blob: 914d04b98beee0aca9e52eada3b52db6307c7b30 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * mm/rmap.c - physical to virtual reverse mappings
3 *
4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5 * Released under the General Public License (GPL).
6 *
7 * Simple, low overhead reverse mapping scheme.
8 * Please try to keep this thing as modular as possible.
9 *
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.
13 *
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
18 */
19
20/*
21 * Lock ordering in mm:
22 *
23 * inode->i_sem (while writing or truncating, not reading or faulting)
24 * inode->i_alloc_sem
25 *
26 * When a page fault occurs in writing from user to file, down_read
27 * of mmap_sem nests within i_sem; in sys_msync, i_sem nests within
28 * down_read of mmap_sem; i_sem and down_write of mmap_sem are never
29 * taken together; in truncation, i_sem is taken outermost.
30 *
31 * mm->mmap_sem
32 * page->flags PG_locked (lock_page)
33 * mapping->i_mmap_lock
34 * anon_vma->lock
Hugh Dickinsb8072f02005-10-29 18:16:41 -070035 * mm->page_table_lock or pte_lock
Linus Torvalds1da177e2005-04-16 15:20:36 -070036 * zone->lru_lock (in mark_page_accessed)
Hugh Dickins5d337b92005-09-03 15:54:41 -070037 * swap_lock (in swap_duplicate, swap_info_get)
Linus Torvalds1da177e2005-04-16 15:20:36 -070038 * mmlist_lock (in mmput, drain_mmlist and others)
Linus Torvalds1da177e2005-04-16 15:20:36 -070039 * mapping->private_lock (in __set_page_dirty_buffers)
40 * inode_lock (in set_page_dirty's __mark_inode_dirty)
41 * sb_lock (within inode_lock in fs/fs-writeback.c)
42 * mapping->tree_lock (widely used, in set_page_dirty,
43 * in arch-dependent flush_dcache_mmap_lock,
44 * within inode_lock in __sync_single_inode)
45 */
46
47#include <linux/mm.h>
48#include <linux/pagemap.h>
49#include <linux/swap.h>
50#include <linux/swapops.h>
51#include <linux/slab.h>
52#include <linux/init.h>
53#include <linux/rmap.h>
54#include <linux/rcupdate.h>
55
56#include <asm/tlbflush.h>
57
58//#define RMAP_DEBUG /* can be enabled only for debugging */
59
60kmem_cache_t *anon_vma_cachep;
61
62static inline void validate_anon_vma(struct vm_area_struct *find_vma)
63{
64#ifdef RMAP_DEBUG
65 struct anon_vma *anon_vma = find_vma->anon_vma;
66 struct vm_area_struct *vma;
67 unsigned int mapcount = 0;
68 int found = 0;
69
70 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
71 mapcount++;
72 BUG_ON(mapcount > 100000);
73 if (vma == find_vma)
74 found = 1;
75 }
76 BUG_ON(!found);
77#endif
78}
79
80/* This must be called under the mmap_sem. */
81int anon_vma_prepare(struct vm_area_struct *vma)
82{
83 struct anon_vma *anon_vma = vma->anon_vma;
84
85 might_sleep();
86 if (unlikely(!anon_vma)) {
87 struct mm_struct *mm = vma->vm_mm;
88 struct anon_vma *allocated, *locked;
89
90 anon_vma = find_mergeable_anon_vma(vma);
91 if (anon_vma) {
92 allocated = NULL;
93 locked = anon_vma;
94 spin_lock(&locked->lock);
95 } else {
96 anon_vma = anon_vma_alloc();
97 if (unlikely(!anon_vma))
98 return -ENOMEM;
99 allocated = anon_vma;
100 locked = NULL;
101 }
102
103 /* page_table_lock to protect against threads */
104 spin_lock(&mm->page_table_lock);
105 if (likely(!vma->anon_vma)) {
106 vma->anon_vma = anon_vma;
107 list_add(&vma->anon_vma_node, &anon_vma->head);
108 allocated = NULL;
109 }
110 spin_unlock(&mm->page_table_lock);
111
112 if (locked)
113 spin_unlock(&locked->lock);
114 if (unlikely(allocated))
115 anon_vma_free(allocated);
116 }
117 return 0;
118}
119
120void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
121{
122 BUG_ON(vma->anon_vma != next->anon_vma);
123 list_del(&next->anon_vma_node);
124}
125
126void __anon_vma_link(struct vm_area_struct *vma)
127{
128 struct anon_vma *anon_vma = vma->anon_vma;
129
130 if (anon_vma) {
131 list_add(&vma->anon_vma_node, &anon_vma->head);
132 validate_anon_vma(vma);
133 }
134}
135
136void anon_vma_link(struct vm_area_struct *vma)
137{
138 struct anon_vma *anon_vma = vma->anon_vma;
139
140 if (anon_vma) {
141 spin_lock(&anon_vma->lock);
142 list_add(&vma->anon_vma_node, &anon_vma->head);
143 validate_anon_vma(vma);
144 spin_unlock(&anon_vma->lock);
145 }
146}
147
148void anon_vma_unlink(struct vm_area_struct *vma)
149{
150 struct anon_vma *anon_vma = vma->anon_vma;
151 int empty;
152
153 if (!anon_vma)
154 return;
155
156 spin_lock(&anon_vma->lock);
157 validate_anon_vma(vma);
158 list_del(&vma->anon_vma_node);
159
160 /* We must garbage collect the anon_vma if it's empty */
161 empty = list_empty(&anon_vma->head);
162 spin_unlock(&anon_vma->lock);
163
164 if (empty)
165 anon_vma_free(anon_vma);
166}
167
168static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
169{
170 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
171 SLAB_CTOR_CONSTRUCTOR) {
172 struct anon_vma *anon_vma = data;
173
174 spin_lock_init(&anon_vma->lock);
175 INIT_LIST_HEAD(&anon_vma->head);
176 }
177}
178
179void __init anon_vma_init(void)
180{
181 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
182 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
183}
184
185/*
186 * Getting a lock on a stable anon_vma from a page off the LRU is
187 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
188 */
189static struct anon_vma *page_lock_anon_vma(struct page *page)
190{
191 struct anon_vma *anon_vma = NULL;
192 unsigned long anon_mapping;
193
194 rcu_read_lock();
195 anon_mapping = (unsigned long) page->mapping;
196 if (!(anon_mapping & PAGE_MAPPING_ANON))
197 goto out;
198 if (!page_mapped(page))
199 goto out;
200
201 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
202 spin_lock(&anon_vma->lock);
203out:
204 rcu_read_unlock();
205 return anon_vma;
206}
207
208/*
209 * At what user virtual address is page expected in vma?
210 */
211static inline unsigned long
212vma_address(struct page *page, struct vm_area_struct *vma)
213{
214 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
215 unsigned long address;
216
217 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
218 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
219 /* page should be within any vma from prio_tree_next */
220 BUG_ON(!PageAnon(page));
221 return -EFAULT;
222 }
223 return address;
224}
225
226/*
227 * At what user virtual address is page expected in vma? checking that the
228 * page matches the vma: currently only used by unuse_process, on anon pages.
229 */
230unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
231{
232 if (PageAnon(page)) {
233 if ((void *)vma->anon_vma !=
234 (void *)page->mapping - PAGE_MAPPING_ANON)
235 return -EFAULT;
236 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
237 if (vma->vm_file->f_mapping != page->mapping)
238 return -EFAULT;
239 } else
240 return -EFAULT;
241 return vma_address(page, vma);
242}
243
244/*
Nikita Danilov81b40822005-05-01 08:58:36 -0700245 * Check that @page is mapped at @address into @mm.
246 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700247 * On success returns with pte mapped and locked.
Nikita Danilov81b40822005-05-01 08:58:36 -0700248 */
Carsten Otteceffc072005-06-23 22:05:25 -0700249pte_t *page_check_address(struct page *page, struct mm_struct *mm,
Hugh Dickinsc0718802005-10-29 18:16:31 -0700250 unsigned long address, spinlock_t **ptlp)
Nikita Danilov81b40822005-05-01 08:58:36 -0700251{
252 pgd_t *pgd;
253 pud_t *pud;
254 pmd_t *pmd;
255 pte_t *pte;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700256 spinlock_t *ptl;
Nikita Danilov81b40822005-05-01 08:58:36 -0700257
Nikita Danilov81b40822005-05-01 08:58:36 -0700258 pgd = pgd_offset(mm, address);
Hugh Dickinsc0718802005-10-29 18:16:31 -0700259 if (!pgd_present(*pgd))
260 return NULL;
261
262 pud = pud_offset(pgd, address);
263 if (!pud_present(*pud))
264 return NULL;
265
266 pmd = pmd_offset(pud, address);
267 if (!pmd_present(*pmd))
268 return NULL;
269
270 pte = pte_offset_map(pmd, address);
271 /* Make a quick check before getting the lock */
272 if (!pte_present(*pte)) {
273 pte_unmap(pte);
274 return NULL;
Nikita Danilov81b40822005-05-01 08:58:36 -0700275 }
Hugh Dickinsc0718802005-10-29 18:16:31 -0700276
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700277 ptl = pte_lockptr(mm, pmd);
Hugh Dickinsc0718802005-10-29 18:16:31 -0700278 spin_lock(ptl);
279 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
280 *ptlp = ptl;
281 return pte;
282 }
283 pte_unmap_unlock(pte, ptl);
284 return NULL;
Nikita Danilov81b40822005-05-01 08:58:36 -0700285}
286
287/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 * Subfunctions of page_referenced: page_referenced_one called
289 * repeatedly from either page_referenced_anon or page_referenced_file.
290 */
291static int page_referenced_one(struct page *page,
292 struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token)
293{
294 struct mm_struct *mm = vma->vm_mm;
295 unsigned long address;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296 pte_t *pte;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700297 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298 int referenced = 0;
299
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300 address = vma_address(page, vma);
301 if (address == -EFAULT)
302 goto out;
303
Hugh Dickinsc0718802005-10-29 18:16:31 -0700304 pte = page_check_address(page, mm, address, &ptl);
305 if (!pte)
306 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307
Hugh Dickinsc0718802005-10-29 18:16:31 -0700308 if (ptep_clear_flush_young(vma, address, pte))
309 referenced++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310
Hugh Dickinsc0718802005-10-29 18:16:31 -0700311 /* Pretend the page is referenced if the task has the
312 swap token and is in the middle of a page fault. */
313 if (mm != current->mm && !ignore_token && has_swap_token(mm) &&
314 rwsem_is_locked(&mm->mmap_sem))
315 referenced++;
316
317 (*mapcount)--;
318 pte_unmap_unlock(pte, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319out:
320 return referenced;
321}
322
323static int page_referenced_anon(struct page *page, int ignore_token)
324{
325 unsigned int mapcount;
326 struct anon_vma *anon_vma;
327 struct vm_area_struct *vma;
328 int referenced = 0;
329
330 anon_vma = page_lock_anon_vma(page);
331 if (!anon_vma)
332 return referenced;
333
334 mapcount = page_mapcount(page);
335 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
336 referenced += page_referenced_one(page, vma, &mapcount,
337 ignore_token);
338 if (!mapcount)
339 break;
340 }
341 spin_unlock(&anon_vma->lock);
342 return referenced;
343}
344
345/**
346 * page_referenced_file - referenced check for object-based rmap
347 * @page: the page we're checking references on.
348 *
349 * For an object-based mapped page, find all the places it is mapped and
350 * check/clear the referenced flag. This is done by following the page->mapping
351 * pointer, then walking the chain of vmas it holds. It returns the number
352 * of references it found.
353 *
354 * This function is only called from page_referenced for object-based pages.
355 */
356static int page_referenced_file(struct page *page, int ignore_token)
357{
358 unsigned int mapcount;
359 struct address_space *mapping = page->mapping;
360 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
361 struct vm_area_struct *vma;
362 struct prio_tree_iter iter;
363 int referenced = 0;
364
365 /*
366 * The caller's checks on page->mapping and !PageAnon have made
367 * sure that this is a file page: the check for page->mapping
368 * excludes the case just before it gets set on an anon page.
369 */
370 BUG_ON(PageAnon(page));
371
372 /*
373 * The page lock not only makes sure that page->mapping cannot
374 * suddenly be NULLified by truncation, it makes sure that the
375 * structure at mapping cannot be freed and reused yet,
376 * so we can safely take mapping->i_mmap_lock.
377 */
378 BUG_ON(!PageLocked(page));
379
380 spin_lock(&mapping->i_mmap_lock);
381
382 /*
383 * i_mmap_lock does not stabilize mapcount at all, but mapcount
384 * is more likely to be accurate if we note it after spinning.
385 */
386 mapcount = page_mapcount(page);
387
388 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
389 if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
390 == (VM_LOCKED|VM_MAYSHARE)) {
391 referenced++;
392 break;
393 }
394 referenced += page_referenced_one(page, vma, &mapcount,
395 ignore_token);
396 if (!mapcount)
397 break;
398 }
399
400 spin_unlock(&mapping->i_mmap_lock);
401 return referenced;
402}
403
404/**
405 * page_referenced - test if the page was referenced
406 * @page: the page to test
407 * @is_locked: caller holds lock on the page
408 *
409 * Quick test_and_clear_referenced for all mappings to a page,
410 * returns the number of ptes which referenced the page.
411 */
412int page_referenced(struct page *page, int is_locked, int ignore_token)
413{
414 int referenced = 0;
415
416 if (!swap_token_default_timeout)
417 ignore_token = 1;
418
419 if (page_test_and_clear_young(page))
420 referenced++;
421
422 if (TestClearPageReferenced(page))
423 referenced++;
424
425 if (page_mapped(page) && page->mapping) {
426 if (PageAnon(page))
427 referenced += page_referenced_anon(page, ignore_token);
428 else if (is_locked)
429 referenced += page_referenced_file(page, ignore_token);
430 else if (TestSetPageLocked(page))
431 referenced++;
432 else {
433 if (page->mapping)
434 referenced += page_referenced_file(page,
435 ignore_token);
436 unlock_page(page);
437 }
438 }
439 return referenced;
440}
441
442/**
443 * page_add_anon_rmap - add pte mapping to an anonymous page
444 * @page: the page to add the mapping to
445 * @vma: the vm area in which the mapping is added
446 * @address: the user virtual address mapped
447 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700448 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 */
450void page_add_anon_rmap(struct page *page,
451 struct vm_area_struct *vma, unsigned long address)
452{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700453 if (atomic_inc_and_test(&page->_mapcount)) {
Nick Piggin2822c1a2005-09-03 15:54:47 -0700454 struct anon_vma *anon_vma = vma->anon_vma;
Nick Piggin2822c1a2005-09-03 15:54:47 -0700455
456 BUG_ON(!anon_vma);
457 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 page->mapping = (struct address_space *) anon_vma;
Nick Piggin2822c1a2005-09-03 15:54:47 -0700459
Nick Piggin4d7670e2005-09-03 15:54:48 -0700460 page->index = linear_page_index(vma, address);
Nick Piggin2822c1a2005-09-03 15:54:47 -0700461
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462 inc_page_state(nr_mapped);
463 }
464 /* else checking page index and mapping is racy */
465}
466
467/**
468 * page_add_file_rmap - add pte mapping to a file page
469 * @page: the page to add the mapping to
470 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700471 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 */
473void page_add_file_rmap(struct page *page)
474{
475 BUG_ON(PageAnon(page));
Nick Pigginb5810032005-10-29 18:16:12 -0700476 BUG_ON(!pfn_valid(page_to_pfn(page)));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477
478 if (atomic_inc_and_test(&page->_mapcount))
479 inc_page_state(nr_mapped);
480}
481
482/**
483 * page_remove_rmap - take down pte mapping from a page
484 * @page: page to remove mapping from
485 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700486 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487 */
488void page_remove_rmap(struct page *page)
489{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 if (atomic_add_negative(-1, &page->_mapcount)) {
491 BUG_ON(page_mapcount(page) < 0);
492 /*
493 * It would be tidy to reset the PageAnon mapping here,
494 * but that might overwrite a racing page_add_anon_rmap
495 * which increments mapcount after us but sets mapping
496 * before us: so leave the reset to free_hot_cold_page,
497 * and remember that it's only reliable while mapped.
498 * Leaving it set also helps swapoff to reinstate ptes
499 * faster for those pages still in swapcache.
500 */
501 if (page_test_and_clear_dirty(page))
502 set_page_dirty(page);
503 dec_page_state(nr_mapped);
504 }
505}
506
507/*
508 * Subfunctions of try_to_unmap: try_to_unmap_one called
509 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
510 */
511static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
512{
513 struct mm_struct *mm = vma->vm_mm;
514 unsigned long address;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 pte_t *pte;
516 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700517 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518 int ret = SWAP_AGAIN;
519
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 address = vma_address(page, vma);
521 if (address == -EFAULT)
522 goto out;
523
Hugh Dickinsc0718802005-10-29 18:16:31 -0700524 pte = page_check_address(page, mm, address, &ptl);
525 if (!pte)
Nikita Danilov81b40822005-05-01 08:58:36 -0700526 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527
528 /*
529 * If the page is mlock()d, we cannot swap it out.
530 * If it's recently referenced (perhaps page_referenced
531 * skipped over this mm) then we should reactivate it.
Nick Pigginc3dce2d2005-09-03 15:54:46 -0700532 *
533 * Pages belonging to VM_RESERVED regions should not happen here.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700534 */
535 if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
536 ptep_clear_flush_young(vma, address, pte)) {
537 ret = SWAP_FAIL;
538 goto out_unmap;
539 }
540
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 /* Nuke the page table entry. */
542 flush_cache_page(vma, address, page_to_pfn(page));
543 pteval = ptep_clear_flush(vma, address, pte);
544
545 /* Move the dirty bit to the physical page now the pte is gone. */
546 if (pte_dirty(pteval))
547 set_page_dirty(page);
548
Hugh Dickins365e9c872005-10-29 18:16:18 -0700549 /* Update high watermark before we lower rss */
550 update_hiwater_rss(mm);
551
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 if (PageAnon(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700553 swp_entry_t entry = { .val = page_private(page) };
Linus Torvalds1da177e2005-04-16 15:20:36 -0700554 /*
555 * Store the swap location in the pte.
556 * See handle_pte_fault() ...
557 */
558 BUG_ON(!PageSwapCache(page));
559 swap_duplicate(entry);
560 if (list_empty(&mm->mmlist)) {
561 spin_lock(&mmlist_lock);
Hugh Dickinsf412ac02005-10-29 18:16:41 -0700562 if (list_empty(&mm->mmlist))
563 list_add(&mm->mmlist, &init_mm.mmlist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 spin_unlock(&mmlist_lock);
565 }
566 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
567 BUG_ON(pte_file(*pte));
568 dec_mm_counter(mm, anon_rss);
Hugh Dickins42946212005-10-29 18:16:05 -0700569 } else
570 dec_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571
Linus Torvalds1da177e2005-04-16 15:20:36 -0700572 page_remove_rmap(page);
573 page_cache_release(page);
574
575out_unmap:
Hugh Dickinsc0718802005-10-29 18:16:31 -0700576 pte_unmap_unlock(pte, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577out:
578 return ret;
579}
580
581/*
582 * objrmap doesn't work for nonlinear VMAs because the assumption that
583 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
584 * Consequently, given a particular page and its ->index, we cannot locate the
585 * ptes which are mapping that page without an exhaustive linear search.
586 *
587 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
588 * maps the file to which the target page belongs. The ->vm_private_data field
589 * holds the current cursor into that scan. Successive searches will circulate
590 * around the vma's virtual address space.
591 *
592 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
593 * more scanning pressure is placed against them as well. Eventually pages
594 * will become fully unmapped and are eligible for eviction.
595 *
596 * For very sparsely populated VMAs this is a little inefficient - chances are
597 * there there won't be many ptes located within the scan cluster. In this case
598 * maybe we could scan further - to the end of the pte page, perhaps.
599 */
600#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
601#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
602
603static void try_to_unmap_cluster(unsigned long cursor,
604 unsigned int *mapcount, struct vm_area_struct *vma)
605{
606 struct mm_struct *mm = vma->vm_mm;
607 pgd_t *pgd;
608 pud_t *pud;
609 pmd_t *pmd;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700610 pte_t *pte;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700612 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613 struct page *page;
614 unsigned long address;
615 unsigned long end;
616 unsigned long pfn;
617
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618 address = (vma->vm_start + cursor) & CLUSTER_MASK;
619 end = address + CLUSTER_SIZE;
620 if (address < vma->vm_start)
621 address = vma->vm_start;
622 if (end > vma->vm_end)
623 end = vma->vm_end;
624
625 pgd = pgd_offset(mm, address);
626 if (!pgd_present(*pgd))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700627 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628
629 pud = pud_offset(pgd, address);
630 if (!pud_present(*pud))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700631 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700632
633 pmd = pmd_offset(pud, address);
634 if (!pmd_present(*pmd))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700635 return;
636
637 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638
Hugh Dickins365e9c872005-10-29 18:16:18 -0700639 /* Update high watermark before we lower rss */
640 update_hiwater_rss(mm);
641
Hugh Dickinsc0718802005-10-29 18:16:31 -0700642 for (; address < end; pte++, address += PAGE_SIZE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643 if (!pte_present(*pte))
644 continue;
645
646 pfn = pte_pfn(*pte);
Nick Pigginb5810032005-10-29 18:16:12 -0700647 if (unlikely(!pfn_valid(pfn))) {
648 print_bad_pte(vma, *pte, address);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700649 continue;
Nick Pigginb5810032005-10-29 18:16:12 -0700650 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651
652 page = pfn_to_page(pfn);
653 BUG_ON(PageAnon(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700654
655 if (ptep_clear_flush_young(vma, address, pte))
656 continue;
657
658 /* Nuke the page table entry. */
659 flush_cache_page(vma, address, pfn);
660 pteval = ptep_clear_flush(vma, address, pte);
661
662 /* If nonlinear, store the file page offset in the pte. */
663 if (page->index != linear_page_index(vma, address))
664 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
665
666 /* Move the dirty bit to the physical page now the pte is gone. */
667 if (pte_dirty(pteval))
668 set_page_dirty(page);
669
670 page_remove_rmap(page);
671 page_cache_release(page);
Hugh Dickins42946212005-10-29 18:16:05 -0700672 dec_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673 (*mapcount)--;
674 }
Hugh Dickinsc0718802005-10-29 18:16:31 -0700675 pte_unmap_unlock(pte - 1, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676}
677
678static int try_to_unmap_anon(struct page *page)
679{
680 struct anon_vma *anon_vma;
681 struct vm_area_struct *vma;
682 int ret = SWAP_AGAIN;
683
684 anon_vma = page_lock_anon_vma(page);
685 if (!anon_vma)
686 return ret;
687
688 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
689 ret = try_to_unmap_one(page, vma);
690 if (ret == SWAP_FAIL || !page_mapped(page))
691 break;
692 }
693 spin_unlock(&anon_vma->lock);
694 return ret;
695}
696
697/**
698 * try_to_unmap_file - unmap file page using the object-based rmap method
699 * @page: the page to unmap
700 *
701 * Find all the mappings of a page using the mapping pointer and the vma chains
702 * contained in the address_space struct it points to.
703 *
704 * This function is only called from try_to_unmap for object-based pages.
705 */
706static int try_to_unmap_file(struct page *page)
707{
708 struct address_space *mapping = page->mapping;
709 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
710 struct vm_area_struct *vma;
711 struct prio_tree_iter iter;
712 int ret = SWAP_AGAIN;
713 unsigned long cursor;
714 unsigned long max_nl_cursor = 0;
715 unsigned long max_nl_size = 0;
716 unsigned int mapcount;
717
718 spin_lock(&mapping->i_mmap_lock);
719 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
720 ret = try_to_unmap_one(page, vma);
721 if (ret == SWAP_FAIL || !page_mapped(page))
722 goto out;
723 }
724
725 if (list_empty(&mapping->i_mmap_nonlinear))
726 goto out;
727
728 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
729 shared.vm_set.list) {
730 if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
731 continue;
732 cursor = (unsigned long) vma->vm_private_data;
733 if (cursor > max_nl_cursor)
734 max_nl_cursor = cursor;
735 cursor = vma->vm_end - vma->vm_start;
736 if (cursor > max_nl_size)
737 max_nl_size = cursor;
738 }
739
740 if (max_nl_size == 0) { /* any nonlinears locked or reserved */
741 ret = SWAP_FAIL;
742 goto out;
743 }
744
745 /*
746 * We don't try to search for this page in the nonlinear vmas,
747 * and page_referenced wouldn't have found it anyway. Instead
748 * just walk the nonlinear vmas trying to age and unmap some.
749 * The mapcount of the page we came in with is irrelevant,
750 * but even so use it as a guide to how hard we should try?
751 */
752 mapcount = page_mapcount(page);
753 if (!mapcount)
754 goto out;
755 cond_resched_lock(&mapping->i_mmap_lock);
756
757 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
758 if (max_nl_cursor == 0)
759 max_nl_cursor = CLUSTER_SIZE;
760
761 do {
762 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
763 shared.vm_set.list) {
764 if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
765 continue;
766 cursor = (unsigned long) vma->vm_private_data;
Hugh Dickins839b9682005-09-03 15:54:43 -0700767 while ( cursor < max_nl_cursor &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 cursor < vma->vm_end - vma->vm_start) {
769 try_to_unmap_cluster(cursor, &mapcount, vma);
770 cursor += CLUSTER_SIZE;
771 vma->vm_private_data = (void *) cursor;
772 if ((int)mapcount <= 0)
773 goto out;
774 }
775 vma->vm_private_data = (void *) max_nl_cursor;
776 }
777 cond_resched_lock(&mapping->i_mmap_lock);
778 max_nl_cursor += CLUSTER_SIZE;
779 } while (max_nl_cursor <= max_nl_size);
780
781 /*
782 * Don't loop forever (perhaps all the remaining pages are
783 * in locked vmas). Reset cursor on all unreserved nonlinear
784 * vmas, now forgetting on which ones it had fallen behind.
785 */
786 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
787 shared.vm_set.list) {
788 if (!(vma->vm_flags & VM_RESERVED))
789 vma->vm_private_data = NULL;
790 }
791out:
792 spin_unlock(&mapping->i_mmap_lock);
793 return ret;
794}
795
796/**
797 * try_to_unmap - try to remove all page table mappings to a page
798 * @page: the page to get unmapped
799 *
800 * Tries to remove all the page table entries which are mapping this
801 * page, used in the pageout path. Caller must hold the page lock.
802 * Return values are:
803 *
804 * SWAP_SUCCESS - we succeeded in removing all mappings
805 * SWAP_AGAIN - we missed a mapping, try again later
806 * SWAP_FAIL - the page is unswappable
807 */
808int try_to_unmap(struct page *page)
809{
810 int ret;
811
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 BUG_ON(!PageLocked(page));
813
814 if (PageAnon(page))
815 ret = try_to_unmap_anon(page);
816 else
817 ret = try_to_unmap_file(page);
818
819 if (!page_mapped(page))
820 ret = SWAP_SUCCESS;
821 return ret;
822}
Nikita Danilov81b40822005-05-01 08:58:36 -0700823