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Commit | Line | Data |
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f8af4da3 | 1 | /* |
31dbd01f IE |
2 | * Memory merging support. |
3 | * | |
4 | * This code enables dynamic sharing of identical pages found in different | |
5 | * memory areas, even if they are not shared by fork() | |
6 | * | |
36b2528d | 7 | * Copyright (C) 2008-2009 Red Hat, Inc. |
31dbd01f IE |
8 | * Authors: |
9 | * Izik Eidus | |
10 | * Andrea Arcangeli | |
11 | * Chris Wright | |
36b2528d | 12 | * Hugh Dickins |
31dbd01f IE |
13 | * |
14 | * This work is licensed under the terms of the GNU GPL, version 2. | |
f8af4da3 HD |
15 | */ |
16 | ||
17 | #include <linux/errno.h> | |
31dbd01f IE |
18 | #include <linux/mm.h> |
19 | #include <linux/fs.h> | |
f8af4da3 | 20 | #include <linux/mman.h> |
31dbd01f | 21 | #include <linux/sched.h> |
6e84f315 | 22 | #include <linux/sched/mm.h> |
f7ccbae4 | 23 | #include <linux/sched/coredump.h> |
31dbd01f IE |
24 | #include <linux/rwsem.h> |
25 | #include <linux/pagemap.h> | |
26 | #include <linux/rmap.h> | |
27 | #include <linux/spinlock.h> | |
28 | #include <linux/jhash.h> | |
29 | #include <linux/delay.h> | |
30 | #include <linux/kthread.h> | |
31 | #include <linux/wait.h> | |
32 | #include <linux/slab.h> | |
33 | #include <linux/rbtree.h> | |
62b61f61 | 34 | #include <linux/memory.h> |
31dbd01f | 35 | #include <linux/mmu_notifier.h> |
2c6854fd | 36 | #include <linux/swap.h> |
f8af4da3 | 37 | #include <linux/ksm.h> |
4ca3a69b | 38 | #include <linux/hashtable.h> |
878aee7d | 39 | #include <linux/freezer.h> |
72788c38 | 40 | #include <linux/oom.h> |
90bd6fd3 | 41 | #include <linux/numa.h> |
f8af4da3 | 42 | |
31dbd01f | 43 | #include <asm/tlbflush.h> |
73848b46 | 44 | #include "internal.h" |
31dbd01f | 45 | |
e850dcf5 HD |
46 | #ifdef CONFIG_NUMA |
47 | #define NUMA(x) (x) | |
48 | #define DO_NUMA(x) do { (x); } while (0) | |
49 | #else | |
50 | #define NUMA(x) (0) | |
51 | #define DO_NUMA(x) do { } while (0) | |
52 | #endif | |
53 | ||
31dbd01f IE |
54 | /* |
55 | * A few notes about the KSM scanning process, | |
56 | * to make it easier to understand the data structures below: | |
57 | * | |
58 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
59 | * contents into a data structure that holds pointers to the pages' locations. | |
60 | * | |
61 | * Since the contents of the pages may change at any moment, KSM cannot just | |
62 | * insert the pages into a normal sorted tree and expect it to find anything. | |
63 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
64 | * | |
65 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
66 | * by their contents. Because each such page is write-protected, searching on | |
67 | * this tree is fully assured to be working (except when pages are unmapped), | |
68 | * and therefore this tree is called the stable tree. | |
69 | * | |
70 | * In addition to the stable tree, KSM uses a second data structure called the | |
71 | * unstable tree: this tree holds pointers to pages which have been found to | |
72 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
73 | * by their contents, but since they are not write-protected, KSM cannot rely | |
74 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
75 | * be corrupted as its contents are modified, and so it is called unstable. | |
76 | * | |
77 | * KSM solves this problem by several techniques: | |
78 | * | |
79 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
80 | * memory areas, and then the tree is rebuilt again from the beginning. | |
81 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
82 | * has not changed since the previous scan of all memory areas. | |
83 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
84 | * colors of the nodes and not on their contents, assuring that even when | |
85 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
86 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
87 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
88 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
89 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
90 | * it is secured in the stable tree. (When we scan a new page, we first | |
91 | * compare it against the stable tree, and then against the unstable tree.) | |
8fdb3dbf HD |
92 | * |
93 | * If the merge_across_nodes tunable is unset, then KSM maintains multiple | |
94 | * stable trees and multiple unstable trees: one of each for each NUMA node. | |
31dbd01f IE |
95 | */ |
96 | ||
97 | /** | |
98 | * struct mm_slot - ksm information per mm that is being scanned | |
99 | * @link: link to the mm_slots hash list | |
100 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head | |
6514d511 | 101 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
102 | * @mm: the mm that this information is valid for |
103 | */ | |
104 | struct mm_slot { | |
105 | struct hlist_node link; | |
106 | struct list_head mm_list; | |
6514d511 | 107 | struct rmap_item *rmap_list; |
31dbd01f IE |
108 | struct mm_struct *mm; |
109 | }; | |
110 | ||
111 | /** | |
112 | * struct ksm_scan - cursor for scanning | |
113 | * @mm_slot: the current mm_slot we are scanning | |
114 | * @address: the next address inside that to be scanned | |
6514d511 | 115 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
116 | * @seqnr: count of completed full scans (needed when removing unstable node) |
117 | * | |
118 | * There is only the one ksm_scan instance of this cursor structure. | |
119 | */ | |
120 | struct ksm_scan { | |
121 | struct mm_slot *mm_slot; | |
122 | unsigned long address; | |
6514d511 | 123 | struct rmap_item **rmap_list; |
31dbd01f IE |
124 | unsigned long seqnr; |
125 | }; | |
126 | ||
7b6ba2c7 HD |
127 | /** |
128 | * struct stable_node - node of the stable rbtree | |
129 | * @node: rb node of this ksm page in the stable tree | |
4146d2d6 | 130 | * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list |
2c653d0e | 131 | * @hlist_dup: linked into the stable_node->hlist with a stable_node chain |
4146d2d6 | 132 | * @list: linked into migrate_nodes, pending placement in the proper node tree |
7b6ba2c7 | 133 | * @hlist: hlist head of rmap_items using this ksm page |
4146d2d6 | 134 | * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid) |
2c653d0e AA |
135 | * @chain_prune_time: time of the last full garbage collection |
136 | * @rmap_hlist_len: number of rmap_item entries in hlist or STABLE_NODE_CHAIN | |
4146d2d6 | 137 | * @nid: NUMA node id of stable tree in which linked (may not match kpfn) |
7b6ba2c7 HD |
138 | */ |
139 | struct stable_node { | |
4146d2d6 HD |
140 | union { |
141 | struct rb_node node; /* when node of stable tree */ | |
142 | struct { /* when listed for migration */ | |
143 | struct list_head *head; | |
2c653d0e AA |
144 | struct { |
145 | struct hlist_node hlist_dup; | |
146 | struct list_head list; | |
147 | }; | |
4146d2d6 HD |
148 | }; |
149 | }; | |
7b6ba2c7 | 150 | struct hlist_head hlist; |
2c653d0e AA |
151 | union { |
152 | unsigned long kpfn; | |
153 | unsigned long chain_prune_time; | |
154 | }; | |
155 | /* | |
156 | * STABLE_NODE_CHAIN can be any negative number in | |
157 | * rmap_hlist_len negative range, but better not -1 to be able | |
158 | * to reliably detect underflows. | |
159 | */ | |
160 | #define STABLE_NODE_CHAIN -1024 | |
161 | int rmap_hlist_len; | |
4146d2d6 HD |
162 | #ifdef CONFIG_NUMA |
163 | int nid; | |
164 | #endif | |
7b6ba2c7 HD |
165 | }; |
166 | ||
31dbd01f IE |
167 | /** |
168 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 | 169 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
db114b83 | 170 | * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree |
bc56620b | 171 | * @nid: NUMA node id of unstable tree in which linked (may not match page) |
31dbd01f IE |
172 | * @mm: the memory structure this rmap_item is pointing into |
173 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
174 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
175 | * @node: rb node of this rmap_item in the unstable tree |
176 | * @head: pointer to stable_node heading this list in the stable tree | |
177 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
178 | */ |
179 | struct rmap_item { | |
6514d511 | 180 | struct rmap_item *rmap_list; |
bc56620b HD |
181 | union { |
182 | struct anon_vma *anon_vma; /* when stable */ | |
183 | #ifdef CONFIG_NUMA | |
184 | int nid; /* when node of unstable tree */ | |
185 | #endif | |
186 | }; | |
31dbd01f IE |
187 | struct mm_struct *mm; |
188 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 189 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 190 | union { |
7b6ba2c7 HD |
191 | struct rb_node node; /* when node of unstable tree */ |
192 | struct { /* when listed from stable tree */ | |
193 | struct stable_node *head; | |
194 | struct hlist_node hlist; | |
195 | }; | |
31dbd01f IE |
196 | }; |
197 | }; | |
198 | ||
199 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
200 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
201 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
202 | |
203 | /* The stable and unstable tree heads */ | |
ef53d16c HD |
204 | static struct rb_root one_stable_tree[1] = { RB_ROOT }; |
205 | static struct rb_root one_unstable_tree[1] = { RB_ROOT }; | |
206 | static struct rb_root *root_stable_tree = one_stable_tree; | |
207 | static struct rb_root *root_unstable_tree = one_unstable_tree; | |
31dbd01f | 208 | |
4146d2d6 HD |
209 | /* Recently migrated nodes of stable tree, pending proper placement */ |
210 | static LIST_HEAD(migrate_nodes); | |
2c653d0e | 211 | #define STABLE_NODE_DUP_HEAD ((struct list_head *)&migrate_nodes.prev) |
4146d2d6 | 212 | |
4ca3a69b SL |
213 | #define MM_SLOTS_HASH_BITS 10 |
214 | static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
31dbd01f IE |
215 | |
216 | static struct mm_slot ksm_mm_head = { | |
217 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
218 | }; | |
219 | static struct ksm_scan ksm_scan = { | |
220 | .mm_slot = &ksm_mm_head, | |
221 | }; | |
222 | ||
223 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 224 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
225 | static struct kmem_cache *mm_slot_cache; |
226 | ||
227 | /* The number of nodes in the stable tree */ | |
b4028260 | 228 | static unsigned long ksm_pages_shared; |
31dbd01f | 229 | |
e178dfde | 230 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 231 | static unsigned long ksm_pages_sharing; |
31dbd01f | 232 | |
473b0ce4 HD |
233 | /* The number of nodes in the unstable tree */ |
234 | static unsigned long ksm_pages_unshared; | |
235 | ||
236 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
237 | static unsigned long ksm_rmap_items; | |
238 | ||
2c653d0e AA |
239 | /* The number of stable_node chains */ |
240 | static unsigned long ksm_stable_node_chains; | |
241 | ||
242 | /* The number of stable_node dups linked to the stable_node chains */ | |
243 | static unsigned long ksm_stable_node_dups; | |
244 | ||
245 | /* Delay in pruning stale stable_node_dups in the stable_node_chains */ | |
246 | static int ksm_stable_node_chains_prune_millisecs = 2000; | |
247 | ||
248 | /* Maximum number of page slots sharing a stable node */ | |
249 | static int ksm_max_page_sharing = 256; | |
250 | ||
31dbd01f | 251 | /* Number of pages ksmd should scan in one batch */ |
2c6854fd | 252 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
253 | |
254 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 255 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f | 256 | |
e86c59b1 CI |
257 | /* Checksum of an empty (zeroed) page */ |
258 | static unsigned int zero_checksum __read_mostly; | |
259 | ||
260 | /* Whether to merge empty (zeroed) pages with actual zero pages */ | |
261 | static bool ksm_use_zero_pages __read_mostly; | |
262 | ||
e850dcf5 | 263 | #ifdef CONFIG_NUMA |
90bd6fd3 PH |
264 | /* Zeroed when merging across nodes is not allowed */ |
265 | static unsigned int ksm_merge_across_nodes = 1; | |
ef53d16c | 266 | static int ksm_nr_node_ids = 1; |
e850dcf5 HD |
267 | #else |
268 | #define ksm_merge_across_nodes 1U | |
ef53d16c | 269 | #define ksm_nr_node_ids 1 |
e850dcf5 | 270 | #endif |
90bd6fd3 | 271 | |
31dbd01f IE |
272 | #define KSM_RUN_STOP 0 |
273 | #define KSM_RUN_MERGE 1 | |
274 | #define KSM_RUN_UNMERGE 2 | |
ef4d43a8 HD |
275 | #define KSM_RUN_OFFLINE 4 |
276 | static unsigned long ksm_run = KSM_RUN_STOP; | |
277 | static void wait_while_offlining(void); | |
31dbd01f IE |
278 | |
279 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
280 | static DEFINE_MUTEX(ksm_thread_mutex); | |
281 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
282 | ||
283 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
284 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
285 | (__flags), NULL) | |
286 | ||
287 | static int __init ksm_slab_init(void) | |
288 | { | |
289 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
290 | if (!rmap_item_cache) | |
291 | goto out; | |
292 | ||
7b6ba2c7 HD |
293 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
294 | if (!stable_node_cache) | |
295 | goto out_free1; | |
296 | ||
31dbd01f IE |
297 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
298 | if (!mm_slot_cache) | |
7b6ba2c7 | 299 | goto out_free2; |
31dbd01f IE |
300 | |
301 | return 0; | |
302 | ||
7b6ba2c7 HD |
303 | out_free2: |
304 | kmem_cache_destroy(stable_node_cache); | |
305 | out_free1: | |
31dbd01f IE |
306 | kmem_cache_destroy(rmap_item_cache); |
307 | out: | |
308 | return -ENOMEM; | |
309 | } | |
310 | ||
311 | static void __init ksm_slab_free(void) | |
312 | { | |
313 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 314 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
315 | kmem_cache_destroy(rmap_item_cache); |
316 | mm_slot_cache = NULL; | |
317 | } | |
318 | ||
2c653d0e AA |
319 | static __always_inline bool is_stable_node_chain(struct stable_node *chain) |
320 | { | |
321 | return chain->rmap_hlist_len == STABLE_NODE_CHAIN; | |
322 | } | |
323 | ||
324 | static __always_inline bool is_stable_node_dup(struct stable_node *dup) | |
325 | { | |
326 | return dup->head == STABLE_NODE_DUP_HEAD; | |
327 | } | |
328 | ||
329 | static inline void stable_node_chain_add_dup(struct stable_node *dup, | |
330 | struct stable_node *chain) | |
331 | { | |
332 | VM_BUG_ON(is_stable_node_dup(dup)); | |
333 | dup->head = STABLE_NODE_DUP_HEAD; | |
334 | VM_BUG_ON(!is_stable_node_chain(chain)); | |
335 | hlist_add_head(&dup->hlist_dup, &chain->hlist); | |
336 | ksm_stable_node_dups++; | |
337 | } | |
338 | ||
339 | static inline void __stable_node_dup_del(struct stable_node *dup) | |
340 | { | |
b4fecc67 | 341 | VM_BUG_ON(!is_stable_node_dup(dup)); |
2c653d0e AA |
342 | hlist_del(&dup->hlist_dup); |
343 | ksm_stable_node_dups--; | |
344 | } | |
345 | ||
346 | static inline void stable_node_dup_del(struct stable_node *dup) | |
347 | { | |
348 | VM_BUG_ON(is_stable_node_chain(dup)); | |
349 | if (is_stable_node_dup(dup)) | |
350 | __stable_node_dup_del(dup); | |
351 | else | |
352 | rb_erase(&dup->node, root_stable_tree + NUMA(dup->nid)); | |
353 | #ifdef CONFIG_DEBUG_VM | |
354 | dup->head = NULL; | |
355 | #endif | |
356 | } | |
357 | ||
31dbd01f IE |
358 | static inline struct rmap_item *alloc_rmap_item(void) |
359 | { | |
473b0ce4 HD |
360 | struct rmap_item *rmap_item; |
361 | ||
5b398e41 | 362 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | |
363 | __GFP_NORETRY | __GFP_NOWARN); | |
473b0ce4 HD |
364 | if (rmap_item) |
365 | ksm_rmap_items++; | |
366 | return rmap_item; | |
31dbd01f IE |
367 | } |
368 | ||
369 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
370 | { | |
473b0ce4 | 371 | ksm_rmap_items--; |
31dbd01f IE |
372 | rmap_item->mm = NULL; /* debug safety */ |
373 | kmem_cache_free(rmap_item_cache, rmap_item); | |
374 | } | |
375 | ||
7b6ba2c7 HD |
376 | static inline struct stable_node *alloc_stable_node(void) |
377 | { | |
6213055f | 378 | /* |
379 | * The allocation can take too long with GFP_KERNEL when memory is under | |
380 | * pressure, which may lead to hung task warnings. Adding __GFP_HIGH | |
381 | * grants access to memory reserves, helping to avoid this problem. | |
382 | */ | |
383 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL | __GFP_HIGH); | |
7b6ba2c7 HD |
384 | } |
385 | ||
386 | static inline void free_stable_node(struct stable_node *stable_node) | |
387 | { | |
2c653d0e AA |
388 | VM_BUG_ON(stable_node->rmap_hlist_len && |
389 | !is_stable_node_chain(stable_node)); | |
7b6ba2c7 HD |
390 | kmem_cache_free(stable_node_cache, stable_node); |
391 | } | |
392 | ||
31dbd01f IE |
393 | static inline struct mm_slot *alloc_mm_slot(void) |
394 | { | |
395 | if (!mm_slot_cache) /* initialization failed */ | |
396 | return NULL; | |
397 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
398 | } | |
399 | ||
400 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
401 | { | |
402 | kmem_cache_free(mm_slot_cache, mm_slot); | |
403 | } | |
404 | ||
31dbd01f IE |
405 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
406 | { | |
4ca3a69b SL |
407 | struct mm_slot *slot; |
408 | ||
b67bfe0d | 409 | hash_for_each_possible(mm_slots_hash, slot, link, (unsigned long)mm) |
4ca3a69b SL |
410 | if (slot->mm == mm) |
411 | return slot; | |
31dbd01f | 412 | |
31dbd01f IE |
413 | return NULL; |
414 | } | |
415 | ||
416 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
417 | struct mm_slot *mm_slot) | |
418 | { | |
31dbd01f | 419 | mm_slot->mm = mm; |
4ca3a69b | 420 | hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm); |
31dbd01f IE |
421 | } |
422 | ||
a913e182 HD |
423 | /* |
424 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
425 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
426 | * takes mmap_sem briefly to serialize against them. ksm_exit() does not set | |
427 | * a special flag: they can just back out as soon as mm_users goes to zero. | |
428 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
429 | * places for correctness, in some places just to avoid unnecessary work. | |
430 | */ | |
431 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
432 | { | |
433 | return atomic_read(&mm->mm_users) == 0; | |
434 | } | |
435 | ||
31dbd01f IE |
436 | /* |
437 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
438 | * | |
d4edcf0d | 439 | * if (get_user_pages(addr, 1, 1, 1, &page, NULL) == 1) |
31dbd01f IE |
440 | * put_page(page); |
441 | * | |
442 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
443 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
444 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
445 | * mmap of /dev/mem or /dev/kmem, where we would not want to touch it. | |
1b2ee126 DH |
446 | * |
447 | * FAULT_FLAG/FOLL_REMOTE are because we do this outside the context | |
448 | * of the process that owns 'vma'. We also do not want to enforce | |
449 | * protection keys here anyway. | |
31dbd01f | 450 | */ |
d952b791 | 451 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
452 | { |
453 | struct page *page; | |
d952b791 | 454 | int ret = 0; |
31dbd01f IE |
455 | |
456 | do { | |
457 | cond_resched(); | |
1b2ee126 DH |
458 | page = follow_page(vma, addr, |
459 | FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); | |
22eccdd7 | 460 | if (IS_ERR_OR_NULL(page)) |
31dbd01f IE |
461 | break; |
462 | if (PageKsm(page)) | |
dcddffd4 KS |
463 | ret = handle_mm_fault(vma, addr, |
464 | FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE); | |
31dbd01f IE |
465 | else |
466 | ret = VM_FAULT_WRITE; | |
467 | put_page(page); | |
33692f27 | 468 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM))); |
d952b791 HD |
469 | /* |
470 | * We must loop because handle_mm_fault() may back out if there's | |
471 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
472 | * | |
473 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
474 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
475 | * but note that a concurrent fault might break PageKsm for us. | |
476 | * | |
477 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
478 | * backing file, which also invalidates anonymous pages: that's | |
479 | * okay, that truncation will have unmapped the PageKsm for us. | |
480 | * | |
481 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
482 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
483 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
484 | * to user; and ksmd, having no mm, would never be chosen for that. | |
485 | * | |
486 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
487 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
488 | * even ksmd can fail in this way - though it's usually breaking ksm | |
489 | * just to undo a merge it made a moment before, so unlikely to oom. | |
490 | * | |
491 | * That's a pity: we might therefore have more kernel pages allocated | |
492 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
493 | * will retry to break_cow on each pass, so should recover the page | |
494 | * in due course. The important thing is to not let VM_MERGEABLE | |
495 | * be cleared while any such pages might remain in the area. | |
496 | */ | |
497 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
498 | } |
499 | ||
ef694222 BL |
500 | static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, |
501 | unsigned long addr) | |
502 | { | |
503 | struct vm_area_struct *vma; | |
504 | if (ksm_test_exit(mm)) | |
505 | return NULL; | |
506 | vma = find_vma(mm, addr); | |
507 | if (!vma || vma->vm_start > addr) | |
508 | return NULL; | |
509 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
510 | return NULL; | |
511 | return vma; | |
512 | } | |
513 | ||
8dd3557a | 514 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 515 | { |
8dd3557a HD |
516 | struct mm_struct *mm = rmap_item->mm; |
517 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
518 | struct vm_area_struct *vma; |
519 | ||
4035c07a HD |
520 | /* |
521 | * It is not an accident that whenever we want to break COW | |
522 | * to undo, we also need to drop a reference to the anon_vma. | |
523 | */ | |
9e60109f | 524 | put_anon_vma(rmap_item->anon_vma); |
4035c07a | 525 | |
81464e30 | 526 | down_read(&mm->mmap_sem); |
ef694222 BL |
527 | vma = find_mergeable_vma(mm, addr); |
528 | if (vma) | |
529 | break_ksm(vma, addr); | |
31dbd01f IE |
530 | up_read(&mm->mmap_sem); |
531 | } | |
532 | ||
533 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
534 | { | |
535 | struct mm_struct *mm = rmap_item->mm; | |
536 | unsigned long addr = rmap_item->address; | |
537 | struct vm_area_struct *vma; | |
538 | struct page *page; | |
539 | ||
540 | down_read(&mm->mmap_sem); | |
ef694222 BL |
541 | vma = find_mergeable_vma(mm, addr); |
542 | if (!vma) | |
31dbd01f IE |
543 | goto out; |
544 | ||
545 | page = follow_page(vma, addr, FOLL_GET); | |
22eccdd7 | 546 | if (IS_ERR_OR_NULL(page)) |
31dbd01f | 547 | goto out; |
f765f540 | 548 | if (PageAnon(page)) { |
31dbd01f IE |
549 | flush_anon_page(vma, page, addr); |
550 | flush_dcache_page(page); | |
551 | } else { | |
552 | put_page(page); | |
c8f95ed1 AA |
553 | out: |
554 | page = NULL; | |
31dbd01f IE |
555 | } |
556 | up_read(&mm->mmap_sem); | |
557 | return page; | |
558 | } | |
559 | ||
90bd6fd3 PH |
560 | /* |
561 | * This helper is used for getting right index into array of tree roots. | |
562 | * When merge_across_nodes knob is set to 1, there are only two rb-trees for | |
563 | * stable and unstable pages from all nodes with roots in index 0. Otherwise, | |
564 | * every node has its own stable and unstable tree. | |
565 | */ | |
566 | static inline int get_kpfn_nid(unsigned long kpfn) | |
567 | { | |
d8fc16a8 | 568 | return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn)); |
90bd6fd3 PH |
569 | } |
570 | ||
2c653d0e AA |
571 | static struct stable_node *alloc_stable_node_chain(struct stable_node *dup, |
572 | struct rb_root *root) | |
573 | { | |
574 | struct stable_node *chain = alloc_stable_node(); | |
575 | VM_BUG_ON(is_stable_node_chain(dup)); | |
576 | if (likely(chain)) { | |
577 | INIT_HLIST_HEAD(&chain->hlist); | |
578 | chain->chain_prune_time = jiffies; | |
579 | chain->rmap_hlist_len = STABLE_NODE_CHAIN; | |
580 | #if defined (CONFIG_DEBUG_VM) && defined(CONFIG_NUMA) | |
581 | chain->nid = -1; /* debug */ | |
582 | #endif | |
583 | ksm_stable_node_chains++; | |
584 | ||
585 | /* | |
586 | * Put the stable node chain in the first dimension of | |
587 | * the stable tree and at the same time remove the old | |
588 | * stable node. | |
589 | */ | |
590 | rb_replace_node(&dup->node, &chain->node, root); | |
591 | ||
592 | /* | |
593 | * Move the old stable node to the second dimension | |
594 | * queued in the hlist_dup. The invariant is that all | |
595 | * dup stable_nodes in the chain->hlist point to pages | |
596 | * that are wrprotected and have the exact same | |
597 | * content. | |
598 | */ | |
599 | stable_node_chain_add_dup(dup, chain); | |
600 | } | |
601 | return chain; | |
602 | } | |
603 | ||
604 | static inline void free_stable_node_chain(struct stable_node *chain, | |
605 | struct rb_root *root) | |
606 | { | |
607 | rb_erase(&chain->node, root); | |
608 | free_stable_node(chain); | |
609 | ksm_stable_node_chains--; | |
610 | } | |
611 | ||
4035c07a HD |
612 | static void remove_node_from_stable_tree(struct stable_node *stable_node) |
613 | { | |
614 | struct rmap_item *rmap_item; | |
4035c07a | 615 | |
2c653d0e AA |
616 | /* check it's not STABLE_NODE_CHAIN or negative */ |
617 | BUG_ON(stable_node->rmap_hlist_len < 0); | |
618 | ||
b67bfe0d | 619 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
4035c07a HD |
620 | if (rmap_item->hlist.next) |
621 | ksm_pages_sharing--; | |
622 | else | |
623 | ksm_pages_shared--; | |
2c653d0e AA |
624 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
625 | stable_node->rmap_hlist_len--; | |
9e60109f | 626 | put_anon_vma(rmap_item->anon_vma); |
4035c07a HD |
627 | rmap_item->address &= PAGE_MASK; |
628 | cond_resched(); | |
629 | } | |
630 | ||
2c653d0e AA |
631 | /* |
632 | * We need the second aligned pointer of the migrate_nodes | |
633 | * list_head to stay clear from the rb_parent_color union | |
634 | * (aligned and different than any node) and also different | |
635 | * from &migrate_nodes. This will verify that future list.h changes | |
636 | * don't break STABLE_NODE_DUP_HEAD. | |
637 | */ | |
638 | #if GCC_VERSION >= 40903 /* only recent gcc can handle it */ | |
639 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD <= &migrate_nodes); | |
640 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1); | |
641 | #endif | |
642 | ||
4146d2d6 HD |
643 | if (stable_node->head == &migrate_nodes) |
644 | list_del(&stable_node->list); | |
645 | else | |
2c653d0e | 646 | stable_node_dup_del(stable_node); |
4035c07a HD |
647 | free_stable_node(stable_node); |
648 | } | |
649 | ||
650 | /* | |
651 | * get_ksm_page: checks if the page indicated by the stable node | |
652 | * is still its ksm page, despite having held no reference to it. | |
653 | * In which case we can trust the content of the page, and it | |
654 | * returns the gotten page; but if the page has now been zapped, | |
655 | * remove the stale node from the stable tree and return NULL. | |
c8d6553b | 656 | * But beware, the stable node's page might be being migrated. |
4035c07a HD |
657 | * |
658 | * You would expect the stable_node to hold a reference to the ksm page. | |
659 | * But if it increments the page's count, swapping out has to wait for | |
660 | * ksmd to come around again before it can free the page, which may take | |
661 | * seconds or even minutes: much too unresponsive. So instead we use a | |
662 | * "keyhole reference": access to the ksm page from the stable node peeps | |
663 | * out through its keyhole to see if that page still holds the right key, | |
664 | * pointing back to this stable node. This relies on freeing a PageAnon | |
665 | * page to reset its page->mapping to NULL, and relies on no other use of | |
666 | * a page to put something that might look like our key in page->mapping. | |
4035c07a HD |
667 | * is on its way to being freed; but it is an anomaly to bear in mind. |
668 | */ | |
8fdb3dbf | 669 | static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it) |
4035c07a HD |
670 | { |
671 | struct page *page; | |
672 | void *expected_mapping; | |
c8d6553b | 673 | unsigned long kpfn; |
4035c07a | 674 | |
bda807d4 MK |
675 | expected_mapping = (void *)((unsigned long)stable_node | |
676 | PAGE_MAPPING_KSM); | |
c8d6553b | 677 | again: |
4db0c3c2 | 678 | kpfn = READ_ONCE(stable_node->kpfn); |
c8d6553b HD |
679 | page = pfn_to_page(kpfn); |
680 | ||
681 | /* | |
682 | * page is computed from kpfn, so on most architectures reading | |
683 | * page->mapping is naturally ordered after reading node->kpfn, | |
684 | * but on Alpha we need to be more careful. | |
685 | */ | |
686 | smp_read_barrier_depends(); | |
4db0c3c2 | 687 | if (READ_ONCE(page->mapping) != expected_mapping) |
4035c07a | 688 | goto stale; |
c8d6553b HD |
689 | |
690 | /* | |
691 | * We cannot do anything with the page while its refcount is 0. | |
692 | * Usually 0 means free, or tail of a higher-order page: in which | |
693 | * case this node is no longer referenced, and should be freed; | |
694 | * however, it might mean that the page is under page_freeze_refs(). | |
695 | * The __remove_mapping() case is easy, again the node is now stale; | |
696 | * but if page is swapcache in migrate_page_move_mapping(), it might | |
697 | * still be our page, in which case it's essential to keep the node. | |
698 | */ | |
699 | while (!get_page_unless_zero(page)) { | |
700 | /* | |
701 | * Another check for page->mapping != expected_mapping would | |
702 | * work here too. We have chosen the !PageSwapCache test to | |
703 | * optimize the common case, when the page is or is about to | |
704 | * be freed: PageSwapCache is cleared (under spin_lock_irq) | |
705 | * in the freeze_refs section of __remove_mapping(); but Anon | |
706 | * page->mapping reset to NULL later, in free_pages_prepare(). | |
707 | */ | |
708 | if (!PageSwapCache(page)) | |
709 | goto stale; | |
710 | cpu_relax(); | |
711 | } | |
712 | ||
4db0c3c2 | 713 | if (READ_ONCE(page->mapping) != expected_mapping) { |
4035c07a HD |
714 | put_page(page); |
715 | goto stale; | |
716 | } | |
c8d6553b | 717 | |
8fdb3dbf | 718 | if (lock_it) { |
8aafa6a4 | 719 | lock_page(page); |
4db0c3c2 | 720 | if (READ_ONCE(page->mapping) != expected_mapping) { |
8aafa6a4 HD |
721 | unlock_page(page); |
722 | put_page(page); | |
723 | goto stale; | |
724 | } | |
725 | } | |
4035c07a | 726 | return page; |
c8d6553b | 727 | |
4035c07a | 728 | stale: |
c8d6553b HD |
729 | /* |
730 | * We come here from above when page->mapping or !PageSwapCache | |
731 | * suggests that the node is stale; but it might be under migration. | |
732 | * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(), | |
733 | * before checking whether node->kpfn has been changed. | |
734 | */ | |
735 | smp_rmb(); | |
4db0c3c2 | 736 | if (READ_ONCE(stable_node->kpfn) != kpfn) |
c8d6553b | 737 | goto again; |
4035c07a HD |
738 | remove_node_from_stable_tree(stable_node); |
739 | return NULL; | |
740 | } | |
741 | ||
31dbd01f IE |
742 | /* |
743 | * Removing rmap_item from stable or unstable tree. | |
744 | * This function will clean the information from the stable/unstable tree. | |
745 | */ | |
746 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
747 | { | |
7b6ba2c7 HD |
748 | if (rmap_item->address & STABLE_FLAG) { |
749 | struct stable_node *stable_node; | |
5ad64688 | 750 | struct page *page; |
31dbd01f | 751 | |
7b6ba2c7 | 752 | stable_node = rmap_item->head; |
8aafa6a4 | 753 | page = get_ksm_page(stable_node, true); |
4035c07a HD |
754 | if (!page) |
755 | goto out; | |
5ad64688 | 756 | |
7b6ba2c7 | 757 | hlist_del(&rmap_item->hlist); |
4035c07a HD |
758 | unlock_page(page); |
759 | put_page(page); | |
08beca44 | 760 | |
98666f8a | 761 | if (!hlist_empty(&stable_node->hlist)) |
4035c07a HD |
762 | ksm_pages_sharing--; |
763 | else | |
7b6ba2c7 | 764 | ksm_pages_shared--; |
2c653d0e AA |
765 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
766 | stable_node->rmap_hlist_len--; | |
31dbd01f | 767 | |
9e60109f | 768 | put_anon_vma(rmap_item->anon_vma); |
93d17715 | 769 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 770 | |
7b6ba2c7 | 771 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
772 | unsigned char age; |
773 | /* | |
9ba69294 | 774 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 775 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
776 | * But be careful when an mm is exiting: do the rb_erase |
777 | * if this rmap_item was inserted by this scan, rather | |
778 | * than left over from before. | |
31dbd01f IE |
779 | */ |
780 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 781 | BUG_ON(age > 1); |
31dbd01f | 782 | if (!age) |
90bd6fd3 | 783 | rb_erase(&rmap_item->node, |
ef53d16c | 784 | root_unstable_tree + NUMA(rmap_item->nid)); |
473b0ce4 | 785 | ksm_pages_unshared--; |
93d17715 | 786 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 787 | } |
4035c07a | 788 | out: |
31dbd01f IE |
789 | cond_resched(); /* we're called from many long loops */ |
790 | } | |
791 | ||
31dbd01f | 792 | static void remove_trailing_rmap_items(struct mm_slot *mm_slot, |
6514d511 | 793 | struct rmap_item **rmap_list) |
31dbd01f | 794 | { |
6514d511 HD |
795 | while (*rmap_list) { |
796 | struct rmap_item *rmap_item = *rmap_list; | |
797 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 798 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
799 | free_rmap_item(rmap_item); |
800 | } | |
801 | } | |
802 | ||
803 | /* | |
e850dcf5 | 804 | * Though it's very tempting to unmerge rmap_items from stable tree rather |
31dbd01f IE |
805 | * than check every pte of a given vma, the locking doesn't quite work for |
806 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
807 | * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing | |
808 | * rmap_items from parent to child at fork time (so as not to waste time | |
809 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
810 | * |
811 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
812 | * and freeing memory) when unmerging an area, it's easier to leave that | |
813 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
814 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 815 | */ |
d952b791 HD |
816 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
817 | unsigned long start, unsigned long end) | |
31dbd01f IE |
818 | { |
819 | unsigned long addr; | |
d952b791 | 820 | int err = 0; |
31dbd01f | 821 | |
d952b791 | 822 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
823 | if (ksm_test_exit(vma->vm_mm)) |
824 | break; | |
d952b791 HD |
825 | if (signal_pending(current)) |
826 | err = -ERESTARTSYS; | |
827 | else | |
828 | err = break_ksm(vma, addr); | |
829 | } | |
830 | return err; | |
31dbd01f IE |
831 | } |
832 | ||
2ffd8679 HD |
833 | #ifdef CONFIG_SYSFS |
834 | /* | |
835 | * Only called through the sysfs control interface: | |
836 | */ | |
cbf86cfe HD |
837 | static int remove_stable_node(struct stable_node *stable_node) |
838 | { | |
839 | struct page *page; | |
840 | int err; | |
841 | ||
842 | page = get_ksm_page(stable_node, true); | |
843 | if (!page) { | |
844 | /* | |
845 | * get_ksm_page did remove_node_from_stable_tree itself. | |
846 | */ | |
847 | return 0; | |
848 | } | |
849 | ||
8fdb3dbf HD |
850 | if (WARN_ON_ONCE(page_mapped(page))) { |
851 | /* | |
852 | * This should not happen: but if it does, just refuse to let | |
853 | * merge_across_nodes be switched - there is no need to panic. | |
854 | */ | |
cbf86cfe | 855 | err = -EBUSY; |
8fdb3dbf | 856 | } else { |
cbf86cfe | 857 | /* |
8fdb3dbf HD |
858 | * The stable node did not yet appear stale to get_ksm_page(), |
859 | * since that allows for an unmapped ksm page to be recognized | |
860 | * right up until it is freed; but the node is safe to remove. | |
cbf86cfe HD |
861 | * This page might be in a pagevec waiting to be freed, |
862 | * or it might be PageSwapCache (perhaps under writeback), | |
863 | * or it might have been removed from swapcache a moment ago. | |
864 | */ | |
865 | set_page_stable_node(page, NULL); | |
866 | remove_node_from_stable_tree(stable_node); | |
867 | err = 0; | |
868 | } | |
869 | ||
870 | unlock_page(page); | |
871 | put_page(page); | |
872 | return err; | |
873 | } | |
874 | ||
2c653d0e AA |
875 | static int remove_stable_node_chain(struct stable_node *stable_node, |
876 | struct rb_root *root) | |
877 | { | |
878 | struct stable_node *dup; | |
879 | struct hlist_node *hlist_safe; | |
880 | ||
881 | if (!is_stable_node_chain(stable_node)) { | |
882 | VM_BUG_ON(is_stable_node_dup(stable_node)); | |
883 | if (remove_stable_node(stable_node)) | |
884 | return true; | |
885 | else | |
886 | return false; | |
887 | } | |
888 | ||
889 | hlist_for_each_entry_safe(dup, hlist_safe, | |
890 | &stable_node->hlist, hlist_dup) { | |
891 | VM_BUG_ON(!is_stable_node_dup(dup)); | |
892 | if (remove_stable_node(dup)) | |
893 | return true; | |
894 | } | |
895 | BUG_ON(!hlist_empty(&stable_node->hlist)); | |
896 | free_stable_node_chain(stable_node, root); | |
897 | return false; | |
898 | } | |
899 | ||
cbf86cfe HD |
900 | static int remove_all_stable_nodes(void) |
901 | { | |
03640418 | 902 | struct stable_node *stable_node, *next; |
cbf86cfe HD |
903 | int nid; |
904 | int err = 0; | |
905 | ||
ef53d16c | 906 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
cbf86cfe HD |
907 | while (root_stable_tree[nid].rb_node) { |
908 | stable_node = rb_entry(root_stable_tree[nid].rb_node, | |
909 | struct stable_node, node); | |
2c653d0e AA |
910 | if (remove_stable_node_chain(stable_node, |
911 | root_stable_tree + nid)) { | |
cbf86cfe HD |
912 | err = -EBUSY; |
913 | break; /* proceed to next nid */ | |
914 | } | |
915 | cond_resched(); | |
916 | } | |
917 | } | |
03640418 | 918 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
919 | if (remove_stable_node(stable_node)) |
920 | err = -EBUSY; | |
921 | cond_resched(); | |
922 | } | |
cbf86cfe HD |
923 | return err; |
924 | } | |
925 | ||
d952b791 | 926 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
927 | { |
928 | struct mm_slot *mm_slot; | |
929 | struct mm_struct *mm; | |
930 | struct vm_area_struct *vma; | |
d952b791 HD |
931 | int err = 0; |
932 | ||
933 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 934 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
935 | struct mm_slot, mm_list); |
936 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 937 | |
9ba69294 HD |
938 | for (mm_slot = ksm_scan.mm_slot; |
939 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f IE |
940 | mm = mm_slot->mm; |
941 | down_read(&mm->mmap_sem); | |
942 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
9ba69294 HD |
943 | if (ksm_test_exit(mm)) |
944 | break; | |
31dbd01f IE |
945 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
946 | continue; | |
d952b791 HD |
947 | err = unmerge_ksm_pages(vma, |
948 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
949 | if (err) |
950 | goto error; | |
31dbd01f | 951 | } |
9ba69294 | 952 | |
6514d511 | 953 | remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list); |
7496fea9 | 954 | up_read(&mm->mmap_sem); |
d952b791 HD |
955 | |
956 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 957 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 958 | struct mm_slot, mm_list); |
9ba69294 | 959 | if (ksm_test_exit(mm)) { |
4ca3a69b | 960 | hash_del(&mm_slot->link); |
9ba69294 HD |
961 | list_del(&mm_slot->mm_list); |
962 | spin_unlock(&ksm_mmlist_lock); | |
963 | ||
964 | free_mm_slot(mm_slot); | |
965 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 | 966 | mmdrop(mm); |
7496fea9 | 967 | } else |
9ba69294 | 968 | spin_unlock(&ksm_mmlist_lock); |
31dbd01f IE |
969 | } |
970 | ||
cbf86cfe HD |
971 | /* Clean up stable nodes, but don't worry if some are still busy */ |
972 | remove_all_stable_nodes(); | |
d952b791 | 973 | ksm_scan.seqnr = 0; |
9ba69294 HD |
974 | return 0; |
975 | ||
976 | error: | |
977 | up_read(&mm->mmap_sem); | |
31dbd01f | 978 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 979 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 980 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 981 | return err; |
31dbd01f | 982 | } |
2ffd8679 | 983 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 984 | |
31dbd01f IE |
985 | static u32 calc_checksum(struct page *page) |
986 | { | |
987 | u32 checksum; | |
9b04c5fe | 988 | void *addr = kmap_atomic(page); |
31dbd01f | 989 | checksum = jhash2(addr, PAGE_SIZE / 4, 17); |
9b04c5fe | 990 | kunmap_atomic(addr); |
31dbd01f IE |
991 | return checksum; |
992 | } | |
993 | ||
994 | static int memcmp_pages(struct page *page1, struct page *page2) | |
995 | { | |
996 | char *addr1, *addr2; | |
997 | int ret; | |
998 | ||
9b04c5fe CW |
999 | addr1 = kmap_atomic(page1); |
1000 | addr2 = kmap_atomic(page2); | |
31dbd01f | 1001 | ret = memcmp(addr1, addr2, PAGE_SIZE); |
9b04c5fe CW |
1002 | kunmap_atomic(addr2); |
1003 | kunmap_atomic(addr1); | |
31dbd01f IE |
1004 | return ret; |
1005 | } | |
1006 | ||
1007 | static inline int pages_identical(struct page *page1, struct page *page2) | |
1008 | { | |
1009 | return !memcmp_pages(page1, page2); | |
1010 | } | |
1011 | ||
1012 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, | |
1013 | pte_t *orig_pte) | |
1014 | { | |
1015 | struct mm_struct *mm = vma->vm_mm; | |
36eaff33 KS |
1016 | struct page_vma_mapped_walk pvmw = { |
1017 | .page = page, | |
1018 | .vma = vma, | |
1019 | }; | |
31dbd01f IE |
1020 | int swapped; |
1021 | int err = -EFAULT; | |
6bdb913f HE |
1022 | unsigned long mmun_start; /* For mmu_notifiers */ |
1023 | unsigned long mmun_end; /* For mmu_notifiers */ | |
31dbd01f | 1024 | |
36eaff33 KS |
1025 | pvmw.address = page_address_in_vma(page, vma); |
1026 | if (pvmw.address == -EFAULT) | |
31dbd01f IE |
1027 | goto out; |
1028 | ||
29ad768c | 1029 | BUG_ON(PageTransCompound(page)); |
6bdb913f | 1030 | |
36eaff33 KS |
1031 | mmun_start = pvmw.address; |
1032 | mmun_end = pvmw.address + PAGE_SIZE; | |
6bdb913f HE |
1033 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); |
1034 | ||
36eaff33 | 1035 | if (!page_vma_mapped_walk(&pvmw)) |
6bdb913f | 1036 | goto out_mn; |
36eaff33 KS |
1037 | if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?")) |
1038 | goto out_unlock; | |
31dbd01f | 1039 | |
595cd8f2 AK |
1040 | if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) || |
1041 | (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte))) { | |
31dbd01f IE |
1042 | pte_t entry; |
1043 | ||
1044 | swapped = PageSwapCache(page); | |
36eaff33 | 1045 | flush_cache_page(vma, pvmw.address, page_to_pfn(page)); |
31dbd01f | 1046 | /* |
25985edc | 1047 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
31dbd01f IE |
1048 | * take any lock, therefore the check that we are going to make |
1049 | * with the pagecount against the mapcount is racey and | |
1050 | * O_DIRECT can happen right after the check. | |
1051 | * So we clear the pte and flush the tlb before the check | |
1052 | * this assure us that no O_DIRECT can happen after the check | |
1053 | * or in the middle of the check. | |
1054 | */ | |
36eaff33 | 1055 | entry = ptep_clear_flush_notify(vma, pvmw.address, pvmw.pte); |
31dbd01f IE |
1056 | /* |
1057 | * Check that no O_DIRECT or similar I/O is in progress on the | |
1058 | * page | |
1059 | */ | |
31e855ea | 1060 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
36eaff33 | 1061 | set_pte_at(mm, pvmw.address, pvmw.pte, entry); |
31dbd01f IE |
1062 | goto out_unlock; |
1063 | } | |
4e31635c HD |
1064 | if (pte_dirty(entry)) |
1065 | set_page_dirty(page); | |
595cd8f2 AK |
1066 | |
1067 | if (pte_protnone(entry)) | |
1068 | entry = pte_mkclean(pte_clear_savedwrite(entry)); | |
1069 | else | |
1070 | entry = pte_mkclean(pte_wrprotect(entry)); | |
36eaff33 | 1071 | set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry); |
31dbd01f | 1072 | } |
36eaff33 | 1073 | *orig_pte = *pvmw.pte; |
31dbd01f IE |
1074 | err = 0; |
1075 | ||
1076 | out_unlock: | |
36eaff33 | 1077 | page_vma_mapped_walk_done(&pvmw); |
6bdb913f HE |
1078 | out_mn: |
1079 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
31dbd01f IE |
1080 | out: |
1081 | return err; | |
1082 | } | |
1083 | ||
1084 | /** | |
1085 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
1086 | * @vma: vma that holds the pte pointing to page |
1087 | * @page: the page we are replacing by kpage | |
1088 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
1089 | * @orig_pte: the original value of the pte |
1090 | * | |
1091 | * Returns 0 on success, -EFAULT on failure. | |
1092 | */ | |
8dd3557a HD |
1093 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
1094 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
1095 | { |
1096 | struct mm_struct *mm = vma->vm_mm; | |
31dbd01f IE |
1097 | pmd_t *pmd; |
1098 | pte_t *ptep; | |
e86c59b1 | 1099 | pte_t newpte; |
31dbd01f IE |
1100 | spinlock_t *ptl; |
1101 | unsigned long addr; | |
31dbd01f | 1102 | int err = -EFAULT; |
6bdb913f HE |
1103 | unsigned long mmun_start; /* For mmu_notifiers */ |
1104 | unsigned long mmun_end; /* For mmu_notifiers */ | |
31dbd01f | 1105 | |
8dd3557a | 1106 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
1107 | if (addr == -EFAULT) |
1108 | goto out; | |
1109 | ||
6219049a BL |
1110 | pmd = mm_find_pmd(mm, addr); |
1111 | if (!pmd) | |
31dbd01f | 1112 | goto out; |
31dbd01f | 1113 | |
6bdb913f HE |
1114 | mmun_start = addr; |
1115 | mmun_end = addr + PAGE_SIZE; | |
1116 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
1117 | ||
31dbd01f IE |
1118 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
1119 | if (!pte_same(*ptep, orig_pte)) { | |
1120 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f | 1121 | goto out_mn; |
31dbd01f IE |
1122 | } |
1123 | ||
e86c59b1 CI |
1124 | /* |
1125 | * No need to check ksm_use_zero_pages here: we can only have a | |
1126 | * zero_page here if ksm_use_zero_pages was enabled alreaady. | |
1127 | */ | |
1128 | if (!is_zero_pfn(page_to_pfn(kpage))) { | |
1129 | get_page(kpage); | |
1130 | page_add_anon_rmap(kpage, vma, addr, false); | |
1131 | newpte = mk_pte(kpage, vma->vm_page_prot); | |
1132 | } else { | |
1133 | newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), | |
1134 | vma->vm_page_prot)); | |
1135 | } | |
31dbd01f IE |
1136 | |
1137 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
34ee645e | 1138 | ptep_clear_flush_notify(vma, addr, ptep); |
e86c59b1 | 1139 | set_pte_at_notify(mm, addr, ptep, newpte); |
31dbd01f | 1140 | |
d281ee61 | 1141 | page_remove_rmap(page, false); |
ae52a2ad HD |
1142 | if (!page_mapped(page)) |
1143 | try_to_free_swap(page); | |
8dd3557a | 1144 | put_page(page); |
31dbd01f IE |
1145 | |
1146 | pte_unmap_unlock(ptep, ptl); | |
1147 | err = 0; | |
6bdb913f HE |
1148 | out_mn: |
1149 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
31dbd01f IE |
1150 | out: |
1151 | return err; | |
1152 | } | |
1153 | ||
1154 | /* | |
1155 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
1156 | * @vma: the vma that holds the pte pointing to page |
1157 | * @page: the PageAnon page that we want to replace with kpage | |
80e14822 HD |
1158 | * @kpage: the PageKsm page that we want to map instead of page, |
1159 | * or NULL the first time when we want to use page as kpage. | |
31dbd01f IE |
1160 | * |
1161 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
1162 | */ | |
1163 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 1164 | struct page *page, struct page *kpage) |
31dbd01f IE |
1165 | { |
1166 | pte_t orig_pte = __pte(0); | |
1167 | int err = -EFAULT; | |
1168 | ||
db114b83 HD |
1169 | if (page == kpage) /* ksm page forked */ |
1170 | return 0; | |
1171 | ||
8dd3557a | 1172 | if (!PageAnon(page)) |
31dbd01f IE |
1173 | goto out; |
1174 | ||
31dbd01f IE |
1175 | /* |
1176 | * We need the page lock to read a stable PageSwapCache in | |
1177 | * write_protect_page(). We use trylock_page() instead of | |
1178 | * lock_page() because we don't want to wait here - we | |
1179 | * prefer to continue scanning and merging different pages, | |
1180 | * then come back to this page when it is unlocked. | |
1181 | */ | |
8dd3557a | 1182 | if (!trylock_page(page)) |
31e855ea | 1183 | goto out; |
f765f540 KS |
1184 | |
1185 | if (PageTransCompound(page)) { | |
a7306c34 | 1186 | if (split_huge_page(page)) |
f765f540 KS |
1187 | goto out_unlock; |
1188 | } | |
1189 | ||
31dbd01f IE |
1190 | /* |
1191 | * If this anonymous page is mapped only here, its pte may need | |
1192 | * to be write-protected. If it's mapped elsewhere, all of its | |
1193 | * ptes are necessarily already write-protected. But in either | |
1194 | * case, we need to lock and check page_count is not raised. | |
1195 | */ | |
80e14822 HD |
1196 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
1197 | if (!kpage) { | |
1198 | /* | |
1199 | * While we hold page lock, upgrade page from | |
1200 | * PageAnon+anon_vma to PageKsm+NULL stable_node: | |
1201 | * stable_tree_insert() will update stable_node. | |
1202 | */ | |
1203 | set_page_stable_node(page, NULL); | |
1204 | mark_page_accessed(page); | |
337ed7eb MK |
1205 | /* |
1206 | * Page reclaim just frees a clean page with no dirty | |
1207 | * ptes: make sure that the ksm page would be swapped. | |
1208 | */ | |
1209 | if (!PageDirty(page)) | |
1210 | SetPageDirty(page); | |
80e14822 HD |
1211 | err = 0; |
1212 | } else if (pages_identical(page, kpage)) | |
1213 | err = replace_page(vma, page, kpage, orig_pte); | |
1214 | } | |
31dbd01f | 1215 | |
80e14822 | 1216 | if ((vma->vm_flags & VM_LOCKED) && kpage && !err) { |
73848b46 | 1217 | munlock_vma_page(page); |
5ad64688 HD |
1218 | if (!PageMlocked(kpage)) { |
1219 | unlock_page(page); | |
5ad64688 HD |
1220 | lock_page(kpage); |
1221 | mlock_vma_page(kpage); | |
1222 | page = kpage; /* for final unlock */ | |
1223 | } | |
1224 | } | |
73848b46 | 1225 | |
f765f540 | 1226 | out_unlock: |
8dd3557a | 1227 | unlock_page(page); |
31dbd01f IE |
1228 | out: |
1229 | return err; | |
1230 | } | |
1231 | ||
81464e30 HD |
1232 | /* |
1233 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
1234 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
1235 | * |
1236 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 1237 | */ |
8dd3557a HD |
1238 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
1239 | struct page *page, struct page *kpage) | |
81464e30 | 1240 | { |
8dd3557a | 1241 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
1242 | struct vm_area_struct *vma; |
1243 | int err = -EFAULT; | |
1244 | ||
8dd3557a | 1245 | down_read(&mm->mmap_sem); |
85c6e8dd AA |
1246 | vma = find_mergeable_vma(mm, rmap_item->address); |
1247 | if (!vma) | |
81464e30 HD |
1248 | goto out; |
1249 | ||
8dd3557a | 1250 | err = try_to_merge_one_page(vma, page, kpage); |
db114b83 HD |
1251 | if (err) |
1252 | goto out; | |
1253 | ||
bc56620b HD |
1254 | /* Unstable nid is in union with stable anon_vma: remove first */ |
1255 | remove_rmap_item_from_tree(rmap_item); | |
1256 | ||
db114b83 | 1257 | /* Must get reference to anon_vma while still holding mmap_sem */ |
9e60109f PZ |
1258 | rmap_item->anon_vma = vma->anon_vma; |
1259 | get_anon_vma(vma->anon_vma); | |
81464e30 | 1260 | out: |
8dd3557a | 1261 | up_read(&mm->mmap_sem); |
81464e30 HD |
1262 | return err; |
1263 | } | |
1264 | ||
31dbd01f IE |
1265 | /* |
1266 | * try_to_merge_two_pages - take two identical pages and prepare them | |
1267 | * to be merged into one page. | |
1268 | * | |
8dd3557a HD |
1269 | * This function returns the kpage if we successfully merged two identical |
1270 | * pages into one ksm page, NULL otherwise. | |
31dbd01f | 1271 | * |
80e14822 | 1272 | * Note that this function upgrades page to ksm page: if one of the pages |
31dbd01f IE |
1273 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
1274 | */ | |
8dd3557a HD |
1275 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
1276 | struct page *page, | |
1277 | struct rmap_item *tree_rmap_item, | |
1278 | struct page *tree_page) | |
31dbd01f | 1279 | { |
80e14822 | 1280 | int err; |
31dbd01f | 1281 | |
80e14822 | 1282 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
31dbd01f | 1283 | if (!err) { |
8dd3557a | 1284 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
80e14822 | 1285 | tree_page, page); |
31dbd01f | 1286 | /* |
81464e30 HD |
1287 | * If that fails, we have a ksm page with only one pte |
1288 | * pointing to it: so break it. | |
31dbd01f | 1289 | */ |
4035c07a | 1290 | if (err) |
8dd3557a | 1291 | break_cow(rmap_item); |
31dbd01f | 1292 | } |
80e14822 | 1293 | return err ? NULL : page; |
31dbd01f IE |
1294 | } |
1295 | ||
2c653d0e AA |
1296 | static __always_inline |
1297 | bool __is_page_sharing_candidate(struct stable_node *stable_node, int offset) | |
1298 | { | |
1299 | VM_BUG_ON(stable_node->rmap_hlist_len < 0); | |
1300 | /* | |
1301 | * Check that at least one mapping still exists, otherwise | |
1302 | * there's no much point to merge and share with this | |
1303 | * stable_node, as the underlying tree_page of the other | |
1304 | * sharer is going to be freed soon. | |
1305 | */ | |
1306 | return stable_node->rmap_hlist_len && | |
1307 | stable_node->rmap_hlist_len + offset < ksm_max_page_sharing; | |
1308 | } | |
1309 | ||
1310 | static __always_inline | |
1311 | bool is_page_sharing_candidate(struct stable_node *stable_node) | |
1312 | { | |
1313 | return __is_page_sharing_candidate(stable_node, 0); | |
1314 | } | |
1315 | ||
8dc5ffcd AA |
1316 | struct page *stable_node_dup(struct stable_node **_stable_node_dup, |
1317 | struct stable_node **_stable_node, | |
1318 | struct rb_root *root, | |
1319 | bool prune_stale_stable_nodes) | |
2c653d0e | 1320 | { |
b4fecc67 | 1321 | struct stable_node *dup, *found = NULL, *stable_node = *_stable_node; |
2c653d0e | 1322 | struct hlist_node *hlist_safe; |
8dc5ffcd | 1323 | struct page *_tree_page, *tree_page = NULL; |
2c653d0e AA |
1324 | int nr = 0; |
1325 | int found_rmap_hlist_len; | |
1326 | ||
1327 | if (!prune_stale_stable_nodes || | |
1328 | time_before(jiffies, stable_node->chain_prune_time + | |
1329 | msecs_to_jiffies( | |
1330 | ksm_stable_node_chains_prune_millisecs))) | |
1331 | prune_stale_stable_nodes = false; | |
1332 | else | |
1333 | stable_node->chain_prune_time = jiffies; | |
1334 | ||
1335 | hlist_for_each_entry_safe(dup, hlist_safe, | |
1336 | &stable_node->hlist, hlist_dup) { | |
1337 | cond_resched(); | |
1338 | /* | |
1339 | * We must walk all stable_node_dup to prune the stale | |
1340 | * stable nodes during lookup. | |
1341 | * | |
1342 | * get_ksm_page can drop the nodes from the | |
1343 | * stable_node->hlist if they point to freed pages | |
1344 | * (that's why we do a _safe walk). The "dup" | |
1345 | * stable_node parameter itself will be freed from | |
1346 | * under us if it returns NULL. | |
1347 | */ | |
1348 | _tree_page = get_ksm_page(dup, false); | |
1349 | if (!_tree_page) | |
1350 | continue; | |
1351 | nr += 1; | |
1352 | if (is_page_sharing_candidate(dup)) { | |
1353 | if (!found || | |
1354 | dup->rmap_hlist_len > found_rmap_hlist_len) { | |
1355 | if (found) | |
8dc5ffcd | 1356 | put_page(tree_page); |
2c653d0e AA |
1357 | found = dup; |
1358 | found_rmap_hlist_len = found->rmap_hlist_len; | |
8dc5ffcd | 1359 | tree_page = _tree_page; |
2c653d0e | 1360 | |
8dc5ffcd | 1361 | /* skip put_page for found dup */ |
2c653d0e AA |
1362 | if (!prune_stale_stable_nodes) |
1363 | break; | |
2c653d0e AA |
1364 | continue; |
1365 | } | |
1366 | } | |
1367 | put_page(_tree_page); | |
1368 | } | |
1369 | ||
1370 | /* | |
1371 | * nr is relevant only if prune_stale_stable_nodes is true, | |
1372 | * otherwise we may break the loop at nr == 1 even if there | |
1373 | * are multiple entries. | |
1374 | */ | |
1375 | if (prune_stale_stable_nodes && found) { | |
1376 | if (nr == 1) { | |
1377 | /* | |
1378 | * If there's not just one entry it would | |
1379 | * corrupt memory, better BUG_ON. In KSM | |
1380 | * context with no lock held it's not even | |
1381 | * fatal. | |
1382 | */ | |
1383 | BUG_ON(stable_node->hlist.first->next); | |
1384 | ||
1385 | /* | |
1386 | * There's just one entry and it is below the | |
1387 | * deduplication limit so drop the chain. | |
1388 | */ | |
1389 | rb_replace_node(&stable_node->node, &found->node, | |
1390 | root); | |
1391 | free_stable_node(stable_node); | |
1392 | ksm_stable_node_chains--; | |
1393 | ksm_stable_node_dups--; | |
b4fecc67 | 1394 | /* |
0ba1d0f7 AA |
1395 | * NOTE: the caller depends on the stable_node |
1396 | * to be equal to stable_node_dup if the chain | |
1397 | * was collapsed. | |
b4fecc67 | 1398 | */ |
0ba1d0f7 AA |
1399 | *_stable_node = found; |
1400 | /* | |
1401 | * Just for robustneess as stable_node is | |
1402 | * otherwise left as a stable pointer, the | |
1403 | * compiler shall optimize it away at build | |
1404 | * time. | |
1405 | */ | |
1406 | stable_node = NULL; | |
2c653d0e AA |
1407 | } else if (__is_page_sharing_candidate(found, 1)) { |
1408 | /* | |
1409 | * Refile our candidate at the head | |
1410 | * after the prune if our candidate | |
1411 | * can accept one more future sharing | |
1412 | * in addition to the one underway. | |
1413 | */ | |
1414 | hlist_del(&found->hlist_dup); | |
1415 | hlist_add_head(&found->hlist_dup, | |
1416 | &stable_node->hlist); | |
1417 | } | |
1418 | } | |
1419 | ||
8dc5ffcd AA |
1420 | *_stable_node_dup = found; |
1421 | return tree_page; | |
2c653d0e AA |
1422 | } |
1423 | ||
1424 | static struct stable_node *stable_node_dup_any(struct stable_node *stable_node, | |
1425 | struct rb_root *root) | |
1426 | { | |
1427 | if (!is_stable_node_chain(stable_node)) | |
1428 | return stable_node; | |
1429 | if (hlist_empty(&stable_node->hlist)) { | |
1430 | free_stable_node_chain(stable_node, root); | |
1431 | return NULL; | |
1432 | } | |
1433 | return hlist_entry(stable_node->hlist.first, | |
1434 | typeof(*stable_node), hlist_dup); | |
1435 | } | |
1436 | ||
8dc5ffcd AA |
1437 | /* |
1438 | * Like for get_ksm_page, this function can free the *_stable_node and | |
1439 | * *_stable_node_dup if the returned tree_page is NULL. | |
1440 | * | |
1441 | * It can also free and overwrite *_stable_node with the found | |
1442 | * stable_node_dup if the chain is collapsed (in which case | |
1443 | * *_stable_node will be equal to *_stable_node_dup like if the chain | |
1444 | * never existed). It's up to the caller to verify tree_page is not | |
1445 | * NULL before dereferencing *_stable_node or *_stable_node_dup. | |
1446 | * | |
1447 | * *_stable_node_dup is really a second output parameter of this | |
1448 | * function and will be overwritten in all cases, the caller doesn't | |
1449 | * need to initialize it. | |
1450 | */ | |
1451 | static struct page *__stable_node_chain(struct stable_node **_stable_node_dup, | |
1452 | struct stable_node **_stable_node, | |
1453 | struct rb_root *root, | |
1454 | bool prune_stale_stable_nodes) | |
2c653d0e | 1455 | { |
b4fecc67 | 1456 | struct stable_node *stable_node = *_stable_node; |
2c653d0e AA |
1457 | if (!is_stable_node_chain(stable_node)) { |
1458 | if (is_page_sharing_candidate(stable_node)) { | |
8dc5ffcd AA |
1459 | *_stable_node_dup = stable_node; |
1460 | return get_ksm_page(stable_node, false); | |
2c653d0e | 1461 | } |
8dc5ffcd AA |
1462 | /* |
1463 | * _stable_node_dup set to NULL means the stable_node | |
1464 | * reached the ksm_max_page_sharing limit. | |
1465 | */ | |
1466 | *_stable_node_dup = NULL; | |
2c653d0e AA |
1467 | return NULL; |
1468 | } | |
8dc5ffcd | 1469 | return stable_node_dup(_stable_node_dup, _stable_node, root, |
2c653d0e AA |
1470 | prune_stale_stable_nodes); |
1471 | } | |
1472 | ||
8dc5ffcd AA |
1473 | static __always_inline struct page *chain_prune(struct stable_node **s_n_d, |
1474 | struct stable_node **s_n, | |
1475 | struct rb_root *root) | |
2c653d0e | 1476 | { |
8dc5ffcd | 1477 | return __stable_node_chain(s_n_d, s_n, root, true); |
2c653d0e AA |
1478 | } |
1479 | ||
8dc5ffcd AA |
1480 | static __always_inline struct page *chain(struct stable_node **s_n_d, |
1481 | struct stable_node *s_n, | |
1482 | struct rb_root *root) | |
2c653d0e | 1483 | { |
8dc5ffcd AA |
1484 | struct stable_node *old_stable_node = s_n; |
1485 | struct page *tree_page; | |
1486 | ||
1487 | tree_page = __stable_node_chain(s_n_d, &s_n, root, false); | |
1488 | /* not pruning dups so s_n cannot have changed */ | |
1489 | VM_BUG_ON(s_n != old_stable_node); | |
1490 | return tree_page; | |
2c653d0e AA |
1491 | } |
1492 | ||
31dbd01f | 1493 | /* |
8dd3557a | 1494 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
1495 | * |
1496 | * This function checks if there is a page inside the stable tree | |
1497 | * with identical content to the page that we are scanning right now. | |
1498 | * | |
7b6ba2c7 | 1499 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
1500 | * NULL otherwise. |
1501 | */ | |
62b61f61 | 1502 | static struct page *stable_tree_search(struct page *page) |
31dbd01f | 1503 | { |
90bd6fd3 | 1504 | int nid; |
ef53d16c | 1505 | struct rb_root *root; |
4146d2d6 HD |
1506 | struct rb_node **new; |
1507 | struct rb_node *parent; | |
2c653d0e | 1508 | struct stable_node *stable_node, *stable_node_dup, *stable_node_any; |
4146d2d6 | 1509 | struct stable_node *page_node; |
31dbd01f | 1510 | |
4146d2d6 HD |
1511 | page_node = page_stable_node(page); |
1512 | if (page_node && page_node->head != &migrate_nodes) { | |
1513 | /* ksm page forked */ | |
08beca44 | 1514 | get_page(page); |
62b61f61 | 1515 | return page; |
08beca44 HD |
1516 | } |
1517 | ||
90bd6fd3 | 1518 | nid = get_kpfn_nid(page_to_pfn(page)); |
ef53d16c | 1519 | root = root_stable_tree + nid; |
4146d2d6 | 1520 | again: |
ef53d16c | 1521 | new = &root->rb_node; |
4146d2d6 | 1522 | parent = NULL; |
90bd6fd3 | 1523 | |
4146d2d6 | 1524 | while (*new) { |
4035c07a | 1525 | struct page *tree_page; |
31dbd01f IE |
1526 | int ret; |
1527 | ||
08beca44 | 1528 | cond_resched(); |
4146d2d6 | 1529 | stable_node = rb_entry(*new, struct stable_node, node); |
2c653d0e | 1530 | stable_node_any = NULL; |
8dc5ffcd | 1531 | tree_page = chain_prune(&stable_node_dup, &stable_node, root); |
b4fecc67 AA |
1532 | /* |
1533 | * NOTE: stable_node may have been freed by | |
1534 | * chain_prune() if the returned stable_node_dup is | |
1535 | * not NULL. stable_node_dup may have been inserted in | |
1536 | * the rbtree instead as a regular stable_node (in | |
1537 | * order to collapse the stable_node chain if a single | |
0ba1d0f7 AA |
1538 | * stable_node dup was found in it). In such case the |
1539 | * stable_node is overwritten by the calleee to point | |
1540 | * to the stable_node_dup that was collapsed in the | |
1541 | * stable rbtree and stable_node will be equal to | |
1542 | * stable_node_dup like if the chain never existed. | |
b4fecc67 | 1543 | */ |
2c653d0e AA |
1544 | if (!stable_node_dup) { |
1545 | /* | |
1546 | * Either all stable_node dups were full in | |
1547 | * this stable_node chain, or this chain was | |
1548 | * empty and should be rb_erased. | |
1549 | */ | |
1550 | stable_node_any = stable_node_dup_any(stable_node, | |
1551 | root); | |
1552 | if (!stable_node_any) { | |
1553 | /* rb_erase just run */ | |
1554 | goto again; | |
1555 | } | |
1556 | /* | |
1557 | * Take any of the stable_node dups page of | |
1558 | * this stable_node chain to let the tree walk | |
1559 | * continue. All KSM pages belonging to the | |
1560 | * stable_node dups in a stable_node chain | |
1561 | * have the same content and they're | |
1562 | * wrprotected at all times. Any will work | |
1563 | * fine to continue the walk. | |
1564 | */ | |
1565 | tree_page = get_ksm_page(stable_node_any, false); | |
1566 | } | |
1567 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); | |
f2e5ff85 AA |
1568 | if (!tree_page) { |
1569 | /* | |
1570 | * If we walked over a stale stable_node, | |
1571 | * get_ksm_page() will call rb_erase() and it | |
1572 | * may rebalance the tree from under us. So | |
1573 | * restart the search from scratch. Returning | |
1574 | * NULL would be safe too, but we'd generate | |
1575 | * false negative insertions just because some | |
1576 | * stable_node was stale. | |
1577 | */ | |
1578 | goto again; | |
1579 | } | |
31dbd01f | 1580 | |
4035c07a | 1581 | ret = memcmp_pages(page, tree_page); |
c8d6553b | 1582 | put_page(tree_page); |
31dbd01f | 1583 | |
4146d2d6 | 1584 | parent = *new; |
c8d6553b | 1585 | if (ret < 0) |
4146d2d6 | 1586 | new = &parent->rb_left; |
c8d6553b | 1587 | else if (ret > 0) |
4146d2d6 | 1588 | new = &parent->rb_right; |
c8d6553b | 1589 | else { |
2c653d0e AA |
1590 | if (page_node) { |
1591 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1592 | /* | |
1593 | * Test if the migrated page should be merged | |
1594 | * into a stable node dup. If the mapcount is | |
1595 | * 1 we can migrate it with another KSM page | |
1596 | * without adding it to the chain. | |
1597 | */ | |
1598 | if (page_mapcount(page) > 1) | |
1599 | goto chain_append; | |
1600 | } | |
1601 | ||
1602 | if (!stable_node_dup) { | |
1603 | /* | |
1604 | * If the stable_node is a chain and | |
1605 | * we got a payload match in memcmp | |
1606 | * but we cannot merge the scanned | |
1607 | * page in any of the existing | |
1608 | * stable_node dups because they're | |
1609 | * all full, we need to wait the | |
1610 | * scanned page to find itself a match | |
1611 | * in the unstable tree to create a | |
1612 | * brand new KSM page to add later to | |
1613 | * the dups of this stable_node. | |
1614 | */ | |
1615 | return NULL; | |
1616 | } | |
1617 | ||
c8d6553b HD |
1618 | /* |
1619 | * Lock and unlock the stable_node's page (which | |
1620 | * might already have been migrated) so that page | |
1621 | * migration is sure to notice its raised count. | |
1622 | * It would be more elegant to return stable_node | |
1623 | * than kpage, but that involves more changes. | |
1624 | */ | |
2c653d0e AA |
1625 | tree_page = get_ksm_page(stable_node_dup, true); |
1626 | if (unlikely(!tree_page)) | |
1627 | /* | |
1628 | * The tree may have been rebalanced, | |
1629 | * so re-evaluate parent and new. | |
1630 | */ | |
4146d2d6 | 1631 | goto again; |
2c653d0e AA |
1632 | unlock_page(tree_page); |
1633 | ||
1634 | if (get_kpfn_nid(stable_node_dup->kpfn) != | |
1635 | NUMA(stable_node_dup->nid)) { | |
1636 | put_page(tree_page); | |
1637 | goto replace; | |
1638 | } | |
1639 | return tree_page; | |
c8d6553b | 1640 | } |
31dbd01f IE |
1641 | } |
1642 | ||
4146d2d6 HD |
1643 | if (!page_node) |
1644 | return NULL; | |
1645 | ||
1646 | list_del(&page_node->list); | |
1647 | DO_NUMA(page_node->nid = nid); | |
1648 | rb_link_node(&page_node->node, parent, new); | |
ef53d16c | 1649 | rb_insert_color(&page_node->node, root); |
2c653d0e AA |
1650 | out: |
1651 | if (is_page_sharing_candidate(page_node)) { | |
1652 | get_page(page); | |
1653 | return page; | |
1654 | } else | |
1655 | return NULL; | |
4146d2d6 HD |
1656 | |
1657 | replace: | |
b4fecc67 AA |
1658 | /* |
1659 | * If stable_node was a chain and chain_prune collapsed it, | |
0ba1d0f7 AA |
1660 | * stable_node has been updated to be the new regular |
1661 | * stable_node. A collapse of the chain is indistinguishable | |
1662 | * from the case there was no chain in the stable | |
1663 | * rbtree. Otherwise stable_node is the chain and | |
1664 | * stable_node_dup is the dup to replace. | |
b4fecc67 | 1665 | */ |
0ba1d0f7 | 1666 | if (stable_node_dup == stable_node) { |
b4fecc67 AA |
1667 | VM_BUG_ON(is_stable_node_chain(stable_node_dup)); |
1668 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); | |
2c653d0e AA |
1669 | /* there is no chain */ |
1670 | if (page_node) { | |
1671 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1672 | list_del(&page_node->list); | |
1673 | DO_NUMA(page_node->nid = nid); | |
b4fecc67 AA |
1674 | rb_replace_node(&stable_node_dup->node, |
1675 | &page_node->node, | |
2c653d0e AA |
1676 | root); |
1677 | if (is_page_sharing_candidate(page_node)) | |
1678 | get_page(page); | |
1679 | else | |
1680 | page = NULL; | |
1681 | } else { | |
b4fecc67 | 1682 | rb_erase(&stable_node_dup->node, root); |
2c653d0e AA |
1683 | page = NULL; |
1684 | } | |
4146d2d6 | 1685 | } else { |
2c653d0e AA |
1686 | VM_BUG_ON(!is_stable_node_chain(stable_node)); |
1687 | __stable_node_dup_del(stable_node_dup); | |
1688 | if (page_node) { | |
1689 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1690 | list_del(&page_node->list); | |
1691 | DO_NUMA(page_node->nid = nid); | |
1692 | stable_node_chain_add_dup(page_node, stable_node); | |
1693 | if (is_page_sharing_candidate(page_node)) | |
1694 | get_page(page); | |
1695 | else | |
1696 | page = NULL; | |
1697 | } else { | |
1698 | page = NULL; | |
1699 | } | |
4146d2d6 | 1700 | } |
2c653d0e AA |
1701 | stable_node_dup->head = &migrate_nodes; |
1702 | list_add(&stable_node_dup->list, stable_node_dup->head); | |
4146d2d6 | 1703 | return page; |
2c653d0e AA |
1704 | |
1705 | chain_append: | |
1706 | /* stable_node_dup could be null if it reached the limit */ | |
1707 | if (!stable_node_dup) | |
1708 | stable_node_dup = stable_node_any; | |
b4fecc67 AA |
1709 | /* |
1710 | * If stable_node was a chain and chain_prune collapsed it, | |
0ba1d0f7 AA |
1711 | * stable_node has been updated to be the new regular |
1712 | * stable_node. A collapse of the chain is indistinguishable | |
1713 | * from the case there was no chain in the stable | |
1714 | * rbtree. Otherwise stable_node is the chain and | |
1715 | * stable_node_dup is the dup to replace. | |
b4fecc67 | 1716 | */ |
0ba1d0f7 | 1717 | if (stable_node_dup == stable_node) { |
b4fecc67 AA |
1718 | VM_BUG_ON(is_stable_node_chain(stable_node_dup)); |
1719 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); | |
2c653d0e AA |
1720 | /* chain is missing so create it */ |
1721 | stable_node = alloc_stable_node_chain(stable_node_dup, | |
1722 | root); | |
1723 | if (!stable_node) | |
1724 | return NULL; | |
1725 | } | |
1726 | /* | |
1727 | * Add this stable_node dup that was | |
1728 | * migrated to the stable_node chain | |
1729 | * of the current nid for this page | |
1730 | * content. | |
1731 | */ | |
b4fecc67 AA |
1732 | VM_BUG_ON(!is_stable_node_chain(stable_node)); |
1733 | VM_BUG_ON(!is_stable_node_dup(stable_node_dup)); | |
2c653d0e AA |
1734 | VM_BUG_ON(page_node->head != &migrate_nodes); |
1735 | list_del(&page_node->list); | |
1736 | DO_NUMA(page_node->nid = nid); | |
1737 | stable_node_chain_add_dup(page_node, stable_node); | |
1738 | goto out; | |
31dbd01f IE |
1739 | } |
1740 | ||
1741 | /* | |
e850dcf5 | 1742 | * stable_tree_insert - insert stable tree node pointing to new ksm page |
31dbd01f IE |
1743 | * into the stable tree. |
1744 | * | |
7b6ba2c7 HD |
1745 | * This function returns the stable tree node just allocated on success, |
1746 | * NULL otherwise. | |
31dbd01f | 1747 | */ |
7b6ba2c7 | 1748 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f | 1749 | { |
90bd6fd3 PH |
1750 | int nid; |
1751 | unsigned long kpfn; | |
ef53d16c | 1752 | struct rb_root *root; |
90bd6fd3 | 1753 | struct rb_node **new; |
f2e5ff85 | 1754 | struct rb_node *parent; |
2c653d0e AA |
1755 | struct stable_node *stable_node, *stable_node_dup, *stable_node_any; |
1756 | bool need_chain = false; | |
31dbd01f | 1757 | |
90bd6fd3 PH |
1758 | kpfn = page_to_pfn(kpage); |
1759 | nid = get_kpfn_nid(kpfn); | |
ef53d16c | 1760 | root = root_stable_tree + nid; |
f2e5ff85 AA |
1761 | again: |
1762 | parent = NULL; | |
ef53d16c | 1763 | new = &root->rb_node; |
90bd6fd3 | 1764 | |
31dbd01f | 1765 | while (*new) { |
4035c07a | 1766 | struct page *tree_page; |
31dbd01f IE |
1767 | int ret; |
1768 | ||
08beca44 | 1769 | cond_resched(); |
7b6ba2c7 | 1770 | stable_node = rb_entry(*new, struct stable_node, node); |
2c653d0e | 1771 | stable_node_any = NULL; |
8dc5ffcd | 1772 | tree_page = chain(&stable_node_dup, stable_node, root); |
2c653d0e AA |
1773 | if (!stable_node_dup) { |
1774 | /* | |
1775 | * Either all stable_node dups were full in | |
1776 | * this stable_node chain, or this chain was | |
1777 | * empty and should be rb_erased. | |
1778 | */ | |
1779 | stable_node_any = stable_node_dup_any(stable_node, | |
1780 | root); | |
1781 | if (!stable_node_any) { | |
1782 | /* rb_erase just run */ | |
1783 | goto again; | |
1784 | } | |
1785 | /* | |
1786 | * Take any of the stable_node dups page of | |
1787 | * this stable_node chain to let the tree walk | |
1788 | * continue. All KSM pages belonging to the | |
1789 | * stable_node dups in a stable_node chain | |
1790 | * have the same content and they're | |
1791 | * wrprotected at all times. Any will work | |
1792 | * fine to continue the walk. | |
1793 | */ | |
1794 | tree_page = get_ksm_page(stable_node_any, false); | |
1795 | } | |
1796 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); | |
f2e5ff85 AA |
1797 | if (!tree_page) { |
1798 | /* | |
1799 | * If we walked over a stale stable_node, | |
1800 | * get_ksm_page() will call rb_erase() and it | |
1801 | * may rebalance the tree from under us. So | |
1802 | * restart the search from scratch. Returning | |
1803 | * NULL would be safe too, but we'd generate | |
1804 | * false negative insertions just because some | |
1805 | * stable_node was stale. | |
1806 | */ | |
1807 | goto again; | |
1808 | } | |
31dbd01f | 1809 | |
4035c07a HD |
1810 | ret = memcmp_pages(kpage, tree_page); |
1811 | put_page(tree_page); | |
31dbd01f IE |
1812 | |
1813 | parent = *new; | |
1814 | if (ret < 0) | |
1815 | new = &parent->rb_left; | |
1816 | else if (ret > 0) | |
1817 | new = &parent->rb_right; | |
1818 | else { | |
2c653d0e AA |
1819 | need_chain = true; |
1820 | break; | |
31dbd01f IE |
1821 | } |
1822 | } | |
1823 | ||
2c653d0e AA |
1824 | stable_node_dup = alloc_stable_node(); |
1825 | if (!stable_node_dup) | |
7b6ba2c7 | 1826 | return NULL; |
31dbd01f | 1827 | |
2c653d0e AA |
1828 | INIT_HLIST_HEAD(&stable_node_dup->hlist); |
1829 | stable_node_dup->kpfn = kpfn; | |
1830 | set_page_stable_node(kpage, stable_node_dup); | |
1831 | stable_node_dup->rmap_hlist_len = 0; | |
1832 | DO_NUMA(stable_node_dup->nid = nid); | |
1833 | if (!need_chain) { | |
1834 | rb_link_node(&stable_node_dup->node, parent, new); | |
1835 | rb_insert_color(&stable_node_dup->node, root); | |
1836 | } else { | |
1837 | if (!is_stable_node_chain(stable_node)) { | |
1838 | struct stable_node *orig = stable_node; | |
1839 | /* chain is missing so create it */ | |
1840 | stable_node = alloc_stable_node_chain(orig, root); | |
1841 | if (!stable_node) { | |
1842 | free_stable_node(stable_node_dup); | |
1843 | return NULL; | |
1844 | } | |
1845 | } | |
1846 | stable_node_chain_add_dup(stable_node_dup, stable_node); | |
1847 | } | |
08beca44 | 1848 | |
2c653d0e | 1849 | return stable_node_dup; |
31dbd01f IE |
1850 | } |
1851 | ||
1852 | /* | |
8dd3557a HD |
1853 | * unstable_tree_search_insert - search for identical page, |
1854 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
1855 | * |
1856 | * This function searches for a page in the unstable tree identical to the | |
1857 | * page currently being scanned; and if no identical page is found in the | |
1858 | * tree, we insert rmap_item as a new object into the unstable tree. | |
1859 | * | |
1860 | * This function returns pointer to rmap_item found to be identical | |
1861 | * to the currently scanned page, NULL otherwise. | |
1862 | * | |
1863 | * This function does both searching and inserting, because they share | |
1864 | * the same walking algorithm in an rbtree. | |
1865 | */ | |
8dd3557a HD |
1866 | static |
1867 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
1868 | struct page *page, | |
1869 | struct page **tree_pagep) | |
31dbd01f | 1870 | { |
90bd6fd3 PH |
1871 | struct rb_node **new; |
1872 | struct rb_root *root; | |
31dbd01f | 1873 | struct rb_node *parent = NULL; |
90bd6fd3 PH |
1874 | int nid; |
1875 | ||
1876 | nid = get_kpfn_nid(page_to_pfn(page)); | |
ef53d16c | 1877 | root = root_unstable_tree + nid; |
90bd6fd3 | 1878 | new = &root->rb_node; |
31dbd01f IE |
1879 | |
1880 | while (*new) { | |
1881 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 1882 | struct page *tree_page; |
31dbd01f IE |
1883 | int ret; |
1884 | ||
d178f27f | 1885 | cond_resched(); |
31dbd01f | 1886 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a | 1887 | tree_page = get_mergeable_page(tree_rmap_item); |
c8f95ed1 | 1888 | if (!tree_page) |
31dbd01f IE |
1889 | return NULL; |
1890 | ||
1891 | /* | |
8dd3557a | 1892 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1893 | */ |
8dd3557a HD |
1894 | if (page == tree_page) { |
1895 | put_page(tree_page); | |
31dbd01f IE |
1896 | return NULL; |
1897 | } | |
1898 | ||
8dd3557a | 1899 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1900 | |
1901 | parent = *new; | |
1902 | if (ret < 0) { | |
8dd3557a | 1903 | put_page(tree_page); |
31dbd01f IE |
1904 | new = &parent->rb_left; |
1905 | } else if (ret > 0) { | |
8dd3557a | 1906 | put_page(tree_page); |
31dbd01f | 1907 | new = &parent->rb_right; |
b599cbdf HD |
1908 | } else if (!ksm_merge_across_nodes && |
1909 | page_to_nid(tree_page) != nid) { | |
1910 | /* | |
1911 | * If tree_page has been migrated to another NUMA node, | |
1912 | * it will be flushed out and put in the right unstable | |
1913 | * tree next time: only merge with it when across_nodes. | |
1914 | */ | |
1915 | put_page(tree_page); | |
1916 | return NULL; | |
31dbd01f | 1917 | } else { |
8dd3557a | 1918 | *tree_pagep = tree_page; |
31dbd01f IE |
1919 | return tree_rmap_item; |
1920 | } | |
1921 | } | |
1922 | ||
7b6ba2c7 | 1923 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f | 1924 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
e850dcf5 | 1925 | DO_NUMA(rmap_item->nid = nid); |
31dbd01f | 1926 | rb_link_node(&rmap_item->node, parent, new); |
90bd6fd3 | 1927 | rb_insert_color(&rmap_item->node, root); |
31dbd01f | 1928 | |
473b0ce4 | 1929 | ksm_pages_unshared++; |
31dbd01f IE |
1930 | return NULL; |
1931 | } | |
1932 | ||
1933 | /* | |
1934 | * stable_tree_append - add another rmap_item to the linked list of | |
1935 | * rmap_items hanging off a given node of the stable tree, all sharing | |
1936 | * the same ksm page. | |
1937 | */ | |
1938 | static void stable_tree_append(struct rmap_item *rmap_item, | |
2c653d0e AA |
1939 | struct stable_node *stable_node, |
1940 | bool max_page_sharing_bypass) | |
31dbd01f | 1941 | { |
2c653d0e AA |
1942 | /* |
1943 | * rmap won't find this mapping if we don't insert the | |
1944 | * rmap_item in the right stable_node | |
1945 | * duplicate. page_migration could break later if rmap breaks, | |
1946 | * so we can as well crash here. We really need to check for | |
1947 | * rmap_hlist_len == STABLE_NODE_CHAIN, but we can as well check | |
1948 | * for other negative values as an undeflow if detected here | |
1949 | * for the first time (and not when decreasing rmap_hlist_len) | |
1950 | * would be sign of memory corruption in the stable_node. | |
1951 | */ | |
1952 | BUG_ON(stable_node->rmap_hlist_len < 0); | |
1953 | ||
1954 | stable_node->rmap_hlist_len++; | |
1955 | if (!max_page_sharing_bypass) | |
1956 | /* possibly non fatal but unexpected overflow, only warn */ | |
1957 | WARN_ON_ONCE(stable_node->rmap_hlist_len > | |
1958 | ksm_max_page_sharing); | |
1959 | ||
7b6ba2c7 | 1960 | rmap_item->head = stable_node; |
31dbd01f | 1961 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 1962 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 1963 | |
7b6ba2c7 HD |
1964 | if (rmap_item->hlist.next) |
1965 | ksm_pages_sharing++; | |
1966 | else | |
1967 | ksm_pages_shared++; | |
31dbd01f IE |
1968 | } |
1969 | ||
1970 | /* | |
81464e30 HD |
1971 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
1972 | * if not, compare checksum to previous and if it's the same, see if page can | |
1973 | * be inserted into the unstable tree, or merged with a page already there and | |
1974 | * both transferred to the stable tree. | |
31dbd01f IE |
1975 | * |
1976 | * @page: the page that we are searching identical page to. | |
1977 | * @rmap_item: the reverse mapping into the virtual address of this page | |
1978 | */ | |
1979 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
1980 | { | |
31dbd01f | 1981 | struct rmap_item *tree_rmap_item; |
8dd3557a | 1982 | struct page *tree_page = NULL; |
7b6ba2c7 | 1983 | struct stable_node *stable_node; |
8dd3557a | 1984 | struct page *kpage; |
31dbd01f IE |
1985 | unsigned int checksum; |
1986 | int err; | |
2c653d0e | 1987 | bool max_page_sharing_bypass = false; |
31dbd01f | 1988 | |
4146d2d6 HD |
1989 | stable_node = page_stable_node(page); |
1990 | if (stable_node) { | |
1991 | if (stable_node->head != &migrate_nodes && | |
2c653d0e AA |
1992 | get_kpfn_nid(READ_ONCE(stable_node->kpfn)) != |
1993 | NUMA(stable_node->nid)) { | |
1994 | stable_node_dup_del(stable_node); | |
4146d2d6 HD |
1995 | stable_node->head = &migrate_nodes; |
1996 | list_add(&stable_node->list, stable_node->head); | |
1997 | } | |
1998 | if (stable_node->head != &migrate_nodes && | |
1999 | rmap_item->head == stable_node) | |
2000 | return; | |
2c653d0e AA |
2001 | /* |
2002 | * If it's a KSM fork, allow it to go over the sharing limit | |
2003 | * without warnings. | |
2004 | */ | |
2005 | if (!is_page_sharing_candidate(stable_node)) | |
2006 | max_page_sharing_bypass = true; | |
4146d2d6 | 2007 | } |
31dbd01f IE |
2008 | |
2009 | /* We first start with searching the page inside the stable tree */ | |
62b61f61 | 2010 | kpage = stable_tree_search(page); |
4146d2d6 HD |
2011 | if (kpage == page && rmap_item->head == stable_node) { |
2012 | put_page(kpage); | |
2013 | return; | |
2014 | } | |
2015 | ||
2016 | remove_rmap_item_from_tree(rmap_item); | |
2017 | ||
62b61f61 | 2018 | if (kpage) { |
08beca44 | 2019 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
31dbd01f IE |
2020 | if (!err) { |
2021 | /* | |
2022 | * The page was successfully merged: | |
2023 | * add its rmap_item to the stable tree. | |
2024 | */ | |
5ad64688 | 2025 | lock_page(kpage); |
2c653d0e AA |
2026 | stable_tree_append(rmap_item, page_stable_node(kpage), |
2027 | max_page_sharing_bypass); | |
5ad64688 | 2028 | unlock_page(kpage); |
31dbd01f | 2029 | } |
8dd3557a | 2030 | put_page(kpage); |
31dbd01f IE |
2031 | return; |
2032 | } | |
2033 | ||
2034 | /* | |
4035c07a HD |
2035 | * If the hash value of the page has changed from the last time |
2036 | * we calculated it, this page is changing frequently: therefore we | |
2037 | * don't want to insert it in the unstable tree, and we don't want | |
2038 | * to waste our time searching for something identical to it there. | |
31dbd01f IE |
2039 | */ |
2040 | checksum = calc_checksum(page); | |
2041 | if (rmap_item->oldchecksum != checksum) { | |
2042 | rmap_item->oldchecksum = checksum; | |
2043 | return; | |
2044 | } | |
2045 | ||
e86c59b1 CI |
2046 | /* |
2047 | * Same checksum as an empty page. We attempt to merge it with the | |
2048 | * appropriate zero page if the user enabled this via sysfs. | |
2049 | */ | |
2050 | if (ksm_use_zero_pages && (checksum == zero_checksum)) { | |
2051 | struct vm_area_struct *vma; | |
2052 | ||
2053 | vma = find_mergeable_vma(rmap_item->mm, rmap_item->address); | |
2054 | err = try_to_merge_one_page(vma, page, | |
2055 | ZERO_PAGE(rmap_item->address)); | |
2056 | /* | |
2057 | * In case of failure, the page was not really empty, so we | |
2058 | * need to continue. Otherwise we're done. | |
2059 | */ | |
2060 | if (!err) | |
2061 | return; | |
2062 | } | |
8dd3557a HD |
2063 | tree_rmap_item = |
2064 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 2065 | if (tree_rmap_item) { |
8dd3557a HD |
2066 | kpage = try_to_merge_two_pages(rmap_item, page, |
2067 | tree_rmap_item, tree_page); | |
2068 | put_page(tree_page); | |
8dd3557a | 2069 | if (kpage) { |
bc56620b HD |
2070 | /* |
2071 | * The pages were successfully merged: insert new | |
2072 | * node in the stable tree and add both rmap_items. | |
2073 | */ | |
5ad64688 | 2074 | lock_page(kpage); |
7b6ba2c7 HD |
2075 | stable_node = stable_tree_insert(kpage); |
2076 | if (stable_node) { | |
2c653d0e AA |
2077 | stable_tree_append(tree_rmap_item, stable_node, |
2078 | false); | |
2079 | stable_tree_append(rmap_item, stable_node, | |
2080 | false); | |
7b6ba2c7 | 2081 | } |
5ad64688 | 2082 | unlock_page(kpage); |
7b6ba2c7 | 2083 | |
31dbd01f IE |
2084 | /* |
2085 | * If we fail to insert the page into the stable tree, | |
2086 | * we will have 2 virtual addresses that are pointing | |
2087 | * to a ksm page left outside the stable tree, | |
2088 | * in which case we need to break_cow on both. | |
2089 | */ | |
7b6ba2c7 | 2090 | if (!stable_node) { |
8dd3557a HD |
2091 | break_cow(tree_rmap_item); |
2092 | break_cow(rmap_item); | |
31dbd01f IE |
2093 | } |
2094 | } | |
31dbd01f IE |
2095 | } |
2096 | } | |
2097 | ||
2098 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 2099 | struct rmap_item **rmap_list, |
31dbd01f IE |
2100 | unsigned long addr) |
2101 | { | |
2102 | struct rmap_item *rmap_item; | |
2103 | ||
6514d511 HD |
2104 | while (*rmap_list) { |
2105 | rmap_item = *rmap_list; | |
93d17715 | 2106 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 2107 | return rmap_item; |
31dbd01f IE |
2108 | if (rmap_item->address > addr) |
2109 | break; | |
6514d511 | 2110 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 2111 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
2112 | free_rmap_item(rmap_item); |
2113 | } | |
2114 | ||
2115 | rmap_item = alloc_rmap_item(); | |
2116 | if (rmap_item) { | |
2117 | /* It has already been zeroed */ | |
2118 | rmap_item->mm = mm_slot->mm; | |
2119 | rmap_item->address = addr; | |
6514d511 HD |
2120 | rmap_item->rmap_list = *rmap_list; |
2121 | *rmap_list = rmap_item; | |
31dbd01f IE |
2122 | } |
2123 | return rmap_item; | |
2124 | } | |
2125 | ||
2126 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
2127 | { | |
2128 | struct mm_struct *mm; | |
2129 | struct mm_slot *slot; | |
2130 | struct vm_area_struct *vma; | |
2131 | struct rmap_item *rmap_item; | |
90bd6fd3 | 2132 | int nid; |
31dbd01f IE |
2133 | |
2134 | if (list_empty(&ksm_mm_head.mm_list)) | |
2135 | return NULL; | |
2136 | ||
2137 | slot = ksm_scan.mm_slot; | |
2138 | if (slot == &ksm_mm_head) { | |
2919bfd0 HD |
2139 | /* |
2140 | * A number of pages can hang around indefinitely on per-cpu | |
2141 | * pagevecs, raised page count preventing write_protect_page | |
2142 | * from merging them. Though it doesn't really matter much, | |
2143 | * it is puzzling to see some stuck in pages_volatile until | |
2144 | * other activity jostles them out, and they also prevented | |
2145 | * LTP's KSM test from succeeding deterministically; so drain | |
2146 | * them here (here rather than on entry to ksm_do_scan(), | |
2147 | * so we don't IPI too often when pages_to_scan is set low). | |
2148 | */ | |
2149 | lru_add_drain_all(); | |
2150 | ||
4146d2d6 HD |
2151 | /* |
2152 | * Whereas stale stable_nodes on the stable_tree itself | |
2153 | * get pruned in the regular course of stable_tree_search(), | |
2154 | * those moved out to the migrate_nodes list can accumulate: | |
2155 | * so prune them once before each full scan. | |
2156 | */ | |
2157 | if (!ksm_merge_across_nodes) { | |
03640418 | 2158 | struct stable_node *stable_node, *next; |
4146d2d6 HD |
2159 | struct page *page; |
2160 | ||
03640418 GT |
2161 | list_for_each_entry_safe(stable_node, next, |
2162 | &migrate_nodes, list) { | |
4146d2d6 HD |
2163 | page = get_ksm_page(stable_node, false); |
2164 | if (page) | |
2165 | put_page(page); | |
2166 | cond_resched(); | |
2167 | } | |
2168 | } | |
2169 | ||
ef53d16c | 2170 | for (nid = 0; nid < ksm_nr_node_ids; nid++) |
90bd6fd3 | 2171 | root_unstable_tree[nid] = RB_ROOT; |
31dbd01f IE |
2172 | |
2173 | spin_lock(&ksm_mmlist_lock); | |
2174 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
2175 | ksm_scan.mm_slot = slot; | |
2176 | spin_unlock(&ksm_mmlist_lock); | |
2b472611 HD |
2177 | /* |
2178 | * Although we tested list_empty() above, a racing __ksm_exit | |
2179 | * of the last mm on the list may have removed it since then. | |
2180 | */ | |
2181 | if (slot == &ksm_mm_head) | |
2182 | return NULL; | |
31dbd01f IE |
2183 | next_mm: |
2184 | ksm_scan.address = 0; | |
6514d511 | 2185 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
2186 | } |
2187 | ||
2188 | mm = slot->mm; | |
2189 | down_read(&mm->mmap_sem); | |
9ba69294 HD |
2190 | if (ksm_test_exit(mm)) |
2191 | vma = NULL; | |
2192 | else | |
2193 | vma = find_vma(mm, ksm_scan.address); | |
2194 | ||
2195 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
2196 | if (!(vma->vm_flags & VM_MERGEABLE)) |
2197 | continue; | |
2198 | if (ksm_scan.address < vma->vm_start) | |
2199 | ksm_scan.address = vma->vm_start; | |
2200 | if (!vma->anon_vma) | |
2201 | ksm_scan.address = vma->vm_end; | |
2202 | ||
2203 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
2204 | if (ksm_test_exit(mm)) |
2205 | break; | |
31dbd01f | 2206 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
21ae5b01 AA |
2207 | if (IS_ERR_OR_NULL(*page)) { |
2208 | ksm_scan.address += PAGE_SIZE; | |
2209 | cond_resched(); | |
2210 | continue; | |
2211 | } | |
f765f540 | 2212 | if (PageAnon(*page)) { |
31dbd01f IE |
2213 | flush_anon_page(vma, *page, ksm_scan.address); |
2214 | flush_dcache_page(*page); | |
2215 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 2216 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 2217 | if (rmap_item) { |
6514d511 HD |
2218 | ksm_scan.rmap_list = |
2219 | &rmap_item->rmap_list; | |
31dbd01f IE |
2220 | ksm_scan.address += PAGE_SIZE; |
2221 | } else | |
2222 | put_page(*page); | |
2223 | up_read(&mm->mmap_sem); | |
2224 | return rmap_item; | |
2225 | } | |
21ae5b01 | 2226 | put_page(*page); |
31dbd01f IE |
2227 | ksm_scan.address += PAGE_SIZE; |
2228 | cond_resched(); | |
2229 | } | |
2230 | } | |
2231 | ||
9ba69294 HD |
2232 | if (ksm_test_exit(mm)) { |
2233 | ksm_scan.address = 0; | |
6514d511 | 2234 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 2235 | } |
31dbd01f IE |
2236 | /* |
2237 | * Nuke all the rmap_items that are above this current rmap: | |
2238 | * because there were no VM_MERGEABLE vmas with such addresses. | |
2239 | */ | |
6514d511 | 2240 | remove_trailing_rmap_items(slot, ksm_scan.rmap_list); |
31dbd01f IE |
2241 | |
2242 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
2243 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
2244 | struct mm_slot, mm_list); | |
2245 | if (ksm_scan.address == 0) { | |
2246 | /* | |
2247 | * We've completed a full scan of all vmas, holding mmap_sem | |
2248 | * throughout, and found no VM_MERGEABLE: so do the same as | |
2249 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
2250 | * This applies either when cleaning up after __ksm_exit |
2251 | * (but beware: we can reach here even before __ksm_exit), | |
2252 | * or when all VM_MERGEABLE areas have been unmapped (and | |
2253 | * mmap_sem then protects against race with MADV_MERGEABLE). | |
cd551f97 | 2254 | */ |
4ca3a69b | 2255 | hash_del(&slot->link); |
cd551f97 | 2256 | list_del(&slot->mm_list); |
9ba69294 HD |
2257 | spin_unlock(&ksm_mmlist_lock); |
2258 | ||
cd551f97 HD |
2259 | free_mm_slot(slot); |
2260 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 HD |
2261 | up_read(&mm->mmap_sem); |
2262 | mmdrop(mm); | |
2263 | } else { | |
9ba69294 | 2264 | up_read(&mm->mmap_sem); |
7496fea9 ZC |
2265 | /* |
2266 | * up_read(&mm->mmap_sem) first because after | |
2267 | * spin_unlock(&ksm_mmlist_lock) run, the "mm" may | |
2268 | * already have been freed under us by __ksm_exit() | |
2269 | * because the "mm_slot" is still hashed and | |
2270 | * ksm_scan.mm_slot doesn't point to it anymore. | |
2271 | */ | |
2272 | spin_unlock(&ksm_mmlist_lock); | |
cd551f97 | 2273 | } |
31dbd01f IE |
2274 | |
2275 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 2276 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
2277 | if (slot != &ksm_mm_head) |
2278 | goto next_mm; | |
2279 | ||
31dbd01f IE |
2280 | ksm_scan.seqnr++; |
2281 | return NULL; | |
2282 | } | |
2283 | ||
2284 | /** | |
2285 | * ksm_do_scan - the ksm scanner main worker function. | |
2286 | * @scan_npages - number of pages we want to scan before we return. | |
2287 | */ | |
2288 | static void ksm_do_scan(unsigned int scan_npages) | |
2289 | { | |
2290 | struct rmap_item *rmap_item; | |
22eccdd7 | 2291 | struct page *uninitialized_var(page); |
31dbd01f | 2292 | |
878aee7d | 2293 | while (scan_npages-- && likely(!freezing(current))) { |
31dbd01f IE |
2294 | cond_resched(); |
2295 | rmap_item = scan_get_next_rmap_item(&page); | |
2296 | if (!rmap_item) | |
2297 | return; | |
4146d2d6 | 2298 | cmp_and_merge_page(page, rmap_item); |
31dbd01f IE |
2299 | put_page(page); |
2300 | } | |
2301 | } | |
2302 | ||
6e158384 HD |
2303 | static int ksmd_should_run(void) |
2304 | { | |
2305 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
2306 | } | |
2307 | ||
31dbd01f IE |
2308 | static int ksm_scan_thread(void *nothing) |
2309 | { | |
878aee7d | 2310 | set_freezable(); |
339aa624 | 2311 | set_user_nice(current, 5); |
31dbd01f IE |
2312 | |
2313 | while (!kthread_should_stop()) { | |
6e158384 | 2314 | mutex_lock(&ksm_thread_mutex); |
ef4d43a8 | 2315 | wait_while_offlining(); |
6e158384 | 2316 | if (ksmd_should_run()) |
31dbd01f | 2317 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
2318 | mutex_unlock(&ksm_thread_mutex); |
2319 | ||
878aee7d AA |
2320 | try_to_freeze(); |
2321 | ||
6e158384 | 2322 | if (ksmd_should_run()) { |
31dbd01f IE |
2323 | schedule_timeout_interruptible( |
2324 | msecs_to_jiffies(ksm_thread_sleep_millisecs)); | |
2325 | } else { | |
878aee7d | 2326 | wait_event_freezable(ksm_thread_wait, |
6e158384 | 2327 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
2328 | } |
2329 | } | |
2330 | return 0; | |
2331 | } | |
2332 | ||
f8af4da3 HD |
2333 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
2334 | unsigned long end, int advice, unsigned long *vm_flags) | |
2335 | { | |
2336 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 2337 | int err; |
f8af4da3 HD |
2338 | |
2339 | switch (advice) { | |
2340 | case MADV_MERGEABLE: | |
2341 | /* | |
2342 | * Be somewhat over-protective for now! | |
2343 | */ | |
2344 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
2345 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
0661a336 | 2346 | VM_HUGETLB | VM_MIXEDMAP)) |
f8af4da3 HD |
2347 | return 0; /* just ignore the advice */ |
2348 | ||
cc2383ec KK |
2349 | #ifdef VM_SAO |
2350 | if (*vm_flags & VM_SAO) | |
2351 | return 0; | |
2352 | #endif | |
2353 | ||
d952b791 HD |
2354 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
2355 | err = __ksm_enter(mm); | |
2356 | if (err) | |
2357 | return err; | |
2358 | } | |
f8af4da3 HD |
2359 | |
2360 | *vm_flags |= VM_MERGEABLE; | |
2361 | break; | |
2362 | ||
2363 | case MADV_UNMERGEABLE: | |
2364 | if (!(*vm_flags & VM_MERGEABLE)) | |
2365 | return 0; /* just ignore the advice */ | |
2366 | ||
d952b791 HD |
2367 | if (vma->anon_vma) { |
2368 | err = unmerge_ksm_pages(vma, start, end); | |
2369 | if (err) | |
2370 | return err; | |
2371 | } | |
f8af4da3 HD |
2372 | |
2373 | *vm_flags &= ~VM_MERGEABLE; | |
2374 | break; | |
2375 | } | |
2376 | ||
2377 | return 0; | |
2378 | } | |
2379 | ||
2380 | int __ksm_enter(struct mm_struct *mm) | |
2381 | { | |
6e158384 HD |
2382 | struct mm_slot *mm_slot; |
2383 | int needs_wakeup; | |
2384 | ||
2385 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
2386 | if (!mm_slot) |
2387 | return -ENOMEM; | |
2388 | ||
6e158384 HD |
2389 | /* Check ksm_run too? Would need tighter locking */ |
2390 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
2391 | ||
31dbd01f IE |
2392 | spin_lock(&ksm_mmlist_lock); |
2393 | insert_to_mm_slots_hash(mm, mm_slot); | |
2394 | /* | |
cbf86cfe HD |
2395 | * When KSM_RUN_MERGE (or KSM_RUN_STOP), |
2396 | * insert just behind the scanning cursor, to let the area settle | |
31dbd01f IE |
2397 | * down a little; when fork is followed by immediate exec, we don't |
2398 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
cbf86cfe HD |
2399 | * |
2400 | * But when KSM_RUN_UNMERGE, it's important to insert ahead of its | |
2401 | * scanning cursor, otherwise KSM pages in newly forked mms will be | |
2402 | * missed: then we might as well insert at the end of the list. | |
31dbd01f | 2403 | */ |
cbf86cfe HD |
2404 | if (ksm_run & KSM_RUN_UNMERGE) |
2405 | list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); | |
2406 | else | |
2407 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
31dbd01f IE |
2408 | spin_unlock(&ksm_mmlist_lock); |
2409 | ||
f8af4da3 | 2410 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
f1f10076 | 2411 | mmgrab(mm); |
6e158384 HD |
2412 | |
2413 | if (needs_wakeup) | |
2414 | wake_up_interruptible(&ksm_thread_wait); | |
2415 | ||
f8af4da3 HD |
2416 | return 0; |
2417 | } | |
2418 | ||
1c2fb7a4 | 2419 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 2420 | { |
cd551f97 | 2421 | struct mm_slot *mm_slot; |
9ba69294 | 2422 | int easy_to_free = 0; |
cd551f97 | 2423 | |
31dbd01f | 2424 | /* |
9ba69294 HD |
2425 | * This process is exiting: if it's straightforward (as is the |
2426 | * case when ksmd was never running), free mm_slot immediately. | |
2427 | * But if it's at the cursor or has rmap_items linked to it, use | |
2428 | * mmap_sem to synchronize with any break_cows before pagetables | |
2429 | * are freed, and leave the mm_slot on the list for ksmd to free. | |
2430 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 2431 | */ |
9ba69294 | 2432 | |
cd551f97 HD |
2433 | spin_lock(&ksm_mmlist_lock); |
2434 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 2435 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 2436 | if (!mm_slot->rmap_list) { |
4ca3a69b | 2437 | hash_del(&mm_slot->link); |
9ba69294 HD |
2438 | list_del(&mm_slot->mm_list); |
2439 | easy_to_free = 1; | |
2440 | } else { | |
2441 | list_move(&mm_slot->mm_list, | |
2442 | &ksm_scan.mm_slot->mm_list); | |
2443 | } | |
cd551f97 | 2444 | } |
cd551f97 HD |
2445 | spin_unlock(&ksm_mmlist_lock); |
2446 | ||
9ba69294 HD |
2447 | if (easy_to_free) { |
2448 | free_mm_slot(mm_slot); | |
2449 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
2450 | mmdrop(mm); | |
2451 | } else if (mm_slot) { | |
9ba69294 HD |
2452 | down_write(&mm->mmap_sem); |
2453 | up_write(&mm->mmap_sem); | |
9ba69294 | 2454 | } |
31dbd01f IE |
2455 | } |
2456 | ||
cbf86cfe | 2457 | struct page *ksm_might_need_to_copy(struct page *page, |
5ad64688 HD |
2458 | struct vm_area_struct *vma, unsigned long address) |
2459 | { | |
cbf86cfe | 2460 | struct anon_vma *anon_vma = page_anon_vma(page); |
5ad64688 HD |
2461 | struct page *new_page; |
2462 | ||
cbf86cfe HD |
2463 | if (PageKsm(page)) { |
2464 | if (page_stable_node(page) && | |
2465 | !(ksm_run & KSM_RUN_UNMERGE)) | |
2466 | return page; /* no need to copy it */ | |
2467 | } else if (!anon_vma) { | |
2468 | return page; /* no need to copy it */ | |
2469 | } else if (anon_vma->root == vma->anon_vma->root && | |
2470 | page->index == linear_page_index(vma, address)) { | |
2471 | return page; /* still no need to copy it */ | |
2472 | } | |
2473 | if (!PageUptodate(page)) | |
2474 | return page; /* let do_swap_page report the error */ | |
2475 | ||
5ad64688 HD |
2476 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
2477 | if (new_page) { | |
2478 | copy_user_highpage(new_page, page, address, vma); | |
2479 | ||
2480 | SetPageDirty(new_page); | |
2481 | __SetPageUptodate(new_page); | |
48c935ad | 2482 | __SetPageLocked(new_page); |
5ad64688 HD |
2483 | } |
2484 | ||
5ad64688 HD |
2485 | return new_page; |
2486 | } | |
2487 | ||
1df631ae | 2488 | void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc) |
e9995ef9 HD |
2489 | { |
2490 | struct stable_node *stable_node; | |
e9995ef9 | 2491 | struct rmap_item *rmap_item; |
e9995ef9 HD |
2492 | int search_new_forks = 0; |
2493 | ||
309381fe | 2494 | VM_BUG_ON_PAGE(!PageKsm(page), page); |
9f32624b JK |
2495 | |
2496 | /* | |
2497 | * Rely on the page lock to protect against concurrent modifications | |
2498 | * to that page's node of the stable tree. | |
2499 | */ | |
309381fe | 2500 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
e9995ef9 HD |
2501 | |
2502 | stable_node = page_stable_node(page); | |
2503 | if (!stable_node) | |
1df631ae | 2504 | return; |
e9995ef9 | 2505 | again: |
b67bfe0d | 2506 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
e9995ef9 | 2507 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 2508 | struct anon_vma_chain *vmac; |
e9995ef9 HD |
2509 | struct vm_area_struct *vma; |
2510 | ||
ad12695f | 2511 | cond_resched(); |
b6b19f25 | 2512 | anon_vma_lock_read(anon_vma); |
bf181b9f ML |
2513 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
2514 | 0, ULONG_MAX) { | |
ad12695f | 2515 | cond_resched(); |
5beb4930 | 2516 | vma = vmac->vma; |
e9995ef9 HD |
2517 | if (rmap_item->address < vma->vm_start || |
2518 | rmap_item->address >= vma->vm_end) | |
2519 | continue; | |
2520 | /* | |
2521 | * Initially we examine only the vma which covers this | |
2522 | * rmap_item; but later, if there is still work to do, | |
2523 | * we examine covering vmas in other mms: in case they | |
2524 | * were forked from the original since ksmd passed. | |
2525 | */ | |
2526 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
2527 | continue; | |
2528 | ||
0dd1c7bb JK |
2529 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
2530 | continue; | |
2531 | ||
e4b82222 | 2532 | if (!rwc->rmap_one(page, vma, |
1df631ae | 2533 | rmap_item->address, rwc->arg)) { |
b6b19f25 | 2534 | anon_vma_unlock_read(anon_vma); |
1df631ae | 2535 | return; |
e9995ef9 | 2536 | } |
0dd1c7bb JK |
2537 | if (rwc->done && rwc->done(page)) { |
2538 | anon_vma_unlock_read(anon_vma); | |
1df631ae | 2539 | return; |
0dd1c7bb | 2540 | } |
e9995ef9 | 2541 | } |
b6b19f25 | 2542 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
2543 | } |
2544 | if (!search_new_forks++) | |
2545 | goto again; | |
e9995ef9 HD |
2546 | } |
2547 | ||
52629506 | 2548 | #ifdef CONFIG_MIGRATION |
e9995ef9 HD |
2549 | void ksm_migrate_page(struct page *newpage, struct page *oldpage) |
2550 | { | |
2551 | struct stable_node *stable_node; | |
2552 | ||
309381fe SL |
2553 | VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage); |
2554 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); | |
2555 | VM_BUG_ON_PAGE(newpage->mapping != oldpage->mapping, newpage); | |
e9995ef9 HD |
2556 | |
2557 | stable_node = page_stable_node(newpage); | |
2558 | if (stable_node) { | |
309381fe | 2559 | VM_BUG_ON_PAGE(stable_node->kpfn != page_to_pfn(oldpage), oldpage); |
62b61f61 | 2560 | stable_node->kpfn = page_to_pfn(newpage); |
c8d6553b HD |
2561 | /* |
2562 | * newpage->mapping was set in advance; now we need smp_wmb() | |
2563 | * to make sure that the new stable_node->kpfn is visible | |
2564 | * to get_ksm_page() before it can see that oldpage->mapping | |
2565 | * has gone stale (or that PageSwapCache has been cleared). | |
2566 | */ | |
2567 | smp_wmb(); | |
2568 | set_page_stable_node(oldpage, NULL); | |
e9995ef9 HD |
2569 | } |
2570 | } | |
2571 | #endif /* CONFIG_MIGRATION */ | |
2572 | ||
62b61f61 | 2573 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 HD |
2574 | static void wait_while_offlining(void) |
2575 | { | |
2576 | while (ksm_run & KSM_RUN_OFFLINE) { | |
2577 | mutex_unlock(&ksm_thread_mutex); | |
2578 | wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), | |
74316201 | 2579 | TASK_UNINTERRUPTIBLE); |
ef4d43a8 HD |
2580 | mutex_lock(&ksm_thread_mutex); |
2581 | } | |
2582 | } | |
2583 | ||
2c653d0e AA |
2584 | static bool stable_node_dup_remove_range(struct stable_node *stable_node, |
2585 | unsigned long start_pfn, | |
2586 | unsigned long end_pfn) | |
2587 | { | |
2588 | if (stable_node->kpfn >= start_pfn && | |
2589 | stable_node->kpfn < end_pfn) { | |
2590 | /* | |
2591 | * Don't get_ksm_page, page has already gone: | |
2592 | * which is why we keep kpfn instead of page* | |
2593 | */ | |
2594 | remove_node_from_stable_tree(stable_node); | |
2595 | return true; | |
2596 | } | |
2597 | return false; | |
2598 | } | |
2599 | ||
2600 | static bool stable_node_chain_remove_range(struct stable_node *stable_node, | |
2601 | unsigned long start_pfn, | |
2602 | unsigned long end_pfn, | |
2603 | struct rb_root *root) | |
2604 | { | |
2605 | struct stable_node *dup; | |
2606 | struct hlist_node *hlist_safe; | |
2607 | ||
2608 | if (!is_stable_node_chain(stable_node)) { | |
2609 | VM_BUG_ON(is_stable_node_dup(stable_node)); | |
2610 | return stable_node_dup_remove_range(stable_node, start_pfn, | |
2611 | end_pfn); | |
2612 | } | |
2613 | ||
2614 | hlist_for_each_entry_safe(dup, hlist_safe, | |
2615 | &stable_node->hlist, hlist_dup) { | |
2616 | VM_BUG_ON(!is_stable_node_dup(dup)); | |
2617 | stable_node_dup_remove_range(dup, start_pfn, end_pfn); | |
2618 | } | |
2619 | if (hlist_empty(&stable_node->hlist)) { | |
2620 | free_stable_node_chain(stable_node, root); | |
2621 | return true; /* notify caller that tree was rebalanced */ | |
2622 | } else | |
2623 | return false; | |
2624 | } | |
2625 | ||
ee0ea59c HD |
2626 | static void ksm_check_stable_tree(unsigned long start_pfn, |
2627 | unsigned long end_pfn) | |
62b61f61 | 2628 | { |
03640418 | 2629 | struct stable_node *stable_node, *next; |
62b61f61 | 2630 | struct rb_node *node; |
90bd6fd3 | 2631 | int nid; |
62b61f61 | 2632 | |
ef53d16c HD |
2633 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
2634 | node = rb_first(root_stable_tree + nid); | |
ee0ea59c | 2635 | while (node) { |
90bd6fd3 | 2636 | stable_node = rb_entry(node, struct stable_node, node); |
2c653d0e AA |
2637 | if (stable_node_chain_remove_range(stable_node, |
2638 | start_pfn, end_pfn, | |
2639 | root_stable_tree + | |
2640 | nid)) | |
ef53d16c | 2641 | node = rb_first(root_stable_tree + nid); |
2c653d0e | 2642 | else |
ee0ea59c HD |
2643 | node = rb_next(node); |
2644 | cond_resched(); | |
90bd6fd3 | 2645 | } |
ee0ea59c | 2646 | } |
03640418 | 2647 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
2648 | if (stable_node->kpfn >= start_pfn && |
2649 | stable_node->kpfn < end_pfn) | |
2650 | remove_node_from_stable_tree(stable_node); | |
2651 | cond_resched(); | |
2652 | } | |
62b61f61 HD |
2653 | } |
2654 | ||
2655 | static int ksm_memory_callback(struct notifier_block *self, | |
2656 | unsigned long action, void *arg) | |
2657 | { | |
2658 | struct memory_notify *mn = arg; | |
62b61f61 HD |
2659 | |
2660 | switch (action) { | |
2661 | case MEM_GOING_OFFLINE: | |
2662 | /* | |
ef4d43a8 HD |
2663 | * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() |
2664 | * and remove_all_stable_nodes() while memory is going offline: | |
2665 | * it is unsafe for them to touch the stable tree at this time. | |
2666 | * But unmerge_ksm_pages(), rmap lookups and other entry points | |
2667 | * which do not need the ksm_thread_mutex are all safe. | |
62b61f61 | 2668 | */ |
ef4d43a8 HD |
2669 | mutex_lock(&ksm_thread_mutex); |
2670 | ksm_run |= KSM_RUN_OFFLINE; | |
2671 | mutex_unlock(&ksm_thread_mutex); | |
62b61f61 HD |
2672 | break; |
2673 | ||
2674 | case MEM_OFFLINE: | |
2675 | /* | |
2676 | * Most of the work is done by page migration; but there might | |
2677 | * be a few stable_nodes left over, still pointing to struct | |
ee0ea59c HD |
2678 | * pages which have been offlined: prune those from the tree, |
2679 | * otherwise get_ksm_page() might later try to access a | |
2680 | * non-existent struct page. | |
62b61f61 | 2681 | */ |
ee0ea59c HD |
2682 | ksm_check_stable_tree(mn->start_pfn, |
2683 | mn->start_pfn + mn->nr_pages); | |
62b61f61 HD |
2684 | /* fallthrough */ |
2685 | ||
2686 | case MEM_CANCEL_OFFLINE: | |
ef4d43a8 HD |
2687 | mutex_lock(&ksm_thread_mutex); |
2688 | ksm_run &= ~KSM_RUN_OFFLINE; | |
62b61f61 | 2689 | mutex_unlock(&ksm_thread_mutex); |
ef4d43a8 HD |
2690 | |
2691 | smp_mb(); /* wake_up_bit advises this */ | |
2692 | wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); | |
62b61f61 HD |
2693 | break; |
2694 | } | |
2695 | return NOTIFY_OK; | |
2696 | } | |
ef4d43a8 HD |
2697 | #else |
2698 | static void wait_while_offlining(void) | |
2699 | { | |
2700 | } | |
62b61f61 HD |
2701 | #endif /* CONFIG_MEMORY_HOTREMOVE */ |
2702 | ||
2ffd8679 HD |
2703 | #ifdef CONFIG_SYSFS |
2704 | /* | |
2705 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
2706 | */ | |
2707 | ||
31dbd01f IE |
2708 | #define KSM_ATTR_RO(_name) \ |
2709 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
2710 | #define KSM_ATTR(_name) \ | |
2711 | static struct kobj_attribute _name##_attr = \ | |
2712 | __ATTR(_name, 0644, _name##_show, _name##_store) | |
2713 | ||
2714 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
2715 | struct kobj_attribute *attr, char *buf) | |
2716 | { | |
2717 | return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs); | |
2718 | } | |
2719 | ||
2720 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
2721 | struct kobj_attribute *attr, | |
2722 | const char *buf, size_t count) | |
2723 | { | |
2724 | unsigned long msecs; | |
2725 | int err; | |
2726 | ||
3dbb95f7 | 2727 | err = kstrtoul(buf, 10, &msecs); |
31dbd01f IE |
2728 | if (err || msecs > UINT_MAX) |
2729 | return -EINVAL; | |
2730 | ||
2731 | ksm_thread_sleep_millisecs = msecs; | |
2732 | ||
2733 | return count; | |
2734 | } | |
2735 | KSM_ATTR(sleep_millisecs); | |
2736 | ||
2737 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
2738 | struct kobj_attribute *attr, char *buf) | |
2739 | { | |
2740 | return sprintf(buf, "%u\n", ksm_thread_pages_to_scan); | |
2741 | } | |
2742 | ||
2743 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
2744 | struct kobj_attribute *attr, | |
2745 | const char *buf, size_t count) | |
2746 | { | |
2747 | int err; | |
2748 | unsigned long nr_pages; | |
2749 | ||
3dbb95f7 | 2750 | err = kstrtoul(buf, 10, &nr_pages); |
31dbd01f IE |
2751 | if (err || nr_pages > UINT_MAX) |
2752 | return -EINVAL; | |
2753 | ||
2754 | ksm_thread_pages_to_scan = nr_pages; | |
2755 | ||
2756 | return count; | |
2757 | } | |
2758 | KSM_ATTR(pages_to_scan); | |
2759 | ||
2760 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
2761 | char *buf) | |
2762 | { | |
ef4d43a8 | 2763 | return sprintf(buf, "%lu\n", ksm_run); |
31dbd01f IE |
2764 | } |
2765 | ||
2766 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
2767 | const char *buf, size_t count) | |
2768 | { | |
2769 | int err; | |
2770 | unsigned long flags; | |
2771 | ||
3dbb95f7 | 2772 | err = kstrtoul(buf, 10, &flags); |
31dbd01f IE |
2773 | if (err || flags > UINT_MAX) |
2774 | return -EINVAL; | |
2775 | if (flags > KSM_RUN_UNMERGE) | |
2776 | return -EINVAL; | |
2777 | ||
2778 | /* | |
2779 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
2780 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
d0f209f6 HD |
2781 | * breaking COW to free the pages_shared (but leaves mm_slots |
2782 | * on the list for when ksmd may be set running again). | |
31dbd01f IE |
2783 | */ |
2784 | ||
2785 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2786 | wait_while_offlining(); |
31dbd01f IE |
2787 | if (ksm_run != flags) { |
2788 | ksm_run = flags; | |
d952b791 | 2789 | if (flags & KSM_RUN_UNMERGE) { |
e1e12d2f | 2790 | set_current_oom_origin(); |
d952b791 | 2791 | err = unmerge_and_remove_all_rmap_items(); |
e1e12d2f | 2792 | clear_current_oom_origin(); |
d952b791 HD |
2793 | if (err) { |
2794 | ksm_run = KSM_RUN_STOP; | |
2795 | count = err; | |
2796 | } | |
2797 | } | |
31dbd01f IE |
2798 | } |
2799 | mutex_unlock(&ksm_thread_mutex); | |
2800 | ||
2801 | if (flags & KSM_RUN_MERGE) | |
2802 | wake_up_interruptible(&ksm_thread_wait); | |
2803 | ||
2804 | return count; | |
2805 | } | |
2806 | KSM_ATTR(run); | |
2807 | ||
90bd6fd3 PH |
2808 | #ifdef CONFIG_NUMA |
2809 | static ssize_t merge_across_nodes_show(struct kobject *kobj, | |
2810 | struct kobj_attribute *attr, char *buf) | |
2811 | { | |
2812 | return sprintf(buf, "%u\n", ksm_merge_across_nodes); | |
2813 | } | |
2814 | ||
2815 | static ssize_t merge_across_nodes_store(struct kobject *kobj, | |
2816 | struct kobj_attribute *attr, | |
2817 | const char *buf, size_t count) | |
2818 | { | |
2819 | int err; | |
2820 | unsigned long knob; | |
2821 | ||
2822 | err = kstrtoul(buf, 10, &knob); | |
2823 | if (err) | |
2824 | return err; | |
2825 | if (knob > 1) | |
2826 | return -EINVAL; | |
2827 | ||
2828 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2829 | wait_while_offlining(); |
90bd6fd3 | 2830 | if (ksm_merge_across_nodes != knob) { |
cbf86cfe | 2831 | if (ksm_pages_shared || remove_all_stable_nodes()) |
90bd6fd3 | 2832 | err = -EBUSY; |
ef53d16c HD |
2833 | else if (root_stable_tree == one_stable_tree) { |
2834 | struct rb_root *buf; | |
2835 | /* | |
2836 | * This is the first time that we switch away from the | |
2837 | * default of merging across nodes: must now allocate | |
2838 | * a buffer to hold as many roots as may be needed. | |
2839 | * Allocate stable and unstable together: | |
2840 | * MAXSMP NODES_SHIFT 10 will use 16kB. | |
2841 | */ | |
bafe1e14 JP |
2842 | buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf), |
2843 | GFP_KERNEL); | |
ef53d16c HD |
2844 | /* Let us assume that RB_ROOT is NULL is zero */ |
2845 | if (!buf) | |
2846 | err = -ENOMEM; | |
2847 | else { | |
2848 | root_stable_tree = buf; | |
2849 | root_unstable_tree = buf + nr_node_ids; | |
2850 | /* Stable tree is empty but not the unstable */ | |
2851 | root_unstable_tree[0] = one_unstable_tree[0]; | |
2852 | } | |
2853 | } | |
2854 | if (!err) { | |
90bd6fd3 | 2855 | ksm_merge_across_nodes = knob; |
ef53d16c HD |
2856 | ksm_nr_node_ids = knob ? 1 : nr_node_ids; |
2857 | } | |
90bd6fd3 PH |
2858 | } |
2859 | mutex_unlock(&ksm_thread_mutex); | |
2860 | ||
2861 | return err ? err : count; | |
2862 | } | |
2863 | KSM_ATTR(merge_across_nodes); | |
2864 | #endif | |
2865 | ||
e86c59b1 CI |
2866 | static ssize_t use_zero_pages_show(struct kobject *kobj, |
2867 | struct kobj_attribute *attr, char *buf) | |
2868 | { | |
2869 | return sprintf(buf, "%u\n", ksm_use_zero_pages); | |
2870 | } | |
2871 | static ssize_t use_zero_pages_store(struct kobject *kobj, | |
2872 | struct kobj_attribute *attr, | |
2873 | const char *buf, size_t count) | |
2874 | { | |
2875 | int err; | |
2876 | bool value; | |
2877 | ||
2878 | err = kstrtobool(buf, &value); | |
2879 | if (err) | |
2880 | return -EINVAL; | |
2881 | ||
2882 | ksm_use_zero_pages = value; | |
2883 | ||
2884 | return count; | |
2885 | } | |
2886 | KSM_ATTR(use_zero_pages); | |
2887 | ||
2c653d0e AA |
2888 | static ssize_t max_page_sharing_show(struct kobject *kobj, |
2889 | struct kobj_attribute *attr, char *buf) | |
2890 | { | |
2891 | return sprintf(buf, "%u\n", ksm_max_page_sharing); | |
2892 | } | |
2893 | ||
2894 | static ssize_t max_page_sharing_store(struct kobject *kobj, | |
2895 | struct kobj_attribute *attr, | |
2896 | const char *buf, size_t count) | |
2897 | { | |
2898 | int err; | |
2899 | int knob; | |
2900 | ||
2901 | err = kstrtoint(buf, 10, &knob); | |
2902 | if (err) | |
2903 | return err; | |
2904 | /* | |
2905 | * When a KSM page is created it is shared by 2 mappings. This | |
2906 | * being a signed comparison, it implicitly verifies it's not | |
2907 | * negative. | |
2908 | */ | |
2909 | if (knob < 2) | |
2910 | return -EINVAL; | |
2911 | ||
2912 | if (READ_ONCE(ksm_max_page_sharing) == knob) | |
2913 | return count; | |
2914 | ||
2915 | mutex_lock(&ksm_thread_mutex); | |
2916 | wait_while_offlining(); | |
2917 | if (ksm_max_page_sharing != knob) { | |
2918 | if (ksm_pages_shared || remove_all_stable_nodes()) | |
2919 | err = -EBUSY; | |
2920 | else | |
2921 | ksm_max_page_sharing = knob; | |
2922 | } | |
2923 | mutex_unlock(&ksm_thread_mutex); | |
2924 | ||
2925 | return err ? err : count; | |
2926 | } | |
2927 | KSM_ATTR(max_page_sharing); | |
2928 | ||
b4028260 HD |
2929 | static ssize_t pages_shared_show(struct kobject *kobj, |
2930 | struct kobj_attribute *attr, char *buf) | |
2931 | { | |
2932 | return sprintf(buf, "%lu\n", ksm_pages_shared); | |
2933 | } | |
2934 | KSM_ATTR_RO(pages_shared); | |
2935 | ||
2936 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
2937 | struct kobj_attribute *attr, char *buf) | |
2938 | { | |
e178dfde | 2939 | return sprintf(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
2940 | } |
2941 | KSM_ATTR_RO(pages_sharing); | |
2942 | ||
473b0ce4 HD |
2943 | static ssize_t pages_unshared_show(struct kobject *kobj, |
2944 | struct kobj_attribute *attr, char *buf) | |
2945 | { | |
2946 | return sprintf(buf, "%lu\n", ksm_pages_unshared); | |
2947 | } | |
2948 | KSM_ATTR_RO(pages_unshared); | |
2949 | ||
2950 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
2951 | struct kobj_attribute *attr, char *buf) | |
2952 | { | |
2953 | long ksm_pages_volatile; | |
2954 | ||
2955 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
2956 | - ksm_pages_sharing - ksm_pages_unshared; | |
2957 | /* | |
2958 | * It was not worth any locking to calculate that statistic, | |
2959 | * but it might therefore sometimes be negative: conceal that. | |
2960 | */ | |
2961 | if (ksm_pages_volatile < 0) | |
2962 | ksm_pages_volatile = 0; | |
2963 | return sprintf(buf, "%ld\n", ksm_pages_volatile); | |
2964 | } | |
2965 | KSM_ATTR_RO(pages_volatile); | |
2966 | ||
2c653d0e AA |
2967 | static ssize_t stable_node_dups_show(struct kobject *kobj, |
2968 | struct kobj_attribute *attr, char *buf) | |
2969 | { | |
2970 | return sprintf(buf, "%lu\n", ksm_stable_node_dups); | |
2971 | } | |
2972 | KSM_ATTR_RO(stable_node_dups); | |
2973 | ||
2974 | static ssize_t stable_node_chains_show(struct kobject *kobj, | |
2975 | struct kobj_attribute *attr, char *buf) | |
2976 | { | |
2977 | return sprintf(buf, "%lu\n", ksm_stable_node_chains); | |
2978 | } | |
2979 | KSM_ATTR_RO(stable_node_chains); | |
2980 | ||
2981 | static ssize_t | |
2982 | stable_node_chains_prune_millisecs_show(struct kobject *kobj, | |
2983 | struct kobj_attribute *attr, | |
2984 | char *buf) | |
2985 | { | |
2986 | return sprintf(buf, "%u\n", ksm_stable_node_chains_prune_millisecs); | |
2987 | } | |
2988 | ||
2989 | static ssize_t | |
2990 | stable_node_chains_prune_millisecs_store(struct kobject *kobj, | |
2991 | struct kobj_attribute *attr, | |
2992 | const char *buf, size_t count) | |
2993 | { | |
2994 | unsigned long msecs; | |
2995 | int err; | |
2996 | ||
2997 | err = kstrtoul(buf, 10, &msecs); | |
2998 | if (err || msecs > UINT_MAX) | |
2999 | return -EINVAL; | |
3000 | ||
3001 | ksm_stable_node_chains_prune_millisecs = msecs; | |
3002 | ||
3003 | return count; | |
3004 | } | |
3005 | KSM_ATTR(stable_node_chains_prune_millisecs); | |
3006 | ||
473b0ce4 HD |
3007 | static ssize_t full_scans_show(struct kobject *kobj, |
3008 | struct kobj_attribute *attr, char *buf) | |
3009 | { | |
3010 | return sprintf(buf, "%lu\n", ksm_scan.seqnr); | |
3011 | } | |
3012 | KSM_ATTR_RO(full_scans); | |
3013 | ||
31dbd01f IE |
3014 | static struct attribute *ksm_attrs[] = { |
3015 | &sleep_millisecs_attr.attr, | |
3016 | &pages_to_scan_attr.attr, | |
3017 | &run_attr.attr, | |
b4028260 HD |
3018 | &pages_shared_attr.attr, |
3019 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
3020 | &pages_unshared_attr.attr, |
3021 | &pages_volatile_attr.attr, | |
3022 | &full_scans_attr.attr, | |
90bd6fd3 PH |
3023 | #ifdef CONFIG_NUMA |
3024 | &merge_across_nodes_attr.attr, | |
3025 | #endif | |
2c653d0e AA |
3026 | &max_page_sharing_attr.attr, |
3027 | &stable_node_chains_attr.attr, | |
3028 | &stable_node_dups_attr.attr, | |
3029 | &stable_node_chains_prune_millisecs_attr.attr, | |
e86c59b1 | 3030 | &use_zero_pages_attr.attr, |
31dbd01f IE |
3031 | NULL, |
3032 | }; | |
3033 | ||
3034 | static struct attribute_group ksm_attr_group = { | |
3035 | .attrs = ksm_attrs, | |
3036 | .name = "ksm", | |
3037 | }; | |
2ffd8679 | 3038 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
3039 | |
3040 | static int __init ksm_init(void) | |
3041 | { | |
3042 | struct task_struct *ksm_thread; | |
3043 | int err; | |
3044 | ||
e86c59b1 CI |
3045 | /* The correct value depends on page size and endianness */ |
3046 | zero_checksum = calc_checksum(ZERO_PAGE(0)); | |
3047 | /* Default to false for backwards compatibility */ | |
3048 | ksm_use_zero_pages = false; | |
3049 | ||
31dbd01f IE |
3050 | err = ksm_slab_init(); |
3051 | if (err) | |
3052 | goto out; | |
3053 | ||
31dbd01f IE |
3054 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
3055 | if (IS_ERR(ksm_thread)) { | |
25acde31 | 3056 | pr_err("ksm: creating kthread failed\n"); |
31dbd01f | 3057 | err = PTR_ERR(ksm_thread); |
d9f8984c | 3058 | goto out_free; |
31dbd01f IE |
3059 | } |
3060 | ||
2ffd8679 | 3061 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
3062 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
3063 | if (err) { | |
25acde31 | 3064 | pr_err("ksm: register sysfs failed\n"); |
2ffd8679 | 3065 | kthread_stop(ksm_thread); |
d9f8984c | 3066 | goto out_free; |
31dbd01f | 3067 | } |
c73602ad HD |
3068 | #else |
3069 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
3070 | ||
2ffd8679 | 3071 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 3072 | |
62b61f61 | 3073 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 | 3074 | /* There is no significance to this priority 100 */ |
62b61f61 HD |
3075 | hotplug_memory_notifier(ksm_memory_callback, 100); |
3076 | #endif | |
31dbd01f IE |
3077 | return 0; |
3078 | ||
d9f8984c | 3079 | out_free: |
31dbd01f IE |
3080 | ksm_slab_free(); |
3081 | out: | |
3082 | return err; | |
f8af4da3 | 3083 | } |
a64fb3cd | 3084 | subsys_initcall(ksm_init); |