Commit | Line | Data |
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1da177e4 LT |
1 | /* |
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 | |
b8072f09 | 35 | * mm->page_table_lock or pte_lock |
1da177e4 | 36 | * zone->lru_lock (in mark_page_accessed) |
5d337b91 | 37 | * swap_lock (in swap_duplicate, swap_info_get) |
1da177e4 | 38 | * mmlist_lock (in mmput, drain_mmlist and others) |
1da177e4 LT |
39 | * 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 | ||
60 | kmem_cache_t *anon_vma_cachep; | |
61 | ||
62 | static 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. */ | |
81 | int 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 | ||
120 | void __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 | ||
126 | void __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 | ||
136 | void 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 | ||
148 | void 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 | ||
168 | static 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 | ||
179 | void __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 | */ | |
189 | static 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); | |
203 | out: | |
204 | rcu_read_unlock(); | |
205 | return anon_vma; | |
206 | } | |
207 | ||
208 | /* | |
209 | * At what user virtual address is page expected in vma? | |
210 | */ | |
211 | static inline unsigned long | |
212 | vma_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 | |
ee498ed7 | 228 | * page matches the vma: currently only used on anon pages, by unuse_vma; |
1da177e4 LT |
229 | */ |
230 | unsigned 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)) { | |
ee498ed7 HD |
237 | if (!vma->vm_file || |
238 | vma->vm_file->f_mapping != page->mapping) | |
1da177e4 LT |
239 | return -EFAULT; |
240 | } else | |
241 | return -EFAULT; | |
242 | return vma_address(page, vma); | |
243 | } | |
244 | ||
81b4082d ND |
245 | /* |
246 | * Check that @page is mapped at @address into @mm. | |
247 | * | |
b8072f09 | 248 | * On success returns with pte mapped and locked. |
81b4082d | 249 | */ |
ceffc078 | 250 | pte_t *page_check_address(struct page *page, struct mm_struct *mm, |
c0718806 | 251 | unsigned long address, spinlock_t **ptlp) |
81b4082d ND |
252 | { |
253 | pgd_t *pgd; | |
254 | pud_t *pud; | |
255 | pmd_t *pmd; | |
256 | pte_t *pte; | |
c0718806 | 257 | spinlock_t *ptl; |
81b4082d | 258 | |
81b4082d | 259 | pgd = pgd_offset(mm, address); |
c0718806 HD |
260 | 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; | |
276 | } | |
277 | ||
4c21e2f2 | 278 | ptl = pte_lockptr(mm, pmd); |
c0718806 HD |
279 | spin_lock(ptl); |
280 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { | |
281 | *ptlp = ptl; | |
282 | return pte; | |
81b4082d | 283 | } |
c0718806 HD |
284 | pte_unmap_unlock(pte, ptl); |
285 | return NULL; | |
81b4082d ND |
286 | } |
287 | ||
1da177e4 LT |
288 | /* |
289 | * Subfunctions of page_referenced: page_referenced_one called | |
290 | * repeatedly from either page_referenced_anon or page_referenced_file. | |
291 | */ | |
292 | static 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; | |
1da177e4 | 297 | pte_t *pte; |
c0718806 | 298 | spinlock_t *ptl; |
1da177e4 LT |
299 | int referenced = 0; |
300 | ||
1da177e4 LT |
301 | address = vma_address(page, vma); |
302 | if (address == -EFAULT) | |
303 | goto out; | |
304 | ||
c0718806 HD |
305 | pte = page_check_address(page, mm, address, &ptl); |
306 | if (!pte) | |
307 | goto out; | |
1da177e4 | 308 | |
c0718806 HD |
309 | if (ptep_clear_flush_young(vma, address, pte)) |
310 | referenced++; | |
1da177e4 | 311 | |
c0718806 HD |
312 | /* 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); | |
1da177e4 LT |
320 | out: |
321 | return referenced; | |
322 | } | |
323 | ||
324 | static 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 | */ | |
357 | static 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 | */ | |
413 | int 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 | * | |
b8072f09 | 449 | * The caller needs to hold the pte lock. |
1da177e4 LT |
450 | */ |
451 | void page_add_anon_rmap(struct page *page, | |
452 | struct vm_area_struct *vma, unsigned long address) | |
453 | { | |
1da177e4 | 454 | if (atomic_inc_and_test(&page->_mapcount)) { |
2822c1aa | 455 | struct anon_vma *anon_vma = vma->anon_vma; |
2822c1aa NP |
456 | |
457 | BUG_ON(!anon_vma); | |
458 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; | |
1da177e4 | 459 | page->mapping = (struct address_space *) anon_vma; |
2822c1aa | 460 | |
4d7670e0 | 461 | page->index = linear_page_index(vma, address); |
2822c1aa | 462 | |
1da177e4 LT |
463 | 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 | * | |
b8072f09 | 472 | * The caller needs to hold the pte lock. |
1da177e4 LT |
473 | */ |
474 | void page_add_file_rmap(struct page *page) | |
475 | { | |
476 | BUG_ON(PageAnon(page)); | |
b5810039 | 477 | BUG_ON(!pfn_valid(page_to_pfn(page))); |
1da177e4 LT |
478 | |
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 | * | |
b8072f09 | 487 | * The caller needs to hold the pte lock. |
1da177e4 LT |
488 | */ |
489 | void page_remove_rmap(struct page *page) | |
490 | { | |
1da177e4 LT |
491 | 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 | */ | |
512 | static 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; | |
1da177e4 LT |
516 | pte_t *pte; |
517 | pte_t pteval; | |
c0718806 | 518 | spinlock_t *ptl; |
1da177e4 LT |
519 | int ret = SWAP_AGAIN; |
520 | ||
1da177e4 LT |
521 | address = vma_address(page, vma); |
522 | if (address == -EFAULT) | |
523 | goto out; | |
524 | ||
c0718806 HD |
525 | pte = page_check_address(page, mm, address, &ptl); |
526 | if (!pte) | |
81b4082d | 527 | goto out; |
1da177e4 LT |
528 | |
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 | */ | |
101d2be7 | 534 | if ((vma->vm_flags & VM_LOCKED) || |
1da177e4 LT |
535 | ptep_clear_flush_young(vma, address, pte)) { |
536 | ret = SWAP_FAIL; | |
537 | goto out_unmap; | |
538 | } | |
539 | ||
1da177e4 LT |
540 | /* 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 | ||
365e9c87 HD |
548 | /* Update high watermark before we lower rss */ |
549 | update_hiwater_rss(mm); | |
550 | ||
1da177e4 | 551 | if (PageAnon(page)) { |
4c21e2f2 | 552 | swp_entry_t entry = { .val = page_private(page) }; |
1da177e4 LT |
553 | /* |
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); | |
f412ac08 HD |
561 | if (list_empty(&mm->mmlist)) |
562 | list_add(&mm->mmlist, &init_mm.mmlist); | |
1da177e4 LT |
563 | 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); | |
4294621f HD |
568 | } else |
569 | dec_mm_counter(mm, file_rss); | |
1da177e4 | 570 | |
1da177e4 LT |
571 | page_remove_rmap(page); |
572 | page_cache_release(page); | |
573 | ||
574 | out_unmap: | |
c0718806 | 575 | pte_unmap_unlock(pte, ptl); |
1da177e4 LT |
576 | out: |
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 | ||
602 | static 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; | |
c0718806 | 609 | pte_t *pte; |
1da177e4 | 610 | pte_t pteval; |
c0718806 | 611 | spinlock_t *ptl; |
1da177e4 LT |
612 | struct page *page; |
613 | unsigned long address; | |
614 | unsigned long end; | |
1da177e4 | 615 | |
1da177e4 LT |
616 | 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)) | |
c0718806 | 625 | return; |
1da177e4 LT |
626 | |
627 | pud = pud_offset(pgd, address); | |
628 | if (!pud_present(*pud)) | |
c0718806 | 629 | return; |
1da177e4 LT |
630 | |
631 | pmd = pmd_offset(pud, address); | |
632 | if (!pmd_present(*pmd)) | |
c0718806 HD |
633 | return; |
634 | ||
635 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); | |
1da177e4 | 636 | |
365e9c87 HD |
637 | /* Update high watermark before we lower rss */ |
638 | update_hiwater_rss(mm); | |
639 | ||
c0718806 | 640 | for (; address < end; pte++, address += PAGE_SIZE) { |
1da177e4 LT |
641 | if (!pte_present(*pte)) |
642 | continue; | |
6aab341e LT |
643 | page = vm_normal_page(vma, address, *pte); |
644 | BUG_ON(!page || PageAnon(page)); | |
1da177e4 LT |
645 | |
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); | |
4294621f | 663 | dec_mm_counter(mm, file_rss); |
1da177e4 LT |
664 | (*mapcount)--; |
665 | } | |
c0718806 | 666 | pte_unmap_unlock(pte - 1, ptl); |
1da177e4 LT |
667 | } |
668 | ||
669 | static 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 | */ | |
697 | static 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) { | |
101d2be7 | 721 | if (vma->vm_flags & VM_LOCKED) |
1da177e4 LT |
722 | 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) { | |
101d2be7 | 755 | if (vma->vm_flags & VM_LOCKED) |
1da177e4 LT |
756 | continue; |
757 | cursor = (unsigned long) vma->vm_private_data; | |
839b9685 | 758 | while ( cursor < max_nl_cursor && |
1da177e4 LT |
759 | 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 | */ | |
101d2be7 HD |
777 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
778 | vma->vm_private_data = NULL; | |
1da177e4 LT |
779 | out: |
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 | */ | |
796 | int try_to_unmap(struct page *page) | |
797 | { | |
798 | int ret; | |
799 | ||
1da177e4 LT |
800 | 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 | } | |
81b4082d | 811 |