e1000e: commit speed/duplex changes for m88 PHY
[linux-2.6.git] / mm / rmap.c
blob10993942d6c989314477291520c6bb6980a0439d
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)
41 #include <linux/mm.h>
42 #include <linux/pagemap.h>
43 #include <linux/swap.h>
44 #include <linux/swapops.h>
45 #include <linux/slab.h>
46 #include <linux/init.h>
47 #include <linux/rmap.h>
48 #include <linux/rcupdate.h>
49 #include <linux/module.h>
50 #include <linux/kallsyms.h>
51 #include <linux/memcontrol.h>
52 #include <linux/mmu_notifier.h>
54 #include <asm/tlbflush.h>
56 #include "internal.h"
58 static struct kmem_cache *anon_vma_cachep;
60 static inline struct anon_vma *anon_vma_alloc(void)
62 return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
65 static inline void anon_vma_free(struct anon_vma *anon_vma)
67 kmem_cache_free(anon_vma_cachep, anon_vma);
70 /**
71 * anon_vma_prepare - attach an anon_vma to a memory region
72 * @vma: the memory region in question
74 * This makes sure the memory mapping described by 'vma' has
75 * an 'anon_vma' attached to it, so that we can associate the
76 * anonymous pages mapped into it with that anon_vma.
78 * The common case will be that we already have one, but if
79 * if not we either need to find an adjacent mapping that we
80 * can re-use the anon_vma from (very common when the only
81 * reason for splitting a vma has been mprotect()), or we
82 * allocate a new one.
84 * Anon-vma allocations are very subtle, because we may have
85 * optimistically looked up an anon_vma in page_lock_anon_vma()
86 * and that may actually touch the spinlock even in the newly
87 * allocated vma (it depends on RCU to make sure that the
88 * anon_vma isn't actually destroyed).
90 * As a result, we need to do proper anon_vma locking even
91 * for the new allocation. At the same time, we do not want
92 * to do any locking for the common case of already having
93 * an anon_vma.
95 * This must be called with the mmap_sem held for reading.
97 int anon_vma_prepare(struct vm_area_struct *vma)
99 struct anon_vma *anon_vma = vma->anon_vma;
101 might_sleep();
102 if (unlikely(!anon_vma)) {
103 struct mm_struct *mm = vma->vm_mm;
104 struct anon_vma *allocated;
106 anon_vma = find_mergeable_anon_vma(vma);
107 allocated = NULL;
108 if (!anon_vma) {
109 anon_vma = anon_vma_alloc();
110 if (unlikely(!anon_vma))
111 return -ENOMEM;
112 allocated = anon_vma;
114 spin_lock(&anon_vma->lock);
116 /* page_table_lock to protect against threads */
117 spin_lock(&mm->page_table_lock);
118 if (likely(!vma->anon_vma)) {
119 vma->anon_vma = anon_vma;
120 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
121 allocated = NULL;
123 spin_unlock(&mm->page_table_lock);
125 spin_unlock(&anon_vma->lock);
126 if (unlikely(allocated))
127 anon_vma_free(allocated);
129 return 0;
132 void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
134 BUG_ON(vma->anon_vma != next->anon_vma);
135 list_del(&next->anon_vma_node);
138 void __anon_vma_link(struct vm_area_struct *vma)
140 struct anon_vma *anon_vma = vma->anon_vma;
142 if (anon_vma)
143 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
146 void anon_vma_link(struct vm_area_struct *vma)
148 struct anon_vma *anon_vma = vma->anon_vma;
150 if (anon_vma) {
151 spin_lock(&anon_vma->lock);
152 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
153 spin_unlock(&anon_vma->lock);
157 void anon_vma_unlink(struct vm_area_struct *vma)
159 struct anon_vma *anon_vma = vma->anon_vma;
160 int empty;
162 if (!anon_vma)
163 return;
165 spin_lock(&anon_vma->lock);
166 list_del(&vma->anon_vma_node);
168 /* We must garbage collect the anon_vma if it's empty */
169 empty = list_empty(&anon_vma->head);
170 spin_unlock(&anon_vma->lock);
172 if (empty)
173 anon_vma_free(anon_vma);
176 static void anon_vma_ctor(void *data)
178 struct anon_vma *anon_vma = data;
180 spin_lock_init(&anon_vma->lock);
181 INIT_LIST_HEAD(&anon_vma->head);
184 void __init anon_vma_init(void)
186 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
187 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
191 * Getting a lock on a stable anon_vma from a page off the LRU is
192 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
194 struct anon_vma *page_lock_anon_vma(struct page *page)
196 struct anon_vma *anon_vma;
197 unsigned long anon_mapping;
199 rcu_read_lock();
200 anon_mapping = (unsigned long) page->mapping;
201 if (!(anon_mapping & PAGE_MAPPING_ANON))
202 goto out;
203 if (!page_mapped(page))
204 goto out;
206 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
207 spin_lock(&anon_vma->lock);
208 return anon_vma;
209 out:
210 rcu_read_unlock();
211 return NULL;
214 void page_unlock_anon_vma(struct anon_vma *anon_vma)
216 spin_unlock(&anon_vma->lock);
217 rcu_read_unlock();
221 * At what user virtual address is page expected in @vma?
222 * Returns virtual address or -EFAULT if page's index/offset is not
223 * within the range mapped the @vma.
225 static inline unsigned long
226 vma_address(struct page *page, struct vm_area_struct *vma)
228 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
229 unsigned long address;
231 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
232 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
233 /* page should be within @vma mapping range */
234 return -EFAULT;
236 return address;
240 * At what user virtual address is page expected in vma? checking that the
241 * page matches the vma: currently only used on anon pages, by unuse_vma;
243 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
245 if (PageAnon(page)) {
246 if ((void *)vma->anon_vma !=
247 (void *)page->mapping - PAGE_MAPPING_ANON)
248 return -EFAULT;
249 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
250 if (!vma->vm_file ||
251 vma->vm_file->f_mapping != page->mapping)
252 return -EFAULT;
253 } else
254 return -EFAULT;
255 return vma_address(page, vma);
259 * Check that @page is mapped at @address into @mm.
261 * If @sync is false, page_check_address may perform a racy check to avoid
262 * the page table lock when the pte is not present (helpful when reclaiming
263 * highly shared pages).
265 * On success returns with pte mapped and locked.
267 pte_t *page_check_address(struct page *page, struct mm_struct *mm,
268 unsigned long address, spinlock_t **ptlp, int sync)
270 pgd_t *pgd;
271 pud_t *pud;
272 pmd_t *pmd;
273 pte_t *pte;
274 spinlock_t *ptl;
276 pgd = pgd_offset(mm, address);
277 if (!pgd_present(*pgd))
278 return NULL;
280 pud = pud_offset(pgd, address);
281 if (!pud_present(*pud))
282 return NULL;
284 pmd = pmd_offset(pud, address);
285 if (!pmd_present(*pmd))
286 return NULL;
288 pte = pte_offset_map(pmd, address);
289 /* Make a quick check before getting the lock */
290 if (!sync && !pte_present(*pte)) {
291 pte_unmap(pte);
292 return NULL;
295 ptl = pte_lockptr(mm, pmd);
296 spin_lock(ptl);
297 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
298 *ptlp = ptl;
299 return pte;
301 pte_unmap_unlock(pte, ptl);
302 return NULL;
306 * page_mapped_in_vma - check whether a page is really mapped in a VMA
307 * @page: the page to test
308 * @vma: the VMA to test
310 * Returns 1 if the page is mapped into the page tables of the VMA, 0
311 * if the page is not mapped into the page tables of this VMA. Only
312 * valid for normal file or anonymous VMAs.
314 static int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
316 unsigned long address;
317 pte_t *pte;
318 spinlock_t *ptl;
320 address = vma_address(page, vma);
321 if (address == -EFAULT) /* out of vma range */
322 return 0;
323 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
324 if (!pte) /* the page is not in this mm */
325 return 0;
326 pte_unmap_unlock(pte, ptl);
328 return 1;
332 * Subfunctions of page_referenced: page_referenced_one called
333 * repeatedly from either page_referenced_anon or page_referenced_file.
335 static int page_referenced_one(struct page *page,
336 struct vm_area_struct *vma, unsigned int *mapcount)
338 struct mm_struct *mm = vma->vm_mm;
339 unsigned long address;
340 pte_t *pte;
341 spinlock_t *ptl;
342 int referenced = 0;
344 address = vma_address(page, vma);
345 if (address == -EFAULT)
346 goto out;
348 pte = page_check_address(page, mm, address, &ptl, 0);
349 if (!pte)
350 goto out;
353 * Don't want to elevate referenced for mlocked page that gets this far,
354 * in order that it progresses to try_to_unmap and is moved to the
355 * unevictable list.
357 if (vma->vm_flags & VM_LOCKED) {
358 *mapcount = 1; /* break early from loop */
359 goto out_unmap;
362 if (ptep_clear_flush_young_notify(vma, address, pte))
363 referenced++;
365 /* Pretend the page is referenced if the task has the
366 swap token and is in the middle of a page fault. */
367 if (mm != current->mm && has_swap_token(mm) &&
368 rwsem_is_locked(&mm->mmap_sem))
369 referenced++;
371 out_unmap:
372 (*mapcount)--;
373 pte_unmap_unlock(pte, ptl);
374 out:
375 return referenced;
378 static int page_referenced_anon(struct page *page,
379 struct mem_cgroup *mem_cont)
381 unsigned int mapcount;
382 struct anon_vma *anon_vma;
383 struct vm_area_struct *vma;
384 int referenced = 0;
386 anon_vma = page_lock_anon_vma(page);
387 if (!anon_vma)
388 return referenced;
390 mapcount = page_mapcount(page);
391 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
393 * If we are reclaiming on behalf of a cgroup, skip
394 * counting on behalf of references from different
395 * cgroups
397 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
398 continue;
399 referenced += page_referenced_one(page, vma, &mapcount);
400 if (!mapcount)
401 break;
404 page_unlock_anon_vma(anon_vma);
405 return referenced;
409 * page_referenced_file - referenced check for object-based rmap
410 * @page: the page we're checking references on.
411 * @mem_cont: target memory controller
413 * For an object-based mapped page, find all the places it is mapped and
414 * check/clear the referenced flag. This is done by following the page->mapping
415 * pointer, then walking the chain of vmas it holds. It returns the number
416 * of references it found.
418 * This function is only called from page_referenced for object-based pages.
420 static int page_referenced_file(struct page *page,
421 struct mem_cgroup *mem_cont)
423 unsigned int mapcount;
424 struct address_space *mapping = page->mapping;
425 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
426 struct vm_area_struct *vma;
427 struct prio_tree_iter iter;
428 int referenced = 0;
431 * The caller's checks on page->mapping and !PageAnon have made
432 * sure that this is a file page: the check for page->mapping
433 * excludes the case just before it gets set on an anon page.
435 BUG_ON(PageAnon(page));
438 * The page lock not only makes sure that page->mapping cannot
439 * suddenly be NULLified by truncation, it makes sure that the
440 * structure at mapping cannot be freed and reused yet,
441 * so we can safely take mapping->i_mmap_lock.
443 BUG_ON(!PageLocked(page));
445 spin_lock(&mapping->i_mmap_lock);
448 * i_mmap_lock does not stabilize mapcount at all, but mapcount
449 * is more likely to be accurate if we note it after spinning.
451 mapcount = page_mapcount(page);
453 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
455 * If we are reclaiming on behalf of a cgroup, skip
456 * counting on behalf of references from different
457 * cgroups
459 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
460 continue;
461 referenced += page_referenced_one(page, vma, &mapcount);
462 if (!mapcount)
463 break;
466 spin_unlock(&mapping->i_mmap_lock);
467 return referenced;
471 * page_referenced - test if the page was referenced
472 * @page: the page to test
473 * @is_locked: caller holds lock on the page
474 * @mem_cont: target memory controller
476 * Quick test_and_clear_referenced for all mappings to a page,
477 * returns the number of ptes which referenced the page.
479 int page_referenced(struct page *page, int is_locked,
480 struct mem_cgroup *mem_cont)
482 int referenced = 0;
484 if (TestClearPageReferenced(page))
485 referenced++;
487 if (page_mapped(page) && page->mapping) {
488 if (PageAnon(page))
489 referenced += page_referenced_anon(page, mem_cont);
490 else if (is_locked)
491 referenced += page_referenced_file(page, mem_cont);
492 else if (!trylock_page(page))
493 referenced++;
494 else {
495 if (page->mapping)
496 referenced +=
497 page_referenced_file(page, mem_cont);
498 unlock_page(page);
502 if (page_test_and_clear_young(page))
503 referenced++;
505 return referenced;
508 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma)
510 struct mm_struct *mm = vma->vm_mm;
511 unsigned long address;
512 pte_t *pte;
513 spinlock_t *ptl;
514 int ret = 0;
516 address = vma_address(page, vma);
517 if (address == -EFAULT)
518 goto out;
520 pte = page_check_address(page, mm, address, &ptl, 1);
521 if (!pte)
522 goto out;
524 if (pte_dirty(*pte) || pte_write(*pte)) {
525 pte_t entry;
527 flush_cache_page(vma, address, pte_pfn(*pte));
528 entry = ptep_clear_flush_notify(vma, address, pte);
529 entry = pte_wrprotect(entry);
530 entry = pte_mkclean(entry);
531 set_pte_at(mm, address, pte, entry);
532 ret = 1;
535 pte_unmap_unlock(pte, ptl);
536 out:
537 return ret;
540 static int page_mkclean_file(struct address_space *mapping, struct page *page)
542 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
543 struct vm_area_struct *vma;
544 struct prio_tree_iter iter;
545 int ret = 0;
547 BUG_ON(PageAnon(page));
549 spin_lock(&mapping->i_mmap_lock);
550 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
551 if (vma->vm_flags & VM_SHARED)
552 ret += page_mkclean_one(page, vma);
554 spin_unlock(&mapping->i_mmap_lock);
555 return ret;
558 int page_mkclean(struct page *page)
560 int ret = 0;
562 BUG_ON(!PageLocked(page));
564 if (page_mapped(page)) {
565 struct address_space *mapping = page_mapping(page);
566 if (mapping) {
567 ret = page_mkclean_file(mapping, page);
568 if (page_test_dirty(page)) {
569 page_clear_dirty(page);
570 ret = 1;
575 return ret;
577 EXPORT_SYMBOL_GPL(page_mkclean);
580 * __page_set_anon_rmap - setup new anonymous rmap
581 * @page: the page to add the mapping to
582 * @vma: the vm area in which the mapping is added
583 * @address: the user virtual address mapped
585 static void __page_set_anon_rmap(struct page *page,
586 struct vm_area_struct *vma, unsigned long address)
588 struct anon_vma *anon_vma = vma->anon_vma;
590 BUG_ON(!anon_vma);
591 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
592 page->mapping = (struct address_space *) anon_vma;
594 page->index = linear_page_index(vma, address);
597 * nr_mapped state can be updated without turning off
598 * interrupts because it is not modified via interrupt.
600 __inc_zone_page_state(page, NR_ANON_PAGES);
604 * __page_check_anon_rmap - sanity check anonymous rmap addition
605 * @page: the page to add the mapping to
606 * @vma: the vm area in which the mapping is added
607 * @address: the user virtual address mapped
609 static void __page_check_anon_rmap(struct page *page,
610 struct vm_area_struct *vma, unsigned long address)
612 #ifdef CONFIG_DEBUG_VM
614 * The page's anon-rmap details (mapping and index) are guaranteed to
615 * be set up correctly at this point.
617 * We have exclusion against page_add_anon_rmap because the caller
618 * always holds the page locked, except if called from page_dup_rmap,
619 * in which case the page is already known to be setup.
621 * We have exclusion against page_add_new_anon_rmap because those pages
622 * are initially only visible via the pagetables, and the pte is locked
623 * over the call to page_add_new_anon_rmap.
625 struct anon_vma *anon_vma = vma->anon_vma;
626 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
627 BUG_ON(page->mapping != (struct address_space *)anon_vma);
628 BUG_ON(page->index != linear_page_index(vma, address));
629 #endif
633 * page_add_anon_rmap - add pte mapping to an anonymous page
634 * @page: the page to add the mapping to
635 * @vma: the vm area in which the mapping is added
636 * @address: the user virtual address mapped
638 * The caller needs to hold the pte lock and the page must be locked.
640 void page_add_anon_rmap(struct page *page,
641 struct vm_area_struct *vma, unsigned long address)
643 VM_BUG_ON(!PageLocked(page));
644 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
645 if (atomic_inc_and_test(&page->_mapcount))
646 __page_set_anon_rmap(page, vma, address);
647 else
648 __page_check_anon_rmap(page, vma, address);
652 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
653 * @page: the page to add the mapping to
654 * @vma: the vm area in which the mapping is added
655 * @address: the user virtual address mapped
657 * Same as page_add_anon_rmap but must only be called on *new* pages.
658 * This means the inc-and-test can be bypassed.
659 * Page does not have to be locked.
661 void page_add_new_anon_rmap(struct page *page,
662 struct vm_area_struct *vma, unsigned long address)
664 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
665 atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
666 __page_set_anon_rmap(page, vma, address);
670 * page_add_file_rmap - add pte mapping to a file page
671 * @page: the page to add the mapping to
673 * The caller needs to hold the pte lock.
675 void page_add_file_rmap(struct page *page)
677 if (atomic_inc_and_test(&page->_mapcount))
678 __inc_zone_page_state(page, NR_FILE_MAPPED);
681 #ifdef CONFIG_DEBUG_VM
683 * page_dup_rmap - duplicate pte mapping to a page
684 * @page: the page to add the mapping to
685 * @vma: the vm area being duplicated
686 * @address: the user virtual address mapped
688 * For copy_page_range only: minimal extract from page_add_file_rmap /
689 * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
690 * quicker.
692 * The caller needs to hold the pte lock.
694 void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
696 BUG_ON(page_mapcount(page) == 0);
697 if (PageAnon(page))
698 __page_check_anon_rmap(page, vma, address);
699 atomic_inc(&page->_mapcount);
701 #endif
704 * page_remove_rmap - take down pte mapping from a page
705 * @page: page to remove mapping from
706 * @vma: the vm area in which the mapping is removed
708 * The caller needs to hold the pte lock.
710 void page_remove_rmap(struct page *page, struct vm_area_struct *vma)
712 if (atomic_add_negative(-1, &page->_mapcount)) {
713 if (unlikely(page_mapcount(page) < 0)) {
714 printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
715 printk (KERN_EMERG " page pfn = %lx\n", page_to_pfn(page));
716 printk (KERN_EMERG " page->flags = %lx\n", page->flags);
717 printk (KERN_EMERG " page->count = %x\n", page_count(page));
718 printk (KERN_EMERG " page->mapping = %p\n", page->mapping);
719 print_symbol (KERN_EMERG " vma->vm_ops = %s\n", (unsigned long)vma->vm_ops);
720 if (vma->vm_ops) {
721 print_symbol (KERN_EMERG " vma->vm_ops->fault = %s\n", (unsigned long)vma->vm_ops->fault);
723 if (vma->vm_file && vma->vm_file->f_op)
724 print_symbol (KERN_EMERG " vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma->vm_file->f_op->mmap);
725 BUG();
729 * Now that the last pte has gone, s390 must transfer dirty
730 * flag from storage key to struct page. We can usually skip
731 * this if the page is anon, so about to be freed; but perhaps
732 * not if it's in swapcache - there might be another pte slot
733 * containing the swap entry, but page not yet written to swap.
735 if ((!PageAnon(page) || PageSwapCache(page)) &&
736 page_test_dirty(page)) {
737 page_clear_dirty(page);
738 set_page_dirty(page);
740 if (PageAnon(page))
741 mem_cgroup_uncharge_page(page);
742 __dec_zone_page_state(page,
743 PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
745 * It would be tidy to reset the PageAnon mapping here,
746 * but that might overwrite a racing page_add_anon_rmap
747 * which increments mapcount after us but sets mapping
748 * before us: so leave the reset to free_hot_cold_page,
749 * and remember that it's only reliable while mapped.
750 * Leaving it set also helps swapoff to reinstate ptes
751 * faster for those pages still in swapcache.
757 * Subfunctions of try_to_unmap: try_to_unmap_one called
758 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
760 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
761 int migration)
763 struct mm_struct *mm = vma->vm_mm;
764 unsigned long address;
765 pte_t *pte;
766 pte_t pteval;
767 spinlock_t *ptl;
768 int ret = SWAP_AGAIN;
770 address = vma_address(page, vma);
771 if (address == -EFAULT)
772 goto out;
774 pte = page_check_address(page, mm, address, &ptl, 0);
775 if (!pte)
776 goto out;
779 * If the page is mlock()d, we cannot swap it out.
780 * If it's recently referenced (perhaps page_referenced
781 * skipped over this mm) then we should reactivate it.
783 if (!migration) {
784 if (vma->vm_flags & VM_LOCKED) {
785 ret = SWAP_MLOCK;
786 goto out_unmap;
788 if (ptep_clear_flush_young_notify(vma, address, pte)) {
789 ret = SWAP_FAIL;
790 goto out_unmap;
794 /* Nuke the page table entry. */
795 flush_cache_page(vma, address, page_to_pfn(page));
796 pteval = ptep_clear_flush_notify(vma, address, pte);
798 /* Move the dirty bit to the physical page now the pte is gone. */
799 if (pte_dirty(pteval))
800 set_page_dirty(page);
802 /* Update high watermark before we lower rss */
803 update_hiwater_rss(mm);
805 if (PageAnon(page)) {
806 swp_entry_t entry = { .val = page_private(page) };
808 if (PageSwapCache(page)) {
810 * Store the swap location in the pte.
811 * See handle_pte_fault() ...
813 swap_duplicate(entry);
814 if (list_empty(&mm->mmlist)) {
815 spin_lock(&mmlist_lock);
816 if (list_empty(&mm->mmlist))
817 list_add(&mm->mmlist, &init_mm.mmlist);
818 spin_unlock(&mmlist_lock);
820 dec_mm_counter(mm, anon_rss);
821 #ifdef CONFIG_MIGRATION
822 } else {
824 * Store the pfn of the page in a special migration
825 * pte. do_swap_page() will wait until the migration
826 * pte is removed and then restart fault handling.
828 BUG_ON(!migration);
829 entry = make_migration_entry(page, pte_write(pteval));
830 #endif
832 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
833 BUG_ON(pte_file(*pte));
834 } else
835 #ifdef CONFIG_MIGRATION
836 if (migration) {
837 /* Establish migration entry for a file page */
838 swp_entry_t entry;
839 entry = make_migration_entry(page, pte_write(pteval));
840 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
841 } else
842 #endif
843 dec_mm_counter(mm, file_rss);
846 page_remove_rmap(page, vma);
847 page_cache_release(page);
849 out_unmap:
850 pte_unmap_unlock(pte, ptl);
851 out:
852 return ret;
856 * objrmap doesn't work for nonlinear VMAs because the assumption that
857 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
858 * Consequently, given a particular page and its ->index, we cannot locate the
859 * ptes which are mapping that page without an exhaustive linear search.
861 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
862 * maps the file to which the target page belongs. The ->vm_private_data field
863 * holds the current cursor into that scan. Successive searches will circulate
864 * around the vma's virtual address space.
866 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
867 * more scanning pressure is placed against them as well. Eventually pages
868 * will become fully unmapped and are eligible for eviction.
870 * For very sparsely populated VMAs this is a little inefficient - chances are
871 * there there won't be many ptes located within the scan cluster. In this case
872 * maybe we could scan further - to the end of the pte page, perhaps.
874 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
875 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
876 * rather than unmapping them. If we encounter the "check_page" that vmscan is
877 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
879 #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
880 #define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
882 static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
883 struct vm_area_struct *vma, struct page *check_page)
885 struct mm_struct *mm = vma->vm_mm;
886 pgd_t *pgd;
887 pud_t *pud;
888 pmd_t *pmd;
889 pte_t *pte;
890 pte_t pteval;
891 spinlock_t *ptl;
892 struct page *page;
893 unsigned long address;
894 unsigned long end;
895 int ret = SWAP_AGAIN;
896 int locked_vma = 0;
898 address = (vma->vm_start + cursor) & CLUSTER_MASK;
899 end = address + CLUSTER_SIZE;
900 if (address < vma->vm_start)
901 address = vma->vm_start;
902 if (end > vma->vm_end)
903 end = vma->vm_end;
905 pgd = pgd_offset(mm, address);
906 if (!pgd_present(*pgd))
907 return ret;
909 pud = pud_offset(pgd, address);
910 if (!pud_present(*pud))
911 return ret;
913 pmd = pmd_offset(pud, address);
914 if (!pmd_present(*pmd))
915 return ret;
918 * MLOCK_PAGES => feature is configured.
919 * if we can acquire the mmap_sem for read, and vma is VM_LOCKED,
920 * keep the sem while scanning the cluster for mlocking pages.
922 if (MLOCK_PAGES && down_read_trylock(&vma->vm_mm->mmap_sem)) {
923 locked_vma = (vma->vm_flags & VM_LOCKED);
924 if (!locked_vma)
925 up_read(&vma->vm_mm->mmap_sem); /* don't need it */
928 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
930 /* Update high watermark before we lower rss */
931 update_hiwater_rss(mm);
933 for (; address < end; pte++, address += PAGE_SIZE) {
934 if (!pte_present(*pte))
935 continue;
936 page = vm_normal_page(vma, address, *pte);
937 BUG_ON(!page || PageAnon(page));
939 if (locked_vma) {
940 mlock_vma_page(page); /* no-op if already mlocked */
941 if (page == check_page)
942 ret = SWAP_MLOCK;
943 continue; /* don't unmap */
946 if (ptep_clear_flush_young_notify(vma, address, pte))
947 continue;
949 /* Nuke the page table entry. */
950 flush_cache_page(vma, address, pte_pfn(*pte));
951 pteval = ptep_clear_flush_notify(vma, address, pte);
953 /* If nonlinear, store the file page offset in the pte. */
954 if (page->index != linear_page_index(vma, address))
955 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
957 /* Move the dirty bit to the physical page now the pte is gone. */
958 if (pte_dirty(pteval))
959 set_page_dirty(page);
961 page_remove_rmap(page, vma);
962 page_cache_release(page);
963 dec_mm_counter(mm, file_rss);
964 (*mapcount)--;
966 pte_unmap_unlock(pte - 1, ptl);
967 if (locked_vma)
968 up_read(&vma->vm_mm->mmap_sem);
969 return ret;
973 * common handling for pages mapped in VM_LOCKED vmas
975 static int try_to_mlock_page(struct page *page, struct vm_area_struct *vma)
977 int mlocked = 0;
979 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
980 if (vma->vm_flags & VM_LOCKED) {
981 mlock_vma_page(page);
982 mlocked++; /* really mlocked the page */
984 up_read(&vma->vm_mm->mmap_sem);
986 return mlocked;
990 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
991 * rmap method
992 * @page: the page to unmap/unlock
993 * @unlock: request for unlock rather than unmap [unlikely]
994 * @migration: unmapping for migration - ignored if @unlock
996 * Find all the mappings of a page using the mapping pointer and the vma chains
997 * contained in the anon_vma struct it points to.
999 * This function is only called from try_to_unmap/try_to_munlock for
1000 * anonymous pages.
1001 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1002 * where the page was found will be held for write. So, we won't recheck
1003 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1004 * 'LOCKED.
1006 static int try_to_unmap_anon(struct page *page, int unlock, int migration)
1008 struct anon_vma *anon_vma;
1009 struct vm_area_struct *vma;
1010 unsigned int mlocked = 0;
1011 int ret = SWAP_AGAIN;
1013 if (MLOCK_PAGES && unlikely(unlock))
1014 ret = SWAP_SUCCESS; /* default for try_to_munlock() */
1016 anon_vma = page_lock_anon_vma(page);
1017 if (!anon_vma)
1018 return ret;
1020 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
1021 if (MLOCK_PAGES && unlikely(unlock)) {
1022 if (!((vma->vm_flags & VM_LOCKED) &&
1023 page_mapped_in_vma(page, vma)))
1024 continue; /* must visit all unlocked vmas */
1025 ret = SWAP_MLOCK; /* saw at least one mlocked vma */
1026 } else {
1027 ret = try_to_unmap_one(page, vma, migration);
1028 if (ret == SWAP_FAIL || !page_mapped(page))
1029 break;
1031 if (ret == SWAP_MLOCK) {
1032 mlocked = try_to_mlock_page(page, vma);
1033 if (mlocked)
1034 break; /* stop if actually mlocked page */
1038 page_unlock_anon_vma(anon_vma);
1040 if (mlocked)
1041 ret = SWAP_MLOCK; /* actually mlocked the page */
1042 else if (ret == SWAP_MLOCK)
1043 ret = SWAP_AGAIN; /* saw VM_LOCKED vma */
1045 return ret;
1049 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1050 * @page: the page to unmap/unlock
1051 * @unlock: request for unlock rather than unmap [unlikely]
1052 * @migration: unmapping for migration - ignored if @unlock
1054 * Find all the mappings of a page using the mapping pointer and the vma chains
1055 * contained in the address_space struct it points to.
1057 * This function is only called from try_to_unmap/try_to_munlock for
1058 * object-based pages.
1059 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1060 * where the page was found will be held for write. So, we won't recheck
1061 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1062 * 'LOCKED.
1064 static int try_to_unmap_file(struct page *page, int unlock, int migration)
1066 struct address_space *mapping = page->mapping;
1067 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1068 struct vm_area_struct *vma;
1069 struct prio_tree_iter iter;
1070 int ret = SWAP_AGAIN;
1071 unsigned long cursor;
1072 unsigned long max_nl_cursor = 0;
1073 unsigned long max_nl_size = 0;
1074 unsigned int mapcount;
1075 unsigned int mlocked = 0;
1077 if (MLOCK_PAGES && unlikely(unlock))
1078 ret = SWAP_SUCCESS; /* default for try_to_munlock() */
1080 spin_lock(&mapping->i_mmap_lock);
1081 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1082 if (MLOCK_PAGES && unlikely(unlock)) {
1083 if (!(vma->vm_flags & VM_LOCKED))
1084 continue; /* must visit all vmas */
1085 ret = SWAP_MLOCK;
1086 } else {
1087 ret = try_to_unmap_one(page, vma, migration);
1088 if (ret == SWAP_FAIL || !page_mapped(page))
1089 goto out;
1091 if (ret == SWAP_MLOCK) {
1092 mlocked = try_to_mlock_page(page, vma);
1093 if (mlocked)
1094 break; /* stop if actually mlocked page */
1098 if (mlocked)
1099 goto out;
1101 if (list_empty(&mapping->i_mmap_nonlinear))
1102 goto out;
1104 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1105 shared.vm_set.list) {
1106 if (MLOCK_PAGES && unlikely(unlock)) {
1107 if (!(vma->vm_flags & VM_LOCKED))
1108 continue; /* must visit all vmas */
1109 ret = SWAP_MLOCK; /* leave mlocked == 0 */
1110 goto out; /* no need to look further */
1112 if (!MLOCK_PAGES && !migration && (vma->vm_flags & VM_LOCKED))
1113 continue;
1114 cursor = (unsigned long) vma->vm_private_data;
1115 if (cursor > max_nl_cursor)
1116 max_nl_cursor = cursor;
1117 cursor = vma->vm_end - vma->vm_start;
1118 if (cursor > max_nl_size)
1119 max_nl_size = cursor;
1122 if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
1123 ret = SWAP_FAIL;
1124 goto out;
1128 * We don't try to search for this page in the nonlinear vmas,
1129 * and page_referenced wouldn't have found it anyway. Instead
1130 * just walk the nonlinear vmas trying to age and unmap some.
1131 * The mapcount of the page we came in with is irrelevant,
1132 * but even so use it as a guide to how hard we should try?
1134 mapcount = page_mapcount(page);
1135 if (!mapcount)
1136 goto out;
1137 cond_resched_lock(&mapping->i_mmap_lock);
1139 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1140 if (max_nl_cursor == 0)
1141 max_nl_cursor = CLUSTER_SIZE;
1143 do {
1144 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1145 shared.vm_set.list) {
1146 if (!MLOCK_PAGES && !migration &&
1147 (vma->vm_flags & VM_LOCKED))
1148 continue;
1149 cursor = (unsigned long) vma->vm_private_data;
1150 while ( cursor < max_nl_cursor &&
1151 cursor < vma->vm_end - vma->vm_start) {
1152 ret = try_to_unmap_cluster(cursor, &mapcount,
1153 vma, page);
1154 if (ret == SWAP_MLOCK)
1155 mlocked = 2; /* to return below */
1156 cursor += CLUSTER_SIZE;
1157 vma->vm_private_data = (void *) cursor;
1158 if ((int)mapcount <= 0)
1159 goto out;
1161 vma->vm_private_data = (void *) max_nl_cursor;
1163 cond_resched_lock(&mapping->i_mmap_lock);
1164 max_nl_cursor += CLUSTER_SIZE;
1165 } while (max_nl_cursor <= max_nl_size);
1168 * Don't loop forever (perhaps all the remaining pages are
1169 * in locked vmas). Reset cursor on all unreserved nonlinear
1170 * vmas, now forgetting on which ones it had fallen behind.
1172 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
1173 vma->vm_private_data = NULL;
1174 out:
1175 spin_unlock(&mapping->i_mmap_lock);
1176 if (mlocked)
1177 ret = SWAP_MLOCK; /* actually mlocked the page */
1178 else if (ret == SWAP_MLOCK)
1179 ret = SWAP_AGAIN; /* saw VM_LOCKED vma */
1180 return ret;
1184 * try_to_unmap - try to remove all page table mappings to a page
1185 * @page: the page to get unmapped
1186 * @migration: migration flag
1188 * Tries to remove all the page table entries which are mapping this
1189 * page, used in the pageout path. Caller must hold the page lock.
1190 * Return values are:
1192 * SWAP_SUCCESS - we succeeded in removing all mappings
1193 * SWAP_AGAIN - we missed a mapping, try again later
1194 * SWAP_FAIL - the page is unswappable
1195 * SWAP_MLOCK - page is mlocked.
1197 int try_to_unmap(struct page *page, int migration)
1199 int ret;
1201 BUG_ON(!PageLocked(page));
1203 if (PageAnon(page))
1204 ret = try_to_unmap_anon(page, 0, migration);
1205 else
1206 ret = try_to_unmap_file(page, 0, migration);
1207 if (ret != SWAP_MLOCK && !page_mapped(page))
1208 ret = SWAP_SUCCESS;
1209 return ret;
1212 #ifdef CONFIG_UNEVICTABLE_LRU
1214 * try_to_munlock - try to munlock a page
1215 * @page: the page to be munlocked
1217 * Called from munlock code. Checks all of the VMAs mapping the page
1218 * to make sure nobody else has this page mlocked. The page will be
1219 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1221 * Return values are:
1223 * SWAP_SUCCESS - no vma's holding page mlocked.
1224 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
1225 * SWAP_MLOCK - page is now mlocked.
1227 int try_to_munlock(struct page *page)
1229 VM_BUG_ON(!PageLocked(page) || PageLRU(page));
1231 if (PageAnon(page))
1232 return try_to_unmap_anon(page, 1, 0);
1233 else
1234 return try_to_unmap_file(page, 1, 0);
1236 #endif