blob: 941bf82e896128b618284ae17a25d963c13838fc [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * mm/rmap.c - physical to virtual reverse mappings
3 *
4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
5 * Released under the General Public License (GPL).
6 *
7 * Simple, low overhead reverse mapping scheme.
8 * Please try to keep this thing as modular as possible.
9 *
10 * Provides methods for unmapping each kind of mapped page:
11 * the anon methods track anonymous pages, and
12 * the file methods track pages belonging to an inode.
13 *
14 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
15 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
16 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
Hugh Dickins98f32602009-05-21 20:33:58 +010017 * Contributions by Hugh Dickins 2003, 2004
Linus Torvalds1da177e2005-04-16 15:20:36 -070018 */
19
20/*
21 * Lock ordering in mm:
22 *
Jes Sorensen1b1dcc12006-01-09 15:59:24 -080023 * inode->i_mutex (while writing or truncating, not reading or faulting)
Nick Piggin82591e62006-10-19 23:29:10 -070024 * 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)
Andi Kleen6a460792009-09-16 11:50:15 +020039 *
40 * (code doesn't rely on that order so it could be switched around)
41 * ->tasklist_lock
42 * anon_vma->lock (memory_failure, collect_procs_anon)
43 * pte map lock
Linus Torvalds1da177e2005-04-16 15:20:36 -070044 */
45
46#include <linux/mm.h>
47#include <linux/pagemap.h>
48#include <linux/swap.h>
49#include <linux/swapops.h>
50#include <linux/slab.h>
51#include <linux/init.h>
Hugh Dickins5ad64682009-12-14 17:59:24 -080052#include <linux/ksm.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070053#include <linux/rmap.h>
54#include <linux/rcupdate.h>
Christoph Lametera48d07a2006-02-01 03:05:38 -080055#include <linux/module.h>
Balbir Singh8a9f3cc2008-02-07 00:13:53 -080056#include <linux/memcontrol.h>
Andrea Arcangelicddb8a52008-07-28 15:46:29 -070057#include <linux/mmu_notifier.h>
KOSAKI Motohiro64cdd542009-01-06 14:39:16 -080058#include <linux/migrate.h>
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +090059#include <linux/hugetlb.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
61#include <asm/tlbflush.h>
62
Nick Pigginb291f002008-10-18 20:26:44 -070063#include "internal.h"
64
Adrian Bunkfdd2e5f2008-10-18 20:28:38 -070065static struct kmem_cache *anon_vma_cachep;
Rik van Riel5beb4932010-03-05 13:42:07 -080066static struct kmem_cache *anon_vma_chain_cachep;
Adrian Bunkfdd2e5f2008-10-18 20:28:38 -070067
68static inline struct anon_vma *anon_vma_alloc(void)
69{
70 return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
71}
72
Hugh Dickinsdb114b82009-12-14 17:59:25 -080073void anon_vma_free(struct anon_vma *anon_vma)
Adrian Bunkfdd2e5f2008-10-18 20:28:38 -070074{
75 kmem_cache_free(anon_vma_cachep, anon_vma);
76}
Linus Torvalds1da177e2005-04-16 15:20:36 -070077
Rik van Riel5beb4932010-03-05 13:42:07 -080078static inline struct anon_vma_chain *anon_vma_chain_alloc(void)
79{
80 return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL);
81}
82
Namhyung Kime574b5f2010-10-26 14:22:02 -070083static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
Rik van Riel5beb4932010-03-05 13:42:07 -080084{
85 kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
86}
87
Linus Torvaldsd9d332e2008-10-19 10:32:20 -070088/**
89 * anon_vma_prepare - attach an anon_vma to a memory region
90 * @vma: the memory region in question
91 *
92 * This makes sure the memory mapping described by 'vma' has
93 * an 'anon_vma' attached to it, so that we can associate the
94 * anonymous pages mapped into it with that anon_vma.
95 *
96 * The common case will be that we already have one, but if
Figo.zhang23a07902010-12-27 15:14:06 +010097 * not we either need to find an adjacent mapping that we
Linus Torvaldsd9d332e2008-10-19 10:32:20 -070098 * can re-use the anon_vma from (very common when the only
99 * reason for splitting a vma has been mprotect()), or we
100 * allocate a new one.
101 *
102 * Anon-vma allocations are very subtle, because we may have
103 * optimistically looked up an anon_vma in page_lock_anon_vma()
104 * and that may actually touch the spinlock even in the newly
105 * allocated vma (it depends on RCU to make sure that the
106 * anon_vma isn't actually destroyed).
107 *
108 * As a result, we need to do proper anon_vma locking even
109 * for the new allocation. At the same time, we do not want
110 * to do any locking for the common case of already having
111 * an anon_vma.
112 *
113 * This must be called with the mmap_sem held for reading.
114 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115int anon_vma_prepare(struct vm_area_struct *vma)
116{
117 struct anon_vma *anon_vma = vma->anon_vma;
Rik van Riel5beb4932010-03-05 13:42:07 -0800118 struct anon_vma_chain *avc;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
120 might_sleep();
121 if (unlikely(!anon_vma)) {
122 struct mm_struct *mm = vma->vm_mm;
Linus Torvaldsd9d332e2008-10-19 10:32:20 -0700123 struct anon_vma *allocated;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124
Rik van Riel5beb4932010-03-05 13:42:07 -0800125 avc = anon_vma_chain_alloc();
126 if (!avc)
127 goto out_enomem;
128
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129 anon_vma = find_mergeable_anon_vma(vma);
Linus Torvaldsd9d332e2008-10-19 10:32:20 -0700130 allocated = NULL;
131 if (!anon_vma) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132 anon_vma = anon_vma_alloc();
133 if (unlikely(!anon_vma))
Rik van Riel5beb4932010-03-05 13:42:07 -0800134 goto out_enomem_free_avc;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 allocated = anon_vma;
Rik van Riel5c341ee2010-08-09 17:18:39 -0700136 /*
137 * This VMA had no anon_vma yet. This anon_vma is
138 * the root of any anon_vma tree that might form.
139 */
140 anon_vma->root = anon_vma;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 }
142
Rik van Rielcba48b92010-08-09 17:18:38 -0700143 anon_vma_lock(anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 /* page_table_lock to protect against threads */
145 spin_lock(&mm->page_table_lock);
146 if (likely(!vma->anon_vma)) {
147 vma->anon_vma = anon_vma;
Rik van Riel5beb4932010-03-05 13:42:07 -0800148 avc->anon_vma = anon_vma;
149 avc->vma = vma;
150 list_add(&avc->same_vma, &vma->anon_vma_chain);
Andrea Arcangeli26ba0cb2010-08-09 17:19:08 -0700151 list_add_tail(&avc->same_anon_vma, &anon_vma->head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 allocated = NULL;
Oleg Nesterov31f2b0e2010-04-23 13:18:01 -0400153 avc = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154 }
155 spin_unlock(&mm->page_table_lock);
Rik van Rielcba48b92010-08-09 17:18:38 -0700156 anon_vma_unlock(anon_vma);
Oleg Nesterov31f2b0e2010-04-23 13:18:01 -0400157
158 if (unlikely(allocated))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 anon_vma_free(allocated);
Oleg Nesterov31f2b0e2010-04-23 13:18:01 -0400160 if (unlikely(avc))
Rik van Riel5beb4932010-03-05 13:42:07 -0800161 anon_vma_chain_free(avc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 }
163 return 0;
Rik van Riel5beb4932010-03-05 13:42:07 -0800164
165 out_enomem_free_avc:
166 anon_vma_chain_free(avc);
167 out_enomem:
168 return -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169}
170
Rik van Riel5beb4932010-03-05 13:42:07 -0800171static void anon_vma_chain_link(struct vm_area_struct *vma,
172 struct anon_vma_chain *avc,
173 struct anon_vma *anon_vma)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174{
Rik van Riel5beb4932010-03-05 13:42:07 -0800175 avc->vma = vma;
176 avc->anon_vma = anon_vma;
177 list_add(&avc->same_vma, &vma->anon_vma_chain);
178
Rik van Rielcba48b92010-08-09 17:18:38 -0700179 anon_vma_lock(anon_vma);
Andrea Arcangeli05759d32011-01-13 15:46:53 -0800180 /*
181 * It's critical to add new vmas to the tail of the anon_vma,
182 * see comment in huge_memory.c:__split_huge_page().
183 */
Rik van Riel5beb4932010-03-05 13:42:07 -0800184 list_add_tail(&avc->same_anon_vma, &anon_vma->head);
Rik van Rielcba48b92010-08-09 17:18:38 -0700185 anon_vma_unlock(anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186}
187
Rik van Riel5beb4932010-03-05 13:42:07 -0800188/*
189 * Attach the anon_vmas from src to dst.
190 * Returns 0 on success, -ENOMEM on failure.
191 */
192int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193{
Rik van Riel5beb4932010-03-05 13:42:07 -0800194 struct anon_vma_chain *avc, *pavc;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195
Linus Torvalds646d87b2010-04-11 17:15:03 -0700196 list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
Rik van Riel5beb4932010-03-05 13:42:07 -0800197 avc = anon_vma_chain_alloc();
198 if (!avc)
199 goto enomem_failure;
200 anon_vma_chain_link(dst, avc, pavc->anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 }
Rik van Riel5beb4932010-03-05 13:42:07 -0800202 return 0;
203
204 enomem_failure:
205 unlink_anon_vmas(dst);
206 return -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207}
208
Rik van Riel5beb4932010-03-05 13:42:07 -0800209/*
210 * Attach vma to its own anon_vma, as well as to the anon_vmas that
211 * the corresponding VMA in the parent process is attached to.
212 * Returns 0 on success, non-zero on failure.
213 */
214int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215{
Rik van Riel5beb4932010-03-05 13:42:07 -0800216 struct anon_vma_chain *avc;
217 struct anon_vma *anon_vma;
218
219 /* Don't bother if the parent process has no anon_vma here. */
220 if (!pvma->anon_vma)
221 return 0;
222
223 /*
224 * First, attach the new VMA to the parent VMA's anon_vmas,
225 * so rmap can find non-COWed pages in child processes.
226 */
227 if (anon_vma_clone(vma, pvma))
228 return -ENOMEM;
229
230 /* Then add our own anon_vma. */
231 anon_vma = anon_vma_alloc();
232 if (!anon_vma)
233 goto out_error;
234 avc = anon_vma_chain_alloc();
235 if (!avc)
236 goto out_error_free_anon_vma;
Rik van Riel5c341ee2010-08-09 17:18:39 -0700237
238 /*
239 * The root anon_vma's spinlock is the lock actually used when we
240 * lock any of the anon_vmas in this anon_vma tree.
241 */
242 anon_vma->root = pvma->anon_vma->root;
Rik van Riel76545062010-08-09 17:18:41 -0700243 /*
244 * With KSM refcounts, an anon_vma can stay around longer than the
245 * process it belongs to. The root anon_vma needs to be pinned
246 * until this anon_vma is freed, because the lock lives in the root.
247 */
248 get_anon_vma(anon_vma->root);
Rik van Riel5beb4932010-03-05 13:42:07 -0800249 /* Mark this anon_vma as the one where our new (COWed) pages go. */
250 vma->anon_vma = anon_vma;
Rik van Riel5c341ee2010-08-09 17:18:39 -0700251 anon_vma_chain_link(vma, avc, anon_vma);
Rik van Riel5beb4932010-03-05 13:42:07 -0800252
253 return 0;
254
255 out_error_free_anon_vma:
256 anon_vma_free(anon_vma);
257 out_error:
Rik van Riel4946d542010-04-05 12:13:33 -0400258 unlink_anon_vmas(vma);
Rik van Riel5beb4932010-03-05 13:42:07 -0800259 return -ENOMEM;
260}
261
262static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
263{
264 struct anon_vma *anon_vma = anon_vma_chain->anon_vma;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 int empty;
266
Rik van Riel5beb4932010-03-05 13:42:07 -0800267 /* If anon_vma_fork fails, we can get an empty anon_vma_chain. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268 if (!anon_vma)
269 return;
270
Rik van Rielcba48b92010-08-09 17:18:38 -0700271 anon_vma_lock(anon_vma);
Rik van Riel5beb4932010-03-05 13:42:07 -0800272 list_del(&anon_vma_chain->same_anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273
274 /* We must garbage collect the anon_vma if it's empty */
Mel Gorman7f60c212010-05-24 14:32:18 -0700275 empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
Rik van Rielcba48b92010-08-09 17:18:38 -0700276 anon_vma_unlock(anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277
Rik van Riel76545062010-08-09 17:18:41 -0700278 if (empty) {
279 /* We no longer need the root anon_vma */
280 if (anon_vma->root != anon_vma)
281 drop_anon_vma(anon_vma->root);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 anon_vma_free(anon_vma);
Rik van Riel76545062010-08-09 17:18:41 -0700283 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284}
285
Rik van Riel5beb4932010-03-05 13:42:07 -0800286void unlink_anon_vmas(struct vm_area_struct *vma)
287{
288 struct anon_vma_chain *avc, *next;
289
Rik van Riel5c341ee2010-08-09 17:18:39 -0700290 /*
291 * Unlink each anon_vma chained to the VMA. This list is ordered
292 * from newest to oldest, ensuring the root anon_vma gets freed last.
293 */
Rik van Riel5beb4932010-03-05 13:42:07 -0800294 list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
295 anon_vma_unlink(avc);
296 list_del(&avc->same_vma);
297 anon_vma_chain_free(avc);
298 }
299}
300
Alexey Dobriyan51cc5062008-07-25 19:45:34 -0700301static void anon_vma_ctor(void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302{
Christoph Lametera35afb82007-05-16 22:10:57 -0700303 struct anon_vma *anon_vma = data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304
Christoph Lametera35afb82007-05-16 22:10:57 -0700305 spin_lock_init(&anon_vma->lock);
Mel Gorman7f60c212010-05-24 14:32:18 -0700306 anonvma_external_refcount_init(anon_vma);
Christoph Lametera35afb82007-05-16 22:10:57 -0700307 INIT_LIST_HEAD(&anon_vma->head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308}
309
310void __init anon_vma_init(void)
311{
312 anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
Paul Mundt20c2df82007-07-20 10:11:58 +0900313 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
Rik van Riel5beb4932010-03-05 13:42:07 -0800314 anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700315}
316
317/*
318 * Getting a lock on a stable anon_vma from a page off the LRU is
319 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
320 */
Namhyung Kimea4525b2010-10-26 14:22:01 -0700321struct anon_vma *__page_lock_anon_vma(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322{
Hugh Dickinsf1819422010-08-25 23:12:54 -0700323 struct anon_vma *anon_vma, *root_anon_vma;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324 unsigned long anon_mapping;
325
326 rcu_read_lock();
Hugh Dickins80e14822009-12-14 17:59:29 -0800327 anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
Hugh Dickins3ca7b3c2009-12-14 17:58:57 -0800328 if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 goto out;
330 if (!page_mapped(page))
331 goto out;
332
333 anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
Hugh Dickinsf1819422010-08-25 23:12:54 -0700334 root_anon_vma = ACCESS_ONCE(anon_vma->root);
335 spin_lock(&root_anon_vma->lock);
336
337 /*
338 * If this page is still mapped, then its anon_vma cannot have been
339 * freed. But if it has been unmapped, we have no security against
340 * the anon_vma structure being freed and reused (for another anon_vma:
341 * SLAB_DESTROY_BY_RCU guarantees that - so the spin_lock above cannot
342 * corrupt): with anon_vma_prepare() or anon_vma_fork() redirecting
343 * anon_vma->root before page_unlock_anon_vma() is called to unlock.
344 */
345 if (page_mapped(page))
346 return anon_vma;
347
348 spin_unlock(&root_anon_vma->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349out:
350 rcu_read_unlock();
Oleg Nesterov34bbd702007-02-28 20:13:49 -0800351 return NULL;
352}
353
Andi Kleen10be22d2009-09-16 11:50:04 +0200354void page_unlock_anon_vma(struct anon_vma *anon_vma)
Namhyung Kimea4525b2010-10-26 14:22:01 -0700355 __releases(&anon_vma->root->lock)
356 __releases(RCU)
Oleg Nesterov34bbd702007-02-28 20:13:49 -0800357{
Rik van Rielcba48b92010-08-09 17:18:38 -0700358 anon_vma_unlock(anon_vma);
Oleg Nesterov34bbd702007-02-28 20:13:49 -0800359 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360}
361
362/*
Lee Schermerhorn3ad33b22007-11-14 16:59:10 -0800363 * At what user virtual address is page expected in @vma?
364 * Returns virtual address or -EFAULT if page's index/offset is not
365 * within the range mapped the @vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366 */
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800367inline unsigned long
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368vma_address(struct page *page, struct vm_area_struct *vma)
369{
370 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
371 unsigned long address;
372
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +0900373 if (unlikely(is_vm_hugetlb_page(vma)))
374 pgoff = page->index << huge_page_order(page_hstate(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
376 if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
Lee Schermerhorn3ad33b22007-11-14 16:59:10 -0800377 /* page should be within @vma mapping range */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378 return -EFAULT;
379 }
380 return address;
381}
382
383/*
Huang Shijiebf89c8c2009-10-01 15:44:04 -0700384 * At what user virtual address is page expected in vma?
Naoya Horiguchiab941e02010-05-11 14:06:55 -0700385 * Caller should check the page is actually part of the vma.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 */
387unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
388{
Andrea Arcangeli21d0d442010-08-09 17:19:10 -0700389 if (PageAnon(page)) {
Hugh Dickins4829b902010-10-02 17:46:06 -0700390 struct anon_vma *page__anon_vma = page_anon_vma(page);
391 /*
392 * Note: swapoff's unuse_vma() is more efficient with this
393 * check, and needs it to match anon_vma when KSM is active.
394 */
395 if (!vma->anon_vma || !page__anon_vma ||
396 vma->anon_vma->root != page__anon_vma->root)
Andrea Arcangeli21d0d442010-08-09 17:19:10 -0700397 return -EFAULT;
398 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
Hugh Dickinsee498ed2005-11-21 21:32:18 -0800399 if (!vma->vm_file ||
400 vma->vm_file->f_mapping != page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 return -EFAULT;
402 } else
403 return -EFAULT;
404 return vma_address(page, vma);
405}
406
407/*
Nikita Danilov81b40822005-05-01 08:58:36 -0700408 * Check that @page is mapped at @address into @mm.
409 *
Nick Piggin479db0b2008-08-20 14:09:18 -0700410 * If @sync is false, page_check_address may perform a racy check to avoid
411 * the page table lock when the pte is not present (helpful when reclaiming
412 * highly shared pages).
413 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700414 * On success returns with pte mapped and locked.
Nikita Danilov81b40822005-05-01 08:58:36 -0700415 */
Namhyung Kime9a81a82010-10-26 14:22:01 -0700416pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
Nick Piggin479db0b2008-08-20 14:09:18 -0700417 unsigned long address, spinlock_t **ptlp, int sync)
Nikita Danilov81b40822005-05-01 08:58:36 -0700418{
419 pgd_t *pgd;
420 pud_t *pud;
421 pmd_t *pmd;
422 pte_t *pte;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700423 spinlock_t *ptl;
Nikita Danilov81b40822005-05-01 08:58:36 -0700424
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +0900425 if (unlikely(PageHuge(page))) {
426 pte = huge_pte_offset(mm, address);
427 ptl = &mm->page_table_lock;
428 goto check;
429 }
430
Nikita Danilov81b40822005-05-01 08:58:36 -0700431 pgd = pgd_offset(mm, address);
Hugh Dickinsc0718802005-10-29 18:16:31 -0700432 if (!pgd_present(*pgd))
433 return NULL;
434
435 pud = pud_offset(pgd, address);
436 if (!pud_present(*pud))
437 return NULL;
438
439 pmd = pmd_offset(pud, address);
440 if (!pmd_present(*pmd))
441 return NULL;
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800442 if (pmd_trans_huge(*pmd))
443 return NULL;
Hugh Dickinsc0718802005-10-29 18:16:31 -0700444
445 pte = pte_offset_map(pmd, address);
446 /* Make a quick check before getting the lock */
Nick Piggin479db0b2008-08-20 14:09:18 -0700447 if (!sync && !pte_present(*pte)) {
Hugh Dickinsc0718802005-10-29 18:16:31 -0700448 pte_unmap(pte);
449 return NULL;
Nikita Danilov81b40822005-05-01 08:58:36 -0700450 }
Hugh Dickinsc0718802005-10-29 18:16:31 -0700451
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700452 ptl = pte_lockptr(mm, pmd);
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +0900453check:
Hugh Dickinsc0718802005-10-29 18:16:31 -0700454 spin_lock(ptl);
455 if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
456 *ptlp = ptl;
457 return pte;
458 }
459 pte_unmap_unlock(pte, ptl);
460 return NULL;
Nikita Danilov81b40822005-05-01 08:58:36 -0700461}
462
Nick Pigginb291f002008-10-18 20:26:44 -0700463/**
464 * page_mapped_in_vma - check whether a page is really mapped in a VMA
465 * @page: the page to test
466 * @vma: the VMA to test
467 *
468 * Returns 1 if the page is mapped into the page tables of the VMA, 0
469 * if the page is not mapped into the page tables of this VMA. Only
470 * valid for normal file or anonymous VMAs.
471 */
Andi Kleen6a460792009-09-16 11:50:15 +0200472int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
Nick Pigginb291f002008-10-18 20:26:44 -0700473{
474 unsigned long address;
475 pte_t *pte;
476 spinlock_t *ptl;
477
478 address = vma_address(page, vma);
479 if (address == -EFAULT) /* out of vma range */
480 return 0;
481 pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
482 if (!pte) /* the page is not in this mm */
483 return 0;
484 pte_unmap_unlock(pte, ptl);
485
486 return 1;
487}
488
Nikita Danilov81b40822005-05-01 08:58:36 -0700489/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 * Subfunctions of page_referenced: page_referenced_one called
491 * repeatedly from either page_referenced_anon or page_referenced_file.
492 */
Hugh Dickins5ad64682009-12-14 17:59:24 -0800493int page_referenced_one(struct page *page, struct vm_area_struct *vma,
494 unsigned long address, unsigned int *mapcount,
495 unsigned long *vm_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700496{
497 struct mm_struct *mm = vma->vm_mm;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 int referenced = 0;
499
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800500 if (unlikely(PageTransHuge(page))) {
501 pmd_t *pmd;
502
503 spin_lock(&mm->page_table_lock);
Andrea Arcangeli2da28bf2011-03-11 14:58:29 -0800504 /*
505 * rmap might return false positives; we must filter
506 * these out using page_check_address_pmd().
507 */
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800508 pmd = page_check_address_pmd(page, mm, address,
509 PAGE_CHECK_ADDRESS_PMD_FLAG);
Andrea Arcangeli2da28bf2011-03-11 14:58:29 -0800510 if (!pmd) {
511 spin_unlock(&mm->page_table_lock);
512 goto out;
513 }
514
515 if (vma->vm_flags & VM_LOCKED) {
516 spin_unlock(&mm->page_table_lock);
517 *mapcount = 0; /* break early from loop */
518 *vm_flags |= VM_LOCKED;
519 goto out;
520 }
521
522 /* go ahead even if the pmd is pmd_trans_splitting() */
523 if (pmdp_clear_flush_young_notify(vma, address, pmd))
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800524 referenced++;
525 spin_unlock(&mm->page_table_lock);
526 } else {
527 pte_t *pte;
528 spinlock_t *ptl;
529
Andrea Arcangeli2da28bf2011-03-11 14:58:29 -0800530 /*
531 * rmap might return false positives; we must filter
532 * these out using page_check_address().
533 */
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800534 pte = page_check_address(page, mm, address, &ptl, 0);
535 if (!pte)
536 goto out;
537
Andrea Arcangeli2da28bf2011-03-11 14:58:29 -0800538 if (vma->vm_flags & VM_LOCKED) {
539 pte_unmap_unlock(pte, ptl);
540 *mapcount = 0; /* break early from loop */
541 *vm_flags |= VM_LOCKED;
542 goto out;
543 }
544
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -0800545 if (ptep_clear_flush_young_notify(vma, address, pte)) {
546 /*
547 * Don't treat a reference through a sequentially read
548 * mapping as such. If the page has been used in
549 * another mapping, we will catch it; if this other
550 * mapping is already gone, the unmap path will have
551 * set PG_referenced or activated the page.
552 */
553 if (likely(!VM_SequentialReadHint(vma)))
554 referenced++;
555 }
556 pte_unmap_unlock(pte, ptl);
557 }
558
Andrea Arcangeli2da28bf2011-03-11 14:58:29 -0800559 /* Pretend the page is referenced if the task has the
560 swap token and is in the middle of a page fault. */
561 if (mm != current->mm && has_swap_token(mm) &&
562 rwsem_is_locked(&mm->mmap_sem))
563 referenced++;
564
Hugh Dickinsc0718802005-10-29 18:16:31 -0700565 (*mapcount)--;
Huang Shijie273f0472009-12-14 17:58:51 -0800566
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700567 if (referenced)
568 *vm_flags |= vma->vm_flags;
Huang Shijie273f0472009-12-14 17:58:51 -0800569out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700570 return referenced;
571}
572
Balbir Singhbed71612008-02-07 00:14:01 -0800573static int page_referenced_anon(struct page *page,
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700574 struct mem_cgroup *mem_cont,
575 unsigned long *vm_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576{
577 unsigned int mapcount;
578 struct anon_vma *anon_vma;
Rik van Riel5beb4932010-03-05 13:42:07 -0800579 struct anon_vma_chain *avc;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580 int referenced = 0;
581
582 anon_vma = page_lock_anon_vma(page);
583 if (!anon_vma)
584 return referenced;
585
586 mapcount = page_mapcount(page);
Rik van Riel5beb4932010-03-05 13:42:07 -0800587 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
588 struct vm_area_struct *vma = avc->vma;
Hugh Dickins1cb17292009-12-14 17:59:01 -0800589 unsigned long address = vma_address(page, vma);
590 if (address == -EFAULT)
591 continue;
Balbir Singhbed71612008-02-07 00:14:01 -0800592 /*
593 * If we are reclaiming on behalf of a cgroup, skip
594 * counting on behalf of references from different
595 * cgroups
596 */
Hugh Dickinsbd845e32008-03-04 14:29:01 -0800597 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
Balbir Singhbed71612008-02-07 00:14:01 -0800598 continue;
Hugh Dickins1cb17292009-12-14 17:59:01 -0800599 referenced += page_referenced_one(page, vma, address,
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700600 &mapcount, vm_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 if (!mapcount)
602 break;
603 }
Oleg Nesterov34bbd702007-02-28 20:13:49 -0800604
605 page_unlock_anon_vma(anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700606 return referenced;
607}
608
609/**
610 * page_referenced_file - referenced check for object-based rmap
611 * @page: the page we're checking references on.
Randy Dunlap43d8eac2008-03-19 17:00:43 -0700612 * @mem_cont: target memory controller
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700613 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614 *
615 * For an object-based mapped page, find all the places it is mapped and
616 * check/clear the referenced flag. This is done by following the page->mapping
617 * pointer, then walking the chain of vmas it holds. It returns the number
618 * of references it found.
619 *
620 * This function is only called from page_referenced for object-based pages.
621 */
Balbir Singhbed71612008-02-07 00:14:01 -0800622static int page_referenced_file(struct page *page,
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700623 struct mem_cgroup *mem_cont,
624 unsigned long *vm_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700625{
626 unsigned int mapcount;
627 struct address_space *mapping = page->mapping;
628 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
629 struct vm_area_struct *vma;
630 struct prio_tree_iter iter;
631 int referenced = 0;
632
633 /*
634 * The caller's checks on page->mapping and !PageAnon have made
635 * sure that this is a file page: the check for page->mapping
636 * excludes the case just before it gets set on an anon page.
637 */
638 BUG_ON(PageAnon(page));
639
640 /*
641 * The page lock not only makes sure that page->mapping cannot
642 * suddenly be NULLified by truncation, it makes sure that the
643 * structure at mapping cannot be freed and reused yet,
644 * so we can safely take mapping->i_mmap_lock.
645 */
646 BUG_ON(!PageLocked(page));
647
648 spin_lock(&mapping->i_mmap_lock);
649
650 /*
651 * i_mmap_lock does not stabilize mapcount at all, but mapcount
652 * is more likely to be accurate if we note it after spinning.
653 */
654 mapcount = page_mapcount(page);
655
656 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
Hugh Dickins1cb17292009-12-14 17:59:01 -0800657 unsigned long address = vma_address(page, vma);
658 if (address == -EFAULT)
659 continue;
Balbir Singhbed71612008-02-07 00:14:01 -0800660 /*
661 * If we are reclaiming on behalf of a cgroup, skip
662 * counting on behalf of references from different
663 * cgroups
664 */
Hugh Dickinsbd845e32008-03-04 14:29:01 -0800665 if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
Balbir Singhbed71612008-02-07 00:14:01 -0800666 continue;
Hugh Dickins1cb17292009-12-14 17:59:01 -0800667 referenced += page_referenced_one(page, vma, address,
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700668 &mapcount, vm_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669 if (!mapcount)
670 break;
671 }
672
673 spin_unlock(&mapping->i_mmap_lock);
674 return referenced;
675}
676
677/**
678 * page_referenced - test if the page was referenced
679 * @page: the page to test
680 * @is_locked: caller holds lock on the page
Randy Dunlap43d8eac2008-03-19 17:00:43 -0700681 * @mem_cont: target memory controller
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700682 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683 *
684 * Quick test_and_clear_referenced for all mappings to a page,
685 * returns the number of ptes which referenced the page.
686 */
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700687int page_referenced(struct page *page,
688 int is_locked,
689 struct mem_cgroup *mem_cont,
690 unsigned long *vm_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691{
692 int referenced = 0;
Hugh Dickins5ad64682009-12-14 17:59:24 -0800693 int we_locked = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700695 *vm_flags = 0;
Hugh Dickins3ca7b3c2009-12-14 17:58:57 -0800696 if (page_mapped(page) && page_rmapping(page)) {
Hugh Dickins5ad64682009-12-14 17:59:24 -0800697 if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
698 we_locked = trylock_page(page);
699 if (!we_locked) {
700 referenced++;
701 goto out;
702 }
703 }
704 if (unlikely(PageKsm(page)))
705 referenced += page_referenced_ksm(page, mem_cont,
706 vm_flags);
707 else if (PageAnon(page))
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700708 referenced += page_referenced_anon(page, mem_cont,
709 vm_flags);
Hugh Dickins5ad64682009-12-14 17:59:24 -0800710 else if (page->mapping)
Wu Fengguang6fe6b7e2009-06-16 15:33:05 -0700711 referenced += page_referenced_file(page, mem_cont,
712 vm_flags);
Hugh Dickins5ad64682009-12-14 17:59:24 -0800713 if (we_locked)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700714 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715 }
Hugh Dickins5ad64682009-12-14 17:59:24 -0800716out:
Christian Borntraeger5b7baf02008-03-25 18:47:12 +0100717 if (page_test_and_clear_young(page))
718 referenced++;
719
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720 return referenced;
721}
722
Hugh Dickins1cb17292009-12-14 17:59:01 -0800723static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
724 unsigned long address)
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700725{
726 struct mm_struct *mm = vma->vm_mm;
Peter Zijlstrac2fda5f2006-12-22 14:25:52 +0100727 pte_t *pte;
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700728 spinlock_t *ptl;
729 int ret = 0;
730
Nick Piggin479db0b2008-08-20 14:09:18 -0700731 pte = page_check_address(page, mm, address, &ptl, 1);
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700732 if (!pte)
733 goto out;
734
Peter Zijlstrac2fda5f2006-12-22 14:25:52 +0100735 if (pte_dirty(*pte) || pte_write(*pte)) {
736 pte_t entry;
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700737
Peter Zijlstrac2fda5f2006-12-22 14:25:52 +0100738 flush_cache_page(vma, address, pte_pfn(*pte));
Andrea Arcangelicddb8a52008-07-28 15:46:29 -0700739 entry = ptep_clear_flush_notify(vma, address, pte);
Peter Zijlstrac2fda5f2006-12-22 14:25:52 +0100740 entry = pte_wrprotect(entry);
741 entry = pte_mkclean(entry);
Al Virod6e88e62006-12-29 16:48:35 -0800742 set_pte_at(mm, address, pte, entry);
Peter Zijlstrac2fda5f2006-12-22 14:25:52 +0100743 ret = 1;
744 }
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700745
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700746 pte_unmap_unlock(pte, ptl);
747out:
748 return ret;
749}
750
751static int page_mkclean_file(struct address_space *mapping, struct page *page)
752{
753 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
754 struct vm_area_struct *vma;
755 struct prio_tree_iter iter;
756 int ret = 0;
757
758 BUG_ON(PageAnon(page));
759
760 spin_lock(&mapping->i_mmap_lock);
761 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
Hugh Dickins1cb17292009-12-14 17:59:01 -0800762 if (vma->vm_flags & VM_SHARED) {
763 unsigned long address = vma_address(page, vma);
764 if (address == -EFAULT)
765 continue;
766 ret += page_mkclean_one(page, vma, address);
767 }
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700768 }
769 spin_unlock(&mapping->i_mmap_lock);
770 return ret;
771}
772
773int page_mkclean(struct page *page)
774{
775 int ret = 0;
776
777 BUG_ON(!PageLocked(page));
778
779 if (page_mapped(page)) {
780 struct address_space *mapping = page_mapping(page);
Christian Borntraegerce7e9fa2007-11-20 11:13:36 +0100781 if (mapping) {
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700782 ret = page_mkclean_file(mapping, page);
Christian Borntraegerce7e9fa2007-11-20 11:13:36 +0100783 if (page_test_dirty(page)) {
Martin Schwidefskye2b8d7a2010-10-25 16:10:14 +0200784 page_clear_dirty(page, 1);
Christian Borntraegerce7e9fa2007-11-20 11:13:36 +0100785 ret = 1;
786 }
Martin Schwidefsky6c210482007-04-27 16:01:57 +0200787 }
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700788 }
789
790 return ret;
791}
Jaya Kumar60b59be2007-05-08 00:37:37 -0700792EXPORT_SYMBOL_GPL(page_mkclean);
Peter Zijlstrad08b3852006-09-25 23:30:57 -0700793
Linus Torvalds1da177e2005-04-16 15:20:36 -0700794/**
Rik van Rielc44b6742010-03-05 13:42:09 -0800795 * page_move_anon_rmap - move a page to our anon_vma
796 * @page: the page to move to our anon_vma
797 * @vma: the vma the page belongs to
798 * @address: the user virtual address mapped
799 *
800 * When a page belongs exclusively to one process after a COW event,
801 * that page can be moved into the anon_vma that belongs to just that
802 * process, so the rmap code will not search the parent or sibling
803 * processes.
804 */
805void page_move_anon_rmap(struct page *page,
806 struct vm_area_struct *vma, unsigned long address)
807{
808 struct anon_vma *anon_vma = vma->anon_vma;
809
810 VM_BUG_ON(!PageLocked(page));
811 VM_BUG_ON(!anon_vma);
812 VM_BUG_ON(page->index != linear_page_index(vma, address));
813
814 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
815 page->mapping = (struct address_space *) anon_vma;
816}
817
818/**
Andi Kleen4e1c1972010-09-22 12:43:56 +0200819 * __page_set_anon_rmap - set up new anonymous rmap
820 * @page: Page to add to rmap
821 * @vma: VM area to add page to.
822 * @address: User virtual address of the mapping
Rik van Riele8a03fe2010-04-14 17:59:28 -0400823 * @exclusive: the page is exclusively owned by the current process
Nick Piggin9617d952006-01-06 00:11:12 -0800824 */
825static void __page_set_anon_rmap(struct page *page,
Rik van Riele8a03fe2010-04-14 17:59:28 -0400826 struct vm_area_struct *vma, unsigned long address, int exclusive)
Nick Piggin9617d952006-01-06 00:11:12 -0800827{
Rik van Riele8a03fe2010-04-14 17:59:28 -0400828 struct anon_vma *anon_vma = vma->anon_vma;
Nick Piggin9617d952006-01-06 00:11:12 -0800829
Rik van Riele8a03fe2010-04-14 17:59:28 -0400830 BUG_ON(!anon_vma);
Linus Torvaldsea900022010-04-12 12:44:29 -0700831
Andi Kleen4e1c1972010-09-22 12:43:56 +0200832 if (PageAnon(page))
833 return;
834
Linus Torvaldsea900022010-04-12 12:44:29 -0700835 /*
Rik van Riele8a03fe2010-04-14 17:59:28 -0400836 * If the page isn't exclusively mapped into this vma,
837 * we must use the _oldest_ possible anon_vma for the
838 * page mapping!
Linus Torvaldsea900022010-04-12 12:44:29 -0700839 */
Andi Kleen4e1c1972010-09-22 12:43:56 +0200840 if (!exclusive)
Andrea Arcangeli288468c2010-08-09 17:19:09 -0700841 anon_vma = anon_vma->root;
Linus Torvaldsea900022010-04-12 12:44:29 -0700842
Nick Piggin9617d952006-01-06 00:11:12 -0800843 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
844 page->mapping = (struct address_space *) anon_vma;
Nick Piggin9617d952006-01-06 00:11:12 -0800845 page->index = linear_page_index(vma, address);
Nick Piggin9617d952006-01-06 00:11:12 -0800846}
847
848/**
Randy Dunlap43d8eac2008-03-19 17:00:43 -0700849 * __page_check_anon_rmap - sanity check anonymous rmap addition
Nick Pigginc97a9e12007-05-16 22:11:21 -0700850 * @page: the page to add the mapping to
851 * @vma: the vm area in which the mapping is added
852 * @address: the user virtual address mapped
853 */
854static void __page_check_anon_rmap(struct page *page,
855 struct vm_area_struct *vma, unsigned long address)
856{
857#ifdef CONFIG_DEBUG_VM
858 /*
859 * The page's anon-rmap details (mapping and index) are guaranteed to
860 * be set up correctly at this point.
861 *
862 * We have exclusion against page_add_anon_rmap because the caller
863 * always holds the page locked, except if called from page_dup_rmap,
864 * in which case the page is already known to be setup.
865 *
866 * We have exclusion against page_add_new_anon_rmap because those pages
867 * are initially only visible via the pagetables, and the pte is locked
868 * over the call to page_add_new_anon_rmap.
869 */
Andrea Arcangeli44ab57a2010-08-09 17:19:10 -0700870 BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
Nick Pigginc97a9e12007-05-16 22:11:21 -0700871 BUG_ON(page->index != linear_page_index(vma, address));
872#endif
873}
874
875/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 * page_add_anon_rmap - add pte mapping to an anonymous page
877 * @page: the page to add the mapping to
878 * @vma: the vm area in which the mapping is added
879 * @address: the user virtual address mapped
880 *
Hugh Dickins5ad64682009-12-14 17:59:24 -0800881 * The caller needs to hold the pte lock, and the page must be locked in
Hugh Dickins80e14822009-12-14 17:59:29 -0800882 * the anon_vma case: to serialize mapping,index checking after setting,
883 * and to ensure that PageAnon is not being upgraded racily to PageKsm
884 * (but PageKsm is never downgraded to PageAnon).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700885 */
886void page_add_anon_rmap(struct page *page,
887 struct vm_area_struct *vma, unsigned long address)
888{
Rik van Rielad8c2ee2010-08-09 17:19:48 -0700889 do_page_add_anon_rmap(page, vma, address, 0);
890}
891
892/*
893 * Special version of the above for do_swap_page, which often runs
894 * into pages that are exclusively owned by the current process.
895 * Everybody else should continue to use page_add_anon_rmap above.
896 */
897void do_page_add_anon_rmap(struct page *page,
898 struct vm_area_struct *vma, unsigned long address, int exclusive)
899{
Hugh Dickins5ad64682009-12-14 17:59:24 -0800900 int first = atomic_inc_and_test(&page->_mapcount);
Andrea Arcangeli79134172011-01-13 15:46:58 -0800901 if (first) {
902 if (!PageTransHuge(page))
903 __inc_zone_page_state(page, NR_ANON_PAGES);
904 else
905 __inc_zone_page_state(page,
906 NR_ANON_TRANSPARENT_HUGEPAGES);
907 }
Hugh Dickins5ad64682009-12-14 17:59:24 -0800908 if (unlikely(PageKsm(page)))
909 return;
910
Nick Pigginc97a9e12007-05-16 22:11:21 -0700911 VM_BUG_ON(!PageLocked(page));
912 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
Hugh Dickins5ad64682009-12-14 17:59:24 -0800913 if (first)
Rik van Rielad8c2ee2010-08-09 17:19:48 -0700914 __page_set_anon_rmap(page, vma, address, exclusive);
KAMEZAWA Hiroyuki69029cd2008-07-25 01:47:14 -0700915 else
Nick Pigginc97a9e12007-05-16 22:11:21 -0700916 __page_check_anon_rmap(page, vma, address);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917}
918
Randy Dunlap43d8eac2008-03-19 17:00:43 -0700919/**
Nick Piggin9617d952006-01-06 00:11:12 -0800920 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
921 * @page: the page to add the mapping to
922 * @vma: the vm area in which the mapping is added
923 * @address: the user virtual address mapped
924 *
925 * Same as page_add_anon_rmap but must only be called on *new* pages.
926 * This means the inc-and-test can be bypassed.
Nick Pigginc97a9e12007-05-16 22:11:21 -0700927 * Page does not have to be locked.
Nick Piggin9617d952006-01-06 00:11:12 -0800928 */
929void page_add_new_anon_rmap(struct page *page,
930 struct vm_area_struct *vma, unsigned long address)
931{
Hugh Dickinsb5934c52009-01-06 14:39:25 -0800932 VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
Hugh Dickinscbf84b72009-01-06 14:39:27 -0800933 SetPageSwapBacked(page);
934 atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
Andrea Arcangeli79134172011-01-13 15:46:58 -0800935 if (!PageTransHuge(page))
936 __inc_zone_page_state(page, NR_ANON_PAGES);
937 else
938 __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
Rik van Riele8a03fe2010-04-14 17:59:28 -0400939 __page_set_anon_rmap(page, vma, address, 1);
Hugh Dickinsb5934c52009-01-06 14:39:25 -0800940 if (page_evictable(page, vma))
Hugh Dickinscbf84b72009-01-06 14:39:27 -0800941 lru_cache_add_lru(page, LRU_ACTIVE_ANON);
Hugh Dickinsb5934c52009-01-06 14:39:25 -0800942 else
943 add_page_to_unevictable_list(page);
Nick Piggin9617d952006-01-06 00:11:12 -0800944}
945
Linus Torvalds1da177e2005-04-16 15:20:36 -0700946/**
947 * page_add_file_rmap - add pte mapping to a file page
948 * @page: the page to add the mapping to
949 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700950 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951 */
952void page_add_file_rmap(struct page *page)
953{
Balbir Singhd69b0422009-06-17 16:26:34 -0700954 if (atomic_inc_and_test(&page->_mapcount)) {
Christoph Lameter65ba55f2006-06-30 01:55:34 -0700955 __inc_zone_page_state(page, NR_FILE_MAPPED);
Greg Thelen2a7106f2011-01-13 15:47:37 -0800956 mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED);
Balbir Singhd69b0422009-06-17 16:26:34 -0700957 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958}
959
960/**
961 * page_remove_rmap - take down pte mapping from a page
962 * @page: page to remove mapping from
963 *
Hugh Dickinsb8072f02005-10-29 18:16:41 -0700964 * The caller needs to hold the pte lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700965 */
Hugh Dickinsedc315f2009-01-06 14:40:11 -0800966void page_remove_rmap(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700967{
KOSAKI Motohirob904dcf2009-09-21 17:01:28 -0700968 /* page still mapped by someone else? */
969 if (!atomic_add_negative(-1, &page->_mapcount))
970 return;
971
972 /*
973 * Now that the last pte has gone, s390 must transfer dirty
974 * flag from storage key to struct page. We can usually skip
975 * this if the page is anon, so about to be freed; but perhaps
976 * not if it's in swapcache - there might be another pte slot
977 * containing the swap entry, but page not yet written to swap.
978 */
979 if ((!PageAnon(page) || PageSwapCache(page)) && page_test_dirty(page)) {
Martin Schwidefskye2b8d7a2010-10-25 16:10:14 +0200980 page_clear_dirty(page, 1);
KOSAKI Motohirob904dcf2009-09-21 17:01:28 -0700981 set_page_dirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700982 }
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +0900983 /*
984 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
985 * and not charged by memcg for now.
986 */
987 if (unlikely(PageHuge(page)))
988 return;
KOSAKI Motohirob904dcf2009-09-21 17:01:28 -0700989 if (PageAnon(page)) {
990 mem_cgroup_uncharge_page(page);
Andrea Arcangeli79134172011-01-13 15:46:58 -0800991 if (!PageTransHuge(page))
992 __dec_zone_page_state(page, NR_ANON_PAGES);
993 else
994 __dec_zone_page_state(page,
995 NR_ANON_TRANSPARENT_HUGEPAGES);
KOSAKI Motohirob904dcf2009-09-21 17:01:28 -0700996 } else {
997 __dec_zone_page_state(page, NR_FILE_MAPPED);
Greg Thelen2a7106f2011-01-13 15:47:37 -0800998 mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED);
KOSAKI Motohirob904dcf2009-09-21 17:01:28 -0700999 }
KOSAKI Motohirob904dcf2009-09-21 17:01:28 -07001000 /*
1001 * It would be tidy to reset the PageAnon mapping here,
1002 * but that might overwrite a racing page_add_anon_rmap
1003 * which increments mapcount after us but sets mapping
1004 * before us: so leave the reset to free_hot_cold_page,
1005 * and remember that it's only reliable while mapped.
1006 * Leaving it set also helps swapoff to reinstate ptes
1007 * faster for those pages still in swapcache.
1008 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009}
1010
1011/*
1012 * Subfunctions of try_to_unmap: try_to_unmap_one called
1013 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
1014 */
Hugh Dickins5ad64682009-12-14 17:59:24 -08001015int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1016 unsigned long address, enum ttu_flags flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017{
1018 struct mm_struct *mm = vma->vm_mm;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019 pte_t *pte;
1020 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -07001021 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 int ret = SWAP_AGAIN;
1023
Nick Piggin479db0b2008-08-20 14:09:18 -07001024 pte = page_check_address(page, mm, address, &ptl, 0);
Hugh Dickinsc0718802005-10-29 18:16:31 -07001025 if (!pte)
Nikita Danilov81b40822005-05-01 08:58:36 -07001026 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001027
1028 /*
1029 * If the page is mlock()d, we cannot swap it out.
1030 * If it's recently referenced (perhaps page_referenced
1031 * skipped over this mm) then we should reactivate it.
1032 */
Andi Kleen14fa31b2009-09-16 11:50:10 +02001033 if (!(flags & TTU_IGNORE_MLOCK)) {
KOSAKI Motohirocaed0f42009-12-14 17:59:45 -08001034 if (vma->vm_flags & VM_LOCKED)
1035 goto out_mlock;
1036
Hugh Dickinsaf8e3352009-12-14 17:58:59 -08001037 if (TTU_ACTION(flags) == TTU_MUNLOCK)
Hugh Dickins53f79ac2009-12-14 17:58:58 -08001038 goto out_unmap;
Andi Kleen14fa31b2009-09-16 11:50:10 +02001039 }
1040 if (!(flags & TTU_IGNORE_ACCESS)) {
Nick Pigginb291f002008-10-18 20:26:44 -07001041 if (ptep_clear_flush_young_notify(vma, address, pte)) {
1042 ret = SWAP_FAIL;
1043 goto out_unmap;
1044 }
1045 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047 /* Nuke the page table entry. */
1048 flush_cache_page(vma, address, page_to_pfn(page));
Andrea Arcangelicddb8a52008-07-28 15:46:29 -07001049 pteval = ptep_clear_flush_notify(vma, address, pte);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050
1051 /* Move the dirty bit to the physical page now the pte is gone. */
1052 if (pte_dirty(pteval))
1053 set_page_dirty(page);
1054
Hugh Dickins365e9c872005-10-29 18:16:18 -07001055 /* Update high watermark before we lower rss */
1056 update_hiwater_rss(mm);
1057
Andi Kleen888b9f72009-09-16 11:50:11 +02001058 if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1059 if (PageAnon(page))
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -08001060 dec_mm_counter(mm, MM_ANONPAGES);
Andi Kleen888b9f72009-09-16 11:50:11 +02001061 else
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -08001062 dec_mm_counter(mm, MM_FILEPAGES);
Andi Kleen888b9f72009-09-16 11:50:11 +02001063 set_pte_at(mm, address, pte,
1064 swp_entry_to_pte(make_hwpoison_entry(page)));
1065 } else if (PageAnon(page)) {
Hugh Dickins4c21e2f2005-10-29 18:16:40 -07001066 swp_entry_t entry = { .val = page_private(page) };
Christoph Lameter06972122006-06-23 02:03:35 -07001067
1068 if (PageSwapCache(page)) {
1069 /*
1070 * Store the swap location in the pte.
1071 * See handle_pte_fault() ...
1072 */
Hugh Dickins570a3352009-12-14 17:58:46 -08001073 if (swap_duplicate(entry) < 0) {
1074 set_pte_at(mm, address, pte, pteval);
1075 ret = SWAP_FAIL;
1076 goto out_unmap;
1077 }
Christoph Lameter06972122006-06-23 02:03:35 -07001078 if (list_empty(&mm->mmlist)) {
1079 spin_lock(&mmlist_lock);
1080 if (list_empty(&mm->mmlist))
1081 list_add(&mm->mmlist, &init_mm.mmlist);
1082 spin_unlock(&mmlist_lock);
1083 }
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -08001084 dec_mm_counter(mm, MM_ANONPAGES);
KAMEZAWA Hiroyukib084d432010-03-05 13:41:42 -08001085 inc_mm_counter(mm, MM_SWAPENTS);
KOSAKI Motohiro64cdd542009-01-06 14:39:16 -08001086 } else if (PAGE_MIGRATION) {
Christoph Lameter06972122006-06-23 02:03:35 -07001087 /*
1088 * Store the pfn of the page in a special migration
1089 * pte. do_swap_page() will wait until the migration
1090 * pte is removed and then restart fault handling.
1091 */
Andi Kleen14fa31b2009-09-16 11:50:10 +02001092 BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
Christoph Lameter06972122006-06-23 02:03:35 -07001093 entry = make_migration_entry(page, pte_write(pteval));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094 }
1095 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1096 BUG_ON(pte_file(*pte));
Andi Kleen14fa31b2009-09-16 11:50:10 +02001097 } else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) {
Christoph Lameter04e62a22006-06-23 02:03:38 -07001098 /* Establish migration entry for a file page */
1099 swp_entry_t entry;
1100 entry = make_migration_entry(page, pte_write(pteval));
1101 set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1102 } else
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -08001103 dec_mm_counter(mm, MM_FILEPAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104
Hugh Dickinsedc315f2009-01-06 14:40:11 -08001105 page_remove_rmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 page_cache_release(page);
1107
1108out_unmap:
Hugh Dickinsc0718802005-10-29 18:16:31 -07001109 pte_unmap_unlock(pte, ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001110out:
1111 return ret;
KOSAKI Motohirocaed0f42009-12-14 17:59:45 -08001112
1113out_mlock:
1114 pte_unmap_unlock(pte, ptl);
1115
1116
1117 /*
1118 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1119 * unstable result and race. Plus, We can't wait here because
1120 * we now hold anon_vma->lock or mapping->i_mmap_lock.
1121 * if trylock failed, the page remain in evictable lru and later
1122 * vmscan could retry to move the page to unevictable lru if the
1123 * page is actually mlocked.
1124 */
1125 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1126 if (vma->vm_flags & VM_LOCKED) {
1127 mlock_vma_page(page);
1128 ret = SWAP_MLOCK;
1129 }
1130 up_read(&vma->vm_mm->mmap_sem);
1131 }
1132 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133}
1134
1135/*
1136 * objrmap doesn't work for nonlinear VMAs because the assumption that
1137 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
1138 * Consequently, given a particular page and its ->index, we cannot locate the
1139 * ptes which are mapping that page without an exhaustive linear search.
1140 *
1141 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
1142 * maps the file to which the target page belongs. The ->vm_private_data field
1143 * holds the current cursor into that scan. Successive searches will circulate
1144 * around the vma's virtual address space.
1145 *
1146 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
1147 * more scanning pressure is placed against them as well. Eventually pages
1148 * will become fully unmapped and are eligible for eviction.
1149 *
1150 * For very sparsely populated VMAs this is a little inefficient - chances are
1151 * there there won't be many ptes located within the scan cluster. In this case
1152 * maybe we could scan further - to the end of the pte page, perhaps.
Nick Pigginb291f002008-10-18 20:26:44 -07001153 *
1154 * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
1155 * acquire it without blocking. If vma locked, mlock the pages in the cluster,
1156 * rather than unmapping them. If we encounter the "check_page" that vmscan is
1157 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 */
1159#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
1160#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
1161
Nick Pigginb291f002008-10-18 20:26:44 -07001162static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1163 struct vm_area_struct *vma, struct page *check_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164{
1165 struct mm_struct *mm = vma->vm_mm;
1166 pgd_t *pgd;
1167 pud_t *pud;
1168 pmd_t *pmd;
Hugh Dickinsc0718802005-10-29 18:16:31 -07001169 pte_t *pte;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 pte_t pteval;
Hugh Dickinsc0718802005-10-29 18:16:31 -07001171 spinlock_t *ptl;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172 struct page *page;
1173 unsigned long address;
1174 unsigned long end;
Nick Pigginb291f002008-10-18 20:26:44 -07001175 int ret = SWAP_AGAIN;
1176 int locked_vma = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001177
Linus Torvalds1da177e2005-04-16 15:20:36 -07001178 address = (vma->vm_start + cursor) & CLUSTER_MASK;
1179 end = address + CLUSTER_SIZE;
1180 if (address < vma->vm_start)
1181 address = vma->vm_start;
1182 if (end > vma->vm_end)
1183 end = vma->vm_end;
1184
1185 pgd = pgd_offset(mm, address);
1186 if (!pgd_present(*pgd))
Nick Pigginb291f002008-10-18 20:26:44 -07001187 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188
1189 pud = pud_offset(pgd, address);
1190 if (!pud_present(*pud))
Nick Pigginb291f002008-10-18 20:26:44 -07001191 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001192
1193 pmd = pmd_offset(pud, address);
1194 if (!pmd_present(*pmd))
Nick Pigginb291f002008-10-18 20:26:44 -07001195 return ret;
1196
1197 /*
Hugh Dickinsaf8e3352009-12-14 17:58:59 -08001198 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
Nick Pigginb291f002008-10-18 20:26:44 -07001199 * keep the sem while scanning the cluster for mlocking pages.
1200 */
Hugh Dickinsaf8e3352009-12-14 17:58:59 -08001201 if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
Nick Pigginb291f002008-10-18 20:26:44 -07001202 locked_vma = (vma->vm_flags & VM_LOCKED);
1203 if (!locked_vma)
1204 up_read(&vma->vm_mm->mmap_sem); /* don't need it */
1205 }
Hugh Dickinsc0718802005-10-29 18:16:31 -07001206
1207 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208
Hugh Dickins365e9c872005-10-29 18:16:18 -07001209 /* Update high watermark before we lower rss */
1210 update_hiwater_rss(mm);
1211
Hugh Dickinsc0718802005-10-29 18:16:31 -07001212 for (; address < end; pte++, address += PAGE_SIZE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001213 if (!pte_present(*pte))
1214 continue;
Linus Torvalds6aab3412005-11-28 14:34:23 -08001215 page = vm_normal_page(vma, address, *pte);
1216 BUG_ON(!page || PageAnon(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001217
Nick Pigginb291f002008-10-18 20:26:44 -07001218 if (locked_vma) {
1219 mlock_vma_page(page); /* no-op if already mlocked */
1220 if (page == check_page)
1221 ret = SWAP_MLOCK;
1222 continue; /* don't unmap */
1223 }
1224
Andrea Arcangelicddb8a52008-07-28 15:46:29 -07001225 if (ptep_clear_flush_young_notify(vma, address, pte))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226 continue;
1227
1228 /* Nuke the page table entry. */
Ben Collinseca35132005-11-29 11:45:26 -08001229 flush_cache_page(vma, address, pte_pfn(*pte));
Andrea Arcangelicddb8a52008-07-28 15:46:29 -07001230 pteval = ptep_clear_flush_notify(vma, address, pte);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231
1232 /* If nonlinear, store the file page offset in the pte. */
1233 if (page->index != linear_page_index(vma, address))
1234 set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
1235
1236 /* Move the dirty bit to the physical page now the pte is gone. */
1237 if (pte_dirty(pteval))
1238 set_page_dirty(page);
1239
Hugh Dickinsedc315f2009-01-06 14:40:11 -08001240 page_remove_rmap(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241 page_cache_release(page);
KAMEZAWA Hiroyukid559db02010-03-05 13:41:39 -08001242 dec_mm_counter(mm, MM_FILEPAGES);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243 (*mapcount)--;
1244 }
Hugh Dickinsc0718802005-10-29 18:16:31 -07001245 pte_unmap_unlock(pte - 1, ptl);
Nick Pigginb291f002008-10-18 20:26:44 -07001246 if (locked_vma)
1247 up_read(&vma->vm_mm->mmap_sem);
1248 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249}
1250
Andrea Arcangeli71e3aac2011-01-13 15:46:52 -08001251bool is_vma_temporary_stack(struct vm_area_struct *vma)
Mel Gormana8bef8ff2010-05-24 14:32:24 -07001252{
1253 int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
1254
1255 if (!maybe_stack)
1256 return false;
1257
1258 if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1259 VM_STACK_INCOMPLETE_SETUP)
1260 return true;
1261
1262 return false;
1263}
1264
Nick Pigginb291f002008-10-18 20:26:44 -07001265/**
1266 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1267 * rmap method
1268 * @page: the page to unmap/unlock
Huang Shijie8051be52009-12-14 17:58:50 -08001269 * @flags: action and flags
Nick Pigginb291f002008-10-18 20:26:44 -07001270 *
1271 * Find all the mappings of a page using the mapping pointer and the vma chains
1272 * contained in the anon_vma struct it points to.
1273 *
1274 * This function is only called from try_to_unmap/try_to_munlock for
1275 * anonymous pages.
1276 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1277 * where the page was found will be held for write. So, we won't recheck
1278 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1279 * 'LOCKED.
1280 */
Andi Kleen14fa31b2009-09-16 11:50:10 +02001281static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001282{
1283 struct anon_vma *anon_vma;
Rik van Riel5beb4932010-03-05 13:42:07 -08001284 struct anon_vma_chain *avc;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001285 int ret = SWAP_AGAIN;
Nick Pigginb291f002008-10-18 20:26:44 -07001286
Linus Torvalds1da177e2005-04-16 15:20:36 -07001287 anon_vma = page_lock_anon_vma(page);
1288 if (!anon_vma)
1289 return ret;
1290
Rik van Riel5beb4932010-03-05 13:42:07 -08001291 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1292 struct vm_area_struct *vma = avc->vma;
Mel Gormana8bef8ff2010-05-24 14:32:24 -07001293 unsigned long address;
1294
1295 /*
1296 * During exec, a temporary VMA is setup and later moved.
1297 * The VMA is moved under the anon_vma lock but not the
1298 * page tables leading to a race where migration cannot
1299 * find the migration ptes. Rather than increasing the
1300 * locking requirements of exec(), migration skips
1301 * temporary VMAs until after exec() completes.
1302 */
1303 if (PAGE_MIGRATION && (flags & TTU_MIGRATION) &&
1304 is_vma_temporary_stack(vma))
1305 continue;
1306
1307 address = vma_address(page, vma);
Hugh Dickins1cb17292009-12-14 17:59:01 -08001308 if (address == -EFAULT)
1309 continue;
1310 ret = try_to_unmap_one(page, vma, address, flags);
Hugh Dickins53f79ac2009-12-14 17:58:58 -08001311 if (ret != SWAP_AGAIN || !page_mapped(page))
1312 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001313 }
Oleg Nesterov34bbd702007-02-28 20:13:49 -08001314
1315 page_unlock_anon_vma(anon_vma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316 return ret;
1317}
1318
1319/**
Nick Pigginb291f002008-10-18 20:26:44 -07001320 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1321 * @page: the page to unmap/unlock
Andi Kleen14fa31b2009-09-16 11:50:10 +02001322 * @flags: action and flags
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 *
1324 * Find all the mappings of a page using the mapping pointer and the vma chains
1325 * contained in the address_space struct it points to.
1326 *
Nick Pigginb291f002008-10-18 20:26:44 -07001327 * This function is only called from try_to_unmap/try_to_munlock for
1328 * object-based pages.
1329 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1330 * where the page was found will be held for write. So, we won't recheck
1331 * vm_flags for that VMA. That should be OK, because that vma shouldn't be
1332 * 'LOCKED.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333 */
Andi Kleen14fa31b2009-09-16 11:50:10 +02001334static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001335{
1336 struct address_space *mapping = page->mapping;
1337 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1338 struct vm_area_struct *vma;
1339 struct prio_tree_iter iter;
1340 int ret = SWAP_AGAIN;
1341 unsigned long cursor;
1342 unsigned long max_nl_cursor = 0;
1343 unsigned long max_nl_size = 0;
1344 unsigned int mapcount;
1345
1346 spin_lock(&mapping->i_mmap_lock);
1347 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
Hugh Dickins1cb17292009-12-14 17:59:01 -08001348 unsigned long address = vma_address(page, vma);
1349 if (address == -EFAULT)
1350 continue;
1351 ret = try_to_unmap_one(page, vma, address, flags);
Hugh Dickins53f79ac2009-12-14 17:58:58 -08001352 if (ret != SWAP_AGAIN || !page_mapped(page))
1353 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 }
1355
1356 if (list_empty(&mapping->i_mmap_nonlinear))
1357 goto out;
1358
Hugh Dickins53f79ac2009-12-14 17:58:58 -08001359 /*
1360 * We don't bother to try to find the munlocked page in nonlinears.
1361 * It's costly. Instead, later, page reclaim logic may call
1362 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1363 */
1364 if (TTU_ACTION(flags) == TTU_MUNLOCK)
1365 goto out;
1366
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1368 shared.vm_set.list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001369 cursor = (unsigned long) vma->vm_private_data;
1370 if (cursor > max_nl_cursor)
1371 max_nl_cursor = cursor;
1372 cursor = vma->vm_end - vma->vm_start;
1373 if (cursor > max_nl_size)
1374 max_nl_size = cursor;
1375 }
1376
Nick Pigginb291f002008-10-18 20:26:44 -07001377 if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001378 ret = SWAP_FAIL;
1379 goto out;
1380 }
1381
1382 /*
1383 * We don't try to search for this page in the nonlinear vmas,
1384 * and page_referenced wouldn't have found it anyway. Instead
1385 * just walk the nonlinear vmas trying to age and unmap some.
1386 * The mapcount of the page we came in with is irrelevant,
1387 * but even so use it as a guide to how hard we should try?
1388 */
1389 mapcount = page_mapcount(page);
1390 if (!mapcount)
1391 goto out;
1392 cond_resched_lock(&mapping->i_mmap_lock);
1393
1394 max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1395 if (max_nl_cursor == 0)
1396 max_nl_cursor = CLUSTER_SIZE;
1397
1398 do {
1399 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1400 shared.vm_set.list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401 cursor = (unsigned long) vma->vm_private_data;
Hugh Dickins839b9682005-09-03 15:54:43 -07001402 while ( cursor < max_nl_cursor &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403 cursor < vma->vm_end - vma->vm_start) {
Hugh Dickins53f79ac2009-12-14 17:58:58 -08001404 if (try_to_unmap_cluster(cursor, &mapcount,
1405 vma, page) == SWAP_MLOCK)
1406 ret = SWAP_MLOCK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 cursor += CLUSTER_SIZE;
1408 vma->vm_private_data = (void *) cursor;
1409 if ((int)mapcount <= 0)
1410 goto out;
1411 }
1412 vma->vm_private_data = (void *) max_nl_cursor;
1413 }
1414 cond_resched_lock(&mapping->i_mmap_lock);
1415 max_nl_cursor += CLUSTER_SIZE;
1416 } while (max_nl_cursor <= max_nl_size);
1417
1418 /*
1419 * Don't loop forever (perhaps all the remaining pages are
1420 * in locked vmas). Reset cursor on all unreserved nonlinear
1421 * vmas, now forgetting on which ones it had fallen behind.
1422 */
Hugh Dickins101d2be2005-11-21 21:32:16 -08001423 list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
1424 vma->vm_private_data = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425out:
1426 spin_unlock(&mapping->i_mmap_lock);
1427 return ret;
1428}
1429
1430/**
1431 * try_to_unmap - try to remove all page table mappings to a page
1432 * @page: the page to get unmapped
Andi Kleen14fa31b2009-09-16 11:50:10 +02001433 * @flags: action and flags
Linus Torvalds1da177e2005-04-16 15:20:36 -07001434 *
1435 * Tries to remove all the page table entries which are mapping this
1436 * page, used in the pageout path. Caller must hold the page lock.
1437 * Return values are:
1438 *
1439 * SWAP_SUCCESS - we succeeded in removing all mappings
1440 * SWAP_AGAIN - we missed a mapping, try again later
1441 * SWAP_FAIL - the page is unswappable
Nick Pigginb291f002008-10-18 20:26:44 -07001442 * SWAP_MLOCK - page is mlocked.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443 */
Andi Kleen14fa31b2009-09-16 11:50:10 +02001444int try_to_unmap(struct page *page, enum ttu_flags flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445{
1446 int ret;
1447
Linus Torvalds1da177e2005-04-16 15:20:36 -07001448 BUG_ON(!PageLocked(page));
Andrea Arcangeli91600e92011-01-13 15:47:16 -08001449 VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450
Hugh Dickins5ad64682009-12-14 17:59:24 -08001451 if (unlikely(PageKsm(page)))
1452 ret = try_to_unmap_ksm(page, flags);
1453 else if (PageAnon(page))
Andi Kleen14fa31b2009-09-16 11:50:10 +02001454 ret = try_to_unmap_anon(page, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001455 else
Andi Kleen14fa31b2009-09-16 11:50:10 +02001456 ret = try_to_unmap_file(page, flags);
Nick Pigginb291f002008-10-18 20:26:44 -07001457 if (ret != SWAP_MLOCK && !page_mapped(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001458 ret = SWAP_SUCCESS;
1459 return ret;
1460}
Nikita Danilov81b40822005-05-01 08:58:36 -07001461
Nick Pigginb291f002008-10-18 20:26:44 -07001462/**
1463 * try_to_munlock - try to munlock a page
1464 * @page: the page to be munlocked
1465 *
1466 * Called from munlock code. Checks all of the VMAs mapping the page
1467 * to make sure nobody else has this page mlocked. The page will be
1468 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1469 *
1470 * Return values are:
1471 *
Hugh Dickins53f79ac2009-12-14 17:58:58 -08001472 * SWAP_AGAIN - no vma is holding page mlocked, or,
Nick Pigginb291f002008-10-18 20:26:44 -07001473 * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
Hugh Dickins5ad64682009-12-14 17:59:24 -08001474 * SWAP_FAIL - page cannot be located at present
Nick Pigginb291f002008-10-18 20:26:44 -07001475 * SWAP_MLOCK - page is now mlocked.
1476 */
1477int try_to_munlock(struct page *page)
1478{
1479 VM_BUG_ON(!PageLocked(page) || PageLRU(page));
1480
Hugh Dickins5ad64682009-12-14 17:59:24 -08001481 if (unlikely(PageKsm(page)))
1482 return try_to_unmap_ksm(page, TTU_MUNLOCK);
1483 else if (PageAnon(page))
Andi Kleen14fa31b2009-09-16 11:50:10 +02001484 return try_to_unmap_anon(page, TTU_MUNLOCK);
Nick Pigginb291f002008-10-18 20:26:44 -07001485 else
Andi Kleen14fa31b2009-09-16 11:50:10 +02001486 return try_to_unmap_file(page, TTU_MUNLOCK);
Nick Pigginb291f002008-10-18 20:26:44 -07001487}
Hugh Dickinse9995ef2009-12-14 17:59:31 -08001488
Rik van Riel76545062010-08-09 17:18:41 -07001489#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
1490/*
1491 * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root
1492 * if necessary. Be careful to do all the tests under the lock. Once
1493 * we know we are the last user, nobody else can get a reference and we
1494 * can do the freeing without the lock.
1495 */
1496void drop_anon_vma(struct anon_vma *anon_vma)
1497{
Andrea Arcangeli44ab57a2010-08-09 17:19:10 -07001498 BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);
Rik van Riel76545062010-08-09 17:18:41 -07001499 if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {
1500 struct anon_vma *root = anon_vma->root;
1501 int empty = list_empty(&anon_vma->head);
1502 int last_root_user = 0;
1503 int root_empty = 0;
1504
1505 /*
1506 * The refcount on a non-root anon_vma got dropped. Drop
1507 * the refcount on the root and check if we need to free it.
1508 */
1509 if (empty && anon_vma != root) {
Andrea Arcangeli44ab57a2010-08-09 17:19:10 -07001510 BUG_ON(atomic_read(&root->external_refcount) <= 0);
Rik van Riel76545062010-08-09 17:18:41 -07001511 last_root_user = atomic_dec_and_test(&root->external_refcount);
1512 root_empty = list_empty(&root->head);
1513 }
1514 anon_vma_unlock(anon_vma);
1515
1516 if (empty) {
1517 anon_vma_free(anon_vma);
1518 if (root_empty && last_root_user)
1519 anon_vma_free(root);
1520 }
1521 }
1522}
1523#endif
1524
Hugh Dickinse9995ef2009-12-14 17:59:31 -08001525#ifdef CONFIG_MIGRATION
1526/*
1527 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1528 * Called by migrate.c to remove migration ptes, but might be used more later.
1529 */
1530static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
1531 struct vm_area_struct *, unsigned long, void *), void *arg)
1532{
1533 struct anon_vma *anon_vma;
Rik van Riel5beb4932010-03-05 13:42:07 -08001534 struct anon_vma_chain *avc;
Hugh Dickinse9995ef2009-12-14 17:59:31 -08001535 int ret = SWAP_AGAIN;
1536
1537 /*
1538 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
1539 * because that depends on page_mapped(); but not all its usages
Mel Gorman3f6c8272010-05-24 14:32:17 -07001540 * are holding mmap_sem. Users without mmap_sem are required to
1541 * take a reference count to prevent the anon_vma disappearing
Hugh Dickinse9995ef2009-12-14 17:59:31 -08001542 */
1543 anon_vma = page_anon_vma(page);
1544 if (!anon_vma)
1545 return ret;
Rik van Rielcba48b92010-08-09 17:18:38 -07001546 anon_vma_lock(anon_vma);
Rik van Riel5beb4932010-03-05 13:42:07 -08001547 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1548 struct vm_area_struct *vma = avc->vma;
Hugh Dickinse9995ef2009-12-14 17:59:31 -08001549 unsigned long address = vma_address(page, vma);
1550 if (address == -EFAULT)
1551 continue;
1552 ret = rmap_one(page, vma, address, arg);
1553 if (ret != SWAP_AGAIN)
1554 break;
1555 }
Rik van Rielcba48b92010-08-09 17:18:38 -07001556 anon_vma_unlock(anon_vma);
Hugh Dickinse9995ef2009-12-14 17:59:31 -08001557 return ret;
1558}
1559
1560static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
1561 struct vm_area_struct *, unsigned long, void *), void *arg)
1562{
1563 struct address_space *mapping = page->mapping;
1564 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1565 struct vm_area_struct *vma;
1566 struct prio_tree_iter iter;
1567 int ret = SWAP_AGAIN;
1568
1569 if (!mapping)
1570 return ret;
1571 spin_lock(&mapping->i_mmap_lock);
1572 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1573 unsigned long address = vma_address(page, vma);
1574 if (address == -EFAULT)
1575 continue;
1576 ret = rmap_one(page, vma, address, arg);
1577 if (ret != SWAP_AGAIN)
1578 break;
1579 }
1580 /*
1581 * No nonlinear handling: being always shared, nonlinear vmas
1582 * never contain migration ptes. Decide what to do about this
1583 * limitation to linear when we need rmap_walk() on nonlinear.
1584 */
1585 spin_unlock(&mapping->i_mmap_lock);
1586 return ret;
1587}
1588
1589int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
1590 struct vm_area_struct *, unsigned long, void *), void *arg)
1591{
1592 VM_BUG_ON(!PageLocked(page));
1593
1594 if (unlikely(PageKsm(page)))
1595 return rmap_walk_ksm(page, rmap_one, arg);
1596 else if (PageAnon(page))
1597 return rmap_walk_anon(page, rmap_one, arg);
1598 else
1599 return rmap_walk_file(page, rmap_one, arg);
1600}
1601#endif /* CONFIG_MIGRATION */
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +09001602
Naoya Horiguchie3390f62010-06-15 13:18:13 +09001603#ifdef CONFIG_HUGETLB_PAGE
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +09001604/*
1605 * The following three functions are for anonymous (private mapped) hugepages.
1606 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1607 * and no lru code, because we handle hugepages differently from common pages.
1608 */
1609static void __hugepage_set_anon_rmap(struct page *page,
1610 struct vm_area_struct *vma, unsigned long address, int exclusive)
1611{
1612 struct anon_vma *anon_vma = vma->anon_vma;
Naoya Horiguchi433abed2010-09-10 13:23:03 +09001613
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +09001614 BUG_ON(!anon_vma);
Naoya Horiguchi433abed2010-09-10 13:23:03 +09001615
1616 if (PageAnon(page))
1617 return;
1618 if (!exclusive)
1619 anon_vma = anon_vma->root;
1620
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +09001621 anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1622 page->mapping = (struct address_space *) anon_vma;
1623 page->index = linear_page_index(vma, address);
1624}
1625
1626void hugepage_add_anon_rmap(struct page *page,
1627 struct vm_area_struct *vma, unsigned long address)
1628{
1629 struct anon_vma *anon_vma = vma->anon_vma;
1630 int first;
Naoya Horiguchia850ea32010-09-10 13:23:06 +09001631
1632 BUG_ON(!PageLocked(page));
Naoya Horiguchi0fe6e202010-05-28 09:29:16 +09001633 BUG_ON(!anon_vma);
1634 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1635 first = atomic_inc_and_test(&page->_mapcount);
1636 if (first)
1637 __hugepage_set_anon_rmap(page, vma, address, 0);
1638}
1639
1640void hugepage_add_new_anon_rmap(struct page *page,
1641 struct vm_area_struct *vma, unsigned long address)
1642{
1643 BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1644 atomic_set(&page->_mapcount, 0);
1645 __hugepage_set_anon_rmap(page, vma, address, 1);
1646}
Naoya Horiguchie3390f62010-06-15 13:18:13 +09001647#endif /* CONFIG_HUGETLB_PAGE */