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Commit | Line | Data |
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f8af4da3 | 1 | /* |
31dbd01f IE |
2 | * Memory merging support. |
3 | * | |
4 | * This code enables dynamic sharing of identical pages found in different | |
5 | * memory areas, even if they are not shared by fork() | |
6 | * | |
36b2528d | 7 | * Copyright (C) 2008-2009 Red Hat, Inc. |
31dbd01f IE |
8 | * Authors: |
9 | * Izik Eidus | |
10 | * Andrea Arcangeli | |
11 | * Chris Wright | |
36b2528d | 12 | * Hugh Dickins |
31dbd01f IE |
13 | * |
14 | * This work is licensed under the terms of the GNU GPL, version 2. | |
f8af4da3 HD |
15 | */ |
16 | ||
17 | #include <linux/errno.h> | |
31dbd01f IE |
18 | #include <linux/mm.h> |
19 | #include <linux/fs.h> | |
f8af4da3 | 20 | #include <linux/mman.h> |
31dbd01f IE |
21 | #include <linux/sched.h> |
22 | #include <linux/rwsem.h> | |
23 | #include <linux/pagemap.h> | |
24 | #include <linux/rmap.h> | |
25 | #include <linux/spinlock.h> | |
26 | #include <linux/jhash.h> | |
27 | #include <linux/delay.h> | |
28 | #include <linux/kthread.h> | |
29 | #include <linux/wait.h> | |
30 | #include <linux/slab.h> | |
31 | #include <linux/rbtree.h> | |
62b61f61 | 32 | #include <linux/memory.h> |
31dbd01f | 33 | #include <linux/mmu_notifier.h> |
2c6854fd | 34 | #include <linux/swap.h> |
f8af4da3 | 35 | #include <linux/ksm.h> |
4ca3a69b | 36 | #include <linux/hashtable.h> |
878aee7d | 37 | #include <linux/freezer.h> |
72788c38 | 38 | #include <linux/oom.h> |
90bd6fd3 | 39 | #include <linux/numa.h> |
f8af4da3 | 40 | |
31dbd01f | 41 | #include <asm/tlbflush.h> |
73848b46 | 42 | #include "internal.h" |
31dbd01f | 43 | |
e850dcf5 HD |
44 | #ifdef CONFIG_NUMA |
45 | #define NUMA(x) (x) | |
46 | #define DO_NUMA(x) do { (x); } while (0) | |
47 | #else | |
48 | #define NUMA(x) (0) | |
49 | #define DO_NUMA(x) do { } while (0) | |
50 | #endif | |
51 | ||
31dbd01f IE |
52 | /* |
53 | * A few notes about the KSM scanning process, | |
54 | * to make it easier to understand the data structures below: | |
55 | * | |
56 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
57 | * contents into a data structure that holds pointers to the pages' locations. | |
58 | * | |
59 | * Since the contents of the pages may change at any moment, KSM cannot just | |
60 | * insert the pages into a normal sorted tree and expect it to find anything. | |
61 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
62 | * | |
63 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
64 | * by their contents. Because each such page is write-protected, searching on | |
65 | * this tree is fully assured to be working (except when pages are unmapped), | |
66 | * and therefore this tree is called the stable tree. | |
67 | * | |
68 | * In addition to the stable tree, KSM uses a second data structure called the | |
69 | * unstable tree: this tree holds pointers to pages which have been found to | |
70 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
71 | * by their contents, but since they are not write-protected, KSM cannot rely | |
72 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
73 | * be corrupted as its contents are modified, and so it is called unstable. | |
74 | * | |
75 | * KSM solves this problem by several techniques: | |
76 | * | |
77 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
78 | * memory areas, and then the tree is rebuilt again from the beginning. | |
79 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
80 | * has not changed since the previous scan of all memory areas. | |
81 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
82 | * colors of the nodes and not on their contents, assuring that even when | |
83 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
84 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
85 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
86 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
87 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
88 | * it is secured in the stable tree. (When we scan a new page, we first | |
89 | * compare it against the stable tree, and then against the unstable tree.) | |
8fdb3dbf HD |
90 | * |
91 | * If the merge_across_nodes tunable is unset, then KSM maintains multiple | |
92 | * stable trees and multiple unstable trees: one of each for each NUMA node. | |
31dbd01f IE |
93 | */ |
94 | ||
95 | /** | |
96 | * struct mm_slot - ksm information per mm that is being scanned | |
97 | * @link: link to the mm_slots hash list | |
98 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head | |
6514d511 | 99 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
100 | * @mm: the mm that this information is valid for |
101 | */ | |
102 | struct mm_slot { | |
103 | struct hlist_node link; | |
104 | struct list_head mm_list; | |
6514d511 | 105 | struct rmap_item *rmap_list; |
31dbd01f IE |
106 | struct mm_struct *mm; |
107 | }; | |
108 | ||
109 | /** | |
110 | * struct ksm_scan - cursor for scanning | |
111 | * @mm_slot: the current mm_slot we are scanning | |
112 | * @address: the next address inside that to be scanned | |
6514d511 | 113 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
114 | * @seqnr: count of completed full scans (needed when removing unstable node) |
115 | * | |
116 | * There is only the one ksm_scan instance of this cursor structure. | |
117 | */ | |
118 | struct ksm_scan { | |
119 | struct mm_slot *mm_slot; | |
120 | unsigned long address; | |
6514d511 | 121 | struct rmap_item **rmap_list; |
31dbd01f IE |
122 | unsigned long seqnr; |
123 | }; | |
124 | ||
7b6ba2c7 HD |
125 | /** |
126 | * struct stable_node - node of the stable rbtree | |
127 | * @node: rb node of this ksm page in the stable tree | |
4146d2d6 HD |
128 | * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list |
129 | * @list: linked into migrate_nodes, pending placement in the proper node tree | |
7b6ba2c7 | 130 | * @hlist: hlist head of rmap_items using this ksm page |
4146d2d6 HD |
131 | * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid) |
132 | * @nid: NUMA node id of stable tree in which linked (may not match kpfn) | |
7b6ba2c7 HD |
133 | */ |
134 | struct stable_node { | |
4146d2d6 HD |
135 | union { |
136 | struct rb_node node; /* when node of stable tree */ | |
137 | struct { /* when listed for migration */ | |
138 | struct list_head *head; | |
139 | struct list_head list; | |
140 | }; | |
141 | }; | |
7b6ba2c7 | 142 | struct hlist_head hlist; |
62b61f61 | 143 | unsigned long kpfn; |
4146d2d6 HD |
144 | #ifdef CONFIG_NUMA |
145 | int nid; | |
146 | #endif | |
7b6ba2c7 HD |
147 | }; |
148 | ||
31dbd01f IE |
149 | /** |
150 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 | 151 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
db114b83 | 152 | * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree |
31dbd01f IE |
153 | * @mm: the memory structure this rmap_item is pointing into |
154 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
155 | * @oldchecksum: previous checksum of the page at that virtual address | |
e850dcf5 | 156 | * @nid: NUMA node id of unstable tree in which linked (may not match page) |
7b6ba2c7 HD |
157 | * @node: rb node of this rmap_item in the unstable tree |
158 | * @head: pointer to stable_node heading this list in the stable tree | |
159 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
160 | */ |
161 | struct rmap_item { | |
6514d511 | 162 | struct rmap_item *rmap_list; |
db114b83 | 163 | struct anon_vma *anon_vma; /* when stable */ |
31dbd01f IE |
164 | struct mm_struct *mm; |
165 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 166 | unsigned int oldchecksum; /* when unstable */ |
90bd6fd3 | 167 | #ifdef CONFIG_NUMA |
e850dcf5 | 168 | int nid; |
90bd6fd3 | 169 | #endif |
31dbd01f | 170 | union { |
7b6ba2c7 HD |
171 | struct rb_node node; /* when node of unstable tree */ |
172 | struct { /* when listed from stable tree */ | |
173 | struct stable_node *head; | |
174 | struct hlist_node hlist; | |
175 | }; | |
31dbd01f IE |
176 | }; |
177 | }; | |
178 | ||
179 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
180 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
181 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
182 | |
183 | /* The stable and unstable tree heads */ | |
90bd6fd3 PH |
184 | static struct rb_root root_unstable_tree[MAX_NUMNODES]; |
185 | static struct rb_root root_stable_tree[MAX_NUMNODES]; | |
31dbd01f | 186 | |
4146d2d6 HD |
187 | /* Recently migrated nodes of stable tree, pending proper placement */ |
188 | static LIST_HEAD(migrate_nodes); | |
189 | ||
4ca3a69b SL |
190 | #define MM_SLOTS_HASH_BITS 10 |
191 | static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
31dbd01f IE |
192 | |
193 | static struct mm_slot ksm_mm_head = { | |
194 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
195 | }; | |
196 | static struct ksm_scan ksm_scan = { | |
197 | .mm_slot = &ksm_mm_head, | |
198 | }; | |
199 | ||
200 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 201 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
202 | static struct kmem_cache *mm_slot_cache; |
203 | ||
204 | /* The number of nodes in the stable tree */ | |
b4028260 | 205 | static unsigned long ksm_pages_shared; |
31dbd01f | 206 | |
e178dfde | 207 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 208 | static unsigned long ksm_pages_sharing; |
31dbd01f | 209 | |
473b0ce4 HD |
210 | /* The number of nodes in the unstable tree */ |
211 | static unsigned long ksm_pages_unshared; | |
212 | ||
213 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
214 | static unsigned long ksm_rmap_items; | |
215 | ||
31dbd01f | 216 | /* Number of pages ksmd should scan in one batch */ |
2c6854fd | 217 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
218 | |
219 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 220 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f | 221 | |
e850dcf5 | 222 | #ifdef CONFIG_NUMA |
90bd6fd3 PH |
223 | /* Zeroed when merging across nodes is not allowed */ |
224 | static unsigned int ksm_merge_across_nodes = 1; | |
e850dcf5 HD |
225 | #else |
226 | #define ksm_merge_across_nodes 1U | |
227 | #endif | |
90bd6fd3 | 228 | |
31dbd01f IE |
229 | #define KSM_RUN_STOP 0 |
230 | #define KSM_RUN_MERGE 1 | |
231 | #define KSM_RUN_UNMERGE 2 | |
ef4d43a8 HD |
232 | #define KSM_RUN_OFFLINE 4 |
233 | static unsigned long ksm_run = KSM_RUN_STOP; | |
234 | static void wait_while_offlining(void); | |
31dbd01f IE |
235 | |
236 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
237 | static DEFINE_MUTEX(ksm_thread_mutex); | |
238 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
239 | ||
240 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
241 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
242 | (__flags), NULL) | |
243 | ||
244 | static int __init ksm_slab_init(void) | |
245 | { | |
246 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
247 | if (!rmap_item_cache) | |
248 | goto out; | |
249 | ||
7b6ba2c7 HD |
250 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
251 | if (!stable_node_cache) | |
252 | goto out_free1; | |
253 | ||
31dbd01f IE |
254 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
255 | if (!mm_slot_cache) | |
7b6ba2c7 | 256 | goto out_free2; |
31dbd01f IE |
257 | |
258 | return 0; | |
259 | ||
7b6ba2c7 HD |
260 | out_free2: |
261 | kmem_cache_destroy(stable_node_cache); | |
262 | out_free1: | |
31dbd01f IE |
263 | kmem_cache_destroy(rmap_item_cache); |
264 | out: | |
265 | return -ENOMEM; | |
266 | } | |
267 | ||
268 | static void __init ksm_slab_free(void) | |
269 | { | |
270 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 271 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
272 | kmem_cache_destroy(rmap_item_cache); |
273 | mm_slot_cache = NULL; | |
274 | } | |
275 | ||
276 | static inline struct rmap_item *alloc_rmap_item(void) | |
277 | { | |
473b0ce4 HD |
278 | struct rmap_item *rmap_item; |
279 | ||
280 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
281 | if (rmap_item) | |
282 | ksm_rmap_items++; | |
283 | return rmap_item; | |
31dbd01f IE |
284 | } |
285 | ||
286 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
287 | { | |
473b0ce4 | 288 | ksm_rmap_items--; |
31dbd01f IE |
289 | rmap_item->mm = NULL; /* debug safety */ |
290 | kmem_cache_free(rmap_item_cache, rmap_item); | |
291 | } | |
292 | ||
7b6ba2c7 HD |
293 | static inline struct stable_node *alloc_stable_node(void) |
294 | { | |
295 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); | |
296 | } | |
297 | ||
298 | static inline void free_stable_node(struct stable_node *stable_node) | |
299 | { | |
300 | kmem_cache_free(stable_node_cache, stable_node); | |
301 | } | |
302 | ||
31dbd01f IE |
303 | static inline struct mm_slot *alloc_mm_slot(void) |
304 | { | |
305 | if (!mm_slot_cache) /* initialization failed */ | |
306 | return NULL; | |
307 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
308 | } | |
309 | ||
310 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
311 | { | |
312 | kmem_cache_free(mm_slot_cache, mm_slot); | |
313 | } | |
314 | ||
31dbd01f IE |
315 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
316 | { | |
31dbd01f | 317 | struct hlist_node *node; |
4ca3a69b SL |
318 | struct mm_slot *slot; |
319 | ||
320 | hash_for_each_possible(mm_slots_hash, slot, node, link, (unsigned long)mm) | |
321 | if (slot->mm == mm) | |
322 | return slot; | |
31dbd01f | 323 | |
31dbd01f IE |
324 | return NULL; |
325 | } | |
326 | ||
327 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
328 | struct mm_slot *mm_slot) | |
329 | { | |
31dbd01f | 330 | mm_slot->mm = mm; |
4ca3a69b | 331 | hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm); |
31dbd01f IE |
332 | } |
333 | ||
a913e182 HD |
334 | /* |
335 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
336 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
337 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
338 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
339 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
340 | * places for correctness, in some places just to avoid unnecessary work. | |
341 | */ | |
342 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
343 | { | |
344 | return atomic_read(&mm->mm_users) == 0; | |
345 | } | |
346 | ||
31dbd01f IE |
347 | /* |
348 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
349 | * | |
350 | * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1) | |
351 | * put_page(page); | |
352 | * | |
353 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
354 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
355 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
356 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
357 | */ | |
d952b791 | 358 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
359 | { |
360 | struct page *page; | |
d952b791 | 361 | int ret = 0; |
31dbd01f IE |
362 | |
363 | do { | |
364 | cond_resched(); | |
365 | page = follow_page(vma, addr, FOLL_GET); | |
22eccdd7 | 366 | if (IS_ERR_OR_NULL(page)) |
31dbd01f IE |
367 | break; |
368 | if (PageKsm(page)) | |
369 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
370 | FAULT_FLAG_WRITE); | |
371 | else | |
372 | ret = VM_FAULT_WRITE; | |
373 | put_page(page); | |
d952b791 HD |
374 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_OOM))); |
375 | /* | |
376 | * We must loop because handle_mm_fault() may back out if there's | |
377 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
378 | * | |
379 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
380 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
381 | * but note that a concurrent fault might break PageKsm for us. | |
382 | * | |
383 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
384 | * backing file, which also invalidates anonymous pages: that's | |
385 | * okay, that truncation will have unmapped the PageKsm for us. | |
386 | * | |
387 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
388 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
389 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
390 | * to user; and ksmd, having no mm, would never be chosen for that. | |
391 | * | |
392 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
393 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
394 | * even ksmd can fail in this way - though it's usually breaking ksm | |
395 | * just to undo a merge it made a moment before, so unlikely to oom. | |
396 | * | |
397 | * That's a pity: we might therefore have more kernel pages allocated | |
398 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
399 | * will retry to break_cow on each pass, so should recover the page | |
400 | * in due course. The important thing is to not let VM_MERGEABLE | |
401 | * be cleared while any such pages might remain in the area. | |
402 | */ | |
403 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
404 | } |
405 | ||
ef694222 BL |
406 | static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, |
407 | unsigned long addr) | |
408 | { | |
409 | struct vm_area_struct *vma; | |
410 | if (ksm_test_exit(mm)) | |
411 | return NULL; | |
412 | vma = find_vma(mm, addr); | |
413 | if (!vma || vma->vm_start > addr) | |
414 | return NULL; | |
415 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
416 | return NULL; | |
417 | return vma; | |
418 | } | |
419 | ||
8dd3557a | 420 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 421 | { |
8dd3557a HD |
422 | struct mm_struct *mm = rmap_item->mm; |
423 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
424 | struct vm_area_struct *vma; |
425 | ||
4035c07a HD |
426 | /* |
427 | * It is not an accident that whenever we want to break COW | |
428 | * to undo, we also need to drop a reference to the anon_vma. | |
429 | */ | |
9e60109f | 430 | put_anon_vma(rmap_item->anon_vma); |
4035c07a | 431 | |
81464e30 | 432 | down_read(&mm->mmap_sem); |
ef694222 BL |
433 | vma = find_mergeable_vma(mm, addr); |
434 | if (vma) | |
435 | break_ksm(vma, addr); | |
31dbd01f IE |
436 | up_read(&mm->mmap_sem); |
437 | } | |
438 | ||
29ad768c AA |
439 | static struct page *page_trans_compound_anon(struct page *page) |
440 | { | |
441 | if (PageTransCompound(page)) { | |
22e5c47e | 442 | struct page *head = compound_trans_head(page); |
29ad768c | 443 | /* |
22e5c47e AA |
444 | * head may actually be splitted and freed from under |
445 | * us but it's ok here. | |
29ad768c | 446 | */ |
29ad768c AA |
447 | if (PageAnon(head)) |
448 | return head; | |
449 | } | |
450 | return NULL; | |
451 | } | |
452 | ||
31dbd01f IE |
453 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) |
454 | { | |
455 | struct mm_struct *mm = rmap_item->mm; | |
456 | unsigned long addr = rmap_item->address; | |
457 | struct vm_area_struct *vma; | |
458 | struct page *page; | |
459 | ||
460 | down_read(&mm->mmap_sem); | |
ef694222 BL |
461 | vma = find_mergeable_vma(mm, addr); |
462 | if (!vma) | |
31dbd01f IE |
463 | goto out; |
464 | ||
465 | page = follow_page(vma, addr, FOLL_GET); | |
22eccdd7 | 466 | if (IS_ERR_OR_NULL(page)) |
31dbd01f | 467 | goto out; |
29ad768c | 468 | if (PageAnon(page) || page_trans_compound_anon(page)) { |
31dbd01f IE |
469 | flush_anon_page(vma, page, addr); |
470 | flush_dcache_page(page); | |
471 | } else { | |
472 | put_page(page); | |
473 | out: page = NULL; | |
474 | } | |
475 | up_read(&mm->mmap_sem); | |
476 | return page; | |
477 | } | |
478 | ||
90bd6fd3 PH |
479 | /* |
480 | * This helper is used for getting right index into array of tree roots. | |
481 | * When merge_across_nodes knob is set to 1, there are only two rb-trees for | |
482 | * stable and unstable pages from all nodes with roots in index 0. Otherwise, | |
483 | * every node has its own stable and unstable tree. | |
484 | */ | |
485 | static inline int get_kpfn_nid(unsigned long kpfn) | |
486 | { | |
e850dcf5 | 487 | return ksm_merge_across_nodes ? 0 : pfn_to_nid(kpfn); |
90bd6fd3 PH |
488 | } |
489 | ||
4035c07a HD |
490 | static void remove_node_from_stable_tree(struct stable_node *stable_node) |
491 | { | |
492 | struct rmap_item *rmap_item; | |
493 | struct hlist_node *hlist; | |
494 | ||
495 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { | |
496 | if (rmap_item->hlist.next) | |
497 | ksm_pages_sharing--; | |
498 | else | |
499 | ksm_pages_shared--; | |
9e60109f | 500 | put_anon_vma(rmap_item->anon_vma); |
4035c07a HD |
501 | rmap_item->address &= PAGE_MASK; |
502 | cond_resched(); | |
503 | } | |
504 | ||
4146d2d6 HD |
505 | if (stable_node->head == &migrate_nodes) |
506 | list_del(&stable_node->list); | |
507 | else | |
508 | rb_erase(&stable_node->node, | |
509 | &root_stable_tree[NUMA(stable_node->nid)]); | |
4035c07a HD |
510 | free_stable_node(stable_node); |
511 | } | |
512 | ||
513 | /* | |
514 | * get_ksm_page: checks if the page indicated by the stable node | |
515 | * is still its ksm page, despite having held no reference to it. | |
516 | * In which case we can trust the content of the page, and it | |
517 | * returns the gotten page; but if the page has now been zapped, | |
518 | * remove the stale node from the stable tree and return NULL. | |
c8d6553b | 519 | * But beware, the stable node's page might be being migrated. |
4035c07a HD |
520 | * |
521 | * You would expect the stable_node to hold a reference to the ksm page. | |
522 | * But if it increments the page's count, swapping out has to wait for | |
523 | * ksmd to come around again before it can free the page, which may take | |
524 | * seconds or even minutes: much too unresponsive. So instead we use a | |
525 | * "keyhole reference": access to the ksm page from the stable node peeps | |
526 | * out through its keyhole to see if that page still holds the right key, | |
527 | * pointing back to this stable node. This relies on freeing a PageAnon | |
528 | * page to reset its page->mapping to NULL, and relies on no other use of | |
529 | * a page to put something that might look like our key in page->mapping. | |
4035c07a HD |
530 | * is on its way to being freed; but it is an anomaly to bear in mind. |
531 | */ | |
8fdb3dbf | 532 | static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) |
4035c07a HD |
533 | { |
534 | struct page *page; | |
535 | void *expected_mapping; | |
c8d6553b | 536 | unsigned long kpfn; |
4035c07a | 537 | |
4035c07a HD |
538 | expected_mapping = (void *)stable_node + |
539 | (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); | |
c8d6553b HD |
540 | again: |
541 | kpfn = ACCESS_ONCE(stable_node->kpfn); | |
542 | page = pfn_to_page(kpfn); | |
543 | ||
544 | /* | |
545 | * page is computed from kpfn, so on most architectures reading | |
546 | * page->mapping is naturally ordered after reading node->kpfn, | |
547 | * but on Alpha we need to be more careful. | |
548 | */ | |
549 | smp_read_barrier_depends(); | |
550 | if (ACCESS_ONCE(page->mapping) != expected_mapping) | |
4035c07a | 551 | goto stale; |
c8d6553b HD |
552 | |
553 | /* | |
554 | * We cannot do anything with the page while its refcount is 0. | |
555 | * Usually 0 means free, or tail of a higher-order page: in which | |
556 | * case this node is no longer referenced, and should be freed; | |
557 | * however, it might mean that the page is under page_freeze_refs(). | |
558 | * The __remove_mapping() case is easy, again the node is now stale; | |
559 | * but if page is swapcache in migrate_page_move_mapping(), it might | |
560 | * still be our page, in which case it's essential to keep the node. | |
561 | */ | |
562 | while (!get_page_unless_zero(page)) { | |
563 | /* | |
564 | * Another check for page->mapping != expected_mapping would | |
565 | * work here too. We have chosen the !PageSwapCache test to | |
566 | * optimize the common case, when the page is or is about to | |
567 | * be freed: PageSwapCache is cleared (under spin_lock_irq) | |
568 | * in the freeze_refs section of __remove_mapping(); but Anon | |
569 | * page->mapping reset to NULL later, in free_pages_prepare(). | |
570 | */ | |
571 | if (!PageSwapCache(page)) | |
572 | goto stale; | |
573 | cpu_relax(); | |
574 | } | |
575 | ||
576 | if (ACCESS_ONCE(page->mapping) != expected_mapping) { | |
4035c07a HD |
577 | put_page(page); |
578 | goto stale; | |
579 | } | |
c8d6553b | 580 | |
8fdb3dbf | 581 | if (lock_it) { |
8aafa6a4 | 582 | lock_page(page); |
c8d6553b | 583 | if (ACCESS_ONCE(page->mapping) != expected_mapping) { |
8aafa6a4 HD |
584 | unlock_page(page); |
585 | put_page(page); | |
586 | goto stale; | |
587 | } | |
588 | } | |
4035c07a | 589 | return page; |
c8d6553b | 590 | |
4035c07a | 591 | stale: |
c8d6553b HD |
592 | /* |
593 | * We come here from above when page->mapping or !PageSwapCache | |
594 | * suggests that the node is stale; but it might be under migration. | |
595 | * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(), | |
596 | * before checking whether node->kpfn has been changed. | |
597 | */ | |
598 | smp_rmb(); | |
599 | if (ACCESS_ONCE(stable_node->kpfn) != kpfn) | |
600 | goto again; | |
4035c07a HD |
601 | remove_node_from_stable_tree(stable_node); |
602 | return NULL; | |
603 | } | |
604 | ||
31dbd01f IE |
605 | /* |
606 | * Removing rmap_item from stable or unstable tree. | |
607 | * This function will clean the information from the stable/unstable tree. | |
608 | */ | |
609 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
610 | { | |
7b6ba2c7 HD |
611 | if (rmap_item->address & STABLE_FLAG) { |
612 | struct stable_node *stable_node; | |
5ad64688 | 613 | struct page *page; |
31dbd01f | 614 | |
7b6ba2c7 | 615 | stable_node = rmap_item->head; |
8aafa6a4 | 616 | page = get_ksm_page(stable_node, true); |
4035c07a HD |
617 | if (!page) |
618 | goto out; | |
5ad64688 | 619 | |
7b6ba2c7 | 620 | hlist_del(&rmap_item->hlist); |
4035c07a HD |
621 | unlock_page(page); |
622 | put_page(page); | |
08beca44 | 623 | |
4035c07a HD |
624 | if (stable_node->hlist.first) |
625 | ksm_pages_sharing--; | |
626 | else | |
7b6ba2c7 | 627 | ksm_pages_shared--; |
31dbd01f | 628 | |
9e60109f | 629 | put_anon_vma(rmap_item->anon_vma); |
93d17715 | 630 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 631 | |
7b6ba2c7 | 632 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
633 | unsigned char age; |
634 | /* | |
9ba69294 | 635 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 636 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
637 | * But be careful when an mm is exiting: do the rb_erase |
638 | * if this rmap_item was inserted by this scan, rather | |
639 | * than left over from before. | |
31dbd01f IE |
640 | */ |
641 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 642 | BUG_ON(age > 1); |
31dbd01f | 643 | if (!age) |
90bd6fd3 | 644 | rb_erase(&rmap_item->node, |
e850dcf5 | 645 | &root_unstable_tree[NUMA(rmap_item->nid)]); |
473b0ce4 | 646 | ksm_pages_unshared--; |
93d17715 | 647 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 648 | } |
4035c07a | 649 | out: |
31dbd01f IE |
650 | cond_resched(); /* we're called from many long loops */ |
651 | } | |
652 | ||
31dbd01f | 653 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 654 | struct rmap_item **rmap_list) |
31dbd01f | 655 | { |
6514d511 HD |
656 | while (*rmap_list) { |
657 | struct rmap_item *rmap_item = *rmap_list; | |
658 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 659 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
660 | free_rmap_item(rmap_item); |
661 | } | |
662 | } | |
663 | ||
664 | /* | |
e850dcf5 | 665 | * Though it's very tempting to unmerge rmap_items from stable tree rather |
31dbd01f IE |
666 | * than check every pte of a given vma, the locking doesn't quite work for |
667 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
668 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
669 | * rmap_items from parent to child at fork time (so as not to waste time | |
670 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
671 | * |
672 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
673 | * and freeing memory) when unmerging an area, it's easier to leave that | |
674 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
675 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 676 | */ |
d952b791 HD |
677 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
678 | unsigned long start, unsigned long end) | |
31dbd01f IE |
679 | { |
680 | unsigned long addr; | |
d952b791 | 681 | int err = 0; |
31dbd01f | 682 | |
d952b791 | 683 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
684 | if (ksm_test_exit(vma->vm_mm)) |
685 | break; | |
d952b791 HD |
686 | if (signal_pending(current)) |
687 | err = -ERESTARTSYS; | |
688 | else | |
689 | err = break_ksm(vma, addr); | |
690 | } | |
691 | return err; | |
31dbd01f IE |
692 | } |
693 | ||
2ffd8679 HD |
694 | #ifdef CONFIG_SYSFS |
695 | /* | |
696 | * Only called through the sysfs control interface: | |
697 | */ | |
cbf86cfe HD |
698 | static int remove_stable_node(struct stable_node *stable_node) |
699 | { | |
700 | struct page *page; | |
701 | int err; | |
702 | ||
703 | page = get_ksm_page(stable_node, true); | |
704 | if (!page) { | |
705 | /* | |
706 | * get_ksm_page did remove_node_from_stable_tree itself. | |
707 | */ | |
708 | return 0; | |
709 | } | |
710 | ||
8fdb3dbf HD |
711 | if (WARN_ON_ONCE(page_mapped(page))) { |
712 | /* | |
713 | * This should not happen: but if it does, just refuse to let | |
714 | * merge_across_nodes be switched - there is no need to panic. | |
715 | */ | |
cbf86cfe | 716 | err = -EBUSY; |
8fdb3dbf | 717 | } else { |
cbf86cfe | 718 | /* |
8fdb3dbf HD |
719 | * The stable node did not yet appear stale to get_ksm_page(), |
720 | * since that allows for an unmapped ksm page to be recognized | |
721 | * right up until it is freed; but the node is safe to remove. | |
cbf86cfe HD |
722 | * This page might be in a pagevec waiting to be freed, |
723 | * or it might be PageSwapCache (perhaps under writeback), | |
724 | * or it might have been removed from swapcache a moment ago. | |
725 | */ | |
726 | set_page_stable_node(page, NULL); | |
727 | remove_node_from_stable_tree(stable_node); | |
728 | err = 0; | |
729 | } | |
730 | ||
731 | unlock_page(page); | |
732 | put_page(page); | |
733 | return err; | |
734 | } | |
735 | ||
736 | static int remove_all_stable_nodes(void) | |
737 | { | |
738 | struct stable_node *stable_node; | |
4146d2d6 | 739 | struct list_head *this, *next; |
cbf86cfe HD |
740 | int nid; |
741 | int err = 0; | |
742 | ||
743 | for (nid = 0; nid < nr_node_ids; nid++) { | |
744 | while (root_stable_tree[nid].rb_node) { | |
745 | stable_node = rb_entry(root_stable_tree[nid].rb_node, | |
746 | struct stable_node, node); | |
747 | if (remove_stable_node(stable_node)) { | |
748 | err = -EBUSY; | |
749 | break; /* proceed to next nid */ | |
750 | } | |
751 | cond_resched(); | |
752 | } | |
753 | } | |
4146d2d6 HD |
754 | list_for_each_safe(this, next, &migrate_nodes) { |
755 | stable_node = list_entry(this, struct stable_node, list); | |
756 | if (remove_stable_node(stable_node)) | |
757 | err = -EBUSY; | |
758 | cond_resched(); | |
759 | } | |
cbf86cfe HD |
760 | return err; |
761 | } | |
762 | ||
d952b791 | 763 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
764 | { |
765 | struct mm_slot *mm_slot; | |
766 | struct mm_struct *mm; | |
767 | struct vm_area_struct *vma; | |
d952b791 HD |
768 | int err = 0; |
769 | ||
770 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 771 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
772 | struct mm_slot, mm_list); |
773 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 774 | |
9ba69294 HD |
775 | for (mm_slot = ksm_scan.mm_slot; |
776 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
777 | mm = mm_slot->mm; |
778 | down_read(&mm->mmap_sem); | |
779 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
780 | if (ksm_test_exit(mm)) |
781 | break; | |
31dbd01f IE |
782 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
783 | continue; | |
d952b791 HD |
784 | err = unmerge_ksm_pages(vma, |
785 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
786 | if (err) |
787 | goto error; | |
31dbd01f | 788 | } |
9ba69294 | 789 | |
6514d511 | 790 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
791 | |
792 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 793 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 794 | struct mm_slot, mm_list); |
9ba69294 | 795 | if (ksm_test_exit(mm)) { |
4ca3a69b | 796 | hash_del(&mm_slot->link); |
9ba69294 HD |
797 | list_del(&mm_slot->mm_list); |
798 | spin_unlock(&ksm_mmlist_lock); | |
799 | ||
800 | free_mm_slot(mm_slot); | |
801 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
802 | up_read(&mm->mmap_sem); | |
803 | mmdrop(mm); | |
804 | } else { | |
805 | spin_unlock(&ksm_mmlist_lock); | |
806 | up_read(&mm->mmap_sem); | |
807 | } | |
31dbd01f IE |
808 | } |
809 | ||
cbf86cfe HD |
810 | /* Clean up stable nodes, but don't worry if some are still busy */ |
811 | remove_all_stable_nodes(); | |
d952b791 | 812 | ksm_scan.seqnr = 0; |
9ba69294 HD |
813 | return 0; |
814 | ||
815 | error: | |
816 | up_read(&mm->mmap_sem); | |
31dbd01f | 817 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 818 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 819 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 820 | return err; |
31dbd01f | 821 | } |
2ffd8679 | 822 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 823 | |
31dbd01f IE |
824 | static u32 calc_checksum(struct page *page) |
825 | { | |
826 | u32 checksum; | |
9b04c5fe | 827 | void *addr = kmap_atomic(page); |
31dbd01f | 828 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); |
9b04c5fe | 829 | kunmap_atomic(addr); |
31dbd01f IE |
830 | return checksum; |
831 | } | |
832 | ||
833 | static int memcmp_pages(struct page *page1, struct page *page2) | |
834 | { | |
835 | char *addr1, *addr2; | |
836 | int ret; | |
837 | ||
9b04c5fe CW |
838 | addr1 = kmap_atomic(page1); |
839 | addr2 = kmap_atomic(page2); | |
31dbd01f | 840 | ret = memcmp(addr1, addr2, PAGE_SIZE); |
9b04c5fe CW |
841 | kunmap_atomic(addr2); |
842 | kunmap_atomic(addr1); | |
31dbd01f IE |
843 | return ret; |
844 | } | |
845 | ||
846 | static inline int pages_identical(struct page *page1, struct page *page2) | |
847 | { | |
848 | return !memcmp_pages(page1, page2); | |
849 | } | |
850 | ||
851 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
852 | pte_t *orig_pte) | |
853 | { | |
854 | struct mm_struct *mm = vma->vm_mm; | |
855 | unsigned long addr; | |
856 | pte_t *ptep; | |
857 | spinlock_t *ptl; | |
858 | int swapped; | |
859 | int err = -EFAULT; | |
6bdb913f HE |
860 | unsigned long mmun_start; /* For mmu_notifiers */ |
861 | unsigned long mmun_end; /* For mmu_notifiers */ | |
31dbd01f IE |
862 | |
863 | addr = page_address_in_vma(page, vma); | |
864 | if (addr == -EFAULT) | |
865 | goto out; | |
866 | ||
29ad768c | 867 | BUG_ON(PageTransCompound(page)); |
6bdb913f HE |
868 | |
869 | mmun_start = addr; | |
870 | mmun_end = addr + PAGE_SIZE; | |
871 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
872 | ||
31dbd01f IE |
873 | ptep = page_check_address(page, mm, addr, &ptl, 0); |
874 | if (!ptep) | |
6bdb913f | 875 | goto out_mn; |
31dbd01f | 876 | |
4e31635c | 877 | if (pte_write(*ptep) || pte_dirty(*ptep)) { |
31dbd01f IE |
878 | pte_t entry; |
879 | ||
880 | swapped = PageSwapCache(page); | |
881 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
882 | /* | |
25985edc | 883 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
31dbd01f IE |
884 | * take any lock, therefore the check that we are going to make |
885 | * with the pagecount against the mapcount is racey and | |
886 | * O_DIRECT can happen right after the check. | |
887 | * So we clear the pte and flush the tlb before the check | |
888 | * this assure us that no O_DIRECT can happen after the check | |
889 | * or in the middle of the check. | |
890 | */ | |
891 | entry = ptep_clear_flush(vma, addr, ptep); | |
892 | /* | |
893 | * Check that no O_DIRECT or similar I/O is in progress on the | |
894 | * page | |
895 | */ | |
31e855ea | 896 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
cb532375 | 897 | set_pte_at(mm, addr, ptep, entry); |
31dbd01f IE |
898 | goto out_unlock; |
899 | } | |
4e31635c HD |
900 | if (pte_dirty(entry)) |
901 | set_page_dirty(page); | |
902 | entry = pte_mkclean(pte_wrprotect(entry)); | |
31dbd01f IE |
903 | set_pte_at_notify(mm, addr, ptep, entry); |
904 | } | |
905 | *orig_pte = *ptep; | |
906 | err = 0; | |
907 | ||
908 | out_unlock: | |
909 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f HE |
910 | out_mn: |
911 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
31dbd01f IE |
912 | out: |
913 | return err; | |
914 | } | |
915 | ||
916 | /** | |
917 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
918 | * @vma: vma that holds the pte pointing to page |
919 | * @page: the page we are replacing by kpage | |
920 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
921 | * @orig_pte: the original value of the pte |
922 | * | |
923 | * Returns 0 on success, -EFAULT on failure. | |
924 | */ | |
8dd3557a HD |
925 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
926 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
927 | { |
928 | struct mm_struct *mm = vma->vm_mm; | |
31dbd01f IE |
929 | pmd_t *pmd; |
930 | pte_t *ptep; | |
931 | spinlock_t *ptl; | |
932 | unsigned long addr; | |
31dbd01f | 933 | int err = -EFAULT; |
6bdb913f HE |
934 | unsigned long mmun_start; /* For mmu_notifiers */ |
935 | unsigned long mmun_end; /* For mmu_notifiers */ | |
31dbd01f | 936 | |
8dd3557a | 937 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
938 | if (addr == -EFAULT) |
939 | goto out; | |
940 | ||
6219049a BL |
941 | pmd = mm_find_pmd(mm, addr); |
942 | if (!pmd) | |
31dbd01f | 943 | goto out; |
29ad768c | 944 | BUG_ON(pmd_trans_huge(*pmd)); |
31dbd01f | 945 | |
6bdb913f HE |
946 | mmun_start = addr; |
947 | mmun_end = addr + PAGE_SIZE; | |
948 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
949 | ||
31dbd01f IE |
950 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
951 | if (!pte_same(*ptep, orig_pte)) { | |
952 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f | 953 | goto out_mn; |
31dbd01f IE |
954 | } |
955 | ||
8dd3557a | 956 | get_page(kpage); |
5ad64688 | 957 | page_add_anon_rmap(kpage, vma, addr); |
31dbd01f IE |
958 | |
959 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
960 | ptep_clear_flush(vma, addr, ptep); | |
8dd3557a | 961 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 962 | |
8dd3557a | 963 | page_remove_rmap(page); |
ae52a2ad HD |
964 | if (!page_mapped(page)) |
965 | try_to_free_swap(page); | |
8dd3557a | 966 | put_page(page); |
31dbd01f IE |
967 | |
968 | pte_unmap_unlock(ptep, ptl); | |
969 | err = 0; | |
6bdb913f HE |
970 | out_mn: |
971 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
31dbd01f IE |
972 | out: |
973 | return err; | |
974 | } | |
975 | ||
29ad768c AA |
976 | static int page_trans_compound_anon_split(struct page *page) |
977 | { | |
978 | int ret = 0; | |
979 | struct page *transhuge_head = page_trans_compound_anon(page); | |
980 | if (transhuge_head) { | |
981 | /* Get the reference on the head to split it. */ | |
982 | if (get_page_unless_zero(transhuge_head)) { | |
983 | /* | |
984 | * Recheck we got the reference while the head | |
985 | * was still anonymous. | |
986 | */ | |
987 | if (PageAnon(transhuge_head)) | |
988 | ret = split_huge_page(transhuge_head); | |
989 | else | |
990 | /* | |
991 | * Retry later if split_huge_page run | |
992 | * from under us. | |
993 | */ | |
994 | ret = 1; | |
995 | put_page(transhuge_head); | |
996 | } else | |
997 | /* Retry later if split_huge_page run from under us. */ | |
998 | ret = 1; | |
999 | } | |
1000 | return ret; | |
1001 | } | |
1002 | ||
31dbd01f IE |
1003 | /* |
1004 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
1005 | * @vma: the vma that holds the pte pointing to page |
1006 | * @page: the PageAnon page that we want to replace with kpage | |
80e14822 HD |
1007 | * @kpage: the PageKsm page that we want to map instead of page, |
1008 | * or NULL the first time when we want to use page as kpage. | |
31dbd01f IE |
1009 | * |
1010 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
1011 | */ | |
1012 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 1013 | struct page *page, struct page *kpage) |
31dbd01f IE |
1014 | { |
1015 | pte_t orig_pte = __pte(0); | |
1016 | int err = -EFAULT; | |
1017 | ||
db114b83 HD |
1018 | if (page == kpage) /* ksm page forked */ |
1019 | return 0; | |
1020 | ||
31dbd01f IE |
1021 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1022 | goto out; | |
29ad768c AA |
1023 | if (PageTransCompound(page) && page_trans_compound_anon_split(page)) |
1024 | goto out; | |
1025 | BUG_ON(PageTransCompound(page)); | |
8dd3557a | 1026 | if (!PageAnon(page)) |
31dbd01f IE |
1027 | goto out; |
1028 | ||
31dbd01f IE |
1029 | /* |
1030 | * We need the page lock to read a stable PageSwapCache in | |
1031 | * write_protect_page(). We use trylock_page() instead of | |
1032 | * lock_page() because we don't want to wait here - we | |
1033 | * prefer to continue scanning and merging different pages, | |
1034 | * then come back to this page when it is unlocked. | |
1035 | */ | |
8dd3557a | 1036 | if (!trylock_page(page)) |
31e855ea | 1037 | goto out; |
31dbd01f IE |
1038 | /* |
1039 | * If this anonymous page is mapped only here, its pte may need | |
1040 | * to be write-protected. If it's mapped elsewhere, all of its | |
1041 | * ptes are necessarily already write-protected. But in either | |
1042 | * case, we need to lock and check page_count is not raised. | |
1043 | */ | |
80e14822 HD |
1044 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
1045 | if (!kpage) { | |
1046 | /* | |
1047 | * While we hold page lock, upgrade page from | |
1048 | * PageAnon+anon_vma to PageKsm+NULL stable_node: | |
1049 | * stable_tree_insert() will update stable_node. | |
1050 | */ | |
1051 | set_page_stable_node(page, NULL); | |
1052 | mark_page_accessed(page); | |
1053 | err = 0; | |
1054 | } else if (pages_identical(page, kpage)) | |
1055 | err = replace_page(vma, page, kpage, orig_pte); | |
1056 | } | |
31dbd01f | 1057 | |
80e14822 | 1058 | if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { |
73848b46 | 1059 | munlock_vma_page(page); |
5ad64688 HD |
1060 | if (!PageMlocked(kpage)) { |
1061 | unlock_page(page); | |
5ad64688 HD |
1062 | lock_page(kpage); |
1063 | mlock_vma_page(kpage); | |
1064 | page = kpage; /* for final unlock */ | |
1065 | } | |
1066 | } | |
73848b46 | 1067 | |
8dd3557a | 1068 | unlock_page(page); |
31dbd01f IE |
1069 | out: |
1070 | return err; | |
1071 | } | |
1072 | ||
81464e30 HD |
1073 | /* |
1074 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
1075 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
1076 | * |
1077 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 1078 | */ |
8dd3557a HD |
1079 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
1080 | struct page *page, struct page *kpage) | |
81464e30 | 1081 | { |
8dd3557a | 1082 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
1083 | struct vm_area_struct *vma; |
1084 | int err = -EFAULT; | |
1085 | ||
8dd3557a HD |
1086 | down_read(&mm->mmap_sem); |
1087 | if (ksm_test_exit(mm)) | |
9ba69294 | 1088 | goto out; |
8dd3557a HD |
1089 | vma = find_vma(mm, rmap_item->address); |
1090 | if (!vma || vma->vm_start > rmap_item->address) | |
81464e30 HD |
1091 | goto out; |
1092 | ||
8dd3557a | 1093 | err = try_to_merge_one_page(vma, page, kpage); |
db114b83 HD |
1094 | if (err) |
1095 | goto out; | |
1096 | ||
1097 | /* Must get reference to anon_vma while still holding mmap_sem */ | |
9e60109f PZ |
1098 | rmap_item->anon_vma = vma->anon_vma; |
1099 | get_anon_vma(vma->anon_vma); | |
81464e30 | 1100 | out: |
8dd3557a | 1101 | up_read(&mm->mmap_sem); |
81464e30 HD |
1102 | return err; |
1103 | } | |
1104 | ||
31dbd01f IE |
1105 | /* |
1106 | * try_to_merge_two_pages - take two identical pages and prepare them | |
1107 | * to be merged into one page. | |
1108 | * | |
8dd3557a HD |
1109 | * This function returns the kpage if we successfully merged two identical |
1110 | * pages into one ksm page, NULL otherwise. | |
31dbd01f | 1111 | * |
80e14822 | 1112 | * Note that this function upgrades page to ksm page: if one of the pages |
31dbd01f IE |
1113 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
1114 | */ | |
8dd3557a HD |
1115 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
1116 | struct page *page, | |
1117 | struct rmap_item *tree_rmap_item, | |
1118 | struct page *tree_page) | |
31dbd01f | 1119 | { |
80e14822 | 1120 | int err; |
31dbd01f | 1121 | |
80e14822 | 1122 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
31dbd01f | 1123 | if (!err) { |
8dd3557a | 1124 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
80e14822 | 1125 | tree_page, page); |
31dbd01f | 1126 | /* |
81464e30 HD |
1127 | * If that fails, we have a ksm page with only one pte |
1128 | * pointing to it: so break it. | |
31dbd01f | 1129 | */ |
4035c07a | 1130 | if (err) |
8dd3557a | 1131 | break_cow(rmap_item); |
31dbd01f | 1132 | } |
80e14822 | 1133 | return err ? NULL : page; |
31dbd01f IE |
1134 | } |
1135 | ||
31dbd01f | 1136 | /* |
8dd3557a | 1137 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
1138 | * |
1139 | * This function checks if there is a page inside the stable tree | |
1140 | * with identical content to the page that we are scanning right now. | |
1141 | * | |
7b6ba2c7 | 1142 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
1143 | * NULL otherwise. |
1144 | */ | |
62b61f61 | 1145 | static struct page *stable_tree_search(struct page *page) |
31dbd01f | 1146 | { |
90bd6fd3 | 1147 | int nid; |
4146d2d6 HD |
1148 | struct rb_node **new; |
1149 | struct rb_node *parent; | |
1150 | struct stable_node *stable_node; | |
1151 | struct stable_node *page_node; | |
31dbd01f | 1152 | |
4146d2d6 HD |
1153 | page_node = page_stable_node(page); |
1154 | if (page_node && page_node->head != &migrate_nodes) { | |
1155 | /* ksm page forked */ | |
08beca44 | 1156 | get_page(page); |
62b61f61 | 1157 | return page; |
08beca44 HD |
1158 | } |
1159 | ||
90bd6fd3 | 1160 | nid = get_kpfn_nid(page_to_pfn(page)); |
4146d2d6 HD |
1161 | again: |
1162 | new = &root_stable_tree[nid].rb_node; | |
1163 | parent = NULL; | |
90bd6fd3 | 1164 | |
4146d2d6 | 1165 | while (*new) { |
4035c07a | 1166 | struct page *tree_page; |
31dbd01f IE |
1167 | int ret; |
1168 | ||
08beca44 | 1169 | cond_resched(); |
4146d2d6 | 1170 | stable_node = rb_entry(*new, struct stable_node, node); |
8aafa6a4 | 1171 | tree_page = get_ksm_page(stable_node, false); |
4035c07a HD |
1172 | if (!tree_page) |
1173 | return NULL; | |
31dbd01f | 1174 | |
4035c07a | 1175 | ret = memcmp_pages(page, tree_page); |
c8d6553b | 1176 | put_page(tree_page); |
31dbd01f | 1177 | |
4146d2d6 | 1178 | parent = *new; |
c8d6553b | 1179 | if (ret < 0) |
4146d2d6 | 1180 | new = &parent->rb_left; |
c8d6553b | 1181 | else if (ret > 0) |
4146d2d6 | 1182 | new = &parent->rb_right; |
c8d6553b HD |
1183 | else { |
1184 | /* | |
1185 | * Lock and unlock the stable_node's page (which | |
1186 | * might already have been migrated) so that page | |
1187 | * migration is sure to notice its raised count. | |
1188 | * It would be more elegant to return stable_node | |
1189 | * than kpage, but that involves more changes. | |
1190 | */ | |
1191 | tree_page = get_ksm_page(stable_node, true); | |
4146d2d6 | 1192 | if (tree_page) { |
c8d6553b | 1193 | unlock_page(tree_page); |
4146d2d6 HD |
1194 | if (get_kpfn_nid(stable_node->kpfn) != |
1195 | NUMA(stable_node->nid)) { | |
1196 | put_page(tree_page); | |
1197 | goto replace; | |
1198 | } | |
1199 | return tree_page; | |
1200 | } | |
1201 | /* | |
1202 | * There is now a place for page_node, but the tree may | |
1203 | * have been rebalanced, so re-evaluate parent and new. | |
1204 | */ | |
1205 | if (page_node) | |
1206 | goto again; | |
1207 | return NULL; | |
c8d6553b | 1208 | } |
31dbd01f IE |
1209 | } |
1210 | ||
4146d2d6 HD |
1211 | if (!page_node) |
1212 | return NULL; | |
1213 | ||
1214 | list_del(&page_node->list); | |
1215 | DO_NUMA(page_node->nid = nid); | |
1216 | rb_link_node(&page_node->node, parent, new); | |
1217 | rb_insert_color(&page_node->node, &root_stable_tree[nid]); | |
1218 | get_page(page); | |
1219 | return page; | |
1220 | ||
1221 | replace: | |
1222 | if (page_node) { | |
1223 | list_del(&page_node->list); | |
1224 | DO_NUMA(page_node->nid = nid); | |
1225 | rb_replace_node(&stable_node->node, | |
1226 | &page_node->node, &root_stable_tree[nid]); | |
1227 | get_page(page); | |
1228 | } else { | |
1229 | rb_erase(&stable_node->node, &root_stable_tree[nid]); | |
1230 | page = NULL; | |
1231 | } | |
1232 | stable_node->head = &migrate_nodes; | |
1233 | list_add(&stable_node->list, stable_node->head); | |
1234 | return page; | |
31dbd01f IE |
1235 | } |
1236 | ||
1237 | /* | |
e850dcf5 | 1238 | * stable_tree_insert - insert stable tree node pointing to new ksm page |
31dbd01f IE |
1239 | * into the stable tree. |
1240 | * | |
7b6ba2c7 HD |
1241 | * This function returns the stable tree node just allocated on success, |
1242 | * NULL otherwise. | |
31dbd01f | 1243 | */ |
7b6ba2c7 | 1244 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f | 1245 | { |
90bd6fd3 PH |
1246 | int nid; |
1247 | unsigned long kpfn; | |
1248 | struct rb_node **new; | |
31dbd01f | 1249 | struct rb_node *parent = NULL; |
7b6ba2c7 | 1250 | struct stable_node *stable_node; |
31dbd01f | 1251 | |
90bd6fd3 PH |
1252 | kpfn = page_to_pfn(kpage); |
1253 | nid = get_kpfn_nid(kpfn); | |
1254 | new = &root_stable_tree[nid].rb_node; | |
1255 | ||
31dbd01f | 1256 | while (*new) { |
4035c07a | 1257 | struct page *tree_page; |
31dbd01f IE |
1258 | int ret; |
1259 | ||
08beca44 | 1260 | cond_resched(); |
7b6ba2c7 | 1261 | stable_node = rb_entry(*new, struct stable_node, node); |
8aafa6a4 | 1262 | tree_page = get_ksm_page(stable_node, false); |
4035c07a HD |
1263 | if (!tree_page) |
1264 | return NULL; | |
31dbd01f | 1265 | |
4035c07a HD |
1266 | ret = memcmp_pages(kpage, tree_page); |
1267 | put_page(tree_page); | |
31dbd01f IE |
1268 | |
1269 | parent = *new; | |
1270 | if (ret < 0) | |
1271 | new = &parent->rb_left; | |
1272 | else if (ret > 0) | |
1273 | new = &parent->rb_right; | |
1274 | else { | |
1275 | /* | |
1276 | * It is not a bug that stable_tree_search() didn't | |
1277 | * find this node: because at that time our page was | |
1278 | * not yet write-protected, so may have changed since. | |
1279 | */ | |
1280 | return NULL; | |
1281 | } | |
1282 | } | |
1283 | ||
7b6ba2c7 HD |
1284 | stable_node = alloc_stable_node(); |
1285 | if (!stable_node) | |
1286 | return NULL; | |
31dbd01f | 1287 | |
7b6ba2c7 | 1288 | INIT_HLIST_HEAD(&stable_node->hlist); |
90bd6fd3 | 1289 | stable_node->kpfn = kpfn; |
08beca44 | 1290 | set_page_stable_node(kpage, stable_node); |
4146d2d6 | 1291 | DO_NUMA(stable_node->nid = nid); |
e850dcf5 HD |
1292 | rb_link_node(&stable_node->node, parent, new); |
1293 | rb_insert_color(&stable_node->node, &root_stable_tree[nid]); | |
08beca44 | 1294 | |
7b6ba2c7 | 1295 | return stable_node; |
31dbd01f IE |
1296 | } |
1297 | ||
1298 | /* | |
8dd3557a HD |
1299 | * unstable_tree_search_insert - search for identical page, |
1300 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
1301 | * |
1302 | * This function searches for a page in the unstable tree identical to the | |
1303 | * page currently being scanned; and if no identical page is found in the | |
1304 | * tree, we insert rmap_item as a new object into the unstable tree. | |
1305 | * | |
1306 | * This function returns pointer to rmap_item found to be identical | |
1307 | * to the currently scanned page, NULL otherwise. | |
1308 | * | |
1309 | * This function does both searching and inserting, because they share | |
1310 | * the same walking algorithm in an rbtree. | |
1311 | */ | |
8dd3557a HD |
1312 | static |
1313 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
1314 | struct page *page, | |
1315 | struct page **tree_pagep) | |
31dbd01f | 1316 | { |
90bd6fd3 PH |
1317 | struct rb_node **new; |
1318 | struct rb_root *root; | |
31dbd01f | 1319 | struct rb_node *parent = NULL; |
90bd6fd3 PH |
1320 | int nid; |
1321 | ||
1322 | nid = get_kpfn_nid(page_to_pfn(page)); | |
1323 | root = &root_unstable_tree[nid]; | |
1324 | new = &root->rb_node; | |
31dbd01f IE |
1325 | |
1326 | while (*new) { | |
1327 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 1328 | struct page *tree_page; |
31dbd01f IE |
1329 | int ret; |
1330 | ||
d178f27f | 1331 | cond_resched(); |
31dbd01f | 1332 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a | 1333 | tree_page = get_mergeable_page(tree_rmap_item); |
22eccdd7 | 1334 | if (IS_ERR_OR_NULL(tree_page)) |
31dbd01f IE |
1335 | return NULL; |
1336 | ||
1337 | /* | |
8dd3557a | 1338 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1339 | */ |
8dd3557a HD |
1340 | if (page == tree_page) { |
1341 | put_page(tree_page); | |
31dbd01f IE |
1342 | return NULL; |
1343 | } | |
1344 | ||
8dd3557a | 1345 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1346 | |
1347 | parent = *new; | |
1348 | if (ret < 0) { | |
8dd3557a | 1349 | put_page(tree_page); |
31dbd01f IE |
1350 | new = &parent->rb_left; |
1351 | } else if (ret > 0) { | |
8dd3557a | 1352 | put_page(tree_page); |
31dbd01f | 1353 | new = &parent->rb_right; |
b599cbdf HD |
1354 | } else if (!ksm_merge_across_nodes && |
1355 | page_to_nid(tree_page) != nid) { | |
1356 | /* | |
1357 | * If tree_page has been migrated to another NUMA node, | |
1358 | * it will be flushed out and put in the right unstable | |
1359 | * tree next time: only merge with it when across_nodes. | |
1360 | */ | |
1361 | put_page(tree_page); | |
1362 | return NULL; | |
31dbd01f | 1363 | } else { |
8dd3557a | 1364 | *tree_pagep = tree_page; |
31dbd01f IE |
1365 | return tree_rmap_item; |
1366 | } | |
1367 | } | |
1368 | ||
7b6ba2c7 | 1369 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f | 1370 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
e850dcf5 | 1371 | DO_NUMA(rmap_item->nid = nid); |
31dbd01f | 1372 | rb_link_node(&rmap_item->node, parent, new); |
90bd6fd3 | 1373 | rb_insert_color(&rmap_item->node, root); |
31dbd01f | 1374 | |
473b0ce4 | 1375 | ksm_pages_unshared++; |
31dbd01f IE |
1376 | return NULL; |
1377 | } | |
1378 | ||
1379 | /* | |
1380 | * stable_tree_append - add another rmap_item to the linked list of | |
1381 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1382 | * the same ksm page. | |
1383 | */ | |
1384 | static void stable_tree_append(struct rmap_item *rmap_item, | |
7b6ba2c7 | 1385 | struct stable_node *stable_node) |
31dbd01f | 1386 | { |
7b6ba2c7 | 1387 | rmap_item->head = stable_node; |
31dbd01f | 1388 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1389 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1390 | |
7b6ba2c7 HD |
1391 | if (rmap_item->hlist.next) |
1392 | ksm_pages_sharing++; | |
1393 | else | |
1394 | ksm_pages_shared++; | |
31dbd01f IE |
1395 | } |
1396 | ||
1397 | /* | |
81464e30 HD |
1398 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1399 | * if not, compare checksum to previous and if it's the same, see if page can | |
1400 | * be inserted into the unstable tree, or merged with a page already there and | |
1401 | * both transferred to the stable tree. | |
31dbd01f IE |
1402 | * |
1403 | * @page: the page that we are searching identical page to. | |
1404 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1405 | */ | |
1406 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1407 | { | |
31dbd01f | 1408 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1409 | struct page *tree_page = NULL; |
7b6ba2c7 | 1410 | struct stable_node *stable_node; |
8dd3557a | 1411 | struct page *kpage; |
31dbd01f IE |
1412 | unsigned int checksum; |
1413 | int err; | |
1414 | ||
4146d2d6 HD |
1415 | stable_node = page_stable_node(page); |
1416 | if (stable_node) { | |
1417 | if (stable_node->head != &migrate_nodes && | |
1418 | get_kpfn_nid(stable_node->kpfn) != NUMA(stable_node->nid)) { | |
1419 | rb_erase(&stable_node->node, | |
1420 | &root_stable_tree[NUMA(stable_node->nid)]); | |
1421 | stable_node->head = &migrate_nodes; | |
1422 | list_add(&stable_node->list, stable_node->head); | |
1423 | } | |
1424 | if (stable_node->head != &migrate_nodes && | |
1425 | rmap_item->head == stable_node) | |
1426 | return; | |
1427 | } | |
31dbd01f IE |
1428 | |
1429 | /* We first start with searching the page inside the stable tree */ | |
62b61f61 | 1430 | kpage = stable_tree_search(page); |
4146d2d6 HD |
1431 | if (kpage == page && rmap_item->head == stable_node) { |
1432 | put_page(kpage); | |
1433 | return; | |
1434 | } | |
1435 | ||
1436 | remove_rmap_item_from_tree(rmap_item); | |
1437 | ||
62b61f61 | 1438 | if (kpage) { |
08beca44 | 1439 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
31dbd01f IE |
1440 | if (!err) { |
1441 | /* | |
1442 | * The page was successfully merged: | |
1443 | * add its rmap_item to the stable tree. | |
1444 | */ | |
5ad64688 | 1445 | lock_page(kpage); |
62b61f61 | 1446 | stable_tree_append(rmap_item, page_stable_node(kpage)); |
5ad64688 | 1447 | unlock_page(kpage); |
31dbd01f | 1448 | } |
8dd3557a | 1449 | put_page(kpage); |
31dbd01f IE |
1450 | return; |
1451 | } | |
1452 | ||
1453 | /* | |
4035c07a HD |
1454 | * If the hash value of the page has changed from the last time |
1455 | * we calculated it, this page is changing frequently: therefore we | |
1456 | * don't want to insert it in the unstable tree, and we don't want | |
1457 | * to waste our time searching for something identical to it there. | |
31dbd01f IE |
1458 | */ |
1459 | checksum = calc_checksum(page); | |
1460 | if (rmap_item->oldchecksum != checksum) { | |
1461 | rmap_item->oldchecksum = checksum; | |
1462 | return; | |
1463 | } | |
1464 | ||
8dd3557a HD |
1465 | tree_rmap_item = |
1466 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1467 | if (tree_rmap_item) { |
8dd3557a HD |
1468 | kpage = try_to_merge_two_pages(rmap_item, page, |
1469 | tree_rmap_item, tree_page); | |
1470 | put_page(tree_page); | |
31dbd01f IE |
1471 | /* |
1472 | * As soon as we merge this page, we want to remove the | |
1473 | * rmap_item of the page we have merged with from the unstable | |
1474 | * tree, and insert it instead as new node in the stable tree. | |
1475 | */ | |
8dd3557a | 1476 | if (kpage) { |
93d17715 | 1477 | remove_rmap_item_from_tree(tree_rmap_item); |
473b0ce4 | 1478 | |
5ad64688 | 1479 | lock_page(kpage); |
7b6ba2c7 HD |
1480 | stable_node = stable_tree_insert(kpage); |
1481 | if (stable_node) { | |
1482 | stable_tree_append(tree_rmap_item, stable_node); | |
1483 | stable_tree_append(rmap_item, stable_node); | |
1484 | } | |
5ad64688 | 1485 | unlock_page(kpage); |
7b6ba2c7 | 1486 | |
31dbd01f IE |
1487 | /* |
1488 | * If we fail to insert the page into the stable tree, | |
1489 | * we will have 2 virtual addresses that are pointing | |
1490 | * to a ksm page left outside the stable tree, | |
1491 | * in which case we need to break_cow on both. | |
1492 | */ | |
7b6ba2c7 | 1493 | if (!stable_node) { |
8dd3557a HD |
1494 | break_cow(tree_rmap_item); |
1495 | break_cow(rmap_item); | |
31dbd01f IE |
1496 | } |
1497 | } | |
31dbd01f IE |
1498 | } |
1499 | } | |
1500 | ||
1501 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1502 | struct rmap_item **rmap_list, |
31dbd01f IE |
1503 | unsigned long addr) |
1504 | { | |
1505 | struct rmap_item *rmap_item; | |
1506 | ||
6514d511 HD |
1507 | while (*rmap_list) { |
1508 | rmap_item = *rmap_list; | |
93d17715 | 1509 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1510 | return rmap_item; |
31dbd01f IE |
1511 | if (rmap_item->address > addr) |
1512 | break; | |
6514d511 | 1513 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1514 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1515 | free_rmap_item(rmap_item); |
1516 | } | |
1517 | ||
1518 | rmap_item = alloc_rmap_item(); | |
1519 | if (rmap_item) { | |
1520 | /* It has already been zeroed */ | |
1521 | rmap_item->mm = mm_slot->mm; | |
1522 | rmap_item->address = addr; | |
6514d511 HD |
1523 | rmap_item->rmap_list = *rmap_list; |
1524 | *rmap_list = rmap_item; | |
31dbd01f IE |
1525 | } |
1526 | return rmap_item; | |
1527 | } | |
1528 | ||
1529 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1530 | { | |
1531 | struct mm_struct *mm; | |
1532 | struct mm_slot *slot; | |
1533 | struct vm_area_struct *vma; | |
1534 | struct rmap_item *rmap_item; | |
90bd6fd3 | 1535 | int nid; |
31dbd01f IE |
1536 | |
1537 | if (list_empty(&ksm_mm_head.mm_list)) | |
1538 | return NULL; | |
1539 | ||
1540 | slot = ksm_scan.mm_slot; | |
1541 | if (slot == &ksm_mm_head) { | |
2919bfd0 HD |
1542 | /* |
1543 | * A number of pages can hang around indefinitely on per-cpu | |
1544 | * pagevecs, raised page count preventing write_protect_page | |
1545 | * from merging them. Though it doesn't really matter much, | |
1546 | * it is puzzling to see some stuck in pages_volatile until | |
1547 | * other activity jostles them out, and they also prevented | |
1548 | * LTP's KSM test from succeeding deterministically; so drain | |
1549 | * them here (here rather than on entry to ksm_do_scan(), | |
1550 | * so we don't IPI too often when pages_to_scan is set low). | |
1551 | */ | |
1552 | lru_add_drain_all(); | |
1553 | ||
4146d2d6 HD |
1554 | /* |
1555 | * Whereas stale stable_nodes on the stable_tree itself | |
1556 | * get pruned in the regular course of stable_tree_search(), | |
1557 | * those moved out to the migrate_nodes list can accumulate: | |
1558 | * so prune them once before each full scan. | |
1559 | */ | |
1560 | if (!ksm_merge_across_nodes) { | |
1561 | struct stable_node *stable_node; | |
1562 | struct list_head *this, *next; | |
1563 | struct page *page; | |
1564 | ||
1565 | list_for_each_safe(this, next, &migrate_nodes) { | |
1566 | stable_node = list_entry(this, | |
1567 | struct stable_node, list); | |
1568 | page = get_ksm_page(stable_node, false); | |
1569 | if (page) | |
1570 | put_page(page); | |
1571 | cond_resched(); | |
1572 | } | |
1573 | } | |
1574 | ||
90bd6fd3 PH |
1575 | for (nid = 0; nid < nr_node_ids; nid++) |
1576 | root_unstable_tree[nid] = RB_ROOT; | |
31dbd01f IE |
1577 | |
1578 | spin_lock(&ksm_mmlist_lock); | |
1579 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1580 | ksm_scan.mm_slot = slot; | |
1581 | spin_unlock(&ksm_mmlist_lock); | |
2b472611 HD |
1582 | /* |
1583 | * Although we tested list_empty() above, a racing __ksm_exit | |
1584 | * of the last mm on the list may have removed it since then. | |
1585 | */ | |
1586 | if (slot == &ksm_mm_head) | |
1587 | return NULL; | |
31dbd01f IE |
1588 | next_mm: |
1589 | ksm_scan.address = 0; | |
6514d511 | 1590 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1591 | } |
1592 | ||
1593 | mm = slot->mm; | |
1594 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1595 | if (ksm_test_exit(mm)) |
1596 | vma = NULL; | |
1597 | else | |
1598 | vma = find_vma(mm, ksm_scan.address); | |
1599 | ||
1600 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1601 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1602 | continue; | |
1603 | if (ksm_scan.address < vma->vm_start) | |
1604 | ksm_scan.address = vma->vm_start; | |
1605 | if (!vma->anon_vma) | |
1606 | ksm_scan.address = vma->vm_end; | |
1607 | ||
1608 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1609 | if (ksm_test_exit(mm)) |
1610 | break; | |
31dbd01f | 1611 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
21ae5b01 AA |
1612 | if (IS_ERR_OR_NULL(*page)) { |
1613 | ksm_scan.address += PAGE_SIZE; | |
1614 | cond_resched(); | |
1615 | continue; | |
1616 | } | |
29ad768c AA |
1617 | if (PageAnon(*page) || |
1618 | page_trans_compound_anon(*page)) { | |
31dbd01f IE |
1619 | flush_anon_page(vma, *page, ksm_scan.address); |
1620 | flush_dcache_page(*page); | |
1621 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1622 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1623 | if (rmap_item) { |
6514d511 HD |
1624 | ksm_scan.rmap_list = |
1625 | &rmap_item->rmap_list; | |
31dbd01f IE |
1626 | ksm_scan.address += PAGE_SIZE; |
1627 | } else | |
1628 | put_page(*page); | |
1629 | up_read(&mm->mmap_sem); | |
1630 | return rmap_item; | |
1631 | } | |
21ae5b01 | 1632 | put_page(*page); |
31dbd01f IE |
1633 | ksm_scan.address += PAGE_SIZE; |
1634 | cond_resched(); | |
1635 | } | |
1636 | } | |
1637 | ||
9ba69294 HD |
1638 | if (ksm_test_exit(mm)) { |
1639 | ksm_scan.address = 0; | |
6514d511 | 1640 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1641 | } |
31dbd01f IE |
1642 | /* |
1643 | * Nuke all the rmap_items that are above this current rmap: | |
1644 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1645 | */ | |
6514d511 | 1646 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1647 | |
1648 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1649 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1650 | struct mm_slot, mm_list); | |
1651 | if (ksm_scan.address == 0) { | |
1652 | /* | |
1653 | * We've completed a full scan of all vmas, holding mmap_sem | |
1654 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1655 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1656 | * This applies either when cleaning up after __ksm_exit |
1657 | * (but beware: we can reach here even before __ksm_exit), | |
1658 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1659 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 | 1660 | */ |
4ca3a69b | 1661 | hash_del(&slot->link); |
cd551f97 | 1662 | list_del(&slot->mm_list); |
9ba69294 HD |
1663 | spin_unlock(&ksm_mmlist_lock); |
1664 | ||
cd551f97 HD |
1665 | free_mm_slot(slot); |
1666 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1667 | up_read(&mm->mmap_sem); |
1668 | mmdrop(mm); | |
1669 | } else { | |
1670 | spin_unlock(&ksm_mmlist_lock); | |
1671 | up_read(&mm->mmap_sem); | |
cd551f97 | 1672 | } |
31dbd01f IE |
1673 | |
1674 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1675 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1676 | if (slot != &ksm_mm_head) |
1677 | goto next_mm; | |
1678 | ||
31dbd01f IE |
1679 | ksm_scan.seqnr++; |
1680 | return NULL; | |
1681 | } | |
1682 | ||
1683 | /** | |
1684 | * ksm_do_scan - the ksm scanner main worker function. | |
1685 | * @scan_npages - number of pages we want to scan before we return. | |
1686 | */ | |
1687 | static void ksm_do_scan(unsigned int scan_npages) | |
1688 | { | |
1689 | struct rmap_item *rmap_item; | |
22eccdd7 | 1690 | struct page *uninitialized_var(page); |
31dbd01f | 1691 | |
878aee7d | 1692 | while (scan_npages-- && likely(!freezing(current))) { |
31dbd01f IE |
1693 | cond_resched(); |
1694 | rmap_item = scan_get_next_rmap_item(&page); | |
1695 | if (!rmap_item) | |
1696 | return; | |
4146d2d6 | 1697 | cmp_and_merge_page(page, rmap_item); |
31dbd01f IE |
1698 | put_page(page); |
1699 | } | |
1700 | } | |
1701 | ||
6e158384 HD |
1702 | static int ksmd_should_run(void) |
1703 | { | |
1704 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1705 | } | |
1706 | ||
31dbd01f IE |
1707 | static int ksm_scan_thread(void *nothing) |
1708 | { | |
878aee7d | 1709 | set_freezable(); |
339aa624 | 1710 | set_user_nice(current, 5); |
31dbd01f IE |
1711 | |
1712 | while (!kthread_should_stop()) { | |
6e158384 | 1713 | mutex_lock(&ksm_thread_mutex); |
ef4d43a8 | 1714 | wait_while_offlining(); |
6e158384 | 1715 | if (ksmd_should_run()) |
31dbd01f | 1716 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1717 | mutex_unlock(&ksm_thread_mutex); |
1718 | ||
878aee7d AA |
1719 | try_to_freeze(); |
1720 | ||
6e158384 | 1721 | if (ksmd_should_run()) { |
31dbd01f IE |
1722 | schedule_timeout_interruptible( |
1723 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1724 | } else { | |
878aee7d | 1725 | wait_event_freezable(ksm_thread_wait, |
6e158384 | 1726 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1727 | } |
1728 | } | |
1729 | return 0; | |
1730 | } | |
1731 | ||
f8af4da3 HD |
1732 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1733 | unsigned long end, int advice, unsigned long *vm_flags) | |
1734 | { | |
1735 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1736 | int err; |
f8af4da3 HD |
1737 | |
1738 | switch (advice) { | |
1739 | case MADV_MERGEABLE: | |
1740 | /* | |
1741 | * Be somewhat over-protective for now! | |
1742 | */ | |
1743 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1744 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
314e51b9 | 1745 | VM_HUGETLB | VM_NONLINEAR | VM_MIXEDMAP)) |
f8af4da3 HD |
1746 | return 0; /* just ignore the advice */ |
1747 | ||
cc2383ec KK |
1748 | #ifdef VM_SAO |
1749 | if (*vm_flags & VM_SAO) | |
1750 | return 0; | |
1751 | #endif | |
1752 | ||
d952b791 HD |
1753 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1754 | err = __ksm_enter(mm); | |
1755 | if (err) | |
1756 | return err; | |
1757 | } | |
f8af4da3 HD |
1758 | |
1759 | *vm_flags |= VM_MERGEABLE; | |
1760 | break; | |
1761 | ||
1762 | case MADV_UNMERGEABLE: | |
1763 | if (!(*vm_flags & VM_MERGEABLE)) | |
1764 | return 0; /* just ignore the advice */ | |
1765 | ||
d952b791 HD |
1766 | if (vma->anon_vma) { |
1767 | err = unmerge_ksm_pages(vma, start, end); | |
1768 | if (err) | |
1769 | return err; | |
1770 | } | |
f8af4da3 HD |
1771 | |
1772 | *vm_flags &= ~VM_MERGEABLE; | |
1773 | break; | |
1774 | } | |
1775 | ||
1776 | return 0; | |
1777 | } | |
1778 | ||
1779 | int __ksm_enter(struct mm_struct *mm) | |
1780 | { | |
6e158384 HD |
1781 | struct mm_slot *mm_slot; |
1782 | int needs_wakeup; | |
1783 | ||
1784 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1785 | if (!mm_slot) |
1786 | return -ENOMEM; | |
1787 | ||
6e158384 HD |
1788 | /* Check ksm_run too? Would need tighter locking */ |
1789 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1790 | ||
31dbd01f IE |
1791 | spin_lock(&ksm_mmlist_lock); |
1792 | insert_to_mm_slots_hash(mm, mm_slot); | |
1793 | /* | |
cbf86cfe HD |
1794 | * When KSM_RUN_MERGE (or KSM_RUN_STOP), |
1795 | * insert just behind the scanning cursor, to let the area settle | |
31dbd01f IE |
1796 | * down a little; when fork is followed by immediate exec, we don't |
1797 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
cbf86cfe HD |
1798 | * |
1799 | * But when KSM_RUN_UNMERGE, it's important to insert ahead of its | |
1800 | * scanning cursor, otherwise KSM pages in newly forked mms will be | |
1801 | * missed: then we might as well insert at the end of the list. | |
31dbd01f | 1802 | */ |
cbf86cfe HD |
1803 | if (ksm_run & KSM_RUN_UNMERGE) |
1804 | list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); | |
1805 | else | |
1806 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
31dbd01f IE |
1807 | spin_unlock(&ksm_mmlist_lock); |
1808 | ||
f8af4da3 | 1809 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1810 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1811 | |
1812 | if (needs_wakeup) | |
1813 | wake_up_interruptible(&ksm_thread_wait); | |
1814 | ||
f8af4da3 HD |
1815 | return 0; |
1816 | } | |
1817 | ||
1c2fb7a4 | 1818 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1819 | { |
cd551f97 | 1820 | struct mm_slot *mm_slot; |
9ba69294 | 1821 | int easy_to_free = 0; |
cd551f97 | 1822 | |
31dbd01f | 1823 | /* |
9ba69294 HD |
1824 | * This process is exiting: if it's straightforward (as is the |
1825 | * case when ksmd was never running), free mm_slot immediately. | |
1826 | * But if it's at the cursor or has rmap_items linked to it, use | |
1827 | * mmap_sem to synchronize with any break_cows before pagetables | |
1828 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1829 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1830 | */ |
9ba69294 | 1831 | |
cd551f97 HD |
1832 | spin_lock(&ksm_mmlist_lock); |
1833 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1834 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1835 | if (!mm_slot->rmap_list) { |
4ca3a69b | 1836 | hash_del(&mm_slot->link); |
9ba69294 HD |
1837 | list_del(&mm_slot->mm_list); |
1838 | easy_to_free = 1; | |
1839 | } else { | |
1840 | list_move(&mm_slot->mm_list, | |
1841 | &ksm_scan.mm_slot->mm_list); | |
1842 | } | |
cd551f97 | 1843 | } |
cd551f97 HD |
1844 | spin_unlock(&ksm_mmlist_lock); |
1845 | ||
9ba69294 HD |
1846 | if (easy_to_free) { |
1847 | free_mm_slot(mm_slot); | |
1848 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1849 | mmdrop(mm); | |
1850 | } else if (mm_slot) { | |
9ba69294 HD |
1851 | down_write(&mm->mmap_sem); |
1852 | up_write(&mm->mmap_sem); | |
9ba69294 | 1853 | } |
31dbd01f IE |
1854 | } |
1855 | ||
cbf86cfe | 1856 | struct page *ksm_might_need_to_copy(struct page *page, |
5ad64688 HD |
1857 | struct vm_area_struct *vma, unsigned long address) |
1858 | { | |
cbf86cfe | 1859 | struct anon_vma *anon_vma = page_anon_vma(page); |
5ad64688 HD |
1860 | struct page *new_page; |
1861 | ||
cbf86cfe HD |
1862 | if (PageKsm(page)) { |
1863 | if (page_stable_node(page) && | |
1864 | !(ksm_run & KSM_RUN_UNMERGE)) | |
1865 | return page; /* no need to copy it */ | |
1866 | } else if (!anon_vma) { | |
1867 | return page; /* no need to copy it */ | |
1868 | } else if (anon_vma->root == vma->anon_vma->root && | |
1869 | page->index == linear_page_index(vma, address)) { | |
1870 | return page; /* still no need to copy it */ | |
1871 | } | |
1872 | if (!PageUptodate(page)) | |
1873 | return page; /* let do_swap_page report the error */ | |
1874 | ||
5ad64688 HD |
1875 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
1876 | if (new_page) { | |
1877 | copy_user_highpage(new_page, page, address, vma); | |
1878 | ||
1879 | SetPageDirty(new_page); | |
1880 | __SetPageUptodate(new_page); | |
5ad64688 | 1881 | __set_page_locked(new_page); |
5ad64688 HD |
1882 | } |
1883 | ||
5ad64688 HD |
1884 | return new_page; |
1885 | } | |
1886 | ||
1887 | int page_referenced_ksm(struct page *page, struct mem_cgroup *memcg, | |
1888 | unsigned long *vm_flags) | |
1889 | { | |
1890 | struct stable_node *stable_node; | |
1891 | struct rmap_item *rmap_item; | |
1892 | struct hlist_node *hlist; | |
1893 | unsigned int mapcount = page_mapcount(page); | |
1894 | int referenced = 0; | |
db114b83 | 1895 | int search_new_forks = 0; |
5ad64688 HD |
1896 | |
1897 | VM_BUG_ON(!PageKsm(page)); | |
1898 | VM_BUG_ON(!PageLocked(page)); | |
1899 | ||
1900 | stable_node = page_stable_node(page); | |
1901 | if (!stable_node) | |
1902 | return 0; | |
db114b83 | 1903 | again: |
5ad64688 | 1904 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { |
db114b83 | 1905 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 1906 | struct anon_vma_chain *vmac; |
db114b83 | 1907 | struct vm_area_struct *vma; |
5ad64688 | 1908 | |
b6b19f25 | 1909 | anon_vma_lock_read(anon_vma); |
bf181b9f ML |
1910 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
1911 | 0, ULONG_MAX) { | |
5beb4930 | 1912 | vma = vmac->vma; |
db114b83 HD |
1913 | if (rmap_item->address < vma->vm_start || |
1914 | rmap_item->address >= vma->vm_end) | |
1915 | continue; | |
1916 | /* | |
1917 | * Initially we examine only the vma which covers this | |
1918 | * rmap_item; but later, if there is still work to do, | |
1919 | * we examine covering vmas in other mms: in case they | |
1920 | * were forked from the original since ksmd passed. | |
1921 | */ | |
1922 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
1923 | continue; | |
1924 | ||
1925 | if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) | |
1926 | continue; | |
5ad64688 | 1927 | |
db114b83 | 1928 | referenced += page_referenced_one(page, vma, |
5ad64688 | 1929 | rmap_item->address, &mapcount, vm_flags); |
db114b83 HD |
1930 | if (!search_new_forks || !mapcount) |
1931 | break; | |
1932 | } | |
b6b19f25 | 1933 | anon_vma_unlock_read(anon_vma); |
5ad64688 HD |
1934 | if (!mapcount) |
1935 | goto out; | |
1936 | } | |
db114b83 HD |
1937 | if (!search_new_forks++) |
1938 | goto again; | |
5ad64688 | 1939 | out: |
5ad64688 HD |
1940 | return referenced; |
1941 | } | |
1942 | ||
1943 | int try_to_unmap_ksm(struct page *page, enum ttu_flags flags) | |
1944 | { | |
1945 | struct stable_node *stable_node; | |
1946 | struct hlist_node *hlist; | |
1947 | struct rmap_item *rmap_item; | |
1948 | int ret = SWAP_AGAIN; | |
db114b83 | 1949 | int search_new_forks = 0; |
5ad64688 HD |
1950 | |
1951 | VM_BUG_ON(!PageKsm(page)); | |
1952 | VM_BUG_ON(!PageLocked(page)); | |
1953 | ||
1954 | stable_node = page_stable_node(page); | |
1955 | if (!stable_node) | |
1956 | return SWAP_FAIL; | |
db114b83 | 1957 | again: |
5ad64688 | 1958 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { |
db114b83 | 1959 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 1960 | struct anon_vma_chain *vmac; |
db114b83 | 1961 | struct vm_area_struct *vma; |
5ad64688 | 1962 | |
b6b19f25 | 1963 | anon_vma_lock_read(anon_vma); |
bf181b9f ML |
1964 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
1965 | 0, ULONG_MAX) { | |
5beb4930 | 1966 | vma = vmac->vma; |
db114b83 HD |
1967 | if (rmap_item->address < vma->vm_start || |
1968 | rmap_item->address >= vma->vm_end) | |
1969 | continue; | |
1970 | /* | |
1971 | * Initially we examine only the vma which covers this | |
1972 | * rmap_item; but later, if there is still work to do, | |
1973 | * we examine covering vmas in other mms: in case they | |
1974 | * were forked from the original since ksmd passed. | |
1975 | */ | |
1976 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
1977 | continue; | |
1978 | ||
1979 | ret = try_to_unmap_one(page, vma, | |
1980 | rmap_item->address, flags); | |
1981 | if (ret != SWAP_AGAIN || !page_mapped(page)) { | |
b6b19f25 | 1982 | anon_vma_unlock_read(anon_vma); |
db114b83 HD |
1983 | goto out; |
1984 | } | |
1985 | } | |
b6b19f25 | 1986 | anon_vma_unlock_read(anon_vma); |
5ad64688 | 1987 | } |
db114b83 HD |
1988 | if (!search_new_forks++) |
1989 | goto again; | |
5ad64688 | 1990 | out: |
5ad64688 HD |
1991 | return ret; |
1992 | } | |
1993 | ||
e9995ef9 HD |
1994 | #ifdef CONFIG_MIGRATION |
1995 | int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *, | |
1996 | struct vm_area_struct *, unsigned long, void *), void *arg) | |
1997 | { | |
1998 | struct stable_node *stable_node; | |
1999 | struct hlist_node *hlist; | |
2000 | struct rmap_item *rmap_item; | |
2001 | int ret = SWAP_AGAIN; | |
2002 | int search_new_forks = 0; | |
2003 | ||
2004 | VM_BUG_ON(!PageKsm(page)); | |
2005 | VM_BUG_ON(!PageLocked(page)); | |
2006 | ||
2007 | stable_node = page_stable_node(page); | |
2008 | if (!stable_node) | |
2009 | return ret; | |
2010 | again: | |
2011 | hlist_for_each_entry(rmap_item, hlist, &stable_node->hlist, hlist) { | |
2012 | struct anon_vma *anon_vma = rmap_item->anon_vma; | |
5beb4930 | 2013 | struct anon_vma_chain *vmac; |
e9995ef9 HD |
2014 | struct vm_area_struct *vma; |
2015 | ||
b6b19f25 | 2016 | anon_vma_lock_read(anon_vma); |
bf181b9f ML |
2017 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
2018 | 0, ULONG_MAX) { | |
5beb4930 | 2019 | vma = vmac->vma; |
e9995ef9 HD |
2020 | if (rmap_item->address < vma->vm_start || |
2021 | rmap_item->address >= vma->vm_end) | |
2022 | continue; | |
2023 | /* | |
2024 | * Initially we examine only the vma which covers this | |
2025 | * rmap_item; but later, if there is still work to do, | |
2026 | * we examine covering vmas in other mms: in case they | |
2027 | * were forked from the original since ksmd passed. | |
2028 | */ | |
2029 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
2030 | continue; | |
2031 | ||
2032 | ret = rmap_one(page, vma, rmap_item->address, arg); | |
2033 | if (ret != SWAP_AGAIN) { | |
b6b19f25 | 2034 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
2035 | goto out; |
2036 | } | |
2037 | } | |
b6b19f25 | 2038 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
2039 | } |
2040 | if (!search_new_forks++) | |
2041 | goto again; | |
2042 | out: | |
2043 | return ret; | |
2044 | } | |
2045 | ||
2046 | void ksm_migrate_page(struct page *newpage, struct page *oldpage) | |
2047 | { | |
2048 | struct stable_node *stable_node; | |
2049 | ||
2050 | VM_BUG_ON(!PageLocked(oldpage)); | |
2051 | VM_BUG_ON(!PageLocked(newpage)); | |
2052 | VM_BUG_ON(newpage->mapping != oldpage->mapping); | |
2053 | ||
2054 | stable_node = page_stable_node(newpage); | |
2055 | if (stable_node) { | |
62b61f61 HD |
2056 | VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage)); |
2057 | stable_node->kpfn = page_to_pfn(newpage); | |
c8d6553b HD |
2058 | /* |
2059 | * newpage->mapping was set in advance; now we need smp_wmb() | |
2060 | * to make sure that the new stable_node->kpfn is visible | |
2061 | * to get_ksm_page() before it can see that oldpage->mapping | |
2062 | * has gone stale (or that PageSwapCache has been cleared). | |
2063 | */ | |
2064 | smp_wmb(); | |
2065 | set_page_stable_node(oldpage, NULL); | |
e9995ef9 HD |
2066 | } |
2067 | } | |
2068 | #endif /* CONFIG_MIGRATION */ | |
2069 | ||
62b61f61 | 2070 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 HD |
2071 | static int just_wait(void *word) |
2072 | { | |
2073 | schedule(); | |
2074 | return 0; | |
2075 | } | |
2076 | ||
2077 | static void wait_while_offlining(void) | |
2078 | { | |
2079 | while (ksm_run & KSM_RUN_OFFLINE) { | |
2080 | mutex_unlock(&ksm_thread_mutex); | |
2081 | wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), | |
2082 | just_wait, TASK_UNINTERRUPTIBLE); | |
2083 | mutex_lock(&ksm_thread_mutex); | |
2084 | } | |
2085 | } | |
2086 | ||
ee0ea59c HD |
2087 | static void ksm_check_stable_tree(unsigned long start_pfn, |
2088 | unsigned long end_pfn) | |
62b61f61 | 2089 | { |
ee0ea59c | 2090 | struct stable_node *stable_node; |
4146d2d6 | 2091 | struct list_head *this, *next; |
62b61f61 | 2092 | struct rb_node *node; |
90bd6fd3 | 2093 | int nid; |
62b61f61 | 2094 | |
ee0ea59c HD |
2095 | for (nid = 0; nid < nr_node_ids; nid++) { |
2096 | node = rb_first(&root_stable_tree[nid]); | |
2097 | while (node) { | |
90bd6fd3 PH |
2098 | stable_node = rb_entry(node, struct stable_node, node); |
2099 | if (stable_node->kpfn >= start_pfn && | |
ee0ea59c HD |
2100 | stable_node->kpfn < end_pfn) { |
2101 | /* | |
2102 | * Don't get_ksm_page, page has already gone: | |
2103 | * which is why we keep kpfn instead of page* | |
2104 | */ | |
2105 | remove_node_from_stable_tree(stable_node); | |
2106 | node = rb_first(&root_stable_tree[nid]); | |
2107 | } else | |
2108 | node = rb_next(node); | |
2109 | cond_resched(); | |
90bd6fd3 | 2110 | } |
ee0ea59c | 2111 | } |
4146d2d6 HD |
2112 | list_for_each_safe(this, next, &migrate_nodes) { |
2113 | stable_node = list_entry(this, struct stable_node, list); | |
2114 | if (stable_node->kpfn >= start_pfn && | |
2115 | stable_node->kpfn < end_pfn) | |
2116 | remove_node_from_stable_tree(stable_node); | |
2117 | cond_resched(); | |
2118 | } | |
62b61f61 HD |
2119 | } |
2120 | ||
2121 | static int ksm_memory_callback(struct notifier_block *self, | |
2122 | unsigned long action, void *arg) | |
2123 | { | |
2124 | struct memory_notify *mn = arg; | |
62b61f61 HD |
2125 | |
2126 | switch (action) { | |
2127 | case MEM_GOING_OFFLINE: | |
2128 | /* | |
ef4d43a8 HD |
2129 | * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() |
2130 | * and remove_all_stable_nodes() while memory is going offline: | |
2131 | * it is unsafe for them to touch the stable tree at this time. | |
2132 | * But unmerge_ksm_pages(), rmap lookups and other entry points | |
2133 | * which do not need the ksm_thread_mutex are all safe. | |
62b61f61 | 2134 | */ |
ef4d43a8 HD |
2135 | mutex_lock(&ksm_thread_mutex); |
2136 | ksm_run |= KSM_RUN_OFFLINE; | |
2137 | mutex_unlock(&ksm_thread_mutex); | |
62b61f61 HD |
2138 | break; |
2139 | ||
2140 | case MEM_OFFLINE: | |
2141 | /* | |
2142 | * Most of the work is done by page migration; but there might | |
2143 | * be a few stable_nodes left over, still pointing to struct | |
ee0ea59c HD |
2144 | * pages which have been offlined: prune those from the tree, |
2145 | * otherwise get_ksm_page() might later try to access a | |
2146 | * non-existent struct page. | |
62b61f61 | 2147 | */ |
ee0ea59c HD |
2148 | ksm_check_stable_tree(mn->start_pfn, |
2149 | mn->start_pfn + mn->nr_pages); | |
62b61f61 HD |
2150 | /* fallthrough */ |
2151 | ||
2152 | case MEM_CANCEL_OFFLINE: | |
ef4d43a8 HD |
2153 | mutex_lock(&ksm_thread_mutex); |
2154 | ksm_run &= ~KSM_RUN_OFFLINE; | |
62b61f61 | 2155 | mutex_unlock(&ksm_thread_mutex); |
ef4d43a8 HD |
2156 | |
2157 | smp_mb(); /* wake_up_bit advises this */ | |
2158 | wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); | |
62b61f61 HD |
2159 | break; |
2160 | } | |
2161 | return NOTIFY_OK; | |
2162 | } | |
ef4d43a8 HD |
2163 | #else |
2164 | static void wait_while_offlining(void) | |
2165 | { | |
2166 | } | |
62b61f61 HD |
2167 | #endif /* CONFIG_MEMORY_HOTREMOVE */ |
2168 | ||
2ffd8679 HD |
2169 | #ifdef CONFIG_SYSFS |
2170 | /* | |
2171 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
2172 | */ | |
2173 | ||
31dbd01f IE |
2174 | #define KSM_ATTR_RO(_name) \ |
2175 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
2176 | #define KSM_ATTR(_name) \ | |
2177 | static struct kobj_attribute _name##_attr = \ | |
2178 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
2179 | ||
2180 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
2181 | struct kobj_attribute *attr, char *buf) | |
2182 | { | |
2183 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
2184 | } | |
2185 | ||
2186 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
2187 | struct kobj_attribute *attr, | |
2188 | const char *buf, size_t count) | |
2189 | { | |
2190 | unsigned long msecs; | |
2191 | int err; | |
2192 | ||
2193 | err = strict_strtoul(buf, 10, &msecs); | |
2194 | if (err || msecs > UINT_MAX) | |
2195 | return -EINVAL; | |
2196 | ||
2197 | ksm_thread_sleep_millisecs = msecs; | |
2198 | ||
2199 | return count; | |
2200 | } | |
2201 | KSM_ATTR(sleep_millisecs); | |
2202 | ||
2203 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
2204 | struct kobj_attribute *attr, char *buf) | |
2205 | { | |
2206 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
2207 | } | |
2208 | ||
2209 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
2210 | struct kobj_attribute *attr, | |
2211 | const char *buf, size_t count) | |
2212 | { | |
2213 | int err; | |
2214 | unsigned long nr_pages; | |
2215 | ||
2216 | err = strict_strtoul(buf, 10, &nr_pages); | |
2217 | if (err || nr_pages > UINT_MAX) | |
2218 | return -EINVAL; | |
2219 | ||
2220 | ksm_thread_pages_to_scan = nr_pages; | |
2221 | ||
2222 | return count; | |
2223 | } | |
2224 | KSM_ATTR(pages_to_scan); | |
2225 | ||
2226 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
2227 | char *buf) | |
2228 | { | |
ef4d43a8 | 2229 | return sprintf(buf, "%lu\n", ksm_run); |
31dbd01f IE |
2230 | } |
2231 | ||
2232 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
2233 | const char *buf, size_t count) | |
2234 | { | |
2235 | int err; | |
2236 | unsigned long flags; | |
2237 | ||
2238 | err = strict_strtoul(buf, 10, &flags); | |
2239 | if (err || flags > UINT_MAX) | |
2240 | return -EINVAL; | |
2241 | if (flags > KSM_RUN_UNMERGE) | |
2242 | return -EINVAL; | |
2243 | ||
2244 | /* | |
2245 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
2246 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
d0f209f6 HD |
2247 | * breaking COW to free the pages_shared (but leaves mm_slots |
2248 | * on the list for when ksmd may be set running again). | |
31dbd01f IE |
2249 | */ |
2250 | ||
2251 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2252 | wait_while_offlining(); |
31dbd01f IE |
2253 | if (ksm_run != flags) { |
2254 | ksm_run = flags; | |
d952b791 | 2255 | if (flags & KSM_RUN_UNMERGE) { |
e1e12d2f | 2256 | set_current_oom_origin(); |
d952b791 | 2257 | err = unmerge_and_remove_all_rmap_items(); |
e1e12d2f | 2258 | clear_current_oom_origin(); |
d952b791 HD |
2259 | if (err) { |
2260 | ksm_run = KSM_RUN_STOP; | |
2261 | count = err; | |
2262 | } | |
2263 | } | |
31dbd01f IE |
2264 | } |
2265 | mutex_unlock(&ksm_thread_mutex); | |
2266 | ||
2267 | if (flags & KSM_RUN_MERGE) | |
2268 | wake_up_interruptible(&ksm_thread_wait); | |
2269 | ||
2270 | return count; | |
2271 | } | |
2272 | KSM_ATTR(run); | |
2273 | ||
90bd6fd3 PH |
2274 | #ifdef CONFIG_NUMA |
2275 | static ssize_t merge_across_nodes_show(struct kobject *kobj, | |
2276 | struct kobj_attribute *attr, char *buf) | |
2277 | { | |
2278 | return sprintf(buf, "%u\n", ksm_merge_across_nodes); | |
2279 | } | |
2280 | ||
2281 | static ssize_t merge_across_nodes_store(struct kobject *kobj, | |
2282 | struct kobj_attribute *attr, | |
2283 | const char *buf, size_t count) | |
2284 | { | |
2285 | int err; | |
2286 | unsigned long knob; | |
2287 | ||
2288 | err = kstrtoul(buf, 10, &knob); | |
2289 | if (err) | |
2290 | return err; | |
2291 | if (knob > 1) | |
2292 | return -EINVAL; | |
2293 | ||
2294 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2295 | wait_while_offlining(); |
90bd6fd3 | 2296 | if (ksm_merge_across_nodes != knob) { |
cbf86cfe | 2297 | if (ksm_pages_shared || remove_all_stable_nodes()) |
90bd6fd3 PH |
2298 | err = -EBUSY; |
2299 | else | |
2300 | ksm_merge_across_nodes = knob; | |
2301 | } | |
2302 | mutex_unlock(&ksm_thread_mutex); | |
2303 | ||
2304 | return err ? err : count; | |
2305 | } | |
2306 | KSM_ATTR(merge_across_nodes); | |
2307 | #endif | |
2308 | ||
b4028260 HD |
2309 | static ssize_t pages_shared_show(struct kobject *kobj, |
2310 | struct kobj_attribute *attr, char *buf) | |
2311 | { | |
2312 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
2313 | } | |
2314 | KSM_ATTR_RO(pages_shared); | |
2315 | ||
2316 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
2317 | struct kobj_attribute *attr, char *buf) | |
2318 | { | |
e178dfde | 2319 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
2320 | } |
2321 | KSM_ATTR_RO(pages_sharing); | |
2322 | ||
473b0ce4 HD |
2323 | static ssize_t pages_unshared_show(struct kobject *kobj, |
2324 | struct kobj_attribute *attr, char *buf) | |
2325 | { | |
2326 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
2327 | } | |
2328 | KSM_ATTR_RO(pages_unshared); | |
2329 | ||
2330 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
2331 | struct kobj_attribute *attr, char *buf) | |
2332 | { | |
2333 | long ksm_pages_volatile; | |
2334 | ||
2335 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
2336 | - ksm_pages_sharing - ksm_pages_unshared; | |
2337 | /* | |
2338 | * It was not worth any locking to calculate that statistic, | |
2339 | * but it might therefore sometimes be negative: conceal that. | |
2340 | */ | |
2341 | if (ksm_pages_volatile < 0) | |
2342 | ksm_pages_volatile = 0; | |
2343 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
2344 | } | |
2345 | KSM_ATTR_RO(pages_volatile); | |
2346 | ||
2347 | static ssize_t full_scans_show(struct kobject *kobj, | |
2348 | struct kobj_attribute *attr, char *buf) | |
2349 | { | |
2350 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
2351 | } | |
2352 | KSM_ATTR_RO(full_scans); | |
2353 | ||
31dbd01f IE |
2354 | static struct attribute *ksm_attrs[] = { |
2355 | &sleep_millisecs_attr.attr, | |
2356 | &pages_to_scan_attr.attr, | |
2357 | &run_attr.attr, | |
b4028260 HD |
2358 | &pages_shared_attr.attr, |
2359 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
2360 | &pages_unshared_attr.attr, |
2361 | &pages_volatile_attr.attr, | |
2362 | &full_scans_attr.attr, | |
90bd6fd3 PH |
2363 | #ifdef CONFIG_NUMA |
2364 | &merge_across_nodes_attr.attr, | |
2365 | #endif | |
31dbd01f IE |
2366 | NULL, |
2367 | }; | |
2368 | ||
2369 | static struct attribute_group ksm_attr_group = { | |
2370 | .attrs = ksm_attrs, | |
2371 | .name = "ksm", | |
2372 | }; | |
2ffd8679 | 2373 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
2374 | |
2375 | static int __init ksm_init(void) | |
2376 | { | |
2377 | struct task_struct *ksm_thread; | |
2378 | int err; | |
90bd6fd3 | 2379 | int nid; |
31dbd01f IE |
2380 | |
2381 | err = ksm_slab_init(); | |
2382 | if (err) | |
2383 | goto out; | |
2384 | ||
90bd6fd3 PH |
2385 | for (nid = 0; nid < nr_node_ids; nid++) |
2386 | root_stable_tree[nid] = RB_ROOT; | |
2387 | ||
31dbd01f IE |
2388 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
2389 | if (IS_ERR(ksm_thread)) { | |
2390 | printk(KERN_ERR "ksm: creating kthread failed\n"); | |
2391 | err = PTR_ERR(ksm_thread); | |
d9f8984c | 2392 | goto out_free; |
31dbd01f IE |
2393 | } |
2394 | ||
2ffd8679 | 2395 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
2396 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
2397 | if (err) { | |
2398 | printk(KERN_ERR "ksm: register sysfs failed\n"); | |
2ffd8679 | 2399 | kthread_stop(ksm_thread); |
d9f8984c | 2400 | goto out_free; |
31dbd01f | 2401 | } |
c73602ad HD |
2402 | #else |
2403 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
2404 | ||
2ffd8679 | 2405 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 2406 | |
62b61f61 | 2407 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 | 2408 | /* There is no significance to this priority 100 */ |
62b61f61 HD |
2409 | hotplug_memory_notifier(ksm_memory_callback, 100); |
2410 | #endif | |
31dbd01f IE |
2411 | return 0; |
2412 | ||
d9f8984c | 2413 | out_free: |
31dbd01f IE |
2414 | ksm_slab_free(); |
2415 | out: | |
2416 | return err; | |
f8af4da3 | 2417 | } |
31dbd01f | 2418 | module_init(ksm_init) |