repeat: |
| 1249 | wait->flags = 0; |
| 1250 | if (behavior == EXCLUSIVE) { |
| 1251 | wait->flags = WQ_FLAG_EXCLUSIVE; |
| 1252 | if (--unfairness < 0) |
| 1253 | wait->flags |= WQ_FLAG_CUSTOM; |
| 1254 | } |
| 1255 | |
| 1256 | /* |
| 1257 | * Do one last check whether we can get the |
| 1258 | * page bit synchronously. |
| 1259 | * |
| 1260 | * Do the folio_set_waiters() marking before that |
| 1261 | * to let any waker we _just_ missed know they |
| 1262 | * need to wake us up (otherwise they'll never |
| 1263 | * even go to the slow case that looks at the |
| 1264 | * page queue), and add ourselves to the wait |
| 1265 | * queue if we need to sleep. |
| 1266 | * |
| 1267 | * This part needs to be done under the queue |
| 1268 | * lock to avoid races. |
| 1269 | */ |
| 1270 | spin_lock_irq(&q->lock); |
| 1271 | folio_set_waiters(folio); |
| 1272 | if (!folio_trylock_flag(folio, bit_nr, wait)) |
| 1273 | __add_wait_queue_entry_tail(q, wait); |
| 1274 | spin_unlock_irq(&q->lock); |
| 1275 | |
| 1276 | /* |
| 1277 | * From now on, all the logic will be based on |
| 1278 | * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to |
| 1279 | * see whether the page bit testing has already |
| 1280 | * been done by the wake function. |
| 1281 | * |
| 1282 | * We can drop our reference to the folio. |
| 1283 | */ |
| 1284 | if (behavior == DROP) |
| 1285 | folio_put(folio); |
| 1286 | |
| 1287 | /* |
| 1288 | * Note that until the "finish_wait()", or until |
| 1289 | * we see the WQ_FLAG_WOKEN flag, we need to |
| 1290 | * be very careful with the 'wait->flags', because |
| 1291 | * we may race with a waker that sets them. |
| 1292 | */ |
| 1293 | for (;;) { |
| 1294 | unsigned int flags; |
| 1295 | |
| 1296 | set_current_state(state); |
| 1297 | |
| 1298 | /* Loop until we've been woken or interrupted */ |
| 1299 | flags = smp_load_acquire(&wait->flags); |
| 1300 | if (!(flags & WQ_FLAG_WOKEN)) { |
| 1301 | if (signal_pending_state(state, current)) |
| 1302 | break; |
| 1303 | |
| 1304 | io_schedule(); |
| 1305 | continue; |
| 1306 | } |
| 1307 | |
| 1308 | /* If we were non-exclusive, we're done */ |
| 1309 | if (behavior != EXCLUSIVE) |
| 1310 | break; |
| 1311 | |
| 1312 | /* If the waker got the lock for us, we're done */ |
| 1313 | if (flags & WQ_FLAG_DONE) |
| 1314 | break; |
| 1315 | |
| 1316 | /* |
| 1317 | * Otherwise, if we're getting the lock, we need to |
| 1318 | * try to get it ourselves. |
| 1319 | * |
| 1320 | * And if that fails, we'll have to retry this all. |
| 1321 | */ |
| 1322 | if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0)))) |
| 1323 | goto repeat; |
| 1324 | |
| 1325 | wait->flags |= WQ_FLAG_DONE; |
| 1326 | break; |
| 1327 | } |
| 1328 | |
| 1329 | /* |
| 1330 | * If a signal happened, this 'finish_wait()' may remove the last |
| 1331 | * waiter from the wait-queues, but the folio waiters bit will remain |
| 1332 | * set. That's ok. The next wakeup will take care of it, and trying |
| 1333 | * to do it here would be difficult and prone to races. |
| 1334 | */ |
| 1335 | finish_wait(q, wait); |
| 1336 | |
| 1337 | if (thrashing) { |
| 1338 | delayacct_thrashing_end(&in_thrashing); |
| 1339 | psi_memstall_leave(&pflags); |
| 1340 | } |
| 1341 | |
| 1342 | /* |
| 1343 | * NOTE! The wait->flags weren't stable until we've done the |
| 1344 | * 'finish_wait()', and we could have exited the loop above due |
| 1345 | * to a signal, and had a wakeup event happen after the signal |
| 1346 | * test but before the 'finish_wait()'. |
| 1347 | * |
| 1348 | * So only after the finish_wait() can we reliably determine |
| 1349 | * if we got woken up or not, so we can now figure out the final |
| 1350 | * return value based on that state without races. |
| 1351 | * |
| 1352 | * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive |
| 1353 | * waiter, but an exclusive one requires WQ_FLAG_DONE. |
| 1354 | */ |
| 1355 | if (behavior == EXCLUSIVE) |
| 1356 | return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR; |
| 1357 | |
| 1358 | return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR; |
| 1359 | } |
| 1360 | |
| 1361 | #ifdef CONFIG_MIGRATION |
| 1362 | /** |
| 1363 | * migration_entry_wait_on_locked - Wait for a migration entry to be removed |
| 1364 | * @entry: migration swap entry. |
| 1365 | * @ptl: already locked ptl. This function will drop the lock. |
| 1366 | * |
| 1367 | * Wait for a migration entry referencing the given page to be removed. This is |
| 1368 | * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except |
| 1369 | * this can be called without taking a reference on the page. Instead this |
| 1370 | * should be called while holding the ptl for the migration entry referencing |
| 1371 | * the page. |
| 1372 | * |
| 1373 | * Returns after unlocking the ptl. |
| 1374 | * |
| 1375 | * This follows the same logic as folio_wait_bit_common() so see the comments |
| 1376 | * there. |
| 1377 | */ |
| 1378 | void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl) |
| 1379 | __releases(ptl) |
| 1380 | { |
| 1381 | struct wait_page_queue wait_page; |
| 1382 | wait_queue_entry_t *wait = &wait_page.wait; |
| 1383 | bool thrashing = false; |
| 1384 | unsigned long pflags; |
| 1385 | bool in_thrashing; |
| 1386 | wait_queue_head_t *q; |
| 1387 | struct folio *folio = page_folio(pfn_swap_entry_to_page(entry)); |
| 1388 | |
| 1389 | q = folio_waitqueue(folio); |
| 1390 | if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) { |
| 1391 | delayacct_thrashing_start(&in_thrashing); |
| 1392 | psi_memstall_enter(&pflags); |
| 1393 | thrashing = true; |
| 1394 | } |
| 1395 | |
| 1396 | init_wait(wait); |
| 1397 | wait->func = wake_page_function; |
| 1398 | wait_page.folio = folio; |
| 1399 | wait_page.bit_nr = PG_locked; |
| 1400 | wait->flags = 0; |
| 1401 | |
| 1402 | spin_lock_irq(&q->lock); |
| 1403 | folio_set_waiters(folio); |
| 1404 | if (!folio_trylock_flag(folio, PG_locked, wait)) |
| 1405 | __add_wait_queue_entry_tail(q, wait); |
| 1406 | spin_unlock_irq(&q->lock); |
| 1407 | |
| 1408 | /* |
| 1409 | * If a migration entry exists for the page the migration path must hold |
| 1410 | * a valid reference to the page, and it must take the ptl to remove the |
| 1411 | * migration entry. So the page is valid until the ptl is dropped. |
| 1412 | */ |
| 1413 | spin_unlock(ptl); |
| 1414 | |
| 1415 | for (;;) { |
| 1416 | unsigned int flags; |
| 1417 | |
| 1418 | set_current_state(TASK_UNINTERRUPTIBLE); |
| 1419 | |
| 1420 | /* Loop until we've been woken or interrupted */ |
| 1421 | flags = smp_load_acquire(&wait->flags); |
| 1422 | if (!(flags & WQ_FLAG_WOKEN)) { |
| 1423 | if (signal_pending_state(TASK_UNINTERRUPTIBLE, current)) |
| 1424 | break; |
| 1425 | |
| 1426 | io_schedule(); |
| 1427 | continue; |
| 1428 | } |
| 1429 | break; |
| 1430 | } |
| 1431 | |
| 1432 | finish_wait(q, wait); |
| 1433 | |
| 1434 | if (thrashing) { |
| 1435 | delayacct_thrashing_end(&in_thrashing); |
| 1436 | psi_memstall_leave(&pflags); |
| 1437 | } |
| 1438 | } |
| 1439 | #endif |
| 1440 | |
| 1441 | void folio_wait_bit(struct folio *folio, int bit_nr) |
| 1442 | { |
| 1443 | folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED); |
| 1444 | } |
| 1445 | EXPORT_SYMBOL(folio_wait_bit); |
| 1446 | |
| 1447 | int folio_wait_bit_killable(struct folio *folio, int bit_nr) |
| 1448 | { |
| 1449 | return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED); |
| 1450 | } |
| 1451 | EXPORT_SYMBOL(folio_wait_bit_killable); |
| 1452 | |
| 1453 | /** |
| 1454 | * folio_put_wait_locked - Drop a reference and wait for it to be unlocked |
| 1455 | * @folio: The folio to wait for. |
| 1456 | * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc). |
| 1457 | * |
| 1458 | * The caller should hold a reference on @folio. They expect the page to |
| 1459 | * become unlocked relatively soon, but do not wish to hold up migration |
| 1460 | * (for example) by holding the reference while waiting for the folio to |
| 1461 | * come unlocked. After this function returns, the caller should not |
| 1462 | * dereference @folio. |
| 1463 | * |
| 1464 | * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal. |
| 1465 | */ |
| 1466 | static int folio_put_wait_locked(struct folio *folio, int state) |
| 1467 | { |
| 1468 | return folio_wait_bit_common(folio, PG_locked, state, DROP); |
| 1469 | } |
| 1470 | |
| 1471 | /** |
| 1472 | * folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue |
| 1473 | * @folio: Folio defining the wait queue of interest |
| 1474 | * @waiter: Waiter to add to the queue |
| 1475 | * |
| 1476 | * Add an arbitrary @waiter to the wait queue for the nominated @folio. |
| 1477 | */ |
| 1478 | void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter) |
| 1479 | { |
| 1480 | wait_queue_head_t *q = folio_waitqueue(folio); |
| 1481 | unsigned long flags; |
| 1482 | |
| 1483 | spin_lock_irqsave(&q->lock, flags); |
| 1484 | __add_wait_queue_entry_tail(q, waiter); |
| 1485 | folio_set_waiters(folio); |
| 1486 | spin_unlock_irqrestore(&q->lock, flags); |
| 1487 | } |
| 1488 | EXPORT_SYMBOL_GPL(folio_add_wait_queue); |
| 1489 | |
| 1490 | #ifndef clear_bit_unlock_is_negative_byte |
| 1491 | |
| 1492 | /* |
| 1493 | * PG_waiters is the high bit in the same byte as PG_lock. |
| 1494 | * |
| 1495 | * On x86 (and on many other architectures), we can clear PG_lock and |
| 1496 | * test the sign bit at the same time. But if the architecture does |
| 1497 | * not support that special operation, we just do this all by hand |
| 1498 | * instead. |
| 1499 | * |
| 1500 | * The read of PG_waiters has to be after (or concurrently with) PG_locked |
| 1501 | * being cleared, but a memory barrier should be unnecessary since it is |
| 1502 | * in the same byte as PG_locked. |
| 1503 | */ |
| 1504 | static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem) |
| 1505 | { |
| 1506 | clear_bit_unlock(nr, mem); |
| 1507 | /* smp_mb__after_atomic(); */ |
| 1508 | return test_bit(PG_waiters, mem); |
| 1509 | } |
| 1510 | |
| 1511 | #endif |
| 1512 | |
| 1513 | /** |
| 1514 | * folio_unlock - Unlock a locked folio. |
| 1515 | * @folio: The folio. |
| 1516 | * |
| 1517 | * Unlocks the folio and wakes up any thread sleeping on the page lock. |
| 1518 | * |
| 1519 | * Context: May be called from interrupt or process context. May not be |
| 1520 | * called from NMI context. |
| 1521 | */ |
| 1522 | void folio_unlock(struct folio *folio) |
| 1523 | { |
| 1524 | /* Bit 7 allows x86 to check the byte's sign bit */ |
| 1525 | BUILD_BUG_ON(PG_waiters != 7); |
| 1526 | BUILD_BUG_ON(PG_locked > 7); |
| 1527 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| 1528 | if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0))) |
| 1529 | folio_wake_bit(folio, PG_locked); |
| 1530 | } |
| 1531 | EXPORT_SYMBOL(folio_unlock); |
| 1532 | |
| 1533 | /** |
| 1534 | * folio_end_private_2 - Clear PG_private_2 and wake any waiters. |
| 1535 | * @folio: The folio. |
| 1536 | * |
| 1537 | * Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for |
| 1538 | * it. The folio reference held for PG_private_2 being set is released. |
| 1539 | * |
| 1540 | * This is, for example, used when a netfs folio is being written to a local |
| 1541 | * disk cache, thereby allowing writes to the cache for the same folio to be |
| 1542 | * serialised. |
| 1543 | */ |
| 1544 | void folio_end_private_2(struct folio *folio) |
| 1545 | { |
| 1546 | VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio); |
| 1547 | clear_bit_unlock(PG_private_2, folio_flags(folio, 0)); |
| 1548 | folio_wake_bit(folio, PG_private_2); |
| 1549 | folio_put(folio); |
| 1550 | } |
| 1551 | EXPORT_SYMBOL(folio_end_private_2); |
| 1552 | |
| 1553 | /** |
| 1554 | * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio. |
| 1555 | * @folio: The folio to wait on. |
| 1556 | * |
| 1557 | * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio. |
| 1558 | */ |
| 1559 | void folio_wait_private_2(struct folio *folio) |
| 1560 | { |
| 1561 | while (folio_test_private_2(folio)) |
| 1562 | folio_wait_bit(folio, PG_private_2); |
| 1563 | } |
| 1564 | EXPORT_SYMBOL(folio_wait_private_2); |
| 1565 | |
| 1566 | /** |
| 1567 | * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio. |
| 1568 | * @folio: The folio to wait on. |
| 1569 | * |
| 1570 | * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a |
| 1571 | * fatal signal is received by the calling task. |
| 1572 | * |
| 1573 | * Return: |
| 1574 | * - 0 if successful. |
| 1575 | * - -EINTR if a fatal signal was encountered. |
| 1576 | */ |
| 1577 | int folio_wait_private_2_killable(struct folio *folio) |
| 1578 | { |
| 1579 | int ret = 0; |
| 1580 | |
| 1581 | while (folio_test_private_2(folio)) { |
| 1582 | ret = folio_wait_bit_killable(folio, PG_private_2); |
| 1583 | if (ret < 0) |
| 1584 | break; |
| 1585 | } |
| 1586 | |
| 1587 | return ret; |
| 1588 | } |
| 1589 | EXPORT_SYMBOL(folio_wait_private_2_killable); |
| 1590 | |
| 1591 | /** |
| 1592 | * folio_end_writeback - End writeback against a folio. |
| 1593 | * @folio: The folio. |
| 1594 | */ |
| 1595 | void folio_end_writeback(struct folio *folio) |
| 1596 | { |
| 1597 | /* |
| 1598 | * folio_test_clear_reclaim() could be used here but it is an |
| 1599 | * atomic operation and overkill in this particular case. Failing |
| 1600 | * to shuffle a folio marked for immediate reclaim is too mild |
| 1601 | * a gain to justify taking an atomic operation penalty at the |
| 1602 | * end of every folio writeback. |
| 1603 | */ |
| 1604 | if (folio_test_reclaim(folio)) { |
| 1605 | folio_clear_reclaim(folio); |
| 1606 | folio_rotate_reclaimable(folio); |
| 1607 | } |
| 1608 | |
| 1609 | /* |
| 1610 | * Writeback does not hold a folio reference of its own, relying |
| 1611 | * on truncation to wait for the clearing of PG_writeback. |
| 1612 | * But here we must make sure that the folio is not freed and |
| 1613 | * reused before the folio_wake(). |
| 1614 | */ |
| 1615 | folio_get(folio); |
| 1616 | if (!__folio_end_writeback(folio)) |
| 1617 | BUG(); |
| 1618 | |
| 1619 | smp_mb__after_atomic(); |
| 1620 | folio_wake(folio, PG_writeback); |
| 1621 | acct_reclaim_writeback(folio); |
| 1622 | folio_put(folio); |
| 1623 | } |
| 1624 | EXPORT_SYMBOL(folio_end_writeback); |
| 1625 | |
| 1626 | /** |
| 1627 | * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it. |
| 1628 | * @folio: The folio to lock |
| 1629 | */ |
| 1630 | void __folio_lock(struct folio *folio) |
| 1631 | { |
| 1632 | folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE, |
| 1633 | EXCLUSIVE); |
| 1634 | } |
| 1635 | EXPORT_SYMBOL(__folio_lock); |
| 1636 | |
| 1637 | int __folio_lock_killable(struct folio *folio) |
| 1638 | { |
| 1639 | return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE, |
| 1640 | EXCLUSIVE); |
| 1641 | } |
| 1642 | EXPORT_SYMBOL_GPL(__folio_lock_killable); |
| 1643 | |
| 1644 | static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait) |
| 1645 | { |
| 1646 | struct wait_queue_head *q = folio_waitqueue(folio); |
| 1647 | int ret = 0; |
| 1648 | |
| 1649 | wait->folio = folio; |
| 1650 | wait->bit_nr = PG_locked; |
| 1651 | |
| 1652 | spin_lock_irq(&q->lock); |
| 1653 | __add_wait_queue_entry_tail(q, &wait->wait); |
| 1654 | folio_set_waiters(folio); |
| 1655 | ret = !folio_trylock(folio); |
| 1656 | /* |
| 1657 | * If we were successful now, we know we're still on the |
| 1658 | * waitqueue as we're still under the lock. This means it's |
| 1659 | * safe to remove and return success, we know the callback |
| 1660 | * isn't going to trigger. |
| 1661 | */ |
| 1662 | if (!ret) |
| 1663 | __remove_wait_queue(q, &wait->wait); |
| 1664 | else |
| 1665 | ret = -EIOCBQUEUED; |
| 1666 | spin_unlock_irq(&q->lock); |
| 1667 | return ret; |
| 1668 | } |
| 1669 | |
| 1670 | /* |
| 1671 | * Return values: |
| 1672 | * true - folio is locked; mmap_lock is still held. |
| 1673 | * false - folio is not locked. |
| 1674 | * mmap_lock has been released (mmap_read_unlock(), unless flags had both |
| 1675 | * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in |
| 1676 | * which case mmap_lock is still held. |
| 1677 | * |
| 1678 | * If neither ALLOW_RETRY nor KILLABLE are set, will always return true |
| 1679 | * with the folio locked and the mmap_lock unperturbed. |
| 1680 | */ |
| 1681 | bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm, |
| 1682 | unsigned int flags) |
| 1683 | { |
| 1684 | if (fault_flag_allow_retry_first(flags)) { |
| 1685 | /* |
| 1686 | * CAUTION! In this case, mmap_lock is not released |
| 1687 | * even though return 0. |
| 1688 | */ |
| 1689 | if (flags & FAULT_FLAG_RETRY_NOWAIT) |
| 1690 | return false; |
| 1691 | |
| 1692 | mmap_read_unlock(mm); |
| 1693 | if (flags & FAULT_FLAG_KILLABLE) |
| 1694 | folio_wait_locked_killable(folio); |
| 1695 | else |
| 1696 | folio_wait_locked(folio); |
| 1697 | return false; |
| 1698 | } |
| 1699 | if (flags & FAULT_FLAG_KILLABLE) { |
| 1700 | bool ret; |
| 1701 | |
| 1702 | ret = __folio_lock_killable(folio); |
| 1703 | if (ret) { |
| 1704 | mmap_read_unlock(mm); |
| 1705 | return false; |
| 1706 | } |
| 1707 | } else { |
| 1708 | __folio_lock(folio); |
| 1709 | } |
| 1710 | |
| 1711 | return true; |
| 1712 | } |
| 1713 | |
| 1714 | /** |
| 1715 | * page_cache_next_miss() - Find the next gap in the page cache. |
| 1716 | * @mapping: Mapping. |
| 1717 | * @index: Index. |
| 1718 | * @max_scan: Maximum range to search. |
| 1719 | * |
| 1720 | * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the |
| 1721 | * gap with the lowest index. |
| 1722 | * |
| 1723 | * This function may be called under the rcu_read_lock. However, this will |
| 1724 | * not atomically search a snapshot of the cache at a single point in time. |
| 1725 | * For example, if a gap is created at index 5, then subsequently a gap is |
| 1726 | * created at index 10, page_cache_next_miss covering both indices may |
| 1727 | * return 10 if called under the rcu_read_lock. |
| 1728 | * |
| 1729 | * Return: The index of the gap if found, otherwise an index outside the |
| 1730 | * range specified (in which case 'return - index >= max_scan' will be true). |
| 1731 | * In the rare case of index wrap-around, 0 will be returned. |
| 1732 | */ |
| 1733 | pgoff_t page_cache_next_miss(struct address_space *mapping, |
| 1734 | pgoff_t index, unsigned long max_scan) |
| 1735 | { |
| 1736 | XA_STATE(xas, &mapping->i_pages, index); |
| 1737 | |
| 1738 | while (max_scan--) { |
| 1739 | void *entry = xas_next(&xas); |
| 1740 | if (!entry || xa_is_value(entry)) |
| 1741 | break; |
| 1742 | if (xas.xa_index == 0) |
| 1743 | break; |
| 1744 | } |
| 1745 | |
| 1746 | return xas.xa_index; |
| 1747 | } |
| 1748 | EXPORT_SYMBOL(page_cache_next_miss); |
| 1749 | |
| 1750 | /** |
| 1751 | * page_cache_prev_miss() - Find the previous gap in the page cache. |
| 1752 | * @mapping: Mapping. |
| 1753 | * @index: Index. |
| 1754 | * @max_scan: Maximum range to search. |
| 1755 | * |
| 1756 | * Search the range [max(index - max_scan + 1, 0), index] for the |
| 1757 | * gap with the highest index. |
| 1758 | * |
| 1759 | * This function may be called under the rcu_read_lock. However, this will |
| 1760 | * not atomically search a snapshot of the cache at a single point in time. |
| 1761 | * For example, if a gap is created at index 10, then subsequently a gap is |
| 1762 | * created at index 5, page_cache_prev_miss() covering both indices may |
| 1763 | * return 5 if called under the rcu_read_lock. |
| 1764 | * |
| 1765 | * Return: The index of the gap if found, otherwise an index outside the |
| 1766 | * range specified (in which case 'index - return >= max_scan' will be true). |
| 1767 | * In the rare case of wrap-around, ULONG_MAX will be returned. |
| 1768 | */ |
| 1769 | pgoff_t page_cache_prev_miss(struct address_space *mapping, |
| 1770 | pgoff_t index, unsigned long max_scan) |
| 1771 | { |
| 1772 | XA_STATE(xas, &mapping->i_pages, index); |
| 1773 | |
| 1774 | while (max_scan--) { |
| 1775 | void *entry = xas_prev(&xas); |
| 1776 | if (!entry || xa_is_value(entry)) |
| 1777 | break; |
| 1778 | if (xas.xa_index == ULONG_MAX) |
| 1779 | break; |
| 1780 | } |
| 1781 | |
| 1782 | return xas.xa_index; |
| 1783 | } |
| 1784 | EXPORT_SYMBOL(page_cache_prev_miss); |
| 1785 | |
| 1786 | /* |
| 1787 | * Lockless page cache protocol: |
| 1788 | * On the lookup side: |
| 1789 | * 1. Load the folio from i_pages |
| 1790 | * 2. Increment the refcount if it's not zero |
| 1791 | * 3. If the folio is not found by xas_reload(), put the refcount and retry |
| 1792 | * |
| 1793 | * On the removal side: |
| 1794 | * A. Freeze the page (by zeroing the refcount if nobody else has a reference) |
| 1795 | * B. Remove the page from i_pages |
| 1796 | * C. Return the page to the page allocator |
| 1797 | * |
| 1798 | * This means that any page may have its reference count temporarily |
| 1799 | * increased by a speculative page cache (or fast GUP) lookup as it can |
| 1800 | * be allocated by another user before the RCU grace period expires. |
| 1801 | * Because the refcount temporarily acquired here may end up being the |
| 1802 | * last refcount on the page, any page allocation must be freeable by |
| 1803 | * folio_put(). |
| 1804 | */ |
| 1805 | |
| 1806 | /* |
| 1807 | * filemap_get_entry - Get a page cache entry. |
| 1808 | * @mapping: the address_space to search |
| 1809 | * @index: The page cache index. |
| 1810 | * |
| 1811 | * Looks up the page cache entry at @mapping & @index. If it is a folio, |
| 1812 | * it is returned with an increased refcount. If it is a shadow entry |
| 1813 | * of a previously evicted folio, or a swap entry from shmem/tmpfs, |
| 1814 | * it is returned without further action. |
| 1815 | * |
| 1816 | * Return: The folio, swap or shadow entry, %NULL if nothing is found. |
| 1817 | */ |
| 1818 | void *filemap_get_entry(struct address_space *mapping, pgoff_t index) |
| 1819 | { |
| 1820 | XA_STATE(xas, &mapping->i_pages, index); |
| 1821 | struct folio *folio; |
| 1822 | |
| 1823 | rcu_read_lock(); |
| 1824 | repeat: |
| 1825 | xas_reset(&xas); |
| 1826 | folio = xas_load(&xas); |
| 1827 | if (xas_retry(&xas, folio)) |
| 1828 | goto repeat; |
| 1829 | /* |
| 1830 | * A shadow entry of a recently evicted page, or a swap entry from |
| 1831 | * shmem/tmpfs. Return it without attempting to raise page count. |
| 1832 | */ |
| 1833 | if (!folio || xa_is_value(folio)) |
| 1834 | goto out; |
| 1835 | |
| 1836 | if (!folio_try_get_rcu(folio)) |
| 1837 | goto repeat; |
| 1838 | |
| 1839 | if (unlikely(folio != xas_reload(&xas))) { |
| 1840 | folio_put(folio); |
| 1841 | goto repeat; |
| 1842 | } |
| 1843 | out: |
| 1844 | rcu_read_unlock(); |
| 1845 | |
| 1846 | return folio; |
| 1847 | } |
| 1848 | |
| 1849 | /** |
| 1850 | * __filemap_get_folio - Find and get a reference to a folio. |
| 1851 | * @mapping: The address_space to search. |
| 1852 | * @index: The page index. |
| 1853 | * @fgp_flags: %FGP flags modify how the folio is returned. |
| 1854 | * @gfp: Memory allocation flags to use if %FGP_CREAT is specified. |
| 1855 | * |
| 1856 | * Looks up the page cache entry at @mapping & @index. |
| 1857 | * |
| 1858 | * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even |
| 1859 | * if the %GFP flags specified for %FGP_CREAT are atomic. |
| 1860 | * |
| 1861 | * If this function returns a folio, it is returned with an increased refcount. |
| 1862 | * |
| 1863 | * Return: The found folio or an ERR_PTR() otherwise. |
| 1864 | */ |
| 1865 | struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index, |
| 1866 | fgf_t fgp_flags, gfp_t gfp) |
| 1867 | { |
| 1868 | struct folio *folio; |
| 1869 | |
| 1870 | repeat: |
| 1871 | folio = filemap_get_entry(mapping, index); |
| 1872 | if (xa_is_value(folio)) |
| 1873 | folio = NULL; |
| 1874 | if (!folio) |
| 1875 | goto no_page; |
| 1876 | |
| 1877 | if (fgp_flags & FGP_LOCK) { |
| 1878 | if (fgp_flags & FGP_NOWAIT) { |
| 1879 | if (!folio_trylock(folio)) { |
| 1880 | folio_put(folio); |
| 1881 | return ERR_PTR(-EAGAIN); |
| 1882 | } |
| 1883 | } else { |
| 1884 | folio_lock(folio); |
| 1885 | } |
| 1886 | |
| 1887 | /* Has the page been truncated? */ |
| 1888 | if (unlikely(folio->mapping != mapping)) { |
| 1889 | folio_unlock(folio); |
| 1890 | folio_put(folio); |
| 1891 | goto repeat; |
| 1892 | } |
| 1893 | VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); |
| 1894 | } |
| 1895 | |
| 1896 | if (fgp_flags & FGP_ACCESSED) |
| 1897 | folio_mark_accessed(folio); |
| 1898 | else if (fgp_flags & FGP_WRITE) { |
| 1899 | /* Clear idle flag for buffer write */ |
| 1900 | if (folio_test_idle(folio)) |
| 1901 | folio_clear_idle(folio); |
| 1902 | } |
| 1903 | |
| 1904 | if (fgp_flags & FGP_STABLE) |
| 1905 | folio_wait_stable(folio); |
| 1906 | no_page: |
| 1907 | if (!folio && (fgp_flags & FGP_CREAT)) { |
| 1908 | unsigned order = FGF_GET_ORDER(fgp_flags); |
| 1909 | int err; |
| 1910 | |
| 1911 | if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping)) |
| 1912 | gfp |= __GFP_WRITE; |
| 1913 | if (fgp_flags & FGP_NOFS) |
| 1914 | gfp &= ~__GFP_FS; |
| 1915 | if (fgp_flags & FGP_NOWAIT) { |
| 1916 | gfp &= ~GFP_KERNEL; |
| 1917 | gfp |= GFP_NOWAIT | __GFP_NOWARN; |
| 1918 | } |
| 1919 | if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP)))) |
| 1920 | fgp_flags |= FGP_LOCK; |
| 1921 | |
| 1922 | if (!mapping_large_folio_support(mapping)) |
| 1923 | order = 0; |
| 1924 | if (order > MAX_PAGECACHE_ORDER) |
| 1925 | order = MAX_PAGECACHE_ORDER; |
| 1926 | /* If we're not aligned, allocate a smaller folio */ |
| 1927 | if (index & ((1UL << order) - 1)) |
| 1928 | order = __ffs(index); |
| 1929 | |
| 1930 | do { |
| 1931 | gfp_t alloc_gfp = gfp; |
| 1932 | |
| 1933 | err = -ENOMEM; |
| 1934 | if (order == 1) |
| 1935 | order = 0; |
| 1936 | if (order > 0) |
| 1937 | alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN; |
| 1938 | folio = filemap_alloc_folio(alloc_gfp, order); |
| 1939 | if (!folio) |
| 1940 | continue; |
| 1941 | |
| 1942 | /* Init accessed so avoid atomic mark_page_accessed later */ |
| 1943 | if (fgp_flags & FGP_ACCESSED) |
| 1944 | __folio_set_referenced(folio); |
| 1945 | |
| 1946 | err = filemap_add_folio(mapping, folio, index, gfp); |
| 1947 | if (!err) |
| 1948 | break; |
| 1949 | folio_put(folio); |
| 1950 | folio = NULL; |
| 1951 | } while (order-- > 0); |
| 1952 | |
| 1953 | if (err == -EEXIST) |
| 1954 | goto repeat; |
| 1955 | if (err) |
| 1956 | return ERR_PTR(err); |
| 1957 | /* |
| 1958 | * filemap_add_folio locks the page, and for mmap |
| 1959 | * we expect an unlocked page. |
| 1960 | */ |
| 1961 | if (folio && (fgp_flags & FGP_FOR_MMAP)) |
| 1962 | folio_unlock(folio); |
| 1963 | } |
| 1964 | |
| 1965 | if (!folio) |
| 1966 | return ERR_PTR(-ENOENT); |
| 1967 | return folio; |
| 1968 | } |
| 1969 | EXPORT_SYMBOL(__filemap_get_folio); |
| 1970 | |
| 1971 | static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max, |
| 1972 | xa_mark_t mark) |
| 1973 | { |
| 1974 | struct folio *folio; |
| 1975 | |
| 1976 | retry: |
| 1977 | if (mark == XA_PRESENT) |
| 1978 | folio = xas_find(xas, max); |
| 1979 | else |
| 1980 | folio = xas_find_marked(xas, max, mark); |
| 1981 | |
| 1982 | if (xas_retry(xas, folio)) |
| 1983 | goto retry; |
| 1984 | /* |
| 1985 | * A shadow entry of a recently evicted page, a swap |
| 1986 | * entry from shmem/tmpfs or a DAX entry. Return it |
| 1987 | * without attempting to raise page count. |
| 1988 | */ |
| 1989 | if (!folio || xa_is_value(folio)) |
| 1990 | return folio; |
| 1991 | |
| 1992 | if (!folio_try_get_rcu(folio)) |
| 1993 | goto reset; |
| 1994 | |
| 1995 | if (unlikely(folio != xas_reload(xas))) { |
| 1996 | folio_put(folio); |
| 1997 | goto reset; |
| 1998 | } |
| 1999 | |
| 2000 | return folio; |
| 2001 | reset: |
| 2002 | xas_reset(xas); |
| 2003 | goto retry; |
| 2004 | } |
| 2005 | |
| 2006 | /** |
| 2007 | * find_get_entries - gang pagecache lookup |
| 2008 | * @mapping: The address_space to search |
| 2009 | * @start: The starting page cache index |
| 2010 | * @end: The final page index (inclusive). |
| 2011 | * @fbatch: Where the resulting entries are placed. |
| 2012 | * @indices: The cache indices corresponding to the entries in @entries |
| 2013 | * |
| 2014 | * find_get_entries() will search for and return a batch of entries in |
| 2015 | * the mapping. The entries are placed in @fbatch. find_get_entries() |
| 2016 | * takes a reference on any actual folios it returns. |
| 2017 | * |
| 2018 | * The entries have ascending indexes. The indices may not be consecutive |
| 2019 | * due to not-present entries or large folios. |
| 2020 | * |
| 2021 | * Any shadow entries of evicted folios, or swap entries from |
| 2022 | * shmem/tmpfs, are included in the returned array. |
| 2023 | * |
| 2024 | * Return: The number of entries which were found. |
| 2025 | */ |
| 2026 | unsigned find_get_entries(struct address_space *mapping, pgoff_t *start, |
| 2027 | pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices) |
| 2028 | { |
| 2029 | XA_STATE(xas, &mapping->i_pages, *start); |
| 2030 | struct folio *folio; |
| 2031 | |
| 2032 | rcu_read_lock(); |
| 2033 | while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) { |
| 2034 | indices[fbatch->nr] = xas.xa_index; |
| 2035 | if (!folio_batch_add(fbatch, folio)) |
| 2036 | break; |
| 2037 | } |
| 2038 | rcu_read_unlock(); |
| 2039 | |
| 2040 | if (folio_batch_count(fbatch)) { |
| 2041 | unsigned long nr = 1; |
| 2042 | int idx = folio_batch_count(fbatch) - 1; |
| 2043 | |
| 2044 | folio = fbatch->folios[idx]; |
| 2045 | if (!xa_is_value(folio) && !folio_test_hugetlb(folio)) |
| 2046 | nr = folio_nr_pages(folio); |
| 2047 | *start = indices[idx] + nr; |
| 2048 | } |
| 2049 | return folio_batch_count(fbatch); |
| 2050 | } |
| 2051 | |
| 2052 | /** |
| 2053 | * find_lock_entries - Find a batch of pagecache entries. |
| 2054 | * @mapping: The address_space to search. |
| 2055 | * @start: The starting page cache index. |
| 2056 | * @end: The final page index (inclusive). |
| 2057 | * @fbatch: Where the resulting entries are placed. |
| 2058 | * @indices: The cache indices of the entries in @fbatch. |
| 2059 | * |
| 2060 | * find_lock_entries() will return a batch of entries from @mapping. |
| 2061 | * Swap, shadow and DAX entries are included. Folios are returned |
| 2062 | * locked and with an incremented refcount. Folios which are locked |
| 2063 | * by somebody else or under writeback are skipped. Folios which are |
| 2064 | * partially outside the range are not returned. |
| 2065 | * |
| 2066 | * The entries have ascending indexes. The indices may not be consecutive |
| 2067 | * due to not-present entries, large folios, folios which could not be |
| 2068 | * locked or folios under writeback. |
| 2069 | * |
| 2070 | * Return: The number of entries which were found. |
| 2071 | */ |
| 2072 | unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start, |
| 2073 | pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices) |
| 2074 | { |
| 2075 | XA_STATE(xas, &mapping->i_pages, *start); |
| 2076 | struct folio *folio; |
| 2077 | |
| 2078 | rcu_read_lock(); |
| 2079 | while ((folio = find_get_entry(&xas, end, XA_PRESENT))) { |
| 2080 | if (!xa_is_value(folio)) { |
| 2081 | if (folio->index < *start) |
| 2082 | goto put; |
| 2083 | if (folio->index + folio_nr_pages(folio) - 1 > end) |
| 2084 | goto put; |
| 2085 | if (!folio_trylock(folio)) |
| 2086 | goto put; |
| 2087 | if (folio->mapping != mapping || |
| 2088 | folio_test_writeback(folio)) |
| 2089 | goto unlock; |
| 2090 | VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index), |
| 2091 | folio); |
| 2092 | } |
| 2093 | indices[fbatch->nr] = xas.xa_index; |
| 2094 | if (!folio_batch_add(fbatch, folio)) |
| 2095 | break; |
| 2096 | continue; |
| 2097 | unlock: |
| 2098 | folio_unlock(folio); |
| 2099 | put: |
| 2100 | folio_put(folio); |
| 2101 | } |
| 2102 | rcu_read_unlock(); |
| 2103 | |
| 2104 | if (folio_batch_count(fbatch)) { |
| 2105 | unsigned long nr = 1; |
| 2106 | int idx = folio_batch_count(fbatch) - 1; |
| 2107 | |
| 2108 | folio = fbatch->folios[idx]; |
| 2109 | if (!xa_is_value(folio) && !folio_test_hugetlb(folio)) |
| 2110 | nr = folio_nr_pages(folio); |
| 2111 | *start = indices[idx] + nr; |
| 2112 | } |
| 2113 | return folio_batch_count(fbatch); |
| 2114 | } |
| 2115 | |
| 2116 | /** |
| 2117 | * filemap_get_folios - Get a batch of folios |
| 2118 | * @mapping: The address_space to search |
| 2119 | * @start: The starting page index |
| 2120 | * @end: The final page index (inclusive) |
| 2121 | * @fbatch: The batch to fill. |
| 2122 | * |
| 2123 | * Search for and return a batch of folios in the mapping starting at |
| 2124 | * index @start and up to index @end (inclusive). The folios are returned |
| 2125 | * in @fbatch with an elevated reference count. |
| 2126 | * |
| 2127 | * The first folio may start before @start; if it does, it will contain |
| 2128 | * @start. The final folio may extend beyond @end; if it does, it will |
| 2129 | * contain @end. The folios have ascending indices. There may be gaps |
| 2130 | * between the folios if there are indices which have no folio in the |
| 2131 | * page cache. If folios are added to or removed from the page cache |
| 2132 | * while this is running, they may or may not be found by this call. |
| 2133 | * |
| 2134 | * Return: The number of folios which were found. |
| 2135 | * We also update @start to index the next folio for the traversal. |
| 2136 | */ |
| 2137 | unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start, |
| 2138 | pgoff_t end, struct folio_batch *fbatch) |
| 2139 | { |
| 2140 | XA_STATE(xas, &mapping->i_pages, *start); |
| 2141 | struct folio *folio; |
| 2142 | |
| 2143 | rcu_read_lock(); |
| 2144 | while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) { |
| 2145 | /* Skip over shadow, swap and DAX entries */ |
| 2146 | if (xa_is_value(folio)) |
| 2147 | continue; |
| 2148 | if (!folio_batch_add(fbatch, folio)) { |
| 2149 | unsigned long nr = folio_nr_pages(folio); |
| 2150 | |
| 2151 | if (folio_test_hugetlb(folio)) |
| 2152 | nr = 1; |
| 2153 | *start = folio->index + nr; |
| 2154 | goto out; |
| 2155 | } |
| 2156 | } |
| 2157 | |
| 2158 | /* |
| 2159 | * We come here when there is no page beyond @end. We take care to not |
| 2160 | * overflow the index @start as it confuses some of the callers. This |
| 2161 | * breaks the iteration when there is a page at index -1 but that is |
| 2162 | * already broken anyway. |
| 2163 | */ |
| 2164 | if (end == (pgoff_t)-1) |
| 2165 | *start = (pgoff_t)-1; |
| 2166 | else |
| 2167 | *start = end + 1; |
| 2168 | out: |
| 2169 | rcu_read_unlock(); |
| 2170 | |
| 2171 | return folio_batch_count(fbatch); |
| 2172 | } |
| 2173 | EXPORT_SYMBOL(filemap_get_folios); |
| 2174 | |
| 2175 | static inline |
| 2176 | bool folio_more_pages(struct folio *folio, pgoff_t index, pgoff_t max) |
| 2177 | { |
| 2178 | if (!folio_test_large(folio) || folio_test_hugetlb(folio)) |
| 2179 | return false; |
| 2180 | if (index >= max) |
| 2181 | return false; |
| 2182 | return index < folio->index + folio_nr_pages(folio) - 1; |
| 2183 | } |
| 2184 | |
| 2185 | /** |
| 2186 | * filemap_get_folios_contig - Get a batch of contiguous folios |
| 2187 | * @mapping: The address_space to search |
| 2188 | * @start: The starting page index |
| 2189 | * @end: The final page index (inclusive) |
| 2190 | * @fbatch: The batch to fill |
| 2191 | * |
| 2192 | * filemap_get_folios_contig() works exactly like filemap_get_folios(), |
| 2193 | * except the returned folios are guaranteed to be contiguous. This may |
| 2194 | * not return all contiguous folios if the batch gets filled up. |
| 2195 | * |
| 2196 | * Return: The number of folios found. |
| 2197 | * Also update @start to be positioned for traversal of the next folio. |
| 2198 | */ |
| 2199 | |
| 2200 | unsigned filemap_get_folios_contig(struct address_space *mapping, |
| 2201 | pgoff_t *start, pgoff_t end, struct folio_batch *fbatch) |
| 2202 | { |
| 2203 | XA_STATE(xas, &mapping->i_pages, *start); |
| 2204 | unsigned long nr; |
| 2205 | struct folio *folio; |
| 2206 | |
| 2207 | rcu_read_lock(); |
| 2208 | |
| 2209 | for (folio = xas_load(&xas); folio && xas.xa_index <= end; |
| 2210 | folio = xas_next(&xas)) { |
| 2211 | if (xas_retry(&xas, folio)) |
| 2212 | continue; |
| 2213 | /* |
| 2214 | * If the entry has been swapped out, we can stop looking. |
| 2215 | * No current caller is looking for DAX entries. |
| 2216 | */ |
| 2217 | if (xa_is_value(folio)) |
| 2218 | goto update_start; |
| 2219 | |
| 2220 | if (!folio_try_get_rcu(folio)) |
| 2221 | goto retry; |
| 2222 | |
| 2223 | if (unlikely(folio != xas_reload(&xas))) |
| 2224 | goto put_folio; |
| 2225 | |
| 2226 | if (!folio_batch_add(fbatch, folio)) { |
| 2227 | nr = folio_nr_pages(folio); |
| 2228 | |
| 2229 | if (folio_test_hugetlb(folio)) |
| 2230 | nr = 1; |
| 2231 | *start = folio->index + nr; |
| 2232 | goto out; |
| 2233 | } |
| 2234 | continue; |
| 2235 | put_folio: |
| 2236 | folio_put(folio); |
| 2237 | |
| 2238 | retry: |
| 2239 | xas_reset(&xas); |
| 2240 | } |
| 2241 | |
| 2242 | update_start: |
| 2243 | nr = folio_batch_count(fbatch); |
| 2244 | |
| 2245 | if (nr) { |
| 2246 | folio = fbatch->folios[nr - 1]; |
| 2247 | if (folio_test_hugetlb(folio)) |
| 2248 | *start = folio->index + 1; |
| 2249 | else |
| 2250 | *start = folio->index + folio_nr_pages(folio); |
| 2251 | } |
| 2252 | out: |
| 2253 | rcu_read_unlock(); |
| 2254 | return folio_batch_count(fbatch); |
| 2255 | } |
| 2256 | EXPORT_SYMBOL(filemap_get_folios_contig); |
| 2257 | |
| 2258 | /** |
| 2259 | * filemap_get_folios_tag - Get a batch of folios matching @tag |
| 2260 | * @mapping: The address_space to search |
| 2261 | * @start: The starting page index |
| 2262 | * @end: The final page index (inclusive) |
| 2263 | * @tag: The tag index |
| 2264 | * @fbatch: The batch to fill |
| 2265 | * |
| 2266 | * Same as filemap_get_folios(), but only returning folios tagged with @tag. |
| 2267 | * |
| 2268 | * Return: The number of folios found. |
| 2269 | * Also update @start to index the next folio for traversal. |
| 2270 | */ |
| 2271 | unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start, |
| 2272 | pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch) |
| 2273 | { |
| 2274 | XA_STATE(xas, &mapping->i_pages, *start); |
| 2275 | struct folio *folio; |
| 2276 | |
| 2277 | rcu_read_lock(); |
| 2278 | while ((folio = find_get_entry(&xas, end, tag)) != NULL) { |
| 2279 | /* |
| 2280 | * Shadow entries should never be tagged, but this iteration |
| 2281 | * is lockless so there is a window for page reclaim to evict |
| 2282 | * a page we saw tagged. Skip over it. |
| 2283 | */ |
| 2284 | if (xa_is_value(folio)) |
| 2285 | continue; |
| 2286 | if (!folio_batch_add(fbatch, folio)) { |
| 2287 | unsigned long nr = folio_nr_pages(folio); |
| 2288 | |
| 2289 | if (folio_test_hugetlb(folio)) |
| 2290 | nr = 1; |
| 2291 | *start = folio->index + nr; |
| 2292 | goto out; |
| 2293 | } |
| 2294 | } |
| 2295 | /* |
| 2296 | * We come here when there is no page beyond @end. We take care to not |
| 2297 | * overflow the index @start as it confuses some of the callers. This |
| 2298 | * breaks the iteration when there is a page at index -1 but that is |
| 2299 | * already broke anyway. |
| 2300 | */ |
| 2301 | if (end == (pgoff_t)-1) |
| 2302 | *start = (pgoff_t)-1; |
| 2303 | else |
| 2304 | *start = end + 1; |
| 2305 | out: |
| 2306 | rcu_read_unlock(); |
| 2307 | |
| 2308 | return folio_batch_count(fbatch); |
| 2309 | } |
| 2310 | EXPORT_SYMBOL(filemap_get_folios_tag); |
| 2311 | |
| 2312 | /* |
| 2313 | * CD/DVDs are error prone. When a medium error occurs, the driver may fail |
| 2314 | * a _large_ part of the i/o request. Imagine the worst scenario: |
| 2315 | * |
| 2316 | * ---R__________________________________________B__________ |
| 2317 | * ^ reading here ^ bad block(assume 4k) |
| 2318 | * |
| 2319 | * read(R) => miss => readahead(R...B) => media error => frustrating retries |
| 2320 | * => failing the whole request => read(R) => read(R+1) => |
| 2321 | * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
| 2322 | * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
| 2323 | * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
| 2324 | * |
| 2325 | * It is going insane. Fix it by quickly scaling down the readahead size. |
| 2326 | */ |
| 2327 | static void shrink_readahead_size_eio(struct file_ra_state *ra) |
| 2328 | { |
| 2329 | ra->ra_pages /= 4; |
| 2330 | } |
| 2331 | |
| 2332 | /* |
| 2333 | * filemap_get_read_batch - Get a batch of folios for read |
| 2334 | * |
| 2335 | * Get a batch of folios which represent a contiguous range of bytes in |
| 2336 | * the file. No exceptional entries will be returned. If @index is in |
| 2337 | * the middle of a folio, the entire folio will be returned. The last |
| 2338 | * folio in the batch may have the readahead flag set or the uptodate flag |
| 2339 | * clear so that the caller can take the appropriate action. |
| 2340 | */ |
| 2341 | static void filemap_get_read_batch(struct address_space *mapping, |
| 2342 | pgoff_t index, pgoff_t max, struct folio_batch *fbatch) |
| 2343 | { |
| 2344 | XA_STATE(xas, &mapping->i_pages, index); |
| 2345 | struct folio *folio; |
| 2346 | |
| 2347 | rcu_read_lock(); |
| 2348 | for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) { |
| 2349 | if (xas_retry(&xas, folio)) |
| 2350 | continue; |
| 2351 | if (xas.xa_index > max || xa_is_value(folio)) |
| 2352 | break; |
| 2353 | if (xa_is_sibling(folio)) |
| 2354 | break; |
| 2355 | if (!folio_try_get_rcu(folio)) |
| 2356 | goto retry; |
| 2357 | |
| 2358 | if (unlikely(folio != xas_reload(&xas))) |
| 2359 | goto put_folio; |
| 2360 | |
| 2361 | if (!folio_batch_add(fbatch, folio)) |
| 2362 | break; |
| 2363 | if (!folio_test_uptodate(folio)) |
| 2364 | break; |
| 2365 | if (folio_test_readahead(folio)) |
| 2366 | break; |
| 2367 | xas_advance(&xas, folio->index + folio_nr_pages(folio) - 1); |
| 2368 | continue; |
| 2369 | put_folio: |
| 2370 | folio_put(folio); |
| 2371 | retry: |
| 2372 | xas_reset(&xas); |
| 2373 | } |
| 2374 | rcu_read_unlock(); |
| 2375 | } |
| 2376 | |
| 2377 | static int filemap_read_folio(struct file *file, filler_t filler, |
| 2378 | struct folio *folio) |
| 2379 | { |
| 2380 | bool workingset = folio_test_workingset(folio); |
| 2381 | unsigned long pflags; |
| 2382 | int error; |
| 2383 | |
| 2384 | /* |
| 2385 | * A previous I/O error may have been due to temporary failures, |
| 2386 | * eg. multipath errors. PG_error will be set again if read_folio |
| 2387 | * fails. |
| 2388 | */ |
| 2389 | folio_clear_error(folio); |
| 2390 | |
| 2391 | /* Start the actual read. The read will unlock the page. */ |
| 2392 | if (unlikely(workingset)) |
| 2393 | psi_memstall_enter(&pflags); |
| 2394 | error = filler(file, folio); |
| 2395 | if (unlikely(workingset)) |
| 2396 | psi_memstall_leave(&pflags); |
| 2397 | if (error) |
| 2398 | return error; |
| 2399 | |
| 2400 | error = folio_wait_locked_killable(folio); |
| 2401 | if (error) |
| 2402 | return error; |
| 2403 | if (folio_test_uptodate(folio)) |
| 2404 | return 0; |
| 2405 | if (file) |
| 2406 | shrink_readahead_size_eio(&file->f_ra); |
| 2407 | return -EIO; |
| 2408 | } |
| 2409 | |
| 2410 | static bool filemap_range_uptodate(struct address_space *mapping, |
| 2411 | loff_t pos, size_t count, struct folio *folio, |
| 2412 | bool need_uptodate) |
| 2413 | { |
| 2414 | if (folio_test_uptodate(folio)) |
| 2415 | return true; |
| 2416 | /* pipes can't handle partially uptodate pages */ |
| 2417 | if (need_uptodate) |
| 2418 | return false; |
| 2419 | if (!mapping->a_ops->is_partially_uptodate) |
| 2420 | return false; |
| 2421 | if (mapping->host->i_blkbits >= folio_shift(folio)) |
| 2422 | return false; |
| 2423 | |
| 2424 | if (folio_pos(folio) > pos) { |
| 2425 | count -= folio_pos(folio) - pos; |
| 2426 | pos = 0; |
| 2427 | } else { |
| 2428 | pos -= folio_pos(folio); |
| 2429 | } |
| 2430 | |
| 2431 | return mapping->a_ops->is_partially_uptodate(folio, pos, count); |
| 2432 | } |
| 2433 | |
| 2434 | static int filemap_update_page(struct kiocb *iocb, |
| 2435 | struct address_space *mapping, size_t count, |
| 2436 | struct folio *folio, bool need_uptodate) |
| 2437 | { |
| 2438 | int error; |
| 2439 | |
| 2440 | if (iocb->ki_flags & IOCB_NOWAIT) { |
| 2441 | if (!filemap_invalidate_trylock_shared(mapping)) |
| 2442 | return -EAGAIN; |
| 2443 | } else { |
| 2444 | filemap_invalidate_lock_shared(mapping); |
| 2445 | } |
| 2446 | |
| 2447 | if (!folio_trylock(folio)) { |
| 2448 | error = -EAGAIN; |
| 2449 | if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) |
| 2450 | goto unlock_mapping; |
| 2451 | if (!(iocb->ki_flags & IOCB_WAITQ)) { |
| 2452 | filemap_invalidate_unlock_shared(mapping); |
| 2453 | /* |
| 2454 | * This is where we usually end up waiting for a |
| 2455 | * previously submitted readahead to finish. |
| 2456 | */ |
| 2457 | folio_put_wait_locked(folio, TASK_KILLABLE); |
| 2458 | return AOP_TRUNCATED_PAGE; |
| 2459 | } |
| 2460 | error = __folio_lock_async(folio, iocb->ki_waitq); |
| 2461 | if (error) |
| 2462 | goto unlock_mapping; |
| 2463 | } |
| 2464 | |
| 2465 | error = AOP_TRUNCATED_PAGE; |
| 2466 | if (!folio->mapping) |
| 2467 | goto unlock; |
| 2468 | |
| 2469 | error = 0; |
| 2470 | if (filemap_range_uptodate(mapping, iocb->ki_pos, count, folio, |
| 2471 | need_uptodate)) |
| 2472 | goto unlock; |
| 2473 | |
| 2474 | error = -EAGAIN; |
| 2475 | if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) |
| 2476 | goto unlock; |
| 2477 | |
| 2478 | error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio, |
| 2479 | folio); |
| 2480 | goto unlock_mapping; |
| 2481 | unlock: |
| 2482 | folio_unlock(folio); |
| 2483 | unlock_mapping: |
| 2484 | filemap_invalidate_unlock_shared(mapping); |
| 2485 | if (error == AOP_TRUNCATED_PAGE) |
| 2486 | folio_put(folio); |
| 2487 | return error; |
| 2488 | } |
| 2489 | |
| 2490 | static int filemap_create_folio(struct file *file, |
| 2491 | struct address_space *mapping, pgoff_t index, |
| 2492 | struct folio_batch *fbatch) |
| 2493 | { |
| 2494 | struct folio *folio; |
| 2495 | int error; |
| 2496 | |
| 2497 | folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0); |
| 2498 | if (!folio) |
| 2499 | return -ENOMEM; |
| 2500 | |
| 2501 | /* |
| 2502 | * Protect against truncate / hole punch. Grabbing invalidate_lock |
| 2503 | * here assures we cannot instantiate and bring uptodate new |
| 2504 | * pagecache folios after evicting page cache during truncate |
| 2505 | * and before actually freeing blocks. Note that we could |
| 2506 | * release invalidate_lock after inserting the folio into |
| 2507 | * the page cache as the locked folio would then be enough to |
| 2508 | * synchronize with hole punching. But there are code paths |
| 2509 | * such as filemap_update_page() filling in partially uptodate |
| 2510 | * pages or ->readahead() that need to hold invalidate_lock |
| 2511 | * while mapping blocks for IO so let's hold the lock here as |
| 2512 | * well to keep locking rules simple. |
| 2513 | */ |
| 2514 | filemap_invalidate_lock_shared(mapping); |
| 2515 | error = filemap_add_folio(mapping, folio, index, |
| 2516 | mapping_gfp_constraint(mapping, GFP_KERNEL)); |
| 2517 | if (error == -EEXIST) |
| 2518 | error = AOP_TRUNCATED_PAGE; |
| 2519 | if (error) |
| 2520 | goto error; |
| 2521 | |
| 2522 | error = filemap_read_folio(file, mapping->a_ops->read_folio, folio); |
| 2523 | if (error) |
| 2524 | goto error; |
| 2525 | |
| 2526 | filemap_invalidate_unlock_shared(mapping); |
| 2527 | folio_batch_add(fbatch, folio); |
| 2528 | return 0; |
| 2529 | error: |
| 2530 | filemap_invalidate_unlock_shared(mapping); |
| 2531 | folio_put(folio); |
| 2532 | return error; |
| 2533 | } |
| 2534 | |
| 2535 | static int filemap_readahead(struct kiocb *iocb, struct file *file, |
| 2536 | struct address_space *mapping, struct folio *folio, |
| 2537 | pgoff_t last_index) |
| 2538 | { |
| 2539 | DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index); |
| 2540 | |
| 2541 | if (iocb->ki_flags & IOCB_NOIO) |
| 2542 | return -EAGAIN; |
| 2543 | page_cache_async_ra(&ractl, folio, last_index - folio->index); |
| 2544 | return 0; |
| 2545 | } |
| 2546 | |
| 2547 | static int filemap_get_pages(struct kiocb *iocb, size_t count, |
| 2548 | struct folio_batch *fbatch, bool need_uptodate) |
| 2549 | { |
| 2550 | struct file *filp = iocb->ki_filp; |
| 2551 | struct address_space *mapping = filp->f_mapping; |
| 2552 | struct file_ra_state *ra = &filp->f_ra; |
| 2553 | pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; |
| 2554 | pgoff_t last_index; |
| 2555 | struct folio *folio; |
| 2556 | int err = 0; |
| 2557 | |
| 2558 | /* "last_index" is the index of the page beyond the end of the read */ |
| 2559 | last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE); |
| 2560 | retry: |
| 2561 | if (fatal_signal_pending(current)) |
| 2562 | return -EINTR; |
| 2563 | |
| 2564 | filemap_get_read_batch(mapping, index, last_index - 1, fbatch); |
| 2565 | if (!folio_batch_count(fbatch)) { |
| 2566 | if (iocb->ki_flags & IOCB_NOIO) |
| 2567 | return -EAGAIN; |
| 2568 | page_cache_sync_readahead(mapping, ra, filp, index, |
| 2569 | last_index - index); |
| 2570 | filemap_get_read_batch(mapping, index, last_index - 1, fbatch); |
| 2571 | } |
| 2572 | if (!folio_batch_count(fbatch)) { |
| 2573 | if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) |
| 2574 | return -EAGAIN; |
| 2575 | err = filemap_create_folio(filp, mapping, |
| 2576 | iocb->ki_pos >> PAGE_SHIFT, fbatch); |
| 2577 | if (err == AOP_TRUNCATED_PAGE) |
| 2578 | goto retry; |
| 2579 | return err; |
| 2580 | } |
| 2581 | |
| 2582 | folio = fbatch->folios[folio_batch_count(fbatch) - 1]; |
| 2583 | if (folio_test_readahead(folio)) { |
| 2584 | err = filemap_readahead(iocb, filp, mapping, folio, last_index); |
| 2585 | if (err) |
| 2586 | goto err; |
| 2587 | } |
| 2588 | if (!folio_test_uptodate(folio)) { |
| 2589 | if ((iocb->ki_flags & IOCB_WAITQ) && |
| 2590 | folio_batch_count(fbatch) > 1) |
| 2591 | iocb->ki_flags |= IOCB_NOWAIT; |
| 2592 | err = filemap_update_page(iocb, mapping, count, folio, |
| 2593 | need_uptodate); |
| 2594 | if (err) |
| 2595 | goto err; |
| 2596 | } |
| 2597 | |
| 2598 | return 0; |
| 2599 | err: |
| 2600 | if (err < 0) |
| 2601 | folio_put(folio); |
| 2602 | if (likely(--fbatch->nr)) |
| 2603 | return 0; |
| 2604 | if (err == AOP_TRUNCATED_PAGE) |
| 2605 | goto retry; |
| 2606 | return err; |
| 2607 | } |
| 2608 | |
| 2609 | static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio) |
| 2610 | { |
| 2611 | unsigned int shift = folio_shift(folio); |
| 2612 | |
| 2613 | return (pos1 >> shift == pos2 >> shift); |
| 2614 | } |
| 2615 | |
| 2616 | /** |
| 2617 | * filemap_read - Read data from the page cache. |
| 2618 | * @iocb: The iocb to read. |
| 2619 | * @iter: Destination for the data. |
| 2620 | * @already_read: Number of bytes already read by the caller. |
| 2621 | * |
| 2622 | * Copies data from the page cache. If the data is not currently present, |
| 2623 | * uses the readahead and read_folio address_space operations to fetch it. |
| 2624 | * |
| 2625 | * Return: Total number of bytes copied, including those already read by |
| 2626 | * the caller. If an error happens before any bytes are copied, returns |
| 2627 | * a negative error number. |
| 2628 | */ |
| 2629 | ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter, |
| 2630 | ssize_t already_read) |
| 2631 | { |
| 2632 | struct file *filp = iocb->ki_filp; |
| 2633 | struct file_ra_state *ra = &filp->f_ra; |
| 2634 | struct address_space *mapping = filp->f_mapping; |
| 2635 | struct inode *inode = mapping->host; |
| 2636 | struct folio_batch fbatch; |
| 2637 | int i, error = 0; |
| 2638 | bool writably_mapped; |
| 2639 | loff_t isize, end_offset; |
| 2640 | |
| 2641 | if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes)) |
| 2642 | return 0; |
| 2643 | if (unlikely(!iov_iter_count(iter))) |
| 2644 | return 0; |
| 2645 | |
| 2646 | iov_iter_truncate(iter, inode->i_sb->s_maxbytes); |
| 2647 | folio_batch_init(&fbatch); |
| 2648 | |
| 2649 | do { |
| 2650 | cond_resched(); |
| 2651 | |
| 2652 | /* |
| 2653 | * If we've already successfully copied some data, then we |
| 2654 | * can no longer safely return -EIOCBQUEUED. Hence mark |
| 2655 | * an async read NOWAIT at that point. |
| 2656 | */ |
| 2657 | if ((iocb->ki_flags & IOCB_WAITQ) && already_read) |
| 2658 | iocb->ki_flags |= IOCB_NOWAIT; |
| 2659 | |
| 2660 | if (unlikely(iocb->ki_pos >= i_size_read(inode))) |
| 2661 | break; |
| 2662 | |
| 2663 | error = filemap_get_pages(iocb, iter->count, &fbatch, false); |
| 2664 | if (error < 0) |
| 2665 | break; |
| 2666 | |
| 2667 | /* |
| 2668 | * i_size must be checked after we know the pages are Uptodate. |
| 2669 | * |
| 2670 | * Checking i_size after the check allows us to calculate |
| 2671 | * the correct value for "nr", which means the zero-filled |
| 2672 | * part of the page is not copied back to userspace (unless |
| 2673 | * another truncate extends the file - this is desired though). |
| 2674 | */ |
| 2675 | isize = i_size_read(inode); |
| 2676 | if (unlikely(iocb->ki_pos >= isize)) |
| 2677 | goto put_folios; |
| 2678 | end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count); |
| 2679 | |
| 2680 | /* |
| 2681 | * Once we start copying data, we don't want to be touching any |
| 2682 | * cachelines that might be contended: |
| 2683 | */ |
| 2684 | writably_mapped = mapping_writably_mapped(mapping); |
| 2685 | |
| 2686 | /* |
| 2687 | * When a read accesses the same folio several times, only |
| 2688 | * mark it as accessed the first time. |
| 2689 | */ |
| 2690 | if (!pos_same_folio(iocb->ki_pos, ra->prev_pos - 1, |
| 2691 | fbatch.folios[0])) |
| 2692 | folio_mark_accessed(fbatch.folios[0]); |
| 2693 | |
| 2694 | for (i = 0; i < folio_batch_count(&fbatch); i++) { |
| 2695 | struct folio *folio = fbatch.folios[i]; |
| 2696 | size_t fsize = folio_size(folio); |
| 2697 | size_t offset = iocb->ki_pos & (fsize - 1); |
| 2698 | size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos, |
| 2699 | fsize - offset); |
| 2700 | size_t copied; |
| 2701 | |
| 2702 | if (end_offset < folio_pos(folio)) |
| 2703 | break; |
| 2704 | if (i > 0) |
| 2705 | folio_mark_accessed(folio); |
| 2706 | /* |
| 2707 | * If users can be writing to this folio using arbitrary |
| 2708 | * virtual addresses, take care of potential aliasing |
| 2709 | * before reading the folio on the kernel side. |
| 2710 | */ |
| 2711 | if (writably_mapped) |
| 2712 | flush_dcache_folio(folio); |
| 2713 | |
| 2714 | copied = copy_folio_to_iter(folio, offset, bytes, iter); |
| 2715 | |
| 2716 | already_read += copied; |
| 2717 | iocb->ki_pos += copied; |
| 2718 | ra->prev_pos = iocb->ki_pos; |
| 2719 | |
| 2720 | if (copied < bytes) { |
| 2721 | error = -EFAULT; |
| 2722 | break; |
| 2723 | } |
| 2724 | } |
| 2725 | put_folios: |
| 2726 | for (i = 0; i < folio_batch_count(&fbatch); i++) |
| 2727 | folio_put(fbatch.folios[i]); |
| 2728 | folio_batch_init(&fbatch); |
| 2729 | } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error); |
| 2730 | |
| 2731 | file_accessed(filp); |
| 2732 | |
| 2733 | return already_read ? already_read : error; |
| 2734 | } |
| 2735 | EXPORT_SYMBOL_GPL(filemap_read); |
| 2736 | |
| 2737 | int kiocb_write_and_wait(struct kiocb *iocb, size_t count) |
| 2738 | { |
| 2739 | struct address_space *mapping = iocb->ki_filp->f_mapping; |
| 2740 | loff_t pos = iocb->ki_pos; |
| 2741 | loff_t end = pos + count - 1; |
| 2742 | |
| 2743 | if (iocb->ki_flags & IOCB_NOWAIT) { |
| 2744 | if (filemap_range_needs_writeback(mapping, pos, end)) |
| 2745 | return -EAGAIN; |
| 2746 | return 0; |
| 2747 | } |
| 2748 | |
| 2749 | return filemap_write_and_wait_range(mapping, pos, end); |
| 2750 | } |
| 2751 | |
| 2752 | int kiocb_invalidate_pages(struct kiocb *iocb, size_t count) |
| 2753 | { |
| 2754 | struct address_space *mapping = iocb->ki_filp->f_mapping; |
| 2755 | loff_t pos = iocb->ki_pos; |
| 2756 | loff_t end = pos + count - 1; |
| 2757 | int ret; |
| 2758 | |
| 2759 | if (iocb->ki_flags & IOCB_NOWAIT) { |
| 2760 | /* we could block if there are any pages in the range */ |
| 2761 | if (filemap_range_has_page(mapping, pos, end)) |
| 2762 | return -EAGAIN; |
| 2763 | } else { |
| 2764 | ret = filemap_write_and_wait_range(mapping, pos, end); |
| 2765 | if (ret) |
| 2766 | return ret; |
| 2767 | } |
| 2768 | |
| 2769 | /* |
| 2770 | * After a write we want buffered reads to be sure to go to disk to get |
| 2771 | * the new data. We invalidate clean cached page from the region we're |
| 2772 | * about to write. We do this *before* the write so that we can return |
| 2773 | * without clobbering -EIOCBQUEUED from ->direct_IO(). |
| 2774 | */ |
| 2775 | return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, |
| 2776 | end >> PAGE_SHIFT); |
| 2777 | } |
| 2778 | |
| 2779 | /** |
| 2780 | * generic_file_read_iter - generic filesystem read routine |
| 2781 | * @iocb: kernel I/O control block |
| 2782 | * @iter: destination for the data read |
| 2783 | * |
| 2784 | * This is the "read_iter()" routine for all filesystems |
| 2785 | * that can use the page cache directly. |
| 2786 | * |
| 2787 | * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall |
| 2788 | * be returned when no data can be read without waiting for I/O requests |
| 2789 | * to complete; it doesn't prevent readahead. |
| 2790 | * |
| 2791 | * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O |
| 2792 | * requests shall be made for the read or for readahead. When no data |
| 2793 | * can be read, -EAGAIN shall be returned. When readahead would be |
| 2794 | * triggered, a partial, possibly empty read shall be returned. |
| 2795 | * |
| 2796 | * Return: |
| 2797 | * * number of bytes copied, even for partial reads |
| 2798 | * * negative error code (or 0 if IOCB_NOIO) if nothing was read |
| 2799 | */ |
| 2800 | ssize_t |
| 2801 | generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
| 2802 | { |
| 2803 | size_t count = iov_iter_count(iter); |
| 2804 | ssize_t retval = 0; |
| 2805 | |
| 2806 | if (!count) |
| 2807 | return 0; /* skip atime */ |
| 2808 | |
| 2809 | if (iocb->ki_flags & IOCB_DIRECT) { |
| 2810 | struct file *file = iocb->ki_filp; |
| 2811 | struct address_space *mapping = file->f_mapping; |
| 2812 | struct inode *inode = mapping->host; |
| 2813 | |
| 2814 | retval = kiocb_write_and_wait(iocb, count); |
| 2815 | if (retval < 0) |
| 2816 | return retval; |
| 2817 | file_accessed(file); |
| 2818 | |
| 2819 | retval = mapping->a_ops->direct_IO(iocb, iter); |
| 2820 | if (retval >= 0) { |
| 2821 | iocb->ki_pos += retval; |
| 2822 | count -= retval; |
| 2823 | } |
| 2824 | if (retval != -EIOCBQUEUED) |
| 2825 | iov_iter_revert(iter, count - iov_iter_count(iter)); |
| 2826 | |
| 2827 | /* |
| 2828 | * Btrfs can have a short DIO read if we encounter |
| 2829 | * compressed extents, so if there was an error, or if |
| 2830 | * we've already read everything we wanted to, or if |
| 2831 | * there was a short read because we hit EOF, go ahead |
| 2832 | * and return. Otherwise fallthrough to buffered io for |
| 2833 | * the rest of the read. Buffered reads will not work for |
| 2834 | * DAX files, so don't bother trying. |
| 2835 | */ |
| 2836 | if (retval < 0 || !count || IS_DAX(inode)) |
| 2837 | return retval; |
| 2838 | if (iocb->ki_pos >= i_size_read(inode)) |
| 2839 | return retval; |
| 2840 | } |
| 2841 | |
| 2842 | return filemap_read(iocb, iter, retval); |
| 2843 | } |
| 2844 | EXPORT_SYMBOL(generic_file_read_iter); |
| 2845 | |
| 2846 | /* |
| 2847 | * Splice subpages from a folio into a pipe. |
| 2848 | */ |
| 2849 | size_t splice_folio_into_pipe(struct pipe_inode_info *pipe, |
| 2850 | struct folio *folio, loff_t fpos, size_t size) |
| 2851 | { |
| 2852 | struct page *page; |
| 2853 | size_t spliced = 0, offset = offset_in_folio(folio, fpos); |
| 2854 | |
| 2855 | page = folio_page(folio, offset / PAGE_SIZE); |
| 2856 | size = min(size, folio_size(folio) - offset); |
| 2857 | offset %= PAGE_SIZE; |
| 2858 | |
| 2859 | while (spliced < size && |
| 2860 | !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) { |
| 2861 | struct pipe_buffer *buf = pipe_head_buf(pipe); |
| 2862 | size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced); |
| 2863 | |
| 2864 | *buf = (struct pipe_buffer) { |
| 2865 | .ops = &page_cache_pipe_buf_ops, |
| 2866 | .page = page, |
| 2867 | .offset = offset, |
| 2868 | .len = part, |
| 2869 | }; |
| 2870 | folio_get(folio); |
| 2871 | pipe->head++; |
| 2872 | page++; |
| 2873 | spliced += part; |
| 2874 | offset = 0; |
| 2875 | } |
| 2876 | |
| 2877 | return spliced; |
| 2878 | } |
| 2879 | |
| 2880 | /** |
| 2881 | * filemap_splice_read - Splice data from a file's pagecache into a pipe |
| 2882 | * @in: The file to read from |
| 2883 | * @ppos: Pointer to the file position to read from |
| 2884 | * @pipe: The pipe to splice into |
| 2885 | * @len: The amount to splice |
| 2886 | * @flags: The SPLICE_F_* flags |
| 2887 | * |
| 2888 | * This function gets folios from a file's pagecache and splices them into the |
| 2889 | * pipe. Readahead will be called as necessary to fill more folios. This may |
| 2890 | * be used for blockdevs also. |
| 2891 | * |
| 2892 | * Return: On success, the number of bytes read will be returned and *@ppos |
| 2893 | * will be updated if appropriate; 0 will be returned if there is no more data |
| 2894 | * to be read; -EAGAIN will be returned if the pipe had no space, and some |
| 2895 | * other negative error code will be returned on error. A short read may occur |
| 2896 | * if the pipe has insufficient space, we reach the end of the data or we hit a |
| 2897 | * hole. |
| 2898 | */ |
| 2899 | ssize_t filemap_splice_read(struct file *in, loff_t *ppos, |
| 2900 | struct pipe_inode_info *pipe, |
| 2901 | size_t len, unsigned int flags) |
| 2902 | { |
| 2903 | struct folio_batch fbatch; |
| 2904 | struct kiocb iocb; |
| 2905 | size_t total_spliced = 0, used, npages; |
| 2906 | loff_t isize, end_offset; |
| 2907 | bool writably_mapped; |
| 2908 | int i, error = 0; |
| 2909 | |
| 2910 | if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes)) |
| 2911 | return 0; |
| 2912 | |
| 2913 | init_sync_kiocb(&iocb, in); |
| 2914 | iocb.ki_pos = *ppos; |
| 2915 | |
| 2916 | /* Work out how much data we can actually add into the pipe */ |
| 2917 | used = pipe_occupancy(pipe->head, pipe->tail); |
| 2918 | npages = max_t(ssize_t, pipe->max_usage - used, 0); |
| 2919 | len = min_t(size_t, len, npages * PAGE_SIZE); |
| 2920 | |
| 2921 | folio_batch_init(&fbatch); |
| 2922 | |
| 2923 | do { |
| 2924 | cond_resched(); |
| 2925 | |
| 2926 | if (*ppos >= i_size_read(in->f_mapping->host)) |
| 2927 | break; |
| 2928 | |
| 2929 | iocb.ki_pos = *ppos; |
| 2930 | error = filemap_get_pages(&iocb, len, &fbatch, true); |
| 2931 | if (error < 0) |
| 2932 | break; |
| 2933 | |
| 2934 | /* |
| 2935 | * i_size must be checked after we know the pages are Uptodate. |
| 2936 | * |
| 2937 | * Checking i_size after the check allows us to calculate |
| 2938 | * the correct value for "nr", which means the zero-filled |
| 2939 | * part of the page is not copied back to userspace (unless |
| 2940 | * another truncate extends the file - this is desired though). |
| 2941 | */ |
| 2942 | isize = i_size_read(in->f_mapping->host); |
| 2943 | if (unlikely(*ppos >= isize)) |
| 2944 | break; |
| 2945 | end_offset = min_t(loff_t, isize, *ppos + len); |
| 2946 | |
| 2947 | /* |
| 2948 | * Once we start copying data, we don't want to be touching any |
| 2949 | * cachelines that might be contended: |
| 2950 | */ |
| 2951 | writably_mapped = mapping_writably_mapped(in->f_mapping); |
| 2952 | |
| 2953 | for (i = 0; i < folio_batch_count(&fbatch); i++) { |
| 2954 | struct folio *folio = fbatch.folios[i]; |
| 2955 | size_t n; |
| 2956 | |
| 2957 | if (folio_pos(folio) >= end_offset) |
| 2958 | goto out; |
| 2959 | folio_mark_accessed(folio); |
| 2960 | |
| 2961 | /* |
| 2962 | * If users can be writing to this folio using arbitrary |
| 2963 | * virtual addresses, take care of potential aliasing |
| 2964 | * before reading the folio on the kernel side. |
| 2965 | */ |
| 2966 | if (writably_mapped) |
| 2967 | flush_dcache_folio(folio); |
| 2968 | |
| 2969 | n = min_t(loff_t, len, isize - *ppos); |
| 2970 | n = splice_folio_into_pipe(pipe, folio, *ppos, n); |
| 2971 | if (!n) |
| 2972 | goto out; |
| 2973 | len -= n; |
| 2974 | total_spliced += n; |
| 2975 | *ppos += n; |
| 2976 | in->f_ra.prev_pos = *ppos; |
| 2977 | if (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) |
| 2978 | goto out; |
| 2979 | } |
| 2980 | |
| 2981 | folio_batch_release(&fbatch); |
| 2982 | } while (len); |
| 2983 | |
| 2984 | out: |
| 2985 | folio_batch_release(&fbatch); |
| 2986 | file_accessed(in); |
| 2987 | |
| 2988 | return total_spliced ? total_spliced : error; |
| 2989 | } |
| 2990 | EXPORT_SYMBOL(filemap_splice_read); |
| 2991 | |
| 2992 | static inline loff_t folio_seek_hole_data(struct xa_state *xas, |
| 2993 | struct address_space *mapping, struct folio *folio, |
| 2994 | loff_t start, loff_t end, bool seek_data) |
| 2995 | { |
| 2996 | const struct address_space_operations *ops = mapping->a_ops; |
| 2997 | size_t offset, bsz = i_blocksize(mapping->host); |
| 2998 | |
| 2999 | if (xa_is_value(folio) || folio_test_uptodate(folio)) |
| 3000 | return seek_data ? start : end; |
| 3001 | if (!ops->is_partially_uptodate) |
| 3002 | return seek_data ? end : start; |
| 3003 | |
| 3004 | xas_pause(xas); |
| 3005 | rcu_read_unlock(); |
| 3006 | folio_lock(folio); |
| 3007 | if (unlikely(folio->mapping != mapping)) |
| 3008 | goto unlock; |
| 3009 | |
| 3010 | offset = offset_in_folio(folio, start) & ~(bsz - 1); |
| 3011 | |
| 3012 | do { |
| 3013 | if (ops->is_partially_uptodate(folio, offset, bsz) == |
| 3014 | seek_data) |
| 3015 | break; |
| 3016 | start = (start + bsz) & ~(bsz - 1); |
| 3017 | offset += bsz; |
| 3018 | } while (offset < folio_size(folio)); |
| 3019 | unlock: |
| 3020 | folio_unlock(folio); |
| 3021 | rcu_read_lock(); |
| 3022 | return start; |
| 3023 | } |
| 3024 | |
| 3025 | static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio) |
| 3026 | { |
| 3027 | if (xa_is_value(folio)) |
| 3028 | return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index); |
| 3029 | return folio_size(folio); |
| 3030 | } |
| 3031 | |
| 3032 | /** |
| 3033 | * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache. |
| 3034 | * @mapping: Address space to search. |
| 3035 | * @start: First byte to consider. |
| 3036 | * @end: Limit of search (exclusive). |
| 3037 | * @whence: Either SEEK_HOLE or SEEK_DATA. |
| 3038 | * |
| 3039 | * If the page cache knows which blocks contain holes and which blocks |
| 3040 | * contain data, your filesystem can use this function to implement |
| 3041 | * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are |
| 3042 | * entirely memory-based such as tmpfs, and filesystems which support |
| 3043 | * unwritten extents. |
| 3044 | * |
| 3045 | * Return: The requested offset on success, or -ENXIO if @whence specifies |
| 3046 | * SEEK_DATA and there is no data after @start. There is an implicit hole |
| 3047 | * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start |
| 3048 | * and @end contain data. |
| 3049 | */ |
| 3050 | loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start, |
| 3051 | loff_t end, int whence) |
| 3052 | { |
| 3053 | XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT); |
| 3054 | pgoff_t max = (end - 1) >> PAGE_SHIFT; |
| 3055 | bool seek_data = (whence == SEEK_DATA); |
| 3056 | struct folio *folio; |
| 3057 | |
| 3058 | if (end <= start) |
| 3059 | return -ENXIO; |
| 3060 | |
| 3061 | rcu_read_lock(); |
| 3062 | while ((folio = find_get_entry(&xas, max, XA_PRESENT))) { |
| 3063 | loff_t pos = (u64)xas.xa_index << PAGE_SHIFT; |
| 3064 | size_t seek_size; |
| 3065 | |
| 3066 | if (start < pos) { |
| 3067 | if (!seek_data) |
| 3068 | goto unlock; |
| 3069 | start = pos; |
| 3070 | } |
| 3071 | |
| 3072 | seek_size = seek_folio_size(&xas, folio); |
| 3073 | pos = round_up((u64)pos + 1, seek_size); |
| 3074 | start = folio_seek_hole_data(&xas, mapping, folio, start, pos, |
| 3075 | seek_data); |
| 3076 | if (start < pos) |
| 3077 | goto unlock; |
| 3078 | if (start >= end) |
| 3079 | break; |
| 3080 | if (seek_size > PAGE_SIZE) |
| 3081 | xas_set(&xas, pos >> PAGE_SHIFT); |
| 3082 | if (!xa_is_value(folio)) |
| 3083 | folio_put(folio); |
| 3084 | } |
| 3085 | if (seek_data) |
| 3086 | start = -ENXIO; |
| 3087 | unlock: |
| 3088 | rcu_read_unlock(); |
| 3089 | if (folio && !xa_is_value(folio)) |
| 3090 | folio_put(folio); |
| 3091 | if (start > end) |
| 3092 | return end; |
| 3093 | return start; |
| 3094 | } |
| 3095 | |
| 3096 | #ifdef CONFIG_MMU |
| 3097 | #define MMAP_LOTSAMISS (100) |
| 3098 | /* |
| 3099 | * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock |
| 3100 | * @vmf - the vm_fault for this fault. |
| 3101 | * @folio - the folio to lock. |
| 3102 | * @fpin - the pointer to the file we may pin (or is already pinned). |
| 3103 | * |
| 3104 | * This works similar to lock_folio_or_retry in that it can drop the |
| 3105 | * mmap_lock. It differs in that it actually returns the folio locked |
| 3106 | * if it returns 1 and 0 if it couldn't lock the folio. If we did have |
| 3107 | * to drop the mmap_lock then fpin will point to the pinned file and |
| 3108 | * needs to be fput()'ed at a later point. |
| 3109 | */ |
| 3110 | static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio, |
| 3111 | struct file **fpin) |
| 3112 | { |
| 3113 | if (folio_trylock(folio)) |
| 3114 | return 1; |
| 3115 | |
| 3116 | /* |
| 3117 | * NOTE! This will make us return with VM_FAULT_RETRY, but with |
| 3118 | * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT |
| 3119 | * is supposed to work. We have way too many special cases.. |
| 3120 | */ |
| 3121 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
| 3122 | return 0; |
| 3123 | |
| 3124 | *fpin = maybe_unlock_mmap_for_io(vmf, *fpin); |
| 3125 | if (vmf->flags & FAULT_FLAG_KILLABLE) { |
| 3126 | if (__folio_lock_killable(folio)) { |
| 3127 | /* |
| 3128 | * We didn't have the right flags to drop the mmap_lock, |
| 3129 | * but all fault_handlers only check for fatal signals |
| 3130 | * if we return VM_FAULT_RETRY, so we need to drop the |
| 3131 | * mmap_lock here and return 0 if we don't have a fpin. |
| 3132 | */ |
| 3133 | if (*fpin == NULL) |
| 3134 | mmap_read_unlock(vmf->vma->vm_mm); |
| 3135 | return 0; |
| 3136 | } |
| 3137 | } else |
| 3138 | __folio_lock(folio); |
| 3139 | |
| 3140 | return 1; |
| 3141 | } |
| 3142 | |
| 3143 | /* |
| 3144 | * Synchronous readahead happens when we don't even find a page in the page |
| 3145 | * cache at all. We don't want to perform IO under the mmap sem, so if we have |
| 3146 | * to drop the mmap sem we return the file that was pinned in order for us to do |
| 3147 | * that. If we didn't pin a file then we return NULL. The file that is |
| 3148 | * returned needs to be fput()'ed when we're done with it. |
| 3149 | */ |
| 3150 | static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) |
| 3151 | { |
| 3152 | struct file *file = vmf->vma->vm_file; |
| 3153 | struct file_ra_state *ra = &file->f_ra; |
| 3154 | struct address_space *mapping = file->f_mapping; |
| 3155 | DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff); |
| 3156 | struct file *fpin = NULL; |
| 3157 | unsigned long vm_flags = vmf->vma->vm_flags; |
| 3158 | unsigned int mmap_miss; |
| 3159 | |
| 3160 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 3161 | /* Use the readahead code, even if readahead is disabled */ |
| 3162 | if (vm_flags & VM_HUGEPAGE) { |
| 3163 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| 3164 | ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1); |
| 3165 | ra->size = HPAGE_PMD_NR; |
| 3166 | /* |
| 3167 | * Fetch two PMD folios, so we get the chance to actually |
| 3168 | * readahead, unless we've been told not to. |
| 3169 | */ |
| 3170 | if (!(vm_flags & VM_RAND_READ)) |
| 3171 | ra->size *= 2; |
| 3172 | ra->async_size = HPAGE_PMD_NR; |
| 3173 | page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER); |
| 3174 | return fpin; |
| 3175 | } |
| 3176 | #endif |
| 3177 | |
| 3178 | /* If we don't want any read-ahead, don't bother */ |
| 3179 | if (vm_flags & VM_RAND_READ) |
| 3180 | return fpin; |
| 3181 | if (!ra->ra_pages) |
| 3182 | return fpin; |
| 3183 | |
| 3184 | if (vm_flags & VM_SEQ_READ) { |
| 3185 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| 3186 | page_cache_sync_ra(&ractl, ra->ra_pages); |
| 3187 | return fpin; |
| 3188 | } |
| 3189 | |
| 3190 | /* Avoid banging the cache line if not needed */ |
| 3191 | mmap_miss = READ_ONCE(ra->mmap_miss); |
| 3192 | if (mmap_miss < MMAP_LOTSAMISS * 10) |
| 3193 | WRITE_ONCE(ra->mmap_miss, ++mmap_miss); |
| 3194 | |
| 3195 | /* |
| 3196 | * Do we miss much more than hit in this file? If so, |
| 3197 | * stop bothering with read-ahead. It will only hurt. |
| 3198 | */ |
| 3199 | if (mmap_miss > MMAP_LOTSAMISS) |
| 3200 | return fpin; |
| 3201 | |
| 3202 | /* |
| 3203 | * mmap read-around |
| 3204 | */ |
| 3205 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| 3206 | ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2); |
| 3207 | ra->size = ra->ra_pages; |
| 3208 | ra->async_size = ra->ra_pages / 4; |
| 3209 | ractl._index = ra->start; |
| 3210 | page_cache_ra_order(&ractl, ra, 0); |
| 3211 | return fpin; |
| 3212 | } |
| 3213 | |
| 3214 | /* |
| 3215 | * Asynchronous readahead happens when we find the page and PG_readahead, |
| 3216 | * so we want to possibly extend the readahead further. We return the file that |
| 3217 | * was pinned if we have to drop the mmap_lock in order to do IO. |
| 3218 | */ |
| 3219 | static struct file *do_async_mmap_readahead(struct vm_fault *vmf, |
| 3220 | struct folio *folio) |
| 3221 | { |
| 3222 | struct file *file = vmf->vma->vm_file; |
| 3223 | struct file_ra_state *ra = &file->f_ra; |
| 3224 | DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff); |
| 3225 | struct file *fpin = NULL; |
| 3226 | unsigned int mmap_miss; |
| 3227 | |
| 3228 | /* If we don't want any read-ahead, don't bother */ |
| 3229 | if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) |
| 3230 | return fpin; |
| 3231 | |
| 3232 | mmap_miss = READ_ONCE(ra->mmap_miss); |
| 3233 | if (mmap_miss) |
| 3234 | WRITE_ONCE(ra->mmap_miss, --mmap_miss); |
| 3235 | |
| 3236 | if (folio_test_readahead(folio)) { |
| 3237 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| 3238 | page_cache_async_ra(&ractl, folio, ra->ra_pages); |
| 3239 | } |
| 3240 | return fpin; |
| 3241 | } |
| 3242 | |
| 3243 | /** |
| 3244 | * filemap_fault - read in file data for page fault handling |
| 3245 | * @vmf: struct vm_fault containing details of the fault |
| 3246 | * |
| 3247 | * filemap_fault() is invoked via the vma operations vector for a |
| 3248 | * mapped memory region to read in file data during a page fault. |
| 3249 | * |
| 3250 | * The goto's are kind of ugly, but this streamlines the normal case of having |
| 3251 | * it in the page cache, and handles the special cases reasonably without |
| 3252 | * having a lot of duplicated code. |
| 3253 | * |
| 3254 | * vma->vm_mm->mmap_lock must be held on entry. |
| 3255 | * |
| 3256 | * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock |
| 3257 | * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap(). |
| 3258 | * |
| 3259 | * If our return value does not have VM_FAULT_RETRY set, the mmap_lock |
| 3260 | * has not been released. |
| 3261 | * |
| 3262 | * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. |
| 3263 | * |
| 3264 | * Return: bitwise-OR of %VM_FAULT_ codes. |
| 3265 | */ |
| 3266 | vm_fault_t filemap_fault(struct vm_fault *vmf) |
| 3267 | { |
| 3268 | int error; |
| 3269 | struct file *file = vmf->vma->vm_file; |
| 3270 | struct file *fpin = NULL; |
| 3271 | struct address_space *mapping = file->f_mapping; |
| 3272 | struct inode *inode = mapping->host; |
| 3273 | pgoff_t max_idx, index = vmf->pgoff; |
| 3274 | struct folio *folio; |
| 3275 | vm_fault_t ret = 0; |
| 3276 | bool mapping_locked = false; |
| 3277 | |
| 3278 | max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| 3279 | if (unlikely(index >= max_idx)) |
| 3280 | return VM_FAULT_SIGBUS; |
| 3281 | |
| 3282 | /* |
| 3283 | * Do we have something in the page cache already? |
| 3284 | */ |
| 3285 | folio = filemap_get_folio(mapping, index); |
| 3286 | if (likely(!IS_ERR(folio))) { |
| 3287 | /* |
| 3288 | * We found the page, so try async readahead before waiting for |
| 3289 | * the lock. |
| 3290 | */ |
| 3291 | if (!(vmf->flags & FAULT_FLAG_TRIED)) |
| 3292 | fpin = do_async_mmap_readahead(vmf, folio); |
| 3293 | if (unlikely(!folio_test_uptodate(folio))) { |
| 3294 | filemap_invalidate_lock_shared(mapping); |
| 3295 | mapping_locked = true; |
| 3296 | } |
| 3297 | } else { |
| 3298 | /* No page in the page cache at all */ |
| 3299 | count_vm_event(PGMAJFAULT); |
| 3300 | count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); |
| 3301 | ret = VM_FAULT_MAJOR; |
| 3302 | fpin = do_sync_mmap_readahead(vmf); |
| 3303 | retry_find: |
| 3304 | /* |
| 3305 | * See comment in filemap_create_folio() why we need |
| 3306 | * invalidate_lock |
| 3307 | */ |
| 3308 | if (!mapping_locked) { |
| 3309 | filemap_invalidate_lock_shared(mapping); |
| 3310 | mapping_locked = true; |
| 3311 | } |
| 3312 | folio = __filemap_get_folio(mapping, index, |
| 3313 | FGP_CREAT|FGP_FOR_MMAP, |
| 3314 | vmf->gfp_mask); |
| 3315 | if (IS_ERR(folio)) { |
| 3316 | if (fpin) |
| 3317 | goto out_retry; |
| 3318 | filemap_invalidate_unlock_shared(mapping); |
| 3319 | return VM_FAULT_OOM; |
| 3320 | } |
| 3321 | } |
| 3322 | |
| 3323 | if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin)) |
| 3324 | goto out_retry; |
| 3325 | |
| 3326 | /* Did it get truncated? */ |
| 3327 | if (unlikely(folio->mapping != mapping)) { |
| 3328 | folio_unlock(folio); |
| 3329 | folio_put(folio); |
| 3330 | goto retry_find; |
| 3331 | } |
| 3332 | VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); |
| 3333 | |
| 3334 | /* |
| 3335 | * We have a locked page in the page cache, now we need to check |
| 3336 | * that it's up-to-date. If not, it is going to be due to an error. |
| 3337 | */ |
| 3338 | if (unlikely(!folio_test_uptodate(folio))) { |
| 3339 | /* |
| 3340 | * The page was in cache and uptodate and now it is not. |
| 3341 | * Strange but possible since we didn't hold the page lock all |
| 3342 | * the time. Let's drop everything get the invalidate lock and |
| 3343 | * try again. |
| 3344 | */ |
| 3345 | if (!mapping_locked) { |
| 3346 | folio_unlock(folio); |
| 3347 | folio_put(folio); |
| 3348 | goto retry_find; |
| 3349 | } |
| 3350 | goto page_not_uptodate; |
| 3351 | } |
| 3352 | |
| 3353 | /* |
| 3354 | * We've made it this far and we had to drop our mmap_lock, now is the |
| 3355 | * time to return to the upper layer and have it re-find the vma and |
| 3356 | * redo the fault. |
| 3357 | */ |
| 3358 | if (fpin) { |
| 3359 | folio_unlock(folio); |
| 3360 | goto out_retry; |
| 3361 | } |
| 3362 | if (mapping_locked) |
| 3363 | filemap_invalidate_unlock_shared(mapping); |
| 3364 | |
| 3365 | /* |
| 3366 | * Found the page and have a reference on it. |
| 3367 | * We must recheck i_size under page lock. |
| 3368 | */ |
| 3369 | max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
| 3370 | if (unlikely(index >= max_idx)) { |
| 3371 | folio_unlock(folio); |
| 3372 | folio_put(folio); |
| 3373 | return VM_FAULT_SIGBUS; |
| 3374 | } |
| 3375 | |
| 3376 | vmf->page = folio_file_page(folio, index); |
| 3377 | return ret | VM_FAULT_LOCKED; |
| 3378 | |
| 3379 | page_not_uptodate: |
| 3380 | /* |
| 3381 | * Umm, take care of errors if the page isn't up-to-date. |
| 3382 | * Try to re-read it _once_. We do this synchronously, |
| 3383 | * because there really aren't any performance issues here |
| 3384 | * and we need to check for errors. |
| 3385 | */ |
| 3386 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
| 3387 | error = filemap_read_folio(file, mapping->a_ops->read_folio, folio); |
| 3388 | if (fpin) |
| 3389 | goto out_retry; |
| 3390 | folio_put(folio); |
| 3391 | |
| 3392 | if (!error || error == AOP_TRUNCATED_PAGE) |
| 3393 | goto retry_find; |
| 3394 | filemap_invalidate_unlock_shared(mapping); |
| 3395 | |
| 3396 | return VM_FAULT_SIGBUS; |
| 3397 | |
| 3398 | out_retry: |
| 3399 | /* |
| 3400 | * We dropped the mmap_lock, we need to return to the fault handler to |
| 3401 | * re-find the vma and come back and find our hopefully still populated |
| 3402 | * page. |
| 3403 | */ |
| 3404 | if (!IS_ERR(folio)) |
| 3405 | folio_put(folio); |
| 3406 | if (mapping_locked) |
| 3407 | filemap_invalidate_unlock_shared(mapping); |
| 3408 | if (fpin) |
| 3409 | fput(fpin); |
| 3410 | return ret | VM_FAULT_RETRY; |
| 3411 | } |
| 3412 | EXPORT_SYMBOL(filemap_fault); |
| 3413 | |
| 3414 | static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio, |
| 3415 | pgoff_t start) |
| 3416 | { |
| 3417 | struct mm_struct *mm = vmf->vma->vm_mm; |
| 3418 | |
| 3419 | /* Huge page is mapped? No need to proceed. */ |
| 3420 | if (pmd_trans_huge(*vmf->pmd)) { |
| 3421 | folio_unlock(folio); |
| 3422 | folio_put(folio); |
| 3423 | return true; |
| 3424 | } |
| 3425 | |
| 3426 | if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) { |
| 3427 | struct page *page = folio_file_page(folio, start); |
| 3428 | vm_fault_t ret = do_set_pmd(vmf, page); |
| 3429 | if (!ret) { |
| 3430 | /* The page is mapped successfully, reference consumed. */ |
| 3431 | folio_unlock(folio); |
| 3432 | return true; |
| 3433 | } |
| 3434 | } |
| 3435 | |
| 3436 | if (pmd_none(*vmf->pmd)) |
| 3437 | pmd_install(mm, vmf->pmd, &vmf->prealloc_pte); |
| 3438 | |
| 3439 | return false; |
| 3440 | } |
| 3441 | |
| 3442 | static struct folio *next_uptodate_page(struct folio *folio, |
| 3443 | struct address_space *mapping, |
| 3444 | struct xa_state *xas, pgoff_t end_pgoff) |
| 3445 | { |
| 3446 | unsigned long max_idx; |
| 3447 | |
| 3448 | do { |
| 3449 | if (!folio) |
| 3450 | return NULL; |
| 3451 | if (xas_retry(xas, folio)) |
| 3452 | continue; |
| 3453 | if (xa_is_value(folio)) |
| 3454 | continue; |
| 3455 | if (folio_test_locked(folio)) |
| 3456 | continue; |
| 3457 | if (!folio_try_get_rcu(folio)) |
| 3458 | continue; |
| 3459 | /* Has the page moved or been split? */ |
| 3460 | if (unlikely(folio != xas_reload(xas))) |
| 3461 | goto skip; |
| 3462 | if (!folio_test_uptodate(folio) || folio_test_readahead(folio)) |
| 3463 | goto skip; |
| 3464 | if (!folio_trylock(folio)) |
| 3465 | goto skip; |
| 3466 | if (folio->mapping != mapping) |
| 3467 | goto unlock; |
| 3468 | if (!folio_test_uptodate(folio)) |
| 3469 | goto unlock; |
| 3470 | max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); |
| 3471 | if (xas->xa_index >= max_idx) |
| 3472 | goto unlock; |
| 3473 | return folio; |
| 3474 | unlock: |
| 3475 | folio_unlock(folio); |
| 3476 | skip: |
| 3477 | folio_put(folio); |
| 3478 | } while ((folio = xas_next_entry(xas, end_pgoff)) != NULL); |
| 3479 | |
| 3480 | return NULL; |
| 3481 | } |
| 3482 | |
| 3483 | static inline struct folio *first_map_page(struct address_space *mapping, |
| 3484 | struct xa_state *xas, |
| 3485 | pgoff_t end_pgoff) |
| 3486 | { |
| 3487 | return next_uptodate_page(xas_find(xas, end_pgoff), |
| 3488 | mapping, xas, end_pgoff); |
| 3489 | } |
| 3490 | |
| 3491 | static inline struct folio *next_map_page(struct address_space *mapping, |
| 3492 | struct xa_state *xas, |
| 3493 | pgoff_t end_pgoff) |
| 3494 | { |
| 3495 | return next_uptodate_page(xas_next_entry(xas, end_pgoff), |
| 3496 | mapping, xas, end_pgoff); |
| 3497 | } |
| 3498 | |
| 3499 | vm_fault_t filemap_map_pages(struct vm_fault *vmf, |
| 3500 | pgoff_t start_pgoff, pgoff_t end_pgoff) |
| 3501 | { |
| 3502 | struct vm_area_struct *vma = vmf->vma; |
| 3503 | struct file *file = vma->vm_file; |
| 3504 | struct address_space *mapping = file->f_mapping; |
| 3505 | pgoff_t last_pgoff = start_pgoff; |
| 3506 | unsigned long addr; |
| 3507 | XA_STATE(xas, &mapping->i_pages, start_pgoff); |
| 3508 | struct folio *folio; |
| 3509 | struct page *page; |
| 3510 | unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss); |
| 3511 | vm_fault_t ret = 0; |
| 3512 | |
| 3513 | rcu_read_lock(); |
| 3514 | folio = first_map_page(mapping, &xas, end_pgoff); |
| 3515 | if (!folio) |
| 3516 | goto out; |
| 3517 | |
| 3518 | if (filemap_map_pmd(vmf, folio, start_pgoff)) { |
| 3519 | ret = VM_FAULT_NOPAGE; |
| 3520 | goto out; |
| 3521 | } |
| 3522 | |
| 3523 | addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
| 3524 | vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl); |
| 3525 | if (!vmf->pte) { |
| 3526 | folio_unlock(folio); |
| 3527 | folio_put(folio); |
| 3528 | goto out; |
| 3529 | } |
| 3530 | do { |
| 3531 | again: |
| 3532 | page = folio_file_page(folio, xas.xa_index); |
| 3533 | if (PageHWPoison(page)) |
| 3534 | goto unlock; |
| 3535 | |
| 3536 | if (mmap_miss > 0) |
| 3537 | mmap_miss--; |
| 3538 | |
| 3539 | addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT; |
| 3540 | vmf->pte += xas.xa_index - last_pgoff; |
| 3541 | last_pgoff = xas.xa_index; |
| 3542 | |
| 3543 | /* |
| 3544 | * NOTE: If there're PTE markers, we'll leave them to be |
| 3545 | * handled in the specific fault path, and it'll prohibit the |
| 3546 | * fault-around logic. |
| 3547 | */ |
| 3548 | if (!pte_none(ptep_get(vmf->pte))) |
| 3549 | goto unlock; |
| 3550 | |
| 3551 | /* We're about to handle the fault */ |
| 3552 | if (vmf->address == addr) |
| 3553 | ret = VM_FAULT_NOPAGE; |
| 3554 | |
| 3555 | do_set_pte(vmf, page, addr); |
| 3556 | /* no need to invalidate: a not-present page won't be cached */ |
| 3557 | update_mmu_cache(vma, addr, vmf->pte); |
| 3558 | if (folio_more_pages(folio, xas.xa_index, end_pgoff)) { |
| 3559 | xas.xa_index++; |
| 3560 | folio_ref_inc(folio); |
| 3561 | goto again; |
| 3562 | } |
| 3563 | folio_unlock(folio); |
| 3564 | continue; |
| 3565 | unlock: |
| 3566 | if (folio_more_pages(folio, xas.xa_index, end_pgoff)) { |
| 3567 | xas.xa_index++; |
| 3568 | goto again; |
| 3569 | } |
| 3570 | folio_unlock(folio); |
| 3571 | folio_put(folio); |
| 3572 | } while ((folio = next_map_page(mapping, &xas, end_pgoff)) != NULL); |
| 3573 | pte_unmap_unlock(vmf->pte, vmf->ptl); |
| 3574 | out: |
| 3575 | rcu_read_unlock(); |
| 3576 | WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss); |
| 3577 | return ret; |
| 3578 | } |
| 3579 | EXPORT_SYMBOL(filemap_map_pages); |
| 3580 | |
| 3581 | vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) |
| 3582 | { |
| 3583 | struct address_space *mapping = vmf->vma->vm_file->f_mapping; |
| 3584 | struct folio *folio = page_folio(vmf->page); |
| 3585 | vm_fault_t ret = VM_FAULT_LOCKED; |
| 3586 | |
| 3587 | sb_start_pagefault(mapping->host->i_sb); |
| 3588 | file_update_time(vmf->vma->vm_file); |
| 3589 | folio_lock(folio); |
| 3590 | if (folio->mapping != mapping) { |
| 3591 | folio_unlock(folio); |
| 3592 | ret = VM_FAULT_NOPAGE; |
| 3593 | goto out; |
| 3594 | } |
| 3595 | /* |
| 3596 | * We mark the folio dirty already here so that when freeze is in |
| 3597 | * progress, we are guaranteed that writeback during freezing will |
| 3598 | * see the dirty folio and writeprotect it again. |
| 3599 | */ |
| 3600 | folio_mark_dirty(folio); |
| 3601 | folio_wait_stable(folio); |
| 3602 | out: |
| 3603 | sb_end_pagefault(mapping->host->i_sb); |
| 3604 | return ret; |
| 3605 | } |
| 3606 | |
| 3607 | const struct vm_operations_struct generic_file_vm_ops = { |
| 3608 | .fault = filemap_fault, |
| 3609 | .map_pages = filemap_map_pages, |
| 3610 | .page_mkwrite = filemap_page_mkwrite, |
| 3611 | }; |
| 3612 | |
| 3613 | /* This is used for a general mmap of a disk file */ |
| 3614 | |
| 3615 | int generic_file_mmap(struct file *file, struct vm_area_struct *vma) |
| 3616 | { |
| 3617 | struct address_space *mapping = file->f_mapping; |
| 3618 | |
| 3619 | if (!mapping->a_ops->read_folio) |
| 3620 | return -ENOEXEC; |
| 3621 | file_accessed(file); |
| 3622 | vma->vm_ops = &generic_file_vm_ops; |
| 3623 | return 0; |
| 3624 | } |
| 3625 | |
| 3626 | /* |
| 3627 | * This is for filesystems which do not implement ->writepage. |
| 3628 | */ |
| 3629 | int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
| 3630 | { |
| 3631 | if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) |
| 3632 | return -EINVAL; |
| 3633 | return generic_file_mmap(file, vma); |
| 3634 | } |
| 3635 | #else |
| 3636 | vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) |
| 3637 | { |
| 3638 | return VM_FAULT_SIGBUS; |
| 3639 | } |
| 3640 | int generic_file_mmap(struct file *file, struct vm_area_struct *vma) |
| 3641 | { |
| 3642 | return -ENOSYS; |
| 3643 | } |
| 3644 | int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
| 3645 | { |
| 3646 | return -ENOSYS; |
| 3647 | } |
| 3648 | #endif /* CONFIG_MMU */ |
| 3649 | |
| 3650 | EXPORT_SYMBOL(filemap_page_mkwrite); |
| 3651 | EXPORT_SYMBOL(generic_file_mmap); |
| 3652 | EXPORT_SYMBOL(generic_file_readonly_mmap); |
| 3653 | |
| 3654 | static struct folio *do_read_cache_folio(struct address_space *mapping, |
| 3655 | pgoff_t index, filler_t filler, struct file *file, gfp_t gfp) |
| 3656 | { |
| 3657 | struct folio *folio; |
| 3658 | int err; |
| 3659 | |
| 3660 | if (!filler) |
| 3661 | filler = mapping->a_ops->read_folio; |
| 3662 | repeat: |
| 3663 | folio = filemap_get_folio(mapping, index); |
| 3664 | if (IS_ERR(folio)) { |
| 3665 | folio = filemap_alloc_folio(gfp, 0); |
| 3666 | if (!folio) |
| 3667 | return ERR_PTR(-ENOMEM); |
| 3668 | err = filemap_add_folio(mapping, folio, index, gfp); |
| 3669 | if (unlikely(err)) { |
| 3670 | folio_put(folio); |
| 3671 | if (err == -EEXIST) |
| 3672 | goto repeat; |
| 3673 | /* Presumably ENOMEM for xarray node */ |
| 3674 | return ERR_PTR(err); |
| 3675 | } |
| 3676 | |
| 3677 | goto filler; |
| 3678 | } |
| 3679 | if (folio_test_uptodate(folio)) |
| 3680 | goto out; |
| 3681 | |
| 3682 | if (!folio_trylock(folio)) { |
| 3683 | folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE); |
| 3684 | goto repeat; |
| 3685 | } |
| 3686 | |
| 3687 | /* Folio was truncated from mapping */ |
| 3688 | if (!folio->mapping) { |
| 3689 | folio_unlock(folio); |
| 3690 | folio_put(folio); |
| 3691 | goto repeat; |
| 3692 | } |
| 3693 | |
| 3694 | /* Someone else locked and filled the page in a very small window */ |
| 3695 | if (folio_test_uptodate(folio)) { |
| 3696 | folio_unlock(folio); |
| 3697 | goto out; |
| 3698 | } |
| 3699 | |
| 3700 | filler: |
| 3701 | err = filemap_read_folio(file, filler, folio); |
| 3702 | if (err) { |
| 3703 | folio_put(folio); |
| 3704 | if (err == AOP_TRUNCATED_PAGE) |
| 3705 | goto repeat; |
| 3706 | return ERR_PTR(err); |
| 3707 | } |
| 3708 | |
| 3709 | out: |
| 3710 | folio_mark_accessed(folio); |
| 3711 | return folio; |
| 3712 | } |
| 3713 | |
| 3714 | /** |
| 3715 | * read_cache_folio - Read into page cache, fill it if needed. |
| 3716 | * @mapping: The address_space to read from. |
| 3717 | * @index: The index to read. |
| 3718 | * @filler: Function to perform the read, or NULL to use aops->read_folio(). |
| 3719 | * @file: Passed to filler function, may be NULL if not required. |
| 3720 | * |
| 3721 | * Read one page into the page cache. If it succeeds, the folio returned |
| 3722 | * will contain @index, but it may not be the first page of the folio. |
| 3723 | * |
| 3724 | * If the filler function returns an error, it will be returned to the |
| 3725 | * caller. |
| 3726 | * |
| 3727 | * Context: May sleep. Expects mapping->invalidate_lock to be held. |
| 3728 | * Return: An uptodate folio on success, ERR_PTR() on failure. |
| 3729 | */ |
| 3730 | struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index, |
| 3731 | filler_t filler, struct file *file) |
| 3732 | { |
| 3733 | return do_read_cache_folio(mapping, index, filler, file, |
| 3734 | mapping_gfp_mask(mapping)); |
| 3735 | } |
| 3736 | EXPORT_SYMBOL(read_cache_folio); |
| 3737 | |
| 3738 | /** |
| 3739 | * mapping_read_folio_gfp - Read into page cache, using specified allocation flags. |
| 3740 | * @mapping: The address_space for the folio. |
| 3741 | * @index: The index that the allocated folio will contain. |
| 3742 | * @gfp: The page allocator flags to use if allocating. |
| 3743 | * |
| 3744 | * This is the same as "read_cache_folio(mapping, index, NULL, NULL)", but with |
| 3745 | * any new memory allocations done using the specified allocation flags. |
| 3746 | * |
| 3747 | * The most likely error from this function is EIO, but ENOMEM is |
| 3748 | * possible and so is EINTR. If ->read_folio returns another error, |
| 3749 | * that will be returned to the caller. |
| 3750 | * |
| 3751 | * The function expects mapping->invalidate_lock to be already held. |
| 3752 | * |
| 3753 | * Return: Uptodate folio on success, ERR_PTR() on failure. |
| 3754 | */ |
| 3755 | struct folio *mapping_read_folio_gfp(struct address_space *mapping, |
| 3756 | pgoff_t index, gfp_t gfp) |
| 3757 | { |
| 3758 | return do_read_cache_folio(mapping, index, NULL, NULL, gfp); |
| 3759 | } |
| 3760 | EXPORT_SYMBOL(mapping_read_folio_gfp); |
| 3761 | |
| 3762 | static struct page *do_read_cache_page(struct address_space *mapping, |
| 3763 | pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp) |
| 3764 | { |
| 3765 | struct folio *folio; |
| 3766 | |
| 3767 | folio = do_read_cache_folio(mapping, index, filler, file, gfp); |
| 3768 | if (IS_ERR(folio)) |
| 3769 | return &folio->page; |
| 3770 | return folio_file_page(folio, index); |
| 3771 | } |
| 3772 | |
| 3773 | struct page *read_cache_page(struct address_space *mapping, |
| 3774 | pgoff_t index, filler_t *filler, struct file *file) |
| 3775 | { |
| 3776 | return do_read_cache_page(mapping, index, filler, file, |
| 3777 | mapping_gfp_mask(mapping)); |
| 3778 | } |
| 3779 | EXPORT_SYMBOL(read_cache_page); |
| 3780 | |
| 3781 | /** |
| 3782 | * read_cache_page_gfp - read into page cache, using specified page allocation flags. |
| 3783 | * @mapping: the page's address_space |
| 3784 | * @index: the page index |
| 3785 | * @gfp: the page allocator flags to use if allocating |
| 3786 | * |
| 3787 | * This is the same as "read_mapping_page(mapping, index, NULL)", but with |
| 3788 | * any new page allocations done using the specified allocation flags. |
| 3789 | * |
| 3790 | * If the page does not get brought uptodate, return -EIO. |
| 3791 | * |
| 3792 | * The function expects mapping->invalidate_lock to be already held. |
| 3793 | * |
| 3794 | * Return: up to date page on success, ERR_PTR() on failure. |
| 3795 | */ |
| 3796 | struct page *read_cache_page_gfp(struct address_space *mapping, |
| 3797 | pgoff_t index, |
| 3798 | gfp_t gfp) |
| 3799 | { |
| 3800 | return do_read_cache_page(mapping, index, NULL, NULL, gfp); |
| 3801 | } |
| 3802 | EXPORT_SYMBOL(read_cache_page_gfp); |
| 3803 | |
| 3804 | /* |
| 3805 | * Warn about a page cache invalidation failure during a direct I/O write. |
| 3806 | */ |
| 3807 | static void dio_warn_stale_pagecache(struct file *filp) |
| 3808 | { |
| 3809 | static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST); |
| 3810 | char pathname[128]; |
| 3811 | char *path; |
| 3812 | |
| 3813 | errseq_set(&filp->f_mapping->wb_err, -EIO); |
| 3814 | if (__ratelimit(&_rs)) { |
| 3815 | path = file_path(filp, pathname, sizeof(pathname)); |
| 3816 | if (IS_ERR(path)) |
| 3817 | path = "(unknown)"; |
| 3818 | pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n"); |
| 3819 | pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid, |
| 3820 | current->comm); |
| 3821 | } |
| 3822 | } |
| 3823 | |
| 3824 | void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count) |
| 3825 | { |
| 3826 | struct address_space *mapping = iocb->ki_filp->f_mapping; |
| 3827 | |
| 3828 | if (mapping->nrpages && |
| 3829 | invalidate_inode_pages2_range(mapping, |
| 3830 | iocb->ki_pos >> PAGE_SHIFT, |
| 3831 | (iocb->ki_pos + count - 1) >> PAGE_SHIFT)) |
| 3832 | dio_warn_stale_pagecache(iocb->ki_filp); |
| 3833 | } |
| 3834 | |
| 3835 | ssize_t |
| 3836 | generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) |
| 3837 | { |
| 3838 | struct address_space *mapping = iocb->ki_filp->f_mapping; |
| 3839 | size_t write_len = iov_iter_count(from); |
| 3840 | ssize_t written; |
| 3841 | |
| 3842 | /* |
| 3843 | * If a page can not be invalidated, return 0 to fall back |
| 3844 | * to buffered write. |
| 3845 | */ |
| 3846 | written = kiocb_invalidate_pages(iocb, write_len); |
| 3847 | if (written) { |
| 3848 | if (written == -EBUSY) |
| 3849 | return 0; |
| 3850 | return written; |
| 3851 | } |
| 3852 | |
| 3853 | written = mapping->a_ops->direct_IO(iocb, from); |
| 3854 | |
| 3855 | /* |
| 3856 | * Finally, try again to invalidate clean pages which might have been |
| 3857 | * cached by non-direct readahead, or faulted in by get_user_pages() |
| 3858 | * if the source of the write was an mmap'ed region of the file |
| 3859 | * we're writing. Either one is a pretty crazy thing to do, |
| 3860 | * so we don't support it 100%. If this invalidation |
| 3861 | * fails, tough, the write still worked... |
| 3862 | * |
| 3863 | * Most of the time we do not need this since dio_complete() will do |
| 3864 | * the invalidation for us. However there are some file systems that |
| 3865 | * do not end up with dio_complete() being called, so let's not break |
| 3866 | * them by removing it completely. |
| 3867 | * |
| 3868 | * Noticeable example is a blkdev_direct_IO(). |
| 3869 | * |
| 3870 | * Skip invalidation for async writes or if mapping has no pages. |
| 3871 | */ |
| 3872 | if (written > 0) { |
| 3873 | struct inode *inode = mapping->host; |
| 3874 | loff_t pos = iocb->ki_pos; |
| 3875 | |
| 3876 | kiocb_invalidate_post_direct_write(iocb, written); |
| 3877 | pos += written; |
| 3878 | write_len -= written; |
| 3879 | if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { |
| 3880 | i_size_write(inode, pos); |
| 3881 | mark_inode_dirty(inode); |
| 3882 | } |
| 3883 | iocb->ki_pos = pos; |
| 3884 | } |
| 3885 | if (written != -EIOCBQUEUED) |
| 3886 | iov_iter_revert(from, write_len - iov_iter_count(from)); |
| 3887 | return written; |
| 3888 | } |
| 3889 | EXPORT_SYMBOL(generic_file_direct_write); |
| 3890 | |
| 3891 | ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i) |
| 3892 | { |
| 3893 | struct file *file = iocb->ki_filp; |
| 3894 | loff_t pos = iocb->ki_pos; |
| 3895 | struct address_space *mapping = file->f_mapping; |
| 3896 | const struct address_space_operations *a_ops = mapping->a_ops; |
| 3897 | long status = 0; |
| 3898 | ssize_t written = 0; |
| 3899 | |
| 3900 | do { |
| 3901 | struct page *page; |
| 3902 | unsigned long offset; /* Offset into pagecache page */ |
| 3903 | unsigned long bytes; /* Bytes to write to page */ |
| 3904 | size_t copied; /* Bytes copied from user */ |
| 3905 | void *fsdata = NULL; |
| 3906 | |
| 3907 | offset = (pos & (PAGE_SIZE - 1)); |
| 3908 | bytes = min_t(unsigned long, PAGE_SIZE - offset, |
| 3909 | iov_iter_count(i)); |
| 3910 | |
| 3911 | again: |
| 3912 | /* |
| 3913 | * Bring in the user page that we will copy from _first_. |
| 3914 | * Otherwise there's a nasty deadlock on copying from the |
| 3915 | * same page as we're writing to, without it being marked |
| 3916 | * up-to-date. |
| 3917 | */ |
| 3918 | if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) { |
| 3919 | status = -EFAULT; |
| 3920 | break; |
| 3921 | } |
| 3922 | |
| 3923 | if (fatal_signal_pending(current)) { |
| 3924 | status = -EINTR; |
| 3925 | break; |
| 3926 | } |
| 3927 | |
| 3928 | status = a_ops->write_begin(file, mapping, pos, bytes, |
| 3929 | &page, &fsdata); |
| 3930 | if (unlikely(status < 0)) |
| 3931 | break; |
| 3932 | |
| 3933 | if (mapping_writably_mapped(mapping)) |
| 3934 | flush_dcache_page(page); |
| 3935 | |
| 3936 | copied = copy_page_from_iter_atomic(page, offset, bytes, i); |
| 3937 | flush_dcache_page(page); |
| 3938 | |
| 3939 | status = a_ops->write_end(file, mapping, pos, bytes, copied, |
| 3940 | page, fsdata); |
| 3941 | if (unlikely(status != copied)) { |
| 3942 | iov_iter_revert(i, copied - max(status, 0L)); |
| 3943 | if (unlikely(status < 0)) |
| 3944 | break; |
| 3945 | } |
| 3946 | cond_resched(); |
| 3947 | |
| 3948 | if (unlikely(status == 0)) { |
| 3949 | /* |
| 3950 | * A short copy made ->write_end() reject the |
| 3951 | * thing entirely. Might be memory poisoning |
| 3952 | * halfway through, might be a race with munmap, |
| 3953 | * might be severe memory pressure. |
| 3954 | */ |
| 3955 | if (copied) |
| 3956 | bytes = copied; |
| 3957 | goto again; |
| 3958 | } |
| 3959 | pos += status; |
| 3960 | written += status; |
| 3961 | |
| 3962 | balance_dirty_pages_ratelimited(mapping); |
| 3963 | } while (iov_iter_count(i)); |
| 3964 | |
| 3965 | if (!written) |
| 3966 | return status; |
| 3967 | iocb->ki_pos += written; |
| 3968 | return written; |
| 3969 | } |
| 3970 | EXPORT_SYMBOL(generic_perform_write); |
| 3971 | |
| 3972 | /** |
| 3973 | * __generic_file_write_iter - write data to a file |
| 3974 | * @iocb: IO state structure (file, offset, etc.) |
| 3975 | * @from: iov_iter with data to write |
| 3976 | * |
| 3977 | * This function does all the work needed for actually writing data to a |
| 3978 | * file. It does all basic checks, removes SUID from the file, updates |
| 3979 | * modification times and calls proper subroutines depending on whether we |
| 3980 | * do direct IO or a standard buffered write. |
| 3981 | * |
| 3982 | * It expects i_rwsem to be grabbed unless we work on a block device or similar |
| 3983 | * object which does not need locking at all. |
| 3984 | * |
| 3985 | * This function does *not* take care of syncing data in case of O_SYNC write. |
| 3986 | * A caller has to handle it. This is mainly due to the fact that we want to |
| 3987 | * avoid syncing under i_rwsem. |
| 3988 | * |
| 3989 | * Return: |
| 3990 | * * number of bytes written, even for truncated writes |
| 3991 | * * negative error code if no data has been written at all |
| 3992 | */ |
| 3993 | ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
| 3994 | { |
| 3995 | struct file *file = iocb->ki_filp; |
| 3996 | struct address_space *mapping = file->f_mapping; |
| 3997 | struct inode *inode = mapping->host; |
| 3998 | ssize_t ret; |
| 3999 | |
| 4000 | ret = file_remove_privs(file); |
| 4001 | if (ret) |
| 4002 | return ret; |
| 4003 | |
| 4004 | ret = file_update_time(file); |
| 4005 | if (ret) |
| 4006 | return ret; |
| 4007 | |
| 4008 | if (iocb->ki_flags & IOCB_DIRECT) { |
| 4009 | ret = generic_file_direct_write(iocb, from); |
| 4010 | /* |
| 4011 | * If the write stopped short of completing, fall back to |
| 4012 | * buffered writes. Some filesystems do this for writes to |
| 4013 | * holes, for example. For DAX files, a buffered write will |
| 4014 | * not succeed (even if it did, DAX does not handle dirty |
| 4015 | * page-cache pages correctly). |
| 4016 | */ |
| 4017 | if (ret < 0 || !iov_iter_count(from) || IS_DAX(inode)) |
| 4018 | return ret; |
| 4019 | return direct_write_fallback(iocb, from, ret, |
| 4020 | generic_perform_write(iocb, from)); |
| 4021 | } |
| 4022 | |
| 4023 | return generic_perform_write(iocb, from); |
| 4024 | } |
| 4025 | EXPORT_SYMBOL(__generic_file_write_iter); |
| 4026 | |
| 4027 | /** |
| 4028 | * generic_file_write_iter - write data to a file |
| 4029 | * @iocb: IO state structure |
| 4030 | * @from: iov_iter with data to write |
| 4031 | * |
| 4032 | * This is a wrapper around __generic_file_write_iter() to be used by most |
| 4033 | * filesystems. It takes care of syncing the file in case of O_SYNC file |
| 4034 | * and acquires i_rwsem as needed. |
| 4035 | * Return: |
| 4036 | * * negative error code if no data has been written at all of |
| 4037 | * vfs_fsync_range() failed for a synchronous write |
| 4038 | * * number of bytes written, even for truncated writes |
| 4039 | */ |
| 4040 | ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
| 4041 | { |
| 4042 | struct file *file = iocb->ki_filp; |
| 4043 | struct inode *inode = file->f_mapping->host; |
| 4044 | ssize_t ret; |
| 4045 | |
| 4046 | inode_lock(inode); |
| 4047 | ret = generic_write_checks(iocb, from); |
| 4048 | if (ret > 0) |
| 4049 | ret = __generic_file_write_iter(iocb, from); |
| 4050 | inode_unlock(inode); |
| 4051 | |
| 4052 | if (ret > 0) |
| 4053 | ret = generic_write_sync(iocb, ret); |
| 4054 | return ret; |
| 4055 | } |
| 4056 | EXPORT_SYMBOL(generic_file_write_iter); |
| 4057 | |
| 4058 | /** |
| 4059 | * filemap_release_folio() - Release fs-specific metadata on a folio. |
| 4060 | * @folio: The folio which the kernel is trying to free. |
| 4061 | * @gfp: Memory allocation flags (and I/O mode). |
| 4062 | * |
| 4063 | * The address_space is trying to release any data attached to a folio |
| 4064 | * (presumably at folio->private). |
| 4065 | * |
| 4066 | * This will also be called if the private_2 flag is set on a page, |
| 4067 | * indicating that the folio has other metadata associated with it. |
| 4068 | * |
| 4069 | * The @gfp argument specifies whether I/O may be performed to release |
| 4070 | * this page (__GFP_IO), and whether the call may block |
| 4071 | * (__GFP_RECLAIM & __GFP_FS). |
| 4072 | * |
| 4073 | * Return: %true if the release was successful, otherwise %false. |
| 4074 | */ |
| 4075 | bool filemap_release_folio(struct folio *folio, gfp_t gfp) |
| 4076 | { |
| 4077 | struct address_space * const mapping = folio->mapping; |
| 4078 | |
| 4079 | BUG_ON(!folio_test_locked(folio)); |
| 4080 | if (folio_test_writeback(folio)) |
| 4081 | return false; |
| 4082 | |
| 4083 | if (mapping && mapping->a_ops->release_folio) |
| 4084 | return mapping->a_ops->release_folio(folio, gfp); |
| 4085 | return try_to_free_buffers(folio); |
| 4086 | } |
| 4087 | EXPORT_SYMBOL(filemap_release_folio); |
| 4088 | |
| 4089 | #ifdef CONFIG_CACHESTAT_SYSCALL |
| 4090 | /** |
| 4091 | * filemap_cachestat() - compute the page cache statistics of a mapping |
| 4092 | * @mapping: The mapping to compute the statistics for. |
| 4093 | * @first_index: The starting page cache index. |
| 4094 | * @last_index: The final page index (inclusive). |
| 4095 | * @cs: the cachestat struct to write the result to. |
| 4096 | * |
| 4097 | * This will query the page cache statistics of a mapping in the |
| 4098 | * page range of [first_index, last_index] (inclusive). The statistics |
| 4099 | * queried include: number of dirty pages, number of pages marked for |
| 4100 | * writeback, and the number of (recently) evicted pages. |
| 4101 | */ |
| 4102 | static void filemap_cachestat(struct address_space *mapping, |
| 4103 | pgoff_t first_index, pgoff_t last_index, struct cachestat *cs) |
| 4104 | { |
| 4105 | XA_STATE(xas, &mapping->i_pages, first_index); |
| 4106 | struct folio *folio; |
| 4107 | |
| 4108 | rcu_read_lock(); |
| 4109 | xas_for_each(&xas, folio, last_index) { |
| 4110 | unsigned long nr_pages; |
| 4111 | pgoff_t folio_first_index, folio_last_index; |
| 4112 | |
| 4113 | if (xas_retry(&xas, folio)) |
| 4114 | continue; |
| 4115 | |
| 4116 | if (xa_is_value(folio)) { |
| 4117 | /* page is evicted */ |
| 4118 | void *shadow = (void *)folio; |
| 4119 | bool workingset; /* not used */ |
| 4120 | int order = xa_get_order(xas.xa, xas.xa_index); |
| 4121 | |
| 4122 | nr_pages = 1 << order; |
| 4123 | folio_first_index = round_down(xas.xa_index, 1 << order); |
| 4124 | folio_last_index = folio_first_index + nr_pages - 1; |
| 4125 | |
| 4126 | /* Folios might straddle the range boundaries, only count covered pages */ |
| 4127 | if (folio_first_index < first_index) |
| 4128 | nr_pages -= first_index - folio_first_index; |
| 4129 | |
| 4130 | if (folio_last_index > last_index) |
| 4131 | nr_pages -= folio_last_index - last_index; |
| 4132 | |
| 4133 | cs->nr_evicted += nr_pages; |
| 4134 | |
| 4135 | #ifdef CONFIG_SWAP /* implies CONFIG_MMU */ |
| 4136 | if (shmem_mapping(mapping)) { |
| 4137 | /* shmem file - in swap cache */ |
| 4138 | swp_entry_t swp = radix_to_swp_entry(folio); |
| 4139 | |
| 4140 | shadow = get_shadow_from_swap_cache(swp); |
| 4141 | } |
| 4142 | #endif |
| 4143 | if (workingset_test_recent(shadow, true, &workingset)) |
| 4144 | cs->nr_recently_evicted += nr_pages; |
| 4145 | |
| 4146 | goto resched; |
| 4147 | } |
| 4148 | |
| 4149 | nr_pages = folio_nr_pages(folio); |
| 4150 | folio_first_index = folio_pgoff(folio); |
| 4151 | folio_last_index = folio_first_index + nr_pages - 1; |
| 4152 | |
| 4153 | /* Folios might straddle the range boundaries, only count covered pages */ |
| 4154 | if (folio_first_index < first_index) |
| 4155 | nr_pages -= first_index - folio_first_index; |
| 4156 | |
| 4157 | if (folio_last_index > last_index) |
| 4158 | nr_pages -= folio_last_index - last_index; |
| 4159 | |
| 4160 | /* page is in cache */ |
| 4161 | cs->nr_cache += nr_pages; |
| 4162 | |
| 4163 | if (folio_test_dirty(folio)) |
| 4164 | cs->nr_dirty += nr_pages; |
| 4165 | |
| 4166 | if (folio_test_writeback(folio)) |
| 4167 | cs->nr_writeback += nr_pages; |
| 4168 | |
| 4169 | resched: |
| 4170 | if (need_resched()) { |
| 4171 | xas_pause(&xas); |
| 4172 | cond_resched_rcu(); |
| 4173 | } |
| 4174 | } |
| 4175 | rcu_read_unlock(); |
| 4176 | } |
| 4177 | |
| 4178 | /* |
| 4179 | * The cachestat(2) system call. |
| 4180 | * |
| 4181 | * cachestat() returns the page cache statistics of a file in the |
| 4182 | * bytes range specified by `off` and `len`: number of cached pages, |
| 4183 | * number of dirty pages, number of pages marked for writeback, |
| 4184 | * number of evicted pages, and number of recently evicted pages. |
| 4185 | * |
| 4186 | * An evicted page is a page that is previously in the page cache |
| 4187 | * but has been evicted since. A page is recently evicted if its last |
| 4188 | * eviction was recent enough that its reentry to the cache would |
| 4189 | * indicate that it is actively being used by the system, and that |
| 4190 | * there is memory pressure on the system. |
| 4191 | * |
| 4192 | * `off` and `len` must be non-negative integers. If `len` > 0, |
| 4193 | * the queried range is [`off`, `off` + `len`]. If `len` == 0, |
| 4194 | * we will query in the range from `off` to the end of the file. |
| 4195 | * |
| 4196 | * The `flags` argument is unused for now, but is included for future |
| 4197 | * extensibility. User should pass 0 (i.e no flag specified). |
| 4198 | * |
| 4199 | * Currently, hugetlbfs is not supported. |
| 4200 | * |
| 4201 | * Because the status of a page can change after cachestat() checks it |
| 4202 | * but before it returns to the application, the returned values may |
| 4203 | * contain stale information. |
| 4204 | * |
| 4205 | * return values: |
| 4206 | * zero - success |
| 4207 | * -EFAULT - cstat or cstat_range points to an illegal address |
| 4208 | * -EINVAL - invalid flags |
| 4209 | * -EBADF - invalid file descriptor |
| 4210 | * -EOPNOTSUPP - file descriptor is of a hugetlbfs file |
| 4211 | */ |
| 4212 | SYSCALL_DEFINE4(cachestat, unsigned int, fd, |
| 4213 | struct cachestat_range __user *, cstat_range, |
| 4214 | struct cachestat __user *, cstat, unsigned int, flags) |
| 4215 | { |
| 4216 | struct fd f = fdget(fd); |
| 4217 | struct address_space *mapping; |
| 4218 | struct cachestat_range csr; |
| 4219 | struct cachestat cs; |
| 4220 | pgoff_t first_index, last_index; |
| 4221 | |
| 4222 | if (!f.file) |
| 4223 | return -EBADF; |
| 4224 | |
| 4225 | if (copy_from_user(&csr, cstat_range, |
| 4226 | sizeof(struct cachestat_range))) { |
| 4227 | fdput(f); |
| 4228 | return -EFAULT; |
| 4229 | } |
| 4230 | |
| 4231 | /* hugetlbfs is not supported */ |
| 4232 | if (is_file_hugepages(f.file)) { |
| 4233 | fdput(f); |
| 4234 | return -EOPNOTSUPP; |
| 4235 | } |
| 4236 | |
| 4237 | if (flags != 0) { |
| 4238 | fdput(f); |
| 4239 | return -EINVAL; |
| 4240 | } |
| 4241 | |
| 4242 | first_index = csr.off >> PAGE_SHIFT; |
| 4243 | last_index = |
| 4244 | csr.len == 0 ? ULONG_MAX : (csr.off + csr.len - 1) >> PAGE_SHIFT; |
| 4245 | memset(&cs, 0, sizeof(struct cachestat)); |
| 4246 | mapping = f.file->f_mapping; |
| 4247 | filemap_cachestat(mapping, first_index, last_index, &cs); |
| 4248 | fdput(f); |
| 4249 | |
| 4250 | if (copy_to_user(cstat, &cs, sizeof(struct cachestat))) |
| 4251 | return -EFAULT; |
| 4252 | |
| 4253 | return 0; |
| 4254 | } |
| 4255 | #endif /* CONFIG_CACHESTAT_SYSCALL */ |