| 1 | /* |
| 2 | * Memory Migration functionality - linux/mm/migration.c |
| 3 | * |
| 4 | * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter |
| 5 | * |
| 6 | * Page migration was first developed in the context of the memory hotplug |
| 7 | * project. The main authors of the migration code are: |
| 8 | * |
| 9 | * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> |
| 10 | * Hirokazu Takahashi <taka@valinux.co.jp> |
| 11 | * Dave Hansen <haveblue@us.ibm.com> |
| 12 | * Christoph Lameter |
| 13 | */ |
| 14 | |
| 15 | #include <linux/migrate.h> |
| 16 | #include <linux/module.h> |
| 17 | #include <linux/swap.h> |
| 18 | #include <linux/swapops.h> |
| 19 | #include <linux/pagemap.h> |
| 20 | #include <linux/buffer_head.h> |
| 21 | #include <linux/mm_inline.h> |
| 22 | #include <linux/nsproxy.h> |
| 23 | #include <linux/pagevec.h> |
| 24 | #include <linux/rmap.h> |
| 25 | #include <linux/topology.h> |
| 26 | #include <linux/cpu.h> |
| 27 | #include <linux/cpuset.h> |
| 28 | #include <linux/writeback.h> |
| 29 | #include <linux/mempolicy.h> |
| 30 | #include <linux/vmalloc.h> |
| 31 | #include <linux/security.h> |
| 32 | #include <linux/memcontrol.h> |
| 33 | #include <linux/syscalls.h> |
| 34 | |
| 35 | #include "internal.h" |
| 36 | |
| 37 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
| 38 | |
| 39 | /* |
| 40 | * migrate_prep() needs to be called before we start compiling a list of pages |
| 41 | * to be migrated using isolate_lru_page(). |
| 42 | */ |
| 43 | int migrate_prep(void) |
| 44 | { |
| 45 | /* |
| 46 | * Clear the LRU lists so pages can be isolated. |
| 47 | * Note that pages may be moved off the LRU after we have |
| 48 | * drained them. Those pages will fail to migrate like other |
| 49 | * pages that may be busy. |
| 50 | */ |
| 51 | lru_add_drain_all(); |
| 52 | |
| 53 | return 0; |
| 54 | } |
| 55 | |
| 56 | /* |
| 57 | * Add isolated pages on the list back to the LRU under page lock |
| 58 | * to avoid leaking evictable pages back onto unevictable list. |
| 59 | * |
| 60 | * returns the number of pages put back. |
| 61 | */ |
| 62 | int putback_lru_pages(struct list_head *l) |
| 63 | { |
| 64 | struct page *page; |
| 65 | struct page *page2; |
| 66 | int count = 0; |
| 67 | |
| 68 | list_for_each_entry_safe(page, page2, l, lru) { |
| 69 | list_del(&page->lru); |
| 70 | dec_zone_page_state(page, NR_ISOLATED_ANON + |
| 71 | page_is_file_cache(page)); |
| 72 | putback_lru_page(page); |
| 73 | count++; |
| 74 | } |
| 75 | return count; |
| 76 | } |
| 77 | |
| 78 | /* |
| 79 | * Restore a potential migration pte to a working pte entry |
| 80 | */ |
| 81 | static void remove_migration_pte(struct vm_area_struct *vma, |
| 82 | struct page *old, struct page *new) |
| 83 | { |
| 84 | struct mm_struct *mm = vma->vm_mm; |
| 85 | swp_entry_t entry; |
| 86 | pgd_t *pgd; |
| 87 | pud_t *pud; |
| 88 | pmd_t *pmd; |
| 89 | pte_t *ptep, pte; |
| 90 | spinlock_t *ptl; |
| 91 | unsigned long addr = page_address_in_vma(new, vma); |
| 92 | |
| 93 | if (addr == -EFAULT) |
| 94 | return; |
| 95 | |
| 96 | pgd = pgd_offset(mm, addr); |
| 97 | if (!pgd_present(*pgd)) |
| 98 | return; |
| 99 | |
| 100 | pud = pud_offset(pgd, addr); |
| 101 | if (!pud_present(*pud)) |
| 102 | return; |
| 103 | |
| 104 | pmd = pmd_offset(pud, addr); |
| 105 | if (!pmd_present(*pmd)) |
| 106 | return; |
| 107 | |
| 108 | ptep = pte_offset_map(pmd, addr); |
| 109 | |
| 110 | if (!is_swap_pte(*ptep)) { |
| 111 | pte_unmap(ptep); |
| 112 | return; |
| 113 | } |
| 114 | |
| 115 | ptl = pte_lockptr(mm, pmd); |
| 116 | spin_lock(ptl); |
| 117 | pte = *ptep; |
| 118 | if (!is_swap_pte(pte)) |
| 119 | goto out; |
| 120 | |
| 121 | entry = pte_to_swp_entry(pte); |
| 122 | |
| 123 | if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) |
| 124 | goto out; |
| 125 | |
| 126 | get_page(new); |
| 127 | pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); |
| 128 | if (is_write_migration_entry(entry)) |
| 129 | pte = pte_mkwrite(pte); |
| 130 | flush_cache_page(vma, addr, pte_pfn(pte)); |
| 131 | set_pte_at(mm, addr, ptep, pte); |
| 132 | |
| 133 | if (PageAnon(new)) |
| 134 | page_add_anon_rmap(new, vma, addr); |
| 135 | else |
| 136 | page_add_file_rmap(new); |
| 137 | |
| 138 | /* No need to invalidate - it was non-present before */ |
| 139 | update_mmu_cache(vma, addr, pte); |
| 140 | |
| 141 | out: |
| 142 | pte_unmap_unlock(ptep, ptl); |
| 143 | } |
| 144 | |
| 145 | /* |
| 146 | * Note that remove_file_migration_ptes will only work on regular mappings, |
| 147 | * Nonlinear mappings do not use migration entries. |
| 148 | */ |
| 149 | static void remove_file_migration_ptes(struct page *old, struct page *new) |
| 150 | { |
| 151 | struct vm_area_struct *vma; |
| 152 | struct address_space *mapping = new->mapping; |
| 153 | struct prio_tree_iter iter; |
| 154 | pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| 155 | |
| 156 | if (!mapping) |
| 157 | return; |
| 158 | |
| 159 | spin_lock(&mapping->i_mmap_lock); |
| 160 | |
| 161 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) |
| 162 | remove_migration_pte(vma, old, new); |
| 163 | |
| 164 | spin_unlock(&mapping->i_mmap_lock); |
| 165 | } |
| 166 | |
| 167 | /* |
| 168 | * Must hold mmap_sem lock on at least one of the vmas containing |
| 169 | * the page so that the anon_vma cannot vanish. |
| 170 | */ |
| 171 | static void remove_anon_migration_ptes(struct page *old, struct page *new) |
| 172 | { |
| 173 | struct anon_vma *anon_vma; |
| 174 | struct vm_area_struct *vma; |
| 175 | unsigned long mapping; |
| 176 | |
| 177 | mapping = (unsigned long)new->mapping; |
| 178 | |
| 179 | if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0) |
| 180 | return; |
| 181 | |
| 182 | /* |
| 183 | * We hold the mmap_sem lock. So no need to call page_lock_anon_vma. |
| 184 | */ |
| 185 | anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON); |
| 186 | spin_lock(&anon_vma->lock); |
| 187 | |
| 188 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) |
| 189 | remove_migration_pte(vma, old, new); |
| 190 | |
| 191 | spin_unlock(&anon_vma->lock); |
| 192 | } |
| 193 | |
| 194 | /* |
| 195 | * Get rid of all migration entries and replace them by |
| 196 | * references to the indicated page. |
| 197 | */ |
| 198 | static void remove_migration_ptes(struct page *old, struct page *new) |
| 199 | { |
| 200 | if (PageAnon(new)) |
| 201 | remove_anon_migration_ptes(old, new); |
| 202 | else |
| 203 | remove_file_migration_ptes(old, new); |
| 204 | } |
| 205 | |
| 206 | /* |
| 207 | * Something used the pte of a page under migration. We need to |
| 208 | * get to the page and wait until migration is finished. |
| 209 | * When we return from this function the fault will be retried. |
| 210 | * |
| 211 | * This function is called from do_swap_page(). |
| 212 | */ |
| 213 | void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, |
| 214 | unsigned long address) |
| 215 | { |
| 216 | pte_t *ptep, pte; |
| 217 | spinlock_t *ptl; |
| 218 | swp_entry_t entry; |
| 219 | struct page *page; |
| 220 | |
| 221 | ptep = pte_offset_map_lock(mm, pmd, address, &ptl); |
| 222 | pte = *ptep; |
| 223 | if (!is_swap_pte(pte)) |
| 224 | goto out; |
| 225 | |
| 226 | entry = pte_to_swp_entry(pte); |
| 227 | if (!is_migration_entry(entry)) |
| 228 | goto out; |
| 229 | |
| 230 | page = migration_entry_to_page(entry); |
| 231 | |
| 232 | /* |
| 233 | * Once radix-tree replacement of page migration started, page_count |
| 234 | * *must* be zero. And, we don't want to call wait_on_page_locked() |
| 235 | * against a page without get_page(). |
| 236 | * So, we use get_page_unless_zero(), here. Even failed, page fault |
| 237 | * will occur again. |
| 238 | */ |
| 239 | if (!get_page_unless_zero(page)) |
| 240 | goto out; |
| 241 | pte_unmap_unlock(ptep, ptl); |
| 242 | wait_on_page_locked(page); |
| 243 | put_page(page); |
| 244 | return; |
| 245 | out: |
| 246 | pte_unmap_unlock(ptep, ptl); |
| 247 | } |
| 248 | |
| 249 | /* |
| 250 | * Replace the page in the mapping. |
| 251 | * |
| 252 | * The number of remaining references must be: |
| 253 | * 1 for anonymous pages without a mapping |
| 254 | * 2 for pages with a mapping |
| 255 | * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. |
| 256 | */ |
| 257 | static int migrate_page_move_mapping(struct address_space *mapping, |
| 258 | struct page *newpage, struct page *page) |
| 259 | { |
| 260 | int expected_count; |
| 261 | void **pslot; |
| 262 | |
| 263 | if (!mapping) { |
| 264 | /* Anonymous page without mapping */ |
| 265 | if (page_count(page) != 1) |
| 266 | return -EAGAIN; |
| 267 | return 0; |
| 268 | } |
| 269 | |
| 270 | spin_lock_irq(&mapping->tree_lock); |
| 271 | |
| 272 | pslot = radix_tree_lookup_slot(&mapping->page_tree, |
| 273 | page_index(page)); |
| 274 | |
| 275 | expected_count = 2 + page_has_private(page); |
| 276 | if (page_count(page) != expected_count || |
| 277 | (struct page *)radix_tree_deref_slot(pslot) != page) { |
| 278 | spin_unlock_irq(&mapping->tree_lock); |
| 279 | return -EAGAIN; |
| 280 | } |
| 281 | |
| 282 | if (!page_freeze_refs(page, expected_count)) { |
| 283 | spin_unlock_irq(&mapping->tree_lock); |
| 284 | return -EAGAIN; |
| 285 | } |
| 286 | |
| 287 | /* |
| 288 | * Now we know that no one else is looking at the page. |
| 289 | */ |
| 290 | get_page(newpage); /* add cache reference */ |
| 291 | if (PageSwapCache(page)) { |
| 292 | SetPageSwapCache(newpage); |
| 293 | set_page_private(newpage, page_private(page)); |
| 294 | } |
| 295 | |
| 296 | radix_tree_replace_slot(pslot, newpage); |
| 297 | |
| 298 | page_unfreeze_refs(page, expected_count); |
| 299 | /* |
| 300 | * Drop cache reference from old page. |
| 301 | * We know this isn't the last reference. |
| 302 | */ |
| 303 | __put_page(page); |
| 304 | |
| 305 | /* |
| 306 | * If moved to a different zone then also account |
| 307 | * the page for that zone. Other VM counters will be |
| 308 | * taken care of when we establish references to the |
| 309 | * new page and drop references to the old page. |
| 310 | * |
| 311 | * Note that anonymous pages are accounted for |
| 312 | * via NR_FILE_PAGES and NR_ANON_PAGES if they |
| 313 | * are mapped to swap space. |
| 314 | */ |
| 315 | __dec_zone_page_state(page, NR_FILE_PAGES); |
| 316 | __inc_zone_page_state(newpage, NR_FILE_PAGES); |
| 317 | if (PageSwapBacked(page)) { |
| 318 | __dec_zone_page_state(page, NR_SHMEM); |
| 319 | __inc_zone_page_state(newpage, NR_SHMEM); |
| 320 | } |
| 321 | spin_unlock_irq(&mapping->tree_lock); |
| 322 | |
| 323 | return 0; |
| 324 | } |
| 325 | |
| 326 | /* |
| 327 | * Copy the page to its new location |
| 328 | */ |
| 329 | static void migrate_page_copy(struct page *newpage, struct page *page) |
| 330 | { |
| 331 | int anon; |
| 332 | |
| 333 | copy_highpage(newpage, page); |
| 334 | |
| 335 | if (PageError(page)) |
| 336 | SetPageError(newpage); |
| 337 | if (PageReferenced(page)) |
| 338 | SetPageReferenced(newpage); |
| 339 | if (PageUptodate(page)) |
| 340 | SetPageUptodate(newpage); |
| 341 | if (TestClearPageActive(page)) { |
| 342 | VM_BUG_ON(PageUnevictable(page)); |
| 343 | SetPageActive(newpage); |
| 344 | } else |
| 345 | unevictable_migrate_page(newpage, page); |
| 346 | if (PageChecked(page)) |
| 347 | SetPageChecked(newpage); |
| 348 | if (PageMappedToDisk(page)) |
| 349 | SetPageMappedToDisk(newpage); |
| 350 | |
| 351 | if (PageDirty(page)) { |
| 352 | clear_page_dirty_for_io(page); |
| 353 | /* |
| 354 | * Want to mark the page and the radix tree as dirty, and |
| 355 | * redo the accounting that clear_page_dirty_for_io undid, |
| 356 | * but we can't use set_page_dirty because that function |
| 357 | * is actually a signal that all of the page has become dirty. |
| 358 | * Wheras only part of our page may be dirty. |
| 359 | */ |
| 360 | __set_page_dirty_nobuffers(newpage); |
| 361 | } |
| 362 | |
| 363 | mlock_migrate_page(newpage, page); |
| 364 | |
| 365 | ClearPageSwapCache(page); |
| 366 | ClearPagePrivate(page); |
| 367 | set_page_private(page, 0); |
| 368 | /* page->mapping contains a flag for PageAnon() */ |
| 369 | anon = PageAnon(page); |
| 370 | page->mapping = NULL; |
| 371 | |
| 372 | /* |
| 373 | * If any waiters have accumulated on the new page then |
| 374 | * wake them up. |
| 375 | */ |
| 376 | if (PageWriteback(newpage)) |
| 377 | end_page_writeback(newpage); |
| 378 | } |
| 379 | |
| 380 | /************************************************************ |
| 381 | * Migration functions |
| 382 | ***********************************************************/ |
| 383 | |
| 384 | /* Always fail migration. Used for mappings that are not movable */ |
| 385 | int fail_migrate_page(struct address_space *mapping, |
| 386 | struct page *newpage, struct page *page) |
| 387 | { |
| 388 | return -EIO; |
| 389 | } |
| 390 | EXPORT_SYMBOL(fail_migrate_page); |
| 391 | |
| 392 | /* |
| 393 | * Common logic to directly migrate a single page suitable for |
| 394 | * pages that do not use PagePrivate/PagePrivate2. |
| 395 | * |
| 396 | * Pages are locked upon entry and exit. |
| 397 | */ |
| 398 | int migrate_page(struct address_space *mapping, |
| 399 | struct page *newpage, struct page *page) |
| 400 | { |
| 401 | int rc; |
| 402 | |
| 403 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ |
| 404 | |
| 405 | rc = migrate_page_move_mapping(mapping, newpage, page); |
| 406 | |
| 407 | if (rc) |
| 408 | return rc; |
| 409 | |
| 410 | migrate_page_copy(newpage, page); |
| 411 | return 0; |
| 412 | } |
| 413 | EXPORT_SYMBOL(migrate_page); |
| 414 | |
| 415 | #ifdef CONFIG_BLOCK |
| 416 | /* |
| 417 | * Migration function for pages with buffers. This function can only be used |
| 418 | * if the underlying filesystem guarantees that no other references to "page" |
| 419 | * exist. |
| 420 | */ |
| 421 | int buffer_migrate_page(struct address_space *mapping, |
| 422 | struct page *newpage, struct page *page) |
| 423 | { |
| 424 | struct buffer_head *bh, *head; |
| 425 | int rc; |
| 426 | |
| 427 | if (!page_has_buffers(page)) |
| 428 | return migrate_page(mapping, newpage, page); |
| 429 | |
| 430 | head = page_buffers(page); |
| 431 | |
| 432 | rc = migrate_page_move_mapping(mapping, newpage, page); |
| 433 | |
| 434 | if (rc) |
| 435 | return rc; |
| 436 | |
| 437 | bh = head; |
| 438 | do { |
| 439 | get_bh(bh); |
| 440 | lock_buffer(bh); |
| 441 | bh = bh->b_this_page; |
| 442 | |
| 443 | } while (bh != head); |
| 444 | |
| 445 | ClearPagePrivate(page); |
| 446 | set_page_private(newpage, page_private(page)); |
| 447 | set_page_private(page, 0); |
| 448 | put_page(page); |
| 449 | get_page(newpage); |
| 450 | |
| 451 | bh = head; |
| 452 | do { |
| 453 | set_bh_page(bh, newpage, bh_offset(bh)); |
| 454 | bh = bh->b_this_page; |
| 455 | |
| 456 | } while (bh != head); |
| 457 | |
| 458 | SetPagePrivate(newpage); |
| 459 | |
| 460 | migrate_page_copy(newpage, page); |
| 461 | |
| 462 | bh = head; |
| 463 | do { |
| 464 | unlock_buffer(bh); |
| 465 | put_bh(bh); |
| 466 | bh = bh->b_this_page; |
| 467 | |
| 468 | } while (bh != head); |
| 469 | |
| 470 | return 0; |
| 471 | } |
| 472 | EXPORT_SYMBOL(buffer_migrate_page); |
| 473 | #endif |
| 474 | |
| 475 | /* |
| 476 | * Writeback a page to clean the dirty state |
| 477 | */ |
| 478 | static int writeout(struct address_space *mapping, struct page *page) |
| 479 | { |
| 480 | struct writeback_control wbc = { |
| 481 | .sync_mode = WB_SYNC_NONE, |
| 482 | .nr_to_write = 1, |
| 483 | .range_start = 0, |
| 484 | .range_end = LLONG_MAX, |
| 485 | .nonblocking = 1, |
| 486 | .for_reclaim = 1 |
| 487 | }; |
| 488 | int rc; |
| 489 | |
| 490 | if (!mapping->a_ops->writepage) |
| 491 | /* No write method for the address space */ |
| 492 | return -EINVAL; |
| 493 | |
| 494 | if (!clear_page_dirty_for_io(page)) |
| 495 | /* Someone else already triggered a write */ |
| 496 | return -EAGAIN; |
| 497 | |
| 498 | /* |
| 499 | * A dirty page may imply that the underlying filesystem has |
| 500 | * the page on some queue. So the page must be clean for |
| 501 | * migration. Writeout may mean we loose the lock and the |
| 502 | * page state is no longer what we checked for earlier. |
| 503 | * At this point we know that the migration attempt cannot |
| 504 | * be successful. |
| 505 | */ |
| 506 | remove_migration_ptes(page, page); |
| 507 | |
| 508 | rc = mapping->a_ops->writepage(page, &wbc); |
| 509 | |
| 510 | if (rc != AOP_WRITEPAGE_ACTIVATE) |
| 511 | /* unlocked. Relock */ |
| 512 | lock_page(page); |
| 513 | |
| 514 | return (rc < 0) ? -EIO : -EAGAIN; |
| 515 | } |
| 516 | |
| 517 | /* |
| 518 | * Default handling if a filesystem does not provide a migration function. |
| 519 | */ |
| 520 | static int fallback_migrate_page(struct address_space *mapping, |
| 521 | struct page *newpage, struct page *page) |
| 522 | { |
| 523 | if (PageDirty(page)) |
| 524 | return writeout(mapping, page); |
| 525 | |
| 526 | /* |
| 527 | * Buffers may be managed in a filesystem specific way. |
| 528 | * We must have no buffers or drop them. |
| 529 | */ |
| 530 | if (page_has_private(page) && |
| 531 | !try_to_release_page(page, GFP_KERNEL)) |
| 532 | return -EAGAIN; |
| 533 | |
| 534 | return migrate_page(mapping, newpage, page); |
| 535 | } |
| 536 | |
| 537 | /* |
| 538 | * Move a page to a newly allocated page |
| 539 | * The page is locked and all ptes have been successfully removed. |
| 540 | * |
| 541 | * The new page will have replaced the old page if this function |
| 542 | * is successful. |
| 543 | * |
| 544 | * Return value: |
| 545 | * < 0 - error code |
| 546 | * == 0 - success |
| 547 | */ |
| 548 | static int move_to_new_page(struct page *newpage, struct page *page) |
| 549 | { |
| 550 | struct address_space *mapping; |
| 551 | int rc; |
| 552 | |
| 553 | /* |
| 554 | * Block others from accessing the page when we get around to |
| 555 | * establishing additional references. We are the only one |
| 556 | * holding a reference to the new page at this point. |
| 557 | */ |
| 558 | if (!trylock_page(newpage)) |
| 559 | BUG(); |
| 560 | |
| 561 | /* Prepare mapping for the new page.*/ |
| 562 | newpage->index = page->index; |
| 563 | newpage->mapping = page->mapping; |
| 564 | if (PageSwapBacked(page)) |
| 565 | SetPageSwapBacked(newpage); |
| 566 | |
| 567 | mapping = page_mapping(page); |
| 568 | if (!mapping) |
| 569 | rc = migrate_page(mapping, newpage, page); |
| 570 | else if (mapping->a_ops->migratepage) |
| 571 | /* |
| 572 | * Most pages have a mapping and most filesystems |
| 573 | * should provide a migration function. Anonymous |
| 574 | * pages are part of swap space which also has its |
| 575 | * own migration function. This is the most common |
| 576 | * path for page migration. |
| 577 | */ |
| 578 | rc = mapping->a_ops->migratepage(mapping, |
| 579 | newpage, page); |
| 580 | else |
| 581 | rc = fallback_migrate_page(mapping, newpage, page); |
| 582 | |
| 583 | if (!rc) { |
| 584 | remove_migration_ptes(page, newpage); |
| 585 | } else |
| 586 | newpage->mapping = NULL; |
| 587 | |
| 588 | unlock_page(newpage); |
| 589 | |
| 590 | return rc; |
| 591 | } |
| 592 | |
| 593 | /* |
| 594 | * Obtain the lock on page, remove all ptes and migrate the page |
| 595 | * to the newly allocated page in newpage. |
| 596 | */ |
| 597 | static int unmap_and_move(new_page_t get_new_page, unsigned long private, |
| 598 | struct page *page, int force) |
| 599 | { |
| 600 | int rc = 0; |
| 601 | int *result = NULL; |
| 602 | struct page *newpage = get_new_page(page, private, &result); |
| 603 | int rcu_locked = 0; |
| 604 | int charge = 0; |
| 605 | struct mem_cgroup *mem; |
| 606 | |
| 607 | if (!newpage) |
| 608 | return -ENOMEM; |
| 609 | |
| 610 | if (page_count(page) == 1) { |
| 611 | /* page was freed from under us. So we are done. */ |
| 612 | goto move_newpage; |
| 613 | } |
| 614 | |
| 615 | /* prepare cgroup just returns 0 or -ENOMEM */ |
| 616 | rc = -EAGAIN; |
| 617 | |
| 618 | if (!trylock_page(page)) { |
| 619 | if (!force) |
| 620 | goto move_newpage; |
| 621 | lock_page(page); |
| 622 | } |
| 623 | |
| 624 | /* charge against new page */ |
| 625 | charge = mem_cgroup_prepare_migration(page, &mem); |
| 626 | if (charge == -ENOMEM) { |
| 627 | rc = -ENOMEM; |
| 628 | goto unlock; |
| 629 | } |
| 630 | BUG_ON(charge); |
| 631 | |
| 632 | if (PageWriteback(page)) { |
| 633 | if (!force) |
| 634 | goto uncharge; |
| 635 | wait_on_page_writeback(page); |
| 636 | } |
| 637 | /* |
| 638 | * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, |
| 639 | * we cannot notice that anon_vma is freed while we migrates a page. |
| 640 | * This rcu_read_lock() delays freeing anon_vma pointer until the end |
| 641 | * of migration. File cache pages are no problem because of page_lock() |
| 642 | * File Caches may use write_page() or lock_page() in migration, then, |
| 643 | * just care Anon page here. |
| 644 | */ |
| 645 | if (PageAnon(page)) { |
| 646 | rcu_read_lock(); |
| 647 | rcu_locked = 1; |
| 648 | } |
| 649 | |
| 650 | /* |
| 651 | * Corner case handling: |
| 652 | * 1. When a new swap-cache page is read into, it is added to the LRU |
| 653 | * and treated as swapcache but it has no rmap yet. |
| 654 | * Calling try_to_unmap() against a page->mapping==NULL page will |
| 655 | * trigger a BUG. So handle it here. |
| 656 | * 2. An orphaned page (see truncate_complete_page) might have |
| 657 | * fs-private metadata. The page can be picked up due to memory |
| 658 | * offlining. Everywhere else except page reclaim, the page is |
| 659 | * invisible to the vm, so the page can not be migrated. So try to |
| 660 | * free the metadata, so the page can be freed. |
| 661 | */ |
| 662 | if (!page->mapping) { |
| 663 | if (!PageAnon(page) && page_has_private(page)) { |
| 664 | /* |
| 665 | * Go direct to try_to_free_buffers() here because |
| 666 | * a) that's what try_to_release_page() would do anyway |
| 667 | * b) we may be under rcu_read_lock() here, so we can't |
| 668 | * use GFP_KERNEL which is what try_to_release_page() |
| 669 | * needs to be effective. |
| 670 | */ |
| 671 | try_to_free_buffers(page); |
| 672 | goto rcu_unlock; |
| 673 | } |
| 674 | goto skip_unmap; |
| 675 | } |
| 676 | |
| 677 | /* Establish migration ptes or remove ptes */ |
| 678 | try_to_unmap(page, 1); |
| 679 | |
| 680 | skip_unmap: |
| 681 | if (!page_mapped(page)) |
| 682 | rc = move_to_new_page(newpage, page); |
| 683 | |
| 684 | if (rc) |
| 685 | remove_migration_ptes(page, page); |
| 686 | rcu_unlock: |
| 687 | if (rcu_locked) |
| 688 | rcu_read_unlock(); |
| 689 | uncharge: |
| 690 | if (!charge) |
| 691 | mem_cgroup_end_migration(mem, page, newpage); |
| 692 | unlock: |
| 693 | unlock_page(page); |
| 694 | |
| 695 | if (rc != -EAGAIN) { |
| 696 | /* |
| 697 | * A page that has been migrated has all references |
| 698 | * removed and will be freed. A page that has not been |
| 699 | * migrated will have kepts its references and be |
| 700 | * restored. |
| 701 | */ |
| 702 | list_del(&page->lru); |
| 703 | dec_zone_page_state(page, NR_ISOLATED_ANON + |
| 704 | page_is_file_cache(page)); |
| 705 | putback_lru_page(page); |
| 706 | } |
| 707 | |
| 708 | move_newpage: |
| 709 | |
| 710 | /* |
| 711 | * Move the new page to the LRU. If migration was not successful |
| 712 | * then this will free the page. |
| 713 | */ |
| 714 | putback_lru_page(newpage); |
| 715 | |
| 716 | if (result) { |
| 717 | if (rc) |
| 718 | *result = rc; |
| 719 | else |
| 720 | *result = page_to_nid(newpage); |
| 721 | } |
| 722 | return rc; |
| 723 | } |
| 724 | |
| 725 | /* |
| 726 | * migrate_pages |
| 727 | * |
| 728 | * The function takes one list of pages to migrate and a function |
| 729 | * that determines from the page to be migrated and the private data |
| 730 | * the target of the move and allocates the page. |
| 731 | * |
| 732 | * The function returns after 10 attempts or if no pages |
| 733 | * are movable anymore because to has become empty |
| 734 | * or no retryable pages exist anymore. All pages will be |
| 735 | * returned to the LRU or freed. |
| 736 | * |
| 737 | * Return: Number of pages not migrated or error code. |
| 738 | */ |
| 739 | int migrate_pages(struct list_head *from, |
| 740 | new_page_t get_new_page, unsigned long private) |
| 741 | { |
| 742 | int retry = 1; |
| 743 | int nr_failed = 0; |
| 744 | int pass = 0; |
| 745 | struct page *page; |
| 746 | struct page *page2; |
| 747 | int swapwrite = current->flags & PF_SWAPWRITE; |
| 748 | int rc; |
| 749 | unsigned long flags; |
| 750 | |
| 751 | local_irq_save(flags); |
| 752 | list_for_each_entry(page, from, lru) |
| 753 | __inc_zone_page_state(page, NR_ISOLATED_ANON + |
| 754 | page_is_file_cache(page)); |
| 755 | local_irq_restore(flags); |
| 756 | |
| 757 | if (!swapwrite) |
| 758 | current->flags |= PF_SWAPWRITE; |
| 759 | |
| 760 | for(pass = 0; pass < 10 && retry; pass++) { |
| 761 | retry = 0; |
| 762 | |
| 763 | list_for_each_entry_safe(page, page2, from, lru) { |
| 764 | cond_resched(); |
| 765 | |
| 766 | rc = unmap_and_move(get_new_page, private, |
| 767 | page, pass > 2); |
| 768 | |
| 769 | switch(rc) { |
| 770 | case -ENOMEM: |
| 771 | goto out; |
| 772 | case -EAGAIN: |
| 773 | retry++; |
| 774 | break; |
| 775 | case 0: |
| 776 | break; |
| 777 | default: |
| 778 | /* Permanent failure */ |
| 779 | nr_failed++; |
| 780 | break; |
| 781 | } |
| 782 | } |
| 783 | } |
| 784 | rc = 0; |
| 785 | out: |
| 786 | if (!swapwrite) |
| 787 | current->flags &= ~PF_SWAPWRITE; |
| 788 | |
| 789 | putback_lru_pages(from); |
| 790 | |
| 791 | if (rc) |
| 792 | return rc; |
| 793 | |
| 794 | return nr_failed + retry; |
| 795 | } |
| 796 | |
| 797 | #ifdef CONFIG_NUMA |
| 798 | /* |
| 799 | * Move a list of individual pages |
| 800 | */ |
| 801 | struct page_to_node { |
| 802 | unsigned long addr; |
| 803 | struct page *page; |
| 804 | int node; |
| 805 | int status; |
| 806 | }; |
| 807 | |
| 808 | static struct page *new_page_node(struct page *p, unsigned long private, |
| 809 | int **result) |
| 810 | { |
| 811 | struct page_to_node *pm = (struct page_to_node *)private; |
| 812 | |
| 813 | while (pm->node != MAX_NUMNODES && pm->page != p) |
| 814 | pm++; |
| 815 | |
| 816 | if (pm->node == MAX_NUMNODES) |
| 817 | return NULL; |
| 818 | |
| 819 | *result = &pm->status; |
| 820 | |
| 821 | return alloc_pages_exact_node(pm->node, |
| 822 | GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); |
| 823 | } |
| 824 | |
| 825 | /* |
| 826 | * Move a set of pages as indicated in the pm array. The addr |
| 827 | * field must be set to the virtual address of the page to be moved |
| 828 | * and the node number must contain a valid target node. |
| 829 | * The pm array ends with node = MAX_NUMNODES. |
| 830 | */ |
| 831 | static int do_move_page_to_node_array(struct mm_struct *mm, |
| 832 | struct page_to_node *pm, |
| 833 | int migrate_all) |
| 834 | { |
| 835 | int err; |
| 836 | struct page_to_node *pp; |
| 837 | LIST_HEAD(pagelist); |
| 838 | |
| 839 | down_read(&mm->mmap_sem); |
| 840 | |
| 841 | /* |
| 842 | * Build a list of pages to migrate |
| 843 | */ |
| 844 | for (pp = pm; pp->node != MAX_NUMNODES; pp++) { |
| 845 | struct vm_area_struct *vma; |
| 846 | struct page *page; |
| 847 | |
| 848 | err = -EFAULT; |
| 849 | vma = find_vma(mm, pp->addr); |
| 850 | if (!vma || !vma_migratable(vma)) |
| 851 | goto set_status; |
| 852 | |
| 853 | page = follow_page(vma, pp->addr, FOLL_GET); |
| 854 | |
| 855 | err = PTR_ERR(page); |
| 856 | if (IS_ERR(page)) |
| 857 | goto set_status; |
| 858 | |
| 859 | err = -ENOENT; |
| 860 | if (!page) |
| 861 | goto set_status; |
| 862 | |
| 863 | if (PageReserved(page)) /* Check for zero page */ |
| 864 | goto put_and_set; |
| 865 | |
| 866 | pp->page = page; |
| 867 | err = page_to_nid(page); |
| 868 | |
| 869 | if (err == pp->node) |
| 870 | /* |
| 871 | * Node already in the right place |
| 872 | */ |
| 873 | goto put_and_set; |
| 874 | |
| 875 | err = -EACCES; |
| 876 | if (page_mapcount(page) > 1 && |
| 877 | !migrate_all) |
| 878 | goto put_and_set; |
| 879 | |
| 880 | err = isolate_lru_page(page); |
| 881 | if (!err) |
| 882 | list_add_tail(&page->lru, &pagelist); |
| 883 | put_and_set: |
| 884 | /* |
| 885 | * Either remove the duplicate refcount from |
| 886 | * isolate_lru_page() or drop the page ref if it was |
| 887 | * not isolated. |
| 888 | */ |
| 889 | put_page(page); |
| 890 | set_status: |
| 891 | pp->status = err; |
| 892 | } |
| 893 | |
| 894 | err = 0; |
| 895 | if (!list_empty(&pagelist)) |
| 896 | err = migrate_pages(&pagelist, new_page_node, |
| 897 | (unsigned long)pm); |
| 898 | |
| 899 | up_read(&mm->mmap_sem); |
| 900 | return err; |
| 901 | } |
| 902 | |
| 903 | /* |
| 904 | * Migrate an array of page address onto an array of nodes and fill |
| 905 | * the corresponding array of status. |
| 906 | */ |
| 907 | static int do_pages_move(struct mm_struct *mm, struct task_struct *task, |
| 908 | unsigned long nr_pages, |
| 909 | const void __user * __user *pages, |
| 910 | const int __user *nodes, |
| 911 | int __user *status, int flags) |
| 912 | { |
| 913 | struct page_to_node *pm; |
| 914 | nodemask_t task_nodes; |
| 915 | unsigned long chunk_nr_pages; |
| 916 | unsigned long chunk_start; |
| 917 | int err; |
| 918 | |
| 919 | task_nodes = cpuset_mems_allowed(task); |
| 920 | |
| 921 | err = -ENOMEM; |
| 922 | pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); |
| 923 | if (!pm) |
| 924 | goto out; |
| 925 | |
| 926 | migrate_prep(); |
| 927 | |
| 928 | /* |
| 929 | * Store a chunk of page_to_node array in a page, |
| 930 | * but keep the last one as a marker |
| 931 | */ |
| 932 | chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; |
| 933 | |
| 934 | for (chunk_start = 0; |
| 935 | chunk_start < nr_pages; |
| 936 | chunk_start += chunk_nr_pages) { |
| 937 | int j; |
| 938 | |
| 939 | if (chunk_start + chunk_nr_pages > nr_pages) |
| 940 | chunk_nr_pages = nr_pages - chunk_start; |
| 941 | |
| 942 | /* fill the chunk pm with addrs and nodes from user-space */ |
| 943 | for (j = 0; j < chunk_nr_pages; j++) { |
| 944 | const void __user *p; |
| 945 | int node; |
| 946 | |
| 947 | err = -EFAULT; |
| 948 | if (get_user(p, pages + j + chunk_start)) |
| 949 | goto out_pm; |
| 950 | pm[j].addr = (unsigned long) p; |
| 951 | |
| 952 | if (get_user(node, nodes + j + chunk_start)) |
| 953 | goto out_pm; |
| 954 | |
| 955 | err = -ENODEV; |
| 956 | if (!node_state(node, N_HIGH_MEMORY)) |
| 957 | goto out_pm; |
| 958 | |
| 959 | err = -EACCES; |
| 960 | if (!node_isset(node, task_nodes)) |
| 961 | goto out_pm; |
| 962 | |
| 963 | pm[j].node = node; |
| 964 | } |
| 965 | |
| 966 | /* End marker for this chunk */ |
| 967 | pm[chunk_nr_pages].node = MAX_NUMNODES; |
| 968 | |
| 969 | /* Migrate this chunk */ |
| 970 | err = do_move_page_to_node_array(mm, pm, |
| 971 | flags & MPOL_MF_MOVE_ALL); |
| 972 | if (err < 0) |
| 973 | goto out_pm; |
| 974 | |
| 975 | /* Return status information */ |
| 976 | for (j = 0; j < chunk_nr_pages; j++) |
| 977 | if (put_user(pm[j].status, status + j + chunk_start)) { |
| 978 | err = -EFAULT; |
| 979 | goto out_pm; |
| 980 | } |
| 981 | } |
| 982 | err = 0; |
| 983 | |
| 984 | out_pm: |
| 985 | free_page((unsigned long)pm); |
| 986 | out: |
| 987 | return err; |
| 988 | } |
| 989 | |
| 990 | /* |
| 991 | * Determine the nodes of an array of pages and store it in an array of status. |
| 992 | */ |
| 993 | static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, |
| 994 | const void __user **pages, int *status) |
| 995 | { |
| 996 | unsigned long i; |
| 997 | |
| 998 | down_read(&mm->mmap_sem); |
| 999 | |
| 1000 | for (i = 0; i < nr_pages; i++) { |
| 1001 | unsigned long addr = (unsigned long)(*pages); |
| 1002 | struct vm_area_struct *vma; |
| 1003 | struct page *page; |
| 1004 | int err = -EFAULT; |
| 1005 | |
| 1006 | vma = find_vma(mm, addr); |
| 1007 | if (!vma) |
| 1008 | goto set_status; |
| 1009 | |
| 1010 | page = follow_page(vma, addr, 0); |
| 1011 | |
| 1012 | err = PTR_ERR(page); |
| 1013 | if (IS_ERR(page)) |
| 1014 | goto set_status; |
| 1015 | |
| 1016 | err = -ENOENT; |
| 1017 | /* Use PageReserved to check for zero page */ |
| 1018 | if (!page || PageReserved(page)) |
| 1019 | goto set_status; |
| 1020 | |
| 1021 | err = page_to_nid(page); |
| 1022 | set_status: |
| 1023 | *status = err; |
| 1024 | |
| 1025 | pages++; |
| 1026 | status++; |
| 1027 | } |
| 1028 | |
| 1029 | up_read(&mm->mmap_sem); |
| 1030 | } |
| 1031 | |
| 1032 | /* |
| 1033 | * Determine the nodes of a user array of pages and store it in |
| 1034 | * a user array of status. |
| 1035 | */ |
| 1036 | static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, |
| 1037 | const void __user * __user *pages, |
| 1038 | int __user *status) |
| 1039 | { |
| 1040 | #define DO_PAGES_STAT_CHUNK_NR 16 |
| 1041 | const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; |
| 1042 | int chunk_status[DO_PAGES_STAT_CHUNK_NR]; |
| 1043 | unsigned long i, chunk_nr = DO_PAGES_STAT_CHUNK_NR; |
| 1044 | int err; |
| 1045 | |
| 1046 | for (i = 0; i < nr_pages; i += chunk_nr) { |
| 1047 | if (chunk_nr + i > nr_pages) |
| 1048 | chunk_nr = nr_pages - i; |
| 1049 | |
| 1050 | err = copy_from_user(chunk_pages, &pages[i], |
| 1051 | chunk_nr * sizeof(*chunk_pages)); |
| 1052 | if (err) { |
| 1053 | err = -EFAULT; |
| 1054 | goto out; |
| 1055 | } |
| 1056 | |
| 1057 | do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); |
| 1058 | |
| 1059 | err = copy_to_user(&status[i], chunk_status, |
| 1060 | chunk_nr * sizeof(*chunk_status)); |
| 1061 | if (err) { |
| 1062 | err = -EFAULT; |
| 1063 | goto out; |
| 1064 | } |
| 1065 | } |
| 1066 | err = 0; |
| 1067 | |
| 1068 | out: |
| 1069 | return err; |
| 1070 | } |
| 1071 | |
| 1072 | /* |
| 1073 | * Move a list of pages in the address space of the currently executing |
| 1074 | * process. |
| 1075 | */ |
| 1076 | SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, |
| 1077 | const void __user * __user *, pages, |
| 1078 | const int __user *, nodes, |
| 1079 | int __user *, status, int, flags) |
| 1080 | { |
| 1081 | const struct cred *cred = current_cred(), *tcred; |
| 1082 | struct task_struct *task; |
| 1083 | struct mm_struct *mm; |
| 1084 | int err; |
| 1085 | |
| 1086 | /* Check flags */ |
| 1087 | if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) |
| 1088 | return -EINVAL; |
| 1089 | |
| 1090 | if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) |
| 1091 | return -EPERM; |
| 1092 | |
| 1093 | /* Find the mm_struct */ |
| 1094 | read_lock(&tasklist_lock); |
| 1095 | task = pid ? find_task_by_vpid(pid) : current; |
| 1096 | if (!task) { |
| 1097 | read_unlock(&tasklist_lock); |
| 1098 | return -ESRCH; |
| 1099 | } |
| 1100 | mm = get_task_mm(task); |
| 1101 | read_unlock(&tasklist_lock); |
| 1102 | |
| 1103 | if (!mm) |
| 1104 | return -EINVAL; |
| 1105 | |
| 1106 | /* |
| 1107 | * Check if this process has the right to modify the specified |
| 1108 | * process. The right exists if the process has administrative |
| 1109 | * capabilities, superuser privileges or the same |
| 1110 | * userid as the target process. |
| 1111 | */ |
| 1112 | rcu_read_lock(); |
| 1113 | tcred = __task_cred(task); |
| 1114 | if (cred->euid != tcred->suid && cred->euid != tcred->uid && |
| 1115 | cred->uid != tcred->suid && cred->uid != tcred->uid && |
| 1116 | !capable(CAP_SYS_NICE)) { |
| 1117 | rcu_read_unlock(); |
| 1118 | err = -EPERM; |
| 1119 | goto out; |
| 1120 | } |
| 1121 | rcu_read_unlock(); |
| 1122 | |
| 1123 | err = security_task_movememory(task); |
| 1124 | if (err) |
| 1125 | goto out; |
| 1126 | |
| 1127 | if (nodes) { |
| 1128 | err = do_pages_move(mm, task, nr_pages, pages, nodes, status, |
| 1129 | flags); |
| 1130 | } else { |
| 1131 | err = do_pages_stat(mm, nr_pages, pages, status); |
| 1132 | } |
| 1133 | |
| 1134 | out: |
| 1135 | mmput(mm); |
| 1136 | return err; |
| 1137 | } |
| 1138 | |
| 1139 | /* |
| 1140 | * Call migration functions in the vma_ops that may prepare |
| 1141 | * memory in a vm for migration. migration functions may perform |
| 1142 | * the migration for vmas that do not have an underlying page struct. |
| 1143 | */ |
| 1144 | int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, |
| 1145 | const nodemask_t *from, unsigned long flags) |
| 1146 | { |
| 1147 | struct vm_area_struct *vma; |
| 1148 | int err = 0; |
| 1149 | |
| 1150 | for (vma = mm->mmap; vma && !err; vma = vma->vm_next) { |
| 1151 | if (vma->vm_ops && vma->vm_ops->migrate) { |
| 1152 | err = vma->vm_ops->migrate(vma, to, from, flags); |
| 1153 | if (err) |
| 1154 | break; |
| 1155 | } |
| 1156 | } |
| 1157 | return err; |
| 1158 | } |
| 1159 | #endif |