x86: add PAGE_KERNEL_EXEC_NOCACHE
[wrt350n-kernel.git] / mm / rmap.c
blobdbc2ca2057a54ff2c4a709de4b6e9a01694241bb
1 /*
2 * mm/rmap.c - physical to virtual reverse mappings
4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5 * Released under the General Public License (GPL).
7 * Simple, low overhead reverse mapping scheme.
8 * Please try to keep this thing as modular as possible.
10 * Provides methods for unmapping each kind of mapped page:
11 * the anon methods track anonymous pages, and
12 * the file methods track pages belonging to an inode.
14 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
15 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
16 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
17 * Contributions by Hugh Dickins <hugh@veritas.com> 2003, 2004
21 * Lock ordering in mm:
23 * inode->i_mutex (while writing or truncating, not reading or faulting)
24 * inode->i_alloc_sem (vmtruncate_range)
25 * mm->mmap_sem
26 * page->flags PG_locked (lock_page)
27 * mapping->i_mmap_lock
28 * anon_vma->lock
29 * mm->page_table_lock or pte_lock
30 * zone->lru_lock (in mark_page_accessed, isolate_lru_page)
31 * swap_lock (in swap_duplicate, swap_info_get)
32 * mmlist_lock (in mmput, drain_mmlist and others)
33 * mapping->private_lock (in __set_page_dirty_buffers)
34 * inode_lock (in set_page_dirty's __mark_inode_dirty)
35 * sb_lock (within inode_lock in fs/fs-writeback.c)
36 * mapping->tree_lock (widely used, in set_page_dirty,
37 * in arch-dependent flush_dcache_mmap_lock,
38 * within inode_lock in __sync_single_inode)
39 * zone->lock (within radix tree node alloc)
42 #include <linux/mm.h>
43 #include <linux/pagemap.h>
44 #include <linux/swap.h>
45 #include <linux/swapops.h>
46 #include <linux/slab.h>
47 #include <linux/init.h>
48 #include <linux/rmap.h>
49 #include <linux/rcupdate.h>
50 #include <linux/module.h>
51 #include <linux/kallsyms.h>
53 #include <asm/tlbflush.h>
55 struct kmem_cache *anon_vma_cachep;
57 /* This must be called under the mmap_sem. */
58 int anon_vma_prepare(struct vm_area_struct *vma)
60 struct anon_vma *anon_vma = vma->anon_vma;
62 might_sleep();
63 if (unlikely(!anon_vma)) {
64 struct mm_struct *mm = vma->vm_mm;
65 struct anon_vma *allocated, *locked;
67 anon_vma = find_mergeable_anon_vma(vma);
68 if (anon_vma) {
69 allocated = NULL;
70 locked = anon_vma;
71 spin_lock(&locked->lock);
72 } else {
73 anon_vma = anon_vma_alloc();
74 if (unlikely(!anon_vma))
75 return -ENOMEM;
76 allocated = anon_vma;
77 locked = NULL;
80 /* page_table_lock to protect against threads */
81 spin_lock(&mm->page_table_lock);
82 if (likely(!vma->anon_vma)) {
83 vma->anon_vma = anon_vma;
84 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
85 allocated = NULL;
87 spin_unlock(&mm->page_table_lock);
89 if (locked)
90 spin_unlock(&locked->lock);
91 if (unlikely(allocated))
92 anon_vma_free(allocated);
94 return 0;
97 void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
99 BUG_ON(vma->anon_vma != next->anon_vma);
100 list_del(&next->anon_vma_node);
103 void __anon_vma_link(struct vm_area_struct *vma)
105 struct anon_vma *anon_vma = vma->anon_vma;
107 if (anon_vma)
108 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
111 void anon_vma_link(struct vm_area_struct *vma)
113 struct anon_vma *anon_vma = vma->anon_vma;
115 if (anon_vma) {
116 spin_lock(&anon_vma->lock);
117 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
118 spin_unlock(&anon_vma->lock);
122 void anon_vma_unlink(struct vm_area_struct *vma)
124 struct anon_vma *anon_vma = vma->anon_vma;
125 int empty;
127 if (!anon_vma)
128 return;
130 spin_lock(&anon_vma->lock);
131 list_del(&vma->anon_vma_node);
133 /* We must garbage collect the anon_vma if it's empty */
134 empty = list_empty(&anon_vma->head);
135 spin_unlock(&anon_vma->lock);
137 if (empty)
138 anon_vma_free(anon_vma);
141 static void anon_vma_ctor(struct kmem_cache *cachep, void *data)
143 struct anon_vma *anon_vma = data;
145 spin_lock_init(&anon_vma->lock);
146 INIT_LIST_HEAD(&anon_vma->head);
149 void __init anon_vma_init(void)
151 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
152 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
156 * Getting a lock on a stable anon_vma from a page off the LRU is
157 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
159 static struct anon_vma *page_lock_anon_vma(struct page *page)
161 struct anon_vma *anon_vma;
162 unsigned long anon_mapping;
164 rcu_read_lock();
165 anon_mapping = (unsigned long) page->mapping;
166 if (!(anon_mapping & PAGE_MAPPING_ANON))
167 goto out;
168 if (!page_mapped(page))
169 goto out;
171 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
172 spin_lock(&anon_vma->lock);
173 return anon_vma;
174 out:
175 rcu_read_unlock();
176 return NULL;
179 static void page_unlock_anon_vma(struct anon_vma *anon_vma)
181 spin_unlock(&anon_vma->lock);
182 rcu_read_unlock();
186 * At what user virtual address is page expected in @vma?
187 * Returns virtual address or -EFAULT if page's index/offset is not
188 * within the range mapped the @vma.
190 static inline unsigned long
191 vma_address(struct page *page, struct vm_area_struct *vma)
193 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
194 unsigned long address;
196 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
197 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
198 /* page should be within @vma mapping range */
199 return -EFAULT;
201 return address;
205 * At what user virtual address is page expected in vma? checking that the
206 * page matches the vma: currently only used on anon pages, by unuse_vma;
208 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
210 if (PageAnon(page)) {
211 if ((void *)vma->anon_vma !=
212 (void *)page->mapping - PAGE_MAPPING_ANON)
213 return -EFAULT;
214 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
215 if (!vma->vm_file ||
216 vma->vm_file->f_mapping != page->mapping)
217 return -EFAULT;
218 } else
219 return -EFAULT;
220 return vma_address(page, vma);
224 * Check that @page is mapped at @address into @mm.
226 * On success returns with pte mapped and locked.
228 pte_t *page_check_address(struct page *page, struct mm_struct *mm,
229 unsigned long address, spinlock_t **ptlp)
231 pgd_t *pgd;
232 pud_t *pud;
233 pmd_t *pmd;
234 pte_t *pte;
235 spinlock_t *ptl;
237 pgd = pgd_offset(mm, address);
238 if (!pgd_present(*pgd))
239 return NULL;
241 pud = pud_offset(pgd, address);
242 if (!pud_present(*pud))
243 return NULL;
245 pmd = pmd_offset(pud, address);
246 if (!pmd_present(*pmd))
247 return NULL;
249 pte = pte_offset_map(pmd, address);
250 /* Make a quick check before getting the lock */
251 if (!pte_present(*pte)) {
252 pte_unmap(pte);
253 return NULL;
256 ptl = pte_lockptr(mm, pmd);
257 spin_lock(ptl);
258 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
259 *ptlp = ptl;
260 return pte;
262 pte_unmap_unlock(pte, ptl);
263 return NULL;
267 * Subfunctions of page_referenced: page_referenced_one called
268 * repeatedly from either page_referenced_anon or page_referenced_file.
270 static int page_referenced_one(struct page *page,
271 struct vm_area_struct *vma, unsigned int *mapcount)
273 struct mm_struct *mm = vma->vm_mm;
274 unsigned long address;
275 pte_t *pte;
276 spinlock_t *ptl;
277 int referenced = 0;
279 address = vma_address(page, vma);
280 if (address == -EFAULT)
281 goto out;
283 pte = page_check_address(page, mm, address, &ptl);
284 if (!pte)
285 goto out;
287 if (ptep_clear_flush_young(vma, address, pte))
288 referenced++;
290 /* Pretend the page is referenced if the task has the
291 swap token and is in the middle of a page fault. */
292 if (mm != current->mm && has_swap_token(mm) &&
293 rwsem_is_locked(&mm->mmap_sem))
294 referenced++;
296 (*mapcount)--;
297 pte_unmap_unlock(pte, ptl);
298 out:
299 return referenced;
302 static int page_referenced_anon(struct page *page)
304 unsigned int mapcount;
305 struct anon_vma *anon_vma;
306 struct vm_area_struct *vma;
307 int referenced = 0;
309 anon_vma = page_lock_anon_vma(page);
310 if (!anon_vma)
311 return referenced;
313 mapcount = page_mapcount(page);
314 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
315 referenced += page_referenced_one(page, vma, &mapcount);
316 if (!mapcount)
317 break;
320 page_unlock_anon_vma(anon_vma);
321 return referenced;
325 * page_referenced_file - referenced check for object-based rmap
326 * @page: the page we're checking references on.
328 * For an object-based mapped page, find all the places it is mapped and
329 * check/clear the referenced flag. This is done by following the page->mapping
330 * pointer, then walking the chain of vmas it holds. It returns the number
331 * of references it found.
333 * This function is only called from page_referenced for object-based pages.
335 static int page_referenced_file(struct page *page)
337 unsigned int mapcount;
338 struct address_space *mapping = page->mapping;
339 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
340 struct vm_area_struct *vma;
341 struct prio_tree_iter iter;
342 int referenced = 0;
345 * The caller's checks on page->mapping and !PageAnon have made
346 * sure that this is a file page: the check for page->mapping
347 * excludes the case just before it gets set on an anon page.
349 BUG_ON(PageAnon(page));
352 * The page lock not only makes sure that page->mapping cannot
353 * suddenly be NULLified by truncation, it makes sure that the
354 * structure at mapping cannot be freed and reused yet,
355 * so we can safely take mapping->i_mmap_lock.
357 BUG_ON(!PageLocked(page));
359 spin_lock(&mapping->i_mmap_lock);
362 * i_mmap_lock does not stabilize mapcount at all, but mapcount
363 * is more likely to be accurate if we note it after spinning.
365 mapcount = page_mapcount(page);
367 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
368 if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
369 == (VM_LOCKED|VM_MAYSHARE)) {
370 referenced++;
371 break;
373 referenced += page_referenced_one(page, vma, &mapcount);
374 if (!mapcount)
375 break;
378 spin_unlock(&mapping->i_mmap_lock);
379 return referenced;
383 * page_referenced - test if the page was referenced
384 * @page: the page to test
385 * @is_locked: caller holds lock on the page
387 * Quick test_and_clear_referenced for all mappings to a page,
388 * returns the number of ptes which referenced the page.
390 int page_referenced(struct page *page, int is_locked)
392 int referenced = 0;
394 if (page_test_and_clear_young(page))
395 referenced++;
397 if (TestClearPageReferenced(page))
398 referenced++;
400 if (page_mapped(page) && page->mapping) {
401 if (PageAnon(page))
402 referenced += page_referenced_anon(page);
403 else if (is_locked)
404 referenced += page_referenced_file(page);
405 else if (TestSetPageLocked(page))
406 referenced++;
407 else {
408 if (page->mapping)
409 referenced += page_referenced_file(page);
410 unlock_page(page);
413 return referenced;
416 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma)
418 struct mm_struct *mm = vma->vm_mm;
419 unsigned long address;
420 pte_t *pte;
421 spinlock_t *ptl;
422 int ret = 0;
424 address = vma_address(page, vma);
425 if (address == -EFAULT)
426 goto out;
428 pte = page_check_address(page, mm, address, &ptl);
429 if (!pte)
430 goto out;
432 if (pte_dirty(*pte) || pte_write(*pte)) {
433 pte_t entry;
435 flush_cache_page(vma, address, pte_pfn(*pte));
436 entry = ptep_clear_flush(vma, address, pte);
437 entry = pte_wrprotect(entry);
438 entry = pte_mkclean(entry);
439 set_pte_at(mm, address, pte, entry);
440 ret = 1;
443 pte_unmap_unlock(pte, ptl);
444 out:
445 return ret;
448 static int page_mkclean_file(struct address_space *mapping, struct page *page)
450 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
451 struct vm_area_struct *vma;
452 struct prio_tree_iter iter;
453 int ret = 0;
455 BUG_ON(PageAnon(page));
457 spin_lock(&mapping->i_mmap_lock);
458 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
459 if (vma->vm_flags & VM_SHARED)
460 ret += page_mkclean_one(page, vma);
462 spin_unlock(&mapping->i_mmap_lock);
463 return ret;
466 int page_mkclean(struct page *page)
468 int ret = 0;
470 BUG_ON(!PageLocked(page));
472 if (page_mapped(page)) {
473 struct address_space *mapping = page_mapping(page);
474 if (mapping) {
475 ret = page_mkclean_file(mapping, page);
476 if (page_test_dirty(page)) {
477 page_clear_dirty(page);
478 ret = 1;
483 return ret;
485 EXPORT_SYMBOL_GPL(page_mkclean);
488 * page_set_anon_rmap - setup new anonymous rmap
489 * @page: the page to add the mapping to
490 * @vma: the vm area in which the mapping is added
491 * @address: the user virtual address mapped
493 static void __page_set_anon_rmap(struct page *page,
494 struct vm_area_struct *vma, unsigned long address)
496 struct anon_vma *anon_vma = vma->anon_vma;
498 BUG_ON(!anon_vma);
499 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
500 page->mapping = (struct address_space *) anon_vma;
502 page->index = linear_page_index(vma, address);
505 * nr_mapped state can be updated without turning off
506 * interrupts because it is not modified via interrupt.
508 __inc_zone_page_state(page, NR_ANON_PAGES);
512 * page_set_anon_rmap - sanity check anonymous rmap addition
513 * @page: the page to add the mapping to
514 * @vma: the vm area in which the mapping is added
515 * @address: the user virtual address mapped
517 static void __page_check_anon_rmap(struct page *page,
518 struct vm_area_struct *vma, unsigned long address)
520 #ifdef CONFIG_DEBUG_VM
522 * The page's anon-rmap details (mapping and index) are guaranteed to
523 * be set up correctly at this point.
525 * We have exclusion against page_add_anon_rmap because the caller
526 * always holds the page locked, except if called from page_dup_rmap,
527 * in which case the page is already known to be setup.
529 * We have exclusion against page_add_new_anon_rmap because those pages
530 * are initially only visible via the pagetables, and the pte is locked
531 * over the call to page_add_new_anon_rmap.
533 struct anon_vma *anon_vma = vma->anon_vma;
534 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
535 BUG_ON(page->mapping != (struct address_space *)anon_vma);
536 BUG_ON(page->index != linear_page_index(vma, address));
537 #endif
541 * page_add_anon_rmap - add pte mapping to an anonymous page
542 * @page: the page to add the mapping to
543 * @vma: the vm area in which the mapping is added
544 * @address: the user virtual address mapped
546 * The caller needs to hold the pte lock and the page must be locked.
548 void page_add_anon_rmap(struct page *page,
549 struct vm_area_struct *vma, unsigned long address)
551 VM_BUG_ON(!PageLocked(page));
552 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
553 if (atomic_inc_and_test(&page->_mapcount))
554 __page_set_anon_rmap(page, vma, address);
555 else
556 __page_check_anon_rmap(page, vma, address);
560 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
561 * @page: the page to add the mapping to
562 * @vma: the vm area in which the mapping is added
563 * @address: the user virtual address mapped
565 * Same as page_add_anon_rmap but must only be called on *new* pages.
566 * This means the inc-and-test can be bypassed.
567 * Page does not have to be locked.
569 void page_add_new_anon_rmap(struct page *page,
570 struct vm_area_struct *vma, unsigned long address)
572 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
573 atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
574 __page_set_anon_rmap(page, vma, address);
578 * page_add_file_rmap - add pte mapping to a file page
579 * @page: the page to add the mapping to
581 * The caller needs to hold the pte lock.
583 void page_add_file_rmap(struct page *page)
585 if (atomic_inc_and_test(&page->_mapcount))
586 __inc_zone_page_state(page, NR_FILE_MAPPED);
589 #ifdef CONFIG_DEBUG_VM
591 * page_dup_rmap - duplicate pte mapping to a page
592 * @page: the page to add the mapping to
594 * For copy_page_range only: minimal extract from page_add_file_rmap /
595 * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
596 * quicker.
598 * The caller needs to hold the pte lock.
600 void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
602 BUG_ON(page_mapcount(page) == 0);
603 if (PageAnon(page))
604 __page_check_anon_rmap(page, vma, address);
605 atomic_inc(&page->_mapcount);
607 #endif
610 * page_remove_rmap - take down pte mapping from a page
611 * @page: page to remove mapping from
613 * The caller needs to hold the pte lock.
615 void page_remove_rmap(struct page *page, struct vm_area_struct *vma)
617 if (atomic_add_negative(-1, &page->_mapcount)) {
618 if (unlikely(page_mapcount(page) < 0)) {
619 printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
620 printk (KERN_EMERG " page pfn = %lx\n", page_to_pfn(page));
621 printk (KERN_EMERG " page->flags = %lx\n", page->flags);
622 printk (KERN_EMERG " page->count = %x\n", page_count(page));
623 printk (KERN_EMERG " page->mapping = %p\n", page->mapping);
624 print_symbol (KERN_EMERG " vma->vm_ops = %s\n", (unsigned long)vma->vm_ops);
625 if (vma->vm_ops) {
626 print_symbol (KERN_EMERG " vma->vm_ops->nopage = %s\n", (unsigned long)vma->vm_ops->nopage);
627 print_symbol (KERN_EMERG " vma->vm_ops->fault = %s\n", (unsigned long)vma->vm_ops->fault);
629 if (vma->vm_file && vma->vm_file->f_op)
630 print_symbol (KERN_EMERG " vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma->vm_file->f_op->mmap);
631 BUG();
635 * It would be tidy to reset the PageAnon mapping here,
636 * but that might overwrite a racing page_add_anon_rmap
637 * which increments mapcount after us but sets mapping
638 * before us: so leave the reset to free_hot_cold_page,
639 * and remember that it's only reliable while mapped.
640 * Leaving it set also helps swapoff to reinstate ptes
641 * faster for those pages still in swapcache.
643 if (page_test_dirty(page)) {
644 page_clear_dirty(page);
645 set_page_dirty(page);
647 __dec_zone_page_state(page,
648 PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
653 * Subfunctions of try_to_unmap: try_to_unmap_one called
654 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
656 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
657 int migration)
659 struct mm_struct *mm = vma->vm_mm;
660 unsigned long address;
661 pte_t *pte;
662 pte_t pteval;
663 spinlock_t *ptl;
664 int ret = SWAP_AGAIN;
666 address = vma_address(page, vma);
667 if (address == -EFAULT)
668 goto out;
670 pte = page_check_address(page, mm, address, &ptl);
671 if (!pte)
672 goto out;
675 * If the page is mlock()d, we cannot swap it out.
676 * If it's recently referenced (perhaps page_referenced
677 * skipped over this mm) then we should reactivate it.
679 if (!migration && ((vma->vm_flags & VM_LOCKED) ||
680 (ptep_clear_flush_young(vma, address, pte)))) {
681 ret = SWAP_FAIL;
682 goto out_unmap;
685 /* Nuke the page table entry. */
686 flush_cache_page(vma, address, page_to_pfn(page));
687 pteval = ptep_clear_flush(vma, address, pte);
689 /* Move the dirty bit to the physical page now the pte is gone. */
690 if (pte_dirty(pteval))
691 set_page_dirty(page);
693 /* Update high watermark before we lower rss */
694 update_hiwater_rss(mm);
696 if (PageAnon(page)) {
697 swp_entry_t entry = { .val = page_private(page) };
699 if (PageSwapCache(page)) {
701 * Store the swap location in the pte.
702 * See handle_pte_fault() ...
704 swap_duplicate(entry);
705 if (list_empty(&mm->mmlist)) {
706 spin_lock(&mmlist_lock);
707 if (list_empty(&mm->mmlist))
708 list_add(&mm->mmlist, &init_mm.mmlist);
709 spin_unlock(&mmlist_lock);
711 dec_mm_counter(mm, anon_rss);
712 #ifdef CONFIG_MIGRATION
713 } else {
715 * Store the pfn of the page in a special migration
716 * pte. do_swap_page() will wait until the migration
717 * pte is removed and then restart fault handling.
719 BUG_ON(!migration);
720 entry = make_migration_entry(page, pte_write(pteval));
721 #endif
723 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
724 BUG_ON(pte_file(*pte));
725 } else
726 #ifdef CONFIG_MIGRATION
727 if (migration) {
728 /* Establish migration entry for a file page */
729 swp_entry_t entry;
730 entry = make_migration_entry(page, pte_write(pteval));
731 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
732 } else
733 #endif
734 dec_mm_counter(mm, file_rss);
737 page_remove_rmap(page, vma);
738 page_cache_release(page);
740 out_unmap:
741 pte_unmap_unlock(pte, ptl);
742 out:
743 return ret;
747 * objrmap doesn't work for nonlinear VMAs because the assumption that
748 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
749 * Consequently, given a particular page and its ->index, we cannot locate the
750 * ptes which are mapping that page without an exhaustive linear search.
752 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
753 * maps the file to which the target page belongs. The ->vm_private_data field
754 * holds the current cursor into that scan. Successive searches will circulate
755 * around the vma's virtual address space.
757 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
758 * more scanning pressure is placed against them as well. Eventually pages
759 * will become fully unmapped and are eligible for eviction.
761 * For very sparsely populated VMAs this is a little inefficient - chances are
762 * there there won't be many ptes located within the scan cluster. In this case
763 * maybe we could scan further - to the end of the pte page, perhaps.
765 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
766 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
768 static void try_to_unmap_cluster(unsigned long cursor,
769 unsigned int *mapcount, struct vm_area_struct *vma)
771 struct mm_struct *mm = vma->vm_mm;
772 pgd_t *pgd;
773 pud_t *pud;
774 pmd_t *pmd;
775 pte_t *pte;
776 pte_t pteval;
777 spinlock_t *ptl;
778 struct page *page;
779 unsigned long address;
780 unsigned long end;
782 address = (vma->vm_start + cursor) & CLUSTER_MASK;
783 end = address + CLUSTER_SIZE;
784 if (address < vma->vm_start)
785 address = vma->vm_start;
786 if (end > vma->vm_end)
787 end = vma->vm_end;
789 pgd = pgd_offset(mm, address);
790 if (!pgd_present(*pgd))
791 return;
793 pud = pud_offset(pgd, address);
794 if (!pud_present(*pud))
795 return;
797 pmd = pmd_offset(pud, address);
798 if (!pmd_present(*pmd))
799 return;
801 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
803 /* Update high watermark before we lower rss */
804 update_hiwater_rss(mm);
806 for (; address < end; pte++, address += PAGE_SIZE) {
807 if (!pte_present(*pte))
808 continue;
809 page = vm_normal_page(vma, address, *pte);
810 BUG_ON(!page || PageAnon(page));
812 if (ptep_clear_flush_young(vma, address, pte))
813 continue;
815 /* Nuke the page table entry. */
816 flush_cache_page(vma, address, pte_pfn(*pte));
817 pteval = ptep_clear_flush(vma, address, pte);
819 /* If nonlinear, store the file page offset in the pte. */
820 if (page->index != linear_page_index(vma, address))
821 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
823 /* Move the dirty bit to the physical page now the pte is gone. */
824 if (pte_dirty(pteval))
825 set_page_dirty(page);
827 page_remove_rmap(page, vma);
828 page_cache_release(page);
829 dec_mm_counter(mm, file_rss);
830 (*mapcount)--;
832 pte_unmap_unlock(pte - 1, ptl);
835 static int try_to_unmap_anon(struct page *page, int migration)
837 struct anon_vma *anon_vma;
838 struct vm_area_struct *vma;
839 int ret = SWAP_AGAIN;
841 anon_vma = page_lock_anon_vma(page);
842 if (!anon_vma)
843 return ret;
845 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
846 ret = try_to_unmap_one(page, vma, migration);
847 if (ret == SWAP_FAIL || !page_mapped(page))
848 break;
851 page_unlock_anon_vma(anon_vma);
852 return ret;
856 * try_to_unmap_file - unmap file page using the object-based rmap method
857 * @page: the page to unmap
859 * Find all the mappings of a page using the mapping pointer and the vma chains
860 * contained in the address_space struct it points to.
862 * This function is only called from try_to_unmap for object-based pages.
864 static int try_to_unmap_file(struct page *page, int migration)
866 struct address_space *mapping = page->mapping;
867 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
868 struct vm_area_struct *vma;
869 struct prio_tree_iter iter;
870 int ret = SWAP_AGAIN;
871 unsigned long cursor;
872 unsigned long max_nl_cursor = 0;
873 unsigned long max_nl_size = 0;
874 unsigned int mapcount;
876 spin_lock(&mapping->i_mmap_lock);
877 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
878 ret = try_to_unmap_one(page, vma, migration);
879 if (ret == SWAP_FAIL || !page_mapped(page))
880 goto out;
883 if (list_empty(&mapping->i_mmap_nonlinear))
884 goto out;
886 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
887 shared.vm_set.list) {
888 if ((vma->vm_flags & VM_LOCKED) && !migration)
889 continue;
890 cursor = (unsigned long) vma->vm_private_data;
891 if (cursor > max_nl_cursor)
892 max_nl_cursor = cursor;
893 cursor = vma->vm_end - vma->vm_start;
894 if (cursor > max_nl_size)
895 max_nl_size = cursor;
898 if (max_nl_size == 0) { /* any nonlinears locked or reserved */
899 ret = SWAP_FAIL;
900 goto out;
904 * We don't try to search for this page in the nonlinear vmas,
905 * and page_referenced wouldn't have found it anyway. Instead
906 * just walk the nonlinear vmas trying to age and unmap some.
907 * The mapcount of the page we came in with is irrelevant,
908 * but even so use it as a guide to how hard we should try?
910 mapcount = page_mapcount(page);
911 if (!mapcount)
912 goto out;
913 cond_resched_lock(&mapping->i_mmap_lock);
915 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
916 if (max_nl_cursor == 0)
917 max_nl_cursor = CLUSTER_SIZE;
919 do {
920 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
921 shared.vm_set.list) {
922 if ((vma->vm_flags & VM_LOCKED) && !migration)
923 continue;
924 cursor = (unsigned long) vma->vm_private_data;
925 while ( cursor < max_nl_cursor &&
926 cursor < vma->vm_end - vma->vm_start) {
927 try_to_unmap_cluster(cursor, &mapcount, vma);
928 cursor += CLUSTER_SIZE;
929 vma->vm_private_data = (void *) cursor;
930 if ((int)mapcount <= 0)
931 goto out;
933 vma->vm_private_data = (void *) max_nl_cursor;
935 cond_resched_lock(&mapping->i_mmap_lock);
936 max_nl_cursor += CLUSTER_SIZE;
937 } while (max_nl_cursor <= max_nl_size);
940 * Don't loop forever (perhaps all the remaining pages are
941 * in locked vmas). Reset cursor on all unreserved nonlinear
942 * vmas, now forgetting on which ones it had fallen behind.
944 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
945 vma->vm_private_data = NULL;
946 out:
947 spin_unlock(&mapping->i_mmap_lock);
948 return ret;
952 * try_to_unmap - try to remove all page table mappings to a page
953 * @page: the page to get unmapped
955 * Tries to remove all the page table entries which are mapping this
956 * page, used in the pageout path. Caller must hold the page lock.
957 * Return values are:
959 * SWAP_SUCCESS - we succeeded in removing all mappings
960 * SWAP_AGAIN - we missed a mapping, try again later
961 * SWAP_FAIL - the page is unswappable
963 int try_to_unmap(struct page *page, int migration)
965 int ret;
967 BUG_ON(!PageLocked(page));
969 if (PageAnon(page))
970 ret = try_to_unmap_anon(page, migration);
971 else
972 ret = try_to_unmap_file(page, migration);
974 if (!page_mapped(page))
975 ret = SWAP_SUCCESS;
976 return ret;