Commit | Line | Data |
---|---|---|
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 |
bc56620b | 153 | * @nid: NUMA node id of unstable tree in which linked (may not match page) |
31dbd01f IE |
154 | * @mm: the memory structure this rmap_item is pointing into |
155 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
156 | * @oldchecksum: previous checksum of the page at that virtual address | |
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; |
bc56620b HD |
163 | union { |
164 | struct anon_vma *anon_vma; /* when stable */ | |
165 | #ifdef CONFIG_NUMA | |
166 | int nid; /* when node of unstable tree */ | |
167 | #endif | |
168 | }; | |
31dbd01f IE |
169 | struct mm_struct *mm; |
170 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 171 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 172 | union { |
7b6ba2c7 HD |
173 | struct rb_node node; /* when node of unstable tree */ |
174 | struct { /* when listed from stable tree */ | |
175 | struct stable_node *head; | |
176 | struct hlist_node hlist; | |
177 | }; | |
31dbd01f IE |
178 | }; |
179 | }; | |
180 | ||
181 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
182 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
183 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
184 | |
185 | /* The stable and unstable tree heads */ | |
ef53d16c HD |
186 | static struct rb_root one_stable_tree[1] = { RB_ROOT }; |
187 | static struct rb_root one_unstable_tree[1] = { RB_ROOT }; | |
188 | static struct rb_root *root_stable_tree = one_stable_tree; | |
189 | static struct rb_root *root_unstable_tree = one_unstable_tree; | |
31dbd01f | 190 | |
4146d2d6 HD |
191 | /* Recently migrated nodes of stable tree, pending proper placement */ |
192 | static LIST_HEAD(migrate_nodes); | |
193 | ||
4ca3a69b SL |
194 | #define MM_SLOTS_HASH_BITS 10 |
195 | static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
31dbd01f IE |
196 | |
197 | static struct mm_slot ksm_mm_head = { | |
198 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
199 | }; | |
200 | static struct ksm_scan ksm_scan = { | |
201 | .mm_slot = &ksm_mm_head, | |
202 | }; | |
203 | ||
204 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 205 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
206 | static struct kmem_cache *mm_slot_cache; |
207 | ||
208 | /* The number of nodes in the stable tree */ | |
b4028260 | 209 | static unsigned long ksm_pages_shared; |
31dbd01f | 210 | |
e178dfde | 211 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 212 | static unsigned long ksm_pages_sharing; |
31dbd01f | 213 | |
473b0ce4 HD |
214 | /* The number of nodes in the unstable tree */ |
215 | static unsigned long ksm_pages_unshared; | |
216 | ||
217 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
218 | static unsigned long ksm_rmap_items; | |
219 | ||
31dbd01f | 220 | /* Number of pages ksmd should scan in one batch */ |
2c6854fd | 221 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
222 | |
223 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 224 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f | 225 | |
e850dcf5 | 226 | #ifdef CONFIG_NUMA |
90bd6fd3 PH |
227 | /* Zeroed when merging across nodes is not allowed */ |
228 | static unsigned int ksm_merge_across_nodes = 1; | |
ef53d16c | 229 | static int ksm_nr_node_ids = 1; |
e850dcf5 HD |
230 | #else |
231 | #define ksm_merge_across_nodes 1U | |
ef53d16c | 232 | #define ksm_nr_node_ids 1 |
e850dcf5 | 233 | #endif |
90bd6fd3 | 234 | |
31dbd01f IE |
235 | #define KSM_RUN_STOP 0 |
236 | #define KSM_RUN_MERGE 1 | |
237 | #define KSM_RUN_UNMERGE 2 | |
ef4d43a8 HD |
238 | #define KSM_RUN_OFFLINE 4 |
239 | static unsigned long ksm_run = KSM_RUN_STOP; | |
240 | static void wait_while_offlining(void); | |
31dbd01f IE |
241 | |
242 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
243 | static DEFINE_MUTEX(ksm_thread_mutex); | |
244 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
245 | ||
246 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
247 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
248 | (__flags), NULL) | |
249 | ||
250 | static int __init ksm_slab_init(void) | |
251 | { | |
252 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
253 | if (!rmap_item_cache) | |
254 | goto out; | |
255 | ||
7b6ba2c7 HD |
256 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
257 | if (!stable_node_cache) | |
258 | goto out_free1; | |
259 | ||
31dbd01f IE |
260 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
261 | if (!mm_slot_cache) | |
7b6ba2c7 | 262 | goto out_free2; |
31dbd01f IE |
263 | |
264 | return 0; | |
265 | ||
7b6ba2c7 HD |
266 | out_free2: |
267 | kmem_cache_destroy(stable_node_cache); | |
268 | out_free1: | |
31dbd01f IE |
269 | kmem_cache_destroy(rmap_item_cache); |
270 | out: | |
271 | return -ENOMEM; | |
272 | } | |
273 | ||
274 | static void __init ksm_slab_free(void) | |
275 | { | |
276 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 277 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
278 | kmem_cache_destroy(rmap_item_cache); |
279 | mm_slot_cache = NULL; | |
280 | } | |
281 | ||
282 | static inline struct rmap_item *alloc_rmap_item(void) | |
283 | { | |
473b0ce4 HD |
284 | struct rmap_item *rmap_item; |
285 | ||
286 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL); | |
287 | if (rmap_item) | |
288 | ksm_rmap_items++; | |
289 | return rmap_item; | |
31dbd01f IE |
290 | } |
291 | ||
292 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
293 | { | |
473b0ce4 | 294 | ksm_rmap_items--; |
31dbd01f IE |
295 | rmap_item->mm = NULL; /* debug safety */ |
296 | kmem_cache_free(rmap_item_cache, rmap_item); | |
297 | } | |
298 | ||
7b6ba2c7 HD |
299 | static inline struct stable_node *alloc_stable_node(void) |
300 | { | |
301 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL); | |
302 | } | |
303 | ||
304 | static inline void free_stable_node(struct stable_node *stable_node) | |
305 | { | |
306 | kmem_cache_free(stable_node_cache, stable_node); | |
307 | } | |
308 | ||
31dbd01f IE |
309 | static inline struct mm_slot *alloc_mm_slot(void) |
310 | { | |
311 | if (!mm_slot_cache) /* initialization failed */ | |
312 | return NULL; | |
313 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
314 | } | |
315 | ||
316 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
317 | { | |
318 | kmem_cache_free(mm_slot_cache, mm_slot); | |
319 | } | |
320 | ||
31dbd01f IE |
321 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
322 | { | |
4ca3a69b SL |
323 | struct mm_slot *slot; |
324 | ||
b67bfe0d | 325 | hash_for_each_possible(mm_slots_hash, slot, link, (unsigned long)mm) |
4ca3a69b SL |
326 | if (slot->mm == mm) |
327 | return slot; | |
31dbd01f | 328 | |
31dbd01f IE |
329 | return NULL; |
330 | } | |
331 | ||
332 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
333 | struct mm_slot *mm_slot) | |
334 | { | |
31dbd01f | 335 | mm_slot->mm = mm; |
4ca3a69b | 336 | hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm); |
31dbd01f IE |
337 | } |
338 | ||
a913e182 HD |
339 | /* |
340 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
341 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
342 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
343 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
344 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
345 | * places for correctness, in some places just to avoid unnecessary work. | |
346 | */ | |
347 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
348 | { | |
349 | return atomic_read(&mm->mm_users) == 0; | |
350 | } | |
351 | ||
31dbd01f IE |
352 | /* |
353 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
354 | * | |
d4edcf0d | 355 | * if (get_user_pages(addr, 1, 1, 1, &page, NULL) == 1) |
31dbd01f IE |
356 | * put_page(page); |
357 | * | |
358 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
359 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
360 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
361 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
1b2ee126 DH |
362 | * |
363 | * FAULT_FLAG/FOLL_REMOTE are because we do this outside the context | |
364 | * of the process that owns 'vma'. We also do not want to enforce | |
365 | * protection keys here anyway. | |
31dbd01f | 366 | */ |
d952b791 | 367 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
368 | { |
369 | struct page *page; | |
d952b791 | 370 | int ret = 0; |
31dbd01f IE |
371 | |
372 | do { | |
373 | cond_resched(); | |
1b2ee126 DH |
374 | page = follow_page(vma, addr, |
375 | FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); | |
22eccdd7 | 376 | if (IS_ERR_OR_NULL(page)) |
31dbd01f IE |
377 | break; |
378 | if (PageKsm(page)) | |
379 | ret = handle_mm_fault(vma->vm_mm, vma, addr, | |
1b2ee126 DH |
380 | FAULT_FLAG_WRITE | |
381 | FAULT_FLAG_REMOTE); | |
31dbd01f IE |
382 | else |
383 | ret = VM_FAULT_WRITE; | |
384 | put_page(page); | |
33692f27 | 385 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM))); |
d952b791 HD |
386 | /* |
387 | * We must loop because handle_mm_fault() may back out if there's | |
388 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
389 | * | |
390 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
391 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
392 | * but note that a concurrent fault might break PageKsm for us. | |
393 | * | |
394 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
395 | * backing file, which also invalidates anonymous pages: that's | |
396 | * okay, that truncation will have unmapped the PageKsm for us. | |
397 | * | |
398 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
399 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
400 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
401 | * to user; and ksmd, having no mm, would never be chosen for that. | |
402 | * | |
403 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
404 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
405 | * even ksmd can fail in this way - though it's usually breaking ksm | |
406 | * just to undo a merge it made a moment before, so unlikely to oom. | |
407 | * | |
408 | * That's a pity: we might therefore have more kernel pages allocated | |
409 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
410 | * will retry to break_cow on each pass, so should recover the page | |
411 | * in due course. The important thing is to not let VM_MERGEABLE | |
412 | * be cleared while any such pages might remain in the area. | |
413 | */ | |
414 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
415 | } |
416 | ||
ef694222 BL |
417 | static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, |
418 | unsigned long addr) | |
419 | { | |
420 | struct vm_area_struct *vma; | |
421 | if (ksm_test_exit(mm)) | |
422 | return NULL; | |
423 | vma = find_vma(mm, addr); | |
424 | if (!vma || vma->vm_start > addr) | |
425 | return NULL; | |
426 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
427 | return NULL; | |
428 | return vma; | |
429 | } | |
430 | ||
8dd3557a | 431 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 432 | { |
8dd3557a HD |
433 | struct mm_struct *mm = rmap_item->mm; |
434 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
435 | struct vm_area_struct *vma; |
436 | ||
4035c07a HD |
437 | /* |
438 | * It is not an accident that whenever we want to break COW | |
439 | * to undo, we also need to drop a reference to the anon_vma. | |
440 | */ | |
9e60109f | 441 | put_anon_vma(rmap_item->anon_vma); |
4035c07a | 442 | |
81464e30 | 443 | down_read(&mm->mmap_sem); |
ef694222 BL |
444 | vma = find_mergeable_vma(mm, addr); |
445 | if (vma) | |
446 | break_ksm(vma, addr); | |
31dbd01f IE |
447 | up_read(&mm->mmap_sem); |
448 | } | |
449 | ||
450 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
451 | { | |
452 | struct mm_struct *mm = rmap_item->mm; | |
453 | unsigned long addr = rmap_item->address; | |
454 | struct vm_area_struct *vma; | |
455 | struct page *page; | |
456 | ||
457 | down_read(&mm->mmap_sem); | |
ef694222 BL |
458 | vma = find_mergeable_vma(mm, addr); |
459 | if (!vma) | |
31dbd01f IE |
460 | goto out; |
461 | ||
462 | page = follow_page(vma, addr, FOLL_GET); | |
22eccdd7 | 463 | if (IS_ERR_OR_NULL(page)) |
31dbd01f | 464 | goto out; |
f765f540 | 465 | if (PageAnon(page)) { |
31dbd01f IE |
466 | flush_anon_page(vma, page, addr); |
467 | flush_dcache_page(page); | |
468 | } else { | |
469 | put_page(page); | |
c8f95ed1 AA |
470 | out: |
471 | page = NULL; | |
31dbd01f IE |
472 | } |
473 | up_read(&mm->mmap_sem); | |
474 | return page; | |
475 | } | |
476 | ||
90bd6fd3 PH |
477 | /* |
478 | * This helper is used for getting right index into array of tree roots. | |
479 | * When merge_across_nodes knob is set to 1, there are only two rb-trees for | |
480 | * stable and unstable pages from all nodes with roots in index 0. Otherwise, | |
481 | * every node has its own stable and unstable tree. | |
482 | */ | |
483 | static inline int get_kpfn_nid(unsigned long kpfn) | |
484 | { | |
d8fc16a8 | 485 | return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn)); |
90bd6fd3 PH |
486 | } |
487 | ||
4035c07a HD |
488 | static void remove_node_from_stable_tree(struct stable_node *stable_node) |
489 | { | |
490 | struct rmap_item *rmap_item; | |
4035c07a | 491 | |
b67bfe0d | 492 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
4035c07a HD |
493 | if (rmap_item->hlist.next) |
494 | ksm_pages_sharing--; | |
495 | else | |
496 | ksm_pages_shared--; | |
9e60109f | 497 | put_anon_vma(rmap_item->anon_vma); |
4035c07a HD |
498 | rmap_item->address &= PAGE_MASK; |
499 | cond_resched(); | |
500 | } | |
501 | ||
4146d2d6 HD |
502 | if (stable_node->head == &migrate_nodes) |
503 | list_del(&stable_node->list); | |
504 | else | |
505 | rb_erase(&stable_node->node, | |
ef53d16c | 506 | root_stable_tree + NUMA(stable_node->nid)); |
4035c07a HD |
507 | free_stable_node(stable_node); |
508 | } | |
509 | ||
510 | /* | |
511 | * get_ksm_page: checks if the page indicated by the stable node | |
512 | * is still its ksm page, despite having held no reference to it. | |
513 | * In which case we can trust the content of the page, and it | |
514 | * returns the gotten page; but if the page has now been zapped, | |
515 | * remove the stale node from the stable tree and return NULL. | |
c8d6553b | 516 | * But beware, the stable node's page might be being migrated. |
4035c07a HD |
517 | * |
518 | * You would expect the stable_node to hold a reference to the ksm page. | |
519 | * But if it increments the page's count, swapping out has to wait for | |
520 | * ksmd to come around again before it can free the page, which may take | |
521 | * seconds or even minutes: much too unresponsive. So instead we use a | |
522 | * "keyhole reference": access to the ksm page from the stable node peeps | |
523 | * out through its keyhole to see if that page still holds the right key, | |
524 | * pointing back to this stable node. This relies on freeing a PageAnon | |
525 | * page to reset its page->mapping to NULL, and relies on no other use of | |
526 | * a page to put something that might look like our key in page->mapping. | |
4035c07a HD |
527 | * is on its way to being freed; but it is an anomaly to bear in mind. |
528 | */ | |
8fdb3dbf | 529 | static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) |
4035c07a HD |
530 | { |
531 | struct page *page; | |
532 | void *expected_mapping; | |
c8d6553b | 533 | unsigned long kpfn; |
4035c07a | 534 | |
4035c07a HD |
535 | expected_mapping = (void *)stable_node + |
536 | (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); | |
c8d6553b | 537 | again: |
4db0c3c2 | 538 | kpfn = READ_ONCE(stable_node->kpfn); |
c8d6553b HD |
539 | page = pfn_to_page(kpfn); |
540 | ||
541 | /* | |
542 | * page is computed from kpfn, so on most architectures reading | |
543 | * page->mapping is naturally ordered after reading node->kpfn, | |
544 | * but on Alpha we need to be more careful. | |
545 | */ | |
546 | smp_read_barrier_depends(); | |
4db0c3c2 | 547 | if (READ_ONCE(page->mapping) != expected_mapping) |
4035c07a | 548 | goto stale; |
c8d6553b HD |
549 | |
550 | /* | |
551 | * We cannot do anything with the page while its refcount is 0. | |
552 | * Usually 0 means free, or tail of a higher-order page: in which | |
553 | * case this node is no longer referenced, and should be freed; | |
554 | * however, it might mean that the page is under page_freeze_refs(). | |
555 | * The __remove_mapping() case is easy, again the node is now stale; | |
556 | * but if page is swapcache in migrate_page_move_mapping(), it might | |
557 | * still be our page, in which case it's essential to keep the node. | |
558 | */ | |
559 | while (!get_page_unless_zero(page)) { | |
560 | /* | |
561 | * Another check for page->mapping != expected_mapping would | |
562 | * work here too. We have chosen the !PageSwapCache test to | |
563 | * optimize the common case, when the page is or is about to | |
564 | * be freed: PageSwapCache is cleared (under spin_lock_irq) | |
565 | * in the freeze_refs section of __remove_mapping(); but Anon | |
566 | * page->mapping reset to NULL later, in free_pages_prepare(). | |
567 | */ | |
568 | if (!PageSwapCache(page)) | |
569 | goto stale; | |
570 | cpu_relax(); | |
571 | } | |
572 | ||
4db0c3c2 | 573 | if (READ_ONCE(page->mapping) != expected_mapping) { |
4035c07a HD |
574 | put_page(page); |
575 | goto stale; | |
576 | } | |
c8d6553b | 577 | |
8fdb3dbf | 578 | if (lock_it) { |
8aafa6a4 | 579 | lock_page(page); |
4db0c3c2 | 580 | if (READ_ONCE(page->mapping) != expected_mapping) { |
8aafa6a4 HD |
581 | unlock_page(page); |
582 | put_page(page); | |
583 | goto stale; | |
584 | } | |
585 | } | |
4035c07a | 586 | return page; |
c8d6553b | 587 | |
4035c07a | 588 | stale: |
c8d6553b HD |
589 | /* |
590 | * We come here from above when page->mapping or !PageSwapCache | |
591 | * suggests that the node is stale; but it might be under migration. | |
592 | * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(), | |
593 | * before checking whether node->kpfn has been changed. | |
594 | */ | |
595 | smp_rmb(); | |
4db0c3c2 | 596 | if (READ_ONCE(stable_node->kpfn) != kpfn) |
c8d6553b | 597 | goto again; |
4035c07a HD |
598 | remove_node_from_stable_tree(stable_node); |
599 | return NULL; | |
600 | } | |
601 | ||
31dbd01f IE |
602 | /* |
603 | * Removing rmap_item from stable or unstable tree. | |
604 | * This function will clean the information from the stable/unstable tree. | |
605 | */ | |
606 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
607 | { | |
7b6ba2c7 HD |
608 | if (rmap_item->address & STABLE_FLAG) { |
609 | struct stable_node *stable_node; | |
5ad64688 | 610 | struct page *page; |
31dbd01f | 611 | |
7b6ba2c7 | 612 | stable_node = rmap_item->head; |
8aafa6a4 | 613 | page = get_ksm_page(stable_node, true); |
4035c07a HD |
614 | if (!page) |
615 | goto out; | |
5ad64688 | 616 | |
7b6ba2c7 | 617 | hlist_del(&rmap_item->hlist); |
4035c07a HD |
618 | unlock_page(page); |
619 | put_page(page); | |
08beca44 | 620 | |
98666f8a | 621 | if (!hlist_empty(&stable_node->hlist)) |
4035c07a HD |
622 | ksm_pages_sharing--; |
623 | else | |
7b6ba2c7 | 624 | ksm_pages_shared--; |
31dbd01f | 625 | |
9e60109f | 626 | put_anon_vma(rmap_item->anon_vma); |
93d17715 | 627 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 628 | |
7b6ba2c7 | 629 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
630 | unsigned char age; |
631 | /* | |
9ba69294 | 632 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 633 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
634 | * But be careful when an mm is exiting: do the rb_erase |
635 | * if this rmap_item was inserted by this scan, rather | |
636 | * than left over from before. | |
31dbd01f IE |
637 | */ |
638 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 639 | BUG_ON(age > 1); |
31dbd01f | 640 | if (!age) |
90bd6fd3 | 641 | rb_erase(&rmap_item->node, |
ef53d16c | 642 | root_unstable_tree + NUMA(rmap_item->nid)); |
473b0ce4 | 643 | ksm_pages_unshared--; |
93d17715 | 644 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 645 | } |
4035c07a | 646 | out: |
31dbd01f IE |
647 | cond_resched(); /* we're called from many long loops */ |
648 | } | |
649 | ||
31dbd01f | 650 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 651 | struct rmap_item **rmap_list) |
31dbd01f | 652 | { |
6514d511 HD |
653 | while (*rmap_list) { |
654 | struct rmap_item *rmap_item = *rmap_list; | |
655 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 656 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
657 | free_rmap_item(rmap_item); |
658 | } | |
659 | } | |
660 | ||
661 | /* | |
e850dcf5 | 662 | * Though it's very tempting to unmerge rmap_items from stable tree rather |
31dbd01f IE |
663 | * than check every pte of a given vma, the locking doesn't quite work for |
664 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
665 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
666 | * rmap_items from parent to child at fork time (so as not to waste time | |
667 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
668 | * |
669 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
670 | * and freeing memory) when unmerging an area, it's easier to leave that | |
671 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
672 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 673 | */ |
d952b791 HD |
674 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
675 | unsigned long start, unsigned long end) | |
31dbd01f IE |
676 | { |
677 | unsigned long addr; | |
d952b791 | 678 | int err = 0; |
31dbd01f | 679 | |
d952b791 | 680 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
681 | if (ksm_test_exit(vma->vm_mm)) |
682 | break; | |
d952b791 HD |
683 | if (signal_pending(current)) |
684 | err = -ERESTARTSYS; | |
685 | else | |
686 | err = break_ksm(vma, addr); | |
687 | } | |
688 | return err; | |
31dbd01f IE |
689 | } |
690 | ||
2ffd8679 HD |
691 | #ifdef CONFIG_SYSFS |
692 | /* | |
693 | * Only called through the sysfs control interface: | |
694 | */ | |
cbf86cfe HD |
695 | static int remove_stable_node(struct stable_node *stable_node) |
696 | { | |
697 | struct page *page; | |
698 | int err; | |
699 | ||
700 | page = get_ksm_page(stable_node, true); | |
701 | if (!page) { | |
702 | /* | |
703 | * get_ksm_page did remove_node_from_stable_tree itself. | |
704 | */ | |
705 | return 0; | |
706 | } | |
707 | ||
8fdb3dbf HD |
708 | if (WARN_ON_ONCE(page_mapped(page))) { |
709 | /* | |
710 | * This should not happen: but if it does, just refuse to let | |
711 | * merge_across_nodes be switched - there is no need to panic. | |
712 | */ | |
cbf86cfe | 713 | err = -EBUSY; |
8fdb3dbf | 714 | } else { |
cbf86cfe | 715 | /* |
8fdb3dbf HD |
716 | * The stable node did not yet appear stale to get_ksm_page(), |
717 | * since that allows for an unmapped ksm page to be recognized | |
718 | * right up until it is freed; but the node is safe to remove. | |
cbf86cfe HD |
719 | * This page might be in a pagevec waiting to be freed, |
720 | * or it might be PageSwapCache (perhaps under writeback), | |
721 | * or it might have been removed from swapcache a moment ago. | |
722 | */ | |
723 | set_page_stable_node(page, NULL); | |
724 | remove_node_from_stable_tree(stable_node); | |
725 | err = 0; | |
726 | } | |
727 | ||
728 | unlock_page(page); | |
729 | put_page(page); | |
730 | return err; | |
731 | } | |
732 | ||
733 | static int remove_all_stable_nodes(void) | |
734 | { | |
03640418 | 735 | struct stable_node *stable_node, *next; |
cbf86cfe HD |
736 | int nid; |
737 | int err = 0; | |
738 | ||
ef53d16c | 739 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
cbf86cfe HD |
740 | while (root_stable_tree[nid].rb_node) { |
741 | stable_node = rb_entry(root_stable_tree[nid].rb_node, | |
742 | struct stable_node, node); | |
743 | if (remove_stable_node(stable_node)) { | |
744 | err = -EBUSY; | |
745 | break; /* proceed to next nid */ | |
746 | } | |
747 | cond_resched(); | |
748 | } | |
749 | } | |
03640418 | 750 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
751 | if (remove_stable_node(stable_node)) |
752 | err = -EBUSY; | |
753 | cond_resched(); | |
754 | } | |
cbf86cfe HD |
755 | return err; |
756 | } | |
757 | ||
d952b791 | 758 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
759 | { |
760 | struct mm_slot *mm_slot; | |
761 | struct mm_struct *mm; | |
762 | struct vm_area_struct *vma; | |
d952b791 HD |
763 | int err = 0; |
764 | ||
765 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 766 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
767 | struct mm_slot, mm_list); |
768 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 769 | |
9ba69294 HD |
770 | for (mm_slot = ksm_scan.mm_slot; |
771 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
772 | mm = mm_slot->mm; |
773 | down_read(&mm->mmap_sem); | |
774 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
775 | if (ksm_test_exit(mm)) |
776 | break; | |
31dbd01f IE |
777 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
778 | continue; | |
d952b791 HD |
779 | err = unmerge_ksm_pages(vma, |
780 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
781 | if (err) |
782 | goto error; | |
31dbd01f | 783 | } |
9ba69294 | 784 | |
6514d511 | 785 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
d952b791 HD |
786 | |
787 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 788 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 789 | struct mm_slot, mm_list); |
9ba69294 | 790 | if (ksm_test_exit(mm)) { |
4ca3a69b | 791 | hash_del(&mm_slot->link); |
9ba69294 HD |
792 | list_del(&mm_slot->mm_list); |
793 | spin_unlock(&ksm_mmlist_lock); | |
794 | ||
795 | free_mm_slot(mm_slot); | |
796 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
797 | up_read(&mm->mmap_sem); | |
798 | mmdrop(mm); | |
799 | } else { | |
800 | spin_unlock(&ksm_mmlist_lock); | |
801 | up_read(&mm->mmap_sem); | |
802 | } | |
31dbd01f IE |
803 | } |
804 | ||
cbf86cfe HD |
805 | /* Clean up stable nodes, but don't worry if some are still busy */ |
806 | remove_all_stable_nodes(); | |
d952b791 | 807 | ksm_scan.seqnr = 0; |
9ba69294 HD |
808 | return 0; |
809 | ||
810 | error: | |
811 | up_read(&mm->mmap_sem); | |
31dbd01f | 812 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 813 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 814 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 815 | return err; |
31dbd01f | 816 | } |
2ffd8679 | 817 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 818 | |
31dbd01f IE |
819 | static u32 calc_checksum(struct page *page) |
820 | { | |
821 | u32 checksum; | |
9b04c5fe | 822 | void *addr = kmap_atomic(page); |
31dbd01f | 823 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); |
9b04c5fe | 824 | kunmap_atomic(addr); |
31dbd01f IE |
825 | return checksum; |
826 | } | |
827 | ||
828 | static int memcmp_pages(struct page *page1, struct page *page2) | |
829 | { | |
830 | char *addr1, *addr2; | |
831 | int ret; | |
832 | ||
9b04c5fe CW |
833 | addr1 = kmap_atomic(page1); |
834 | addr2 = kmap_atomic(page2); | |
31dbd01f | 835 | ret = memcmp(addr1, addr2, PAGE_SIZE); |
9b04c5fe CW |
836 | kunmap_atomic(addr2); |
837 | kunmap_atomic(addr1); | |
31dbd01f IE |
838 | return ret; |
839 | } | |
840 | ||
841 | static inline int pages_identical(struct page *page1, struct page *page2) | |
842 | { | |
843 | return !memcmp_pages(page1, page2); | |
844 | } | |
845 | ||
846 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
847 | pte_t *orig_pte) | |
848 | { | |
849 | struct mm_struct *mm = vma->vm_mm; | |
850 | unsigned long addr; | |
851 | pte_t *ptep; | |
852 | spinlock_t *ptl; | |
853 | int swapped; | |
854 | int err = -EFAULT; | |
6bdb913f HE |
855 | unsigned long mmun_start; /* For mmu_notifiers */ |
856 | unsigned long mmun_end; /* For mmu_notifiers */ | |
31dbd01f IE |
857 | |
858 | addr = page_address_in_vma(page, vma); | |
859 | if (addr == -EFAULT) | |
860 | goto out; | |
861 | ||
29ad768c | 862 | BUG_ON(PageTransCompound(page)); |
6bdb913f HE |
863 | |
864 | mmun_start = addr; | |
865 | mmun_end = addr + PAGE_SIZE; | |
866 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
867 | ||
31dbd01f IE |
868 | ptep = page_check_address(page, mm, addr, &ptl, 0); |
869 | if (!ptep) | |
6bdb913f | 870 | goto out_mn; |
31dbd01f | 871 | |
4e31635c | 872 | if (pte_write(*ptep) || pte_dirty(*ptep)) { |
31dbd01f IE |
873 | pte_t entry; |
874 | ||
875 | swapped = PageSwapCache(page); | |
876 | flush_cache_page(vma, addr, page_to_pfn(page)); | |
877 | /* | |
25985edc | 878 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
31dbd01f IE |
879 | * take any lock, therefore the check that we are going to make |
880 | * with the pagecount against the mapcount is racey and | |
881 | * O_DIRECT can happen right after the check. | |
882 | * So we clear the pte and flush the tlb before the check | |
883 | * this assure us that no O_DIRECT can happen after the check | |
884 | * or in the middle of the check. | |
885 | */ | |
34ee645e | 886 | entry = ptep_clear_flush_notify(vma, addr, ptep); |
31dbd01f IE |
887 | /* |
888 | * Check that no O_DIRECT or similar I/O is in progress on the | |
889 | * page | |
890 | */ | |
31e855ea | 891 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
cb532375 | 892 | set_pte_at(mm, addr, ptep, entry); |
31dbd01f IE |
893 | goto out_unlock; |
894 | } | |
4e31635c HD |
895 | if (pte_dirty(entry)) |
896 | set_page_dirty(page); | |
897 | entry = pte_mkclean(pte_wrprotect(entry)); | |
31dbd01f IE |
898 | set_pte_at_notify(mm, addr, ptep, entry); |
899 | } | |
900 | *orig_pte = *ptep; | |
901 | err = 0; | |
902 | ||
903 | out_unlock: | |
904 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f HE |
905 | out_mn: |
906 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
31dbd01f IE |
907 | out: |
908 | return err; | |
909 | } | |
910 | ||
911 | /** | |
912 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
913 | * @vma: vma that holds the pte pointing to page |
914 | * @page: the page we are replacing by kpage | |
915 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
916 | * @orig_pte: the original value of the pte |
917 | * | |
918 | * Returns 0 on success, -EFAULT on failure. | |
919 | */ | |
8dd3557a HD |
920 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
921 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
922 | { |
923 | struct mm_struct *mm = vma->vm_mm; | |
31dbd01f IE |
924 | pmd_t *pmd; |
925 | pte_t *ptep; | |
926 | spinlock_t *ptl; | |
927 | unsigned long addr; | |
31dbd01f | 928 | int err = -EFAULT; |
6bdb913f HE |
929 | unsigned long mmun_start; /* For mmu_notifiers */ |
930 | unsigned long mmun_end; /* For mmu_notifiers */ | |
31dbd01f | 931 | |
8dd3557a | 932 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
933 | if (addr == -EFAULT) |
934 | goto out; | |
935 | ||
6219049a BL |
936 | pmd = mm_find_pmd(mm, addr); |
937 | if (!pmd) | |
31dbd01f | 938 | goto out; |
31dbd01f | 939 | |
6bdb913f HE |
940 | mmun_start = addr; |
941 | mmun_end = addr + PAGE_SIZE; | |
942 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
943 | ||
31dbd01f IE |
944 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
945 | if (!pte_same(*ptep, orig_pte)) { | |
946 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f | 947 | goto out_mn; |
31dbd01f IE |
948 | } |
949 | ||
8dd3557a | 950 | get_page(kpage); |
d281ee61 | 951 | page_add_anon_rmap(kpage, vma, addr, false); |
31dbd01f IE |
952 | |
953 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
34ee645e | 954 | ptep_clear_flush_notify(vma, addr, ptep); |
8dd3557a | 955 | set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot)); |
31dbd01f | 956 | |
d281ee61 | 957 | page_remove_rmap(page, false); |
ae52a2ad HD |
958 | if (!page_mapped(page)) |
959 | try_to_free_swap(page); | |
8dd3557a | 960 | put_page(page); |
31dbd01f IE |
961 | |
962 | pte_unmap_unlock(ptep, ptl); | |
963 | err = 0; | |
6bdb913f HE |
964 | out_mn: |
965 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
31dbd01f IE |
966 | out: |
967 | return err; | |
968 | } | |
969 | ||
970 | /* | |
971 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
972 | * @vma: the vma that holds the pte pointing to page |
973 | * @page: the PageAnon page that we want to replace with kpage | |
80e14822 HD |
974 | * @kpage: the PageKsm page that we want to map instead of page, |
975 | * or NULL the first time when we want to use page as kpage. | |
31dbd01f IE |
976 | * |
977 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
978 | */ | |
979 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 980 | struct page *page, struct page *kpage) |
31dbd01f IE |
981 | { |
982 | pte_t orig_pte = __pte(0); | |
983 | int err = -EFAULT; | |
984 | ||
db114b83 HD |
985 | if (page == kpage) /* ksm page forked */ |
986 | return 0; | |
987 | ||
8dd3557a | 988 | if (!PageAnon(page)) |
31dbd01f IE |
989 | goto out; |
990 | ||
31dbd01f IE |
991 | /* |
992 | * We need the page lock to read a stable PageSwapCache in | |
993 | * write_protect_page(). We use trylock_page() instead of | |
994 | * lock_page() because we don't want to wait here - we | |
995 | * prefer to continue scanning and merging different pages, | |
996 | * then come back to this page when it is unlocked. | |
997 | */ | |
8dd3557a | 998 | if (!trylock_page(page)) |
31e855ea | 999 | goto out; |
f765f540 KS |
1000 | |
1001 | if (PageTransCompound(page)) { | |
1002 | err = split_huge_page(page); | |
1003 | if (err) | |
1004 | goto out_unlock; | |
1005 | } | |
1006 | ||
31dbd01f IE |
1007 | /* |
1008 | * If this anonymous page is mapped only here, its pte may need | |
1009 | * to be write-protected. If it's mapped elsewhere, all of its | |
1010 | * ptes are necessarily already write-protected. But in either | |
1011 | * case, we need to lock and check page_count is not raised. | |
1012 | */ | |
80e14822 HD |
1013 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
1014 | if (!kpage) { | |
1015 | /* | |
1016 | * While we hold page lock, upgrade page from | |
1017 | * PageAnon+anon_vma to PageKsm+NULL stable_node: | |
1018 | * stable_tree_insert() will update stable_node. | |
1019 | */ | |
1020 | set_page_stable_node(page, NULL); | |
1021 | mark_page_accessed(page); | |
337ed7eb MK |
1022 | /* |
1023 | * Page reclaim just frees a clean page with no dirty | |
1024 | * ptes: make sure that the ksm page would be swapped. | |
1025 | */ | |
1026 | if (!PageDirty(page)) | |
1027 | SetPageDirty(page); | |
80e14822 HD |
1028 | err = 0; |
1029 | } else if (pages_identical(page, kpage)) | |
1030 | err = replace_page(vma, page, kpage, orig_pte); | |
1031 | } | |
31dbd01f | 1032 | |
80e14822 | 1033 | if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { |
73848b46 | 1034 | munlock_vma_page(page); |
5ad64688 HD |
1035 | if (!PageMlocked(kpage)) { |
1036 | unlock_page(page); | |
5ad64688 HD |
1037 | lock_page(kpage); |
1038 | mlock_vma_page(kpage); | |
1039 | page = kpage; /* for final unlock */ | |
1040 | } | |
1041 | } | |
73848b46 | 1042 | |
f765f540 | 1043 | out_unlock: |
8dd3557a | 1044 | unlock_page(page); |
31dbd01f IE |
1045 | out: |
1046 | return err; | |
1047 | } | |
1048 | ||
81464e30 HD |
1049 | /* |
1050 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
1051 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
1052 | * |
1053 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 1054 | */ |
8dd3557a HD |
1055 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
1056 | struct page *page, struct page *kpage) | |
81464e30 | 1057 | { |
8dd3557a | 1058 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
1059 | struct vm_area_struct *vma; |
1060 | int err = -EFAULT; | |
1061 | ||
8dd3557a | 1062 | down_read(&mm->mmap_sem); |
85c6e8dd AA |
1063 | vma = find_mergeable_vma(mm, rmap_item->address); |
1064 | if (!vma) | |
81464e30 HD |
1065 | goto out; |
1066 | ||
8dd3557a | 1067 | err = try_to_merge_one_page(vma, page, kpage); |
db114b83 HD |
1068 | if (err) |
1069 | goto out; | |
1070 | ||
bc56620b HD |
1071 | /* Unstable nid is in union with stable anon_vma: remove first */ |
1072 | remove_rmap_item_from_tree(rmap_item); | |
1073 | ||
db114b83 | 1074 | /* Must get reference to anon_vma while still holding mmap_sem */ |
9e60109f PZ |
1075 | rmap_item->anon_vma = vma->anon_vma; |
1076 | get_anon_vma(vma->anon_vma); | |
81464e30 | 1077 | out: |
8dd3557a | 1078 | up_read(&mm->mmap_sem); |
81464e30 HD |
1079 | return err; |
1080 | } | |
1081 | ||
31dbd01f IE |
1082 | /* |
1083 | * try_to_merge_two_pages - take two identical pages and prepare them | |
1084 | * to be merged into one page. | |
1085 | * | |
8dd3557a HD |
1086 | * This function returns the kpage if we successfully merged two identical |
1087 | * pages into one ksm page, NULL otherwise. | |
31dbd01f | 1088 | * |
80e14822 | 1089 | * Note that this function upgrades page to ksm page: if one of the pages |
31dbd01f IE |
1090 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
1091 | */ | |
8dd3557a HD |
1092 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
1093 | struct page *page, | |
1094 | struct rmap_item *tree_rmap_item, | |
1095 | struct page *tree_page) | |
31dbd01f | 1096 | { |
80e14822 | 1097 | int err; |
31dbd01f | 1098 | |
80e14822 | 1099 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
31dbd01f | 1100 | if (!err) { |
8dd3557a | 1101 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
80e14822 | 1102 | tree_page, page); |
31dbd01f | 1103 | /* |
81464e30 HD |
1104 | * If that fails, we have a ksm page with only one pte |
1105 | * pointing to it: so break it. | |
31dbd01f | 1106 | */ |
4035c07a | 1107 | if (err) |
8dd3557a | 1108 | break_cow(rmap_item); |
31dbd01f | 1109 | } |
80e14822 | 1110 | return err ? NULL : page; |
31dbd01f IE |
1111 | } |
1112 | ||
31dbd01f | 1113 | /* |
8dd3557a | 1114 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
1115 | * |
1116 | * This function checks if there is a page inside the stable tree | |
1117 | * with identical content to the page that we are scanning right now. | |
1118 | * | |
7b6ba2c7 | 1119 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
1120 | * NULL otherwise. |
1121 | */ | |
62b61f61 | 1122 | static struct page *stable_tree_search(struct page *page) |
31dbd01f | 1123 | { |
90bd6fd3 | 1124 | int nid; |
ef53d16c | 1125 | struct rb_root *root; |
4146d2d6 HD |
1126 | struct rb_node **new; |
1127 | struct rb_node *parent; | |
1128 | struct stable_node *stable_node; | |
1129 | struct stable_node *page_node; | |
31dbd01f | 1130 | |
4146d2d6 HD |
1131 | page_node = page_stable_node(page); |
1132 | if (page_node && page_node->head != &migrate_nodes) { | |
1133 | /* ksm page forked */ | |
08beca44 | 1134 | get_page(page); |
62b61f61 | 1135 | return page; |
08beca44 HD |
1136 | } |
1137 | ||
90bd6fd3 | 1138 | nid = get_kpfn_nid(page_to_pfn(page)); |
ef53d16c | 1139 | root = root_stable_tree + nid; |
4146d2d6 | 1140 | again: |
ef53d16c | 1141 | new = &root->rb_node; |
4146d2d6 | 1142 | parent = NULL; |
90bd6fd3 | 1143 | |
4146d2d6 | 1144 | while (*new) { |
4035c07a | 1145 | struct page *tree_page; |
31dbd01f IE |
1146 | int ret; |
1147 | ||
08beca44 | 1148 | cond_resched(); |
4146d2d6 | 1149 | stable_node = rb_entry(*new, struct stable_node, node); |
8aafa6a4 | 1150 | tree_page = get_ksm_page(stable_node, false); |
f2e5ff85 AA |
1151 | if (!tree_page) { |
1152 | /* | |
1153 | * If we walked over a stale stable_node, | |
1154 | * get_ksm_page() will call rb_erase() and it | |
1155 | * may rebalance the tree from under us. So | |
1156 | * restart the search from scratch. Returning | |
1157 | * NULL would be safe too, but we'd generate | |
1158 | * false negative insertions just because some | |
1159 | * stable_node was stale. | |
1160 | */ | |
1161 | goto again; | |
1162 | } | |
31dbd01f | 1163 | |
4035c07a | 1164 | ret = memcmp_pages(page, tree_page); |
c8d6553b | 1165 | put_page(tree_page); |
31dbd01f | 1166 | |
4146d2d6 | 1167 | parent = *new; |
c8d6553b | 1168 | if (ret < 0) |
4146d2d6 | 1169 | new = &parent->rb_left; |
c8d6553b | 1170 | else if (ret > 0) |
4146d2d6 | 1171 | new = &parent->rb_right; |
c8d6553b HD |
1172 | else { |
1173 | /* | |
1174 | * Lock and unlock the stable_node's page (which | |
1175 | * might already have been migrated) so that page | |
1176 | * migration is sure to notice its raised count. | |
1177 | * It would be more elegant to return stable_node | |
1178 | * than kpage, but that involves more changes. | |
1179 | */ | |
1180 | tree_page = get_ksm_page(stable_node, true); | |
4146d2d6 | 1181 | if (tree_page) { |
c8d6553b | 1182 | unlock_page(tree_page); |
4146d2d6 HD |
1183 | if (get_kpfn_nid(stable_node->kpfn) != |
1184 | NUMA(stable_node->nid)) { | |
1185 | put_page(tree_page); | |
1186 | goto replace; | |
1187 | } | |
1188 | return tree_page; | |
1189 | } | |
1190 | /* | |
1191 | * There is now a place for page_node, but the tree may | |
1192 | * have been rebalanced, so re-evaluate parent and new. | |
1193 | */ | |
1194 | if (page_node) | |
1195 | goto again; | |
1196 | return NULL; | |
c8d6553b | 1197 | } |
31dbd01f IE |
1198 | } |
1199 | ||
4146d2d6 HD |
1200 | if (!page_node) |
1201 | return NULL; | |
1202 | ||
1203 | list_del(&page_node->list); | |
1204 | DO_NUMA(page_node->nid = nid); | |
1205 | rb_link_node(&page_node->node, parent, new); | |
ef53d16c | 1206 | rb_insert_color(&page_node->node, root); |
4146d2d6 HD |
1207 | get_page(page); |
1208 | return page; | |
1209 | ||
1210 | replace: | |
1211 | if (page_node) { | |
1212 | list_del(&page_node->list); | |
1213 | DO_NUMA(page_node->nid = nid); | |
ef53d16c | 1214 | rb_replace_node(&stable_node->node, &page_node->node, root); |
4146d2d6 HD |
1215 | get_page(page); |
1216 | } else { | |
ef53d16c | 1217 | rb_erase(&stable_node->node, root); |
4146d2d6 HD |
1218 | page = NULL; |
1219 | } | |
1220 | stable_node->head = &migrate_nodes; | |
1221 | list_add(&stable_node->list, stable_node->head); | |
1222 | return page; | |
31dbd01f IE |
1223 | } |
1224 | ||
1225 | /* | |
e850dcf5 | 1226 | * stable_tree_insert - insert stable tree node pointing to new ksm page |
31dbd01f IE |
1227 | * into the stable tree. |
1228 | * | |
7b6ba2c7 HD |
1229 | * This function returns the stable tree node just allocated on success, |
1230 | * NULL otherwise. | |
31dbd01f | 1231 | */ |
7b6ba2c7 | 1232 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f | 1233 | { |
90bd6fd3 PH |
1234 | int nid; |
1235 | unsigned long kpfn; | |
ef53d16c | 1236 | struct rb_root *root; |
90bd6fd3 | 1237 | struct rb_node **new; |
f2e5ff85 | 1238 | struct rb_node *parent; |
7b6ba2c7 | 1239 | struct stable_node *stable_node; |
31dbd01f | 1240 | |
90bd6fd3 PH |
1241 | kpfn = page_to_pfn(kpage); |
1242 | nid = get_kpfn_nid(kpfn); | |
ef53d16c | 1243 | root = root_stable_tree + nid; |
f2e5ff85 AA |
1244 | again: |
1245 | parent = NULL; | |
ef53d16c | 1246 | new = &root->rb_node; |
90bd6fd3 | 1247 | |
31dbd01f | 1248 | while (*new) { |
4035c07a | 1249 | struct page *tree_page; |
31dbd01f IE |
1250 | int ret; |
1251 | ||
08beca44 | 1252 | cond_resched(); |
7b6ba2c7 | 1253 | stable_node = rb_entry(*new, struct stable_node, node); |
8aafa6a4 | 1254 | tree_page = get_ksm_page(stable_node, false); |
f2e5ff85 AA |
1255 | if (!tree_page) { |
1256 | /* | |
1257 | * If we walked over a stale stable_node, | |
1258 | * get_ksm_page() will call rb_erase() and it | |
1259 | * may rebalance the tree from under us. So | |
1260 | * restart the search from scratch. Returning | |
1261 | * NULL would be safe too, but we'd generate | |
1262 | * false negative insertions just because some | |
1263 | * stable_node was stale. | |
1264 | */ | |
1265 | goto again; | |
1266 | } | |
31dbd01f | 1267 | |
4035c07a HD |
1268 | ret = memcmp_pages(kpage, tree_page); |
1269 | put_page(tree_page); | |
31dbd01f IE |
1270 | |
1271 | parent = *new; | |
1272 | if (ret < 0) | |
1273 | new = &parent->rb_left; | |
1274 | else if (ret > 0) | |
1275 | new = &parent->rb_right; | |
1276 | else { | |
1277 | /* | |
1278 | * It is not a bug that stable_tree_search() didn't | |
1279 | * find this node: because at that time our page was | |
1280 | * not yet write-protected, so may have changed since. | |
1281 | */ | |
1282 | return NULL; | |
1283 | } | |
1284 | } | |
1285 | ||
7b6ba2c7 HD |
1286 | stable_node = alloc_stable_node(); |
1287 | if (!stable_node) | |
1288 | return NULL; | |
31dbd01f | 1289 | |
7b6ba2c7 | 1290 | INIT_HLIST_HEAD(&stable_node->hlist); |
90bd6fd3 | 1291 | stable_node->kpfn = kpfn; |
08beca44 | 1292 | set_page_stable_node(kpage, stable_node); |
4146d2d6 | 1293 | DO_NUMA(stable_node->nid = nid); |
e850dcf5 | 1294 | rb_link_node(&stable_node->node, parent, new); |
ef53d16c | 1295 | rb_insert_color(&stable_node->node, root); |
08beca44 | 1296 | |
7b6ba2c7 | 1297 | return stable_node; |
31dbd01f IE |
1298 | } |
1299 | ||
1300 | /* | |
8dd3557a HD |
1301 | * unstable_tree_search_insert - search for identical page, |
1302 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
1303 | * |
1304 | * This function searches for a page in the unstable tree identical to the | |
1305 | * page currently being scanned; and if no identical page is found in the | |
1306 | * tree, we insert rmap_item as a new object into the unstable tree. | |
1307 | * | |
1308 | * This function returns pointer to rmap_item found to be identical | |
1309 | * to the currently scanned page, NULL otherwise. | |
1310 | * | |
1311 | * This function does both searching and inserting, because they share | |
1312 | * the same walking algorithm in an rbtree. | |
1313 | */ | |
8dd3557a HD |
1314 | static |
1315 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
1316 | struct page *page, | |
1317 | struct page **tree_pagep) | |
31dbd01f | 1318 | { |
90bd6fd3 PH |
1319 | struct rb_node **new; |
1320 | struct rb_root *root; | |
31dbd01f | 1321 | struct rb_node *parent = NULL; |
90bd6fd3 PH |
1322 | int nid; |
1323 | ||
1324 | nid = get_kpfn_nid(page_to_pfn(page)); | |
ef53d16c | 1325 | root = root_unstable_tree + nid; |
90bd6fd3 | 1326 | new = &root->rb_node; |
31dbd01f IE |
1327 | |
1328 | while (*new) { | |
1329 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 1330 | struct page *tree_page; |
31dbd01f IE |
1331 | int ret; |
1332 | ||
d178f27f | 1333 | cond_resched(); |
31dbd01f | 1334 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a | 1335 | tree_page = get_mergeable_page(tree_rmap_item); |
c8f95ed1 | 1336 | if (!tree_page) |
31dbd01f IE |
1337 | return NULL; |
1338 | ||
1339 | /* | |
8dd3557a | 1340 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1341 | */ |
8dd3557a HD |
1342 | if (page == tree_page) { |
1343 | put_page(tree_page); | |
31dbd01f IE |
1344 | return NULL; |
1345 | } | |
1346 | ||
8dd3557a | 1347 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1348 | |
1349 | parent = *new; | |
1350 | if (ret < 0) { | |
8dd3557a | 1351 | put_page(tree_page); |
31dbd01f IE |
1352 | new = &parent->rb_left; |
1353 | } else if (ret > 0) { | |
8dd3557a | 1354 | put_page(tree_page); |
31dbd01f | 1355 | new = &parent->rb_right; |
b599cbdf HD |
1356 | } else if (!ksm_merge_across_nodes && |
1357 | page_to_nid(tree_page) != nid) { | |
1358 | /* | |
1359 | * If tree_page has been migrated to another NUMA node, | |
1360 | * it will be flushed out and put in the right unstable | |
1361 | * tree next time: only merge with it when across_nodes. | |
1362 | */ | |
1363 | put_page(tree_page); | |
1364 | return NULL; | |
31dbd01f | 1365 | } else { |
8dd3557a | 1366 | *tree_pagep = tree_page; |
31dbd01f IE |
1367 | return tree_rmap_item; |
1368 | } | |
1369 | } | |
1370 | ||
7b6ba2c7 | 1371 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f | 1372 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
e850dcf5 | 1373 | DO_NUMA(rmap_item->nid = nid); |
31dbd01f | 1374 | rb_link_node(&rmap_item->node, parent, new); |
90bd6fd3 | 1375 | rb_insert_color(&rmap_item->node, root); |
31dbd01f | 1376 | |
473b0ce4 | 1377 | ksm_pages_unshared++; |
31dbd01f IE |
1378 | return NULL; |
1379 | } | |
1380 | ||
1381 | /* | |
1382 | * stable_tree_append - add another rmap_item to the linked list of | |
1383 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1384 | * the same ksm page. | |
1385 | */ | |
1386 | static void stable_tree_append(struct rmap_item *rmap_item, | |
7b6ba2c7 | 1387 | struct stable_node *stable_node) |
31dbd01f | 1388 | { |
7b6ba2c7 | 1389 | rmap_item->head = stable_node; |
31dbd01f | 1390 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1391 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1392 | |
7b6ba2c7 HD |
1393 | if (rmap_item->hlist.next) |
1394 | ksm_pages_sharing++; | |
1395 | else | |
1396 | ksm_pages_shared++; | |
31dbd01f IE |
1397 | } |
1398 | ||
1399 | /* | |
81464e30 HD |
1400 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1401 | * if not, compare checksum to previous and if it's the same, see if page can | |
1402 | * be inserted into the unstable tree, or merged with a page already there and | |
1403 | * both transferred to the stable tree. | |
31dbd01f IE |
1404 | * |
1405 | * @page: the page that we are searching identical page to. | |
1406 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1407 | */ | |
1408 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1409 | { | |
31dbd01f | 1410 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1411 | struct page *tree_page = NULL; |
7b6ba2c7 | 1412 | struct stable_node *stable_node; |
8dd3557a | 1413 | struct page *kpage; |
31dbd01f IE |
1414 | unsigned int checksum; |
1415 | int err; | |
1416 | ||
4146d2d6 HD |
1417 | stable_node = page_stable_node(page); |
1418 | if (stable_node) { | |
1419 | if (stable_node->head != &migrate_nodes && | |
1420 | get_kpfn_nid(stable_node->kpfn) != NUMA(stable_node->nid)) { | |
1421 | rb_erase(&stable_node->node, | |
ef53d16c | 1422 | root_stable_tree + NUMA(stable_node->nid)); |
4146d2d6 HD |
1423 | stable_node->head = &migrate_nodes; |
1424 | list_add(&stable_node->list, stable_node->head); | |
1425 | } | |
1426 | if (stable_node->head != &migrate_nodes && | |
1427 | rmap_item->head == stable_node) | |
1428 | return; | |
1429 | } | |
31dbd01f IE |
1430 | |
1431 | /* We first start with searching the page inside the stable tree */ | |
62b61f61 | 1432 | kpage = stable_tree_search(page); |
4146d2d6 HD |
1433 | if (kpage == page && rmap_item->head == stable_node) { |
1434 | put_page(kpage); | |
1435 | return; | |
1436 | } | |
1437 | ||
1438 | remove_rmap_item_from_tree(rmap_item); | |
1439 | ||
62b61f61 | 1440 | if (kpage) { |
08beca44 | 1441 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
31dbd01f IE |
1442 | if (!err) { |
1443 | /* | |
1444 | * The page was successfully merged: | |
1445 | * add its rmap_item to the stable tree. | |
1446 | */ | |
5ad64688 | 1447 | lock_page(kpage); |
62b61f61 | 1448 | stable_tree_append(rmap_item, page_stable_node(kpage)); |
5ad64688 | 1449 | unlock_page(kpage); |
31dbd01f | 1450 | } |
8dd3557a | 1451 | put_page(kpage); |
31dbd01f IE |
1452 | return; |
1453 | } | |
1454 | ||
1455 | /* | |
4035c07a HD |
1456 | * If the hash value of the page has changed from the last time |
1457 | * we calculated it, this page is changing frequently: therefore we | |
1458 | * don't want to insert it in the unstable tree, and we don't want | |
1459 | * to waste our time searching for something identical to it there. | |
31dbd01f IE |
1460 | */ |
1461 | checksum = calc_checksum(page); | |
1462 | if (rmap_item->oldchecksum != checksum) { | |
1463 | rmap_item->oldchecksum = checksum; | |
1464 | return; | |
1465 | } | |
1466 | ||
8dd3557a HD |
1467 | tree_rmap_item = |
1468 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 1469 | if (tree_rmap_item) { |
8dd3557a HD |
1470 | kpage = try_to_merge_two_pages(rmap_item, page, |
1471 | tree_rmap_item, tree_page); | |
1472 | put_page(tree_page); | |
8dd3557a | 1473 | if (kpage) { |
bc56620b HD |
1474 | /* |
1475 | * The pages were successfully merged: insert new | |
1476 | * node in the stable tree and add both rmap_items. | |
1477 | */ | |
5ad64688 | 1478 | lock_page(kpage); |
7b6ba2c7 HD |
1479 | stable_node = stable_tree_insert(kpage); |
1480 | if (stable_node) { | |
1481 | stable_tree_append(tree_rmap_item, stable_node); | |
1482 | stable_tree_append(rmap_item, stable_node); | |
1483 | } | |
5ad64688 | 1484 | unlock_page(kpage); |
7b6ba2c7 | 1485 | |
31dbd01f IE |
1486 | /* |
1487 | * If we fail to insert the page into the stable tree, | |
1488 | * we will have 2 virtual addresses that are pointing | |
1489 | * to a ksm page left outside the stable tree, | |
1490 | * in which case we need to break_cow on both. | |
1491 | */ | |
7b6ba2c7 | 1492 | if (!stable_node) { |
8dd3557a HD |
1493 | break_cow(tree_rmap_item); |
1494 | break_cow(rmap_item); | |
31dbd01f IE |
1495 | } |
1496 | } | |
31dbd01f IE |
1497 | } |
1498 | } | |
1499 | ||
1500 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 1501 | struct rmap_item **rmap_list, |
31dbd01f IE |
1502 | unsigned long addr) |
1503 | { | |
1504 | struct rmap_item *rmap_item; | |
1505 | ||
6514d511 HD |
1506 | while (*rmap_list) { |
1507 | rmap_item = *rmap_list; | |
93d17715 | 1508 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 1509 | return rmap_item; |
31dbd01f IE |
1510 | if (rmap_item->address > addr) |
1511 | break; | |
6514d511 | 1512 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 1513 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
1514 | free_rmap_item(rmap_item); |
1515 | } | |
1516 | ||
1517 | rmap_item = alloc_rmap_item(); | |
1518 | if (rmap_item) { | |
1519 | /* It has already been zeroed */ | |
1520 | rmap_item->mm = mm_slot->mm; | |
1521 | rmap_item->address = addr; | |
6514d511 HD |
1522 | rmap_item->rmap_list = *rmap_list; |
1523 | *rmap_list = rmap_item; | |
31dbd01f IE |
1524 | } |
1525 | return rmap_item; | |
1526 | } | |
1527 | ||
1528 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
1529 | { | |
1530 | struct mm_struct *mm; | |
1531 | struct mm_slot *slot; | |
1532 | struct vm_area_struct *vma; | |
1533 | struct rmap_item *rmap_item; | |
90bd6fd3 | 1534 | int nid; |
31dbd01f IE |
1535 | |
1536 | if (list_empty(&ksm_mm_head.mm_list)) | |
1537 | return NULL; | |
1538 | ||
1539 | slot = ksm_scan.mm_slot; | |
1540 | if (slot == &ksm_mm_head) { | |
2919bfd0 HD |
1541 | /* |
1542 | * A number of pages can hang around indefinitely on per-cpu | |
1543 | * pagevecs, raised page count preventing write_protect_page | |
1544 | * from merging them. Though it doesn't really matter much, | |
1545 | * it is puzzling to see some stuck in pages_volatile until | |
1546 | * other activity jostles them out, and they also prevented | |
1547 | * LTP's KSM test from succeeding deterministically; so drain | |
1548 | * them here (here rather than on entry to ksm_do_scan(), | |
1549 | * so we don't IPI too often when pages_to_scan is set low). | |
1550 | */ | |
1551 | lru_add_drain_all(); | |
1552 | ||
4146d2d6 HD |
1553 | /* |
1554 | * Whereas stale stable_nodes on the stable_tree itself | |
1555 | * get pruned in the regular course of stable_tree_search(), | |
1556 | * those moved out to the migrate_nodes list can accumulate: | |
1557 | * so prune them once before each full scan. | |
1558 | */ | |
1559 | if (!ksm_merge_across_nodes) { | |
03640418 | 1560 | struct stable_node *stable_node, *next; |
4146d2d6 HD |
1561 | struct page *page; |
1562 | ||
03640418 GT |
1563 | list_for_each_entry_safe(stable_node, next, |
1564 | &migrate_nodes, list) { | |
4146d2d6 HD |
1565 | page = get_ksm_page(stable_node, false); |
1566 | if (page) | |
1567 | put_page(page); | |
1568 | cond_resched(); | |
1569 | } | |
1570 | } | |
1571 | ||
ef53d16c | 1572 | for (nid = 0; nid < ksm_nr_node_ids; nid++) |
90bd6fd3 | 1573 | root_unstable_tree[nid] = RB_ROOT; |
31dbd01f IE |
1574 | |
1575 | spin_lock(&ksm_mmlist_lock); | |
1576 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
1577 | ksm_scan.mm_slot = slot; | |
1578 | spin_unlock(&ksm_mmlist_lock); | |
2b472611 HD |
1579 | /* |
1580 | * Although we tested list_empty() above, a racing __ksm_exit | |
1581 | * of the last mm on the list may have removed it since then. | |
1582 | */ | |
1583 | if (slot == &ksm_mm_head) | |
1584 | return NULL; | |
31dbd01f IE |
1585 | next_mm: |
1586 | ksm_scan.address = 0; | |
6514d511 | 1587 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
1588 | } |
1589 | ||
1590 | mm = slot->mm; | |
1591 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
1592 | if (ksm_test_exit(mm)) |
1593 | vma = NULL; | |
1594 | else | |
1595 | vma = find_vma(mm, ksm_scan.address); | |
1596 | ||
1597 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
1598 | if (!(vma->vm_flags & VM_MERGEABLE)) |
1599 | continue; | |
1600 | if (ksm_scan.address < vma->vm_start) | |
1601 | ksm_scan.address = vma->vm_start; | |
1602 | if (!vma->anon_vma) | |
1603 | ksm_scan.address = vma->vm_end; | |
1604 | ||
1605 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
1606 | if (ksm_test_exit(mm)) |
1607 | break; | |
31dbd01f | 1608 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
21ae5b01 AA |
1609 | if (IS_ERR_OR_NULL(*page)) { |
1610 | ksm_scan.address += PAGE_SIZE; | |
1611 | cond_resched(); | |
1612 | continue; | |
1613 | } | |
f765f540 | 1614 | if (PageAnon(*page)) { |
31dbd01f IE |
1615 | flush_anon_page(vma, *page, ksm_scan.address); |
1616 | flush_dcache_page(*page); | |
1617 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 1618 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 1619 | if (rmap_item) { |
6514d511 HD |
1620 | ksm_scan.rmap_list = |
1621 | &rmap_item->rmap_list; | |
31dbd01f IE |
1622 | ksm_scan.address += PAGE_SIZE; |
1623 | } else | |
1624 | put_page(*page); | |
1625 | up_read(&mm->mmap_sem); | |
1626 | return rmap_item; | |
1627 | } | |
21ae5b01 | 1628 | put_page(*page); |
31dbd01f IE |
1629 | ksm_scan.address += PAGE_SIZE; |
1630 | cond_resched(); | |
1631 | } | |
1632 | } | |
1633 | ||
9ba69294 HD |
1634 | if (ksm_test_exit(mm)) { |
1635 | ksm_scan.address = 0; | |
6514d511 | 1636 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 1637 | } |
31dbd01f IE |
1638 | /* |
1639 | * Nuke all the rmap_items that are above this current rmap: | |
1640 | * because there were no VM_MERGEABLE vmas with such addresses. | |
1641 | */ | |
6514d511 | 1642 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
1643 | |
1644 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
1645 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
1646 | struct mm_slot, mm_list); | |
1647 | if (ksm_scan.address == 0) { | |
1648 | /* | |
1649 | * We've completed a full scan of all vmas, holding mmap_sem | |
1650 | * throughout, and found no VM_MERGEABLE: so do the same as | |
1651 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
1652 | * This applies either when cleaning up after __ksm_exit |
1653 | * (but beware: we can reach here even before __ksm_exit), | |
1654 | * or when all VM_MERGEABLE areas have been unmapped (and | |
1655 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 | 1656 | */ |
4ca3a69b | 1657 | hash_del(&slot->link); |
cd551f97 | 1658 | list_del(&slot->mm_list); |
9ba69294 HD |
1659 | spin_unlock(&ksm_mmlist_lock); |
1660 | ||
cd551f97 HD |
1661 | free_mm_slot(slot); |
1662 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
1663 | up_read(&mm->mmap_sem); |
1664 | mmdrop(mm); | |
1665 | } else { | |
1666 | spin_unlock(&ksm_mmlist_lock); | |
1667 | up_read(&mm->mmap_sem); | |
cd551f97 | 1668 | } |
31dbd01f IE |
1669 | |
1670 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 1671 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
1672 | if (slot != &ksm_mm_head) |
1673 | goto next_mm; | |
1674 | ||
31dbd01f IE |
1675 | ksm_scan.seqnr++; |
1676 | return NULL; | |
1677 | } | |
1678 | ||
1679 | /** | |
1680 | * ksm_do_scan - the ksm scanner main worker function. | |
1681 | * @scan_npages - number of pages we want to scan before we return. | |
1682 | */ | |
1683 | static void ksm_do_scan(unsigned int scan_npages) | |
1684 | { | |
1685 | struct rmap_item *rmap_item; | |
22eccdd7 | 1686 | struct page *uninitialized_var(page); |
31dbd01f | 1687 | |
878aee7d | 1688 | while (scan_npages-- && likely(!freezing(current))) { |
31dbd01f IE |
1689 | cond_resched(); |
1690 | rmap_item = scan_get_next_rmap_item(&page); | |
1691 | if (!rmap_item) | |
1692 | return; | |
4146d2d6 | 1693 | cmp_and_merge_page(page, rmap_item); |
31dbd01f IE |
1694 | put_page(page); |
1695 | } | |
1696 | } | |
1697 | ||
6e158384 HD |
1698 | static int ksmd_should_run(void) |
1699 | { | |
1700 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
1701 | } | |
1702 | ||
31dbd01f IE |
1703 | static int ksm_scan_thread(void *nothing) |
1704 | { | |
878aee7d | 1705 | set_freezable(); |
339aa624 | 1706 | set_user_nice(current, 5); |
31dbd01f IE |
1707 | |
1708 | while (!kthread_should_stop()) { | |
6e158384 | 1709 | mutex_lock(&ksm_thread_mutex); |
ef4d43a8 | 1710 | wait_while_offlining(); |
6e158384 | 1711 | if (ksmd_should_run()) |
31dbd01f | 1712 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
1713 | mutex_unlock(&ksm_thread_mutex); |
1714 | ||
878aee7d AA |
1715 | try_to_freeze(); |
1716 | ||
6e158384 | 1717 | if (ksmd_should_run()) { |
31dbd01f IE |
1718 | schedule_timeout_interruptible( |
1719 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
1720 | } else { | |
878aee7d | 1721 | wait_event_freezable(ksm_thread_wait, |
6e158384 | 1722 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
1723 | } |
1724 | } | |
1725 | return 0; | |
1726 | } | |
1727 | ||
f8af4da3 HD |
1728 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
1729 | unsigned long end, int advice, unsigned long *vm_flags) | |
1730 | { | |
1731 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 1732 | int err; |
f8af4da3 HD |
1733 | |
1734 | switch (advice) { | |
1735 | case MADV_MERGEABLE: | |
1736 | /* | |
1737 | * Be somewhat over-protective for now! | |
1738 | */ | |
1739 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
1740 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
0661a336 | 1741 | VM_HUGETLB | VM_MIXEDMAP)) |
f8af4da3 HD |
1742 | return 0; /* just ignore the advice */ |
1743 | ||
cc2383ec KK |
1744 | #ifdef VM_SAO |
1745 | if (*vm_flags & VM_SAO) | |
1746 | return 0; | |
1747 | #endif | |
1748 | ||
d952b791 HD |
1749 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
1750 | err = __ksm_enter(mm); | |
1751 | if (err) | |
1752 | return err; | |
1753 | } | |
f8af4da3 HD |
1754 | |
1755 | *vm_flags |= VM_MERGEABLE; | |
1756 | break; | |
1757 | ||
1758 | case MADV_UNMERGEABLE: | |
1759 | if (!(*vm_flags & VM_MERGEABLE)) | |
1760 | return 0; /* just ignore the advice */ | |
1761 | ||
d952b791 HD |
1762 | if (vma->anon_vma) { |
1763 | err = unmerge_ksm_pages(vma, start, end); | |
1764 | if (err) | |
1765 | return err; | |
1766 | } | |
f8af4da3 HD |
1767 | |
1768 | *vm_flags &= ~VM_MERGEABLE; | |
1769 | break; | |
1770 | } | |
1771 | ||
1772 | return 0; | |
1773 | } | |
1774 | ||
1775 | int __ksm_enter(struct mm_struct *mm) | |
1776 | { | |
6e158384 HD |
1777 | struct mm_slot *mm_slot; |
1778 | int needs_wakeup; | |
1779 | ||
1780 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
1781 | if (!mm_slot) |
1782 | return -ENOMEM; | |
1783 | ||
6e158384 HD |
1784 | /* Check ksm_run too? Would need tighter locking */ |
1785 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
1786 | ||
31dbd01f IE |
1787 | spin_lock(&ksm_mmlist_lock); |
1788 | insert_to_mm_slots_hash(mm, mm_slot); | |
1789 | /* | |
cbf86cfe HD |
1790 | * When KSM_RUN_MERGE (or KSM_RUN_STOP), |
1791 | * insert just behind the scanning cursor, to let the area settle | |
31dbd01f IE |
1792 | * down a little; when fork is followed by immediate exec, we don't |
1793 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
cbf86cfe HD |
1794 | * |
1795 | * But when KSM_RUN_UNMERGE, it's important to insert ahead of its | |
1796 | * scanning cursor, otherwise KSM pages in newly forked mms will be | |
1797 | * missed: then we might as well insert at the end of the list. | |
31dbd01f | 1798 | */ |
cbf86cfe HD |
1799 | if (ksm_run & KSM_RUN_UNMERGE) |
1800 | list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); | |
1801 | else | |
1802 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
31dbd01f IE |
1803 | spin_unlock(&ksm_mmlist_lock); |
1804 | ||
f8af4da3 | 1805 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
9ba69294 | 1806 | atomic_inc(&mm->mm_count); |
6e158384 HD |
1807 | |
1808 | if (needs_wakeup) | |
1809 | wake_up_interruptible(&ksm_thread_wait); | |
1810 | ||
f8af4da3 HD |
1811 | return 0; |
1812 | } | |
1813 | ||
1c2fb7a4 | 1814 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 1815 | { |
cd551f97 | 1816 | struct mm_slot *mm_slot; |
9ba69294 | 1817 | int easy_to_free = 0; |
cd551f97 | 1818 | |
31dbd01f | 1819 | /* |
9ba69294 HD |
1820 | * This process is exiting: if it's straightforward (as is the |
1821 | * case when ksmd was never running), free mm_slot immediately. | |
1822 | * But if it's at the cursor or has rmap_items linked to it, use | |
1823 | * mmap_sem to synchronize with any break_cows before pagetables | |
1824 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
1825 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 1826 | */ |
9ba69294 | 1827 | |
cd551f97 HD |
1828 | spin_lock(&ksm_mmlist_lock); |
1829 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 1830 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 1831 | if (!mm_slot->rmap_list) { |
4ca3a69b | 1832 | hash_del(&mm_slot->link); |
9ba69294 HD |
1833 | list_del(&mm_slot->mm_list); |
1834 | easy_to_free = 1; | |
1835 | } else { | |
1836 | list_move(&mm_slot->mm_list, | |
1837 | &ksm_scan.mm_slot->mm_list); | |
1838 | } | |
cd551f97 | 1839 | } |
cd551f97 HD |
1840 | spin_unlock(&ksm_mmlist_lock); |
1841 | ||
9ba69294 HD |
1842 | if (easy_to_free) { |
1843 | free_mm_slot(mm_slot); | |
1844 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
1845 | mmdrop(mm); | |
1846 | } else if (mm_slot) { | |
9ba69294 HD |
1847 | down_write(&mm->mmap_sem); |
1848 | up_write(&mm->mmap_sem); | |
9ba69294 | 1849 | } |
31dbd01f IE |
1850 | } |
1851 | ||
cbf86cfe | 1852 | struct page *ksm_might_need_to_copy(struct page *page, |
5ad64688 HD |
1853 | struct vm_area_struct *vma, unsigned long address) |
1854 | { | |
cbf86cfe | 1855 | struct anon_vma *anon_vma = page_anon_vma(page); |
5ad64688 HD |
1856 | struct page *new_page; |
1857 | ||
cbf86cfe HD |
1858 | if (PageKsm(page)) { |
1859 | if (page_stable_node(page) && | |
1860 | !(ksm_run & KSM_RUN_UNMERGE)) | |
1861 | return page; /* no need to copy it */ | |
1862 | } else if (!anon_vma) { | |
1863 | return page; /* no need to copy it */ | |
1864 | } else if (anon_vma->root == vma->anon_vma->root && | |
1865 | page->index == linear_page_index(vma, address)) { | |
1866 | return page; /* still no need to copy it */ | |
1867 | } | |
1868 | if (!PageUptodate(page)) | |
1869 | return page; /* let do_swap_page report the error */ | |
1870 | ||
5ad64688 HD |
1871 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
1872 | if (new_page) { | |
1873 | copy_user_highpage(new_page, page, address, vma); | |
1874 | ||
1875 | SetPageDirty(new_page); | |
1876 | __SetPageUptodate(new_page); | |
48c935ad | 1877 | __SetPageLocked(new_page); |
5ad64688 HD |
1878 | } |
1879 | ||
5ad64688 HD |
1880 | return new_page; |
1881 | } | |
1882 | ||
051ac83a | 1883 | int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc) |
e9995ef9 HD |
1884 | { |
1885 | struct stable_node *stable_node; | |
e9995ef9 HD |
1886 | struct rmap_item *rmap_item; |
1887 | int ret = SWAP_AGAIN; | |
1888 | int search_new_forks = 0; | |
1889 | ||
309381fe | 1890 | VM_BUG_ON_PAGE(!PageKsm(page), page); |
9f32624b JK |
1891 | |
1892 | /* | |
1893 | * Rely on the page lock to protect against concurrent modifications | |
1894 | * to that page's node of the stable tree. | |
1895 | */ | |
309381fe | 1896 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
e9995ef9 HD |
1897 | |
1898 | stable_node = page_stable_node(page); | |
1899 | if (!stable_node) | |
1900 | return ret; | |
1901 | again: | |
b67bfe0d | 1902 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
e9995ef9 | 1903 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 1904 | struct anon_vma_chain *vmac; |
e9995ef9 HD |
1905 | struct vm_area_struct *vma; |
1906 | ||
ad12695f | 1907 | cond_resched(); |
b6b19f25 | 1908 | anon_vma_lock_read(anon_vma); |
bf181b9f ML |
1909 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
1910 | 0, ULONG_MAX) { | |
ad12695f | 1911 | cond_resched(); |
5beb4930 | 1912 | vma = vmac->vma; |
e9995ef9 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 | ||
0dd1c7bb JK |
1925 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
1926 | continue; | |
1927 | ||
051ac83a JK |
1928 | ret = rwc->rmap_one(page, vma, |
1929 | rmap_item->address, rwc->arg); | |
e9995ef9 | 1930 | if (ret != SWAP_AGAIN) { |
b6b19f25 | 1931 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
1932 | goto out; |
1933 | } | |
0dd1c7bb JK |
1934 | if (rwc->done && rwc->done(page)) { |
1935 | anon_vma_unlock_read(anon_vma); | |
1936 | goto out; | |
1937 | } | |
e9995ef9 | 1938 | } |
b6b19f25 | 1939 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
1940 | } |
1941 | if (!search_new_forks++) | |
1942 | goto again; | |
1943 | out: | |
1944 | return ret; | |
1945 | } | |
1946 | ||
52629506 | 1947 | #ifdef CONFIG_MIGRATION |
e9995ef9 HD |
1948 | void ksm_migrate_page(struct page *newpage, struct page *oldpage) |
1949 | { | |
1950 | struct stable_node *stable_node; | |
1951 | ||
309381fe SL |
1952 | VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); |
1953 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); | |
1954 | VM_BUG_ON_PAGE(newpage->mapping != oldpage->mapping, newpage); | |
e9995ef9 HD |
1955 | |
1956 | stable_node = page_stable_node(newpage); | |
1957 | if (stable_node) { | |
309381fe | 1958 | VM_BUG_ON_PAGE(stable_node->kpfn != page_to_pfn(oldpage), oldpage); |
62b61f61 | 1959 | stable_node->kpfn = page_to_pfn(newpage); |
c8d6553b HD |
1960 | /* |
1961 | * newpage->mapping was set in advance; now we need smp_wmb() | |
1962 | * to make sure that the new stable_node->kpfn is visible | |
1963 | * to get_ksm_page() before it can see that oldpage->mapping | |
1964 | * has gone stale (or that PageSwapCache has been cleared). | |
1965 | */ | |
1966 | smp_wmb(); | |
1967 | set_page_stable_node(oldpage, NULL); | |
e9995ef9 HD |
1968 | } |
1969 | } | |
1970 | #endif /* CONFIG_MIGRATION */ | |
1971 | ||
62b61f61 | 1972 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 HD |
1973 | static void wait_while_offlining(void) |
1974 | { | |
1975 | while (ksm_run & KSM_RUN_OFFLINE) { | |
1976 | mutex_unlock(&ksm_thread_mutex); | |
1977 | wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), | |
74316201 | 1978 | TASK_UNINTERRUPTIBLE); |
ef4d43a8 HD |
1979 | mutex_lock(&ksm_thread_mutex); |
1980 | } | |
1981 | } | |
1982 | ||
ee0ea59c HD |
1983 | static void ksm_check_stable_tree(unsigned long start_pfn, |
1984 | unsigned long end_pfn) | |
62b61f61 | 1985 | { |
03640418 | 1986 | struct stable_node *stable_node, *next; |
62b61f61 | 1987 | struct rb_node *node; |
90bd6fd3 | 1988 | int nid; |
62b61f61 | 1989 | |
ef53d16c HD |
1990 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
1991 | node = rb_first(root_stable_tree + nid); | |
ee0ea59c | 1992 | while (node) { |
90bd6fd3 PH |
1993 | stable_node = rb_entry(node, struct stable_node, node); |
1994 | if (stable_node->kpfn >= start_pfn && | |
ee0ea59c HD |
1995 | stable_node->kpfn < end_pfn) { |
1996 | /* | |
1997 | * Don't get_ksm_page, page has already gone: | |
1998 | * which is why we keep kpfn instead of page* | |
1999 | */ | |
2000 | remove_node_from_stable_tree(stable_node); | |
ef53d16c | 2001 | node = rb_first(root_stable_tree + nid); |
ee0ea59c HD |
2002 | } else |
2003 | node = rb_next(node); | |
2004 | cond_resched(); | |
90bd6fd3 | 2005 | } |
ee0ea59c | 2006 | } |
03640418 | 2007 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
2008 | if (stable_node->kpfn >= start_pfn && |
2009 | stable_node->kpfn < end_pfn) | |
2010 | remove_node_from_stable_tree(stable_node); | |
2011 | cond_resched(); | |
2012 | } | |
62b61f61 HD |
2013 | } |
2014 | ||
2015 | static int ksm_memory_callback(struct notifier_block *self, | |
2016 | unsigned long action, void *arg) | |
2017 | { | |
2018 | struct memory_notify *mn = arg; | |
62b61f61 HD |
2019 | |
2020 | switch (action) { | |
2021 | case MEM_GOING_OFFLINE: | |
2022 | /* | |
ef4d43a8 HD |
2023 | * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() |
2024 | * and remove_all_stable_nodes() while memory is going offline: | |
2025 | * it is unsafe for them to touch the stable tree at this time. | |
2026 | * But unmerge_ksm_pages(), rmap lookups and other entry points | |
2027 | * which do not need the ksm_thread_mutex are all safe. | |
62b61f61 | 2028 | */ |
ef4d43a8 HD |
2029 | mutex_lock(&ksm_thread_mutex); |
2030 | ksm_run |= KSM_RUN_OFFLINE; | |
2031 | mutex_unlock(&ksm_thread_mutex); | |
62b61f61 HD |
2032 | break; |
2033 | ||
2034 | case MEM_OFFLINE: | |
2035 | /* | |
2036 | * Most of the work is done by page migration; but there might | |
2037 | * be a few stable_nodes left over, still pointing to struct | |
ee0ea59c HD |
2038 | * pages which have been offlined: prune those from the tree, |
2039 | * otherwise get_ksm_page() might later try to access a | |
2040 | * non-existent struct page. | |
62b61f61 | 2041 | */ |
ee0ea59c HD |
2042 | ksm_check_stable_tree(mn->start_pfn, |
2043 | mn->start_pfn + mn->nr_pages); | |
62b61f61 HD |
2044 | /* fallthrough */ |
2045 | ||
2046 | case MEM_CANCEL_OFFLINE: | |
ef4d43a8 HD |
2047 | mutex_lock(&ksm_thread_mutex); |
2048 | ksm_run &= ~KSM_RUN_OFFLINE; | |
62b61f61 | 2049 | mutex_unlock(&ksm_thread_mutex); |
ef4d43a8 HD |
2050 | |
2051 | smp_mb(); /* wake_up_bit advises this */ | |
2052 | wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); | |
62b61f61 HD |
2053 | break; |
2054 | } | |
2055 | return NOTIFY_OK; | |
2056 | } | |
ef4d43a8 HD |
2057 | #else |
2058 | static void wait_while_offlining(void) | |
2059 | { | |
2060 | } | |
62b61f61 HD |
2061 | #endif /* CONFIG_MEMORY_HOTREMOVE */ |
2062 | ||
2ffd8679 HD |
2063 | #ifdef CONFIG_SYSFS |
2064 | /* | |
2065 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
2066 | */ | |
2067 | ||
31dbd01f IE |
2068 | #define KSM_ATTR_RO(_name) \ |
2069 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
2070 | #define KSM_ATTR(_name) \ | |
2071 | static struct kobj_attribute _name##_attr = \ | |
2072 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
2073 | ||
2074 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
2075 | struct kobj_attribute *attr, char *buf) | |
2076 | { | |
2077 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
2078 | } | |
2079 | ||
2080 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
2081 | struct kobj_attribute *attr, | |
2082 | const char *buf, size_t count) | |
2083 | { | |
2084 | unsigned long msecs; | |
2085 | int err; | |
2086 | ||
3dbb95f7 | 2087 | err = kstrtoul(buf, 10, &msecs); |
31dbd01f IE |
2088 | if (err || msecs > UINT_MAX) |
2089 | return -EINVAL; | |
2090 | ||
2091 | ksm_thread_sleep_millisecs = msecs; | |
2092 | ||
2093 | return count; | |
2094 | } | |
2095 | KSM_ATTR(sleep_millisecs); | |
2096 | ||
2097 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
2098 | struct kobj_attribute *attr, char *buf) | |
2099 | { | |
2100 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
2101 | } | |
2102 | ||
2103 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
2104 | struct kobj_attribute *attr, | |
2105 | const char *buf, size_t count) | |
2106 | { | |
2107 | int err; | |
2108 | unsigned long nr_pages; | |
2109 | ||
3dbb95f7 | 2110 | err = kstrtoul(buf, 10, &nr_pages); |
31dbd01f IE |
2111 | if (err || nr_pages > UINT_MAX) |
2112 | return -EINVAL; | |
2113 | ||
2114 | ksm_thread_pages_to_scan = nr_pages; | |
2115 | ||
2116 | return count; | |
2117 | } | |
2118 | KSM_ATTR(pages_to_scan); | |
2119 | ||
2120 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
2121 | char *buf) | |
2122 | { | |
ef4d43a8 | 2123 | return sprintf(buf, "%lu\n", ksm_run); |
31dbd01f IE |
2124 | } |
2125 | ||
2126 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
2127 | const char *buf, size_t count) | |
2128 | { | |
2129 | int err; | |
2130 | unsigned long flags; | |
2131 | ||
3dbb95f7 | 2132 | err = kstrtoul(buf, 10, &flags); |
31dbd01f IE |
2133 | if (err || flags > UINT_MAX) |
2134 | return -EINVAL; | |
2135 | if (flags > KSM_RUN_UNMERGE) | |
2136 | return -EINVAL; | |
2137 | ||
2138 | /* | |
2139 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
2140 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
d0f209f6 HD |
2141 | * breaking COW to free the pages_shared (but leaves mm_slots |
2142 | * on the list for when ksmd may be set running again). | |
31dbd01f IE |
2143 | */ |
2144 | ||
2145 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2146 | wait_while_offlining(); |
31dbd01f IE |
2147 | if (ksm_run != flags) { |
2148 | ksm_run = flags; | |
d952b791 | 2149 | if (flags & KSM_RUN_UNMERGE) { |
e1e12d2f | 2150 | set_current_oom_origin(); |
d952b791 | 2151 | err = unmerge_and_remove_all_rmap_items(); |
e1e12d2f | 2152 | clear_current_oom_origin(); |
d952b791 HD |
2153 | if (err) { |
2154 | ksm_run = KSM_RUN_STOP; | |
2155 | count = err; | |
2156 | } | |
2157 | } | |
31dbd01f IE |
2158 | } |
2159 | mutex_unlock(&ksm_thread_mutex); | |
2160 | ||
2161 | if (flags & KSM_RUN_MERGE) | |
2162 | wake_up_interruptible(&ksm_thread_wait); | |
2163 | ||
2164 | return count; | |
2165 | } | |
2166 | KSM_ATTR(run); | |
2167 | ||
90bd6fd3 PH |
2168 | #ifdef CONFIG_NUMA |
2169 | static ssize_t merge_across_nodes_show(struct kobject *kobj, | |
2170 | struct kobj_attribute *attr, char *buf) | |
2171 | { | |
2172 | return sprintf(buf, "%u\n", ksm_merge_across_nodes); | |
2173 | } | |
2174 | ||
2175 | static ssize_t merge_across_nodes_store(struct kobject *kobj, | |
2176 | struct kobj_attribute *attr, | |
2177 | const char *buf, size_t count) | |
2178 | { | |
2179 | int err; | |
2180 | unsigned long knob; | |
2181 | ||
2182 | err = kstrtoul(buf, 10, &knob); | |
2183 | if (err) | |
2184 | return err; | |
2185 | if (knob > 1) | |
2186 | return -EINVAL; | |
2187 | ||
2188 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2189 | wait_while_offlining(); |
90bd6fd3 | 2190 | if (ksm_merge_across_nodes != knob) { |
cbf86cfe | 2191 | if (ksm_pages_shared || remove_all_stable_nodes()) |
90bd6fd3 | 2192 | err = -EBUSY; |
ef53d16c HD |
2193 | else if (root_stable_tree == one_stable_tree) { |
2194 | struct rb_root *buf; | |
2195 | /* | |
2196 | * This is the first time that we switch away from the | |
2197 | * default of merging across nodes: must now allocate | |
2198 | * a buffer to hold as many roots as may be needed. | |
2199 | * Allocate stable and unstable together: | |
2200 | * MAXSMP NODES_SHIFT 10 will use 16kB. | |
2201 | */ | |
bafe1e14 JP |
2202 | buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf), |
2203 | GFP_KERNEL); | |
ef53d16c HD |
2204 | /* Let us assume that RB_ROOT is NULL is zero */ |
2205 | if (!buf) | |
2206 | err = -ENOMEM; | |
2207 | else { | |
2208 | root_stable_tree = buf; | |
2209 | root_unstable_tree = buf + nr_node_ids; | |
2210 | /* Stable tree is empty but not the unstable */ | |
2211 | root_unstable_tree[0] = one_unstable_tree[0]; | |
2212 | } | |
2213 | } | |
2214 | if (!err) { | |
90bd6fd3 | 2215 | ksm_merge_across_nodes = knob; |
ef53d16c HD |
2216 | ksm_nr_node_ids = knob ? 1 : nr_node_ids; |
2217 | } | |
90bd6fd3 PH |
2218 | } |
2219 | mutex_unlock(&ksm_thread_mutex); | |
2220 | ||
2221 | return err ? err : count; | |
2222 | } | |
2223 | KSM_ATTR(merge_across_nodes); | |
2224 | #endif | |
2225 | ||
b4028260 HD |
2226 | static ssize_t pages_shared_show(struct kobject *kobj, |
2227 | struct kobj_attribute *attr, char *buf) | |
2228 | { | |
2229 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
2230 | } | |
2231 | KSM_ATTR_RO(pages_shared); | |
2232 | ||
2233 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
2234 | struct kobj_attribute *attr, char *buf) | |
2235 | { | |
e178dfde | 2236 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
2237 | } |
2238 | KSM_ATTR_RO(pages_sharing); | |
2239 | ||
473b0ce4 HD |
2240 | static ssize_t pages_unshared_show(struct kobject *kobj, |
2241 | struct kobj_attribute *attr, char *buf) | |
2242 | { | |
2243 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
2244 | } | |
2245 | KSM_ATTR_RO(pages_unshared); | |
2246 | ||
2247 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
2248 | struct kobj_attribute *attr, char *buf) | |
2249 | { | |
2250 | long ksm_pages_volatile; | |
2251 | ||
2252 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
2253 | - ksm_pages_sharing - ksm_pages_unshared; | |
2254 | /* | |
2255 | * It was not worth any locking to calculate that statistic, | |
2256 | * but it might therefore sometimes be negative: conceal that. | |
2257 | */ | |
2258 | if (ksm_pages_volatile < 0) | |
2259 | ksm_pages_volatile = 0; | |
2260 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
2261 | } | |
2262 | KSM_ATTR_RO(pages_volatile); | |
2263 | ||
2264 | static ssize_t full_scans_show(struct kobject *kobj, | |
2265 | struct kobj_attribute *attr, char *buf) | |
2266 | { | |
2267 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
2268 | } | |
2269 | KSM_ATTR_RO(full_scans); | |
2270 | ||
31dbd01f IE |
2271 | static struct attribute *ksm_attrs[] = { |
2272 | &sleep_millisecs_attr.attr, | |
2273 | &pages_to_scan_attr.attr, | |
2274 | &run_attr.attr, | |
b4028260 HD |
2275 | &pages_shared_attr.attr, |
2276 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
2277 | &pages_unshared_attr.attr, |
2278 | &pages_volatile_attr.attr, | |
2279 | &full_scans_attr.attr, | |
90bd6fd3 PH |
2280 | #ifdef CONFIG_NUMA |
2281 | &merge_across_nodes_attr.attr, | |
2282 | #endif | |
31dbd01f IE |
2283 | NULL, |
2284 | }; | |
2285 | ||
2286 | static struct attribute_group ksm_attr_group = { | |
2287 | .attrs = ksm_attrs, | |
2288 | .name = "ksm", | |
2289 | }; | |
2ffd8679 | 2290 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
2291 | |
2292 | static int __init ksm_init(void) | |
2293 | { | |
2294 | struct task_struct *ksm_thread; | |
2295 | int err; | |
2296 | ||
2297 | err = ksm_slab_init(); | |
2298 | if (err) | |
2299 | goto out; | |
2300 | ||
31dbd01f IE |
2301 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
2302 | if (IS_ERR(ksm_thread)) { | |
25acde31 | 2303 | pr_err("ksm: creating kthread failed\n"); |
31dbd01f | 2304 | err = PTR_ERR(ksm_thread); |
d9f8984c | 2305 | goto out_free; |
31dbd01f IE |
2306 | } |
2307 | ||
2ffd8679 | 2308 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
2309 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
2310 | if (err) { | |
25acde31 | 2311 | pr_err("ksm: register sysfs failed\n"); |
2ffd8679 | 2312 | kthread_stop(ksm_thread); |
d9f8984c | 2313 | goto out_free; |
31dbd01f | 2314 | } |
c73602ad HD |
2315 | #else |
2316 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
2317 | ||
2ffd8679 | 2318 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 2319 | |
62b61f61 | 2320 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 | 2321 | /* There is no significance to this priority 100 */ |
62b61f61 HD |
2322 | hotplug_memory_notifier(ksm_memory_callback, 100); |
2323 | #endif | |
31dbd01f IE |
2324 | return 0; |
2325 | ||
d9f8984c | 2326 | out_free: |
31dbd01f IE |
2327 | ksm_slab_free(); |
2328 | out: | |
2329 | return err; | |
f8af4da3 | 2330 | } |
a64fb3cd | 2331 | subsys_initcall(ksm_init); |