| 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 <clameter@sgi.com> |
| 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 | |
| 34 | #include "internal.h" |
| 35 | |
| 36 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
| 37 | |
| 38 | /* |
| 39 | * Isolate one page from the LRU lists. If successful put it onto |
| 40 | * the indicated list with elevated page count. |
| 41 | * |
| 42 | * Result: |
| 43 | * -EBUSY: page not on LRU list |
| 44 | * 0: page removed from LRU list and added to the specified list. |
| 45 | */ |
| 46 | int isolate_lru_page(struct page *page, struct list_head *pagelist) |
| 47 | { |
| 48 | int ret = -EBUSY; |
| 49 | |
| 50 | if (PageLRU(page)) { |
| 51 | struct zone *zone = page_zone(page); |
| 52 | |
| 53 | spin_lock_irq(&zone->lru_lock); |
| 54 | if (PageLRU(page) && get_page_unless_zero(page)) { |
| 55 | ret = 0; |
| 56 | ClearPageLRU(page); |
| 57 | if (PageActive(page)) |
| 58 | del_page_from_active_list(zone, page); |
| 59 | else |
| 60 | del_page_from_inactive_list(zone, page); |
| 61 | list_add_tail(&page->lru, pagelist); |
| 62 | } |
| 63 | spin_unlock_irq(&zone->lru_lock); |
| 64 | } |
| 65 | return ret; |
| 66 | } |
| 67 | |
| 68 | /* |
| 69 | * migrate_prep() needs to be called before we start compiling a list of pages |
| 70 | * to be migrated using isolate_lru_page(). |
| 71 | */ |
| 72 | int migrate_prep(void) |
| 73 | { |
| 74 | /* |
| 75 | * Clear the LRU lists so pages can be isolated. |
| 76 | * Note that pages may be moved off the LRU after we have |
| 77 | * drained them. Those pages will fail to migrate like other |
| 78 | * pages that may be busy. |
| 79 | */ |
| 80 | lru_add_drain_all(); |
| 81 | |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | static inline void move_to_lru(struct page *page) |
| 86 | { |
| 87 | if (PageActive(page)) { |
| 88 | /* |
| 89 | * lru_cache_add_active checks that |
| 90 | * the PG_active bit is off. |
| 91 | */ |
| 92 | ClearPageActive(page); |
| 93 | lru_cache_add_active(page); |
| 94 | } else { |
| 95 | lru_cache_add(page); |
| 96 | } |
| 97 | put_page(page); |
| 98 | } |
| 99 | |
| 100 | /* |
| 101 | * Add isolated pages on the list back to the LRU. |
| 102 | * |
| 103 | * returns the number of pages put back. |
| 104 | */ |
| 105 | int putback_lru_pages(struct list_head *l) |
| 106 | { |
| 107 | struct page *page; |
| 108 | struct page *page2; |
| 109 | int count = 0; |
| 110 | |
| 111 | list_for_each_entry_safe(page, page2, l, lru) { |
| 112 | list_del(&page->lru); |
| 113 | move_to_lru(page); |
| 114 | count++; |
| 115 | } |
| 116 | return count; |
| 117 | } |
| 118 | |
| 119 | /* |
| 120 | * Restore a potential migration pte to a working pte entry |
| 121 | */ |
| 122 | static void remove_migration_pte(struct vm_area_struct *vma, |
| 123 | struct page *old, struct page *new) |
| 124 | { |
| 125 | struct mm_struct *mm = vma->vm_mm; |
| 126 | swp_entry_t entry; |
| 127 | pgd_t *pgd; |
| 128 | pud_t *pud; |
| 129 | pmd_t *pmd; |
| 130 | pte_t *ptep, pte; |
| 131 | spinlock_t *ptl; |
| 132 | unsigned long addr = page_address_in_vma(new, vma); |
| 133 | |
| 134 | if (addr == -EFAULT) |
| 135 | return; |
| 136 | |
| 137 | pgd = pgd_offset(mm, addr); |
| 138 | if (!pgd_present(*pgd)) |
| 139 | return; |
| 140 | |
| 141 | pud = pud_offset(pgd, addr); |
| 142 | if (!pud_present(*pud)) |
| 143 | return; |
| 144 | |
| 145 | pmd = pmd_offset(pud, addr); |
| 146 | if (!pmd_present(*pmd)) |
| 147 | return; |
| 148 | |
| 149 | ptep = pte_offset_map(pmd, addr); |
| 150 | |
| 151 | if (!is_swap_pte(*ptep)) { |
| 152 | pte_unmap(ptep); |
| 153 | return; |
| 154 | } |
| 155 | |
| 156 | ptl = pte_lockptr(mm, pmd); |
| 157 | spin_lock(ptl); |
| 158 | pte = *ptep; |
| 159 | if (!is_swap_pte(pte)) |
| 160 | goto out; |
| 161 | |
| 162 | entry = pte_to_swp_entry(pte); |
| 163 | |
| 164 | if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) |
| 165 | goto out; |
| 166 | |
| 167 | /* |
| 168 | * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge. |
| 169 | * Failure is not an option here: we're now expected to remove every |
| 170 | * migration pte, and will cause crashes otherwise. Normally this |
| 171 | * is not an issue: mem_cgroup_prepare_migration bumped up the old |
| 172 | * page_cgroup count for safety, that's now attached to the new page, |
| 173 | * so this charge should just be another incrementation of the count, |
| 174 | * to keep in balance with rmap.c's mem_cgroup_uncharging. But if |
| 175 | * there's been a force_empty, those reference counts may no longer |
| 176 | * be reliable, and this charge can actually fail: oh well, we don't |
| 177 | * make the situation any worse by proceeding as if it had succeeded. |
| 178 | */ |
| 179 | mem_cgroup_charge(new, mm, GFP_ATOMIC); |
| 180 | |
| 181 | get_page(new); |
| 182 | pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); |
| 183 | if (is_write_migration_entry(entry)) |
| 184 | pte = pte_mkwrite(pte); |
| 185 | flush_cache_page(vma, addr, pte_pfn(pte)); |
| 186 | set_pte_at(mm, addr, ptep, pte); |
| 187 | |
| 188 | if (PageAnon(new)) |
| 189 | page_add_anon_rmap(new, vma, addr); |
| 190 | else |
| 191 | page_add_file_rmap(new); |
| 192 | |
| 193 | /* No need to invalidate - it was non-present before */ |
| 194 | update_mmu_cache(vma, addr, pte); |
| 195 | |
| 196 | out: |
| 197 | pte_unmap_unlock(ptep, ptl); |
| 198 | } |
| 199 | |
| 200 | /* |
| 201 | * Note that remove_file_migration_ptes will only work on regular mappings, |
| 202 | * Nonlinear mappings do not use migration entries. |
| 203 | */ |
| 204 | static void remove_file_migration_ptes(struct page *old, struct page *new) |
| 205 | { |
| 206 | struct vm_area_struct *vma; |
| 207 | struct address_space *mapping = page_mapping(new); |
| 208 | struct prio_tree_iter iter; |
| 209 | pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| 210 | |
| 211 | if (!mapping) |
| 212 | return; |
| 213 | |
| 214 | spin_lock(&mapping->i_mmap_lock); |
| 215 | |
| 216 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) |
| 217 | remove_migration_pte(vma, old, new); |
| 218 | |
| 219 | spin_unlock(&mapping->i_mmap_lock); |
| 220 | } |
| 221 | |
| 222 | /* |
| 223 | * Must hold mmap_sem lock on at least one of the vmas containing |
| 224 | * the page so that the anon_vma cannot vanish. |
| 225 | */ |
| 226 | static void remove_anon_migration_ptes(struct page *old, struct page *new) |
| 227 | { |
| 228 | struct anon_vma *anon_vma; |
| 229 | struct vm_area_struct *vma; |
| 230 | unsigned long mapping; |
| 231 | |
| 232 | mapping = (unsigned long)new->mapping; |
| 233 | |
| 234 | if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0) |
| 235 | return; |
| 236 | |
| 237 | /* |
| 238 | * We hold the mmap_sem lock. So no need to call page_lock_anon_vma. |
| 239 | */ |
| 240 | anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON); |
| 241 | spin_lock(&anon_vma->lock); |
| 242 | |
| 243 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) |
| 244 | remove_migration_pte(vma, old, new); |
| 245 | |
| 246 | spin_unlock(&anon_vma->lock); |
| 247 | } |
| 248 | |
| 249 | /* |
| 250 | * Get rid of all migration entries and replace them by |
| 251 | * references to the indicated page. |
| 252 | */ |
| 253 | static void remove_migration_ptes(struct page *old, struct page *new) |
| 254 | { |
| 255 | if (PageAnon(new)) |
| 256 | remove_anon_migration_ptes(old, new); |
| 257 | else |
| 258 | remove_file_migration_ptes(old, new); |
| 259 | } |
| 260 | |
| 261 | /* |
| 262 | * Something used the pte of a page under migration. We need to |
| 263 | * get to the page and wait until migration is finished. |
| 264 | * When we return from this function the fault will be retried. |
| 265 | * |
| 266 | * This function is called from do_swap_page(). |
| 267 | */ |
| 268 | void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, |
| 269 | unsigned long address) |
| 270 | { |
| 271 | pte_t *ptep, pte; |
| 272 | spinlock_t *ptl; |
| 273 | swp_entry_t entry; |
| 274 | struct page *page; |
| 275 | |
| 276 | ptep = pte_offset_map_lock(mm, pmd, address, &ptl); |
| 277 | pte = *ptep; |
| 278 | if (!is_swap_pte(pte)) |
| 279 | goto out; |
| 280 | |
| 281 | entry = pte_to_swp_entry(pte); |
| 282 | if (!is_migration_entry(entry)) |
| 283 | goto out; |
| 284 | |
| 285 | page = migration_entry_to_page(entry); |
| 286 | |
| 287 | get_page(page); |
| 288 | pte_unmap_unlock(ptep, ptl); |
| 289 | wait_on_page_locked(page); |
| 290 | put_page(page); |
| 291 | return; |
| 292 | out: |
| 293 | pte_unmap_unlock(ptep, ptl); |
| 294 | } |
| 295 | |
| 296 | /* |
| 297 | * Replace the page in the mapping. |
| 298 | * |
| 299 | * The number of remaining references must be: |
| 300 | * 1 for anonymous pages without a mapping |
| 301 | * 2 for pages with a mapping |
| 302 | * 3 for pages with a mapping and PagePrivate set. |
| 303 | */ |
| 304 | static int migrate_page_move_mapping(struct address_space *mapping, |
| 305 | struct page *newpage, struct page *page) |
| 306 | { |
| 307 | void **pslot; |
| 308 | |
| 309 | if (!mapping) { |
| 310 | /* Anonymous page without mapping */ |
| 311 | if (page_count(page) != 1) |
| 312 | return -EAGAIN; |
| 313 | return 0; |
| 314 | } |
| 315 | |
| 316 | write_lock_irq(&mapping->tree_lock); |
| 317 | |
| 318 | pslot = radix_tree_lookup_slot(&mapping->page_tree, |
| 319 | page_index(page)); |
| 320 | |
| 321 | if (page_count(page) != 2 + !!PagePrivate(page) || |
| 322 | (struct page *)radix_tree_deref_slot(pslot) != page) { |
| 323 | write_unlock_irq(&mapping->tree_lock); |
| 324 | return -EAGAIN; |
| 325 | } |
| 326 | |
| 327 | /* |
| 328 | * Now we know that no one else is looking at the page. |
| 329 | */ |
| 330 | get_page(newpage); /* add cache reference */ |
| 331 | #ifdef CONFIG_SWAP |
| 332 | if (PageSwapCache(page)) { |
| 333 | SetPageSwapCache(newpage); |
| 334 | set_page_private(newpage, page_private(page)); |
| 335 | } |
| 336 | #endif |
| 337 | |
| 338 | radix_tree_replace_slot(pslot, newpage); |
| 339 | |
| 340 | /* |
| 341 | * Drop cache reference from old page. |
| 342 | * We know this isn't the last reference. |
| 343 | */ |
| 344 | __put_page(page); |
| 345 | |
| 346 | /* |
| 347 | * If moved to a different zone then also account |
| 348 | * the page for that zone. Other VM counters will be |
| 349 | * taken care of when we establish references to the |
| 350 | * new page and drop references to the old page. |
| 351 | * |
| 352 | * Note that anonymous pages are accounted for |
| 353 | * via NR_FILE_PAGES and NR_ANON_PAGES if they |
| 354 | * are mapped to swap space. |
| 355 | */ |
| 356 | __dec_zone_page_state(page, NR_FILE_PAGES); |
| 357 | __inc_zone_page_state(newpage, NR_FILE_PAGES); |
| 358 | |
| 359 | write_unlock_irq(&mapping->tree_lock); |
| 360 | |
| 361 | return 0; |
| 362 | } |
| 363 | |
| 364 | /* |
| 365 | * Copy the page to its new location |
| 366 | */ |
| 367 | static void migrate_page_copy(struct page *newpage, struct page *page) |
| 368 | { |
| 369 | copy_highpage(newpage, page); |
| 370 | |
| 371 | if (PageError(page)) |
| 372 | SetPageError(newpage); |
| 373 | if (PageReferenced(page)) |
| 374 | SetPageReferenced(newpage); |
| 375 | if (PageUptodate(page)) |
| 376 | SetPageUptodate(newpage); |
| 377 | if (PageActive(page)) |
| 378 | SetPageActive(newpage); |
| 379 | if (PageChecked(page)) |
| 380 | SetPageChecked(newpage); |
| 381 | if (PageMappedToDisk(page)) |
| 382 | SetPageMappedToDisk(newpage); |
| 383 | |
| 384 | if (PageDirty(page)) { |
| 385 | clear_page_dirty_for_io(page); |
| 386 | set_page_dirty(newpage); |
| 387 | } |
| 388 | |
| 389 | #ifdef CONFIG_SWAP |
| 390 | ClearPageSwapCache(page); |
| 391 | #endif |
| 392 | ClearPageActive(page); |
| 393 | ClearPagePrivate(page); |
| 394 | set_page_private(page, 0); |
| 395 | page->mapping = NULL; |
| 396 | |
| 397 | /* |
| 398 | * If any waiters have accumulated on the new page then |
| 399 | * wake them up. |
| 400 | */ |
| 401 | if (PageWriteback(newpage)) |
| 402 | end_page_writeback(newpage); |
| 403 | } |
| 404 | |
| 405 | /************************************************************ |
| 406 | * Migration functions |
| 407 | ***********************************************************/ |
| 408 | |
| 409 | /* Always fail migration. Used for mappings that are not movable */ |
| 410 | int fail_migrate_page(struct address_space *mapping, |
| 411 | struct page *newpage, struct page *page) |
| 412 | { |
| 413 | return -EIO; |
| 414 | } |
| 415 | EXPORT_SYMBOL(fail_migrate_page); |
| 416 | |
| 417 | /* |
| 418 | * Common logic to directly migrate a single page suitable for |
| 419 | * pages that do not use PagePrivate. |
| 420 | * |
| 421 | * Pages are locked upon entry and exit. |
| 422 | */ |
| 423 | int migrate_page(struct address_space *mapping, |
| 424 | struct page *newpage, struct page *page) |
| 425 | { |
| 426 | int rc; |
| 427 | |
| 428 | BUG_ON(PageWriteback(page)); /* Writeback must be complete */ |
| 429 | |
| 430 | rc = migrate_page_move_mapping(mapping, newpage, page); |
| 431 | |
| 432 | if (rc) |
| 433 | return rc; |
| 434 | |
| 435 | migrate_page_copy(newpage, page); |
| 436 | return 0; |
| 437 | } |
| 438 | EXPORT_SYMBOL(migrate_page); |
| 439 | |
| 440 | #ifdef CONFIG_BLOCK |
| 441 | /* |
| 442 | * Migration function for pages with buffers. This function can only be used |
| 443 | * if the underlying filesystem guarantees that no other references to "page" |
| 444 | * exist. |
| 445 | */ |
| 446 | int buffer_migrate_page(struct address_space *mapping, |
| 447 | struct page *newpage, struct page *page) |
| 448 | { |
| 449 | struct buffer_head *bh, *head; |
| 450 | int rc; |
| 451 | |
| 452 | if (!page_has_buffers(page)) |
| 453 | return migrate_page(mapping, newpage, page); |
| 454 | |
| 455 | head = page_buffers(page); |
| 456 | |
| 457 | rc = migrate_page_move_mapping(mapping, newpage, page); |
| 458 | |
| 459 | if (rc) |
| 460 | return rc; |
| 461 | |
| 462 | bh = head; |
| 463 | do { |
| 464 | get_bh(bh); |
| 465 | lock_buffer(bh); |
| 466 | bh = bh->b_this_page; |
| 467 | |
| 468 | } while (bh != head); |
| 469 | |
| 470 | ClearPagePrivate(page); |
| 471 | set_page_private(newpage, page_private(page)); |
| 472 | set_page_private(page, 0); |
| 473 | put_page(page); |
| 474 | get_page(newpage); |
| 475 | |
| 476 | bh = head; |
| 477 | do { |
| 478 | set_bh_page(bh, newpage, bh_offset(bh)); |
| 479 | bh = bh->b_this_page; |
| 480 | |
| 481 | } while (bh != head); |
| 482 | |
| 483 | SetPagePrivate(newpage); |
| 484 | |
| 485 | migrate_page_copy(newpage, page); |
| 486 | |
| 487 | bh = head; |
| 488 | do { |
| 489 | unlock_buffer(bh); |
| 490 | put_bh(bh); |
| 491 | bh = bh->b_this_page; |
| 492 | |
| 493 | } while (bh != head); |
| 494 | |
| 495 | return 0; |
| 496 | } |
| 497 | EXPORT_SYMBOL(buffer_migrate_page); |
| 498 | #endif |
| 499 | |
| 500 | /* |
| 501 | * Writeback a page to clean the dirty state |
| 502 | */ |
| 503 | static int writeout(struct address_space *mapping, struct page *page) |
| 504 | { |
| 505 | struct writeback_control wbc = { |
| 506 | .sync_mode = WB_SYNC_NONE, |
| 507 | .nr_to_write = 1, |
| 508 | .range_start = 0, |
| 509 | .range_end = LLONG_MAX, |
| 510 | .nonblocking = 1, |
| 511 | .for_reclaim = 1 |
| 512 | }; |
| 513 | int rc; |
| 514 | |
| 515 | if (!mapping->a_ops->writepage) |
| 516 | /* No write method for the address space */ |
| 517 | return -EINVAL; |
| 518 | |
| 519 | if (!clear_page_dirty_for_io(page)) |
| 520 | /* Someone else already triggered a write */ |
| 521 | return -EAGAIN; |
| 522 | |
| 523 | /* |
| 524 | * A dirty page may imply that the underlying filesystem has |
| 525 | * the page on some queue. So the page must be clean for |
| 526 | * migration. Writeout may mean we loose the lock and the |
| 527 | * page state is no longer what we checked for earlier. |
| 528 | * At this point we know that the migration attempt cannot |
| 529 | * be successful. |
| 530 | */ |
| 531 | remove_migration_ptes(page, page); |
| 532 | |
| 533 | rc = mapping->a_ops->writepage(page, &wbc); |
| 534 | if (rc < 0) |
| 535 | /* I/O Error writing */ |
| 536 | return -EIO; |
| 537 | |
| 538 | if (rc != AOP_WRITEPAGE_ACTIVATE) |
| 539 | /* unlocked. Relock */ |
| 540 | lock_page(page); |
| 541 | |
| 542 | return -EAGAIN; |
| 543 | } |
| 544 | |
| 545 | /* |
| 546 | * Default handling if a filesystem does not provide a migration function. |
| 547 | */ |
| 548 | static int fallback_migrate_page(struct address_space *mapping, |
| 549 | struct page *newpage, struct page *page) |
| 550 | { |
| 551 | if (PageDirty(page)) |
| 552 | return writeout(mapping, page); |
| 553 | |
| 554 | /* |
| 555 | * Buffers may be managed in a filesystem specific way. |
| 556 | * We must have no buffers or drop them. |
| 557 | */ |
| 558 | if (PagePrivate(page) && |
| 559 | !try_to_release_page(page, GFP_KERNEL)) |
| 560 | return -EAGAIN; |
| 561 | |
| 562 | return migrate_page(mapping, newpage, page); |
| 563 | } |
| 564 | |
| 565 | /* |
| 566 | * Move a page to a newly allocated page |
| 567 | * The page is locked and all ptes have been successfully removed. |
| 568 | * |
| 569 | * The new page will have replaced the old page if this function |
| 570 | * is successful. |
| 571 | */ |
| 572 | static int move_to_new_page(struct page *newpage, struct page *page) |
| 573 | { |
| 574 | struct address_space *mapping; |
| 575 | int rc; |
| 576 | |
| 577 | /* |
| 578 | * Block others from accessing the page when we get around to |
| 579 | * establishing additional references. We are the only one |
| 580 | * holding a reference to the new page at this point. |
| 581 | */ |
| 582 | if (TestSetPageLocked(newpage)) |
| 583 | BUG(); |
| 584 | |
| 585 | /* Prepare mapping for the new page.*/ |
| 586 | newpage->index = page->index; |
| 587 | newpage->mapping = page->mapping; |
| 588 | |
| 589 | mapping = page_mapping(page); |
| 590 | if (!mapping) |
| 591 | rc = migrate_page(mapping, newpage, page); |
| 592 | else if (mapping->a_ops->migratepage) |
| 593 | /* |
| 594 | * Most pages have a mapping and most filesystems |
| 595 | * should provide a migration function. Anonymous |
| 596 | * pages are part of swap space which also has its |
| 597 | * own migration function. This is the most common |
| 598 | * path for page migration. |
| 599 | */ |
| 600 | rc = mapping->a_ops->migratepage(mapping, |
| 601 | newpage, page); |
| 602 | else |
| 603 | rc = fallback_migrate_page(mapping, newpage, page); |
| 604 | |
| 605 | if (!rc) { |
| 606 | mem_cgroup_page_migration(page, newpage); |
| 607 | remove_migration_ptes(page, newpage); |
| 608 | } else |
| 609 | newpage->mapping = NULL; |
| 610 | |
| 611 | unlock_page(newpage); |
| 612 | |
| 613 | return rc; |
| 614 | } |
| 615 | |
| 616 | /* |
| 617 | * Obtain the lock on page, remove all ptes and migrate the page |
| 618 | * to the newly allocated page in newpage. |
| 619 | */ |
| 620 | static int unmap_and_move(new_page_t get_new_page, unsigned long private, |
| 621 | struct page *page, int force) |
| 622 | { |
| 623 | int rc = 0; |
| 624 | int *result = NULL; |
| 625 | struct page *newpage = get_new_page(page, private, &result); |
| 626 | int rcu_locked = 0; |
| 627 | int charge = 0; |
| 628 | |
| 629 | if (!newpage) |
| 630 | return -ENOMEM; |
| 631 | |
| 632 | if (page_count(page) == 1) |
| 633 | /* page was freed from under us. So we are done. */ |
| 634 | goto move_newpage; |
| 635 | |
| 636 | rc = -EAGAIN; |
| 637 | if (TestSetPageLocked(page)) { |
| 638 | if (!force) |
| 639 | goto move_newpage; |
| 640 | lock_page(page); |
| 641 | } |
| 642 | |
| 643 | if (PageWriteback(page)) { |
| 644 | if (!force) |
| 645 | goto unlock; |
| 646 | wait_on_page_writeback(page); |
| 647 | } |
| 648 | /* |
| 649 | * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, |
| 650 | * we cannot notice that anon_vma is freed while we migrates a page. |
| 651 | * This rcu_read_lock() delays freeing anon_vma pointer until the end |
| 652 | * of migration. File cache pages are no problem because of page_lock() |
| 653 | * File Caches may use write_page() or lock_page() in migration, then, |
| 654 | * just care Anon page here. |
| 655 | */ |
| 656 | if (PageAnon(page)) { |
| 657 | rcu_read_lock(); |
| 658 | rcu_locked = 1; |
| 659 | } |
| 660 | |
| 661 | /* |
| 662 | * Corner case handling: |
| 663 | * 1. When a new swap-cache page is read into, it is added to the LRU |
| 664 | * and treated as swapcache but it has no rmap yet. |
| 665 | * Calling try_to_unmap() against a page->mapping==NULL page will |
| 666 | * trigger a BUG. So handle it here. |
| 667 | * 2. An orphaned page (see truncate_complete_page) might have |
| 668 | * fs-private metadata. The page can be picked up due to memory |
| 669 | * offlining. Everywhere else except page reclaim, the page is |
| 670 | * invisible to the vm, so the page can not be migrated. So try to |
| 671 | * free the metadata, so the page can be freed. |
| 672 | */ |
| 673 | if (!page->mapping) { |
| 674 | if (!PageAnon(page) && PagePrivate(page)) { |
| 675 | /* |
| 676 | * Go direct to try_to_free_buffers() here because |
| 677 | * a) that's what try_to_release_page() would do anyway |
| 678 | * b) we may be under rcu_read_lock() here, so we can't |
| 679 | * use GFP_KERNEL which is what try_to_release_page() |
| 680 | * needs to be effective. |
| 681 | */ |
| 682 | try_to_free_buffers(page); |
| 683 | } |
| 684 | goto rcu_unlock; |
| 685 | } |
| 686 | |
| 687 | charge = mem_cgroup_prepare_migration(page); |
| 688 | /* Establish migration ptes or remove ptes */ |
| 689 | try_to_unmap(page, 1); |
| 690 | |
| 691 | if (!page_mapped(page)) |
| 692 | rc = move_to_new_page(newpage, page); |
| 693 | |
| 694 | if (rc) { |
| 695 | remove_migration_ptes(page, page); |
| 696 | if (charge) |
| 697 | mem_cgroup_end_migration(page); |
| 698 | } else if (charge) |
| 699 | mem_cgroup_end_migration(newpage); |
| 700 | rcu_unlock: |
| 701 | if (rcu_locked) |
| 702 | rcu_read_unlock(); |
| 703 | |
| 704 | unlock: |
| 705 | |
| 706 | unlock_page(page); |
| 707 | |
| 708 | if (rc != -EAGAIN) { |
| 709 | /* |
| 710 | * A page that has been migrated has all references |
| 711 | * removed and will be freed. A page that has not been |
| 712 | * migrated will have kepts its references and be |
| 713 | * restored. |
| 714 | */ |
| 715 | list_del(&page->lru); |
| 716 | move_to_lru(page); |
| 717 | } |
| 718 | |
| 719 | move_newpage: |
| 720 | /* |
| 721 | * Move the new page to the LRU. If migration was not successful |
| 722 | * then this will free the page. |
| 723 | */ |
| 724 | move_to_lru(newpage); |
| 725 | if (result) { |
| 726 | if (rc) |
| 727 | *result = rc; |
| 728 | else |
| 729 | *result = page_to_nid(newpage); |
| 730 | } |
| 731 | return rc; |
| 732 | } |
| 733 | |
| 734 | /* |
| 735 | * migrate_pages |
| 736 | * |
| 737 | * The function takes one list of pages to migrate and a function |
| 738 | * that determines from the page to be migrated and the private data |
| 739 | * the target of the move and allocates the page. |
| 740 | * |
| 741 | * The function returns after 10 attempts or if no pages |
| 742 | * are movable anymore because to has become empty |
| 743 | * or no retryable pages exist anymore. All pages will be |
| 744 | * returned to the LRU or freed. |
| 745 | * |
| 746 | * Return: Number of pages not migrated or error code. |
| 747 | */ |
| 748 | int migrate_pages(struct list_head *from, |
| 749 | new_page_t get_new_page, unsigned long private) |
| 750 | { |
| 751 | int retry = 1; |
| 752 | int nr_failed = 0; |
| 753 | int pass = 0; |
| 754 | struct page *page; |
| 755 | struct page *page2; |
| 756 | int swapwrite = current->flags & PF_SWAPWRITE; |
| 757 | int rc; |
| 758 | |
| 759 | if (!swapwrite) |
| 760 | current->flags |= PF_SWAPWRITE; |
| 761 | |
| 762 | for(pass = 0; pass < 10 && retry; pass++) { |
| 763 | retry = 0; |
| 764 | |
| 765 | list_for_each_entry_safe(page, page2, from, lru) { |
| 766 | cond_resched(); |
| 767 | |
| 768 | rc = unmap_and_move(get_new_page, private, |
| 769 | page, pass > 2); |
| 770 | |
| 771 | switch(rc) { |
| 772 | case -ENOMEM: |
| 773 | goto out; |
| 774 | case -EAGAIN: |
| 775 | retry++; |
| 776 | break; |
| 777 | case 0: |
| 778 | break; |
| 779 | default: |
| 780 | /* Permanent failure */ |
| 781 | nr_failed++; |
| 782 | break; |
| 783 | } |
| 784 | } |
| 785 | } |
| 786 | rc = 0; |
| 787 | out: |
| 788 | if (!swapwrite) |
| 789 | current->flags &= ~PF_SWAPWRITE; |
| 790 | |
| 791 | putback_lru_pages(from); |
| 792 | |
| 793 | if (rc) |
| 794 | return rc; |
| 795 | |
| 796 | return nr_failed + retry; |
| 797 | } |
| 798 | |
| 799 | #ifdef CONFIG_NUMA |
| 800 | /* |
| 801 | * Move a list of individual pages |
| 802 | */ |
| 803 | struct page_to_node { |
| 804 | unsigned long addr; |
| 805 | struct page *page; |
| 806 | int node; |
| 807 | int status; |
| 808 | }; |
| 809 | |
| 810 | static struct page *new_page_node(struct page *p, unsigned long private, |
| 811 | int **result) |
| 812 | { |
| 813 | struct page_to_node *pm = (struct page_to_node *)private; |
| 814 | |
| 815 | while (pm->node != MAX_NUMNODES && pm->page != p) |
| 816 | pm++; |
| 817 | |
| 818 | if (pm->node == MAX_NUMNODES) |
| 819 | return NULL; |
| 820 | |
| 821 | *result = &pm->status; |
| 822 | |
| 823 | return alloc_pages_node(pm->node, |
| 824 | GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); |
| 825 | } |
| 826 | |
| 827 | /* |
| 828 | * Move a set of pages as indicated in the pm array. The addr |
| 829 | * field must be set to the virtual address of the page to be moved |
| 830 | * and the node number must contain a valid target node. |
| 831 | */ |
| 832 | static int do_move_pages(struct mm_struct *mm, 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 | migrate_prep(); |
| 845 | for (pp = pm; pp->node != MAX_NUMNODES; pp++) { |
| 846 | struct vm_area_struct *vma; |
| 847 | struct page *page; |
| 848 | |
| 849 | /* |
| 850 | * A valid page pointer that will not match any of the |
| 851 | * pages that will be moved. |
| 852 | */ |
| 853 | pp->page = ZERO_PAGE(0); |
| 854 | |
| 855 | err = -EFAULT; |
| 856 | vma = find_vma(mm, pp->addr); |
| 857 | if (!vma || !vma_migratable(vma)) |
| 858 | goto set_status; |
| 859 | |
| 860 | page = follow_page(vma, pp->addr, FOLL_GET); |
| 861 | err = -ENOENT; |
| 862 | if (!page) |
| 863 | goto set_status; |
| 864 | |
| 865 | if (PageReserved(page)) /* Check for zero page */ |
| 866 | goto put_and_set; |
| 867 | |
| 868 | pp->page = page; |
| 869 | err = page_to_nid(page); |
| 870 | |
| 871 | if (err == pp->node) |
| 872 | /* |
| 873 | * Node already in the right place |
| 874 | */ |
| 875 | goto put_and_set; |
| 876 | |
| 877 | err = -EACCES; |
| 878 | if (page_mapcount(page) > 1 && |
| 879 | !migrate_all) |
| 880 | goto put_and_set; |
| 881 | |
| 882 | err = isolate_lru_page(page, &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 | if (!list_empty(&pagelist)) |
| 895 | err = migrate_pages(&pagelist, new_page_node, |
| 896 | (unsigned long)pm); |
| 897 | else |
| 898 | err = -ENOENT; |
| 899 | |
| 900 | up_read(&mm->mmap_sem); |
| 901 | return err; |
| 902 | } |
| 903 | |
| 904 | /* |
| 905 | * Determine the nodes of a list of pages. The addr in the pm array |
| 906 | * must have been set to the virtual address of which we want to determine |
| 907 | * the node number. |
| 908 | */ |
| 909 | static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm) |
| 910 | { |
| 911 | down_read(&mm->mmap_sem); |
| 912 | |
| 913 | for ( ; pm->node != MAX_NUMNODES; pm++) { |
| 914 | struct vm_area_struct *vma; |
| 915 | struct page *page; |
| 916 | int err; |
| 917 | |
| 918 | err = -EFAULT; |
| 919 | vma = find_vma(mm, pm->addr); |
| 920 | if (!vma) |
| 921 | goto set_status; |
| 922 | |
| 923 | page = follow_page(vma, pm->addr, 0); |
| 924 | err = -ENOENT; |
| 925 | /* Use PageReserved to check for zero page */ |
| 926 | if (!page || PageReserved(page)) |
| 927 | goto set_status; |
| 928 | |
| 929 | err = page_to_nid(page); |
| 930 | set_status: |
| 931 | pm->status = err; |
| 932 | } |
| 933 | |
| 934 | up_read(&mm->mmap_sem); |
| 935 | return 0; |
| 936 | } |
| 937 | |
| 938 | /* |
| 939 | * Move a list of pages in the address space of the currently executing |
| 940 | * process. |
| 941 | */ |
| 942 | asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages, |
| 943 | const void __user * __user *pages, |
| 944 | const int __user *nodes, |
| 945 | int __user *status, int flags) |
| 946 | { |
| 947 | int err = 0; |
| 948 | int i; |
| 949 | struct task_struct *task; |
| 950 | nodemask_t task_nodes; |
| 951 | struct mm_struct *mm; |
| 952 | struct page_to_node *pm = NULL; |
| 953 | |
| 954 | /* Check flags */ |
| 955 | if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) |
| 956 | return -EINVAL; |
| 957 | |
| 958 | if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) |
| 959 | return -EPERM; |
| 960 | |
| 961 | /* Find the mm_struct */ |
| 962 | read_lock(&tasklist_lock); |
| 963 | task = pid ? find_task_by_vpid(pid) : current; |
| 964 | if (!task) { |
| 965 | read_unlock(&tasklist_lock); |
| 966 | return -ESRCH; |
| 967 | } |
| 968 | mm = get_task_mm(task); |
| 969 | read_unlock(&tasklist_lock); |
| 970 | |
| 971 | if (!mm) |
| 972 | return -EINVAL; |
| 973 | |
| 974 | /* |
| 975 | * Check if this process has the right to modify the specified |
| 976 | * process. The right exists if the process has administrative |
| 977 | * capabilities, superuser privileges or the same |
| 978 | * userid as the target process. |
| 979 | */ |
| 980 | if ((current->euid != task->suid) && (current->euid != task->uid) && |
| 981 | (current->uid != task->suid) && (current->uid != task->uid) && |
| 982 | !capable(CAP_SYS_NICE)) { |
| 983 | err = -EPERM; |
| 984 | goto out2; |
| 985 | } |
| 986 | |
| 987 | err = security_task_movememory(task); |
| 988 | if (err) |
| 989 | goto out2; |
| 990 | |
| 991 | |
| 992 | task_nodes = cpuset_mems_allowed(task); |
| 993 | |
| 994 | /* Limit nr_pages so that the multiplication may not overflow */ |
| 995 | if (nr_pages >= ULONG_MAX / sizeof(struct page_to_node) - 1) { |
| 996 | err = -E2BIG; |
| 997 | goto out2; |
| 998 | } |
| 999 | |
| 1000 | pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node)); |
| 1001 | if (!pm) { |
| 1002 | err = -ENOMEM; |
| 1003 | goto out2; |
| 1004 | } |
| 1005 | |
| 1006 | /* |
| 1007 | * Get parameters from user space and initialize the pm |
| 1008 | * array. Return various errors if the user did something wrong. |
| 1009 | */ |
| 1010 | for (i = 0; i < nr_pages; i++) { |
| 1011 | const void __user *p; |
| 1012 | |
| 1013 | err = -EFAULT; |
| 1014 | if (get_user(p, pages + i)) |
| 1015 | goto out; |
| 1016 | |
| 1017 | pm[i].addr = (unsigned long)p; |
| 1018 | if (nodes) { |
| 1019 | int node; |
| 1020 | |
| 1021 | if (get_user(node, nodes + i)) |
| 1022 | goto out; |
| 1023 | |
| 1024 | err = -ENODEV; |
| 1025 | if (!node_state(node, N_HIGH_MEMORY)) |
| 1026 | goto out; |
| 1027 | |
| 1028 | err = -EACCES; |
| 1029 | if (!node_isset(node, task_nodes)) |
| 1030 | goto out; |
| 1031 | |
| 1032 | pm[i].node = node; |
| 1033 | } else |
| 1034 | pm[i].node = 0; /* anything to not match MAX_NUMNODES */ |
| 1035 | } |
| 1036 | /* End marker */ |
| 1037 | pm[nr_pages].node = MAX_NUMNODES; |
| 1038 | |
| 1039 | if (nodes) |
| 1040 | err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL); |
| 1041 | else |
| 1042 | err = do_pages_stat(mm, pm); |
| 1043 | |
| 1044 | if (err >= 0) |
| 1045 | /* Return status information */ |
| 1046 | for (i = 0; i < nr_pages; i++) |
| 1047 | if (put_user(pm[i].status, status + i)) |
| 1048 | err = -EFAULT; |
| 1049 | |
| 1050 | out: |
| 1051 | vfree(pm); |
| 1052 | out2: |
| 1053 | mmput(mm); |
| 1054 | return err; |
| 1055 | } |
| 1056 | #endif |
| 1057 | |
| 1058 | /* |
| 1059 | * Call migration functions in the vma_ops that may prepare |
| 1060 | * memory in a vm for migration. migration functions may perform |
| 1061 | * the migration for vmas that do not have an underlying page struct. |
| 1062 | */ |
| 1063 | int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, |
| 1064 | const nodemask_t *from, unsigned long flags) |
| 1065 | { |
| 1066 | struct vm_area_struct *vma; |
| 1067 | int err = 0; |
| 1068 | |
| 1069 | for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) { |
| 1070 | if (vma->vm_ops && vma->vm_ops->migrate) { |
| 1071 | err = vma->vm_ops->migrate(vma, to, from, flags); |
| 1072 | if (err) |
| 1073 | break; |
| 1074 | } |
| 1075 | } |
| 1076 | return err; |
| 1077 | } |