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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 | |
98f32602 | 17 | * Contributions by Hugh Dickins 2003, 2004 |
1da177e4 LT |
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) | |
3d48ae45 | 27 | * mapping->i_mmap_mutex |
2b575eb6 | 28 | * anon_vma->mutex |
82591e6e NP |
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) | |
250df6ed | 34 | * inode->i_lock (in set_page_dirty's __mark_inode_dirty) |
a66979ab | 35 | * inode_wb_list_lock (in set_page_dirty's __mark_inode_dirty) |
82591e6e NP |
36 | * sb_lock (within inode_lock in fs/fs-writeback.c) |
37 | * mapping->tree_lock (widely used, in set_page_dirty, | |
38 | * in arch-dependent flush_dcache_mmap_lock, | |
a66979ab | 39 | * within inode_wb_list_lock in __sync_single_inode) |
6a46079c AK |
40 | * |
41 | * (code doesn't rely on that order so it could be switched around) | |
42 | * ->tasklist_lock | |
2b575eb6 | 43 | * anon_vma->mutex (memory_failure, collect_procs_anon) |
6a46079c | 44 | * pte map lock |
1da177e4 LT |
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> | |
5ad64688 | 53 | #include <linux/ksm.h> |
1da177e4 LT |
54 | #include <linux/rmap.h> |
55 | #include <linux/rcupdate.h> | |
a48d07af | 56 | #include <linux/module.h> |
8a9f3ccd | 57 | #include <linux/memcontrol.h> |
cddb8a5c | 58 | #include <linux/mmu_notifier.h> |
64cdd548 | 59 | #include <linux/migrate.h> |
0fe6e20b | 60 | #include <linux/hugetlb.h> |
1da177e4 LT |
61 | |
62 | #include <asm/tlbflush.h> | |
63 | ||
b291f000 NP |
64 | #include "internal.h" |
65 | ||
fdd2e5f8 | 66 | static struct kmem_cache *anon_vma_cachep; |
5beb4930 | 67 | static struct kmem_cache *anon_vma_chain_cachep; |
fdd2e5f8 AB |
68 | |
69 | static inline struct anon_vma *anon_vma_alloc(void) | |
70 | { | |
01d8b20d PZ |
71 | struct anon_vma *anon_vma; |
72 | ||
73 | anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); | |
74 | if (anon_vma) { | |
75 | atomic_set(&anon_vma->refcount, 1); | |
76 | /* | |
77 | * Initialise the anon_vma root to point to itself. If called | |
78 | * from fork, the root will be reset to the parents anon_vma. | |
79 | */ | |
80 | anon_vma->root = anon_vma; | |
81 | } | |
82 | ||
83 | return anon_vma; | |
fdd2e5f8 AB |
84 | } |
85 | ||
01d8b20d | 86 | static inline void anon_vma_free(struct anon_vma *anon_vma) |
fdd2e5f8 | 87 | { |
01d8b20d | 88 | VM_BUG_ON(atomic_read(&anon_vma->refcount)); |
88c22088 PZ |
89 | |
90 | /* | |
91 | * Synchronize against page_lock_anon_vma() such that | |
92 | * we can safely hold the lock without the anon_vma getting | |
93 | * freed. | |
94 | * | |
95 | * Relies on the full mb implied by the atomic_dec_and_test() from | |
96 | * put_anon_vma() against the acquire barrier implied by | |
97 | * mutex_trylock() from page_lock_anon_vma(). This orders: | |
98 | * | |
99 | * page_lock_anon_vma() VS put_anon_vma() | |
100 | * mutex_trylock() atomic_dec_and_test() | |
101 | * LOCK MB | |
102 | * atomic_read() mutex_is_locked() | |
103 | * | |
104 | * LOCK should suffice since the actual taking of the lock must | |
105 | * happen _before_ what follows. | |
106 | */ | |
107 | if (mutex_is_locked(&anon_vma->root->mutex)) { | |
108 | anon_vma_lock(anon_vma); | |
109 | anon_vma_unlock(anon_vma); | |
110 | } | |
111 | ||
fdd2e5f8 AB |
112 | kmem_cache_free(anon_vma_cachep, anon_vma); |
113 | } | |
1da177e4 | 114 | |
dd34739c | 115 | static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp) |
5beb4930 | 116 | { |
dd34739c | 117 | return kmem_cache_alloc(anon_vma_chain_cachep, gfp); |
5beb4930 RR |
118 | } |
119 | ||
e574b5fd | 120 | static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain) |
5beb4930 RR |
121 | { |
122 | kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain); | |
123 | } | |
124 | ||
d9d332e0 LT |
125 | /** |
126 | * anon_vma_prepare - attach an anon_vma to a memory region | |
127 | * @vma: the memory region in question | |
128 | * | |
129 | * This makes sure the memory mapping described by 'vma' has | |
130 | * an 'anon_vma' attached to it, so that we can associate the | |
131 | * anonymous pages mapped into it with that anon_vma. | |
132 | * | |
133 | * The common case will be that we already have one, but if | |
23a0790a | 134 | * not we either need to find an adjacent mapping that we |
d9d332e0 LT |
135 | * can re-use the anon_vma from (very common when the only |
136 | * reason for splitting a vma has been mprotect()), or we | |
137 | * allocate a new one. | |
138 | * | |
139 | * Anon-vma allocations are very subtle, because we may have | |
140 | * optimistically looked up an anon_vma in page_lock_anon_vma() | |
141 | * and that may actually touch the spinlock even in the newly | |
142 | * allocated vma (it depends on RCU to make sure that the | |
143 | * anon_vma isn't actually destroyed). | |
144 | * | |
145 | * As a result, we need to do proper anon_vma locking even | |
146 | * for the new allocation. At the same time, we do not want | |
147 | * to do any locking for the common case of already having | |
148 | * an anon_vma. | |
149 | * | |
150 | * This must be called with the mmap_sem held for reading. | |
151 | */ | |
1da177e4 LT |
152 | int anon_vma_prepare(struct vm_area_struct *vma) |
153 | { | |
154 | struct anon_vma *anon_vma = vma->anon_vma; | |
5beb4930 | 155 | struct anon_vma_chain *avc; |
1da177e4 LT |
156 | |
157 | might_sleep(); | |
158 | if (unlikely(!anon_vma)) { | |
159 | struct mm_struct *mm = vma->vm_mm; | |
d9d332e0 | 160 | struct anon_vma *allocated; |
1da177e4 | 161 | |
dd34739c | 162 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
5beb4930 RR |
163 | if (!avc) |
164 | goto out_enomem; | |
165 | ||
1da177e4 | 166 | anon_vma = find_mergeable_anon_vma(vma); |
d9d332e0 LT |
167 | allocated = NULL; |
168 | if (!anon_vma) { | |
1da177e4 LT |
169 | anon_vma = anon_vma_alloc(); |
170 | if (unlikely(!anon_vma)) | |
5beb4930 | 171 | goto out_enomem_free_avc; |
1da177e4 | 172 | allocated = anon_vma; |
1da177e4 LT |
173 | } |
174 | ||
cba48b98 | 175 | anon_vma_lock(anon_vma); |
1da177e4 LT |
176 | /* page_table_lock to protect against threads */ |
177 | spin_lock(&mm->page_table_lock); | |
178 | if (likely(!vma->anon_vma)) { | |
179 | vma->anon_vma = anon_vma; | |
5beb4930 RR |
180 | avc->anon_vma = anon_vma; |
181 | avc->vma = vma; | |
182 | list_add(&avc->same_vma, &vma->anon_vma_chain); | |
26ba0cb6 | 183 | list_add_tail(&avc->same_anon_vma, &anon_vma->head); |
1da177e4 | 184 | allocated = NULL; |
31f2b0eb | 185 | avc = NULL; |
1da177e4 LT |
186 | } |
187 | spin_unlock(&mm->page_table_lock); | |
cba48b98 | 188 | anon_vma_unlock(anon_vma); |
31f2b0eb ON |
189 | |
190 | if (unlikely(allocated)) | |
01d8b20d | 191 | put_anon_vma(allocated); |
31f2b0eb | 192 | if (unlikely(avc)) |
5beb4930 | 193 | anon_vma_chain_free(avc); |
1da177e4 LT |
194 | } |
195 | return 0; | |
5beb4930 RR |
196 | |
197 | out_enomem_free_avc: | |
198 | anon_vma_chain_free(avc); | |
199 | out_enomem: | |
200 | return -ENOMEM; | |
1da177e4 LT |
201 | } |
202 | ||
bb4aa396 LT |
203 | /* |
204 | * This is a useful helper function for locking the anon_vma root as | |
205 | * we traverse the vma->anon_vma_chain, looping over anon_vma's that | |
206 | * have the same vma. | |
207 | * | |
208 | * Such anon_vma's should have the same root, so you'd expect to see | |
209 | * just a single mutex_lock for the whole traversal. | |
210 | */ | |
211 | static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma) | |
212 | { | |
213 | struct anon_vma *new_root = anon_vma->root; | |
214 | if (new_root != root) { | |
215 | if (WARN_ON_ONCE(root)) | |
216 | mutex_unlock(&root->mutex); | |
217 | root = new_root; | |
218 | mutex_lock(&root->mutex); | |
219 | } | |
220 | return root; | |
221 | } | |
222 | ||
223 | static inline void unlock_anon_vma_root(struct anon_vma *root) | |
224 | { | |
225 | if (root) | |
226 | mutex_unlock(&root->mutex); | |
227 | } | |
228 | ||
5beb4930 RR |
229 | static void anon_vma_chain_link(struct vm_area_struct *vma, |
230 | struct anon_vma_chain *avc, | |
231 | struct anon_vma *anon_vma) | |
1da177e4 | 232 | { |
5beb4930 RR |
233 | avc->vma = vma; |
234 | avc->anon_vma = anon_vma; | |
235 | list_add(&avc->same_vma, &vma->anon_vma_chain); | |
236 | ||
05759d38 AA |
237 | /* |
238 | * It's critical to add new vmas to the tail of the anon_vma, | |
239 | * see comment in huge_memory.c:__split_huge_page(). | |
240 | */ | |
5beb4930 | 241 | list_add_tail(&avc->same_anon_vma, &anon_vma->head); |
1da177e4 LT |
242 | } |
243 | ||
5beb4930 RR |
244 | /* |
245 | * Attach the anon_vmas from src to dst. | |
246 | * Returns 0 on success, -ENOMEM on failure. | |
247 | */ | |
248 | int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) | |
1da177e4 | 249 | { |
5beb4930 | 250 | struct anon_vma_chain *avc, *pavc; |
bb4aa396 | 251 | struct anon_vma *root = NULL; |
5beb4930 | 252 | |
646d87b4 | 253 | list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
bb4aa396 LT |
254 | struct anon_vma *anon_vma; |
255 | ||
dd34739c LT |
256 | avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN); |
257 | if (unlikely(!avc)) { | |
258 | unlock_anon_vma_root(root); | |
259 | root = NULL; | |
260 | avc = anon_vma_chain_alloc(GFP_KERNEL); | |
261 | if (!avc) | |
262 | goto enomem_failure; | |
263 | } | |
bb4aa396 LT |
264 | anon_vma = pavc->anon_vma; |
265 | root = lock_anon_vma_root(root, anon_vma); | |
266 | anon_vma_chain_link(dst, avc, anon_vma); | |
5beb4930 | 267 | } |
bb4aa396 | 268 | unlock_anon_vma_root(root); |
5beb4930 | 269 | return 0; |
1da177e4 | 270 | |
5beb4930 RR |
271 | enomem_failure: |
272 | unlink_anon_vmas(dst); | |
273 | return -ENOMEM; | |
1da177e4 LT |
274 | } |
275 | ||
5beb4930 RR |
276 | /* |
277 | * Attach vma to its own anon_vma, as well as to the anon_vmas that | |
278 | * the corresponding VMA in the parent process is attached to. | |
279 | * Returns 0 on success, non-zero on failure. | |
280 | */ | |
281 | int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) | |
1da177e4 | 282 | { |
5beb4930 RR |
283 | struct anon_vma_chain *avc; |
284 | struct anon_vma *anon_vma; | |
1da177e4 | 285 | |
5beb4930 RR |
286 | /* Don't bother if the parent process has no anon_vma here. */ |
287 | if (!pvma->anon_vma) | |
288 | return 0; | |
289 | ||
290 | /* | |
291 | * First, attach the new VMA to the parent VMA's anon_vmas, | |
292 | * so rmap can find non-COWed pages in child processes. | |
293 | */ | |
294 | if (anon_vma_clone(vma, pvma)) | |
295 | return -ENOMEM; | |
296 | ||
297 | /* Then add our own anon_vma. */ | |
298 | anon_vma = anon_vma_alloc(); | |
299 | if (!anon_vma) | |
300 | goto out_error; | |
dd34739c | 301 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
5beb4930 RR |
302 | if (!avc) |
303 | goto out_error_free_anon_vma; | |
5c341ee1 RR |
304 | |
305 | /* | |
306 | * The root anon_vma's spinlock is the lock actually used when we | |
307 | * lock any of the anon_vmas in this anon_vma tree. | |
308 | */ | |
309 | anon_vma->root = pvma->anon_vma->root; | |
76545066 | 310 | /* |
01d8b20d PZ |
311 | * With refcounts, an anon_vma can stay around longer than the |
312 | * process it belongs to. The root anon_vma needs to be pinned until | |
313 | * this anon_vma is freed, because the lock lives in the root. | |
76545066 RR |
314 | */ |
315 | get_anon_vma(anon_vma->root); | |
5beb4930 RR |
316 | /* Mark this anon_vma as the one where our new (COWed) pages go. */ |
317 | vma->anon_vma = anon_vma; | |
bb4aa396 | 318 | anon_vma_lock(anon_vma); |
5c341ee1 | 319 | anon_vma_chain_link(vma, avc, anon_vma); |
bb4aa396 | 320 | anon_vma_unlock(anon_vma); |
5beb4930 RR |
321 | |
322 | return 0; | |
323 | ||
324 | out_error_free_anon_vma: | |
01d8b20d | 325 | put_anon_vma(anon_vma); |
5beb4930 | 326 | out_error: |
4946d54c | 327 | unlink_anon_vmas(vma); |
5beb4930 | 328 | return -ENOMEM; |
1da177e4 LT |
329 | } |
330 | ||
5beb4930 RR |
331 | void unlink_anon_vmas(struct vm_area_struct *vma) |
332 | { | |
333 | struct anon_vma_chain *avc, *next; | |
eee2acba | 334 | struct anon_vma *root = NULL; |
5beb4930 | 335 | |
5c341ee1 RR |
336 | /* |
337 | * Unlink each anon_vma chained to the VMA. This list is ordered | |
338 | * from newest to oldest, ensuring the root anon_vma gets freed last. | |
339 | */ | |
5beb4930 | 340 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
eee2acba PZ |
341 | struct anon_vma *anon_vma = avc->anon_vma; |
342 | ||
343 | root = lock_anon_vma_root(root, anon_vma); | |
344 | list_del(&avc->same_anon_vma); | |
345 | ||
346 | /* | |
347 | * Leave empty anon_vmas on the list - we'll need | |
348 | * to free them outside the lock. | |
349 | */ | |
350 | if (list_empty(&anon_vma->head)) | |
351 | continue; | |
352 | ||
353 | list_del(&avc->same_vma); | |
354 | anon_vma_chain_free(avc); | |
355 | } | |
356 | unlock_anon_vma_root(root); | |
357 | ||
358 | /* | |
359 | * Iterate the list once more, it now only contains empty and unlinked | |
360 | * anon_vmas, destroy them. Could not do before due to __put_anon_vma() | |
361 | * needing to acquire the anon_vma->root->mutex. | |
362 | */ | |
363 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { | |
364 | struct anon_vma *anon_vma = avc->anon_vma; | |
365 | ||
366 | put_anon_vma(anon_vma); | |
367 | ||
5beb4930 RR |
368 | list_del(&avc->same_vma); |
369 | anon_vma_chain_free(avc); | |
370 | } | |
371 | } | |
372 | ||
51cc5068 | 373 | static void anon_vma_ctor(void *data) |
1da177e4 | 374 | { |
a35afb83 | 375 | struct anon_vma *anon_vma = data; |
1da177e4 | 376 | |
2b575eb6 | 377 | mutex_init(&anon_vma->mutex); |
83813267 | 378 | atomic_set(&anon_vma->refcount, 0); |
a35afb83 | 379 | INIT_LIST_HEAD(&anon_vma->head); |
1da177e4 LT |
380 | } |
381 | ||
382 | void __init anon_vma_init(void) | |
383 | { | |
384 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), | |
20c2df83 | 385 | 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor); |
5beb4930 | 386 | anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC); |
1da177e4 LT |
387 | } |
388 | ||
389 | /* | |
6111e4ca PZ |
390 | * Getting a lock on a stable anon_vma from a page off the LRU is tricky! |
391 | * | |
392 | * Since there is no serialization what so ever against page_remove_rmap() | |
393 | * the best this function can do is return a locked anon_vma that might | |
394 | * have been relevant to this page. | |
395 | * | |
396 | * The page might have been remapped to a different anon_vma or the anon_vma | |
397 | * returned may already be freed (and even reused). | |
398 | * | |
bc658c96 PZ |
399 | * In case it was remapped to a different anon_vma, the new anon_vma will be a |
400 | * child of the old anon_vma, and the anon_vma lifetime rules will therefore | |
401 | * ensure that any anon_vma obtained from the page will still be valid for as | |
402 | * long as we observe page_mapped() [ hence all those page_mapped() tests ]. | |
403 | * | |
6111e4ca PZ |
404 | * All users of this function must be very careful when walking the anon_vma |
405 | * chain and verify that the page in question is indeed mapped in it | |
406 | * [ something equivalent to page_mapped_in_vma() ]. | |
407 | * | |
408 | * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap() | |
409 | * that the anon_vma pointer from page->mapping is valid if there is a | |
410 | * mapcount, we can dereference the anon_vma after observing those. | |
1da177e4 | 411 | */ |
746b18d4 | 412 | struct anon_vma *page_get_anon_vma(struct page *page) |
1da177e4 | 413 | { |
746b18d4 | 414 | struct anon_vma *anon_vma = NULL; |
1da177e4 LT |
415 | unsigned long anon_mapping; |
416 | ||
417 | rcu_read_lock(); | |
80e14822 | 418 | anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping); |
3ca7b3c5 | 419 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
1da177e4 LT |
420 | goto out; |
421 | if (!page_mapped(page)) | |
422 | goto out; | |
423 | ||
424 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); | |
746b18d4 PZ |
425 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
426 | anon_vma = NULL; | |
427 | goto out; | |
428 | } | |
f1819427 HD |
429 | |
430 | /* | |
431 | * If this page is still mapped, then its anon_vma cannot have been | |
746b18d4 PZ |
432 | * freed. But if it has been unmapped, we have no security against the |
433 | * anon_vma structure being freed and reused (for another anon_vma: | |
434 | * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero() | |
435 | * above cannot corrupt). | |
f1819427 | 436 | */ |
746b18d4 PZ |
437 | if (!page_mapped(page)) { |
438 | put_anon_vma(anon_vma); | |
439 | anon_vma = NULL; | |
440 | } | |
1da177e4 LT |
441 | out: |
442 | rcu_read_unlock(); | |
746b18d4 PZ |
443 | |
444 | return anon_vma; | |
445 | } | |
446 | ||
88c22088 PZ |
447 | /* |
448 | * Similar to page_get_anon_vma() except it locks the anon_vma. | |
449 | * | |
450 | * Its a little more complex as it tries to keep the fast path to a single | |
451 | * atomic op -- the trylock. If we fail the trylock, we fall back to getting a | |
452 | * reference like with page_get_anon_vma() and then block on the mutex. | |
453 | */ | |
746b18d4 PZ |
454 | struct anon_vma *page_lock_anon_vma(struct page *page) |
455 | { | |
88c22088 | 456 | struct anon_vma *anon_vma = NULL; |
eee0f252 | 457 | struct anon_vma *root_anon_vma; |
88c22088 | 458 | unsigned long anon_mapping; |
746b18d4 | 459 | |
88c22088 PZ |
460 | rcu_read_lock(); |
461 | anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping); | |
462 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) | |
463 | goto out; | |
464 | if (!page_mapped(page)) | |
465 | goto out; | |
466 | ||
467 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); | |
eee0f252 HD |
468 | root_anon_vma = ACCESS_ONCE(anon_vma->root); |
469 | if (mutex_trylock(&root_anon_vma->mutex)) { | |
88c22088 | 470 | /* |
eee0f252 HD |
471 | * If the page is still mapped, then this anon_vma is still |
472 | * its anon_vma, and holding the mutex ensures that it will | |
bc658c96 | 473 | * not go away, see anon_vma_free(). |
88c22088 | 474 | */ |
eee0f252 HD |
475 | if (!page_mapped(page)) { |
476 | mutex_unlock(&root_anon_vma->mutex); | |
88c22088 PZ |
477 | anon_vma = NULL; |
478 | } | |
479 | goto out; | |
480 | } | |
746b18d4 | 481 | |
88c22088 PZ |
482 | /* trylock failed, we got to sleep */ |
483 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { | |
484 | anon_vma = NULL; | |
485 | goto out; | |
486 | } | |
487 | ||
488 | if (!page_mapped(page)) { | |
489 | put_anon_vma(anon_vma); | |
490 | anon_vma = NULL; | |
491 | goto out; | |
492 | } | |
493 | ||
494 | /* we pinned the anon_vma, its safe to sleep */ | |
495 | rcu_read_unlock(); | |
496 | anon_vma_lock(anon_vma); | |
497 | ||
498 | if (atomic_dec_and_test(&anon_vma->refcount)) { | |
499 | /* | |
500 | * Oops, we held the last refcount, release the lock | |
501 | * and bail -- can't simply use put_anon_vma() because | |
502 | * we'll deadlock on the anon_vma_lock() recursion. | |
503 | */ | |
504 | anon_vma_unlock(anon_vma); | |
505 | __put_anon_vma(anon_vma); | |
506 | anon_vma = NULL; | |
507 | } | |
508 | ||
509 | return anon_vma; | |
510 | ||
511 | out: | |
512 | rcu_read_unlock(); | |
746b18d4 | 513 | return anon_vma; |
34bbd704 ON |
514 | } |
515 | ||
10be22df | 516 | void page_unlock_anon_vma(struct anon_vma *anon_vma) |
34bbd704 | 517 | { |
cba48b98 | 518 | anon_vma_unlock(anon_vma); |
1da177e4 LT |
519 | } |
520 | ||
521 | /* | |
3ad33b24 LS |
522 | * At what user virtual address is page expected in @vma? |
523 | * Returns virtual address or -EFAULT if page's index/offset is not | |
524 | * within the range mapped the @vma. | |
1da177e4 | 525 | */ |
71e3aac0 | 526 | inline unsigned long |
1da177e4 LT |
527 | vma_address(struct page *page, struct vm_area_struct *vma) |
528 | { | |
529 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
530 | unsigned long address; | |
531 | ||
0fe6e20b NH |
532 | if (unlikely(is_vm_hugetlb_page(vma))) |
533 | pgoff = page->index << huge_page_order(page_hstate(page)); | |
1da177e4 LT |
534 | address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
535 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { | |
3ad33b24 | 536 | /* page should be within @vma mapping range */ |
1da177e4 LT |
537 | return -EFAULT; |
538 | } | |
539 | return address; | |
540 | } | |
541 | ||
542 | /* | |
bf89c8c8 | 543 | * At what user virtual address is page expected in vma? |
ab941e0f | 544 | * Caller should check the page is actually part of the vma. |
1da177e4 LT |
545 | */ |
546 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) | |
547 | { | |
21d0d443 | 548 | if (PageAnon(page)) { |
4829b906 HD |
549 | struct anon_vma *page__anon_vma = page_anon_vma(page); |
550 | /* | |
551 | * Note: swapoff's unuse_vma() is more efficient with this | |
552 | * check, and needs it to match anon_vma when KSM is active. | |
553 | */ | |
554 | if (!vma->anon_vma || !page__anon_vma || | |
555 | vma->anon_vma->root != page__anon_vma->root) | |
21d0d443 AA |
556 | return -EFAULT; |
557 | } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { | |
ee498ed7 HD |
558 | if (!vma->vm_file || |
559 | vma->vm_file->f_mapping != page->mapping) | |
1da177e4 LT |
560 | return -EFAULT; |
561 | } else | |
562 | return -EFAULT; | |
563 | return vma_address(page, vma); | |
564 | } | |
565 | ||
81b4082d ND |
566 | /* |
567 | * Check that @page is mapped at @address into @mm. | |
568 | * | |
479db0bf NP |
569 | * If @sync is false, page_check_address may perform a racy check to avoid |
570 | * the page table lock when the pte is not present (helpful when reclaiming | |
571 | * highly shared pages). | |
572 | * | |
b8072f09 | 573 | * On success returns with pte mapped and locked. |
81b4082d | 574 | */ |
e9a81a82 | 575 | pte_t *__page_check_address(struct page *page, struct mm_struct *mm, |
479db0bf | 576 | unsigned long address, spinlock_t **ptlp, int sync) |
81b4082d ND |
577 | { |
578 | pgd_t *pgd; | |
579 | pud_t *pud; | |
580 | pmd_t *pmd; | |
581 | pte_t *pte; | |
c0718806 | 582 | spinlock_t *ptl; |
81b4082d | 583 | |
0fe6e20b NH |
584 | if (unlikely(PageHuge(page))) { |
585 | pte = huge_pte_offset(mm, address); | |
586 | ptl = &mm->page_table_lock; | |
587 | goto check; | |
588 | } | |
589 | ||
81b4082d | 590 | pgd = pgd_offset(mm, address); |
c0718806 HD |
591 | if (!pgd_present(*pgd)) |
592 | return NULL; | |
593 | ||
594 | pud = pud_offset(pgd, address); | |
595 | if (!pud_present(*pud)) | |
596 | return NULL; | |
597 | ||
598 | pmd = pmd_offset(pud, address); | |
599 | if (!pmd_present(*pmd)) | |
600 | return NULL; | |
71e3aac0 AA |
601 | if (pmd_trans_huge(*pmd)) |
602 | return NULL; | |
c0718806 HD |
603 | |
604 | pte = pte_offset_map(pmd, address); | |
605 | /* Make a quick check before getting the lock */ | |
479db0bf | 606 | if (!sync && !pte_present(*pte)) { |
c0718806 HD |
607 | pte_unmap(pte); |
608 | return NULL; | |
609 | } | |
610 | ||
4c21e2f2 | 611 | ptl = pte_lockptr(mm, pmd); |
0fe6e20b | 612 | check: |
c0718806 HD |
613 | spin_lock(ptl); |
614 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { | |
615 | *ptlp = ptl; | |
616 | return pte; | |
81b4082d | 617 | } |
c0718806 HD |
618 | pte_unmap_unlock(pte, ptl); |
619 | return NULL; | |
81b4082d ND |
620 | } |
621 | ||
b291f000 NP |
622 | /** |
623 | * page_mapped_in_vma - check whether a page is really mapped in a VMA | |
624 | * @page: the page to test | |
625 | * @vma: the VMA to test | |
626 | * | |
627 | * Returns 1 if the page is mapped into the page tables of the VMA, 0 | |
628 | * if the page is not mapped into the page tables of this VMA. Only | |
629 | * valid for normal file or anonymous VMAs. | |
630 | */ | |
6a46079c | 631 | int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) |
b291f000 NP |
632 | { |
633 | unsigned long address; | |
634 | pte_t *pte; | |
635 | spinlock_t *ptl; | |
636 | ||
637 | address = vma_address(page, vma); | |
638 | if (address == -EFAULT) /* out of vma range */ | |
639 | return 0; | |
640 | pte = page_check_address(page, vma->vm_mm, address, &ptl, 1); | |
641 | if (!pte) /* the page is not in this mm */ | |
642 | return 0; | |
643 | pte_unmap_unlock(pte, ptl); | |
644 | ||
645 | return 1; | |
646 | } | |
647 | ||
1da177e4 LT |
648 | /* |
649 | * Subfunctions of page_referenced: page_referenced_one called | |
650 | * repeatedly from either page_referenced_anon or page_referenced_file. | |
651 | */ | |
5ad64688 HD |
652 | int page_referenced_one(struct page *page, struct vm_area_struct *vma, |
653 | unsigned long address, unsigned int *mapcount, | |
654 | unsigned long *vm_flags) | |
1da177e4 LT |
655 | { |
656 | struct mm_struct *mm = vma->vm_mm; | |
1da177e4 LT |
657 | int referenced = 0; |
658 | ||
71e3aac0 AA |
659 | if (unlikely(PageTransHuge(page))) { |
660 | pmd_t *pmd; | |
661 | ||
662 | spin_lock(&mm->page_table_lock); | |
2da28bfd AA |
663 | /* |
664 | * rmap might return false positives; we must filter | |
665 | * these out using page_check_address_pmd(). | |
666 | */ | |
71e3aac0 AA |
667 | pmd = page_check_address_pmd(page, mm, address, |
668 | PAGE_CHECK_ADDRESS_PMD_FLAG); | |
2da28bfd AA |
669 | if (!pmd) { |
670 | spin_unlock(&mm->page_table_lock); | |
671 | goto out; | |
672 | } | |
673 | ||
674 | if (vma->vm_flags & VM_LOCKED) { | |
675 | spin_unlock(&mm->page_table_lock); | |
676 | *mapcount = 0; /* break early from loop */ | |
677 | *vm_flags |= VM_LOCKED; | |
678 | goto out; | |
679 | } | |
680 | ||
681 | /* go ahead even if the pmd is pmd_trans_splitting() */ | |
682 | if (pmdp_clear_flush_young_notify(vma, address, pmd)) | |
71e3aac0 AA |
683 | referenced++; |
684 | spin_unlock(&mm->page_table_lock); | |
685 | } else { | |
686 | pte_t *pte; | |
687 | spinlock_t *ptl; | |
688 | ||
2da28bfd AA |
689 | /* |
690 | * rmap might return false positives; we must filter | |
691 | * these out using page_check_address(). | |
692 | */ | |
71e3aac0 AA |
693 | pte = page_check_address(page, mm, address, &ptl, 0); |
694 | if (!pte) | |
695 | goto out; | |
696 | ||
2da28bfd AA |
697 | if (vma->vm_flags & VM_LOCKED) { |
698 | pte_unmap_unlock(pte, ptl); | |
699 | *mapcount = 0; /* break early from loop */ | |
700 | *vm_flags |= VM_LOCKED; | |
701 | goto out; | |
702 | } | |
703 | ||
71e3aac0 AA |
704 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
705 | /* | |
706 | * Don't treat a reference through a sequentially read | |
707 | * mapping as such. If the page has been used in | |
708 | * another mapping, we will catch it; if this other | |
709 | * mapping is already gone, the unmap path will have | |
710 | * set PG_referenced or activated the page. | |
711 | */ | |
712 | if (likely(!VM_SequentialReadHint(vma))) | |
713 | referenced++; | |
714 | } | |
715 | pte_unmap_unlock(pte, ptl); | |
716 | } | |
717 | ||
2da28bfd AA |
718 | /* Pretend the page is referenced if the task has the |
719 | swap token and is in the middle of a page fault. */ | |
720 | if (mm != current->mm && has_swap_token(mm) && | |
721 | rwsem_is_locked(&mm->mmap_sem)) | |
722 | referenced++; | |
723 | ||
c0718806 | 724 | (*mapcount)--; |
273f047e | 725 | |
6fe6b7e3 WF |
726 | if (referenced) |
727 | *vm_flags |= vma->vm_flags; | |
273f047e | 728 | out: |
1da177e4 LT |
729 | return referenced; |
730 | } | |
731 | ||
bed7161a | 732 | static int page_referenced_anon(struct page *page, |
6fe6b7e3 WF |
733 | struct mem_cgroup *mem_cont, |
734 | unsigned long *vm_flags) | |
1da177e4 LT |
735 | { |
736 | unsigned int mapcount; | |
737 | struct anon_vma *anon_vma; | |
5beb4930 | 738 | struct anon_vma_chain *avc; |
1da177e4 LT |
739 | int referenced = 0; |
740 | ||
741 | anon_vma = page_lock_anon_vma(page); | |
742 | if (!anon_vma) | |
743 | return referenced; | |
744 | ||
745 | mapcount = page_mapcount(page); | |
5beb4930 RR |
746 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
747 | struct vm_area_struct *vma = avc->vma; | |
1cb1729b HD |
748 | unsigned long address = vma_address(page, vma); |
749 | if (address == -EFAULT) | |
750 | continue; | |
bed7161a BS |
751 | /* |
752 | * If we are reclaiming on behalf of a cgroup, skip | |
753 | * counting on behalf of references from different | |
754 | * cgroups | |
755 | */ | |
bd845e38 | 756 | if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) |
bed7161a | 757 | continue; |
1cb1729b | 758 | referenced += page_referenced_one(page, vma, address, |
6fe6b7e3 | 759 | &mapcount, vm_flags); |
1da177e4 LT |
760 | if (!mapcount) |
761 | break; | |
762 | } | |
34bbd704 ON |
763 | |
764 | page_unlock_anon_vma(anon_vma); | |
1da177e4 LT |
765 | return referenced; |
766 | } | |
767 | ||
768 | /** | |
769 | * page_referenced_file - referenced check for object-based rmap | |
770 | * @page: the page we're checking references on. | |
43d8eac4 | 771 | * @mem_cont: target memory controller |
6fe6b7e3 | 772 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
1da177e4 LT |
773 | * |
774 | * For an object-based mapped page, find all the places it is mapped and | |
775 | * check/clear the referenced flag. This is done by following the page->mapping | |
776 | * pointer, then walking the chain of vmas it holds. It returns the number | |
777 | * of references it found. | |
778 | * | |
779 | * This function is only called from page_referenced for object-based pages. | |
780 | */ | |
bed7161a | 781 | static int page_referenced_file(struct page *page, |
6fe6b7e3 WF |
782 | struct mem_cgroup *mem_cont, |
783 | unsigned long *vm_flags) | |
1da177e4 LT |
784 | { |
785 | unsigned int mapcount; | |
786 | struct address_space *mapping = page->mapping; | |
787 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
788 | struct vm_area_struct *vma; | |
789 | struct prio_tree_iter iter; | |
790 | int referenced = 0; | |
791 | ||
792 | /* | |
793 | * The caller's checks on page->mapping and !PageAnon have made | |
794 | * sure that this is a file page: the check for page->mapping | |
795 | * excludes the case just before it gets set on an anon page. | |
796 | */ | |
797 | BUG_ON(PageAnon(page)); | |
798 | ||
799 | /* | |
800 | * The page lock not only makes sure that page->mapping cannot | |
801 | * suddenly be NULLified by truncation, it makes sure that the | |
802 | * structure at mapping cannot be freed and reused yet, | |
3d48ae45 | 803 | * so we can safely take mapping->i_mmap_mutex. |
1da177e4 LT |
804 | */ |
805 | BUG_ON(!PageLocked(page)); | |
806 | ||
3d48ae45 | 807 | mutex_lock(&mapping->i_mmap_mutex); |
1da177e4 LT |
808 | |
809 | /* | |
3d48ae45 | 810 | * i_mmap_mutex does not stabilize mapcount at all, but mapcount |
1da177e4 LT |
811 | * is more likely to be accurate if we note it after spinning. |
812 | */ | |
813 | mapcount = page_mapcount(page); | |
814 | ||
815 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { | |
1cb1729b HD |
816 | unsigned long address = vma_address(page, vma); |
817 | if (address == -EFAULT) | |
818 | continue; | |
bed7161a BS |
819 | /* |
820 | * If we are reclaiming on behalf of a cgroup, skip | |
821 | * counting on behalf of references from different | |
822 | * cgroups | |
823 | */ | |
bd845e38 | 824 | if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) |
bed7161a | 825 | continue; |
1cb1729b | 826 | referenced += page_referenced_one(page, vma, address, |
6fe6b7e3 | 827 | &mapcount, vm_flags); |
1da177e4 LT |
828 | if (!mapcount) |
829 | break; | |
830 | } | |
831 | ||
3d48ae45 | 832 | mutex_unlock(&mapping->i_mmap_mutex); |
1da177e4 LT |
833 | return referenced; |
834 | } | |
835 | ||
836 | /** | |
837 | * page_referenced - test if the page was referenced | |
838 | * @page: the page to test | |
839 | * @is_locked: caller holds lock on the page | |
43d8eac4 | 840 | * @mem_cont: target memory controller |
6fe6b7e3 | 841 | * @vm_flags: collect encountered vma->vm_flags who actually referenced the page |
1da177e4 LT |
842 | * |
843 | * Quick test_and_clear_referenced for all mappings to a page, | |
844 | * returns the number of ptes which referenced the page. | |
845 | */ | |
6fe6b7e3 WF |
846 | int page_referenced(struct page *page, |
847 | int is_locked, | |
848 | struct mem_cgroup *mem_cont, | |
849 | unsigned long *vm_flags) | |
1da177e4 LT |
850 | { |
851 | int referenced = 0; | |
5ad64688 | 852 | int we_locked = 0; |
1da177e4 | 853 | |
6fe6b7e3 | 854 | *vm_flags = 0; |
3ca7b3c5 | 855 | if (page_mapped(page) && page_rmapping(page)) { |
5ad64688 HD |
856 | if (!is_locked && (!PageAnon(page) || PageKsm(page))) { |
857 | we_locked = trylock_page(page); | |
858 | if (!we_locked) { | |
859 | referenced++; | |
860 | goto out; | |
861 | } | |
862 | } | |
863 | if (unlikely(PageKsm(page))) | |
864 | referenced += page_referenced_ksm(page, mem_cont, | |
865 | vm_flags); | |
866 | else if (PageAnon(page)) | |
6fe6b7e3 WF |
867 | referenced += page_referenced_anon(page, mem_cont, |
868 | vm_flags); | |
5ad64688 | 869 | else if (page->mapping) |
6fe6b7e3 WF |
870 | referenced += page_referenced_file(page, mem_cont, |
871 | vm_flags); | |
5ad64688 | 872 | if (we_locked) |
1da177e4 | 873 | unlock_page(page); |
1da177e4 | 874 | } |
5ad64688 | 875 | out: |
2d42552d | 876 | if (page_test_and_clear_young(page_to_pfn(page))) |
5b7baf05 CB |
877 | referenced++; |
878 | ||
1da177e4 LT |
879 | return referenced; |
880 | } | |
881 | ||
1cb1729b HD |
882 | static int page_mkclean_one(struct page *page, struct vm_area_struct *vma, |
883 | unsigned long address) | |
d08b3851 PZ |
884 | { |
885 | struct mm_struct *mm = vma->vm_mm; | |
c2fda5fe | 886 | pte_t *pte; |
d08b3851 PZ |
887 | spinlock_t *ptl; |
888 | int ret = 0; | |
889 | ||
479db0bf | 890 | pte = page_check_address(page, mm, address, &ptl, 1); |
d08b3851 PZ |
891 | if (!pte) |
892 | goto out; | |
893 | ||
c2fda5fe PZ |
894 | if (pte_dirty(*pte) || pte_write(*pte)) { |
895 | pte_t entry; | |
d08b3851 | 896 | |
c2fda5fe | 897 | flush_cache_page(vma, address, pte_pfn(*pte)); |
cddb8a5c | 898 | entry = ptep_clear_flush_notify(vma, address, pte); |
c2fda5fe PZ |
899 | entry = pte_wrprotect(entry); |
900 | entry = pte_mkclean(entry); | |
d6e88e67 | 901 | set_pte_at(mm, address, pte, entry); |
c2fda5fe PZ |
902 | ret = 1; |
903 | } | |
d08b3851 | 904 | |
d08b3851 PZ |
905 | pte_unmap_unlock(pte, ptl); |
906 | out: | |
907 | return ret; | |
908 | } | |
909 | ||
910 | static int page_mkclean_file(struct address_space *mapping, struct page *page) | |
911 | { | |
912 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
913 | struct vm_area_struct *vma; | |
914 | struct prio_tree_iter iter; | |
915 | int ret = 0; | |
916 | ||
917 | BUG_ON(PageAnon(page)); | |
918 | ||
3d48ae45 | 919 | mutex_lock(&mapping->i_mmap_mutex); |
d08b3851 | 920 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1cb1729b HD |
921 | if (vma->vm_flags & VM_SHARED) { |
922 | unsigned long address = vma_address(page, vma); | |
923 | if (address == -EFAULT) | |
924 | continue; | |
925 | ret += page_mkclean_one(page, vma, address); | |
926 | } | |
d08b3851 | 927 | } |
3d48ae45 | 928 | mutex_unlock(&mapping->i_mmap_mutex); |
d08b3851 PZ |
929 | return ret; |
930 | } | |
931 | ||
932 | int page_mkclean(struct page *page) | |
933 | { | |
934 | int ret = 0; | |
935 | ||
936 | BUG_ON(!PageLocked(page)); | |
937 | ||
938 | if (page_mapped(page)) { | |
939 | struct address_space *mapping = page_mapping(page); | |
ce7e9fae | 940 | if (mapping) { |
d08b3851 | 941 | ret = page_mkclean_file(mapping, page); |
2d42552d | 942 | if (page_test_and_clear_dirty(page_to_pfn(page), 1)) |
ce7e9fae | 943 | ret = 1; |
6c210482 | 944 | } |
d08b3851 PZ |
945 | } |
946 | ||
947 | return ret; | |
948 | } | |
60b59bea | 949 | EXPORT_SYMBOL_GPL(page_mkclean); |
d08b3851 | 950 | |
c44b6743 RR |
951 | /** |
952 | * page_move_anon_rmap - move a page to our anon_vma | |
953 | * @page: the page to move to our anon_vma | |
954 | * @vma: the vma the page belongs to | |
955 | * @address: the user virtual address mapped | |
956 | * | |
957 | * When a page belongs exclusively to one process after a COW event, | |
958 | * that page can be moved into the anon_vma that belongs to just that | |
959 | * process, so the rmap code will not search the parent or sibling | |
960 | * processes. | |
961 | */ | |
962 | void page_move_anon_rmap(struct page *page, | |
963 | struct vm_area_struct *vma, unsigned long address) | |
964 | { | |
965 | struct anon_vma *anon_vma = vma->anon_vma; | |
966 | ||
967 | VM_BUG_ON(!PageLocked(page)); | |
968 | VM_BUG_ON(!anon_vma); | |
969 | VM_BUG_ON(page->index != linear_page_index(vma, address)); | |
970 | ||
971 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; | |
972 | page->mapping = (struct address_space *) anon_vma; | |
973 | } | |
974 | ||
9617d95e | 975 | /** |
4e1c1975 AK |
976 | * __page_set_anon_rmap - set up new anonymous rmap |
977 | * @page: Page to add to rmap | |
978 | * @vma: VM area to add page to. | |
979 | * @address: User virtual address of the mapping | |
e8a03feb | 980 | * @exclusive: the page is exclusively owned by the current process |
9617d95e NP |
981 | */ |
982 | static void __page_set_anon_rmap(struct page *page, | |
e8a03feb | 983 | struct vm_area_struct *vma, unsigned long address, int exclusive) |
9617d95e | 984 | { |
e8a03feb | 985 | struct anon_vma *anon_vma = vma->anon_vma; |
ea90002b | 986 | |
e8a03feb | 987 | BUG_ON(!anon_vma); |
ea90002b | 988 | |
4e1c1975 AK |
989 | if (PageAnon(page)) |
990 | return; | |
991 | ||
ea90002b | 992 | /* |
e8a03feb RR |
993 | * If the page isn't exclusively mapped into this vma, |
994 | * we must use the _oldest_ possible anon_vma for the | |
995 | * page mapping! | |
ea90002b | 996 | */ |
4e1c1975 | 997 | if (!exclusive) |
288468c3 | 998 | anon_vma = anon_vma->root; |
9617d95e | 999 | |
9617d95e NP |
1000 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1001 | page->mapping = (struct address_space *) anon_vma; | |
9617d95e | 1002 | page->index = linear_page_index(vma, address); |
9617d95e NP |
1003 | } |
1004 | ||
c97a9e10 | 1005 | /** |
43d8eac4 | 1006 | * __page_check_anon_rmap - sanity check anonymous rmap addition |
c97a9e10 NP |
1007 | * @page: the page to add the mapping to |
1008 | * @vma: the vm area in which the mapping is added | |
1009 | * @address: the user virtual address mapped | |
1010 | */ | |
1011 | static void __page_check_anon_rmap(struct page *page, | |
1012 | struct vm_area_struct *vma, unsigned long address) | |
1013 | { | |
1014 | #ifdef CONFIG_DEBUG_VM | |
1015 | /* | |
1016 | * The page's anon-rmap details (mapping and index) are guaranteed to | |
1017 | * be set up correctly at this point. | |
1018 | * | |
1019 | * We have exclusion against page_add_anon_rmap because the caller | |
1020 | * always holds the page locked, except if called from page_dup_rmap, | |
1021 | * in which case the page is already known to be setup. | |
1022 | * | |
1023 | * We have exclusion against page_add_new_anon_rmap because those pages | |
1024 | * are initially only visible via the pagetables, and the pte is locked | |
1025 | * over the call to page_add_new_anon_rmap. | |
1026 | */ | |
44ab57a0 | 1027 | BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root); |
c97a9e10 NP |
1028 | BUG_ON(page->index != linear_page_index(vma, address)); |
1029 | #endif | |
1030 | } | |
1031 | ||
1da177e4 LT |
1032 | /** |
1033 | * page_add_anon_rmap - add pte mapping to an anonymous page | |
1034 | * @page: the page to add the mapping to | |
1035 | * @vma: the vm area in which the mapping is added | |
1036 | * @address: the user virtual address mapped | |
1037 | * | |
5ad64688 | 1038 | * The caller needs to hold the pte lock, and the page must be locked in |
80e14822 HD |
1039 | * the anon_vma case: to serialize mapping,index checking after setting, |
1040 | * and to ensure that PageAnon is not being upgraded racily to PageKsm | |
1041 | * (but PageKsm is never downgraded to PageAnon). | |
1da177e4 LT |
1042 | */ |
1043 | void page_add_anon_rmap(struct page *page, | |
1044 | struct vm_area_struct *vma, unsigned long address) | |
ad8c2ee8 RR |
1045 | { |
1046 | do_page_add_anon_rmap(page, vma, address, 0); | |
1047 | } | |
1048 | ||
1049 | /* | |
1050 | * Special version of the above for do_swap_page, which often runs | |
1051 | * into pages that are exclusively owned by the current process. | |
1052 | * Everybody else should continue to use page_add_anon_rmap above. | |
1053 | */ | |
1054 | void do_page_add_anon_rmap(struct page *page, | |
1055 | struct vm_area_struct *vma, unsigned long address, int exclusive) | |
1da177e4 | 1056 | { |
5ad64688 | 1057 | int first = atomic_inc_and_test(&page->_mapcount); |
79134171 AA |
1058 | if (first) { |
1059 | if (!PageTransHuge(page)) | |
1060 | __inc_zone_page_state(page, NR_ANON_PAGES); | |
1061 | else | |
1062 | __inc_zone_page_state(page, | |
1063 | NR_ANON_TRANSPARENT_HUGEPAGES); | |
1064 | } | |
5ad64688 HD |
1065 | if (unlikely(PageKsm(page))) |
1066 | return; | |
1067 | ||
c97a9e10 | 1068 | VM_BUG_ON(!PageLocked(page)); |
5dbe0af4 | 1069 | /* address might be in next vma when migration races vma_adjust */ |
5ad64688 | 1070 | if (first) |
ad8c2ee8 | 1071 | __page_set_anon_rmap(page, vma, address, exclusive); |
69029cd5 | 1072 | else |
c97a9e10 | 1073 | __page_check_anon_rmap(page, vma, address); |
1da177e4 LT |
1074 | } |
1075 | ||
43d8eac4 | 1076 | /** |
9617d95e NP |
1077 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page |
1078 | * @page: the page to add the mapping to | |
1079 | * @vma: the vm area in which the mapping is added | |
1080 | * @address: the user virtual address mapped | |
1081 | * | |
1082 | * Same as page_add_anon_rmap but must only be called on *new* pages. | |
1083 | * This means the inc-and-test can be bypassed. | |
c97a9e10 | 1084 | * Page does not have to be locked. |
9617d95e NP |
1085 | */ |
1086 | void page_add_new_anon_rmap(struct page *page, | |
1087 | struct vm_area_struct *vma, unsigned long address) | |
1088 | { | |
b5934c53 | 1089 | VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
cbf84b7a HD |
1090 | SetPageSwapBacked(page); |
1091 | atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */ | |
79134171 AA |
1092 | if (!PageTransHuge(page)) |
1093 | __inc_zone_page_state(page, NR_ANON_PAGES); | |
1094 | else | |
1095 | __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); | |
e8a03feb | 1096 | __page_set_anon_rmap(page, vma, address, 1); |
b5934c53 | 1097 | if (page_evictable(page, vma)) |
cbf84b7a | 1098 | lru_cache_add_lru(page, LRU_ACTIVE_ANON); |
b5934c53 HD |
1099 | else |
1100 | add_page_to_unevictable_list(page); | |
9617d95e NP |
1101 | } |
1102 | ||
1da177e4 LT |
1103 | /** |
1104 | * page_add_file_rmap - add pte mapping to a file page | |
1105 | * @page: the page to add the mapping to | |
1106 | * | |
b8072f09 | 1107 | * The caller needs to hold the pte lock. |
1da177e4 LT |
1108 | */ |
1109 | void page_add_file_rmap(struct page *page) | |
1110 | { | |
d69b042f | 1111 | if (atomic_inc_and_test(&page->_mapcount)) { |
65ba55f5 | 1112 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
2a7106f2 | 1113 | mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED); |
d69b042f | 1114 | } |
1da177e4 LT |
1115 | } |
1116 | ||
1117 | /** | |
1118 | * page_remove_rmap - take down pte mapping from a page | |
1119 | * @page: page to remove mapping from | |
1120 | * | |
b8072f09 | 1121 | * The caller needs to hold the pte lock. |
1da177e4 | 1122 | */ |
edc315fd | 1123 | void page_remove_rmap(struct page *page) |
1da177e4 | 1124 | { |
b904dcfe KM |
1125 | /* page still mapped by someone else? */ |
1126 | if (!atomic_add_negative(-1, &page->_mapcount)) | |
1127 | return; | |
1128 | ||
1129 | /* | |
1130 | * Now that the last pte has gone, s390 must transfer dirty | |
1131 | * flag from storage key to struct page. We can usually skip | |
1132 | * this if the page is anon, so about to be freed; but perhaps | |
1133 | * not if it's in swapcache - there might be another pte slot | |
1134 | * containing the swap entry, but page not yet written to swap. | |
1135 | */ | |
2d42552d MS |
1136 | if ((!PageAnon(page) || PageSwapCache(page)) && |
1137 | page_test_and_clear_dirty(page_to_pfn(page), 1)) | |
b904dcfe | 1138 | set_page_dirty(page); |
0fe6e20b NH |
1139 | /* |
1140 | * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED | |
1141 | * and not charged by memcg for now. | |
1142 | */ | |
1143 | if (unlikely(PageHuge(page))) | |
1144 | return; | |
b904dcfe KM |
1145 | if (PageAnon(page)) { |
1146 | mem_cgroup_uncharge_page(page); | |
79134171 AA |
1147 | if (!PageTransHuge(page)) |
1148 | __dec_zone_page_state(page, NR_ANON_PAGES); | |
1149 | else | |
1150 | __dec_zone_page_state(page, | |
1151 | NR_ANON_TRANSPARENT_HUGEPAGES); | |
b904dcfe KM |
1152 | } else { |
1153 | __dec_zone_page_state(page, NR_FILE_MAPPED); | |
2a7106f2 | 1154 | mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED); |
b904dcfe | 1155 | } |
b904dcfe KM |
1156 | /* |
1157 | * It would be tidy to reset the PageAnon mapping here, | |
1158 | * but that might overwrite a racing page_add_anon_rmap | |
1159 | * which increments mapcount after us but sets mapping | |
1160 | * before us: so leave the reset to free_hot_cold_page, | |
1161 | * and remember that it's only reliable while mapped. | |
1162 | * Leaving it set also helps swapoff to reinstate ptes | |
1163 | * faster for those pages still in swapcache. | |
1164 | */ | |
1da177e4 LT |
1165 | } |
1166 | ||
1167 | /* | |
1168 | * Subfunctions of try_to_unmap: try_to_unmap_one called | |
1169 | * repeatedly from either try_to_unmap_anon or try_to_unmap_file. | |
1170 | */ | |
5ad64688 HD |
1171 | int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
1172 | unsigned long address, enum ttu_flags flags) | |
1da177e4 LT |
1173 | { |
1174 | struct mm_struct *mm = vma->vm_mm; | |
1da177e4 LT |
1175 | pte_t *pte; |
1176 | pte_t pteval; | |
c0718806 | 1177 | spinlock_t *ptl; |
1da177e4 LT |
1178 | int ret = SWAP_AGAIN; |
1179 | ||
479db0bf | 1180 | pte = page_check_address(page, mm, address, &ptl, 0); |
c0718806 | 1181 | if (!pte) |
81b4082d | 1182 | goto out; |
1da177e4 LT |
1183 | |
1184 | /* | |
1185 | * If the page is mlock()d, we cannot swap it out. | |
1186 | * If it's recently referenced (perhaps page_referenced | |
1187 | * skipped over this mm) then we should reactivate it. | |
1188 | */ | |
14fa31b8 | 1189 | if (!(flags & TTU_IGNORE_MLOCK)) { |
caed0f48 KM |
1190 | if (vma->vm_flags & VM_LOCKED) |
1191 | goto out_mlock; | |
1192 | ||
af8e3354 | 1193 | if (TTU_ACTION(flags) == TTU_MUNLOCK) |
53f79acb | 1194 | goto out_unmap; |
14fa31b8 AK |
1195 | } |
1196 | if (!(flags & TTU_IGNORE_ACCESS)) { | |
b291f000 NP |
1197 | if (ptep_clear_flush_young_notify(vma, address, pte)) { |
1198 | ret = SWAP_FAIL; | |
1199 | goto out_unmap; | |
1200 | } | |
1201 | } | |
1da177e4 | 1202 | |
1da177e4 LT |
1203 | /* Nuke the page table entry. */ |
1204 | flush_cache_page(vma, address, page_to_pfn(page)); | |
cddb8a5c | 1205 | pteval = ptep_clear_flush_notify(vma, address, pte); |
1da177e4 LT |
1206 | |
1207 | /* Move the dirty bit to the physical page now the pte is gone. */ | |
1208 | if (pte_dirty(pteval)) | |
1209 | set_page_dirty(page); | |
1210 | ||
365e9c87 HD |
1211 | /* Update high watermark before we lower rss */ |
1212 | update_hiwater_rss(mm); | |
1213 | ||
888b9f7c AK |
1214 | if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
1215 | if (PageAnon(page)) | |
d559db08 | 1216 | dec_mm_counter(mm, MM_ANONPAGES); |
888b9f7c | 1217 | else |
d559db08 | 1218 | dec_mm_counter(mm, MM_FILEPAGES); |
888b9f7c AK |
1219 | set_pte_at(mm, address, pte, |
1220 | swp_entry_to_pte(make_hwpoison_entry(page))); | |
1221 | } else if (PageAnon(page)) { | |
4c21e2f2 | 1222 | swp_entry_t entry = { .val = page_private(page) }; |
0697212a CL |
1223 | |
1224 | if (PageSwapCache(page)) { | |
1225 | /* | |
1226 | * Store the swap location in the pte. | |
1227 | * See handle_pte_fault() ... | |
1228 | */ | |
570a335b HD |
1229 | if (swap_duplicate(entry) < 0) { |
1230 | set_pte_at(mm, address, pte, pteval); | |
1231 | ret = SWAP_FAIL; | |
1232 | goto out_unmap; | |
1233 | } | |
0697212a CL |
1234 | if (list_empty(&mm->mmlist)) { |
1235 | spin_lock(&mmlist_lock); | |
1236 | if (list_empty(&mm->mmlist)) | |
1237 | list_add(&mm->mmlist, &init_mm.mmlist); | |
1238 | spin_unlock(&mmlist_lock); | |
1239 | } | |
d559db08 | 1240 | dec_mm_counter(mm, MM_ANONPAGES); |
b084d435 | 1241 | inc_mm_counter(mm, MM_SWAPENTS); |
64cdd548 | 1242 | } else if (PAGE_MIGRATION) { |
0697212a CL |
1243 | /* |
1244 | * Store the pfn of the page in a special migration | |
1245 | * pte. do_swap_page() will wait until the migration | |
1246 | * pte is removed and then restart fault handling. | |
1247 | */ | |
14fa31b8 | 1248 | BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION); |
0697212a | 1249 | entry = make_migration_entry(page, pte_write(pteval)); |
1da177e4 LT |
1250 | } |
1251 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); | |
1252 | BUG_ON(pte_file(*pte)); | |
14fa31b8 | 1253 | } else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) { |
04e62a29 CL |
1254 | /* Establish migration entry for a file page */ |
1255 | swp_entry_t entry; | |
1256 | entry = make_migration_entry(page, pte_write(pteval)); | |
1257 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); | |
1258 | } else | |
d559db08 | 1259 | dec_mm_counter(mm, MM_FILEPAGES); |
1da177e4 | 1260 | |
edc315fd | 1261 | page_remove_rmap(page); |
1da177e4 LT |
1262 | page_cache_release(page); |
1263 | ||
1264 | out_unmap: | |
c0718806 | 1265 | pte_unmap_unlock(pte, ptl); |
caed0f48 KM |
1266 | out: |
1267 | return ret; | |
53f79acb | 1268 | |
caed0f48 KM |
1269 | out_mlock: |
1270 | pte_unmap_unlock(pte, ptl); | |
1271 | ||
1272 | ||
1273 | /* | |
1274 | * We need mmap_sem locking, Otherwise VM_LOCKED check makes | |
1275 | * unstable result and race. Plus, We can't wait here because | |
2b575eb6 | 1276 | * we now hold anon_vma->mutex or mapping->i_mmap_mutex. |
caed0f48 KM |
1277 | * if trylock failed, the page remain in evictable lru and later |
1278 | * vmscan could retry to move the page to unevictable lru if the | |
1279 | * page is actually mlocked. | |
1280 | */ | |
1281 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { | |
1282 | if (vma->vm_flags & VM_LOCKED) { | |
1283 | mlock_vma_page(page); | |
1284 | ret = SWAP_MLOCK; | |
53f79acb | 1285 | } |
caed0f48 | 1286 | up_read(&vma->vm_mm->mmap_sem); |
53f79acb | 1287 | } |
1da177e4 LT |
1288 | return ret; |
1289 | } | |
1290 | ||
1291 | /* | |
1292 | * objrmap doesn't work for nonlinear VMAs because the assumption that | |
1293 | * offset-into-file correlates with offset-into-virtual-addresses does not hold. | |
1294 | * Consequently, given a particular page and its ->index, we cannot locate the | |
1295 | * ptes which are mapping that page without an exhaustive linear search. | |
1296 | * | |
1297 | * So what this code does is a mini "virtual scan" of each nonlinear VMA which | |
1298 | * maps the file to which the target page belongs. The ->vm_private_data field | |
1299 | * holds the current cursor into that scan. Successive searches will circulate | |
1300 | * around the vma's virtual address space. | |
1301 | * | |
1302 | * So as more replacement pressure is applied to the pages in a nonlinear VMA, | |
1303 | * more scanning pressure is placed against them as well. Eventually pages | |
1304 | * will become fully unmapped and are eligible for eviction. | |
1305 | * | |
1306 | * For very sparsely populated VMAs this is a little inefficient - chances are | |
1307 | * there there won't be many ptes located within the scan cluster. In this case | |
1308 | * maybe we could scan further - to the end of the pte page, perhaps. | |
b291f000 NP |
1309 | * |
1310 | * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can | |
1311 | * acquire it without blocking. If vma locked, mlock the pages in the cluster, | |
1312 | * rather than unmapping them. If we encounter the "check_page" that vmscan is | |
1313 | * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN. | |
1da177e4 LT |
1314 | */ |
1315 | #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) | |
1316 | #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) | |
1317 | ||
b291f000 NP |
1318 | static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, |
1319 | struct vm_area_struct *vma, struct page *check_page) | |
1da177e4 LT |
1320 | { |
1321 | struct mm_struct *mm = vma->vm_mm; | |
1322 | pgd_t *pgd; | |
1323 | pud_t *pud; | |
1324 | pmd_t *pmd; | |
c0718806 | 1325 | pte_t *pte; |
1da177e4 | 1326 | pte_t pteval; |
c0718806 | 1327 | spinlock_t *ptl; |
1da177e4 LT |
1328 | struct page *page; |
1329 | unsigned long address; | |
1330 | unsigned long end; | |
b291f000 NP |
1331 | int ret = SWAP_AGAIN; |
1332 | int locked_vma = 0; | |
1da177e4 | 1333 | |
1da177e4 LT |
1334 | address = (vma->vm_start + cursor) & CLUSTER_MASK; |
1335 | end = address + CLUSTER_SIZE; | |
1336 | if (address < vma->vm_start) | |
1337 | address = vma->vm_start; | |
1338 | if (end > vma->vm_end) | |
1339 | end = vma->vm_end; | |
1340 | ||
1341 | pgd = pgd_offset(mm, address); | |
1342 | if (!pgd_present(*pgd)) | |
b291f000 | 1343 | return ret; |
1da177e4 LT |
1344 | |
1345 | pud = pud_offset(pgd, address); | |
1346 | if (!pud_present(*pud)) | |
b291f000 | 1347 | return ret; |
1da177e4 LT |
1348 | |
1349 | pmd = pmd_offset(pud, address); | |
1350 | if (!pmd_present(*pmd)) | |
b291f000 NP |
1351 | return ret; |
1352 | ||
1353 | /* | |
af8e3354 | 1354 | * If we can acquire the mmap_sem for read, and vma is VM_LOCKED, |
b291f000 NP |
1355 | * keep the sem while scanning the cluster for mlocking pages. |
1356 | */ | |
af8e3354 | 1357 | if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
b291f000 NP |
1358 | locked_vma = (vma->vm_flags & VM_LOCKED); |
1359 | if (!locked_vma) | |
1360 | up_read(&vma->vm_mm->mmap_sem); /* don't need it */ | |
1361 | } | |
c0718806 HD |
1362 | |
1363 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); | |
1da177e4 | 1364 | |
365e9c87 HD |
1365 | /* Update high watermark before we lower rss */ |
1366 | update_hiwater_rss(mm); | |
1367 | ||
c0718806 | 1368 | for (; address < end; pte++, address += PAGE_SIZE) { |
1da177e4 LT |
1369 | if (!pte_present(*pte)) |
1370 | continue; | |
6aab341e LT |
1371 | page = vm_normal_page(vma, address, *pte); |
1372 | BUG_ON(!page || PageAnon(page)); | |
1da177e4 | 1373 | |
b291f000 NP |
1374 | if (locked_vma) { |
1375 | mlock_vma_page(page); /* no-op if already mlocked */ | |
1376 | if (page == check_page) | |
1377 | ret = SWAP_MLOCK; | |
1378 | continue; /* don't unmap */ | |
1379 | } | |
1380 | ||
cddb8a5c | 1381 | if (ptep_clear_flush_young_notify(vma, address, pte)) |
1da177e4 LT |
1382 | continue; |
1383 | ||
1384 | /* Nuke the page table entry. */ | |
eca35133 | 1385 | flush_cache_page(vma, address, pte_pfn(*pte)); |
cddb8a5c | 1386 | pteval = ptep_clear_flush_notify(vma, address, pte); |
1da177e4 LT |
1387 | |
1388 | /* If nonlinear, store the file page offset in the pte. */ | |
1389 | if (page->index != linear_page_index(vma, address)) | |
1390 | set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); | |
1391 | ||
1392 | /* Move the dirty bit to the physical page now the pte is gone. */ | |
1393 | if (pte_dirty(pteval)) | |
1394 | set_page_dirty(page); | |
1395 | ||
edc315fd | 1396 | page_remove_rmap(page); |
1da177e4 | 1397 | page_cache_release(page); |
d559db08 | 1398 | dec_mm_counter(mm, MM_FILEPAGES); |
1da177e4 LT |
1399 | (*mapcount)--; |
1400 | } | |
c0718806 | 1401 | pte_unmap_unlock(pte - 1, ptl); |
b291f000 NP |
1402 | if (locked_vma) |
1403 | up_read(&vma->vm_mm->mmap_sem); | |
1404 | return ret; | |
1da177e4 LT |
1405 | } |
1406 | ||
71e3aac0 | 1407 | bool is_vma_temporary_stack(struct vm_area_struct *vma) |
a8bef8ff MG |
1408 | { |
1409 | int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP); | |
1410 | ||
1411 | if (!maybe_stack) | |
1412 | return false; | |
1413 | ||
1414 | if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) == | |
1415 | VM_STACK_INCOMPLETE_SETUP) | |
1416 | return true; | |
1417 | ||
1418 | return false; | |
1419 | } | |
1420 | ||
b291f000 NP |
1421 | /** |
1422 | * try_to_unmap_anon - unmap or unlock anonymous page using the object-based | |
1423 | * rmap method | |
1424 | * @page: the page to unmap/unlock | |
8051be5e | 1425 | * @flags: action and flags |
b291f000 NP |
1426 | * |
1427 | * Find all the mappings of a page using the mapping pointer and the vma chains | |
1428 | * contained in the anon_vma struct it points to. | |
1429 | * | |
1430 | * This function is only called from try_to_unmap/try_to_munlock for | |
1431 | * anonymous pages. | |
1432 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma | |
1433 | * where the page was found will be held for write. So, we won't recheck | |
1434 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be | |
1435 | * 'LOCKED. | |
1436 | */ | |
14fa31b8 | 1437 | static int try_to_unmap_anon(struct page *page, enum ttu_flags flags) |
1da177e4 LT |
1438 | { |
1439 | struct anon_vma *anon_vma; | |
5beb4930 | 1440 | struct anon_vma_chain *avc; |
1da177e4 | 1441 | int ret = SWAP_AGAIN; |
b291f000 | 1442 | |
1da177e4 LT |
1443 | anon_vma = page_lock_anon_vma(page); |
1444 | if (!anon_vma) | |
1445 | return ret; | |
1446 | ||
5beb4930 RR |
1447 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
1448 | struct vm_area_struct *vma = avc->vma; | |
a8bef8ff MG |
1449 | unsigned long address; |
1450 | ||
1451 | /* | |
1452 | * During exec, a temporary VMA is setup and later moved. | |
1453 | * The VMA is moved under the anon_vma lock but not the | |
1454 | * page tables leading to a race where migration cannot | |
1455 | * find the migration ptes. Rather than increasing the | |
1456 | * locking requirements of exec(), migration skips | |
1457 | * temporary VMAs until after exec() completes. | |
1458 | */ | |
1459 | if (PAGE_MIGRATION && (flags & TTU_MIGRATION) && | |
1460 | is_vma_temporary_stack(vma)) | |
1461 | continue; | |
1462 | ||
1463 | address = vma_address(page, vma); | |
1cb1729b HD |
1464 | if (address == -EFAULT) |
1465 | continue; | |
1466 | ret = try_to_unmap_one(page, vma, address, flags); | |
53f79acb HD |
1467 | if (ret != SWAP_AGAIN || !page_mapped(page)) |
1468 | break; | |
1da177e4 | 1469 | } |
34bbd704 ON |
1470 | |
1471 | page_unlock_anon_vma(anon_vma); | |
1da177e4 LT |
1472 | return ret; |
1473 | } | |
1474 | ||
1475 | /** | |
b291f000 NP |
1476 | * try_to_unmap_file - unmap/unlock file page using the object-based rmap method |
1477 | * @page: the page to unmap/unlock | |
14fa31b8 | 1478 | * @flags: action and flags |
1da177e4 LT |
1479 | * |
1480 | * Find all the mappings of a page using the mapping pointer and the vma chains | |
1481 | * contained in the address_space struct it points to. | |
1482 | * | |
b291f000 NP |
1483 | * This function is only called from try_to_unmap/try_to_munlock for |
1484 | * object-based pages. | |
1485 | * When called from try_to_munlock(), the mmap_sem of the mm containing the vma | |
1486 | * where the page was found will be held for write. So, we won't recheck | |
1487 | * vm_flags for that VMA. That should be OK, because that vma shouldn't be | |
1488 | * 'LOCKED. | |
1da177e4 | 1489 | */ |
14fa31b8 | 1490 | static int try_to_unmap_file(struct page *page, enum ttu_flags flags) |
1da177e4 LT |
1491 | { |
1492 | struct address_space *mapping = page->mapping; | |
1493 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
1494 | struct vm_area_struct *vma; | |
1495 | struct prio_tree_iter iter; | |
1496 | int ret = SWAP_AGAIN; | |
1497 | unsigned long cursor; | |
1498 | unsigned long max_nl_cursor = 0; | |
1499 | unsigned long max_nl_size = 0; | |
1500 | unsigned int mapcount; | |
1501 | ||
3d48ae45 | 1502 | mutex_lock(&mapping->i_mmap_mutex); |
1da177e4 | 1503 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1cb1729b HD |
1504 | unsigned long address = vma_address(page, vma); |
1505 | if (address == -EFAULT) | |
1506 | continue; | |
1507 | ret = try_to_unmap_one(page, vma, address, flags); | |
53f79acb HD |
1508 | if (ret != SWAP_AGAIN || !page_mapped(page)) |
1509 | goto out; | |
1da177e4 LT |
1510 | } |
1511 | ||
1512 | if (list_empty(&mapping->i_mmap_nonlinear)) | |
1513 | goto out; | |
1514 | ||
53f79acb HD |
1515 | /* |
1516 | * We don't bother to try to find the munlocked page in nonlinears. | |
1517 | * It's costly. Instead, later, page reclaim logic may call | |
1518 | * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily. | |
1519 | */ | |
1520 | if (TTU_ACTION(flags) == TTU_MUNLOCK) | |
1521 | goto out; | |
1522 | ||
1da177e4 LT |
1523 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
1524 | shared.vm_set.list) { | |
1da177e4 LT |
1525 | cursor = (unsigned long) vma->vm_private_data; |
1526 | if (cursor > max_nl_cursor) | |
1527 | max_nl_cursor = cursor; | |
1528 | cursor = vma->vm_end - vma->vm_start; | |
1529 | if (cursor > max_nl_size) | |
1530 | max_nl_size = cursor; | |
1531 | } | |
1532 | ||
b291f000 | 1533 | if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ |
1da177e4 LT |
1534 | ret = SWAP_FAIL; |
1535 | goto out; | |
1536 | } | |
1537 | ||
1538 | /* | |
1539 | * We don't try to search for this page in the nonlinear vmas, | |
1540 | * and page_referenced wouldn't have found it anyway. Instead | |
1541 | * just walk the nonlinear vmas trying to age and unmap some. | |
1542 | * The mapcount of the page we came in with is irrelevant, | |
1543 | * but even so use it as a guide to how hard we should try? | |
1544 | */ | |
1545 | mapcount = page_mapcount(page); | |
1546 | if (!mapcount) | |
1547 | goto out; | |
3d48ae45 | 1548 | cond_resched(); |
1da177e4 LT |
1549 | |
1550 | max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; | |
1551 | if (max_nl_cursor == 0) | |
1552 | max_nl_cursor = CLUSTER_SIZE; | |
1553 | ||
1554 | do { | |
1555 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, | |
1556 | shared.vm_set.list) { | |
1da177e4 | 1557 | cursor = (unsigned long) vma->vm_private_data; |
839b9685 | 1558 | while ( cursor < max_nl_cursor && |
1da177e4 | 1559 | cursor < vma->vm_end - vma->vm_start) { |
53f79acb HD |
1560 | if (try_to_unmap_cluster(cursor, &mapcount, |
1561 | vma, page) == SWAP_MLOCK) | |
1562 | ret = SWAP_MLOCK; | |
1da177e4 LT |
1563 | cursor += CLUSTER_SIZE; |
1564 | vma->vm_private_data = (void *) cursor; | |
1565 | if ((int)mapcount <= 0) | |
1566 | goto out; | |
1567 | } | |
1568 | vma->vm_private_data = (void *) max_nl_cursor; | |
1569 | } | |
3d48ae45 | 1570 | cond_resched(); |
1da177e4 LT |
1571 | max_nl_cursor += CLUSTER_SIZE; |
1572 | } while (max_nl_cursor <= max_nl_size); | |
1573 | ||
1574 | /* | |
1575 | * Don't loop forever (perhaps all the remaining pages are | |
1576 | * in locked vmas). Reset cursor on all unreserved nonlinear | |
1577 | * vmas, now forgetting on which ones it had fallen behind. | |
1578 | */ | |
101d2be7 HD |
1579 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
1580 | vma->vm_private_data = NULL; | |
1da177e4 | 1581 | out: |
3d48ae45 | 1582 | mutex_unlock(&mapping->i_mmap_mutex); |
1da177e4 LT |
1583 | return ret; |
1584 | } | |
1585 | ||
1586 | /** | |
1587 | * try_to_unmap - try to remove all page table mappings to a page | |
1588 | * @page: the page to get unmapped | |
14fa31b8 | 1589 | * @flags: action and flags |
1da177e4 LT |
1590 | * |
1591 | * Tries to remove all the page table entries which are mapping this | |
1592 | * page, used in the pageout path. Caller must hold the page lock. | |
1593 | * Return values are: | |
1594 | * | |
1595 | * SWAP_SUCCESS - we succeeded in removing all mappings | |
1596 | * SWAP_AGAIN - we missed a mapping, try again later | |
1597 | * SWAP_FAIL - the page is unswappable | |
b291f000 | 1598 | * SWAP_MLOCK - page is mlocked. |
1da177e4 | 1599 | */ |
14fa31b8 | 1600 | int try_to_unmap(struct page *page, enum ttu_flags flags) |
1da177e4 LT |
1601 | { |
1602 | int ret; | |
1603 | ||
1da177e4 | 1604 | BUG_ON(!PageLocked(page)); |
91600e9e | 1605 | VM_BUG_ON(!PageHuge(page) && PageTransHuge(page)); |
1da177e4 | 1606 | |
5ad64688 HD |
1607 | if (unlikely(PageKsm(page))) |
1608 | ret = try_to_unmap_ksm(page, flags); | |
1609 | else if (PageAnon(page)) | |
14fa31b8 | 1610 | ret = try_to_unmap_anon(page, flags); |
1da177e4 | 1611 | else |
14fa31b8 | 1612 | ret = try_to_unmap_file(page, flags); |
b291f000 | 1613 | if (ret != SWAP_MLOCK && !page_mapped(page)) |
1da177e4 LT |
1614 | ret = SWAP_SUCCESS; |
1615 | return ret; | |
1616 | } | |
81b4082d | 1617 | |
b291f000 NP |
1618 | /** |
1619 | * try_to_munlock - try to munlock a page | |
1620 | * @page: the page to be munlocked | |
1621 | * | |
1622 | * Called from munlock code. Checks all of the VMAs mapping the page | |
1623 | * to make sure nobody else has this page mlocked. The page will be | |
1624 | * returned with PG_mlocked cleared if no other vmas have it mlocked. | |
1625 | * | |
1626 | * Return values are: | |
1627 | * | |
53f79acb | 1628 | * SWAP_AGAIN - no vma is holding page mlocked, or, |
b291f000 | 1629 | * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem |
5ad64688 | 1630 | * SWAP_FAIL - page cannot be located at present |
b291f000 NP |
1631 | * SWAP_MLOCK - page is now mlocked. |
1632 | */ | |
1633 | int try_to_munlock(struct page *page) | |
1634 | { | |
1635 | VM_BUG_ON(!PageLocked(page) || PageLRU(page)); | |
1636 | ||
5ad64688 HD |
1637 | if (unlikely(PageKsm(page))) |
1638 | return try_to_unmap_ksm(page, TTU_MUNLOCK); | |
1639 | else if (PageAnon(page)) | |
14fa31b8 | 1640 | return try_to_unmap_anon(page, TTU_MUNLOCK); |
b291f000 | 1641 | else |
14fa31b8 | 1642 | return try_to_unmap_file(page, TTU_MUNLOCK); |
b291f000 | 1643 | } |
e9995ef9 | 1644 | |
01d8b20d | 1645 | void __put_anon_vma(struct anon_vma *anon_vma) |
76545066 | 1646 | { |
01d8b20d | 1647 | struct anon_vma *root = anon_vma->root; |
76545066 | 1648 | |
01d8b20d PZ |
1649 | if (root != anon_vma && atomic_dec_and_test(&root->refcount)) |
1650 | anon_vma_free(root); | |
76545066 | 1651 | |
01d8b20d | 1652 | anon_vma_free(anon_vma); |
76545066 | 1653 | } |
76545066 | 1654 | |
e9995ef9 HD |
1655 | #ifdef CONFIG_MIGRATION |
1656 | /* | |
1657 | * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file(): | |
1658 | * Called by migrate.c to remove migration ptes, but might be used more later. | |
1659 | */ | |
1660 | static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, | |
1661 | struct vm_area_struct *, unsigned long, void *), void *arg) | |
1662 | { | |
1663 | struct anon_vma *anon_vma; | |
5beb4930 | 1664 | struct anon_vma_chain *avc; |
e9995ef9 HD |
1665 | int ret = SWAP_AGAIN; |
1666 | ||
1667 | /* | |
1668 | * Note: remove_migration_ptes() cannot use page_lock_anon_vma() | |
1669 | * because that depends on page_mapped(); but not all its usages | |
3f6c8272 MG |
1670 | * are holding mmap_sem. Users without mmap_sem are required to |
1671 | * take a reference count to prevent the anon_vma disappearing | |
e9995ef9 HD |
1672 | */ |
1673 | anon_vma = page_anon_vma(page); | |
1674 | if (!anon_vma) | |
1675 | return ret; | |
cba48b98 | 1676 | anon_vma_lock(anon_vma); |
5beb4930 RR |
1677 | list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
1678 | struct vm_area_struct *vma = avc->vma; | |
e9995ef9 HD |
1679 | unsigned long address = vma_address(page, vma); |
1680 | if (address == -EFAULT) | |
1681 | continue; | |
1682 | ret = rmap_one(page, vma, address, arg); | |
1683 | if (ret != SWAP_AGAIN) | |
1684 | break; | |
1685 | } | |
cba48b98 | 1686 | anon_vma_unlock(anon_vma); |
e9995ef9 HD |
1687 | return ret; |
1688 | } | |
1689 | ||
1690 | static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *, | |
1691 | struct vm_area_struct *, unsigned long, void *), void *arg) | |
1692 | { | |
1693 | struct address_space *mapping = page->mapping; | |
1694 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
1695 | struct vm_area_struct *vma; | |
1696 | struct prio_tree_iter iter; | |
1697 | int ret = SWAP_AGAIN; | |
1698 | ||
1699 | if (!mapping) | |
1700 | return ret; | |
3d48ae45 | 1701 | mutex_lock(&mapping->i_mmap_mutex); |
e9995ef9 HD |
1702 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
1703 | unsigned long address = vma_address(page, vma); | |
1704 | if (address == -EFAULT) | |
1705 | continue; | |
1706 | ret = rmap_one(page, vma, address, arg); | |
1707 | if (ret != SWAP_AGAIN) | |
1708 | break; | |
1709 | } | |
1710 | /* | |
1711 | * No nonlinear handling: being always shared, nonlinear vmas | |
1712 | * never contain migration ptes. Decide what to do about this | |
1713 | * limitation to linear when we need rmap_walk() on nonlinear. | |
1714 | */ | |
3d48ae45 | 1715 | mutex_unlock(&mapping->i_mmap_mutex); |
e9995ef9 HD |
1716 | return ret; |
1717 | } | |
1718 | ||
1719 | int rmap_walk(struct page *page, int (*rmap_one)(struct page *, | |
1720 | struct vm_area_struct *, unsigned long, void *), void *arg) | |
1721 | { | |
1722 | VM_BUG_ON(!PageLocked(page)); | |
1723 | ||
1724 | if (unlikely(PageKsm(page))) | |
1725 | return rmap_walk_ksm(page, rmap_one, arg); | |
1726 | else if (PageAnon(page)) | |
1727 | return rmap_walk_anon(page, rmap_one, arg); | |
1728 | else | |
1729 | return rmap_walk_file(page, rmap_one, arg); | |
1730 | } | |
1731 | #endif /* CONFIG_MIGRATION */ | |
0fe6e20b | 1732 | |
e3390f67 | 1733 | #ifdef CONFIG_HUGETLB_PAGE |
0fe6e20b NH |
1734 | /* |
1735 | * The following three functions are for anonymous (private mapped) hugepages. | |
1736 | * Unlike common anonymous pages, anonymous hugepages have no accounting code | |
1737 | * and no lru code, because we handle hugepages differently from common pages. | |
1738 | */ | |
1739 | static void __hugepage_set_anon_rmap(struct page *page, | |
1740 | struct vm_area_struct *vma, unsigned long address, int exclusive) | |
1741 | { | |
1742 | struct anon_vma *anon_vma = vma->anon_vma; | |
433abed6 | 1743 | |
0fe6e20b | 1744 | BUG_ON(!anon_vma); |
433abed6 NH |
1745 | |
1746 | if (PageAnon(page)) | |
1747 | return; | |
1748 | if (!exclusive) | |
1749 | anon_vma = anon_vma->root; | |
1750 | ||
0fe6e20b NH |
1751 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
1752 | page->mapping = (struct address_space *) anon_vma; | |
1753 | page->index = linear_page_index(vma, address); | |
1754 | } | |
1755 | ||
1756 | void hugepage_add_anon_rmap(struct page *page, | |
1757 | struct vm_area_struct *vma, unsigned long address) | |
1758 | { | |
1759 | struct anon_vma *anon_vma = vma->anon_vma; | |
1760 | int first; | |
a850ea30 NH |
1761 | |
1762 | BUG_ON(!PageLocked(page)); | |
0fe6e20b | 1763 | BUG_ON(!anon_vma); |
5dbe0af4 | 1764 | /* address might be in next vma when migration races vma_adjust */ |
0fe6e20b NH |
1765 | first = atomic_inc_and_test(&page->_mapcount); |
1766 | if (first) | |
1767 | __hugepage_set_anon_rmap(page, vma, address, 0); | |
1768 | } | |
1769 | ||
1770 | void hugepage_add_new_anon_rmap(struct page *page, | |
1771 | struct vm_area_struct *vma, unsigned long address) | |
1772 | { | |
1773 | BUG_ON(address < vma->vm_start || address >= vma->vm_end); | |
1774 | atomic_set(&page->_mapcount, 0); | |
1775 | __hugepage_set_anon_rmap(page, vma, address, 1); | |
1776 | } | |
e3390f67 | 1777 | #endif /* CONFIG_HUGETLB_PAGE */ |