blob: e76909e880ca8c2847b3b405f03ed56b453a4a44 [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 *
Jes Sorensen1b1dcc12006-01-09 15:59:24 -080023 * inode->i_mutex (while writing or truncating, not reading or faulting)
Linus Torvalds1da177e2005-04-16 15:20:36 -070024 * inode->i_alloc_sem
25 *
26 * When a page fault occurs in writing from user to file, down_read
Jes Sorensen1b1dcc12006-01-09 15:59:24 -080027 * of mmap_sem nests within i_mutex; in sys_msync, i_mutex nests within
28 * down_read of mmap_sem; i_mutex and down_write of mmap_sem are never
29 * taken together; in truncation, i_mutex is taken outermost.
Linus Torvalds1da177e2005-04-16 15:20:36 -070030 *
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
Nick Piggin053837f2006-01-18 17:42:27 -080036 * zone->lru_lock (in mark_page_accessed, isolate_lru_page)
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>
Christoph Lametera48d07a2006-02-01 03:05:38 -080055#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
57#include <asm/tlbflush.h>
58
Pekka Enbergfcc234f2006-03-22 00:08:13 -080059struct kmem_cache *anon_vma_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
61static inline void validate_anon_vma(struct vm_area_struct *find_vma)
62{
Nick Pigginb7ab7952006-03-22 00:08:42 -080063#ifdef CONFIG_DEBUG_VM
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 struct anon_vma *anon_vma = find_vma->anon_vma;
65 struct vm_area_struct *vma;
66 unsigned int mapcount = 0;
67 int found = 0;
68
69 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
70 mapcount++;
71 BUG_ON(mapcount > 100000);
72 if (vma == find_vma)
73 found = 1;
74 }
75 BUG_ON(!found);
76#endif
77}
78
79/* This must be called under the mmap_sem. */
80int anon_vma_prepare(struct vm_area_struct *vma)
81{
82 struct anon_vma *anon_vma = vma->anon_vma;
83
84 might_sleep();
85 if (unlikely(!anon_vma)) {
86 struct mm_struct *mm = vma->vm_mm;
87 struct anon_vma *allocated, *locked;
88
89 anon_vma = find_mergeable_anon_vma(vma);
90 if (anon_vma) {
91 allocated = NULL;
92 locked = anon_vma;
93 spin_lock(&locked->lock);
94 } else {
95 anon_vma = anon_vma_alloc();
96 if (unlikely(!anon_vma))
97 return -ENOMEM;
98 allocated = anon_vma;
99 locked = NULL;
100 }
101
102 /* page_table_lock to protect against threads */
103 spin_lock(&mm->page_table_lock);
104 if (likely(!vma->anon_vma)) {
105 vma->anon_vma = anon_vma;
Christoph Lameter06972122006-06-23 02:03:35 -0700106 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 allocated = NULL;
108 }
109 spin_unlock(&mm->page_table_lock);
110
111 if (locked)
112 spin_unlock(&locked->lock);
113 if (unlikely(allocated))
114 anon_vma_free(allocated);
115 }
116 return 0;
117}
118
119void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
120{
121 BUG_ON(vma->anon_vma != next->anon_vma);
122 list_del(&next->anon_vma_node);
123}
124
125void __anon_vma_link(struct vm_area_struct *vma)
126{
127 struct anon_vma *anon_vma = vma->anon_vma;
128
129 if (anon_vma) {
Christoph Lameter06972122006-06-23 02:03:35 -0700130 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131 validate_anon_vma(vma);
132 }
133}
134
135void anon_vma_link(struct vm_area_struct *vma)
136{
137 struct anon_vma *anon_vma = vma->anon_vma;
138
139 if (anon_vma) {
140 spin_lock(&anon_vma->lock);
Christoph Lameter06972122006-06-23 02:03:35 -0700141 list_add_tail(&vma->anon_vma_node, &anon_vma->head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 validate_anon_vma(vma);
143 spin_unlock(&anon_vma->lock);
144 }
145}
146
147void anon_vma_unlink(struct vm_area_struct *vma)
148{
149 struct anon_vma *anon_vma = vma->anon_vma;
150 int empty;
151
152 if (!anon_vma)
153 return;
154
155 spin_lock(&anon_vma->lock);
156 validate_anon_vma(vma);
157 list_del(&vma->anon_vma_node);
158
159 /* We must garbage collect the anon_vma if it's empty */
160 empty = list_empty(&anon_vma->head);
161 spin_unlock(&anon_vma->lock);
162
163 if (empty)
164 anon_vma_free(anon_vma);
165}
166
Pekka Enbergfcc234f2006-03-22 00:08:13 -0800167static void anon_vma_ctor(void *data, struct kmem_cache *cachep,
168 unsigned long flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169{
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,
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800293 struct vm_area_struct *vma, unsigned int *mapcount)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294{
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. */
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800314 if (mm != current->mm && has_swap_token(mm) &&
Hugh Dickinsc0718802005-10-29 18:16:31 -0700315 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
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800324static int page_referenced_anon(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325{
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) {
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800337 referenced += page_referenced_one(page, vma, &mapcount);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338 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 */
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800356static int page_referenced_file(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357{
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 }
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800394 referenced += page_referenced_one(page, vma, &mapcount);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 if (!mapcount)
396 break;
397 }
398
399 spin_unlock(&mapping->i_mmap_lock);
400 return referenced;
401}
402
403/**
404 * page_referenced - test if the page was referenced
405 * @page: the page to test
406 * @is_locked: caller holds lock on the page
407 *
408 * Quick test_and_clear_referenced for all mappings to a page,
409 * returns the number of ptes which referenced the page.
410 */
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800411int page_referenced(struct page *page, int is_locked)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700412{
413 int referenced = 0;
414
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415 if (page_test_and_clear_young(page))
416 referenced++;
417
418 if (TestClearPageReferenced(page))
419 referenced++;
420
421 if (page_mapped(page) && page->mapping) {
422 if (PageAnon(page))
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800423 referenced += page_referenced_anon(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424 else if (is_locked)
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800425 referenced += page_referenced_file(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 else if (TestSetPageLocked(page))
427 referenced++;
428 else {
429 if (page->mapping)
Rik van Rielf7b7fd82005-11-28 13:44:07 -0800430 referenced += page_referenced_file(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700431 unlock_page(page);
432 }
433 }
434 return referenced;
435}
436
437/**
Nick Piggin9617d952006-01-06 00:11:12 -0800438 * page_set_anon_rmap - setup new anonymous rmap
439 * @page: the page to add the mapping to
440 * @vma: the vm area in which the mapping is added
441 * @address: the user virtual address mapped
442 */
443static void __page_set_anon_rmap(struct page *page,
444 struct vm_area_struct *vma, unsigned long address)
445{
446 struct anon_vma *anon_vma = vma->anon_vma;
447
448 BUG_ON(!anon_vma);
449 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
450 page->mapping = (struct address_space *) anon_vma;
451
452 page->index = linear_page_index(vma, address);
453
Nick Piggina74609f2006-01-06 00:11:20 -0800454 /*
455 * nr_mapped state can be updated without turning off
456 * interrupts because it is not modified via interrupt.
457 */
458 __inc_page_state(nr_mapped);
Nick Piggin9617d952006-01-06 00:11:12 -0800459}
460
461/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462 * page_add_anon_rmap - add pte mapping to an anonymous page
463 * @page: the page to add the mapping to
464 * @vma: the vm area in which the mapping is added
465 * @address: the user virtual address mapped
466 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700467 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700468 */
469void page_add_anon_rmap(struct page *page,
470 struct vm_area_struct *vma, unsigned long address)
471{
Nick Piggin9617d952006-01-06 00:11:12 -0800472 if (atomic_inc_and_test(&page->_mapcount))
473 __page_set_anon_rmap(page, vma, address);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700474 /* else checking page index and mapping is racy */
475}
476
Nick Piggin9617d952006-01-06 00:11:12 -0800477/*
478 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
479 * @page: the page to add the mapping to
480 * @vma: the vm area in which the mapping is added
481 * @address: the user virtual address mapped
482 *
483 * Same as page_add_anon_rmap but must only be called on *new* pages.
484 * This means the inc-and-test can be bypassed.
485 */
486void page_add_new_anon_rmap(struct page *page,
487 struct vm_area_struct *vma, unsigned long address)
488{
489 atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
490 __page_set_anon_rmap(page, vma, address);
491}
492
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493/**
494 * page_add_file_rmap - add pte mapping to a file page
495 * @page: the page to add the mapping to
496 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700497 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 */
499void page_add_file_rmap(struct page *page)
500{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501 if (atomic_inc_and_test(&page->_mapcount))
Nick Piggina74609f2006-01-06 00:11:20 -0800502 __inc_page_state(nr_mapped);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503}
504
505/**
506 * page_remove_rmap - take down pte mapping from a page
507 * @page: page to remove mapping from
508 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700509 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 */
511void page_remove_rmap(struct page *page)
512{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 if (atomic_add_negative(-1, &page->_mapcount)) {
Nick Pigginb7ab7952006-03-22 00:08:42 -0800514#ifdef CONFIG_DEBUG_VM
515 if (unlikely(page_mapcount(page) < 0)) {
Dave Jonesef2bf0d2006-01-08 01:01:00 -0800516 printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
517 printk (KERN_EMERG " page->flags = %lx\n", page->flags);
518 printk (KERN_EMERG " page->count = %x\n", page_count(page));
519 printk (KERN_EMERG " page->mapping = %p\n", page->mapping);
520 }
Nick Pigginb7ab7952006-03-22 00:08:42 -0800521#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 BUG_ON(page_mapcount(page) < 0);
523 /*
524 * It would be tidy to reset the PageAnon mapping here,
525 * but that might overwrite a racing page_add_anon_rmap
526 * which increments mapcount after us but sets mapping
527 * before us: so leave the reset to free_hot_cold_page,
528 * and remember that it's only reliable while mapped.
529 * Leaving it set also helps swapoff to reinstate ptes
530 * faster for those pages still in swapcache.
531 */
532 if (page_test_and_clear_dirty(page))
533 set_page_dirty(page);
Nick Piggina74609f2006-01-06 00:11:20 -0800534 __dec_page_state(nr_mapped);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700535 }
536}
537
538/*
539 * Subfunctions of try_to_unmap: try_to_unmap_one called
540 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
541 */
Christoph Lametera48d07a2006-02-01 03:05:38 -0800542static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
Christoph Lameter73523492006-06-23 02:03:27 -0700543 int migration)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700544{
545 struct mm_struct *mm = vma->vm_mm;
546 unsigned long address;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700547 pte_t *pte;
548 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700549 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 int ret = SWAP_AGAIN;
551
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 address = vma_address(page, vma);
553 if (address == -EFAULT)
554 goto out;
555
Hugh Dickinsc0718802005-10-29 18:16:31 -0700556 pte = page_check_address(page, mm, address, &ptl);
557 if (!pte)
Nikita Danilov81b40822005-05-01 08:58:36 -0700558 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700559
560 /*
561 * If the page is mlock()d, we cannot swap it out.
562 * If it's recently referenced (perhaps page_referenced
563 * skipped over this mm) then we should reactivate it.
564 */
Christoph Lametere6a15302006-06-25 05:46:49 -0700565 if (!migration && ((vma->vm_flags & VM_LOCKED) ||
566 (ptep_clear_flush_young(vma, address, pte)))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700567 ret = SWAP_FAIL;
568 goto out_unmap;
569 }
570
Linus Torvalds1da177e2005-04-16 15:20:36 -0700571 /* Nuke the page table entry. */
572 flush_cache_page(vma, address, page_to_pfn(page));
573 pteval = ptep_clear_flush(vma, address, pte);
574
575 /* Move the dirty bit to the physical page now the pte is gone. */
576 if (pte_dirty(pteval))
577 set_page_dirty(page);
578
Hugh Dickins365e9c872005-10-29 18:16:18 -0700579 /* Update high watermark before we lower rss */
580 update_hiwater_rss(mm);
581
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 if (PageAnon(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700583 swp_entry_t entry = { .val = page_private(page) };
Christoph Lameter06972122006-06-23 02:03:35 -0700584
585 if (PageSwapCache(page)) {
586 /*
587 * Store the swap location in the pte.
588 * See handle_pte_fault() ...
589 */
590 swap_duplicate(entry);
591 if (list_empty(&mm->mmlist)) {
592 spin_lock(&mmlist_lock);
593 if (list_empty(&mm->mmlist))
594 list_add(&mm->mmlist, &init_mm.mmlist);
595 spin_unlock(&mmlist_lock);
596 }
Christoph Lameter442c9132006-06-23 02:03:38 -0700597 dec_mm_counter(mm, anon_rss);
Christoph Lameter04e62a22006-06-23 02:03:38 -0700598#ifdef CONFIG_MIGRATION
Christoph Lameter06972122006-06-23 02:03:35 -0700599 } else {
600 /*
601 * Store the pfn of the page in a special migration
602 * pte. do_swap_page() will wait until the migration
603 * pte is removed and then restart fault handling.
604 */
605 BUG_ON(!migration);
606 entry = make_migration_entry(page, pte_write(pteval));
Christoph Lameter04e62a22006-06-23 02:03:38 -0700607#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 }
609 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
610 BUG_ON(pte_file(*pte));
Hugh Dickins42946212005-10-29 18:16:05 -0700611 } else
Christoph Lameter04e62a22006-06-23 02:03:38 -0700612#ifdef CONFIG_MIGRATION
613 if (migration) {
614 /* Establish migration entry for a file page */
615 swp_entry_t entry;
616 entry = make_migration_entry(page, pte_write(pteval));
617 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
618 } else
619#endif
Hugh Dickins42946212005-10-29 18:16:05 -0700620 dec_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700621
Christoph Lameter04e62a22006-06-23 02:03:38 -0700622
Linus Torvalds1da177e2005-04-16 15:20:36 -0700623 page_remove_rmap(page);
624 page_cache_release(page);
625
626out_unmap:
Hugh Dickinsc0718802005-10-29 18:16:31 -0700627 pte_unmap_unlock(pte, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628out:
629 return ret;
630}
631
632/*
633 * objrmap doesn't work for nonlinear VMAs because the assumption that
634 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
635 * Consequently, given a particular page and its ->index, we cannot locate the
636 * ptes which are mapping that page without an exhaustive linear search.
637 *
638 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
639 * maps the file to which the target page belongs. The ->vm_private_data field
640 * holds the current cursor into that scan. Successive searches will circulate
641 * around the vma's virtual address space.
642 *
643 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
644 * more scanning pressure is placed against them as well. Eventually pages
645 * will become fully unmapped and are eligible for eviction.
646 *
647 * For very sparsely populated VMAs this is a little inefficient - chances are
648 * there there won't be many ptes located within the scan cluster. In this case
649 * maybe we could scan further - to the end of the pte page, perhaps.
650 */
651#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
652#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
653
654static void try_to_unmap_cluster(unsigned long cursor,
655 unsigned int *mapcount, struct vm_area_struct *vma)
656{
657 struct mm_struct *mm = vma->vm_mm;
658 pgd_t *pgd;
659 pud_t *pud;
660 pmd_t *pmd;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700661 pte_t *pte;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700662 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700663 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664 struct page *page;
665 unsigned long address;
666 unsigned long end;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667
Linus Torvalds1da177e2005-04-16 15:20:36 -0700668 address = (vma->vm_start + cursor) & CLUSTER_MASK;
669 end = address + CLUSTER_SIZE;
670 if (address < vma->vm_start)
671 address = vma->vm_start;
672 if (end > vma->vm_end)
673 end = vma->vm_end;
674
675 pgd = pgd_offset(mm, address);
676 if (!pgd_present(*pgd))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700677 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678
679 pud = pud_offset(pgd, address);
680 if (!pud_present(*pud))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700681 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700682
683 pmd = pmd_offset(pud, address);
684 if (!pmd_present(*pmd))
Hugh Dickinsc0718802005-10-29 18:16:31 -0700685 return;
686
687 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700688
Hugh Dickins365e9c872005-10-29 18:16:18 -0700689 /* Update high watermark before we lower rss */
690 update_hiwater_rss(mm);
691
Hugh Dickinsc0718802005-10-29 18:16:31 -0700692 for (; address < end; pte++, address += PAGE_SIZE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700693 if (!pte_present(*pte))
694 continue;
Linus Torvalds6aab3412005-11-28 14:34:23 -0800695 page = vm_normal_page(vma, address, *pte);
696 BUG_ON(!page || PageAnon(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700697
698 if (ptep_clear_flush_young(vma, address, pte))
699 continue;
700
701 /* Nuke the page table entry. */
Ben Collinseca35132005-11-29 11:45:26 -0800702 flush_cache_page(vma, address, pte_pfn(*pte));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 pteval = ptep_clear_flush(vma, address, pte);
704
705 /* If nonlinear, store the file page offset in the pte. */
706 if (page->index != linear_page_index(vma, address))
707 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
708
709 /* Move the dirty bit to the physical page now the pte is gone. */
710 if (pte_dirty(pteval))
711 set_page_dirty(page);
712
713 page_remove_rmap(page);
714 page_cache_release(page);
Hugh Dickins42946212005-10-29 18:16:05 -0700715 dec_mm_counter(mm, file_rss);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 (*mapcount)--;
717 }
Hugh Dickinsc0718802005-10-29 18:16:31 -0700718 pte_unmap_unlock(pte - 1, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719}
720
Christoph Lameter73523492006-06-23 02:03:27 -0700721static int try_to_unmap_anon(struct page *page, int migration)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700722{
723 struct anon_vma *anon_vma;
724 struct vm_area_struct *vma;
725 int ret = SWAP_AGAIN;
726
727 anon_vma = page_lock_anon_vma(page);
728 if (!anon_vma)
729 return ret;
730
731 list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
Christoph Lameter73523492006-06-23 02:03:27 -0700732 ret = try_to_unmap_one(page, vma, migration);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733 if (ret == SWAP_FAIL || !page_mapped(page))
734 break;
735 }
736 spin_unlock(&anon_vma->lock);
737 return ret;
738}
739
740/**
741 * try_to_unmap_file - unmap file page using the object-based rmap method
742 * @page: the page to unmap
743 *
744 * Find all the mappings of a page using the mapping pointer and the vma chains
745 * contained in the address_space struct it points to.
746 *
747 * This function is only called from try_to_unmap for object-based pages.
748 */
Christoph Lameter73523492006-06-23 02:03:27 -0700749static int try_to_unmap_file(struct page *page, int migration)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750{
751 struct address_space *mapping = page->mapping;
752 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
753 struct vm_area_struct *vma;
754 struct prio_tree_iter iter;
755 int ret = SWAP_AGAIN;
756 unsigned long cursor;
757 unsigned long max_nl_cursor = 0;
758 unsigned long max_nl_size = 0;
759 unsigned int mapcount;
760
761 spin_lock(&mapping->i_mmap_lock);
762 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
Christoph Lameter73523492006-06-23 02:03:27 -0700763 ret = try_to_unmap_one(page, vma, migration);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764 if (ret == SWAP_FAIL || !page_mapped(page))
765 goto out;
766 }
767
768 if (list_empty(&mapping->i_mmap_nonlinear))
769 goto out;
770
771 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
772 shared.vm_set.list) {
Christoph Lametere6a15302006-06-25 05:46:49 -0700773 if ((vma->vm_flags & VM_LOCKED) && !migration)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774 continue;
775 cursor = (unsigned long) vma->vm_private_data;
776 if (cursor > max_nl_cursor)
777 max_nl_cursor = cursor;
778 cursor = vma->vm_end - vma->vm_start;
779 if (cursor > max_nl_size)
780 max_nl_size = cursor;
781 }
782
783 if (max_nl_size == 0) { /* any nonlinears locked or reserved */
784 ret = SWAP_FAIL;
785 goto out;
786 }
787
788 /*
789 * We don't try to search for this page in the nonlinear vmas,
790 * and page_referenced wouldn't have found it anyway. Instead
791 * just walk the nonlinear vmas trying to age and unmap some.
792 * The mapcount of the page we came in with is irrelevant,
793 * but even so use it as a guide to how hard we should try?
794 */
795 mapcount = page_mapcount(page);
796 if (!mapcount)
797 goto out;
798 cond_resched_lock(&mapping->i_mmap_lock);
799
800 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
801 if (max_nl_cursor == 0)
802 max_nl_cursor = CLUSTER_SIZE;
803
804 do {
805 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
806 shared.vm_set.list) {
Christoph Lametere6a15302006-06-25 05:46:49 -0700807 if ((vma->vm_flags & VM_LOCKED) && !migration)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700808 continue;
809 cursor = (unsigned long) vma->vm_private_data;
Hugh Dickins839b9682005-09-03 15:54:43 -0700810 while ( cursor < max_nl_cursor &&
Linus Torvalds1da177e2005-04-16 15:20:36 -0700811 cursor < vma->vm_end - vma->vm_start) {
812 try_to_unmap_cluster(cursor, &mapcount, vma);
813 cursor += CLUSTER_SIZE;
814 vma->vm_private_data = (void *) cursor;
815 if ((int)mapcount <= 0)
816 goto out;
817 }
818 vma->vm_private_data = (void *) max_nl_cursor;
819 }
820 cond_resched_lock(&mapping->i_mmap_lock);
821 max_nl_cursor += CLUSTER_SIZE;
822 } while (max_nl_cursor <= max_nl_size);
823
824 /*
825 * Don't loop forever (perhaps all the remaining pages are
826 * in locked vmas). Reset cursor on all unreserved nonlinear
827 * vmas, now forgetting on which ones it had fallen behind.
828 */
Hugh Dickins101d2be2005-11-21 21:32:16 -0800829 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
830 vma->vm_private_data = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831out:
832 spin_unlock(&mapping->i_mmap_lock);
833 return ret;
834}
835
836/**
837 * try_to_unmap - try to remove all page table mappings to a page
838 * @page: the page to get unmapped
839 *
840 * Tries to remove all the page table entries which are mapping this
841 * page, used in the pageout path. Caller must hold the page lock.
842 * Return values are:
843 *
844 * SWAP_SUCCESS - we succeeded in removing all mappings
845 * SWAP_AGAIN - we missed a mapping, try again later
846 * SWAP_FAIL - the page is unswappable
847 */
Christoph Lameter73523492006-06-23 02:03:27 -0700848int try_to_unmap(struct page *page, int migration)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700849{
850 int ret;
851
Linus Torvalds1da177e2005-04-16 15:20:36 -0700852 BUG_ON(!PageLocked(page));
853
854 if (PageAnon(page))
Christoph Lameter73523492006-06-23 02:03:27 -0700855 ret = try_to_unmap_anon(page, migration);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856 else
Christoph Lameter73523492006-06-23 02:03:27 -0700857 ret = try_to_unmap_file(page, migration);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858
859 if (!page_mapped(page))
860 ret = SWAP_SUCCESS;
861 return ret;
862}
Nikita Danilov81b40822005-05-01 08:58:36 -0700863