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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 2003, 2004 |
18 | */ |
19 | |
20 | /* |
21 | * Lock ordering in mm: |
22 | * |
23 | * inode->i_mutex (while writing or truncating, not reading or faulting) |
24 | * inode->i_alloc_sem (vmtruncate_range) |
25 | * mm->mmap_sem |
26 | * page->flags PG_locked (lock_page) |
27 | * mapping->i_mmap_lock |
28 | * anon_vma->lock |
29 | * mm->page_table_lock or pte_lock |
30 | * zone->lru_lock (in mark_page_accessed, isolate_lru_page) |
31 | * swap_lock (in swap_duplicate, swap_info_get) |
32 | * mmlist_lock (in mmput, drain_mmlist and others) |
33 | * mapping->private_lock (in __set_page_dirty_buffers) |
34 | * inode_lock (in set_page_dirty's __mark_inode_dirty) |
35 | * sb_lock (within inode_lock in fs/fs-writeback.c) |
36 | * mapping->tree_lock (widely used, in set_page_dirty, |
37 | * in arch-dependent flush_dcache_mmap_lock, |
38 | * within inode_lock in __sync_single_inode) |
39 | * |
40 | * (code doesn't rely on that order so it could be switched around) |
41 | * ->tasklist_lock |
42 | * anon_vma->lock (memory_failure, collect_procs_anon) |
43 | * pte map lock |
44 | */ |
45 | |
46 | #include <linux/mm.h> |
47 | #include <linux/pagemap.h> |
48 | #include <linux/swap.h> |
49 | #include <linux/swapops.h> |
50 | #include <linux/slab.h> |
51 | #include <linux/init.h> |
52 | #include <linux/rmap.h> |
53 | #include <linux/rcupdate.h> |
54 | #include <linux/module.h> |
55 | #include <linux/memcontrol.h> |
56 | #include <linux/mmu_notifier.h> |
57 | #include <linux/migrate.h> |
58 | |
59 | #include <asm/tlbflush.h> |
60 | |
61 | #include "internal.h" |
62 | |
63 | static struct kmem_cache *anon_vma_cachep; |
64 | |
65 | static inline struct anon_vma *anon_vma_alloc(void) |
66 | { |
67 | return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
68 | } |
69 | |
70 | static inline void anon_vma_free(struct anon_vma *anon_vma) |
71 | { |
72 | kmem_cache_free(anon_vma_cachep, anon_vma); |
73 | } |
74 | |
75 | /** |
76 | * anon_vma_prepare - attach an anon_vma to a memory region |
77 | * @vma: the memory region in question |
78 | * |
79 | * This makes sure the memory mapping described by 'vma' has |
80 | * an 'anon_vma' attached to it, so that we can associate the |
81 | * anonymous pages mapped into it with that anon_vma. |
82 | * |
83 | * The common case will be that we already have one, but if |
84 | * if not we either need to find an adjacent mapping that we |
85 | * can re-use the anon_vma from (very common when the only |
86 | * reason for splitting a vma has been mprotect()), or we |
87 | * allocate a new one. |
88 | * |
89 | * Anon-vma allocations are very subtle, because we may have |
90 | * optimistically looked up an anon_vma in page_lock_anon_vma() |
91 | * and that may actually touch the spinlock even in the newly |
92 | * allocated vma (it depends on RCU to make sure that the |
93 | * anon_vma isn't actually destroyed). |
94 | * |
95 | * As a result, we need to do proper anon_vma locking even |
96 | * for the new allocation. At the same time, we do not want |
97 | * to do any locking for the common case of already having |
98 | * an anon_vma. |
99 | * |
100 | * This must be called with the mmap_sem held for reading. |
101 | */ |
102 | int anon_vma_prepare(struct vm_area_struct *vma) |
103 | { |
104 | struct anon_vma *anon_vma = vma->anon_vma; |
105 | |
106 | might_sleep(); |
107 | if (unlikely(!anon_vma)) { |
108 | struct mm_struct *mm = vma->vm_mm; |
109 | struct anon_vma *allocated; |
110 | |
111 | anon_vma = find_mergeable_anon_vma(vma); |
112 | allocated = NULL; |
113 | if (!anon_vma) { |
114 | anon_vma = anon_vma_alloc(); |
115 | if (unlikely(!anon_vma)) |
116 | return -ENOMEM; |
117 | allocated = anon_vma; |
118 | } |
119 | spin_lock(&anon_vma->lock); |
120 | |
121 | /* page_table_lock to protect against threads */ |
122 | spin_lock(&mm->page_table_lock); |
123 | if (likely(!vma->anon_vma)) { |
124 | vma->anon_vma = anon_vma; |
125 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
126 | allocated = NULL; |
127 | } |
128 | spin_unlock(&mm->page_table_lock); |
129 | |
130 | spin_unlock(&anon_vma->lock); |
131 | if (unlikely(allocated)) |
132 | anon_vma_free(allocated); |
133 | } |
134 | return 0; |
135 | } |
136 | |
137 | void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next) |
138 | { |
139 | BUG_ON(vma->anon_vma != next->anon_vma); |
140 | list_del(&next->anon_vma_node); |
141 | } |
142 | |
143 | void __anon_vma_link(struct vm_area_struct *vma) |
144 | { |
145 | struct anon_vma *anon_vma = vma->anon_vma; |
146 | |
147 | if (anon_vma) |
148 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
149 | } |
150 | |
151 | void anon_vma_link(struct vm_area_struct *vma) |
152 | { |
153 | struct anon_vma *anon_vma = vma->anon_vma; |
154 | |
155 | if (anon_vma) { |
156 | spin_lock(&anon_vma->lock); |
157 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
158 | spin_unlock(&anon_vma->lock); |
159 | } |
160 | } |
161 | |
162 | void anon_vma_unlink(struct vm_area_struct *vma) |
163 | { |
164 | struct anon_vma *anon_vma = vma->anon_vma; |
165 | int empty; |
166 | |
167 | if (!anon_vma) |
168 | return; |
169 | |
170 | spin_lock(&anon_vma->lock); |
171 | list_del(&vma->anon_vma_node); |
172 | |
173 | /* We must garbage collect the anon_vma if it's empty */ |
174 | empty = list_empty(&anon_vma->head); |
175 | spin_unlock(&anon_vma->lock); |
176 | |
177 | if (empty) |
178 | anon_vma_free(anon_vma); |
179 | } |
180 | |
181 | static void anon_vma_ctor(void *data) |
182 | { |
183 | struct anon_vma *anon_vma = data; |
184 | |
185 | spin_lock_init(&anon_vma->lock); |
186 | INIT_LIST_HEAD(&anon_vma->head); |
187 | } |
188 | |
189 | void __init anon_vma_init(void) |
190 | { |
191 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), |
192 | 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor); |
193 | } |
194 | |
195 | /* |
196 | * Getting a lock on a stable anon_vma from a page off the LRU is |
197 | * tricky: page_lock_anon_vma rely on RCU to guard against the races. |
198 | */ |
199 | struct anon_vma *page_lock_anon_vma(struct page *page) |
200 | { |
201 | struct anon_vma *anon_vma; |
202 | unsigned long anon_mapping; |
203 | |
204 | rcu_read_lock(); |
205 | anon_mapping = (unsigned long) page->mapping; |
206 | if (!(anon_mapping & PAGE_MAPPING_ANON)) |
207 | goto out; |
208 | if (!page_mapped(page)) |
209 | goto out; |
210 | |
211 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
212 | spin_lock(&anon_vma->lock); |
213 | return anon_vma; |
214 | out: |
215 | rcu_read_unlock(); |
216 | return NULL; |
217 | } |
218 | |
219 | void page_unlock_anon_vma(struct anon_vma *anon_vma) |
220 | { |
221 | spin_unlock(&anon_vma->lock); |
222 | rcu_read_unlock(); |
223 | } |
224 | |
225 | /* |
226 | * At what user virtual address is page expected in @vma? |
227 | * Returns virtual address or -EFAULT if page's index/offset is not |
228 | * within the range mapped the @vma. |
229 | */ |
230 | static inline unsigned long |
231 | vma_address(struct page *page, struct vm_area_struct *vma) |
232 | { |
233 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
234 | unsigned long address; |
235 | |
236 | address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
237 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { |
238 | /* page should be within @vma mapping range */ |
239 | return -EFAULT; |
240 | } |
241 | return address; |
242 | } |
243 | |
244 | /* |
245 | * At what user virtual address is page expected in vma? |
246 | * checking that the page matches the vma. |
247 | */ |
248 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
249 | { |
250 | if (PageAnon(page)) { |
251 | if ((void *)vma->anon_vma != |
252 | (void *)page->mapping - PAGE_MAPPING_ANON) |
253 | return -EFAULT; |
254 | } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { |
255 | if (!vma->vm_file || |
256 | vma->vm_file->f_mapping != page->mapping) |
257 | return -EFAULT; |
258 | } else |
259 | return -EFAULT; |
260 | return vma_address(page, vma); |
261 | } |
262 | |
263 | /* |
264 | * Check that @page is mapped at @address into @mm. |
265 | * |
266 | * If @sync is false, page_check_address may perform a racy check to avoid |
267 | * the page table lock when the pte is not present (helpful when reclaiming |
268 | * highly shared pages). |
269 | * |
270 | * On success returns with pte mapped and locked. |
271 | */ |
272 | pte_t *page_check_address(struct page *page, struct mm_struct *mm, |
273 | unsigned long address, spinlock_t **ptlp, int sync) |
274 | { |
275 | pgd_t *pgd; |
276 | pud_t *pud; |
277 | pmd_t *pmd; |
278 | pte_t *pte; |
279 | spinlock_t *ptl; |
280 | |
281 | pgd = pgd_offset(mm, address); |
282 | if (!pgd_present(*pgd)) |
283 | return NULL; |
284 | |
285 | pud = pud_offset(pgd, address); |
286 | if (!pud_present(*pud)) |
287 | return NULL; |
288 | |
289 | pmd = pmd_offset(pud, address); |
290 | if (!pmd_present(*pmd)) |
291 | return NULL; |
292 | |
293 | pte = pte_offset_map(pmd, address); |
294 | /* Make a quick check before getting the lock */ |
295 | if (!sync && !pte_present(*pte)) { |
296 | pte_unmap(pte); |
297 | return NULL; |
298 | } |
299 | |
300 | ptl = pte_lockptr(mm, pmd); |
301 | spin_lock(ptl); |
302 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { |
303 | *ptlp = ptl; |
304 | return pte; |
305 | } |
306 | pte_unmap_unlock(pte, ptl); |
307 | return NULL; |
308 | } |
309 | |
310 | /** |
311 | * page_mapped_in_vma - check whether a page is really mapped in a VMA |
312 | * @page: the page to test |
313 | * @vma: the VMA to test |
314 | * |
315 | * Returns 1 if the page is mapped into the page tables of the VMA, 0 |
316 | * if the page is not mapped into the page tables of this VMA. Only |
317 | * valid for normal file or anonymous VMAs. |
318 | */ |
319 | int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) |
320 | { |
321 | unsigned long address; |
322 | pte_t *pte; |
323 | spinlock_t *ptl; |
324 | |
325 | address = vma_address(page, vma); |
326 | if (address == -EFAULT) /* out of vma range */ |
327 | return 0; |
328 | pte = page_check_address(page, vma->vm_mm, address, &ptl, 1); |
329 | if (!pte) /* the page is not in this mm */ |
330 | return 0; |
331 | pte_unmap_unlock(pte, ptl); |
332 | |
333 | return 1; |
334 | } |
335 | |
336 | /* |
337 | * Subfunctions of page_referenced: page_referenced_one called |
338 | * repeatedly from either page_referenced_anon or page_referenced_file. |
339 | */ |
340 | static int page_referenced_one(struct page *page, |
341 | struct vm_area_struct *vma, |
342 | unsigned int *mapcount, |
343 | unsigned long *vm_flags) |
344 | { |
345 | struct mm_struct *mm = vma->vm_mm; |
346 | unsigned long address; |
347 | pte_t *pte; |
348 | spinlock_t *ptl; |
349 | int referenced = 0; |
350 | |
351 | address = vma_address(page, vma); |
352 | if (address == -EFAULT) |
353 | goto out; |
354 | |
355 | pte = page_check_address(page, mm, address, &ptl, 0); |
356 | if (!pte) |
357 | goto out; |
358 | |
359 | /* |
360 | * Don't want to elevate referenced for mlocked page that gets this far, |
361 | * in order that it progresses to try_to_unmap and is moved to the |
362 | * unevictable list. |
363 | */ |
364 | if (vma->vm_flags & VM_LOCKED) { |
365 | *mapcount = 1; /* break early from loop */ |
366 | *vm_flags |= VM_LOCKED; |
367 | goto out_unmap; |
368 | } |
369 | |
370 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
371 | /* |
372 | * Don't treat a reference through a sequentially read |
373 | * mapping as such. If the page has been used in |
374 | * another mapping, we will catch it; if this other |
375 | * mapping is already gone, the unmap path will have |
376 | * set PG_referenced or activated the page. |
377 | */ |
378 | if (likely(!VM_SequentialReadHint(vma))) |
379 | referenced++; |
380 | } |
381 | |
382 | /* Pretend the page is referenced if the task has the |
383 | swap token and is in the middle of a page fault. */ |
384 | if (mm != current->mm && has_swap_token(mm) && |
385 | rwsem_is_locked(&mm->mmap_sem)) |
386 | referenced++; |
387 | |
388 | out_unmap: |
389 | (*mapcount)--; |
390 | pte_unmap_unlock(pte, ptl); |
391 | out: |
392 | if (referenced) |
393 | *vm_flags |= vma->vm_flags; |
394 | return referenced; |
395 | } |
396 | |
397 | static int page_referenced_anon(struct page *page, |
398 | struct mem_cgroup *mem_cont, |
399 | unsigned long *vm_flags) |
400 | { |
401 | unsigned int mapcount; |
402 | struct anon_vma *anon_vma; |
403 | struct vm_area_struct *vma; |
404 | int referenced = 0; |
405 | |
406 | anon_vma = page_lock_anon_vma(page); |
407 | if (!anon_vma) |
408 | return referenced; |
409 | |
410 | mapcount = page_mapcount(page); |
411 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { |
412 | /* |
413 | * If we are reclaiming on behalf of a cgroup, skip |
414 | * counting on behalf of references from different |
415 | * cgroups |
416 | */ |
417 | if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) |
418 | continue; |
419 | referenced += page_referenced_one(page, vma, |
420 | &mapcount, vm_flags); |
421 | if (!mapcount) |
422 | break; |
423 | } |
424 | |
425 | page_unlock_anon_vma(anon_vma); |
426 | return referenced; |
427 | } |
428 | |
429 | /** |
430 | * page_referenced_file - referenced check for object-based rmap |
431 | * @page: the page we're checking references on. |
432 | * @mem_cont: target memory controller |
433 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
434 | * |
435 | * For an object-based mapped page, find all the places it is mapped and |
436 | * check/clear the referenced flag. This is done by following the page->mapping |
437 | * pointer, then walking the chain of vmas it holds. It returns the number |
438 | * of references it found. |
439 | * |
440 | * This function is only called from page_referenced for object-based pages. |
441 | */ |
442 | static int page_referenced_file(struct page *page, |
443 | struct mem_cgroup *mem_cont, |
444 | unsigned long *vm_flags) |
445 | { |
446 | unsigned int mapcount; |
447 | struct address_space *mapping = page->mapping; |
448 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
449 | struct vm_area_struct *vma; |
450 | struct prio_tree_iter iter; |
451 | int referenced = 0; |
452 | |
453 | /* |
454 | * The caller's checks on page->mapping and !PageAnon have made |
455 | * sure that this is a file page: the check for page->mapping |
456 | * excludes the case just before it gets set on an anon page. |
457 | */ |
458 | BUG_ON(PageAnon(page)); |
459 | |
460 | /* |
461 | * The page lock not only makes sure that page->mapping cannot |
462 | * suddenly be NULLified by truncation, it makes sure that the |
463 | * structure at mapping cannot be freed and reused yet, |
464 | * so we can safely take mapping->i_mmap_lock. |
465 | */ |
466 | BUG_ON(!PageLocked(page)); |
467 | |
468 | spin_lock(&mapping->i_mmap_lock); |
469 | |
470 | /* |
471 | * i_mmap_lock does not stabilize mapcount at all, but mapcount |
472 | * is more likely to be accurate if we note it after spinning. |
473 | */ |
474 | mapcount = page_mapcount(page); |
475 | |
476 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
477 | /* |
478 | * If we are reclaiming on behalf of a cgroup, skip |
479 | * counting on behalf of references from different |
480 | * cgroups |
481 | */ |
482 | if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) |
483 | continue; |
484 | referenced += page_referenced_one(page, vma, |
485 | &mapcount, vm_flags); |
486 | if (!mapcount) |
487 | break; |
488 | } |
489 | |
490 | spin_unlock(&mapping->i_mmap_lock); |
491 | return referenced; |
492 | } |
493 | |
494 | /** |
495 | * page_referenced - test if the page was referenced |
496 | * @page: the page to test |
497 | * @is_locked: caller holds lock on the page |
498 | * @mem_cont: target memory controller |
499 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
500 | * |
501 | * Quick test_and_clear_referenced for all mappings to a page, |
502 | * returns the number of ptes which referenced the page. |
503 | */ |
504 | int page_referenced(struct page *page, |
505 | int is_locked, |
506 | struct mem_cgroup *mem_cont, |
507 | unsigned long *vm_flags) |
508 | { |
509 | int referenced = 0; |
510 | |
511 | if (TestClearPageReferenced(page)) |
512 | referenced++; |
513 | |
514 | *vm_flags = 0; |
515 | if (page_mapped(page) && page->mapping) { |
516 | if (PageAnon(page)) |
517 | referenced += page_referenced_anon(page, mem_cont, |
518 | vm_flags); |
519 | else if (is_locked) |
520 | referenced += page_referenced_file(page, mem_cont, |
521 | vm_flags); |
522 | else if (!trylock_page(page)) |
523 | referenced++; |
524 | else { |
525 | if (page->mapping) |
526 | referenced += page_referenced_file(page, |
527 | mem_cont, vm_flags); |
528 | unlock_page(page); |
529 | } |
530 | } |
531 | |
532 | if (page_test_and_clear_young(page)) |
533 | referenced++; |
534 | |
535 | return referenced; |
536 | } |
537 | |
538 | static int page_mkclean_one(struct page *page, struct vm_area_struct *vma) |
539 | { |
540 | struct mm_struct *mm = vma->vm_mm; |
541 | unsigned long address; |
542 | pte_t *pte; |
543 | spinlock_t *ptl; |
544 | int ret = 0; |
545 | |
546 | address = vma_address(page, vma); |
547 | if (address == -EFAULT) |
548 | goto out; |
549 | |
550 | pte = page_check_address(page, mm, address, &ptl, 1); |
551 | if (!pte) |
552 | goto out; |
553 | |
554 | if (pte_dirty(*pte) || pte_write(*pte)) { |
555 | pte_t entry; |
556 | |
557 | flush_cache_page(vma, address, pte_pfn(*pte)); |
558 | entry = ptep_clear_flush_notify(vma, address, pte); |
559 | entry = pte_wrprotect(entry); |
560 | entry = pte_mkclean(entry); |
561 | set_pte_at(mm, address, pte, entry); |
562 | ret = 1; |
563 | } |
564 | |
565 | pte_unmap_unlock(pte, ptl); |
566 | out: |
567 | return ret; |
568 | } |
569 | |
570 | static int page_mkclean_file(struct address_space *mapping, struct page *page) |
571 | { |
572 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
573 | struct vm_area_struct *vma; |
574 | struct prio_tree_iter iter; |
575 | int ret = 0; |
576 | |
577 | BUG_ON(PageAnon(page)); |
578 | |
579 | spin_lock(&mapping->i_mmap_lock); |
580 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
581 | if (vma->vm_flags & VM_SHARED) |
582 | ret += page_mkclean_one(page, vma); |
583 | } |
584 | spin_unlock(&mapping->i_mmap_lock); |
585 | return ret; |
586 | } |
587 | |
588 | int page_mkclean(struct page *page) |
589 | { |
590 | int ret = 0; |
591 | |
592 | BUG_ON(!PageLocked(page)); |
593 | |
594 | if (page_mapped(page)) { |
595 | struct address_space *mapping = page_mapping(page); |
596 | if (mapping) { |
597 | ret = page_mkclean_file(mapping, page); |
598 | if (page_test_dirty(page)) { |
599 | page_clear_dirty(page); |
600 | ret = 1; |
601 | } |
602 | } |
603 | } |
604 | |
605 | return ret; |
606 | } |
607 | EXPORT_SYMBOL_GPL(page_mkclean); |
608 | |
609 | /** |
610 | * __page_set_anon_rmap - setup new anonymous rmap |
611 | * @page: the page to add the mapping to |
612 | * @vma: the vm area in which the mapping is added |
613 | * @address: the user virtual address mapped |
614 | */ |
615 | static void __page_set_anon_rmap(struct page *page, |
616 | struct vm_area_struct *vma, unsigned long address) |
617 | { |
618 | struct anon_vma *anon_vma = vma->anon_vma; |
619 | |
620 | BUG_ON(!anon_vma); |
621 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
622 | page->mapping = (struct address_space *) anon_vma; |
623 | |
624 | page->index = linear_page_index(vma, address); |
625 | |
626 | /* |
627 | * nr_mapped state can be updated without turning off |
628 | * interrupts because it is not modified via interrupt. |
629 | */ |
630 | __inc_zone_page_state(page, NR_ANON_PAGES); |
631 | } |
632 | |
633 | /** |
634 | * __page_check_anon_rmap - sanity check anonymous rmap addition |
635 | * @page: the page to add the mapping to |
636 | * @vma: the vm area in which the mapping is added |
637 | * @address: the user virtual address mapped |
638 | */ |
639 | static void __page_check_anon_rmap(struct page *page, |
640 | struct vm_area_struct *vma, unsigned long address) |
641 | { |
642 | #ifdef CONFIG_DEBUG_VM |
643 | /* |
644 | * The page's anon-rmap details (mapping and index) are guaranteed to |
645 | * be set up correctly at this point. |
646 | * |
647 | * We have exclusion against page_add_anon_rmap because the caller |
648 | * always holds the page locked, except if called from page_dup_rmap, |
649 | * in which case the page is already known to be setup. |
650 | * |
651 | * We have exclusion against page_add_new_anon_rmap because those pages |
652 | * are initially only visible via the pagetables, and the pte is locked |
653 | * over the call to page_add_new_anon_rmap. |
654 | */ |
655 | struct anon_vma *anon_vma = vma->anon_vma; |
656 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
657 | BUG_ON(page->mapping != (struct address_space *)anon_vma); |
658 | BUG_ON(page->index != linear_page_index(vma, address)); |
659 | #endif |
660 | } |
661 | |
662 | /** |
663 | * page_add_anon_rmap - add pte mapping to an anonymous page |
664 | * @page: the page to add the mapping to |
665 | * @vma: the vm area in which the mapping is added |
666 | * @address: the user virtual address mapped |
667 | * |
668 | * The caller needs to hold the pte lock and the page must be locked. |
669 | */ |
670 | void page_add_anon_rmap(struct page *page, |
671 | struct vm_area_struct *vma, unsigned long address) |
672 | { |
673 | VM_BUG_ON(!PageLocked(page)); |
674 | VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
675 | if (atomic_inc_and_test(&page->_mapcount)) |
676 | __page_set_anon_rmap(page, vma, address); |
677 | else |
678 | __page_check_anon_rmap(page, vma, address); |
679 | } |
680 | |
681 | /** |
682 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page |
683 | * @page: the page to add the mapping to |
684 | * @vma: the vm area in which the mapping is added |
685 | * @address: the user virtual address mapped |
686 | * |
687 | * Same as page_add_anon_rmap but must only be called on *new* pages. |
688 | * This means the inc-and-test can be bypassed. |
689 | * Page does not have to be locked. |
690 | */ |
691 | void page_add_new_anon_rmap(struct page *page, |
692 | struct vm_area_struct *vma, unsigned long address) |
693 | { |
694 | VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
695 | SetPageSwapBacked(page); |
696 | atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */ |
697 | __page_set_anon_rmap(page, vma, address); |
698 | if (page_evictable(page, vma)) |
699 | lru_cache_add_lru(page, LRU_ACTIVE_ANON); |
700 | else |
701 | add_page_to_unevictable_list(page); |
702 | } |
703 | |
704 | /** |
705 | * page_add_file_rmap - add pte mapping to a file page |
706 | * @page: the page to add the mapping to |
707 | * |
708 | * The caller needs to hold the pte lock. |
709 | */ |
710 | void page_add_file_rmap(struct page *page) |
711 | { |
712 | if (atomic_inc_and_test(&page->_mapcount)) { |
713 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
714 | mem_cgroup_update_mapped_file_stat(page, 1); |
715 | } |
716 | } |
717 | |
718 | /** |
719 | * page_remove_rmap - take down pte mapping from a page |
720 | * @page: page to remove mapping from |
721 | * |
722 | * The caller needs to hold the pte lock. |
723 | */ |
724 | void page_remove_rmap(struct page *page) |
725 | { |
726 | /* page still mapped by someone else? */ |
727 | if (!atomic_add_negative(-1, &page->_mapcount)) |
728 | return; |
729 | |
730 | /* |
731 | * Now that the last pte has gone, s390 must transfer dirty |
732 | * flag from storage key to struct page. We can usually skip |
733 | * this if the page is anon, so about to be freed; but perhaps |
734 | * not if it's in swapcache - there might be another pte slot |
735 | * containing the swap entry, but page not yet written to swap. |
736 | */ |
737 | if ((!PageAnon(page) || PageSwapCache(page)) && page_test_dirty(page)) { |
738 | page_clear_dirty(page); |
739 | set_page_dirty(page); |
740 | } |
741 | if (PageAnon(page)) { |
742 | mem_cgroup_uncharge_page(page); |
743 | __dec_zone_page_state(page, NR_ANON_PAGES); |
744 | } else { |
745 | __dec_zone_page_state(page, NR_FILE_MAPPED); |
746 | } |
747 | mem_cgroup_update_mapped_file_stat(page, -1); |
748 | /* |
749 | * It would be tidy to reset the PageAnon mapping here, |
750 | * but that might overwrite a racing page_add_anon_rmap |
751 | * which increments mapcount after us but sets mapping |
752 | * before us: so leave the reset to free_hot_cold_page, |
753 | * and remember that it's only reliable while mapped. |
754 | * Leaving it set also helps swapoff to reinstate ptes |
755 | * faster for those pages still in swapcache. |
756 | */ |
757 | } |
758 | |
759 | /* |
760 | * Subfunctions of try_to_unmap: try_to_unmap_one called |
761 | * repeatedly from either try_to_unmap_anon or try_to_unmap_file. |
762 | */ |
763 | static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
764 | enum ttu_flags flags) |
765 | { |
766 | struct mm_struct *mm = vma->vm_mm; |
767 | unsigned long address; |
768 | pte_t *pte; |
769 | pte_t pteval; |
770 | spinlock_t *ptl; |
771 | int ret = SWAP_AGAIN; |
772 | |
773 | address = vma_address(page, vma); |
774 | if (address == -EFAULT) |
775 | goto out; |
776 | |
777 | pte = page_check_address(page, mm, address, &ptl, 0); |
778 | if (!pte) |
779 | goto out; |
780 | |
781 | /* |
782 | * If the page is mlock()d, we cannot swap it out. |
783 | * If it's recently referenced (perhaps page_referenced |
784 | * skipped over this mm) then we should reactivate it. |
785 | */ |
786 | if (!(flags & TTU_IGNORE_MLOCK)) { |
787 | if (vma->vm_flags & VM_LOCKED) { |
788 | ret = SWAP_MLOCK; |
789 | goto out_unmap; |
790 | } |
791 | } |
792 | if (!(flags & TTU_IGNORE_ACCESS)) { |
793 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
794 | ret = SWAP_FAIL; |
795 | goto out_unmap; |
796 | } |
797 | } |
798 | |
799 | /* Nuke the page table entry. */ |
800 | flush_cache_page(vma, address, page_to_pfn(page)); |
801 | pteval = ptep_clear_flush_notify(vma, address, pte); |
802 | |
803 | /* Move the dirty bit to the physical page now the pte is gone. */ |
804 | if (pte_dirty(pteval)) |
805 | set_page_dirty(page); |
806 | |
807 | /* Update high watermark before we lower rss */ |
808 | update_hiwater_rss(mm); |
809 | |
810 | if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
811 | if (PageAnon(page)) |
812 | dec_mm_counter(mm, anon_rss); |
813 | else |
814 | dec_mm_counter(mm, file_rss); |
815 | set_pte_at(mm, address, pte, |
816 | swp_entry_to_pte(make_hwpoison_entry(page))); |
817 | } else if (PageAnon(page)) { |
818 | swp_entry_t entry = { .val = page_private(page) }; |
819 | |
820 | if (PageSwapCache(page)) { |
821 | /* |
822 | * Store the swap location in the pte. |
823 | * See handle_pte_fault() ... |
824 | */ |
825 | swap_duplicate(entry); |
826 | if (list_empty(&mm->mmlist)) { |
827 | spin_lock(&mmlist_lock); |
828 | if (list_empty(&mm->mmlist)) |
829 | list_add(&mm->mmlist, &init_mm.mmlist); |
830 | spin_unlock(&mmlist_lock); |
831 | } |
832 | dec_mm_counter(mm, anon_rss); |
833 | } else if (PAGE_MIGRATION) { |
834 | /* |
835 | * Store the pfn of the page in a special migration |
836 | * pte. do_swap_page() will wait until the migration |
837 | * pte is removed and then restart fault handling. |
838 | */ |
839 | BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION); |
840 | entry = make_migration_entry(page, pte_write(pteval)); |
841 | } |
842 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
843 | BUG_ON(pte_file(*pte)); |
844 | } else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) { |
845 | /* Establish migration entry for a file page */ |
846 | swp_entry_t entry; |
847 | entry = make_migration_entry(page, pte_write(pteval)); |
848 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
849 | } else |
850 | dec_mm_counter(mm, file_rss); |
851 | |
852 | |
853 | page_remove_rmap(page); |
854 | page_cache_release(page); |
855 | |
856 | out_unmap: |
857 | pte_unmap_unlock(pte, ptl); |
858 | out: |
859 | return ret; |
860 | } |
861 | |
862 | /* |
863 | * objrmap doesn't work for nonlinear VMAs because the assumption that |
864 | * offset-into-file correlates with offset-into-virtual-addresses does not hold. |
865 | * Consequently, given a particular page and its ->index, we cannot locate the |
866 | * ptes which are mapping that page without an exhaustive linear search. |
867 | * |
868 | * So what this code does is a mini "virtual scan" of each nonlinear VMA which |
869 | * maps the file to which the target page belongs. The ->vm_private_data field |
870 | * holds the current cursor into that scan. Successive searches will circulate |
871 | * around the vma's virtual address space. |
872 | * |
873 | * So as more replacement pressure is applied to the pages in a nonlinear VMA, |
874 | * more scanning pressure is placed against them as well. Eventually pages |
875 | * will become fully unmapped and are eligible for eviction. |
876 | * |
877 | * For very sparsely populated VMAs this is a little inefficient - chances are |
878 | * there there won't be many ptes located within the scan cluster. In this case |
879 | * maybe we could scan further - to the end of the pte page, perhaps. |
880 | * |
881 | * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can |
882 | * acquire it without blocking. If vma locked, mlock the pages in the cluster, |
883 | * rather than unmapping them. If we encounter the "check_page" that vmscan is |
884 | * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN. |
885 | */ |
886 | #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) |
887 | #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) |
888 | |
889 | static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, |
890 | struct vm_area_struct *vma, struct page *check_page) |
891 | { |
892 | struct mm_struct *mm = vma->vm_mm; |
893 | pgd_t *pgd; |
894 | pud_t *pud; |
895 | pmd_t *pmd; |
896 | pte_t *pte; |
897 | pte_t pteval; |
898 | spinlock_t *ptl; |
899 | struct page *page; |
900 | unsigned long address; |
901 | unsigned long end; |
902 | int ret = SWAP_AGAIN; |
903 | int locked_vma = 0; |
904 | |
905 | address = (vma->vm_start + cursor) & CLUSTER_MASK; |
906 | end = address + CLUSTER_SIZE; |
907 | if (address < vma->vm_start) |
908 | address = vma->vm_start; |
909 | if (end > vma->vm_end) |
910 | end = vma->vm_end; |
911 | |
912 | pgd = pgd_offset(mm, address); |
913 | if (!pgd_present(*pgd)) |
914 | return ret; |
915 | |
916 | pud = pud_offset(pgd, address); |
917 | if (!pud_present(*pud)) |
918 | return ret; |
919 | |
920 | pmd = pmd_offset(pud, address); |
921 | if (!pmd_present(*pmd)) |
922 | return ret; |
923 | |
924 | /* |
925 | * MLOCK_PAGES => feature is configured. |
926 | * if we can acquire the mmap_sem for read, and vma is VM_LOCKED, |
927 | * keep the sem while scanning the cluster for mlocking pages. |
928 | */ |
929 | if (MLOCK_PAGES && down_read_trylock(&vma->vm_mm->mmap_sem)) { |
930 | locked_vma = (vma->vm_flags & VM_LOCKED); |
931 | if (!locked_vma) |
932 | up_read(&vma->vm_mm->mmap_sem); /* don't need it */ |
933 | } |
934 | |
935 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
936 | |
937 | /* Update high watermark before we lower rss */ |
938 | update_hiwater_rss(mm); |
939 | |
940 | for (; address < end; pte++, address += PAGE_SIZE) { |
941 | if (!pte_present(*pte)) |
942 | continue; |
943 | page = vm_normal_page(vma, address, *pte); |
944 | BUG_ON(!page || PageAnon(page)); |
945 | |
946 | if (locked_vma) { |
947 | mlock_vma_page(page); /* no-op if already mlocked */ |
948 | if (page == check_page) |
949 | ret = SWAP_MLOCK; |
950 | continue; /* don't unmap */ |
951 | } |
952 | |
953 | if (ptep_clear_flush_young_notify(vma, address, pte)) |
954 | continue; |
955 | |
956 | /* Nuke the page table entry. */ |
957 | flush_cache_page(vma, address, pte_pfn(*pte)); |
958 | pteval = ptep_clear_flush_notify(vma, address, pte); |
959 | |
960 | /* If nonlinear, store the file page offset in the pte. */ |
961 | if (page->index != linear_page_index(vma, address)) |
962 | set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); |
963 | |
964 | /* Move the dirty bit to the physical page now the pte is gone. */ |
965 | if (pte_dirty(pteval)) |
966 | set_page_dirty(page); |
967 | |
968 | page_remove_rmap(page); |
969 | page_cache_release(page); |
970 | dec_mm_counter(mm, file_rss); |
971 | (*mapcount)--; |
972 | } |
973 | pte_unmap_unlock(pte - 1, ptl); |
974 | if (locked_vma) |
975 | up_read(&vma->vm_mm->mmap_sem); |
976 | return ret; |
977 | } |
978 | |
979 | /* |
980 | * common handling for pages mapped in VM_LOCKED vmas |
981 | */ |
982 | static int try_to_mlock_page(struct page *page, struct vm_area_struct *vma) |
983 | { |
984 | int mlocked = 0; |
985 | |
986 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
987 | if (vma->vm_flags & VM_LOCKED) { |
988 | mlock_vma_page(page); |
989 | mlocked++; /* really mlocked the page */ |
990 | } |
991 | up_read(&vma->vm_mm->mmap_sem); |
992 | } |
993 | return mlocked; |
994 | } |
995 | |
996 | /** |
997 | * try_to_unmap_anon - unmap or unlock anonymous page using the object-based |
998 | * rmap method |
999 | * @page: the page to unmap/unlock |
1000 | * @unlock: request for unlock rather than unmap [unlikely] |
1001 | * @migration: unmapping for migration - ignored if @unlock |
1002 | * |
1003 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1004 | * contained in the anon_vma struct it points to. |
1005 | * |
1006 | * This function is only called from try_to_unmap/try_to_munlock for |
1007 | * anonymous pages. |
1008 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1009 | * where the page was found will be held for write. So, we won't recheck |
1010 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1011 | * 'LOCKED. |
1012 | */ |
1013 | static int try_to_unmap_anon(struct page *page, enum ttu_flags flags) |
1014 | { |
1015 | struct anon_vma *anon_vma; |
1016 | struct vm_area_struct *vma; |
1017 | unsigned int mlocked = 0; |
1018 | int ret = SWAP_AGAIN; |
1019 | int unlock = TTU_ACTION(flags) == TTU_MUNLOCK; |
1020 | |
1021 | if (MLOCK_PAGES && unlikely(unlock)) |
1022 | ret = SWAP_SUCCESS; /* default for try_to_munlock() */ |
1023 | |
1024 | anon_vma = page_lock_anon_vma(page); |
1025 | if (!anon_vma) |
1026 | return ret; |
1027 | |
1028 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { |
1029 | if (MLOCK_PAGES && unlikely(unlock)) { |
1030 | if (!((vma->vm_flags & VM_LOCKED) && |
1031 | page_mapped_in_vma(page, vma))) |
1032 | continue; /* must visit all unlocked vmas */ |
1033 | ret = SWAP_MLOCK; /* saw at least one mlocked vma */ |
1034 | } else { |
1035 | ret = try_to_unmap_one(page, vma, flags); |
1036 | if (ret == SWAP_FAIL || !page_mapped(page)) |
1037 | break; |
1038 | } |
1039 | if (ret == SWAP_MLOCK) { |
1040 | mlocked = try_to_mlock_page(page, vma); |
1041 | if (mlocked) |
1042 | break; /* stop if actually mlocked page */ |
1043 | } |
1044 | } |
1045 | |
1046 | page_unlock_anon_vma(anon_vma); |
1047 | |
1048 | if (mlocked) |
1049 | ret = SWAP_MLOCK; /* actually mlocked the page */ |
1050 | else if (ret == SWAP_MLOCK) |
1051 | ret = SWAP_AGAIN; /* saw VM_LOCKED vma */ |
1052 | |
1053 | return ret; |
1054 | } |
1055 | |
1056 | /** |
1057 | * try_to_unmap_file - unmap/unlock file page using the object-based rmap method |
1058 | * @page: the page to unmap/unlock |
1059 | * @flags: action and flags |
1060 | * |
1061 | * Find all the mappings of a page using the mapping pointer and the vma chains |
1062 | * contained in the address_space struct it points to. |
1063 | * |
1064 | * This function is only called from try_to_unmap/try_to_munlock for |
1065 | * object-based pages. |
1066 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
1067 | * where the page was found will be held for write. So, we won't recheck |
1068 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
1069 | * 'LOCKED. |
1070 | */ |
1071 | static int try_to_unmap_file(struct page *page, enum ttu_flags flags) |
1072 | { |
1073 | struct address_space *mapping = page->mapping; |
1074 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
1075 | struct vm_area_struct *vma; |
1076 | struct prio_tree_iter iter; |
1077 | int ret = SWAP_AGAIN; |
1078 | unsigned long cursor; |
1079 | unsigned long max_nl_cursor = 0; |
1080 | unsigned long max_nl_size = 0; |
1081 | unsigned int mapcount; |
1082 | unsigned int mlocked = 0; |
1083 | int unlock = TTU_ACTION(flags) == TTU_MUNLOCK; |
1084 | |
1085 | if (MLOCK_PAGES && unlikely(unlock)) |
1086 | ret = SWAP_SUCCESS; /* default for try_to_munlock() */ |
1087 | |
1088 | spin_lock(&mapping->i_mmap_lock); |
1089 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1090 | if (MLOCK_PAGES && unlikely(unlock)) { |
1091 | if (!((vma->vm_flags & VM_LOCKED) && |
1092 | page_mapped_in_vma(page, vma))) |
1093 | continue; /* must visit all vmas */ |
1094 | ret = SWAP_MLOCK; |
1095 | } else { |
1096 | ret = try_to_unmap_one(page, vma, flags); |
1097 | if (ret == SWAP_FAIL || !page_mapped(page)) |
1098 | goto out; |
1099 | } |
1100 | if (ret == SWAP_MLOCK) { |
1101 | mlocked = try_to_mlock_page(page, vma); |
1102 | if (mlocked) |
1103 | break; /* stop if actually mlocked page */ |
1104 | } |
1105 | } |
1106 | |
1107 | if (mlocked) |
1108 | goto out; |
1109 | |
1110 | if (list_empty(&mapping->i_mmap_nonlinear)) |
1111 | goto out; |
1112 | |
1113 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1114 | shared.vm_set.list) { |
1115 | if (MLOCK_PAGES && unlikely(unlock)) { |
1116 | if (!(vma->vm_flags & VM_LOCKED)) |
1117 | continue; /* must visit all vmas */ |
1118 | ret = SWAP_MLOCK; /* leave mlocked == 0 */ |
1119 | goto out; /* no need to look further */ |
1120 | } |
1121 | if (!MLOCK_PAGES && !(flags & TTU_IGNORE_MLOCK) && |
1122 | (vma->vm_flags & VM_LOCKED)) |
1123 | continue; |
1124 | cursor = (unsigned long) vma->vm_private_data; |
1125 | if (cursor > max_nl_cursor) |
1126 | max_nl_cursor = cursor; |
1127 | cursor = vma->vm_end - vma->vm_start; |
1128 | if (cursor > max_nl_size) |
1129 | max_nl_size = cursor; |
1130 | } |
1131 | |
1132 | if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ |
1133 | ret = SWAP_FAIL; |
1134 | goto out; |
1135 | } |
1136 | |
1137 | /* |
1138 | * We don't try to search for this page in the nonlinear vmas, |
1139 | * and page_referenced wouldn't have found it anyway. Instead |
1140 | * just walk the nonlinear vmas trying to age and unmap some. |
1141 | * The mapcount of the page we came in with is irrelevant, |
1142 | * but even so use it as a guide to how hard we should try? |
1143 | */ |
1144 | mapcount = page_mapcount(page); |
1145 | if (!mapcount) |
1146 | goto out; |
1147 | cond_resched_lock(&mapping->i_mmap_lock); |
1148 | |
1149 | max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; |
1150 | if (max_nl_cursor == 0) |
1151 | max_nl_cursor = CLUSTER_SIZE; |
1152 | |
1153 | do { |
1154 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1155 | shared.vm_set.list) { |
1156 | if (!MLOCK_PAGES && !(flags & TTU_IGNORE_MLOCK) && |
1157 | (vma->vm_flags & VM_LOCKED)) |
1158 | continue; |
1159 | cursor = (unsigned long) vma->vm_private_data; |
1160 | while ( cursor < max_nl_cursor && |
1161 | cursor < vma->vm_end - vma->vm_start) { |
1162 | ret = try_to_unmap_cluster(cursor, &mapcount, |
1163 | vma, page); |
1164 | if (ret == SWAP_MLOCK) |
1165 | mlocked = 2; /* to return below */ |
1166 | cursor += CLUSTER_SIZE; |
1167 | vma->vm_private_data = (void *) cursor; |
1168 | if ((int)mapcount <= 0) |
1169 | goto out; |
1170 | } |
1171 | vma->vm_private_data = (void *) max_nl_cursor; |
1172 | } |
1173 | cond_resched_lock(&mapping->i_mmap_lock); |
1174 | max_nl_cursor += CLUSTER_SIZE; |
1175 | } while (max_nl_cursor <= max_nl_size); |
1176 | |
1177 | /* |
1178 | * Don't loop forever (perhaps all the remaining pages are |
1179 | * in locked vmas). Reset cursor on all unreserved nonlinear |
1180 | * vmas, now forgetting on which ones it had fallen behind. |
1181 | */ |
1182 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
1183 | vma->vm_private_data = NULL; |
1184 | out: |
1185 | spin_unlock(&mapping->i_mmap_lock); |
1186 | if (mlocked) |
1187 | ret = SWAP_MLOCK; /* actually mlocked the page */ |
1188 | else if (ret == SWAP_MLOCK) |
1189 | ret = SWAP_AGAIN; /* saw VM_LOCKED vma */ |
1190 | return ret; |
1191 | } |
1192 | |
1193 | /** |
1194 | * try_to_unmap - try to remove all page table mappings to a page |
1195 | * @page: the page to get unmapped |
1196 | * @flags: action and flags |
1197 | * |
1198 | * Tries to remove all the page table entries which are mapping this |
1199 | * page, used in the pageout path. Caller must hold the page lock. |
1200 | * Return values are: |
1201 | * |
1202 | * SWAP_SUCCESS - we succeeded in removing all mappings |
1203 | * SWAP_AGAIN - we missed a mapping, try again later |
1204 | * SWAP_FAIL - the page is unswappable |
1205 | * SWAP_MLOCK - page is mlocked. |
1206 | */ |
1207 | int try_to_unmap(struct page *page, enum ttu_flags flags) |
1208 | { |
1209 | int ret; |
1210 | |
1211 | BUG_ON(!PageLocked(page)); |
1212 | |
1213 | if (PageAnon(page)) |
1214 | ret = try_to_unmap_anon(page, flags); |
1215 | else |
1216 | ret = try_to_unmap_file(page, flags); |
1217 | if (ret != SWAP_MLOCK && !page_mapped(page)) |
1218 | ret = SWAP_SUCCESS; |
1219 | return ret; |
1220 | } |
1221 | |
1222 | /** |
1223 | * try_to_munlock - try to munlock a page |
1224 | * @page: the page to be munlocked |
1225 | * |
1226 | * Called from munlock code. Checks all of the VMAs mapping the page |
1227 | * to make sure nobody else has this page mlocked. The page will be |
1228 | * returned with PG_mlocked cleared if no other vmas have it mlocked. |
1229 | * |
1230 | * Return values are: |
1231 | * |
1232 | * SWAP_SUCCESS - no vma's holding page mlocked. |
1233 | * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem |
1234 | * SWAP_MLOCK - page is now mlocked. |
1235 | */ |
1236 | int try_to_munlock(struct page *page) |
1237 | { |
1238 | VM_BUG_ON(!PageLocked(page) || PageLRU(page)); |
1239 | |
1240 | if (PageAnon(page)) |
1241 | return try_to_unmap_anon(page, TTU_MUNLOCK); |
1242 | else |
1243 | return try_to_unmap_file(page, TTU_MUNLOCK); |
1244 | } |
1245 | |
1246 |
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javiroman/ks7010
jz-2.6.34
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9