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 | * | |
1b1dcc1b | 23 | * inode->i_mutex (while writing or truncating, not reading or faulting) |
82591e6e NP |
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) | |
1da177e4 LT |
39 | */ |
40 | ||
41 | #include <linux/mm.h> | |
42 | #include <linux/pagemap.h> | |
43 | #include <linux/swap.h> | |
44 | #include <linux/swapops.h> | |
45 | #include <linux/slab.h> | |
46 | #include <linux/init.h> | |
47 | #include <linux/rmap.h> | |
48 | #include <linux/rcupdate.h> | |
a48d07af | 49 | #include <linux/module.h> |
7de6b805 | 50 | #include <linux/kallsyms.h> |
1da177e4 LT |
51 | |
52 | #include <asm/tlbflush.h> | |
53 | ||
fcc234f8 | 54 | struct kmem_cache *anon_vma_cachep; |
1da177e4 LT |
55 | |
56 | static inline void validate_anon_vma(struct vm_area_struct *find_vma) | |
57 | { | |
b7ab795b | 58 | #ifdef CONFIG_DEBUG_VM |
1da177e4 LT |
59 | struct anon_vma *anon_vma = find_vma->anon_vma; |
60 | struct vm_area_struct *vma; | |
61 | unsigned int mapcount = 0; | |
62 | int found = 0; | |
63 | ||
64 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { | |
65 | mapcount++; | |
66 | BUG_ON(mapcount > 100000); | |
67 | if (vma == find_vma) | |
68 | found = 1; | |
69 | } | |
70 | BUG_ON(!found); | |
71 | #endif | |
72 | } | |
73 | ||
74 | /* This must be called under the mmap_sem. */ | |
75 | int anon_vma_prepare(struct vm_area_struct *vma) | |
76 | { | |
77 | struct anon_vma *anon_vma = vma->anon_vma; | |
78 | ||
79 | might_sleep(); | |
80 | if (unlikely(!anon_vma)) { | |
81 | struct mm_struct *mm = vma->vm_mm; | |
82 | struct anon_vma *allocated, *locked; | |
83 | ||
84 | anon_vma = find_mergeable_anon_vma(vma); | |
85 | if (anon_vma) { | |
86 | allocated = NULL; | |
87 | locked = anon_vma; | |
88 | spin_lock(&locked->lock); | |
89 | } else { | |
90 | anon_vma = anon_vma_alloc(); | |
91 | if (unlikely(!anon_vma)) | |
92 | return -ENOMEM; | |
93 | allocated = anon_vma; | |
94 | locked = NULL; | |
95 | } | |
96 | ||
97 | /* page_table_lock to protect against threads */ | |
98 | spin_lock(&mm->page_table_lock); | |
99 | if (likely(!vma->anon_vma)) { | |
100 | vma->anon_vma = anon_vma; | |
0697212a | 101 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
1da177e4 LT |
102 | allocated = NULL; |
103 | } | |
104 | spin_unlock(&mm->page_table_lock); | |
105 | ||
106 | if (locked) | |
107 | spin_unlock(&locked->lock); | |
108 | if (unlikely(allocated)) | |
109 | anon_vma_free(allocated); | |
110 | } | |
111 | return 0; | |
112 | } | |
113 | ||
114 | void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next) | |
115 | { | |
116 | BUG_ON(vma->anon_vma != next->anon_vma); | |
117 | list_del(&next->anon_vma_node); | |
118 | } | |
119 | ||
120 | void __anon_vma_link(struct vm_area_struct *vma) | |
121 | { | |
122 | struct anon_vma *anon_vma = vma->anon_vma; | |
123 | ||
124 | if (anon_vma) { | |
0697212a | 125 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
1da177e4 LT |
126 | validate_anon_vma(vma); |
127 | } | |
128 | } | |
129 | ||
130 | void anon_vma_link(struct vm_area_struct *vma) | |
131 | { | |
132 | struct anon_vma *anon_vma = vma->anon_vma; | |
133 | ||
134 | if (anon_vma) { | |
135 | spin_lock(&anon_vma->lock); | |
0697212a | 136 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
1da177e4 LT |
137 | validate_anon_vma(vma); |
138 | spin_unlock(&anon_vma->lock); | |
139 | } | |
140 | } | |
141 | ||
142 | void anon_vma_unlink(struct vm_area_struct *vma) | |
143 | { | |
144 | struct anon_vma *anon_vma = vma->anon_vma; | |
145 | int empty; | |
146 | ||
147 | if (!anon_vma) | |
148 | return; | |
149 | ||
150 | spin_lock(&anon_vma->lock); | |
151 | validate_anon_vma(vma); | |
152 | list_del(&vma->anon_vma_node); | |
153 | ||
154 | /* We must garbage collect the anon_vma if it's empty */ | |
155 | empty = list_empty(&anon_vma->head); | |
156 | spin_unlock(&anon_vma->lock); | |
157 | ||
158 | if (empty) | |
159 | anon_vma_free(anon_vma); | |
160 | } | |
161 | ||
fcc234f8 PE |
162 | static void anon_vma_ctor(void *data, struct kmem_cache *cachep, |
163 | unsigned long flags) | |
1da177e4 | 164 | { |
50953fe9 | 165 | if (flags & SLAB_CTOR_CONSTRUCTOR) { |
1da177e4 LT |
166 | struct anon_vma *anon_vma = data; |
167 | ||
168 | spin_lock_init(&anon_vma->lock); | |
169 | INIT_LIST_HEAD(&anon_vma->head); | |
170 | } | |
171 | } | |
172 | ||
173 | void __init anon_vma_init(void) | |
174 | { | |
175 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), | |
176 | 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL); | |
177 | } | |
178 | ||
179 | /* | |
180 | * Getting a lock on a stable anon_vma from a page off the LRU is | |
181 | * tricky: page_lock_anon_vma rely on RCU to guard against the races. | |
182 | */ | |
183 | static struct anon_vma *page_lock_anon_vma(struct page *page) | |
184 | { | |
34bbd704 | 185 | struct anon_vma *anon_vma; |
1da177e4 LT |
186 | unsigned long anon_mapping; |
187 | ||
188 | rcu_read_lock(); | |
189 | anon_mapping = (unsigned long) page->mapping; | |
190 | if (!(anon_mapping & PAGE_MAPPING_ANON)) | |
191 | goto out; | |
192 | if (!page_mapped(page)) | |
193 | goto out; | |
194 | ||
195 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); | |
196 | spin_lock(&anon_vma->lock); | |
34bbd704 | 197 | return anon_vma; |
1da177e4 LT |
198 | out: |
199 | rcu_read_unlock(); | |
34bbd704 ON |
200 | return NULL; |
201 | } | |
202 | ||
203 | static void page_unlock_anon_vma(struct anon_vma *anon_vma) | |
204 | { | |
205 | spin_unlock(&anon_vma->lock); | |
206 | rcu_read_unlock(); | |
1da177e4 LT |
207 | } |
208 | ||
209 | /* | |
210 | * At what user virtual address is page expected in vma? | |
211 | */ | |
212 | static inline unsigned long | |
213 | vma_address(struct page *page, struct vm_area_struct *vma) | |
214 | { | |
215 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
216 | unsigned long address; | |
217 | ||
218 | address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); | |
219 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { | |
220 | /* page should be within any vma from prio_tree_next */ | |
221 | BUG_ON(!PageAnon(page)); | |
222 | return -EFAULT; | |
223 | } | |
224 | return address; | |
225 | } | |
226 | ||
227 | /* | |
228 | * At what user virtual address is page expected in vma? checking that the | |
ee498ed7 | 229 | * page matches the vma: currently only used on anon pages, by unuse_vma; |
1da177e4 LT |
230 | */ |
231 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) | |
232 | { | |
233 | if (PageAnon(page)) { | |
234 | if ((void *)vma->anon_vma != | |
235 | (void *)page->mapping - PAGE_MAPPING_ANON) | |
236 | return -EFAULT; | |
237 | } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { | |
ee498ed7 HD |
238 | if (!vma->vm_file || |
239 | vma->vm_file->f_mapping != page->mapping) | |
1da177e4 LT |
240 | return -EFAULT; |
241 | } else | |
242 | return -EFAULT; | |
243 | return vma_address(page, vma); | |
244 | } | |
245 | ||
81b4082d ND |
246 | /* |
247 | * Check that @page is mapped at @address into @mm. | |
248 | * | |
b8072f09 | 249 | * On success returns with pte mapped and locked. |
81b4082d | 250 | */ |
ceffc078 | 251 | pte_t *page_check_address(struct page *page, struct mm_struct *mm, |
c0718806 | 252 | unsigned long address, spinlock_t **ptlp) |
81b4082d ND |
253 | { |
254 | pgd_t *pgd; | |
255 | pud_t *pud; | |
256 | pmd_t *pmd; | |
257 | pte_t *pte; | |
c0718806 | 258 | spinlock_t *ptl; |
81b4082d | 259 | |
81b4082d | 260 | pgd = pgd_offset(mm, address); |
c0718806 HD |
261 | if (!pgd_present(*pgd)) |
262 | return NULL; | |
263 | ||
264 | pud = pud_offset(pgd, address); | |
265 | if (!pud_present(*pud)) | |
266 | return NULL; | |
267 | ||
268 | pmd = pmd_offset(pud, address); | |
269 | if (!pmd_present(*pmd)) | |
270 | return NULL; | |
271 | ||
272 | pte = pte_offset_map(pmd, address); | |
273 | /* Make a quick check before getting the lock */ | |
274 | if (!pte_present(*pte)) { | |
275 | pte_unmap(pte); | |
276 | return NULL; | |
277 | } | |
278 | ||
4c21e2f2 | 279 | ptl = pte_lockptr(mm, pmd); |
c0718806 HD |
280 | spin_lock(ptl); |
281 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { | |
282 | *ptlp = ptl; | |
283 | return pte; | |
81b4082d | 284 | } |
c0718806 HD |
285 | pte_unmap_unlock(pte, ptl); |
286 | return NULL; | |
81b4082d ND |
287 | } |
288 | ||
1da177e4 LT |
289 | /* |
290 | * Subfunctions of page_referenced: page_referenced_one called | |
291 | * repeatedly from either page_referenced_anon or page_referenced_file. | |
292 | */ | |
293 | static int page_referenced_one(struct page *page, | |
f7b7fd8f | 294 | struct vm_area_struct *vma, unsigned int *mapcount) |
1da177e4 LT |
295 | { |
296 | struct mm_struct *mm = vma->vm_mm; | |
297 | unsigned long address; | |
1da177e4 | 298 | pte_t *pte; |
c0718806 | 299 | spinlock_t *ptl; |
1da177e4 LT |
300 | int referenced = 0; |
301 | ||
1da177e4 LT |
302 | address = vma_address(page, vma); |
303 | if (address == -EFAULT) | |
304 | goto out; | |
305 | ||
c0718806 HD |
306 | pte = page_check_address(page, mm, address, &ptl); |
307 | if (!pte) | |
308 | goto out; | |
1da177e4 | 309 | |
c0718806 HD |
310 | if (ptep_clear_flush_young(vma, address, pte)) |
311 | referenced++; | |
1da177e4 | 312 | |
c0718806 HD |
313 | /* Pretend the page is referenced if the task has the |
314 | swap token and is in the middle of a page fault. */ | |
f7b7fd8f | 315 | if (mm != current->mm && has_swap_token(mm) && |
c0718806 HD |
316 | rwsem_is_locked(&mm->mmap_sem)) |
317 | referenced++; | |
318 | ||
319 | (*mapcount)--; | |
320 | pte_unmap_unlock(pte, ptl); | |
1da177e4 LT |
321 | out: |
322 | return referenced; | |
323 | } | |
324 | ||
f7b7fd8f | 325 | static int page_referenced_anon(struct page *page) |
1da177e4 LT |
326 | { |
327 | unsigned int mapcount; | |
328 | struct anon_vma *anon_vma; | |
329 | struct vm_area_struct *vma; | |
330 | int referenced = 0; | |
331 | ||
332 | anon_vma = page_lock_anon_vma(page); | |
333 | if (!anon_vma) | |
334 | return referenced; | |
335 | ||
336 | mapcount = page_mapcount(page); | |
337 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { | |
f7b7fd8f | 338 | referenced += page_referenced_one(page, vma, &mapcount); |
1da177e4 LT |
339 | if (!mapcount) |
340 | break; | |
341 | } | |
34bbd704 ON |
342 | |
343 | page_unlock_anon_vma(anon_vma); | |
1da177e4 LT |
344 | return referenced; |
345 | } | |
346 | ||
347 | /** | |
348 | * page_referenced_file - referenced check for object-based rmap | |
349 | * @page: the page we're checking references on. | |
350 | * | |
351 | * For an object-based mapped page, find all the places it is mapped and | |
352 | * check/clear the referenced flag. This is done by following the page->mapping | |
353 | * pointer, then walking the chain of vmas it holds. It returns the number | |
354 | * of references it found. | |
355 | * | |
356 | * This function is only called from page_referenced for object-based pages. | |
357 | */ | |
f7b7fd8f | 358 | static int page_referenced_file(struct page *page) |
1da177e4 LT |
359 | { |
360 | unsigned int mapcount; | |
361 | struct address_space *mapping = page->mapping; | |
362 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
363 | struct vm_area_struct *vma; | |
364 | struct prio_tree_iter iter; | |
365 | int referenced = 0; | |
366 | ||
367 | /* | |
368 | * The caller's checks on page->mapping and !PageAnon have made | |
369 | * sure that this is a file page: the check for page->mapping | |
370 | * excludes the case just before it gets set on an anon page. | |
371 | */ | |
372 | BUG_ON(PageAnon(page)); | |
373 | ||
374 | /* | |
375 | * The page lock not only makes sure that page->mapping cannot | |
376 | * suddenly be NULLified by truncation, it makes sure that the | |
377 | * structure at mapping cannot be freed and reused yet, | |
378 | * so we can safely take mapping->i_mmap_lock. | |
379 | */ | |
380 | BUG_ON(!PageLocked(page)); | |
381 | ||
382 | spin_lock(&mapping->i_mmap_lock); | |
383 | ||
384 | /* | |
385 | * i_mmap_lock does not stabilize mapcount at all, but mapcount | |
386 | * is more likely to be accurate if we note it after spinning. | |
387 | */ | |
388 | mapcount = page_mapcount(page); | |
389 | ||
390 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { | |
391 | if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE)) | |
392 | == (VM_LOCKED|VM_MAYSHARE)) { | |
393 | referenced++; | |
394 | break; | |
395 | } | |
f7b7fd8f | 396 | referenced += page_referenced_one(page, vma, &mapcount); |
1da177e4 LT |
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 | */ | |
f7b7fd8f | 413 | int page_referenced(struct page *page, int is_locked) |
1da177e4 LT |
414 | { |
415 | int referenced = 0; | |
416 | ||
1da177e4 LT |
417 | if (page_test_and_clear_young(page)) |
418 | referenced++; | |
419 | ||
420 | if (TestClearPageReferenced(page)) | |
421 | referenced++; | |
422 | ||
423 | if (page_mapped(page) && page->mapping) { | |
424 | if (PageAnon(page)) | |
f7b7fd8f | 425 | referenced += page_referenced_anon(page); |
1da177e4 | 426 | else if (is_locked) |
f7b7fd8f | 427 | referenced += page_referenced_file(page); |
1da177e4 LT |
428 | else if (TestSetPageLocked(page)) |
429 | referenced++; | |
430 | else { | |
431 | if (page->mapping) | |
f7b7fd8f | 432 | referenced += page_referenced_file(page); |
1da177e4 LT |
433 | unlock_page(page); |
434 | } | |
435 | } | |
436 | return referenced; | |
437 | } | |
438 | ||
d08b3851 PZ |
439 | static int page_mkclean_one(struct page *page, struct vm_area_struct *vma) |
440 | { | |
441 | struct mm_struct *mm = vma->vm_mm; | |
442 | unsigned long address; | |
c2fda5fe | 443 | pte_t *pte; |
d08b3851 PZ |
444 | spinlock_t *ptl; |
445 | int ret = 0; | |
446 | ||
447 | address = vma_address(page, vma); | |
448 | if (address == -EFAULT) | |
449 | goto out; | |
450 | ||
451 | pte = page_check_address(page, mm, address, &ptl); | |
452 | if (!pte) | |
453 | goto out; | |
454 | ||
c2fda5fe PZ |
455 | if (pte_dirty(*pte) || pte_write(*pte)) { |
456 | pte_t entry; | |
d08b3851 | 457 | |
c2fda5fe PZ |
458 | flush_cache_page(vma, address, pte_pfn(*pte)); |
459 | entry = ptep_clear_flush(vma, address, pte); | |
460 | entry = pte_wrprotect(entry); | |
461 | entry = pte_mkclean(entry); | |
d6e88e67 | 462 | set_pte_at(mm, address, pte, entry); |
c2fda5fe PZ |
463 | lazy_mmu_prot_update(entry); |
464 | ret = 1; | |
465 | } | |
d08b3851 | 466 | |
d08b3851 PZ |
467 | pte_unmap_unlock(pte, ptl); |
468 | out: | |
469 | return ret; | |
470 | } | |
471 | ||
472 | static int page_mkclean_file(struct address_space *mapping, struct page *page) | |
473 | { | |
474 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
475 | struct vm_area_struct *vma; | |
476 | struct prio_tree_iter iter; | |
477 | int ret = 0; | |
478 | ||
479 | BUG_ON(PageAnon(page)); | |
480 | ||
481 | spin_lock(&mapping->i_mmap_lock); | |
482 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { | |
483 | if (vma->vm_flags & VM_SHARED) | |
484 | ret += page_mkclean_one(page, vma); | |
485 | } | |
486 | spin_unlock(&mapping->i_mmap_lock); | |
487 | return ret; | |
488 | } | |
489 | ||
490 | int page_mkclean(struct page *page) | |
491 | { | |
492 | int ret = 0; | |
493 | ||
494 | BUG_ON(!PageLocked(page)); | |
495 | ||
496 | if (page_mapped(page)) { | |
497 | struct address_space *mapping = page_mapping(page); | |
498 | if (mapping) | |
499 | ret = page_mkclean_file(mapping, page); | |
6c210482 MS |
500 | if (page_test_dirty(page)) { |
501 | page_clear_dirty(page); | |
6e1beb3c | 502 | ret = 1; |
6c210482 | 503 | } |
d08b3851 PZ |
504 | } |
505 | ||
506 | return ret; | |
507 | } | |
60b59bea | 508 | EXPORT_SYMBOL_GPL(page_mkclean); |
d08b3851 | 509 | |
9617d95e NP |
510 | /** |
511 | * page_set_anon_rmap - setup new anonymous rmap | |
512 | * @page: the page to add the mapping to | |
513 | * @vma: the vm area in which the mapping is added | |
514 | * @address: the user virtual address mapped | |
515 | */ | |
516 | static void __page_set_anon_rmap(struct page *page, | |
517 | struct vm_area_struct *vma, unsigned long address) | |
518 | { | |
519 | struct anon_vma *anon_vma = vma->anon_vma; | |
520 | ||
521 | BUG_ON(!anon_vma); | |
522 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; | |
523 | page->mapping = (struct address_space *) anon_vma; | |
524 | ||
525 | page->index = linear_page_index(vma, address); | |
526 | ||
a74609fa NP |
527 | /* |
528 | * nr_mapped state can be updated without turning off | |
529 | * interrupts because it is not modified via interrupt. | |
530 | */ | |
f3dbd344 | 531 | __inc_zone_page_state(page, NR_ANON_PAGES); |
9617d95e NP |
532 | } |
533 | ||
1da177e4 LT |
534 | /** |
535 | * page_add_anon_rmap - add pte mapping to an anonymous page | |
536 | * @page: the page to add the mapping to | |
537 | * @vma: the vm area in which the mapping is added | |
538 | * @address: the user virtual address mapped | |
539 | * | |
b8072f09 | 540 | * The caller needs to hold the pte lock. |
1da177e4 LT |
541 | */ |
542 | void page_add_anon_rmap(struct page *page, | |
543 | struct vm_area_struct *vma, unsigned long address) | |
544 | { | |
9617d95e NP |
545 | if (atomic_inc_and_test(&page->_mapcount)) |
546 | __page_set_anon_rmap(page, vma, address); | |
1da177e4 LT |
547 | /* else checking page index and mapping is racy */ |
548 | } | |
549 | ||
9617d95e NP |
550 | /* |
551 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page | |
552 | * @page: the page to add the mapping to | |
553 | * @vma: the vm area in which the mapping is added | |
554 | * @address: the user virtual address mapped | |
555 | * | |
556 | * Same as page_add_anon_rmap but must only be called on *new* pages. | |
557 | * This means the inc-and-test can be bypassed. | |
558 | */ | |
559 | void page_add_new_anon_rmap(struct page *page, | |
560 | struct vm_area_struct *vma, unsigned long address) | |
561 | { | |
562 | atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */ | |
563 | __page_set_anon_rmap(page, vma, address); | |
564 | } | |
565 | ||
1da177e4 LT |
566 | /** |
567 | * page_add_file_rmap - add pte mapping to a file page | |
568 | * @page: the page to add the mapping to | |
569 | * | |
b8072f09 | 570 | * The caller needs to hold the pte lock. |
1da177e4 LT |
571 | */ |
572 | void page_add_file_rmap(struct page *page) | |
573 | { | |
1da177e4 | 574 | if (atomic_inc_and_test(&page->_mapcount)) |
65ba55f5 | 575 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
1da177e4 LT |
576 | } |
577 | ||
578 | /** | |
579 | * page_remove_rmap - take down pte mapping from a page | |
580 | * @page: page to remove mapping from | |
581 | * | |
b8072f09 | 582 | * The caller needs to hold the pte lock. |
1da177e4 | 583 | */ |
7de6b805 | 584 | void page_remove_rmap(struct page *page, struct vm_area_struct *vma) |
1da177e4 | 585 | { |
1da177e4 | 586 | if (atomic_add_negative(-1, &page->_mapcount)) { |
b7ab795b | 587 | if (unlikely(page_mapcount(page) < 0)) { |
ef2bf0dc | 588 | printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page)); |
7de6b805 | 589 | printk (KERN_EMERG " page pfn = %lx\n", page_to_pfn(page)); |
ef2bf0dc DJ |
590 | printk (KERN_EMERG " page->flags = %lx\n", page->flags); |
591 | printk (KERN_EMERG " page->count = %x\n", page_count(page)); | |
592 | printk (KERN_EMERG " page->mapping = %p\n", page->mapping); | |
7de6b805 NP |
593 | print_symbol (KERN_EMERG " vma->vm_ops = %s\n", (unsigned long)vma->vm_ops); |
594 | if (vma->vm_ops) | |
595 | print_symbol (KERN_EMERG " vma->vm_ops->nopage = %s\n", (unsigned long)vma->vm_ops->nopage); | |
596 | if (vma->vm_file && vma->vm_file->f_op) | |
597 | print_symbol (KERN_EMERG " vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma->vm_file->f_op->mmap); | |
b16bc64d | 598 | BUG(); |
ef2bf0dc | 599 | } |
b16bc64d | 600 | |
1da177e4 LT |
601 | /* |
602 | * It would be tidy to reset the PageAnon mapping here, | |
603 | * but that might overwrite a racing page_add_anon_rmap | |
604 | * which increments mapcount after us but sets mapping | |
605 | * before us: so leave the reset to free_hot_cold_page, | |
606 | * and remember that it's only reliable while mapped. | |
607 | * Leaving it set also helps swapoff to reinstate ptes | |
608 | * faster for those pages still in swapcache. | |
609 | */ | |
6c210482 MS |
610 | if (page_test_dirty(page)) { |
611 | page_clear_dirty(page); | |
1da177e4 | 612 | set_page_dirty(page); |
6c210482 | 613 | } |
f3dbd344 CL |
614 | __dec_zone_page_state(page, |
615 | PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED); | |
1da177e4 LT |
616 | } |
617 | } | |
618 | ||
619 | /* | |
620 | * Subfunctions of try_to_unmap: try_to_unmap_one called | |
621 | * repeatedly from either try_to_unmap_anon or try_to_unmap_file. | |
622 | */ | |
a48d07af | 623 | static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
7352349a | 624 | int migration) |
1da177e4 LT |
625 | { |
626 | struct mm_struct *mm = vma->vm_mm; | |
627 | unsigned long address; | |
1da177e4 LT |
628 | pte_t *pte; |
629 | pte_t pteval; | |
c0718806 | 630 | spinlock_t *ptl; |
1da177e4 LT |
631 | int ret = SWAP_AGAIN; |
632 | ||
1da177e4 LT |
633 | address = vma_address(page, vma); |
634 | if (address == -EFAULT) | |
635 | goto out; | |
636 | ||
c0718806 HD |
637 | pte = page_check_address(page, mm, address, &ptl); |
638 | if (!pte) | |
81b4082d | 639 | goto out; |
1da177e4 LT |
640 | |
641 | /* | |
642 | * If the page is mlock()d, we cannot swap it out. | |
643 | * If it's recently referenced (perhaps page_referenced | |
644 | * skipped over this mm) then we should reactivate it. | |
645 | */ | |
e6a1530d CL |
646 | if (!migration && ((vma->vm_flags & VM_LOCKED) || |
647 | (ptep_clear_flush_young(vma, address, pte)))) { | |
1da177e4 LT |
648 | ret = SWAP_FAIL; |
649 | goto out_unmap; | |
650 | } | |
651 | ||
1da177e4 LT |
652 | /* Nuke the page table entry. */ |
653 | flush_cache_page(vma, address, page_to_pfn(page)); | |
654 | pteval = ptep_clear_flush(vma, address, pte); | |
655 | ||
656 | /* Move the dirty bit to the physical page now the pte is gone. */ | |
657 | if (pte_dirty(pteval)) | |
658 | set_page_dirty(page); | |
659 | ||
365e9c87 HD |
660 | /* Update high watermark before we lower rss */ |
661 | update_hiwater_rss(mm); | |
662 | ||
1da177e4 | 663 | if (PageAnon(page)) { |
4c21e2f2 | 664 | swp_entry_t entry = { .val = page_private(page) }; |
0697212a CL |
665 | |
666 | if (PageSwapCache(page)) { | |
667 | /* | |
668 | * Store the swap location in the pte. | |
669 | * See handle_pte_fault() ... | |
670 | */ | |
671 | swap_duplicate(entry); | |
672 | if (list_empty(&mm->mmlist)) { | |
673 | spin_lock(&mmlist_lock); | |
674 | if (list_empty(&mm->mmlist)) | |
675 | list_add(&mm->mmlist, &init_mm.mmlist); | |
676 | spin_unlock(&mmlist_lock); | |
677 | } | |
442c9137 | 678 | dec_mm_counter(mm, anon_rss); |
04e62a29 | 679 | #ifdef CONFIG_MIGRATION |
0697212a CL |
680 | } else { |
681 | /* | |
682 | * Store the pfn of the page in a special migration | |
683 | * pte. do_swap_page() will wait until the migration | |
684 | * pte is removed and then restart fault handling. | |
685 | */ | |
686 | BUG_ON(!migration); | |
687 | entry = make_migration_entry(page, pte_write(pteval)); | |
04e62a29 | 688 | #endif |
1da177e4 LT |
689 | } |
690 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); | |
691 | BUG_ON(pte_file(*pte)); | |
4294621f | 692 | } else |
04e62a29 CL |
693 | #ifdef CONFIG_MIGRATION |
694 | if (migration) { | |
695 | /* Establish migration entry for a file page */ | |
696 | swp_entry_t entry; | |
697 | entry = make_migration_entry(page, pte_write(pteval)); | |
698 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); | |
699 | } else | |
700 | #endif | |
4294621f | 701 | dec_mm_counter(mm, file_rss); |
1da177e4 | 702 | |
04e62a29 | 703 | |
7de6b805 | 704 | page_remove_rmap(page, vma); |
1da177e4 LT |
705 | page_cache_release(page); |
706 | ||
707 | out_unmap: | |
c0718806 | 708 | pte_unmap_unlock(pte, ptl); |
1da177e4 LT |
709 | out: |
710 | return ret; | |
711 | } | |
712 | ||
713 | /* | |
714 | * objrmap doesn't work for nonlinear VMAs because the assumption that | |
715 | * offset-into-file correlates with offset-into-virtual-addresses does not hold. | |
716 | * Consequently, given a particular page and its ->index, we cannot locate the | |
717 | * ptes which are mapping that page without an exhaustive linear search. | |
718 | * | |
719 | * So what this code does is a mini "virtual scan" of each nonlinear VMA which | |
720 | * maps the file to which the target page belongs. The ->vm_private_data field | |
721 | * holds the current cursor into that scan. Successive searches will circulate | |
722 | * around the vma's virtual address space. | |
723 | * | |
724 | * So as more replacement pressure is applied to the pages in a nonlinear VMA, | |
725 | * more scanning pressure is placed against them as well. Eventually pages | |
726 | * will become fully unmapped and are eligible for eviction. | |
727 | * | |
728 | * For very sparsely populated VMAs this is a little inefficient - chances are | |
729 | * there there won't be many ptes located within the scan cluster. In this case | |
730 | * maybe we could scan further - to the end of the pte page, perhaps. | |
731 | */ | |
732 | #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) | |
733 | #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) | |
734 | ||
735 | static void try_to_unmap_cluster(unsigned long cursor, | |
736 | unsigned int *mapcount, struct vm_area_struct *vma) | |
737 | { | |
738 | struct mm_struct *mm = vma->vm_mm; | |
739 | pgd_t *pgd; | |
740 | pud_t *pud; | |
741 | pmd_t *pmd; | |
c0718806 | 742 | pte_t *pte; |
1da177e4 | 743 | pte_t pteval; |
c0718806 | 744 | spinlock_t *ptl; |
1da177e4 LT |
745 | struct page *page; |
746 | unsigned long address; | |
747 | unsigned long end; | |
1da177e4 | 748 | |
1da177e4 LT |
749 | address = (vma->vm_start + cursor) & CLUSTER_MASK; |
750 | end = address + CLUSTER_SIZE; | |
751 | if (address < vma->vm_start) | |
752 | address = vma->vm_start; | |
753 | if (end > vma->vm_end) | |
754 | end = vma->vm_end; | |
755 | ||
756 | pgd = pgd_offset(mm, address); | |
757 | if (!pgd_present(*pgd)) | |
c0718806 | 758 | return; |
1da177e4 LT |
759 | |
760 | pud = pud_offset(pgd, address); | |
761 | if (!pud_present(*pud)) | |
c0718806 | 762 | return; |
1da177e4 LT |
763 | |
764 | pmd = pmd_offset(pud, address); | |
765 | if (!pmd_present(*pmd)) | |
c0718806 HD |
766 | return; |
767 | ||
768 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); | |
1da177e4 | 769 | |
365e9c87 HD |
770 | /* Update high watermark before we lower rss */ |
771 | update_hiwater_rss(mm); | |
772 | ||
c0718806 | 773 | for (; address < end; pte++, address += PAGE_SIZE) { |
1da177e4 LT |
774 | if (!pte_present(*pte)) |
775 | continue; | |
6aab341e LT |
776 | page = vm_normal_page(vma, address, *pte); |
777 | BUG_ON(!page || PageAnon(page)); | |
1da177e4 LT |
778 | |
779 | if (ptep_clear_flush_young(vma, address, pte)) | |
780 | continue; | |
781 | ||
782 | /* Nuke the page table entry. */ | |
eca35133 | 783 | flush_cache_page(vma, address, pte_pfn(*pte)); |
1da177e4 LT |
784 | pteval = ptep_clear_flush(vma, address, pte); |
785 | ||
786 | /* If nonlinear, store the file page offset in the pte. */ | |
787 | if (page->index != linear_page_index(vma, address)) | |
788 | set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); | |
789 | ||
790 | /* Move the dirty bit to the physical page now the pte is gone. */ | |
791 | if (pte_dirty(pteval)) | |
792 | set_page_dirty(page); | |
793 | ||
7de6b805 | 794 | page_remove_rmap(page, vma); |
1da177e4 | 795 | page_cache_release(page); |
4294621f | 796 | dec_mm_counter(mm, file_rss); |
1da177e4 LT |
797 | (*mapcount)--; |
798 | } | |
c0718806 | 799 | pte_unmap_unlock(pte - 1, ptl); |
1da177e4 LT |
800 | } |
801 | ||
7352349a | 802 | static int try_to_unmap_anon(struct page *page, int migration) |
1da177e4 LT |
803 | { |
804 | struct anon_vma *anon_vma; | |
805 | struct vm_area_struct *vma; | |
806 | int ret = SWAP_AGAIN; | |
807 | ||
808 | anon_vma = page_lock_anon_vma(page); | |
809 | if (!anon_vma) | |
810 | return ret; | |
811 | ||
812 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { | |
7352349a | 813 | ret = try_to_unmap_one(page, vma, migration); |
1da177e4 LT |
814 | if (ret == SWAP_FAIL || !page_mapped(page)) |
815 | break; | |
816 | } | |
34bbd704 ON |
817 | |
818 | page_unlock_anon_vma(anon_vma); | |
1da177e4 LT |
819 | return ret; |
820 | } | |
821 | ||
822 | /** | |
823 | * try_to_unmap_file - unmap file page using the object-based rmap method | |
824 | * @page: the page to unmap | |
825 | * | |
826 | * Find all the mappings of a page using the mapping pointer and the vma chains | |
827 | * contained in the address_space struct it points to. | |
828 | * | |
829 | * This function is only called from try_to_unmap for object-based pages. | |
830 | */ | |
7352349a | 831 | static int try_to_unmap_file(struct page *page, int migration) |
1da177e4 LT |
832 | { |
833 | struct address_space *mapping = page->mapping; | |
834 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
835 | struct vm_area_struct *vma; | |
836 | struct prio_tree_iter iter; | |
837 | int ret = SWAP_AGAIN; | |
838 | unsigned long cursor; | |
839 | unsigned long max_nl_cursor = 0; | |
840 | unsigned long max_nl_size = 0; | |
841 | unsigned int mapcount; | |
842 | ||
843 | spin_lock(&mapping->i_mmap_lock); | |
844 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { | |
7352349a | 845 | ret = try_to_unmap_one(page, vma, migration); |
1da177e4 LT |
846 | if (ret == SWAP_FAIL || !page_mapped(page)) |
847 | goto out; | |
848 | } | |
849 | ||
850 | if (list_empty(&mapping->i_mmap_nonlinear)) | |
851 | goto out; | |
852 | ||
853 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, | |
854 | shared.vm_set.list) { | |
e6a1530d | 855 | if ((vma->vm_flags & VM_LOCKED) && !migration) |
1da177e4 LT |
856 | continue; |
857 | cursor = (unsigned long) vma->vm_private_data; | |
858 | if (cursor > max_nl_cursor) | |
859 | max_nl_cursor = cursor; | |
860 | cursor = vma->vm_end - vma->vm_start; | |
861 | if (cursor > max_nl_size) | |
862 | max_nl_size = cursor; | |
863 | } | |
864 | ||
865 | if (max_nl_size == 0) { /* any nonlinears locked or reserved */ | |
866 | ret = SWAP_FAIL; | |
867 | goto out; | |
868 | } | |
869 | ||
870 | /* | |
871 | * We don't try to search for this page in the nonlinear vmas, | |
872 | * and page_referenced wouldn't have found it anyway. Instead | |
873 | * just walk the nonlinear vmas trying to age and unmap some. | |
874 | * The mapcount of the page we came in with is irrelevant, | |
875 | * but even so use it as a guide to how hard we should try? | |
876 | */ | |
877 | mapcount = page_mapcount(page); | |
878 | if (!mapcount) | |
879 | goto out; | |
880 | cond_resched_lock(&mapping->i_mmap_lock); | |
881 | ||
882 | max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; | |
883 | if (max_nl_cursor == 0) | |
884 | max_nl_cursor = CLUSTER_SIZE; | |
885 | ||
886 | do { | |
887 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, | |
888 | shared.vm_set.list) { | |
e6a1530d | 889 | if ((vma->vm_flags & VM_LOCKED) && !migration) |
1da177e4 LT |
890 | continue; |
891 | cursor = (unsigned long) vma->vm_private_data; | |
839b9685 | 892 | while ( cursor < max_nl_cursor && |
1da177e4 LT |
893 | cursor < vma->vm_end - vma->vm_start) { |
894 | try_to_unmap_cluster(cursor, &mapcount, vma); | |
895 | cursor += CLUSTER_SIZE; | |
896 | vma->vm_private_data = (void *) cursor; | |
897 | if ((int)mapcount <= 0) | |
898 | goto out; | |
899 | } | |
900 | vma->vm_private_data = (void *) max_nl_cursor; | |
901 | } | |
902 | cond_resched_lock(&mapping->i_mmap_lock); | |
903 | max_nl_cursor += CLUSTER_SIZE; | |
904 | } while (max_nl_cursor <= max_nl_size); | |
905 | ||
906 | /* | |
907 | * Don't loop forever (perhaps all the remaining pages are | |
908 | * in locked vmas). Reset cursor on all unreserved nonlinear | |
909 | * vmas, now forgetting on which ones it had fallen behind. | |
910 | */ | |
101d2be7 HD |
911 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
912 | vma->vm_private_data = NULL; | |
1da177e4 LT |
913 | out: |
914 | spin_unlock(&mapping->i_mmap_lock); | |
915 | return ret; | |
916 | } | |
917 | ||
918 | /** | |
919 | * try_to_unmap - try to remove all page table mappings to a page | |
920 | * @page: the page to get unmapped | |
921 | * | |
922 | * Tries to remove all the page table entries which are mapping this | |
923 | * page, used in the pageout path. Caller must hold the page lock. | |
924 | * Return values are: | |
925 | * | |
926 | * SWAP_SUCCESS - we succeeded in removing all mappings | |
927 | * SWAP_AGAIN - we missed a mapping, try again later | |
928 | * SWAP_FAIL - the page is unswappable | |
929 | */ | |
7352349a | 930 | int try_to_unmap(struct page *page, int migration) |
1da177e4 LT |
931 | { |
932 | int ret; | |
933 | ||
1da177e4 LT |
934 | BUG_ON(!PageLocked(page)); |
935 | ||
936 | if (PageAnon(page)) | |
7352349a | 937 | ret = try_to_unmap_anon(page, migration); |
1da177e4 | 938 | else |
7352349a | 939 | ret = try_to_unmap_file(page, migration); |
1da177e4 LT |
940 | |
941 | if (!page_mapped(page)) | |
942 | ret = SWAP_SUCCESS; | |
943 | return ret; | |
944 | } | |
81b4082d | 945 |