blob: 6389cda02a20e50d3edfa836afa21895941b6e90 [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
Hugh Dickinsee498ed2005-11-21 21:32:18 -0800228 * page matches the vma: currently only used on anon pages, by unuse_vma;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 */
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)) {
Hugh Dickinsee498ed2005-11-21 21:32:18 -0800237 if (!vma->vm_file ||
238 vma->vm_file->f_mapping != page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239 return -EFAULT;
240 } else
241 return -EFAULT;
242 return vma_address(page, vma);
243}
244
245/*
Nikita Danilov81b40822005-05-01 08:58:36 -0700246 * Check that @page is mapped at @address into @mm.
247 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700248 * On success returns with pte mapped and locked.
Nikita Danilov81b40822005-05-01 08:58:36 -0700249 */
Carsten Otteceffc072005-06-23 22:05:25 -0700250pte_t *page_check_address(struct page *page, struct mm_struct *mm,
Hugh Dickinsc0718802005-10-29 18:16:31 -0700251 unsigned long address, spinlock_t **ptlp)
Nikita Danilov81b40822005-05-01 08:58:36 -0700252{
253 pgd_t *pgd;
254 pud_t *pud;
255 pmd_t *pmd;
256 pte_t *pte;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700257 spinlock_t *ptl;
Nikita Danilov81b40822005-05-01 08:58:36 -0700258
Nikita Danilov81b40822005-05-01 08:58:36 -0700259 pgd = pgd_offset(mm, address);
Hugh Dickinsc0718802005-10-29 18:16:31 -0700260 if (!pgd_present(*pgd))
261 return NULL;
262
263 pud = pud_offset(pgd, address);
264 if (!pud_present(*pud))
265 return NULL;
266
267 pmd = pmd_offset(pud, address);
268 if (!pmd_present(*pmd))
269 return NULL;
270
271 pte = pte_offset_map(pmd, address);
272 /* Make a quick check before getting the lock */
273 if (!pte_present(*pte)) {
274 pte_unmap(pte);
275 return NULL;
Nikita Danilov81b40822005-05-01 08:58:36 -0700276 }
Hugh Dickinsc0718802005-10-29 18:16:31 -0700277
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700278 ptl = pte_lockptr(mm, pmd);
Hugh Dickinsc0718802005-10-29 18:16:31 -0700279 spin_lock(ptl);
280 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
281 *ptlp = ptl;
282 return pte;
283 }
284 pte_unmap_unlock(pte, ptl);
285 return NULL;
Nikita Danilov81b40822005-05-01 08:58:36 -0700286}
287
288/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289 * Subfunctions of page_referenced: page_referenced_one called
290 * repeatedly from either page_referenced_anon or page_referenced_file.
291 */
292static int page_referenced_one(struct page *page,
293 struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token)
294{
295 struct mm_struct *mm = vma->vm_mm;
296 unsigned long address;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297 pte_t *pte;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700298 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299 int referenced = 0;
300
Linus Torvalds1da177e2005-04-16 15:20:36 -0700301 address = vma_address(page, vma);
302 if (address == -EFAULT)
303 goto out;
304
Hugh Dickinsc0718802005-10-29 18:16:31 -0700305 pte = page_check_address(page, mm, address, &ptl);
306 if (!pte)
307 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308
Hugh Dickinsc0718802005-10-29 18:16:31 -0700309 if (ptep_clear_flush_young(vma, address, pte))
310 referenced++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311
Hugh Dickinsc0718802005-10-29 18:16:31 -0700312 /* Pretend the page is referenced if the task has the
313 swap token and is in the middle of a page fault. */
314 if (mm != current->mm && !ignore_token && has_swap_token(mm) &&
315 rwsem_is_locked(&mm->mmap_sem))
316 referenced++;
317
318 (*mapcount)--;
319 pte_unmap_unlock(pte, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320out:
321 return referenced;
322}
323
324static int page_referenced_anon(struct page *page, int ignore_token)
325{
326 unsigned int mapcount;
327 struct anon_vma *anon_vma;
328 struct vm_area_struct *vma;
329 int referenced = 0;
330
331 anon_vma = page_lock_anon_vma(page);
332 if (!anon_vma)
333 return referenced;
334
335 mapcount = page_mapcount(page);
336 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
337 referenced += page_referenced_one(page, vma, &mapcount,
338 ignore_token);
339 if (!mapcount)
340 break;
341 }
342 spin_unlock(&anon_vma->lock);
343 return referenced;
344}
345
346/**
347 * page_referenced_file - referenced check for object-based rmap
348 * @page: the page we're checking references on.
349 *
350 * For an object-based mapped page, find all the places it is mapped and
351 * check/clear the referenced flag. This is done by following the page->mapping
352 * pointer, then walking the chain of vmas it holds. It returns the number
353 * of references it found.
354 *
355 * This function is only called from page_referenced for object-based pages.
356 */
357static int page_referenced_file(struct page *page, int ignore_token)
358{
359 unsigned int mapcount;
360 struct address_space *mapping = page->mapping;
361 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
362 struct vm_area_struct *vma;
363 struct prio_tree_iter iter;
364 int referenced = 0;
365
366 /*
367 * The caller's checks on page->mapping and !PageAnon have made
368 * sure that this is a file page: the check for page->mapping
369 * excludes the case just before it gets set on an anon page.
370 */
371 BUG_ON(PageAnon(page));
372
373 /*
374 * The page lock not only makes sure that page->mapping cannot
375 * suddenly be NULLified by truncation, it makes sure that the
376 * structure at mapping cannot be freed and reused yet,
377 * so we can safely take mapping->i_mmap_lock.
378 */
379 BUG_ON(!PageLocked(page));
380
381 spin_lock(&mapping->i_mmap_lock);
382
383 /*
384 * i_mmap_lock does not stabilize mapcount at all, but mapcount
385 * is more likely to be accurate if we note it after spinning.
386 */
387 mapcount = page_mapcount(page);
388
389 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
390 if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
391 == (VM_LOCKED|VM_MAYSHARE)) {
392 referenced++;
393 break;
394 }
395 referenced += page_referenced_one(page, vma, &mapcount,
396 ignore_token);
397 if (!mapcount)
398 break;
399 }
400
401 spin_unlock(&mapping->i_mmap_lock);
402 return referenced;
403}
404
405/**
406 * page_referenced - test if the page was referenced
407 * @page: the page to test
408 * @is_locked: caller holds lock on the page
409 *
410 * Quick test_and_clear_referenced for all mappings to a page,
411 * returns the number of ptes which referenced the page.
412 */
413int page_referenced(struct page *page, int is_locked, int ignore_token)
414{
415 int referenced = 0;
416
417 if (!swap_token_default_timeout)
418 ignore_token = 1;
419
420 if (page_test_and_clear_young(page))
421 referenced++;
422
423 if (TestClearPageReferenced(page))
424 referenced++;
425
426 if (page_mapped(page) && page->mapping) {
427 if (PageAnon(page))
428 referenced += page_referenced_anon(page, ignore_token);
429 else if (is_locked)
430 referenced += page_referenced_file(page, ignore_token);
431 else if (TestSetPageLocked(page))
432 referenced++;
433 else {
434 if (page->mapping)
435 referenced += page_referenced_file(page,
436 ignore_token);
437 unlock_page(page);
438 }
439 }
440 return referenced;
441}
442
443/**
444 * page_add_anon_rmap - add pte mapping to an anonymous page
445 * @page: the page to add the mapping to
446 * @vma: the vm area in which the mapping is added
447 * @address: the user virtual address mapped
448 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700449 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450 */
451void page_add_anon_rmap(struct page *page,
452 struct vm_area_struct *vma, unsigned long address)
453{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454 if (atomic_inc_and_test(&page->_mapcount)) {
Nick Piggin2822c1a2005-09-03 15:54:47 -0700455 struct anon_vma *anon_vma = vma->anon_vma;
Nick Piggin2822c1a2005-09-03 15:54:47 -0700456
457 BUG_ON(!anon_vma);
458 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459 page->mapping = (struct address_space *) anon_vma;
Nick Piggin2822c1a2005-09-03 15:54:47 -0700460
Nick Piggin4d7670e2005-09-03 15:54:48 -0700461 page->index = linear_page_index(vma, address);
Nick Piggin2822c1a2005-09-03 15:54:47 -0700462
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 inc_page_state(nr_mapped);
464 }
465 /* else checking page index and mapping is racy */
466}
467
468/**
469 * page_add_file_rmap - add pte mapping to a file page
470 * @page: the page to add the mapping to
471 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700472 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473 */
474void page_add_file_rmap(struct page *page)
475{
476 BUG_ON(PageAnon(page));
Nick Pigginb5810032005-10-29 18:16:12 -0700477 BUG_ON(!pfn_valid(page_to_pfn(page)));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478
479 if (atomic_inc_and_test(&page->_mapcount))
480 inc_page_state(nr_mapped);
481}
482
483/**
484 * page_remove_rmap - take down pte mapping from a page
485 * @page: page to remove mapping from
486 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700487 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488 */
489void page_remove_rmap(struct page *page)
490{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700491 if (atomic_add_negative(-1, &page->_mapcount)) {
492 BUG_ON(page_mapcount(page) < 0);
493 /*
494 * It would be tidy to reset the PageAnon mapping here,
495 * but that might overwrite a racing page_add_anon_rmap
496 * which increments mapcount after us but sets mapping
497 * before us: so leave the reset to free_hot_cold_page,
498 * and remember that it's only reliable while mapped.
499 * Leaving it set also helps swapoff to reinstate ptes
500 * faster for those pages still in swapcache.
501 */
502 if (page_test_and_clear_dirty(page))
503 set_page_dirty(page);
504 dec_page_state(nr_mapped);
505 }
506}
507
508/*
509 * Subfunctions of try_to_unmap: try_to_unmap_one called
510 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
511 */
512static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
513{
514 struct mm_struct *mm = vma->vm_mm;
515 unsigned long address;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 pte_t *pte;
517 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700518 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700519 int ret = SWAP_AGAIN;
520
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 address = vma_address(page, vma);
522 if (address == -EFAULT)
523 goto out;
524
Hugh Dickinsc0718802005-10-29 18:16:31 -0700525 pte = page_check_address(page, mm, address, &ptl);
526 if (!pte)
Nikita Danilov81b40822005-05-01 08:58:36 -0700527 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528
529 /*
530 * If the page is mlock()d, we cannot swap it out.
531 * If it's recently referenced (perhaps page_referenced
532 * skipped over this mm) then we should reactivate it.
533 */
Hugh Dickins101d2be2005-11-21 21:32:16 -0800534 if ((vma->vm_flags & VM_LOCKED) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535 ptep_clear_flush_young(vma, address, pte)) {
536 ret = SWAP_FAIL;
537 goto out_unmap;
538 }
539
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 /* Nuke the page table entry. */
541 flush_cache_page(vma, address, page_to_pfn(page));
542 pteval = ptep_clear_flush(vma, address, pte);
543
544 /* Move the dirty bit to the physical page now the pte is gone. */
545 if (pte_dirty(pteval))
546 set_page_dirty(page);
547
Hugh Dickins365e9c872005-10-29 18:16:18 -0700548 /* Update high watermark before we lower rss */
549 update_hiwater_rss(mm);
550
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551 if (PageAnon(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700552 swp_entry_t entry = { .val = page_private(page) };
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 /*
554 * Store the swap location in the pte.
555 * See handle_pte_fault() ...
556 */
557 BUG_ON(!PageSwapCache(page));
558 swap_duplicate(entry);
559 if (list_empty(&mm->mmlist)) {
560 spin_lock(&mmlist_lock);
Hugh Dickinsf412ac02005-10-29 18:16:41 -0700561 if (list_empty(&mm->mmlist))
562 list_add(&mm->mmlist, &init_mm.mmlist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700563 spin_unlock(&mmlist_lock);
564 }
565 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
566 BUG_ON(pte_file(*pte));
567 dec_mm_counter(mm, anon_rss);
Hugh Dickins42946212005-10-29 18:16:05 -0700568 } else
569 dec_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 page_remove_rmap(page);
572 page_cache_release(page);
573
574out_unmap:
Hugh Dickinsc0718802005-10-29 18:16:31 -0700575 pte_unmap_unlock(pte, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576out:
577 return ret;
578}
579
580/*
581 * objrmap doesn't work for nonlinear VMAs because the assumption that
582 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
583 * Consequently, given a particular page and its ->index, we cannot locate the
584 * ptes which are mapping that page without an exhaustive linear search.
585 *
586 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
587 * maps the file to which the target page belongs. The ->vm_private_data field
588 * holds the current cursor into that scan. Successive searches will circulate
589 * around the vma's virtual address space.
590 *
591 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
592 * more scanning pressure is placed against them as well. Eventually pages
593 * will become fully unmapped and are eligible for eviction.
594 *
595 * For very sparsely populated VMAs this is a little inefficient - chances are
596 * there there won't be many ptes located within the scan cluster. In this case
597 * maybe we could scan further - to the end of the pte page, perhaps.
598 */
599#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
600#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
601
602static void try_to_unmap_cluster(unsigned long cursor,
603 unsigned int *mapcount, struct vm_area_struct *vma)
604{
605 struct mm_struct *mm = vma->vm_mm;
606 pgd_t *pgd;
607 pud_t *pud;
608 pmd_t *pmd;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700609 pte_t *pte;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700611 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612 struct page *page;
613 unsigned long address;
614 unsigned long end;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 address = (vma->vm_start + cursor) & CLUSTER_MASK;
617 end = address + CLUSTER_SIZE;
618 if (address < vma->vm_start)
619 address = vma->vm_start;
620 if (end > vma->vm_end)
621 end = vma->vm_end;
622
623 pgd = pgd_offset(mm, address);
624 if (!pgd_present(*pgd))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700625 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626
627 pud = pud_offset(pgd, address);
628 if (!pud_present(*pud))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700629 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630
631 pmd = pmd_offset(pud, address);
632 if (!pmd_present(*pmd))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700633 return;
634
635 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636
Hugh Dickins365e9c872005-10-29 18:16:18 -0700637 /* Update high watermark before we lower rss */
638 update_hiwater_rss(mm);
639
Hugh Dickinsc0718802005-10-29 18:16:31 -0700640 for (; address < end; pte++, address += PAGE_SIZE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 if (!pte_present(*pte))
642 continue;
Linus Torvalds6aab3412005-11-28 14:34:23 -0800643 page = vm_normal_page(vma, address, *pte);
644 BUG_ON(!page || PageAnon(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700645
646 if (ptep_clear_flush_young(vma, address, pte))
647 continue;
648
649 /* Nuke the page table entry. */
650 flush_cache_page(vma, address, pfn);
651 pteval = ptep_clear_flush(vma, address, pte);
652
653 /* If nonlinear, store the file page offset in the pte. */
654 if (page->index != linear_page_index(vma, address))
655 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
656
657 /* Move the dirty bit to the physical page now the pte is gone. */
658 if (pte_dirty(pteval))
659 set_page_dirty(page);
660
661 page_remove_rmap(page);
662 page_cache_release(page);
Hugh Dickins42946212005-10-29 18:16:05 -0700663 dec_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664 (*mapcount)--;
665 }
Hugh Dickinsc0718802005-10-29 18:16:31 -0700666 pte_unmap_unlock(pte - 1, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667}
668
669static int try_to_unmap_anon(struct page *page)
670{
671 struct anon_vma *anon_vma;
672 struct vm_area_struct *vma;
673 int ret = SWAP_AGAIN;
674
675 anon_vma = page_lock_anon_vma(page);
676 if (!anon_vma)
677 return ret;
678
679 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
680 ret = try_to_unmap_one(page, vma);
681 if (ret == SWAP_FAIL || !page_mapped(page))
682 break;
683 }
684 spin_unlock(&anon_vma->lock);
685 return ret;
686}
687
688/**
689 * try_to_unmap_file - unmap file page using the object-based rmap method
690 * @page: the page to unmap
691 *
692 * Find all the mappings of a page using the mapping pointer and the vma chains
693 * contained in the address_space struct it points to.
694 *
695 * This function is only called from try_to_unmap for object-based pages.
696 */
697static int try_to_unmap_file(struct page *page)
698{
699 struct address_space *mapping = page->mapping;
700 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
701 struct vm_area_struct *vma;
702 struct prio_tree_iter iter;
703 int ret = SWAP_AGAIN;
704 unsigned long cursor;
705 unsigned long max_nl_cursor = 0;
706 unsigned long max_nl_size = 0;
707 unsigned int mapcount;
708
709 spin_lock(&mapping->i_mmap_lock);
710 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
711 ret = try_to_unmap_one(page, vma);
712 if (ret == SWAP_FAIL || !page_mapped(page))
713 goto out;
714 }
715
716 if (list_empty(&mapping->i_mmap_nonlinear))
717 goto out;
718
719 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
720 shared.vm_set.list) {
Hugh Dickins101d2be2005-11-21 21:32:16 -0800721 if (vma->vm_flags & VM_LOCKED)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722 continue;
723 cursor = (unsigned long) vma->vm_private_data;
724 if (cursor > max_nl_cursor)
725 max_nl_cursor = cursor;
726 cursor = vma->vm_end - vma->vm_start;
727 if (cursor > max_nl_size)
728 max_nl_size = cursor;
729 }
730
731 if (max_nl_size == 0) { /* any nonlinears locked or reserved */
732 ret = SWAP_FAIL;
733 goto out;
734 }
735
736 /*
737 * We don't try to search for this page in the nonlinear vmas,
738 * and page_referenced wouldn't have found it anyway. Instead
739 * just walk the nonlinear vmas trying to age and unmap some.
740 * The mapcount of the page we came in with is irrelevant,
741 * but even so use it as a guide to how hard we should try?
742 */
743 mapcount = page_mapcount(page);
744 if (!mapcount)
745 goto out;
746 cond_resched_lock(&mapping->i_mmap_lock);
747
748 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
749 if (max_nl_cursor == 0)
750 max_nl_cursor = CLUSTER_SIZE;
751
752 do {
753 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
754 shared.vm_set.list) {
Hugh Dickins101d2be2005-11-21 21:32:16 -0800755 if (vma->vm_flags & VM_LOCKED)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700756 continue;
757 cursor = (unsigned long) vma->vm_private_data;
Hugh Dickins839b9682005-09-03 15:54:43 -0700758 while ( cursor < max_nl_cursor &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700759 cursor < vma->vm_end - vma->vm_start) {
760 try_to_unmap_cluster(cursor, &mapcount, vma);
761 cursor += CLUSTER_SIZE;
762 vma->vm_private_data = (void *) cursor;
763 if ((int)mapcount <= 0)
764 goto out;
765 }
766 vma->vm_private_data = (void *) max_nl_cursor;
767 }
768 cond_resched_lock(&mapping->i_mmap_lock);
769 max_nl_cursor += CLUSTER_SIZE;
770 } while (max_nl_cursor <= max_nl_size);
771
772 /*
773 * Don't loop forever (perhaps all the remaining pages are
774 * in locked vmas). Reset cursor on all unreserved nonlinear
775 * vmas, now forgetting on which ones it had fallen behind.
776 */
Hugh Dickins101d2be2005-11-21 21:32:16 -0800777 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
778 vma->vm_private_data = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779out:
780 spin_unlock(&mapping->i_mmap_lock);
781 return ret;
782}
783
784/**
785 * try_to_unmap - try to remove all page table mappings to a page
786 * @page: the page to get unmapped
787 *
788 * Tries to remove all the page table entries which are mapping this
789 * page, used in the pageout path. Caller must hold the page lock.
790 * Return values are:
791 *
792 * SWAP_SUCCESS - we succeeded in removing all mappings
793 * SWAP_AGAIN - we missed a mapping, try again later
794 * SWAP_FAIL - the page is unswappable
795 */
796int try_to_unmap(struct page *page)
797{
798 int ret;
799
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800 BUG_ON(!PageLocked(page));
801
802 if (PageAnon(page))
803 ret = try_to_unmap_anon(page);
804 else
805 ret = try_to_unmap_file(page);
806
807 if (!page_mapped(page))
808 ret = SWAP_SUCCESS;
809 return ret;
810}
Nikita Danilov81b40822005-05-01 08:58:36 -0700811