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7a338472 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
f8af4da3 | 2 | /* |
31dbd01f IE |
3 | * Memory merging support. |
4 | * | |
5 | * This code enables dynamic sharing of identical pages found in different | |
6 | * memory areas, even if they are not shared by fork() | |
7 | * | |
36b2528d | 8 | * Copyright (C) 2008-2009 Red Hat, Inc. |
31dbd01f IE |
9 | * Authors: |
10 | * Izik Eidus | |
11 | * Andrea Arcangeli | |
12 | * Chris Wright | |
36b2528d | 13 | * Hugh Dickins |
f8af4da3 HD |
14 | */ |
15 | ||
16 | #include <linux/errno.h> | |
31dbd01f | 17 | #include <linux/mm.h> |
36090def | 18 | #include <linux/mm_inline.h> |
31dbd01f | 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> | |
59e1a2f4 | 28 | #include <linux/xxhash.h> |
31dbd01f IE |
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 | ||
5a2ca3ef MR |
54 | /** |
55 | * DOC: Overview | |
56 | * | |
31dbd01f IE |
57 | * A few notes about the KSM scanning process, |
58 | * to make it easier to understand the data structures below: | |
59 | * | |
60 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
61 | * contents into a data structure that holds pointers to the pages' locations. | |
62 | * | |
63 | * Since the contents of the pages may change at any moment, KSM cannot just | |
64 | * insert the pages into a normal sorted tree and expect it to find anything. | |
65 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
66 | * | |
67 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
68 | * by their contents. Because each such page is write-protected, searching on | |
69 | * this tree is fully assured to be working (except when pages are unmapped), | |
70 | * and therefore this tree is called the stable tree. | |
71 | * | |
5a2ca3ef MR |
72 | * The stable tree node includes information required for reverse |
73 | * mapping from a KSM page to virtual addresses that map this page. | |
74 | * | |
75 | * In order to avoid large latencies of the rmap walks on KSM pages, | |
76 | * KSM maintains two types of nodes in the stable tree: | |
77 | * | |
78 | * * the regular nodes that keep the reverse mapping structures in a | |
79 | * linked list | |
80 | * * the "chains" that link nodes ("dups") that represent the same | |
81 | * write protected memory content, but each "dup" corresponds to a | |
82 | * different KSM page copy of that content | |
83 | * | |
84 | * Internally, the regular nodes, "dups" and "chains" are represented | |
9303c9d5 | 85 | * using the same struct stable_node structure. |
5a2ca3ef | 86 | * |
31dbd01f IE |
87 | * In addition to the stable tree, KSM uses a second data structure called the |
88 | * unstable tree: this tree holds pointers to pages which have been found to | |
89 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
90 | * by their contents, but since they are not write-protected, KSM cannot rely | |
91 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
92 | * be corrupted as its contents are modified, and so it is called unstable. | |
93 | * | |
94 | * KSM solves this problem by several techniques: | |
95 | * | |
96 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
97 | * memory areas, and then the tree is rebuilt again from the beginning. | |
98 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
99 | * has not changed since the previous scan of all memory areas. | |
100 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
101 | * colors of the nodes and not on their contents, assuring that even when | |
102 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
103 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
104 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
105 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
106 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
107 | * it is secured in the stable tree. (When we scan a new page, we first | |
108 | * compare it against the stable tree, and then against the unstable tree.) | |
8fdb3dbf HD |
109 | * |
110 | * If the merge_across_nodes tunable is unset, then KSM maintains multiple | |
111 | * stable trees and multiple unstable trees: one of each for each NUMA node. | |
31dbd01f IE |
112 | */ |
113 | ||
114 | /** | |
115 | * struct mm_slot - ksm information per mm that is being scanned | |
116 | * @link: link to the mm_slots hash list | |
117 | * @mm_list: link into the mm_slots list, rooted in ksm_mm_head | |
6514d511 | 118 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f IE |
119 | * @mm: the mm that this information is valid for |
120 | */ | |
121 | struct mm_slot { | |
122 | struct hlist_node link; | |
123 | struct list_head mm_list; | |
6514d511 | 124 | struct rmap_item *rmap_list; |
31dbd01f IE |
125 | struct mm_struct *mm; |
126 | }; | |
127 | ||
128 | /** | |
129 | * struct ksm_scan - cursor for scanning | |
130 | * @mm_slot: the current mm_slot we are scanning | |
131 | * @address: the next address inside that to be scanned | |
6514d511 | 132 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
133 | * @seqnr: count of completed full scans (needed when removing unstable node) |
134 | * | |
135 | * There is only the one ksm_scan instance of this cursor structure. | |
136 | */ | |
137 | struct ksm_scan { | |
138 | struct mm_slot *mm_slot; | |
139 | unsigned long address; | |
6514d511 | 140 | struct rmap_item **rmap_list; |
31dbd01f IE |
141 | unsigned long seqnr; |
142 | }; | |
143 | ||
7b6ba2c7 HD |
144 | /** |
145 | * struct stable_node - node of the stable rbtree | |
146 | * @node: rb node of this ksm page in the stable tree | |
4146d2d6 | 147 | * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list |
2c653d0e | 148 | * @hlist_dup: linked into the stable_node->hlist with a stable_node chain |
4146d2d6 | 149 | * @list: linked into migrate_nodes, pending placement in the proper node tree |
7b6ba2c7 | 150 | * @hlist: hlist head of rmap_items using this ksm page |
4146d2d6 | 151 | * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid) |
2c653d0e AA |
152 | * @chain_prune_time: time of the last full garbage collection |
153 | * @rmap_hlist_len: number of rmap_item entries in hlist or STABLE_NODE_CHAIN | |
4146d2d6 | 154 | * @nid: NUMA node id of stable tree in which linked (may not match kpfn) |
7b6ba2c7 HD |
155 | */ |
156 | struct stable_node { | |
4146d2d6 HD |
157 | union { |
158 | struct rb_node node; /* when node of stable tree */ | |
159 | struct { /* when listed for migration */ | |
160 | struct list_head *head; | |
2c653d0e AA |
161 | struct { |
162 | struct hlist_node hlist_dup; | |
163 | struct list_head list; | |
164 | }; | |
4146d2d6 HD |
165 | }; |
166 | }; | |
7b6ba2c7 | 167 | struct hlist_head hlist; |
2c653d0e AA |
168 | union { |
169 | unsigned long kpfn; | |
170 | unsigned long chain_prune_time; | |
171 | }; | |
172 | /* | |
173 | * STABLE_NODE_CHAIN can be any negative number in | |
174 | * rmap_hlist_len negative range, but better not -1 to be able | |
175 | * to reliably detect underflows. | |
176 | */ | |
177 | #define STABLE_NODE_CHAIN -1024 | |
178 | int rmap_hlist_len; | |
4146d2d6 HD |
179 | #ifdef CONFIG_NUMA |
180 | int nid; | |
181 | #endif | |
7b6ba2c7 HD |
182 | }; |
183 | ||
31dbd01f IE |
184 | /** |
185 | * struct rmap_item - reverse mapping item for virtual addresses | |
6514d511 | 186 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
db114b83 | 187 | * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree |
bc56620b | 188 | * @nid: NUMA node id of unstable tree in which linked (may not match page) |
31dbd01f IE |
189 | * @mm: the memory structure this rmap_item is pointing into |
190 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
191 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
192 | * @node: rb node of this rmap_item in the unstable tree |
193 | * @head: pointer to stable_node heading this list in the stable tree | |
194 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f IE |
195 | */ |
196 | struct rmap_item { | |
6514d511 | 197 | struct rmap_item *rmap_list; |
bc56620b HD |
198 | union { |
199 | struct anon_vma *anon_vma; /* when stable */ | |
200 | #ifdef CONFIG_NUMA | |
201 | int nid; /* when node of unstable tree */ | |
202 | #endif | |
203 | }; | |
31dbd01f IE |
204 | struct mm_struct *mm; |
205 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 206 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 207 | union { |
7b6ba2c7 HD |
208 | struct rb_node node; /* when node of unstable tree */ |
209 | struct { /* when listed from stable tree */ | |
210 | struct stable_node *head; | |
211 | struct hlist_node hlist; | |
212 | }; | |
31dbd01f IE |
213 | }; |
214 | }; | |
215 | ||
216 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
217 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
218 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
219 | |
220 | /* The stable and unstable tree heads */ | |
ef53d16c HD |
221 | static struct rb_root one_stable_tree[1] = { RB_ROOT }; |
222 | static struct rb_root one_unstable_tree[1] = { RB_ROOT }; | |
223 | static struct rb_root *root_stable_tree = one_stable_tree; | |
224 | static struct rb_root *root_unstable_tree = one_unstable_tree; | |
31dbd01f | 225 | |
4146d2d6 HD |
226 | /* Recently migrated nodes of stable tree, pending proper placement */ |
227 | static LIST_HEAD(migrate_nodes); | |
2c653d0e | 228 | #define STABLE_NODE_DUP_HEAD ((struct list_head *)&migrate_nodes.prev) |
4146d2d6 | 229 | |
4ca3a69b SL |
230 | #define MM_SLOTS_HASH_BITS 10 |
231 | static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
31dbd01f IE |
232 | |
233 | static struct mm_slot ksm_mm_head = { | |
234 | .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list), | |
235 | }; | |
236 | static struct ksm_scan ksm_scan = { | |
237 | .mm_slot = &ksm_mm_head, | |
238 | }; | |
239 | ||
240 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 241 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
242 | static struct kmem_cache *mm_slot_cache; |
243 | ||
244 | /* The number of nodes in the stable tree */ | |
b4028260 | 245 | static unsigned long ksm_pages_shared; |
31dbd01f | 246 | |
e178dfde | 247 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 248 | static unsigned long ksm_pages_sharing; |
31dbd01f | 249 | |
473b0ce4 HD |
250 | /* The number of nodes in the unstable tree */ |
251 | static unsigned long ksm_pages_unshared; | |
252 | ||
253 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
254 | static unsigned long ksm_rmap_items; | |
255 | ||
2c653d0e AA |
256 | /* The number of stable_node chains */ |
257 | static unsigned long ksm_stable_node_chains; | |
258 | ||
259 | /* The number of stable_node dups linked to the stable_node chains */ | |
260 | static unsigned long ksm_stable_node_dups; | |
261 | ||
262 | /* Delay in pruning stale stable_node_dups in the stable_node_chains */ | |
584ff0df | 263 | static unsigned int ksm_stable_node_chains_prune_millisecs = 2000; |
2c653d0e AA |
264 | |
265 | /* Maximum number of page slots sharing a stable node */ | |
266 | static int ksm_max_page_sharing = 256; | |
267 | ||
31dbd01f | 268 | /* Number of pages ksmd should scan in one batch */ |
2c6854fd | 269 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
270 | |
271 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 272 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f | 273 | |
e86c59b1 CI |
274 | /* Checksum of an empty (zeroed) page */ |
275 | static unsigned int zero_checksum __read_mostly; | |
276 | ||
277 | /* Whether to merge empty (zeroed) pages with actual zero pages */ | |
278 | static bool ksm_use_zero_pages __read_mostly; | |
279 | ||
e850dcf5 | 280 | #ifdef CONFIG_NUMA |
90bd6fd3 PH |
281 | /* Zeroed when merging across nodes is not allowed */ |
282 | static unsigned int ksm_merge_across_nodes = 1; | |
ef53d16c | 283 | static int ksm_nr_node_ids = 1; |
e850dcf5 HD |
284 | #else |
285 | #define ksm_merge_across_nodes 1U | |
ef53d16c | 286 | #define ksm_nr_node_ids 1 |
e850dcf5 | 287 | #endif |
90bd6fd3 | 288 | |
31dbd01f IE |
289 | #define KSM_RUN_STOP 0 |
290 | #define KSM_RUN_MERGE 1 | |
291 | #define KSM_RUN_UNMERGE 2 | |
ef4d43a8 HD |
292 | #define KSM_RUN_OFFLINE 4 |
293 | static unsigned long ksm_run = KSM_RUN_STOP; | |
294 | static void wait_while_offlining(void); | |
31dbd01f IE |
295 | |
296 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
fcf9a0ef | 297 | static DECLARE_WAIT_QUEUE_HEAD(ksm_iter_wait); |
31dbd01f IE |
298 | static DEFINE_MUTEX(ksm_thread_mutex); |
299 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
300 | ||
301 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\ | |
302 | sizeof(struct __struct), __alignof__(struct __struct),\ | |
303 | (__flags), NULL) | |
304 | ||
305 | static int __init ksm_slab_init(void) | |
306 | { | |
307 | rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0); | |
308 | if (!rmap_item_cache) | |
309 | goto out; | |
310 | ||
7b6ba2c7 HD |
311 | stable_node_cache = KSM_KMEM_CACHE(stable_node, 0); |
312 | if (!stable_node_cache) | |
313 | goto out_free1; | |
314 | ||
31dbd01f IE |
315 | mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0); |
316 | if (!mm_slot_cache) | |
7b6ba2c7 | 317 | goto out_free2; |
31dbd01f IE |
318 | |
319 | return 0; | |
320 | ||
7b6ba2c7 HD |
321 | out_free2: |
322 | kmem_cache_destroy(stable_node_cache); | |
323 | out_free1: | |
31dbd01f IE |
324 | kmem_cache_destroy(rmap_item_cache); |
325 | out: | |
326 | return -ENOMEM; | |
327 | } | |
328 | ||
329 | static void __init ksm_slab_free(void) | |
330 | { | |
331 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 332 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
333 | kmem_cache_destroy(rmap_item_cache); |
334 | mm_slot_cache = NULL; | |
335 | } | |
336 | ||
2c653d0e AA |
337 | static __always_inline bool is_stable_node_chain(struct stable_node *chain) |
338 | { | |
339 | return chain->rmap_hlist_len == STABLE_NODE_CHAIN; | |
340 | } | |
341 | ||
342 | static __always_inline bool is_stable_node_dup(struct stable_node *dup) | |
343 | { | |
344 | return dup->head == STABLE_NODE_DUP_HEAD; | |
345 | } | |
346 | ||
347 | static inline void stable_node_chain_add_dup(struct stable_node *dup, | |
348 | struct stable_node *chain) | |
349 | { | |
350 | VM_BUG_ON(is_stable_node_dup(dup)); | |
351 | dup->head = STABLE_NODE_DUP_HEAD; | |
352 | VM_BUG_ON(!is_stable_node_chain(chain)); | |
353 | hlist_add_head(&dup->hlist_dup, &chain->hlist); | |
354 | ksm_stable_node_dups++; | |
355 | } | |
356 | ||
357 | static inline void __stable_node_dup_del(struct stable_node *dup) | |
358 | { | |
b4fecc67 | 359 | VM_BUG_ON(!is_stable_node_dup(dup)); |
2c653d0e AA |
360 | hlist_del(&dup->hlist_dup); |
361 | ksm_stable_node_dups--; | |
362 | } | |
363 | ||
364 | static inline void stable_node_dup_del(struct stable_node *dup) | |
365 | { | |
366 | VM_BUG_ON(is_stable_node_chain(dup)); | |
367 | if (is_stable_node_dup(dup)) | |
368 | __stable_node_dup_del(dup); | |
369 | else | |
370 | rb_erase(&dup->node, root_stable_tree + NUMA(dup->nid)); | |
371 | #ifdef CONFIG_DEBUG_VM | |
372 | dup->head = NULL; | |
373 | #endif | |
374 | } | |
375 | ||
31dbd01f IE |
376 | static inline struct rmap_item *alloc_rmap_item(void) |
377 | { | |
473b0ce4 HD |
378 | struct rmap_item *rmap_item; |
379 | ||
5b398e41 | 380 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | |
381 | __GFP_NORETRY | __GFP_NOWARN); | |
473b0ce4 HD |
382 | if (rmap_item) |
383 | ksm_rmap_items++; | |
384 | return rmap_item; | |
31dbd01f IE |
385 | } |
386 | ||
387 | static inline void free_rmap_item(struct rmap_item *rmap_item) | |
388 | { | |
473b0ce4 | 389 | ksm_rmap_items--; |
31dbd01f IE |
390 | rmap_item->mm = NULL; /* debug safety */ |
391 | kmem_cache_free(rmap_item_cache, rmap_item); | |
392 | } | |
393 | ||
7b6ba2c7 HD |
394 | static inline struct stable_node *alloc_stable_node(void) |
395 | { | |
6213055f | 396 | /* |
397 | * The allocation can take too long with GFP_KERNEL when memory is under | |
398 | * pressure, which may lead to hung task warnings. Adding __GFP_HIGH | |
399 | * grants access to memory reserves, helping to avoid this problem. | |
400 | */ | |
401 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL | __GFP_HIGH); | |
7b6ba2c7 HD |
402 | } |
403 | ||
404 | static inline void free_stable_node(struct stable_node *stable_node) | |
405 | { | |
2c653d0e AA |
406 | VM_BUG_ON(stable_node->rmap_hlist_len && |
407 | !is_stable_node_chain(stable_node)); | |
7b6ba2c7 HD |
408 | kmem_cache_free(stable_node_cache, stable_node); |
409 | } | |
410 | ||
31dbd01f IE |
411 | static inline struct mm_slot *alloc_mm_slot(void) |
412 | { | |
413 | if (!mm_slot_cache) /* initialization failed */ | |
414 | return NULL; | |
415 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
416 | } | |
417 | ||
418 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
419 | { | |
420 | kmem_cache_free(mm_slot_cache, mm_slot); | |
421 | } | |
422 | ||
31dbd01f IE |
423 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
424 | { | |
4ca3a69b SL |
425 | struct mm_slot *slot; |
426 | ||
b67bfe0d | 427 | hash_for_each_possible(mm_slots_hash, slot, link, (unsigned long)mm) |
4ca3a69b SL |
428 | if (slot->mm == mm) |
429 | return slot; | |
31dbd01f | 430 | |
31dbd01f IE |
431 | return NULL; |
432 | } | |
433 | ||
434 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
435 | struct mm_slot *mm_slot) | |
436 | { | |
31dbd01f | 437 | mm_slot->mm = mm; |
4ca3a69b | 438 | hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm); |
31dbd01f IE |
439 | } |
440 | ||
a913e182 HD |
441 | /* |
442 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
443 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
c1e8d7c6 | 444 | * takes mmap_lock briefly to serialize against them. ksm_exit() does not set |
a913e182 HD |
445 | * a special flag: they can just back out as soon as mm_users goes to zero. |
446 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
447 | * places for correctness, in some places just to avoid unnecessary work. | |
448 | */ | |
449 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
450 | { | |
451 | return atomic_read(&mm->mm_users) == 0; | |
452 | } | |
453 | ||
31dbd01f IE |
454 | /* |
455 | * We use break_ksm to break COW on a ksm page: it's a stripped down | |
456 | * | |
7a9547fd | 457 | * if (get_user_pages(addr, 1, FOLL_WRITE, &page, NULL) == 1) |
31dbd01f IE |
458 | * put_page(page); |
459 | * | |
460 | * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma, | |
461 | * in case the application has unmapped and remapped mm,addr meanwhile. | |
462 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
bbcd53c9 | 463 | * mmap of /dev/mem, where we would not want to touch it. |
1b2ee126 DH |
464 | * |
465 | * FAULT_FLAG/FOLL_REMOTE are because we do this outside the context | |
466 | * of the process that owns 'vma'. We also do not want to enforce | |
467 | * protection keys here anyway. | |
31dbd01f | 468 | */ |
d952b791 | 469 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f IE |
470 | { |
471 | struct page *page; | |
50a7ca3c | 472 | vm_fault_t ret = 0; |
31dbd01f IE |
473 | |
474 | do { | |
475 | cond_resched(); | |
1b2ee126 DH |
476 | page = follow_page(vma, addr, |
477 | FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE); | |
3218f871 | 478 | if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) |
31dbd01f IE |
479 | break; |
480 | if (PageKsm(page)) | |
dcddffd4 | 481 | ret = handle_mm_fault(vma, addr, |
bce617ed PX |
482 | FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE, |
483 | NULL); | |
31dbd01f IE |
484 | else |
485 | ret = VM_FAULT_WRITE; | |
486 | put_page(page); | |
33692f27 | 487 | } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM))); |
d952b791 HD |
488 | /* |
489 | * We must loop because handle_mm_fault() may back out if there's | |
490 | * any difficulty e.g. if pte accessed bit gets updated concurrently. | |
491 | * | |
492 | * VM_FAULT_WRITE is what we have been hoping for: it indicates that | |
493 | * COW has been broken, even if the vma does not permit VM_WRITE; | |
494 | * but note that a concurrent fault might break PageKsm for us. | |
495 | * | |
496 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
497 | * backing file, which also invalidates anonymous pages: that's | |
498 | * okay, that truncation will have unmapped the PageKsm for us. | |
499 | * | |
500 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
501 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
502 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
503 | * to user; and ksmd, having no mm, would never be chosen for that. | |
504 | * | |
505 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
506 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
507 | * even ksmd can fail in this way - though it's usually breaking ksm | |
508 | * just to undo a merge it made a moment before, so unlikely to oom. | |
509 | * | |
510 | * That's a pity: we might therefore have more kernel pages allocated | |
511 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
512 | * will retry to break_cow on each pass, so should recover the page | |
513 | * in due course. The important thing is to not let VM_MERGEABLE | |
514 | * be cleared while any such pages might remain in the area. | |
515 | */ | |
516 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
517 | } |
518 | ||
ef694222 BL |
519 | static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, |
520 | unsigned long addr) | |
521 | { | |
522 | struct vm_area_struct *vma; | |
523 | if (ksm_test_exit(mm)) | |
524 | return NULL; | |
ff69fb81 LH |
525 | vma = vma_lookup(mm, addr); |
526 | if (!vma || !(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
ef694222 BL |
527 | return NULL; |
528 | return vma; | |
529 | } | |
530 | ||
8dd3557a | 531 | static void break_cow(struct rmap_item *rmap_item) |
31dbd01f | 532 | { |
8dd3557a HD |
533 | struct mm_struct *mm = rmap_item->mm; |
534 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
535 | struct vm_area_struct *vma; |
536 | ||
4035c07a HD |
537 | /* |
538 | * It is not an accident that whenever we want to break COW | |
539 | * to undo, we also need to drop a reference to the anon_vma. | |
540 | */ | |
9e60109f | 541 | put_anon_vma(rmap_item->anon_vma); |
4035c07a | 542 | |
d8ed45c5 | 543 | mmap_read_lock(mm); |
ef694222 BL |
544 | vma = find_mergeable_vma(mm, addr); |
545 | if (vma) | |
546 | break_ksm(vma, addr); | |
d8ed45c5 | 547 | mmap_read_unlock(mm); |
31dbd01f IE |
548 | } |
549 | ||
550 | static struct page *get_mergeable_page(struct rmap_item *rmap_item) | |
551 | { | |
552 | struct mm_struct *mm = rmap_item->mm; | |
553 | unsigned long addr = rmap_item->address; | |
554 | struct vm_area_struct *vma; | |
555 | struct page *page; | |
556 | ||
d8ed45c5 | 557 | mmap_read_lock(mm); |
ef694222 BL |
558 | vma = find_mergeable_vma(mm, addr); |
559 | if (!vma) | |
31dbd01f IE |
560 | goto out; |
561 | ||
562 | page = follow_page(vma, addr, FOLL_GET); | |
3218f871 | 563 | if (IS_ERR_OR_NULL(page) || is_zone_device_page(page)) |
31dbd01f | 564 | goto out; |
f765f540 | 565 | if (PageAnon(page)) { |
31dbd01f IE |
566 | flush_anon_page(vma, page, addr); |
567 | flush_dcache_page(page); | |
568 | } else { | |
569 | put_page(page); | |
c8f95ed1 AA |
570 | out: |
571 | page = NULL; | |
31dbd01f | 572 | } |
d8ed45c5 | 573 | mmap_read_unlock(mm); |
31dbd01f IE |
574 | return page; |
575 | } | |
576 | ||
90bd6fd3 PH |
577 | /* |
578 | * This helper is used for getting right index into array of tree roots. | |
579 | * When merge_across_nodes knob is set to 1, there are only two rb-trees for | |
580 | * stable and unstable pages from all nodes with roots in index 0. Otherwise, | |
581 | * every node has its own stable and unstable tree. | |
582 | */ | |
583 | static inline int get_kpfn_nid(unsigned long kpfn) | |
584 | { | |
d8fc16a8 | 585 | return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn)); |
90bd6fd3 PH |
586 | } |
587 | ||
2c653d0e AA |
588 | static struct stable_node *alloc_stable_node_chain(struct stable_node *dup, |
589 | struct rb_root *root) | |
590 | { | |
591 | struct stable_node *chain = alloc_stable_node(); | |
592 | VM_BUG_ON(is_stable_node_chain(dup)); | |
593 | if (likely(chain)) { | |
594 | INIT_HLIST_HEAD(&chain->hlist); | |
595 | chain->chain_prune_time = jiffies; | |
596 | chain->rmap_hlist_len = STABLE_NODE_CHAIN; | |
597 | #if defined (CONFIG_DEBUG_VM) && defined(CONFIG_NUMA) | |
98fa15f3 | 598 | chain->nid = NUMA_NO_NODE; /* debug */ |
2c653d0e AA |
599 | #endif |
600 | ksm_stable_node_chains++; | |
601 | ||
602 | /* | |
603 | * Put the stable node chain in the first dimension of | |
604 | * the stable tree and at the same time remove the old | |
605 | * stable node. | |
606 | */ | |
607 | rb_replace_node(&dup->node, &chain->node, root); | |
608 | ||
609 | /* | |
610 | * Move the old stable node to the second dimension | |
611 | * queued in the hlist_dup. The invariant is that all | |
612 | * dup stable_nodes in the chain->hlist point to pages | |
457aef94 | 613 | * that are write protected and have the exact same |
2c653d0e AA |
614 | * content. |
615 | */ | |
616 | stable_node_chain_add_dup(dup, chain); | |
617 | } | |
618 | return chain; | |
619 | } | |
620 | ||
621 | static inline void free_stable_node_chain(struct stable_node *chain, | |
622 | struct rb_root *root) | |
623 | { | |
624 | rb_erase(&chain->node, root); | |
625 | free_stable_node(chain); | |
626 | ksm_stable_node_chains--; | |
627 | } | |
628 | ||
4035c07a HD |
629 | static void remove_node_from_stable_tree(struct stable_node *stable_node) |
630 | { | |
631 | struct rmap_item *rmap_item; | |
4035c07a | 632 | |
2c653d0e AA |
633 | /* check it's not STABLE_NODE_CHAIN or negative */ |
634 | BUG_ON(stable_node->rmap_hlist_len < 0); | |
635 | ||
b67bfe0d | 636 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
4035c07a HD |
637 | if (rmap_item->hlist.next) |
638 | ksm_pages_sharing--; | |
639 | else | |
640 | ksm_pages_shared--; | |
76093853 | 641 | |
642 | rmap_item->mm->ksm_merging_pages--; | |
643 | ||
2c653d0e AA |
644 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
645 | stable_node->rmap_hlist_len--; | |
9e60109f | 646 | put_anon_vma(rmap_item->anon_vma); |
4035c07a HD |
647 | rmap_item->address &= PAGE_MASK; |
648 | cond_resched(); | |
649 | } | |
650 | ||
2c653d0e AA |
651 | /* |
652 | * We need the second aligned pointer of the migrate_nodes | |
653 | * list_head to stay clear from the rb_parent_color union | |
654 | * (aligned and different than any node) and also different | |
655 | * from &migrate_nodes. This will verify that future list.h changes | |
815f0ddb | 656 | * don't break STABLE_NODE_DUP_HEAD. Only recent gcc can handle it. |
2c653d0e | 657 | */ |
2c653d0e AA |
658 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD <= &migrate_nodes); |
659 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1); | |
2c653d0e | 660 | |
4146d2d6 HD |
661 | if (stable_node->head == &migrate_nodes) |
662 | list_del(&stable_node->list); | |
663 | else | |
2c653d0e | 664 | stable_node_dup_del(stable_node); |
4035c07a HD |
665 | free_stable_node(stable_node); |
666 | } | |
667 | ||
2cee57d1 YS |
668 | enum get_ksm_page_flags { |
669 | GET_KSM_PAGE_NOLOCK, | |
670 | GET_KSM_PAGE_LOCK, | |
671 | GET_KSM_PAGE_TRYLOCK | |
672 | }; | |
673 | ||
4035c07a HD |
674 | /* |
675 | * get_ksm_page: checks if the page indicated by the stable node | |
676 | * is still its ksm page, despite having held no reference to it. | |
677 | * In which case we can trust the content of the page, and it | |
678 | * returns the gotten page; but if the page has now been zapped, | |
679 | * remove the stale node from the stable tree and return NULL. | |
c8d6553b | 680 | * But beware, the stable node's page might be being migrated. |
4035c07a HD |
681 | * |
682 | * You would expect the stable_node to hold a reference to the ksm page. | |
683 | * But if it increments the page's count, swapping out has to wait for | |
684 | * ksmd to come around again before it can free the page, which may take | |
685 | * seconds or even minutes: much too unresponsive. So instead we use a | |
686 | * "keyhole reference": access to the ksm page from the stable node peeps | |
687 | * out through its keyhole to see if that page still holds the right key, | |
688 | * pointing back to this stable node. This relies on freeing a PageAnon | |
689 | * page to reset its page->mapping to NULL, and relies on no other use of | |
690 | * a page to put something that might look like our key in page->mapping. | |
4035c07a HD |
691 | * is on its way to being freed; but it is an anomaly to bear in mind. |
692 | */ | |
2cee57d1 YS |
693 | static struct page *get_ksm_page(struct stable_node *stable_node, |
694 | enum get_ksm_page_flags flags) | |
4035c07a HD |
695 | { |
696 | struct page *page; | |
697 | void *expected_mapping; | |
c8d6553b | 698 | unsigned long kpfn; |
4035c07a | 699 | |
bda807d4 MK |
700 | expected_mapping = (void *)((unsigned long)stable_node | |
701 | PAGE_MAPPING_KSM); | |
c8d6553b | 702 | again: |
08df4774 | 703 | kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */ |
c8d6553b | 704 | page = pfn_to_page(kpfn); |
4db0c3c2 | 705 | if (READ_ONCE(page->mapping) != expected_mapping) |
4035c07a | 706 | goto stale; |
c8d6553b HD |
707 | |
708 | /* | |
709 | * We cannot do anything with the page while its refcount is 0. | |
710 | * Usually 0 means free, or tail of a higher-order page: in which | |
711 | * case this node is no longer referenced, and should be freed; | |
1c4c3b99 | 712 | * however, it might mean that the page is under page_ref_freeze(). |
c8d6553b | 713 | * The __remove_mapping() case is easy, again the node is now stale; |
52d1e606 | 714 | * the same is in reuse_ksm_page() case; but if page is swapcache |
9800562f | 715 | * in folio_migrate_mapping(), it might still be our page, |
52d1e606 | 716 | * in which case it's essential to keep the node. |
c8d6553b HD |
717 | */ |
718 | while (!get_page_unless_zero(page)) { | |
719 | /* | |
720 | * Another check for page->mapping != expected_mapping would | |
721 | * work here too. We have chosen the !PageSwapCache test to | |
722 | * optimize the common case, when the page is or is about to | |
723 | * be freed: PageSwapCache is cleared (under spin_lock_irq) | |
1c4c3b99 | 724 | * in the ref_freeze section of __remove_mapping(); but Anon |
c8d6553b HD |
725 | * page->mapping reset to NULL later, in free_pages_prepare(). |
726 | */ | |
727 | if (!PageSwapCache(page)) | |
728 | goto stale; | |
729 | cpu_relax(); | |
730 | } | |
731 | ||
4db0c3c2 | 732 | if (READ_ONCE(page->mapping) != expected_mapping) { |
4035c07a HD |
733 | put_page(page); |
734 | goto stale; | |
735 | } | |
c8d6553b | 736 | |
2cee57d1 YS |
737 | if (flags == GET_KSM_PAGE_TRYLOCK) { |
738 | if (!trylock_page(page)) { | |
739 | put_page(page); | |
740 | return ERR_PTR(-EBUSY); | |
741 | } | |
742 | } else if (flags == GET_KSM_PAGE_LOCK) | |
8aafa6a4 | 743 | lock_page(page); |
2cee57d1 YS |
744 | |
745 | if (flags != GET_KSM_PAGE_NOLOCK) { | |
4db0c3c2 | 746 | if (READ_ONCE(page->mapping) != expected_mapping) { |
8aafa6a4 HD |
747 | unlock_page(page); |
748 | put_page(page); | |
749 | goto stale; | |
750 | } | |
751 | } | |
4035c07a | 752 | return page; |
c8d6553b | 753 | |
4035c07a | 754 | stale: |
c8d6553b HD |
755 | /* |
756 | * We come here from above when page->mapping or !PageSwapCache | |
757 | * suggests that the node is stale; but it might be under migration. | |
19138349 | 758 | * We need smp_rmb(), matching the smp_wmb() in folio_migrate_ksm(), |
c8d6553b HD |
759 | * before checking whether node->kpfn has been changed. |
760 | */ | |
761 | smp_rmb(); | |
4db0c3c2 | 762 | if (READ_ONCE(stable_node->kpfn) != kpfn) |
c8d6553b | 763 | goto again; |
4035c07a HD |
764 | remove_node_from_stable_tree(stable_node); |
765 | return NULL; | |
766 | } | |
767 | ||
31dbd01f IE |
768 | /* |
769 | * Removing rmap_item from stable or unstable tree. | |
770 | * This function will clean the information from the stable/unstable tree. | |
771 | */ | |
772 | static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) | |
773 | { | |
7b6ba2c7 HD |
774 | if (rmap_item->address & STABLE_FLAG) { |
775 | struct stable_node *stable_node; | |
5ad64688 | 776 | struct page *page; |
31dbd01f | 777 | |
7b6ba2c7 | 778 | stable_node = rmap_item->head; |
62862290 | 779 | page = get_ksm_page(stable_node, GET_KSM_PAGE_LOCK); |
4035c07a HD |
780 | if (!page) |
781 | goto out; | |
5ad64688 | 782 | |
7b6ba2c7 | 783 | hlist_del(&rmap_item->hlist); |
62862290 | 784 | unlock_page(page); |
4035c07a | 785 | put_page(page); |
08beca44 | 786 | |
98666f8a | 787 | if (!hlist_empty(&stable_node->hlist)) |
4035c07a HD |
788 | ksm_pages_sharing--; |
789 | else | |
7b6ba2c7 | 790 | ksm_pages_shared--; |
76093853 | 791 | |
792 | rmap_item->mm->ksm_merging_pages--; | |
793 | ||
2c653d0e AA |
794 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
795 | stable_node->rmap_hlist_len--; | |
31dbd01f | 796 | |
9e60109f | 797 | put_anon_vma(rmap_item->anon_vma); |
c89a384e | 798 | rmap_item->head = NULL; |
93d17715 | 799 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 800 | |
7b6ba2c7 | 801 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
802 | unsigned char age; |
803 | /* | |
9ba69294 | 804 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 805 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
806 | * But be careful when an mm is exiting: do the rb_erase |
807 | * if this rmap_item was inserted by this scan, rather | |
808 | * than left over from before. | |
31dbd01f IE |
809 | */ |
810 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 811 | BUG_ON(age > 1); |
31dbd01f | 812 | if (!age) |
90bd6fd3 | 813 | rb_erase(&rmap_item->node, |
ef53d16c | 814 | root_unstable_tree + NUMA(rmap_item->nid)); |
473b0ce4 | 815 | ksm_pages_unshared--; |
93d17715 | 816 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 817 | } |
4035c07a | 818 | out: |
31dbd01f IE |
819 | cond_resched(); /* we're called from many long loops */ |
820 | } | |
821 | ||
420be4ed | 822 | static void remove_trailing_rmap_items(struct rmap_item **rmap_list) |
31dbd01f | 823 | { |
6514d511 HD |
824 | while (*rmap_list) { |
825 | struct rmap_item *rmap_item = *rmap_list; | |
826 | *rmap_list = rmap_item->rmap_list; | |
31dbd01f | 827 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
828 | free_rmap_item(rmap_item); |
829 | } | |
830 | } | |
831 | ||
832 | /* | |
e850dcf5 | 833 | * Though it's very tempting to unmerge rmap_items from stable tree rather |
31dbd01f IE |
834 | * than check every pte of a given vma, the locking doesn't quite work for |
835 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
c1e8d7c6 | 836 | * page and upping mmap_lock. Nor does it fit with the way we skip dup'ing |
31dbd01f IE |
837 | * rmap_items from parent to child at fork time (so as not to waste time |
838 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
839 | * |
840 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
841 | * and freeing memory) when unmerging an area, it's easier to leave that | |
842 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
843 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 844 | */ |
d952b791 HD |
845 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
846 | unsigned long start, unsigned long end) | |
31dbd01f IE |
847 | { |
848 | unsigned long addr; | |
d952b791 | 849 | int err = 0; |
31dbd01f | 850 | |
d952b791 | 851 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
852 | if (ksm_test_exit(vma->vm_mm)) |
853 | break; | |
d952b791 HD |
854 | if (signal_pending(current)) |
855 | err = -ERESTARTSYS; | |
856 | else | |
857 | err = break_ksm(vma, addr); | |
858 | } | |
859 | return err; | |
31dbd01f IE |
860 | } |
861 | ||
19138349 MWO |
862 | static inline struct stable_node *folio_stable_node(struct folio *folio) |
863 | { | |
864 | return folio_test_ksm(folio) ? folio_raw_mapping(folio) : NULL; | |
865 | } | |
866 | ||
88484826 MR |
867 | static inline struct stable_node *page_stable_node(struct page *page) |
868 | { | |
19138349 | 869 | return folio_stable_node(page_folio(page)); |
88484826 MR |
870 | } |
871 | ||
872 | static inline void set_page_stable_node(struct page *page, | |
873 | struct stable_node *stable_node) | |
874 | { | |
6c287605 | 875 | VM_BUG_ON_PAGE(PageAnon(page) && PageAnonExclusive(page), page); |
88484826 MR |
876 | page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM); |
877 | } | |
878 | ||
2ffd8679 HD |
879 | #ifdef CONFIG_SYSFS |
880 | /* | |
881 | * Only called through the sysfs control interface: | |
882 | */ | |
cbf86cfe HD |
883 | static int remove_stable_node(struct stable_node *stable_node) |
884 | { | |
885 | struct page *page; | |
886 | int err; | |
887 | ||
2cee57d1 | 888 | page = get_ksm_page(stable_node, GET_KSM_PAGE_LOCK); |
cbf86cfe HD |
889 | if (!page) { |
890 | /* | |
891 | * get_ksm_page did remove_node_from_stable_tree itself. | |
892 | */ | |
893 | return 0; | |
894 | } | |
895 | ||
9a63236f AR |
896 | /* |
897 | * Page could be still mapped if this races with __mmput() running in | |
898 | * between ksm_exit() and exit_mmap(). Just refuse to let | |
899 | * merge_across_nodes/max_page_sharing be switched. | |
900 | */ | |
901 | err = -EBUSY; | |
902 | if (!page_mapped(page)) { | |
cbf86cfe | 903 | /* |
8fdb3dbf HD |
904 | * The stable node did not yet appear stale to get_ksm_page(), |
905 | * since that allows for an unmapped ksm page to be recognized | |
906 | * right up until it is freed; but the node is safe to remove. | |
cbf86cfe HD |
907 | * This page might be in a pagevec waiting to be freed, |
908 | * or it might be PageSwapCache (perhaps under writeback), | |
909 | * or it might have been removed from swapcache a moment ago. | |
910 | */ | |
911 | set_page_stable_node(page, NULL); | |
912 | remove_node_from_stable_tree(stable_node); | |
913 | err = 0; | |
914 | } | |
915 | ||
916 | unlock_page(page); | |
917 | put_page(page); | |
918 | return err; | |
919 | } | |
920 | ||
2c653d0e AA |
921 | static int remove_stable_node_chain(struct stable_node *stable_node, |
922 | struct rb_root *root) | |
923 | { | |
924 | struct stable_node *dup; | |
925 | struct hlist_node *hlist_safe; | |
926 | ||
927 | if (!is_stable_node_chain(stable_node)) { | |
928 | VM_BUG_ON(is_stable_node_dup(stable_node)); | |
929 | if (remove_stable_node(stable_node)) | |
930 | return true; | |
931 | else | |
932 | return false; | |
933 | } | |
934 | ||
935 | hlist_for_each_entry_safe(dup, hlist_safe, | |
936 | &stable_node->hlist, hlist_dup) { | |
937 | VM_BUG_ON(!is_stable_node_dup(dup)); | |
938 | if (remove_stable_node(dup)) | |
939 | return true; | |
940 | } | |
941 | BUG_ON(!hlist_empty(&stable_node->hlist)); | |
942 | free_stable_node_chain(stable_node, root); | |
943 | return false; | |
944 | } | |
945 | ||
cbf86cfe HD |
946 | static int remove_all_stable_nodes(void) |
947 | { | |
03640418 | 948 | struct stable_node *stable_node, *next; |
cbf86cfe HD |
949 | int nid; |
950 | int err = 0; | |
951 | ||
ef53d16c | 952 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
cbf86cfe HD |
953 | while (root_stable_tree[nid].rb_node) { |
954 | stable_node = rb_entry(root_stable_tree[nid].rb_node, | |
955 | struct stable_node, node); | |
2c653d0e AA |
956 | if (remove_stable_node_chain(stable_node, |
957 | root_stable_tree + nid)) { | |
cbf86cfe HD |
958 | err = -EBUSY; |
959 | break; /* proceed to next nid */ | |
960 | } | |
961 | cond_resched(); | |
962 | } | |
963 | } | |
03640418 | 964 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
965 | if (remove_stable_node(stable_node)) |
966 | err = -EBUSY; | |
967 | cond_resched(); | |
968 | } | |
cbf86cfe HD |
969 | return err; |
970 | } | |
971 | ||
d952b791 | 972 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f IE |
973 | { |
974 | struct mm_slot *mm_slot; | |
975 | struct mm_struct *mm; | |
976 | struct vm_area_struct *vma; | |
d952b791 HD |
977 | int err = 0; |
978 | ||
979 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 980 | ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next, |
d952b791 HD |
981 | struct mm_slot, mm_list); |
982 | spin_unlock(&ksm_mmlist_lock); | |
31dbd01f | 983 | |
9ba69294 HD |
984 | for (mm_slot = ksm_scan.mm_slot; |
985 | mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) { | |
31dbd01f | 986 | mm = mm_slot->mm; |
d8ed45c5 | 987 | mmap_read_lock(mm); |
31dbd01f | 988 | for (vma = mm->mmap; vma; vma = vma->vm_next) { |
9ba69294 HD |
989 | if (ksm_test_exit(mm)) |
990 | break; | |
31dbd01f IE |
991 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
992 | continue; | |
d952b791 HD |
993 | err = unmerge_ksm_pages(vma, |
994 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
995 | if (err) |
996 | goto error; | |
31dbd01f | 997 | } |
9ba69294 | 998 | |
420be4ed | 999 | remove_trailing_rmap_items(&mm_slot->rmap_list); |
d8ed45c5 | 1000 | mmap_read_unlock(mm); |
d952b791 HD |
1001 | |
1002 | spin_lock(&ksm_mmlist_lock); | |
9ba69294 | 1003 | ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next, |
d952b791 | 1004 | struct mm_slot, mm_list); |
9ba69294 | 1005 | if (ksm_test_exit(mm)) { |
4ca3a69b | 1006 | hash_del(&mm_slot->link); |
9ba69294 HD |
1007 | list_del(&mm_slot->mm_list); |
1008 | spin_unlock(&ksm_mmlist_lock); | |
1009 | ||
1010 | free_mm_slot(mm_slot); | |
1011 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
9ba69294 | 1012 | mmdrop(mm); |
7496fea9 | 1013 | } else |
9ba69294 | 1014 | spin_unlock(&ksm_mmlist_lock); |
31dbd01f IE |
1015 | } |
1016 | ||
cbf86cfe HD |
1017 | /* Clean up stable nodes, but don't worry if some are still busy */ |
1018 | remove_all_stable_nodes(); | |
d952b791 | 1019 | ksm_scan.seqnr = 0; |
9ba69294 HD |
1020 | return 0; |
1021 | ||
1022 | error: | |
d8ed45c5 | 1023 | mmap_read_unlock(mm); |
31dbd01f | 1024 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 1025 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 1026 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 1027 | return err; |
31dbd01f | 1028 | } |
2ffd8679 | 1029 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 1030 | |
31dbd01f IE |
1031 | static u32 calc_checksum(struct page *page) |
1032 | { | |
1033 | u32 checksum; | |
9b04c5fe | 1034 | void *addr = kmap_atomic(page); |
59e1a2f4 | 1035 | checksum = xxhash(addr, PAGE_SIZE, 0); |
9b04c5fe | 1036 | kunmap_atomic(addr); |
31dbd01f IE |
1037 | return checksum; |
1038 | } | |
1039 | ||
31dbd01f IE |
1040 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, |
1041 | pte_t *orig_pte) | |
1042 | { | |
1043 | struct mm_struct *mm = vma->vm_mm; | |
eed05e54 | 1044 | DEFINE_PAGE_VMA_WALK(pvmw, page, vma, 0, 0); |
31dbd01f IE |
1045 | int swapped; |
1046 | int err = -EFAULT; | |
ac46d4f3 | 1047 | struct mmu_notifier_range range; |
6c287605 | 1048 | bool anon_exclusive; |
31dbd01f | 1049 | |
36eaff33 KS |
1050 | pvmw.address = page_address_in_vma(page, vma); |
1051 | if (pvmw.address == -EFAULT) | |
31dbd01f IE |
1052 | goto out; |
1053 | ||
29ad768c | 1054 | BUG_ON(PageTransCompound(page)); |
6bdb913f | 1055 | |
7269f999 | 1056 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, |
6f4f13e8 | 1057 | pvmw.address, |
ac46d4f3 JG |
1058 | pvmw.address + PAGE_SIZE); |
1059 | mmu_notifier_invalidate_range_start(&range); | |
6bdb913f | 1060 | |
36eaff33 | 1061 | if (!page_vma_mapped_walk(&pvmw)) |
6bdb913f | 1062 | goto out_mn; |
36eaff33 KS |
1063 | if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?")) |
1064 | goto out_unlock; | |
31dbd01f | 1065 | |
6c287605 | 1066 | anon_exclusive = PageAnonExclusive(page); |
595cd8f2 | 1067 | if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) || |
b3a81d08 | 1068 | (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte)) || |
6c287605 | 1069 | anon_exclusive || mm_tlb_flush_pending(mm)) { |
31dbd01f IE |
1070 | pte_t entry; |
1071 | ||
1072 | swapped = PageSwapCache(page); | |
36eaff33 | 1073 | flush_cache_page(vma, pvmw.address, page_to_pfn(page)); |
31dbd01f | 1074 | /* |
25985edc | 1075 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
31dbd01f | 1076 | * take any lock, therefore the check that we are going to make |
f0953a1b | 1077 | * with the pagecount against the mapcount is racy and |
31dbd01f IE |
1078 | * O_DIRECT can happen right after the check. |
1079 | * So we clear the pte and flush the tlb before the check | |
1080 | * this assure us that no O_DIRECT can happen after the check | |
1081 | * or in the middle of the check. | |
0f10851e JG |
1082 | * |
1083 | * No need to notify as we are downgrading page table to read | |
1084 | * only not changing it to point to a new page. | |
1085 | * | |
ee65728e | 1086 | * See Documentation/mm/mmu_notifier.rst |
31dbd01f | 1087 | */ |
0f10851e | 1088 | entry = ptep_clear_flush(vma, pvmw.address, pvmw.pte); |
31dbd01f IE |
1089 | /* |
1090 | * Check that no O_DIRECT or similar I/O is in progress on the | |
1091 | * page | |
1092 | */ | |
31e855ea | 1093 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
36eaff33 | 1094 | set_pte_at(mm, pvmw.address, pvmw.pte, entry); |
31dbd01f IE |
1095 | goto out_unlock; |
1096 | } | |
6c287605 | 1097 | |
088b8aa5 | 1098 | /* See page_try_share_anon_rmap(): clear PTE first. */ |
6c287605 DH |
1099 | if (anon_exclusive && page_try_share_anon_rmap(page)) { |
1100 | set_pte_at(mm, pvmw.address, pvmw.pte, entry); | |
1101 | goto out_unlock; | |
1102 | } | |
1103 | ||
4e31635c HD |
1104 | if (pte_dirty(entry)) |
1105 | set_page_dirty(page); | |
595cd8f2 AK |
1106 | |
1107 | if (pte_protnone(entry)) | |
1108 | entry = pte_mkclean(pte_clear_savedwrite(entry)); | |
1109 | else | |
1110 | entry = pte_mkclean(pte_wrprotect(entry)); | |
36eaff33 | 1111 | set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry); |
31dbd01f | 1112 | } |
36eaff33 | 1113 | *orig_pte = *pvmw.pte; |
31dbd01f IE |
1114 | err = 0; |
1115 | ||
1116 | out_unlock: | |
36eaff33 | 1117 | page_vma_mapped_walk_done(&pvmw); |
6bdb913f | 1118 | out_mn: |
ac46d4f3 | 1119 | mmu_notifier_invalidate_range_end(&range); |
31dbd01f IE |
1120 | out: |
1121 | return err; | |
1122 | } | |
1123 | ||
1124 | /** | |
1125 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
1126 | * @vma: vma that holds the pte pointing to page |
1127 | * @page: the page we are replacing by kpage | |
1128 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
1129 | * @orig_pte: the original value of the pte |
1130 | * | |
1131 | * Returns 0 on success, -EFAULT on failure. | |
1132 | */ | |
8dd3557a HD |
1133 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
1134 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
1135 | { |
1136 | struct mm_struct *mm = vma->vm_mm; | |
31dbd01f | 1137 | pmd_t *pmd; |
50722804 | 1138 | pmd_t pmde; |
31dbd01f | 1139 | pte_t *ptep; |
e86c59b1 | 1140 | pte_t newpte; |
31dbd01f IE |
1141 | spinlock_t *ptl; |
1142 | unsigned long addr; | |
31dbd01f | 1143 | int err = -EFAULT; |
ac46d4f3 | 1144 | struct mmu_notifier_range range; |
31dbd01f | 1145 | |
8dd3557a | 1146 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
1147 | if (addr == -EFAULT) |
1148 | goto out; | |
1149 | ||
6219049a BL |
1150 | pmd = mm_find_pmd(mm, addr); |
1151 | if (!pmd) | |
31dbd01f | 1152 | goto out; |
50722804 ZK |
1153 | /* |
1154 | * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() | |
1155 | * without holding anon_vma lock for write. So when looking for a | |
1156 | * genuine pmde (in which to find pte), test present and !THP together. | |
1157 | */ | |
1158 | pmde = *pmd; | |
1159 | barrier(); | |
1160 | if (!pmd_present(pmde) || pmd_trans_huge(pmde)) | |
1161 | goto out; | |
31dbd01f | 1162 | |
7269f999 | 1163 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr, |
6f4f13e8 | 1164 | addr + PAGE_SIZE); |
ac46d4f3 | 1165 | mmu_notifier_invalidate_range_start(&range); |
6bdb913f | 1166 | |
31dbd01f IE |
1167 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
1168 | if (!pte_same(*ptep, orig_pte)) { | |
1169 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f | 1170 | goto out_mn; |
31dbd01f | 1171 | } |
6c287605 DH |
1172 | VM_BUG_ON_PAGE(PageAnonExclusive(page), page); |
1173 | VM_BUG_ON_PAGE(PageAnon(kpage) && PageAnonExclusive(kpage), kpage); | |
31dbd01f | 1174 | |
e86c59b1 CI |
1175 | /* |
1176 | * No need to check ksm_use_zero_pages here: we can only have a | |
457aef94 | 1177 | * zero_page here if ksm_use_zero_pages was enabled already. |
e86c59b1 CI |
1178 | */ |
1179 | if (!is_zero_pfn(page_to_pfn(kpage))) { | |
1180 | get_page(kpage); | |
f1e2db12 | 1181 | page_add_anon_rmap(kpage, vma, addr, RMAP_NONE); |
e86c59b1 CI |
1182 | newpte = mk_pte(kpage, vma->vm_page_prot); |
1183 | } else { | |
1184 | newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), | |
1185 | vma->vm_page_prot)); | |
a38c015f CI |
1186 | /* |
1187 | * We're replacing an anonymous page with a zero page, which is | |
1188 | * not anonymous. We need to do proper accounting otherwise we | |
1189 | * will get wrong values in /proc, and a BUG message in dmesg | |
1190 | * when tearing down the mm. | |
1191 | */ | |
1192 | dec_mm_counter(mm, MM_ANONPAGES); | |
e86c59b1 | 1193 | } |
31dbd01f IE |
1194 | |
1195 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
0f10851e JG |
1196 | /* |
1197 | * No need to notify as we are replacing a read only page with another | |
1198 | * read only page with the same content. | |
1199 | * | |
ee65728e | 1200 | * See Documentation/mm/mmu_notifier.rst |
0f10851e JG |
1201 | */ |
1202 | ptep_clear_flush(vma, addr, ptep); | |
e86c59b1 | 1203 | set_pte_at_notify(mm, addr, ptep, newpte); |
31dbd01f | 1204 | |
cea86fe2 | 1205 | page_remove_rmap(page, vma, false); |
ae52a2ad HD |
1206 | if (!page_mapped(page)) |
1207 | try_to_free_swap(page); | |
8dd3557a | 1208 | put_page(page); |
31dbd01f IE |
1209 | |
1210 | pte_unmap_unlock(ptep, ptl); | |
1211 | err = 0; | |
6bdb913f | 1212 | out_mn: |
ac46d4f3 | 1213 | mmu_notifier_invalidate_range_end(&range); |
31dbd01f IE |
1214 | out: |
1215 | return err; | |
1216 | } | |
1217 | ||
1218 | /* | |
1219 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
1220 | * @vma: the vma that holds the pte pointing to page |
1221 | * @page: the PageAnon page that we want to replace with kpage | |
80e14822 HD |
1222 | * @kpage: the PageKsm page that we want to map instead of page, |
1223 | * or NULL the first time when we want to use page as kpage. | |
31dbd01f IE |
1224 | * |
1225 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
1226 | */ | |
1227 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 1228 | struct page *page, struct page *kpage) |
31dbd01f IE |
1229 | { |
1230 | pte_t orig_pte = __pte(0); | |
1231 | int err = -EFAULT; | |
1232 | ||
db114b83 HD |
1233 | if (page == kpage) /* ksm page forked */ |
1234 | return 0; | |
1235 | ||
8dd3557a | 1236 | if (!PageAnon(page)) |
31dbd01f IE |
1237 | goto out; |
1238 | ||
31dbd01f IE |
1239 | /* |
1240 | * We need the page lock to read a stable PageSwapCache in | |
1241 | * write_protect_page(). We use trylock_page() instead of | |
1242 | * lock_page() because we don't want to wait here - we | |
1243 | * prefer to continue scanning and merging different pages, | |
1244 | * then come back to this page when it is unlocked. | |
1245 | */ | |
8dd3557a | 1246 | if (!trylock_page(page)) |
31e855ea | 1247 | goto out; |
f765f540 KS |
1248 | |
1249 | if (PageTransCompound(page)) { | |
a7306c34 | 1250 | if (split_huge_page(page)) |
f765f540 KS |
1251 | goto out_unlock; |
1252 | } | |
1253 | ||
31dbd01f IE |
1254 | /* |
1255 | * If this anonymous page is mapped only here, its pte may need | |
1256 | * to be write-protected. If it's mapped elsewhere, all of its | |
1257 | * ptes are necessarily already write-protected. But in either | |
1258 | * case, we need to lock and check page_count is not raised. | |
1259 | */ | |
80e14822 HD |
1260 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
1261 | if (!kpage) { | |
1262 | /* | |
1263 | * While we hold page lock, upgrade page from | |
1264 | * PageAnon+anon_vma to PageKsm+NULL stable_node: | |
1265 | * stable_tree_insert() will update stable_node. | |
1266 | */ | |
1267 | set_page_stable_node(page, NULL); | |
1268 | mark_page_accessed(page); | |
337ed7eb MK |
1269 | /* |
1270 | * Page reclaim just frees a clean page with no dirty | |
1271 | * ptes: make sure that the ksm page would be swapped. | |
1272 | */ | |
1273 | if (!PageDirty(page)) | |
1274 | SetPageDirty(page); | |
80e14822 HD |
1275 | err = 0; |
1276 | } else if (pages_identical(page, kpage)) | |
1277 | err = replace_page(vma, page, kpage, orig_pte); | |
1278 | } | |
31dbd01f | 1279 | |
f765f540 | 1280 | out_unlock: |
8dd3557a | 1281 | unlock_page(page); |
31dbd01f IE |
1282 | out: |
1283 | return err; | |
1284 | } | |
1285 | ||
81464e30 HD |
1286 | /* |
1287 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
1288 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
1289 | * |
1290 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 1291 | */ |
8dd3557a HD |
1292 | static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item, |
1293 | struct page *page, struct page *kpage) | |
81464e30 | 1294 | { |
8dd3557a | 1295 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
1296 | struct vm_area_struct *vma; |
1297 | int err = -EFAULT; | |
1298 | ||
d8ed45c5 | 1299 | mmap_read_lock(mm); |
85c6e8dd AA |
1300 | vma = find_mergeable_vma(mm, rmap_item->address); |
1301 | if (!vma) | |
81464e30 HD |
1302 | goto out; |
1303 | ||
8dd3557a | 1304 | err = try_to_merge_one_page(vma, page, kpage); |
db114b83 HD |
1305 | if (err) |
1306 | goto out; | |
1307 | ||
bc56620b HD |
1308 | /* Unstable nid is in union with stable anon_vma: remove first */ |
1309 | remove_rmap_item_from_tree(rmap_item); | |
1310 | ||
c1e8d7c6 | 1311 | /* Must get reference to anon_vma while still holding mmap_lock */ |
9e60109f PZ |
1312 | rmap_item->anon_vma = vma->anon_vma; |
1313 | get_anon_vma(vma->anon_vma); | |
81464e30 | 1314 | out: |
d8ed45c5 | 1315 | mmap_read_unlock(mm); |
81464e30 HD |
1316 | return err; |
1317 | } | |
1318 | ||
31dbd01f IE |
1319 | /* |
1320 | * try_to_merge_two_pages - take two identical pages and prepare them | |
1321 | * to be merged into one page. | |
1322 | * | |
8dd3557a HD |
1323 | * This function returns the kpage if we successfully merged two identical |
1324 | * pages into one ksm page, NULL otherwise. | |
31dbd01f | 1325 | * |
80e14822 | 1326 | * Note that this function upgrades page to ksm page: if one of the pages |
31dbd01f IE |
1327 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
1328 | */ | |
8dd3557a HD |
1329 | static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item, |
1330 | struct page *page, | |
1331 | struct rmap_item *tree_rmap_item, | |
1332 | struct page *tree_page) | |
31dbd01f | 1333 | { |
80e14822 | 1334 | int err; |
31dbd01f | 1335 | |
80e14822 | 1336 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
31dbd01f | 1337 | if (!err) { |
8dd3557a | 1338 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
80e14822 | 1339 | tree_page, page); |
31dbd01f | 1340 | /* |
81464e30 HD |
1341 | * If that fails, we have a ksm page with only one pte |
1342 | * pointing to it: so break it. | |
31dbd01f | 1343 | */ |
4035c07a | 1344 | if (err) |
8dd3557a | 1345 | break_cow(rmap_item); |
31dbd01f | 1346 | } |
80e14822 | 1347 | return err ? NULL : page; |
31dbd01f IE |
1348 | } |
1349 | ||
2c653d0e AA |
1350 | static __always_inline |
1351 | bool __is_page_sharing_candidate(struct stable_node *stable_node, int offset) | |
1352 | { | |
1353 | VM_BUG_ON(stable_node->rmap_hlist_len < 0); | |
1354 | /* | |
1355 | * Check that at least one mapping still exists, otherwise | |
1356 | * there's no much point to merge and share with this | |
1357 | * stable_node, as the underlying tree_page of the other | |
1358 | * sharer is going to be freed soon. | |
1359 | */ | |
1360 | return stable_node->rmap_hlist_len && | |
1361 | stable_node->rmap_hlist_len + offset < ksm_max_page_sharing; | |
1362 | } | |
1363 | ||
1364 | static __always_inline | |
1365 | bool is_page_sharing_candidate(struct stable_node *stable_node) | |
1366 | { | |
1367 | return __is_page_sharing_candidate(stable_node, 0); | |
1368 | } | |
1369 | ||
c01f0b54 CIK |
1370 | static struct page *stable_node_dup(struct stable_node **_stable_node_dup, |
1371 | struct stable_node **_stable_node, | |
1372 | struct rb_root *root, | |
1373 | bool prune_stale_stable_nodes) | |
2c653d0e | 1374 | { |
b4fecc67 | 1375 | struct stable_node *dup, *found = NULL, *stable_node = *_stable_node; |
2c653d0e | 1376 | struct hlist_node *hlist_safe; |
8dc5ffcd | 1377 | struct page *_tree_page, *tree_page = NULL; |
2c653d0e AA |
1378 | int nr = 0; |
1379 | int found_rmap_hlist_len; | |
1380 | ||
1381 | if (!prune_stale_stable_nodes || | |
1382 | time_before(jiffies, stable_node->chain_prune_time + | |
1383 | msecs_to_jiffies( | |
1384 | ksm_stable_node_chains_prune_millisecs))) | |
1385 | prune_stale_stable_nodes = false; | |
1386 | else | |
1387 | stable_node->chain_prune_time = jiffies; | |
1388 | ||
1389 | hlist_for_each_entry_safe(dup, hlist_safe, | |
1390 | &stable_node->hlist, hlist_dup) { | |
1391 | cond_resched(); | |
1392 | /* | |
1393 | * We must walk all stable_node_dup to prune the stale | |
1394 | * stable nodes during lookup. | |
1395 | * | |
1396 | * get_ksm_page can drop the nodes from the | |
1397 | * stable_node->hlist if they point to freed pages | |
1398 | * (that's why we do a _safe walk). The "dup" | |
1399 | * stable_node parameter itself will be freed from | |
1400 | * under us if it returns NULL. | |
1401 | */ | |
2cee57d1 | 1402 | _tree_page = get_ksm_page(dup, GET_KSM_PAGE_NOLOCK); |
2c653d0e AA |
1403 | if (!_tree_page) |
1404 | continue; | |
1405 | nr += 1; | |
1406 | if (is_page_sharing_candidate(dup)) { | |
1407 | if (!found || | |
1408 | dup->rmap_hlist_len > found_rmap_hlist_len) { | |
1409 | if (found) | |
8dc5ffcd | 1410 | put_page(tree_page); |
2c653d0e AA |
1411 | found = dup; |
1412 | found_rmap_hlist_len = found->rmap_hlist_len; | |
8dc5ffcd | 1413 | tree_page = _tree_page; |
2c653d0e | 1414 | |
8dc5ffcd | 1415 | /* skip put_page for found dup */ |
2c653d0e AA |
1416 | if (!prune_stale_stable_nodes) |
1417 | break; | |
2c653d0e AA |
1418 | continue; |
1419 | } | |
1420 | } | |
1421 | put_page(_tree_page); | |
1422 | } | |
1423 | ||
80b18dfa AA |
1424 | if (found) { |
1425 | /* | |
1426 | * nr is counting all dups in the chain only if | |
1427 | * prune_stale_stable_nodes is true, otherwise we may | |
1428 | * break the loop at nr == 1 even if there are | |
1429 | * multiple entries. | |
1430 | */ | |
1431 | if (prune_stale_stable_nodes && nr == 1) { | |
2c653d0e AA |
1432 | /* |
1433 | * If there's not just one entry it would | |
1434 | * corrupt memory, better BUG_ON. In KSM | |
1435 | * context with no lock held it's not even | |
1436 | * fatal. | |
1437 | */ | |
1438 | BUG_ON(stable_node->hlist.first->next); | |
1439 | ||
1440 | /* | |
1441 | * There's just one entry and it is below the | |
1442 | * deduplication limit so drop the chain. | |
1443 | */ | |
1444 | rb_replace_node(&stable_node->node, &found->node, | |
1445 | root); | |
1446 | free_stable_node(stable_node); | |
1447 | ksm_stable_node_chains--; | |
1448 | ksm_stable_node_dups--; | |
b4fecc67 | 1449 | /* |
0ba1d0f7 AA |
1450 | * NOTE: the caller depends on the stable_node |
1451 | * to be equal to stable_node_dup if the chain | |
1452 | * was collapsed. | |
b4fecc67 | 1453 | */ |
0ba1d0f7 AA |
1454 | *_stable_node = found; |
1455 | /* | |
f0953a1b | 1456 | * Just for robustness, as stable_node is |
0ba1d0f7 AA |
1457 | * otherwise left as a stable pointer, the |
1458 | * compiler shall optimize it away at build | |
1459 | * time. | |
1460 | */ | |
1461 | stable_node = NULL; | |
80b18dfa AA |
1462 | } else if (stable_node->hlist.first != &found->hlist_dup && |
1463 | __is_page_sharing_candidate(found, 1)) { | |
2c653d0e | 1464 | /* |
80b18dfa AA |
1465 | * If the found stable_node dup can accept one |
1466 | * more future merge (in addition to the one | |
1467 | * that is underway) and is not at the head of | |
1468 | * the chain, put it there so next search will | |
1469 | * be quicker in the !prune_stale_stable_nodes | |
1470 | * case. | |
1471 | * | |
1472 | * NOTE: it would be inaccurate to use nr > 1 | |
1473 | * instead of checking the hlist.first pointer | |
1474 | * directly, because in the | |
1475 | * prune_stale_stable_nodes case "nr" isn't | |
1476 | * the position of the found dup in the chain, | |
1477 | * but the total number of dups in the chain. | |
2c653d0e AA |
1478 | */ |
1479 | hlist_del(&found->hlist_dup); | |
1480 | hlist_add_head(&found->hlist_dup, | |
1481 | &stable_node->hlist); | |
1482 | } | |
1483 | } | |
1484 | ||
8dc5ffcd AA |
1485 | *_stable_node_dup = found; |
1486 | return tree_page; | |
2c653d0e AA |
1487 | } |
1488 | ||
1489 | static struct stable_node *stable_node_dup_any(struct stable_node *stable_node, | |
1490 | struct rb_root *root) | |
1491 | { | |
1492 | if (!is_stable_node_chain(stable_node)) | |
1493 | return stable_node; | |
1494 | if (hlist_empty(&stable_node->hlist)) { | |
1495 | free_stable_node_chain(stable_node, root); | |
1496 | return NULL; | |
1497 | } | |
1498 | return hlist_entry(stable_node->hlist.first, | |
1499 | typeof(*stable_node), hlist_dup); | |
1500 | } | |
1501 | ||
8dc5ffcd AA |
1502 | /* |
1503 | * Like for get_ksm_page, this function can free the *_stable_node and | |
1504 | * *_stable_node_dup if the returned tree_page is NULL. | |
1505 | * | |
1506 | * It can also free and overwrite *_stable_node with the found | |
1507 | * stable_node_dup if the chain is collapsed (in which case | |
1508 | * *_stable_node will be equal to *_stable_node_dup like if the chain | |
1509 | * never existed). It's up to the caller to verify tree_page is not | |
1510 | * NULL before dereferencing *_stable_node or *_stable_node_dup. | |
1511 | * | |
1512 | * *_stable_node_dup is really a second output parameter of this | |
1513 | * function and will be overwritten in all cases, the caller doesn't | |
1514 | * need to initialize it. | |
1515 | */ | |
1516 | static struct page *__stable_node_chain(struct stable_node **_stable_node_dup, | |
1517 | struct stable_node **_stable_node, | |
1518 | struct rb_root *root, | |
1519 | bool prune_stale_stable_nodes) | |
2c653d0e | 1520 | { |
b4fecc67 | 1521 | struct stable_node *stable_node = *_stable_node; |
2c653d0e AA |
1522 | if (!is_stable_node_chain(stable_node)) { |
1523 | if (is_page_sharing_candidate(stable_node)) { | |
8dc5ffcd | 1524 | *_stable_node_dup = stable_node; |
2cee57d1 | 1525 | return get_ksm_page(stable_node, GET_KSM_PAGE_NOLOCK); |
2c653d0e | 1526 | } |
8dc5ffcd AA |
1527 | /* |
1528 | * _stable_node_dup set to NULL means the stable_node | |
1529 | * reached the ksm_max_page_sharing limit. | |
1530 | */ | |
1531 | *_stable_node_dup = NULL; | |
2c653d0e AA |
1532 | return NULL; |
1533 | } | |
8dc5ffcd | 1534 | return stable_node_dup(_stable_node_dup, _stable_node, root, |
2c653d0e AA |
1535 | prune_stale_stable_nodes); |
1536 | } | |
1537 | ||
8dc5ffcd AA |
1538 | static __always_inline struct page *chain_prune(struct stable_node **s_n_d, |
1539 | struct stable_node **s_n, | |
1540 | struct rb_root *root) | |
2c653d0e | 1541 | { |
8dc5ffcd | 1542 | return __stable_node_chain(s_n_d, s_n, root, true); |
2c653d0e AA |
1543 | } |
1544 | ||
8dc5ffcd AA |
1545 | static __always_inline struct page *chain(struct stable_node **s_n_d, |
1546 | struct stable_node *s_n, | |
1547 | struct rb_root *root) | |
2c653d0e | 1548 | { |
8dc5ffcd AA |
1549 | struct stable_node *old_stable_node = s_n; |
1550 | struct page *tree_page; | |
1551 | ||
1552 | tree_page = __stable_node_chain(s_n_d, &s_n, root, false); | |
1553 | /* not pruning dups so s_n cannot have changed */ | |
1554 | VM_BUG_ON(s_n != old_stable_node); | |
1555 | return tree_page; | |
2c653d0e AA |
1556 | } |
1557 | ||
31dbd01f | 1558 | /* |
8dd3557a | 1559 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
1560 | * |
1561 | * This function checks if there is a page inside the stable tree | |
1562 | * with identical content to the page that we are scanning right now. | |
1563 | * | |
7b6ba2c7 | 1564 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
1565 | * NULL otherwise. |
1566 | */ | |
62b61f61 | 1567 | static struct page *stable_tree_search(struct page *page) |
31dbd01f | 1568 | { |
90bd6fd3 | 1569 | int nid; |
ef53d16c | 1570 | struct rb_root *root; |
4146d2d6 HD |
1571 | struct rb_node **new; |
1572 | struct rb_node *parent; | |
2c653d0e | 1573 | struct stable_node *stable_node, *stable_node_dup, *stable_node_any; |
4146d2d6 | 1574 | struct stable_node *page_node; |
31dbd01f | 1575 | |
4146d2d6 HD |
1576 | page_node = page_stable_node(page); |
1577 | if (page_node && page_node->head != &migrate_nodes) { | |
1578 | /* ksm page forked */ | |
08beca44 | 1579 | get_page(page); |
62b61f61 | 1580 | return page; |
08beca44 HD |
1581 | } |
1582 | ||
90bd6fd3 | 1583 | nid = get_kpfn_nid(page_to_pfn(page)); |
ef53d16c | 1584 | root = root_stable_tree + nid; |
4146d2d6 | 1585 | again: |
ef53d16c | 1586 | new = &root->rb_node; |
4146d2d6 | 1587 | parent = NULL; |
90bd6fd3 | 1588 | |
4146d2d6 | 1589 | while (*new) { |
4035c07a | 1590 | struct page *tree_page; |
31dbd01f IE |
1591 | int ret; |
1592 | ||
08beca44 | 1593 | cond_resched(); |
4146d2d6 | 1594 | stable_node = rb_entry(*new, struct stable_node, node); |
2c653d0e | 1595 | stable_node_any = NULL; |
8dc5ffcd | 1596 | tree_page = chain_prune(&stable_node_dup, &stable_node, root); |
b4fecc67 AA |
1597 | /* |
1598 | * NOTE: stable_node may have been freed by | |
1599 | * chain_prune() if the returned stable_node_dup is | |
1600 | * not NULL. stable_node_dup may have been inserted in | |
1601 | * the rbtree instead as a regular stable_node (in | |
1602 | * order to collapse the stable_node chain if a single | |
0ba1d0f7 | 1603 | * stable_node dup was found in it). In such case the |
3413b2c8 | 1604 | * stable_node is overwritten by the callee to point |
0ba1d0f7 AA |
1605 | * to the stable_node_dup that was collapsed in the |
1606 | * stable rbtree and stable_node will be equal to | |
1607 | * stable_node_dup like if the chain never existed. | |
b4fecc67 | 1608 | */ |
2c653d0e AA |
1609 | if (!stable_node_dup) { |
1610 | /* | |
1611 | * Either all stable_node dups were full in | |
1612 | * this stable_node chain, or this chain was | |
1613 | * empty and should be rb_erased. | |
1614 | */ | |
1615 | stable_node_any = stable_node_dup_any(stable_node, | |
1616 | root); | |
1617 | if (!stable_node_any) { | |
1618 | /* rb_erase just run */ | |
1619 | goto again; | |
1620 | } | |
1621 | /* | |
1622 | * Take any of the stable_node dups page of | |
1623 | * this stable_node chain to let the tree walk | |
1624 | * continue. All KSM pages belonging to the | |
1625 | * stable_node dups in a stable_node chain | |
1626 | * have the same content and they're | |
457aef94 | 1627 | * write protected at all times. Any will work |
2c653d0e AA |
1628 | * fine to continue the walk. |
1629 | */ | |
2cee57d1 YS |
1630 | tree_page = get_ksm_page(stable_node_any, |
1631 | GET_KSM_PAGE_NOLOCK); | |
2c653d0e AA |
1632 | } |
1633 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); | |
f2e5ff85 AA |
1634 | if (!tree_page) { |
1635 | /* | |
1636 | * If we walked over a stale stable_node, | |
1637 | * get_ksm_page() will call rb_erase() and it | |
1638 | * may rebalance the tree from under us. So | |
1639 | * restart the search from scratch. Returning | |
1640 | * NULL would be safe too, but we'd generate | |
1641 | * false negative insertions just because some | |
1642 | * stable_node was stale. | |
1643 | */ | |
1644 | goto again; | |
1645 | } | |
31dbd01f | 1646 | |
4035c07a | 1647 | ret = memcmp_pages(page, tree_page); |
c8d6553b | 1648 | put_page(tree_page); |
31dbd01f | 1649 | |
4146d2d6 | 1650 | parent = *new; |
c8d6553b | 1651 | if (ret < 0) |
4146d2d6 | 1652 | new = &parent->rb_left; |
c8d6553b | 1653 | else if (ret > 0) |
4146d2d6 | 1654 | new = &parent->rb_right; |
c8d6553b | 1655 | else { |
2c653d0e AA |
1656 | if (page_node) { |
1657 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1658 | /* | |
1659 | * Test if the migrated page should be merged | |
1660 | * into a stable node dup. If the mapcount is | |
1661 | * 1 we can migrate it with another KSM page | |
1662 | * without adding it to the chain. | |
1663 | */ | |
1664 | if (page_mapcount(page) > 1) | |
1665 | goto chain_append; | |
1666 | } | |
1667 | ||
1668 | if (!stable_node_dup) { | |
1669 | /* | |
1670 | * If the stable_node is a chain and | |
1671 | * we got a payload match in memcmp | |
1672 | * but we cannot merge the scanned | |
1673 | * page in any of the existing | |
1674 | * stable_node dups because they're | |
1675 | * all full, we need to wait the | |
1676 | * scanned page to find itself a match | |
1677 | * in the unstable tree to create a | |
1678 | * brand new KSM page to add later to | |
1679 | * the dups of this stable_node. | |
1680 | */ | |
1681 | return NULL; | |
1682 | } | |
1683 | ||
c8d6553b HD |
1684 | /* |
1685 | * Lock and unlock the stable_node's page (which | |
1686 | * might already have been migrated) so that page | |
1687 | * migration is sure to notice its raised count. | |
1688 | * It would be more elegant to return stable_node | |
1689 | * than kpage, but that involves more changes. | |
1690 | */ | |
2cee57d1 YS |
1691 | tree_page = get_ksm_page(stable_node_dup, |
1692 | GET_KSM_PAGE_TRYLOCK); | |
1693 | ||
1694 | if (PTR_ERR(tree_page) == -EBUSY) | |
1695 | return ERR_PTR(-EBUSY); | |
1696 | ||
2c653d0e AA |
1697 | if (unlikely(!tree_page)) |
1698 | /* | |
1699 | * The tree may have been rebalanced, | |
1700 | * so re-evaluate parent and new. | |
1701 | */ | |
4146d2d6 | 1702 | goto again; |
2c653d0e AA |
1703 | unlock_page(tree_page); |
1704 | ||
1705 | if (get_kpfn_nid(stable_node_dup->kpfn) != | |
1706 | NUMA(stable_node_dup->nid)) { | |
1707 | put_page(tree_page); | |
1708 | goto replace; | |
1709 | } | |
1710 | return tree_page; | |
c8d6553b | 1711 | } |
31dbd01f IE |
1712 | } |
1713 | ||
4146d2d6 HD |
1714 | if (!page_node) |
1715 | return NULL; | |
1716 | ||
1717 | list_del(&page_node->list); | |
1718 | DO_NUMA(page_node->nid = nid); | |
1719 | rb_link_node(&page_node->node, parent, new); | |
ef53d16c | 1720 | rb_insert_color(&page_node->node, root); |
2c653d0e AA |
1721 | out: |
1722 | if (is_page_sharing_candidate(page_node)) { | |
1723 | get_page(page); | |
1724 | return page; | |
1725 | } else | |
1726 | return NULL; | |
4146d2d6 HD |
1727 | |
1728 | replace: | |
b4fecc67 AA |
1729 | /* |
1730 | * If stable_node was a chain and chain_prune collapsed it, | |
0ba1d0f7 AA |
1731 | * stable_node has been updated to be the new regular |
1732 | * stable_node. A collapse of the chain is indistinguishable | |
1733 | * from the case there was no chain in the stable | |
1734 | * rbtree. Otherwise stable_node is the chain and | |
1735 | * stable_node_dup is the dup to replace. | |
b4fecc67 | 1736 | */ |
0ba1d0f7 | 1737 | if (stable_node_dup == stable_node) { |
b4fecc67 AA |
1738 | VM_BUG_ON(is_stable_node_chain(stable_node_dup)); |
1739 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); | |
2c653d0e AA |
1740 | /* there is no chain */ |
1741 | if (page_node) { | |
1742 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1743 | list_del(&page_node->list); | |
1744 | DO_NUMA(page_node->nid = nid); | |
b4fecc67 AA |
1745 | rb_replace_node(&stable_node_dup->node, |
1746 | &page_node->node, | |
2c653d0e AA |
1747 | root); |
1748 | if (is_page_sharing_candidate(page_node)) | |
1749 | get_page(page); | |
1750 | else | |
1751 | page = NULL; | |
1752 | } else { | |
b4fecc67 | 1753 | rb_erase(&stable_node_dup->node, root); |
2c653d0e AA |
1754 | page = NULL; |
1755 | } | |
4146d2d6 | 1756 | } else { |
2c653d0e AA |
1757 | VM_BUG_ON(!is_stable_node_chain(stable_node)); |
1758 | __stable_node_dup_del(stable_node_dup); | |
1759 | if (page_node) { | |
1760 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1761 | list_del(&page_node->list); | |
1762 | DO_NUMA(page_node->nid = nid); | |
1763 | stable_node_chain_add_dup(page_node, stable_node); | |
1764 | if (is_page_sharing_candidate(page_node)) | |
1765 | get_page(page); | |
1766 | else | |
1767 | page = NULL; | |
1768 | } else { | |
1769 | page = NULL; | |
1770 | } | |
4146d2d6 | 1771 | } |
2c653d0e AA |
1772 | stable_node_dup->head = &migrate_nodes; |
1773 | list_add(&stable_node_dup->list, stable_node_dup->head); | |
4146d2d6 | 1774 | return page; |
2c653d0e AA |
1775 | |
1776 | chain_append: | |
1777 | /* stable_node_dup could be null if it reached the limit */ | |
1778 | if (!stable_node_dup) | |
1779 | stable_node_dup = stable_node_any; | |
b4fecc67 AA |
1780 | /* |
1781 | * If stable_node was a chain and chain_prune collapsed it, | |
0ba1d0f7 AA |
1782 | * stable_node has been updated to be the new regular |
1783 | * stable_node. A collapse of the chain is indistinguishable | |
1784 | * from the case there was no chain in the stable | |
1785 | * rbtree. Otherwise stable_node is the chain and | |
1786 | * stable_node_dup is the dup to replace. | |
b4fecc67 | 1787 | */ |
0ba1d0f7 | 1788 | if (stable_node_dup == stable_node) { |
b4fecc67 | 1789 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); |
2c653d0e AA |
1790 | /* chain is missing so create it */ |
1791 | stable_node = alloc_stable_node_chain(stable_node_dup, | |
1792 | root); | |
1793 | if (!stable_node) | |
1794 | return NULL; | |
1795 | } | |
1796 | /* | |
1797 | * Add this stable_node dup that was | |
1798 | * migrated to the stable_node chain | |
1799 | * of the current nid for this page | |
1800 | * content. | |
1801 | */ | |
b4fecc67 | 1802 | VM_BUG_ON(!is_stable_node_dup(stable_node_dup)); |
2c653d0e AA |
1803 | VM_BUG_ON(page_node->head != &migrate_nodes); |
1804 | list_del(&page_node->list); | |
1805 | DO_NUMA(page_node->nid = nid); | |
1806 | stable_node_chain_add_dup(page_node, stable_node); | |
1807 | goto out; | |
31dbd01f IE |
1808 | } |
1809 | ||
1810 | /* | |
e850dcf5 | 1811 | * stable_tree_insert - insert stable tree node pointing to new ksm page |
31dbd01f IE |
1812 | * into the stable tree. |
1813 | * | |
7b6ba2c7 HD |
1814 | * This function returns the stable tree node just allocated on success, |
1815 | * NULL otherwise. | |
31dbd01f | 1816 | */ |
7b6ba2c7 | 1817 | static struct stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f | 1818 | { |
90bd6fd3 PH |
1819 | int nid; |
1820 | unsigned long kpfn; | |
ef53d16c | 1821 | struct rb_root *root; |
90bd6fd3 | 1822 | struct rb_node **new; |
f2e5ff85 | 1823 | struct rb_node *parent; |
2c653d0e AA |
1824 | struct stable_node *stable_node, *stable_node_dup, *stable_node_any; |
1825 | bool need_chain = false; | |
31dbd01f | 1826 | |
90bd6fd3 PH |
1827 | kpfn = page_to_pfn(kpage); |
1828 | nid = get_kpfn_nid(kpfn); | |
ef53d16c | 1829 | root = root_stable_tree + nid; |
f2e5ff85 AA |
1830 | again: |
1831 | parent = NULL; | |
ef53d16c | 1832 | new = &root->rb_node; |
90bd6fd3 | 1833 | |
31dbd01f | 1834 | while (*new) { |
4035c07a | 1835 | struct page *tree_page; |
31dbd01f IE |
1836 | int ret; |
1837 | ||
08beca44 | 1838 | cond_resched(); |
7b6ba2c7 | 1839 | stable_node = rb_entry(*new, struct stable_node, node); |
2c653d0e | 1840 | stable_node_any = NULL; |
8dc5ffcd | 1841 | tree_page = chain(&stable_node_dup, stable_node, root); |
2c653d0e AA |
1842 | if (!stable_node_dup) { |
1843 | /* | |
1844 | * Either all stable_node dups were full in | |
1845 | * this stable_node chain, or this chain was | |
1846 | * empty and should be rb_erased. | |
1847 | */ | |
1848 | stable_node_any = stable_node_dup_any(stable_node, | |
1849 | root); | |
1850 | if (!stable_node_any) { | |
1851 | /* rb_erase just run */ | |
1852 | goto again; | |
1853 | } | |
1854 | /* | |
1855 | * Take any of the stable_node dups page of | |
1856 | * this stable_node chain to let the tree walk | |
1857 | * continue. All KSM pages belonging to the | |
1858 | * stable_node dups in a stable_node chain | |
1859 | * have the same content and they're | |
457aef94 | 1860 | * write protected at all times. Any will work |
2c653d0e AA |
1861 | * fine to continue the walk. |
1862 | */ | |
2cee57d1 YS |
1863 | tree_page = get_ksm_page(stable_node_any, |
1864 | GET_KSM_PAGE_NOLOCK); | |
2c653d0e AA |
1865 | } |
1866 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); | |
f2e5ff85 AA |
1867 | if (!tree_page) { |
1868 | /* | |
1869 | * If we walked over a stale stable_node, | |
1870 | * get_ksm_page() will call rb_erase() and it | |
1871 | * may rebalance the tree from under us. So | |
1872 | * restart the search from scratch. Returning | |
1873 | * NULL would be safe too, but we'd generate | |
1874 | * false negative insertions just because some | |
1875 | * stable_node was stale. | |
1876 | */ | |
1877 | goto again; | |
1878 | } | |
31dbd01f | 1879 | |
4035c07a HD |
1880 | ret = memcmp_pages(kpage, tree_page); |
1881 | put_page(tree_page); | |
31dbd01f IE |
1882 | |
1883 | parent = *new; | |
1884 | if (ret < 0) | |
1885 | new = &parent->rb_left; | |
1886 | else if (ret > 0) | |
1887 | new = &parent->rb_right; | |
1888 | else { | |
2c653d0e AA |
1889 | need_chain = true; |
1890 | break; | |
31dbd01f IE |
1891 | } |
1892 | } | |
1893 | ||
2c653d0e AA |
1894 | stable_node_dup = alloc_stable_node(); |
1895 | if (!stable_node_dup) | |
7b6ba2c7 | 1896 | return NULL; |
31dbd01f | 1897 | |
2c653d0e AA |
1898 | INIT_HLIST_HEAD(&stable_node_dup->hlist); |
1899 | stable_node_dup->kpfn = kpfn; | |
1900 | set_page_stable_node(kpage, stable_node_dup); | |
1901 | stable_node_dup->rmap_hlist_len = 0; | |
1902 | DO_NUMA(stable_node_dup->nid = nid); | |
1903 | if (!need_chain) { | |
1904 | rb_link_node(&stable_node_dup->node, parent, new); | |
1905 | rb_insert_color(&stable_node_dup->node, root); | |
1906 | } else { | |
1907 | if (!is_stable_node_chain(stable_node)) { | |
1908 | struct stable_node *orig = stable_node; | |
1909 | /* chain is missing so create it */ | |
1910 | stable_node = alloc_stable_node_chain(orig, root); | |
1911 | if (!stable_node) { | |
1912 | free_stable_node(stable_node_dup); | |
1913 | return NULL; | |
1914 | } | |
1915 | } | |
1916 | stable_node_chain_add_dup(stable_node_dup, stable_node); | |
1917 | } | |
08beca44 | 1918 | |
2c653d0e | 1919 | return stable_node_dup; |
31dbd01f IE |
1920 | } |
1921 | ||
1922 | /* | |
8dd3557a HD |
1923 | * unstable_tree_search_insert - search for identical page, |
1924 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
1925 | * |
1926 | * This function searches for a page in the unstable tree identical to the | |
1927 | * page currently being scanned; and if no identical page is found in the | |
1928 | * tree, we insert rmap_item as a new object into the unstable tree. | |
1929 | * | |
1930 | * This function returns pointer to rmap_item found to be identical | |
1931 | * to the currently scanned page, NULL otherwise. | |
1932 | * | |
1933 | * This function does both searching and inserting, because they share | |
1934 | * the same walking algorithm in an rbtree. | |
1935 | */ | |
8dd3557a HD |
1936 | static |
1937 | struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item, | |
1938 | struct page *page, | |
1939 | struct page **tree_pagep) | |
31dbd01f | 1940 | { |
90bd6fd3 PH |
1941 | struct rb_node **new; |
1942 | struct rb_root *root; | |
31dbd01f | 1943 | struct rb_node *parent = NULL; |
90bd6fd3 PH |
1944 | int nid; |
1945 | ||
1946 | nid = get_kpfn_nid(page_to_pfn(page)); | |
ef53d16c | 1947 | root = root_unstable_tree + nid; |
90bd6fd3 | 1948 | new = &root->rb_node; |
31dbd01f IE |
1949 | |
1950 | while (*new) { | |
1951 | struct rmap_item *tree_rmap_item; | |
8dd3557a | 1952 | struct page *tree_page; |
31dbd01f IE |
1953 | int ret; |
1954 | ||
d178f27f | 1955 | cond_resched(); |
31dbd01f | 1956 | tree_rmap_item = rb_entry(*new, struct rmap_item, node); |
8dd3557a | 1957 | tree_page = get_mergeable_page(tree_rmap_item); |
c8f95ed1 | 1958 | if (!tree_page) |
31dbd01f IE |
1959 | return NULL; |
1960 | ||
1961 | /* | |
8dd3557a | 1962 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 1963 | */ |
8dd3557a HD |
1964 | if (page == tree_page) { |
1965 | put_page(tree_page); | |
31dbd01f IE |
1966 | return NULL; |
1967 | } | |
1968 | ||
8dd3557a | 1969 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
1970 | |
1971 | parent = *new; | |
1972 | if (ret < 0) { | |
8dd3557a | 1973 | put_page(tree_page); |
31dbd01f IE |
1974 | new = &parent->rb_left; |
1975 | } else if (ret > 0) { | |
8dd3557a | 1976 | put_page(tree_page); |
31dbd01f | 1977 | new = &parent->rb_right; |
b599cbdf HD |
1978 | } else if (!ksm_merge_across_nodes && |
1979 | page_to_nid(tree_page) != nid) { | |
1980 | /* | |
1981 | * If tree_page has been migrated to another NUMA node, | |
1982 | * it will be flushed out and put in the right unstable | |
1983 | * tree next time: only merge with it when across_nodes. | |
1984 | */ | |
1985 | put_page(tree_page); | |
1986 | return NULL; | |
31dbd01f | 1987 | } else { |
8dd3557a | 1988 | *tree_pagep = tree_page; |
31dbd01f IE |
1989 | return tree_rmap_item; |
1990 | } | |
1991 | } | |
1992 | ||
7b6ba2c7 | 1993 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f | 1994 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
e850dcf5 | 1995 | DO_NUMA(rmap_item->nid = nid); |
31dbd01f | 1996 | rb_link_node(&rmap_item->node, parent, new); |
90bd6fd3 | 1997 | rb_insert_color(&rmap_item->node, root); |
31dbd01f | 1998 | |
473b0ce4 | 1999 | ksm_pages_unshared++; |
31dbd01f IE |
2000 | return NULL; |
2001 | } | |
2002 | ||
2003 | /* | |
2004 | * stable_tree_append - add another rmap_item to the linked list of | |
2005 | * rmap_items hanging off a given node of the stable tree, all sharing | |
2006 | * the same ksm page. | |
2007 | */ | |
2008 | static void stable_tree_append(struct rmap_item *rmap_item, | |
2c653d0e AA |
2009 | struct stable_node *stable_node, |
2010 | bool max_page_sharing_bypass) | |
31dbd01f | 2011 | { |
2c653d0e AA |
2012 | /* |
2013 | * rmap won't find this mapping if we don't insert the | |
2014 | * rmap_item in the right stable_node | |
2015 | * duplicate. page_migration could break later if rmap breaks, | |
2016 | * so we can as well crash here. We really need to check for | |
2017 | * rmap_hlist_len == STABLE_NODE_CHAIN, but we can as well check | |
457aef94 | 2018 | * for other negative values as an underflow if detected here |
2c653d0e AA |
2019 | * for the first time (and not when decreasing rmap_hlist_len) |
2020 | * would be sign of memory corruption in the stable_node. | |
2021 | */ | |
2022 | BUG_ON(stable_node->rmap_hlist_len < 0); | |
2023 | ||
2024 | stable_node->rmap_hlist_len++; | |
2025 | if (!max_page_sharing_bypass) | |
2026 | /* possibly non fatal but unexpected overflow, only warn */ | |
2027 | WARN_ON_ONCE(stable_node->rmap_hlist_len > | |
2028 | ksm_max_page_sharing); | |
2029 | ||
7b6ba2c7 | 2030 | rmap_item->head = stable_node; |
31dbd01f | 2031 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 2032 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 2033 | |
7b6ba2c7 HD |
2034 | if (rmap_item->hlist.next) |
2035 | ksm_pages_sharing++; | |
2036 | else | |
2037 | ksm_pages_shared++; | |
76093853 | 2038 | |
2039 | rmap_item->mm->ksm_merging_pages++; | |
31dbd01f IE |
2040 | } |
2041 | ||
2042 | /* | |
81464e30 HD |
2043 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
2044 | * if not, compare checksum to previous and if it's the same, see if page can | |
2045 | * be inserted into the unstable tree, or merged with a page already there and | |
2046 | * both transferred to the stable tree. | |
31dbd01f IE |
2047 | * |
2048 | * @page: the page that we are searching identical page to. | |
2049 | * @rmap_item: the reverse mapping into the virtual address of this page | |
2050 | */ | |
2051 | static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) | |
2052 | { | |
4b22927f | 2053 | struct mm_struct *mm = rmap_item->mm; |
31dbd01f | 2054 | struct rmap_item *tree_rmap_item; |
8dd3557a | 2055 | struct page *tree_page = NULL; |
7b6ba2c7 | 2056 | struct stable_node *stable_node; |
8dd3557a | 2057 | struct page *kpage; |
31dbd01f IE |
2058 | unsigned int checksum; |
2059 | int err; | |
2c653d0e | 2060 | bool max_page_sharing_bypass = false; |
31dbd01f | 2061 | |
4146d2d6 HD |
2062 | stable_node = page_stable_node(page); |
2063 | if (stable_node) { | |
2064 | if (stable_node->head != &migrate_nodes && | |
2c653d0e AA |
2065 | get_kpfn_nid(READ_ONCE(stable_node->kpfn)) != |
2066 | NUMA(stable_node->nid)) { | |
2067 | stable_node_dup_del(stable_node); | |
4146d2d6 HD |
2068 | stable_node->head = &migrate_nodes; |
2069 | list_add(&stable_node->list, stable_node->head); | |
2070 | } | |
2071 | if (stable_node->head != &migrate_nodes && | |
2072 | rmap_item->head == stable_node) | |
2073 | return; | |
2c653d0e AA |
2074 | /* |
2075 | * If it's a KSM fork, allow it to go over the sharing limit | |
2076 | * without warnings. | |
2077 | */ | |
2078 | if (!is_page_sharing_candidate(stable_node)) | |
2079 | max_page_sharing_bypass = true; | |
4146d2d6 | 2080 | } |
31dbd01f IE |
2081 | |
2082 | /* We first start with searching the page inside the stable tree */ | |
62b61f61 | 2083 | kpage = stable_tree_search(page); |
4146d2d6 HD |
2084 | if (kpage == page && rmap_item->head == stable_node) { |
2085 | put_page(kpage); | |
2086 | return; | |
2087 | } | |
2088 | ||
2089 | remove_rmap_item_from_tree(rmap_item); | |
2090 | ||
62b61f61 | 2091 | if (kpage) { |
2cee57d1 YS |
2092 | if (PTR_ERR(kpage) == -EBUSY) |
2093 | return; | |
2094 | ||
08beca44 | 2095 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
31dbd01f IE |
2096 | if (!err) { |
2097 | /* | |
2098 | * The page was successfully merged: | |
2099 | * add its rmap_item to the stable tree. | |
2100 | */ | |
5ad64688 | 2101 | lock_page(kpage); |
2c653d0e AA |
2102 | stable_tree_append(rmap_item, page_stable_node(kpage), |
2103 | max_page_sharing_bypass); | |
5ad64688 | 2104 | unlock_page(kpage); |
31dbd01f | 2105 | } |
8dd3557a | 2106 | put_page(kpage); |
31dbd01f IE |
2107 | return; |
2108 | } | |
2109 | ||
2110 | /* | |
4035c07a HD |
2111 | * If the hash value of the page has changed from the last time |
2112 | * we calculated it, this page is changing frequently: therefore we | |
2113 | * don't want to insert it in the unstable tree, and we don't want | |
2114 | * to waste our time searching for something identical to it there. | |
31dbd01f IE |
2115 | */ |
2116 | checksum = calc_checksum(page); | |
2117 | if (rmap_item->oldchecksum != checksum) { | |
2118 | rmap_item->oldchecksum = checksum; | |
2119 | return; | |
2120 | } | |
2121 | ||
e86c59b1 CI |
2122 | /* |
2123 | * Same checksum as an empty page. We attempt to merge it with the | |
2124 | * appropriate zero page if the user enabled this via sysfs. | |
2125 | */ | |
2126 | if (ksm_use_zero_pages && (checksum == zero_checksum)) { | |
2127 | struct vm_area_struct *vma; | |
2128 | ||
d8ed45c5 | 2129 | mmap_read_lock(mm); |
4b22927f | 2130 | vma = find_mergeable_vma(mm, rmap_item->address); |
56df70a6 MS |
2131 | if (vma) { |
2132 | err = try_to_merge_one_page(vma, page, | |
2133 | ZERO_PAGE(rmap_item->address)); | |
2134 | } else { | |
2135 | /* | |
2136 | * If the vma is out of date, we do not need to | |
2137 | * continue. | |
2138 | */ | |
2139 | err = 0; | |
2140 | } | |
d8ed45c5 | 2141 | mmap_read_unlock(mm); |
e86c59b1 CI |
2142 | /* |
2143 | * In case of failure, the page was not really empty, so we | |
2144 | * need to continue. Otherwise we're done. | |
2145 | */ | |
2146 | if (!err) | |
2147 | return; | |
2148 | } | |
8dd3557a HD |
2149 | tree_rmap_item = |
2150 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 2151 | if (tree_rmap_item) { |
77da2ba0 CI |
2152 | bool split; |
2153 | ||
8dd3557a HD |
2154 | kpage = try_to_merge_two_pages(rmap_item, page, |
2155 | tree_rmap_item, tree_page); | |
77da2ba0 CI |
2156 | /* |
2157 | * If both pages we tried to merge belong to the same compound | |
2158 | * page, then we actually ended up increasing the reference | |
2159 | * count of the same compound page twice, and split_huge_page | |
2160 | * failed. | |
2161 | * Here we set a flag if that happened, and we use it later to | |
2162 | * try split_huge_page again. Since we call put_page right | |
2163 | * afterwards, the reference count will be correct and | |
2164 | * split_huge_page should succeed. | |
2165 | */ | |
2166 | split = PageTransCompound(page) | |
2167 | && compound_head(page) == compound_head(tree_page); | |
8dd3557a | 2168 | put_page(tree_page); |
8dd3557a | 2169 | if (kpage) { |
bc56620b HD |
2170 | /* |
2171 | * The pages were successfully merged: insert new | |
2172 | * node in the stable tree and add both rmap_items. | |
2173 | */ | |
5ad64688 | 2174 | lock_page(kpage); |
7b6ba2c7 HD |
2175 | stable_node = stable_tree_insert(kpage); |
2176 | if (stable_node) { | |
2c653d0e AA |
2177 | stable_tree_append(tree_rmap_item, stable_node, |
2178 | false); | |
2179 | stable_tree_append(rmap_item, stable_node, | |
2180 | false); | |
7b6ba2c7 | 2181 | } |
5ad64688 | 2182 | unlock_page(kpage); |
7b6ba2c7 | 2183 | |
31dbd01f IE |
2184 | /* |
2185 | * If we fail to insert the page into the stable tree, | |
2186 | * we will have 2 virtual addresses that are pointing | |
2187 | * to a ksm page left outside the stable tree, | |
2188 | * in which case we need to break_cow on both. | |
2189 | */ | |
7b6ba2c7 | 2190 | if (!stable_node) { |
8dd3557a HD |
2191 | break_cow(tree_rmap_item); |
2192 | break_cow(rmap_item); | |
31dbd01f | 2193 | } |
77da2ba0 CI |
2194 | } else if (split) { |
2195 | /* | |
2196 | * We are here if we tried to merge two pages and | |
2197 | * failed because they both belonged to the same | |
2198 | * compound page. We will split the page now, but no | |
2199 | * merging will take place. | |
2200 | * We do not want to add the cost of a full lock; if | |
2201 | * the page is locked, it is better to skip it and | |
2202 | * perhaps try again later. | |
2203 | */ | |
2204 | if (!trylock_page(page)) | |
2205 | return; | |
2206 | split_huge_page(page); | |
2207 | unlock_page(page); | |
31dbd01f | 2208 | } |
31dbd01f IE |
2209 | } |
2210 | } | |
2211 | ||
2212 | static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, | |
6514d511 | 2213 | struct rmap_item **rmap_list, |
31dbd01f IE |
2214 | unsigned long addr) |
2215 | { | |
2216 | struct rmap_item *rmap_item; | |
2217 | ||
6514d511 HD |
2218 | while (*rmap_list) { |
2219 | rmap_item = *rmap_list; | |
93d17715 | 2220 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 2221 | return rmap_item; |
31dbd01f IE |
2222 | if (rmap_item->address > addr) |
2223 | break; | |
6514d511 | 2224 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 2225 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
2226 | free_rmap_item(rmap_item); |
2227 | } | |
2228 | ||
2229 | rmap_item = alloc_rmap_item(); | |
2230 | if (rmap_item) { | |
2231 | /* It has already been zeroed */ | |
2232 | rmap_item->mm = mm_slot->mm; | |
2233 | rmap_item->address = addr; | |
6514d511 HD |
2234 | rmap_item->rmap_list = *rmap_list; |
2235 | *rmap_list = rmap_item; | |
31dbd01f IE |
2236 | } |
2237 | return rmap_item; | |
2238 | } | |
2239 | ||
2240 | static struct rmap_item *scan_get_next_rmap_item(struct page **page) | |
2241 | { | |
2242 | struct mm_struct *mm; | |
2243 | struct mm_slot *slot; | |
2244 | struct vm_area_struct *vma; | |
2245 | struct rmap_item *rmap_item; | |
90bd6fd3 | 2246 | int nid; |
31dbd01f IE |
2247 | |
2248 | if (list_empty(&ksm_mm_head.mm_list)) | |
2249 | return NULL; | |
2250 | ||
2251 | slot = ksm_scan.mm_slot; | |
2252 | if (slot == &ksm_mm_head) { | |
2919bfd0 HD |
2253 | /* |
2254 | * A number of pages can hang around indefinitely on per-cpu | |
2255 | * pagevecs, raised page count preventing write_protect_page | |
2256 | * from merging them. Though it doesn't really matter much, | |
2257 | * it is puzzling to see some stuck in pages_volatile until | |
2258 | * other activity jostles them out, and they also prevented | |
2259 | * LTP's KSM test from succeeding deterministically; so drain | |
2260 | * them here (here rather than on entry to ksm_do_scan(), | |
2261 | * so we don't IPI too often when pages_to_scan is set low). | |
2262 | */ | |
2263 | lru_add_drain_all(); | |
2264 | ||
4146d2d6 HD |
2265 | /* |
2266 | * Whereas stale stable_nodes on the stable_tree itself | |
2267 | * get pruned in the regular course of stable_tree_search(), | |
2268 | * those moved out to the migrate_nodes list can accumulate: | |
2269 | * so prune them once before each full scan. | |
2270 | */ | |
2271 | if (!ksm_merge_across_nodes) { | |
03640418 | 2272 | struct stable_node *stable_node, *next; |
4146d2d6 HD |
2273 | struct page *page; |
2274 | ||
03640418 GT |
2275 | list_for_each_entry_safe(stable_node, next, |
2276 | &migrate_nodes, list) { | |
2cee57d1 YS |
2277 | page = get_ksm_page(stable_node, |
2278 | GET_KSM_PAGE_NOLOCK); | |
4146d2d6 HD |
2279 | if (page) |
2280 | put_page(page); | |
2281 | cond_resched(); | |
2282 | } | |
2283 | } | |
2284 | ||
ef53d16c | 2285 | for (nid = 0; nid < ksm_nr_node_ids; nid++) |
90bd6fd3 | 2286 | root_unstable_tree[nid] = RB_ROOT; |
31dbd01f IE |
2287 | |
2288 | spin_lock(&ksm_mmlist_lock); | |
2289 | slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); | |
2290 | ksm_scan.mm_slot = slot; | |
2291 | spin_unlock(&ksm_mmlist_lock); | |
2b472611 HD |
2292 | /* |
2293 | * Although we tested list_empty() above, a racing __ksm_exit | |
2294 | * of the last mm on the list may have removed it since then. | |
2295 | */ | |
2296 | if (slot == &ksm_mm_head) | |
2297 | return NULL; | |
31dbd01f IE |
2298 | next_mm: |
2299 | ksm_scan.address = 0; | |
6514d511 | 2300 | ksm_scan.rmap_list = &slot->rmap_list; |
31dbd01f IE |
2301 | } |
2302 | ||
2303 | mm = slot->mm; | |
d8ed45c5 | 2304 | mmap_read_lock(mm); |
9ba69294 HD |
2305 | if (ksm_test_exit(mm)) |
2306 | vma = NULL; | |
2307 | else | |
2308 | vma = find_vma(mm, ksm_scan.address); | |
2309 | ||
2310 | for (; vma; vma = vma->vm_next) { | |
31dbd01f IE |
2311 | if (!(vma->vm_flags & VM_MERGEABLE)) |
2312 | continue; | |
2313 | if (ksm_scan.address < vma->vm_start) | |
2314 | ksm_scan.address = vma->vm_start; | |
2315 | if (!vma->anon_vma) | |
2316 | ksm_scan.address = vma->vm_end; | |
2317 | ||
2318 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
2319 | if (ksm_test_exit(mm)) |
2320 | break; | |
31dbd01f | 2321 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
3218f871 | 2322 | if (IS_ERR_OR_NULL(*page) || is_zone_device_page(*page)) { |
21ae5b01 AA |
2323 | ksm_scan.address += PAGE_SIZE; |
2324 | cond_resched(); | |
2325 | continue; | |
2326 | } | |
f765f540 | 2327 | if (PageAnon(*page)) { |
31dbd01f IE |
2328 | flush_anon_page(vma, *page, ksm_scan.address); |
2329 | flush_dcache_page(*page); | |
2330 | rmap_item = get_next_rmap_item(slot, | |
6514d511 | 2331 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 2332 | if (rmap_item) { |
6514d511 HD |
2333 | ksm_scan.rmap_list = |
2334 | &rmap_item->rmap_list; | |
31dbd01f IE |
2335 | ksm_scan.address += PAGE_SIZE; |
2336 | } else | |
2337 | put_page(*page); | |
d8ed45c5 | 2338 | mmap_read_unlock(mm); |
31dbd01f IE |
2339 | return rmap_item; |
2340 | } | |
21ae5b01 | 2341 | put_page(*page); |
31dbd01f IE |
2342 | ksm_scan.address += PAGE_SIZE; |
2343 | cond_resched(); | |
2344 | } | |
2345 | } | |
2346 | ||
9ba69294 HD |
2347 | if (ksm_test_exit(mm)) { |
2348 | ksm_scan.address = 0; | |
6514d511 | 2349 | ksm_scan.rmap_list = &slot->rmap_list; |
9ba69294 | 2350 | } |
31dbd01f IE |
2351 | /* |
2352 | * Nuke all the rmap_items that are above this current rmap: | |
2353 | * because there were no VM_MERGEABLE vmas with such addresses. | |
2354 | */ | |
420be4ed | 2355 | remove_trailing_rmap_items(ksm_scan.rmap_list); |
31dbd01f IE |
2356 | |
2357 | spin_lock(&ksm_mmlist_lock); | |
cd551f97 HD |
2358 | ksm_scan.mm_slot = list_entry(slot->mm_list.next, |
2359 | struct mm_slot, mm_list); | |
2360 | if (ksm_scan.address == 0) { | |
2361 | /* | |
c1e8d7c6 | 2362 | * We've completed a full scan of all vmas, holding mmap_lock |
cd551f97 HD |
2363 | * throughout, and found no VM_MERGEABLE: so do the same as |
2364 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
2365 | * This applies either when cleaning up after __ksm_exit |
2366 | * (but beware: we can reach here even before __ksm_exit), | |
2367 | * or when all VM_MERGEABLE areas have been unmapped (and | |
c1e8d7c6 | 2368 | * mmap_lock then protects against race with MADV_MERGEABLE). |
cd551f97 | 2369 | */ |
4ca3a69b | 2370 | hash_del(&slot->link); |
cd551f97 | 2371 | list_del(&slot->mm_list); |
9ba69294 HD |
2372 | spin_unlock(&ksm_mmlist_lock); |
2373 | ||
cd551f97 HD |
2374 | free_mm_slot(slot); |
2375 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
d8ed45c5 | 2376 | mmap_read_unlock(mm); |
9ba69294 HD |
2377 | mmdrop(mm); |
2378 | } else { | |
d8ed45c5 | 2379 | mmap_read_unlock(mm); |
7496fea9 | 2380 | /* |
3e4e28c5 | 2381 | * mmap_read_unlock(mm) first because after |
7496fea9 ZC |
2382 | * spin_unlock(&ksm_mmlist_lock) run, the "mm" may |
2383 | * already have been freed under us by __ksm_exit() | |
2384 | * because the "mm_slot" is still hashed and | |
2385 | * ksm_scan.mm_slot doesn't point to it anymore. | |
2386 | */ | |
2387 | spin_unlock(&ksm_mmlist_lock); | |
cd551f97 | 2388 | } |
31dbd01f IE |
2389 | |
2390 | /* Repeat until we've completed scanning the whole list */ | |
cd551f97 | 2391 | slot = ksm_scan.mm_slot; |
31dbd01f IE |
2392 | if (slot != &ksm_mm_head) |
2393 | goto next_mm; | |
2394 | ||
31dbd01f IE |
2395 | ksm_scan.seqnr++; |
2396 | return NULL; | |
2397 | } | |
2398 | ||
2399 | /** | |
2400 | * ksm_do_scan - the ksm scanner main worker function. | |
b7701a5f | 2401 | * @scan_npages: number of pages we want to scan before we return. |
31dbd01f IE |
2402 | */ |
2403 | static void ksm_do_scan(unsigned int scan_npages) | |
2404 | { | |
2405 | struct rmap_item *rmap_item; | |
3f649ab7 | 2406 | struct page *page; |
31dbd01f | 2407 | |
878aee7d | 2408 | while (scan_npages-- && likely(!freezing(current))) { |
31dbd01f IE |
2409 | cond_resched(); |
2410 | rmap_item = scan_get_next_rmap_item(&page); | |
2411 | if (!rmap_item) | |
2412 | return; | |
4146d2d6 | 2413 | cmp_and_merge_page(page, rmap_item); |
31dbd01f IE |
2414 | put_page(page); |
2415 | } | |
2416 | } | |
2417 | ||
6e158384 HD |
2418 | static int ksmd_should_run(void) |
2419 | { | |
2420 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list); | |
2421 | } | |
2422 | ||
31dbd01f IE |
2423 | static int ksm_scan_thread(void *nothing) |
2424 | { | |
fcf9a0ef KT |
2425 | unsigned int sleep_ms; |
2426 | ||
878aee7d | 2427 | set_freezable(); |
339aa624 | 2428 | set_user_nice(current, 5); |
31dbd01f IE |
2429 | |
2430 | while (!kthread_should_stop()) { | |
6e158384 | 2431 | mutex_lock(&ksm_thread_mutex); |
ef4d43a8 | 2432 | wait_while_offlining(); |
6e158384 | 2433 | if (ksmd_should_run()) |
31dbd01f | 2434 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
2435 | mutex_unlock(&ksm_thread_mutex); |
2436 | ||
878aee7d AA |
2437 | try_to_freeze(); |
2438 | ||
6e158384 | 2439 | if (ksmd_should_run()) { |
fcf9a0ef KT |
2440 | sleep_ms = READ_ONCE(ksm_thread_sleep_millisecs); |
2441 | wait_event_interruptible_timeout(ksm_iter_wait, | |
2442 | sleep_ms != READ_ONCE(ksm_thread_sleep_millisecs), | |
2443 | msecs_to_jiffies(sleep_ms)); | |
31dbd01f | 2444 | } else { |
878aee7d | 2445 | wait_event_freezable(ksm_thread_wait, |
6e158384 | 2446 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
2447 | } |
2448 | } | |
2449 | return 0; | |
2450 | } | |
2451 | ||
f8af4da3 HD |
2452 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
2453 | unsigned long end, int advice, unsigned long *vm_flags) | |
2454 | { | |
2455 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 2456 | int err; |
f8af4da3 HD |
2457 | |
2458 | switch (advice) { | |
2459 | case MADV_MERGEABLE: | |
2460 | /* | |
2461 | * Be somewhat over-protective for now! | |
2462 | */ | |
2463 | if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | | |
2464 | VM_PFNMAP | VM_IO | VM_DONTEXPAND | | |
0661a336 | 2465 | VM_HUGETLB | VM_MIXEDMAP)) |
f8af4da3 HD |
2466 | return 0; /* just ignore the advice */ |
2467 | ||
e1fb4a08 DJ |
2468 | if (vma_is_dax(vma)) |
2469 | return 0; | |
2470 | ||
12564485 SA |
2471 | #ifdef VM_SAO |
2472 | if (*vm_flags & VM_SAO) | |
2473 | return 0; | |
2474 | #endif | |
74a04967 KA |
2475 | #ifdef VM_SPARC_ADI |
2476 | if (*vm_flags & VM_SPARC_ADI) | |
2477 | return 0; | |
2478 | #endif | |
cc2383ec | 2479 | |
d952b791 HD |
2480 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
2481 | err = __ksm_enter(mm); | |
2482 | if (err) | |
2483 | return err; | |
2484 | } | |
f8af4da3 HD |
2485 | |
2486 | *vm_flags |= VM_MERGEABLE; | |
2487 | break; | |
2488 | ||
2489 | case MADV_UNMERGEABLE: | |
2490 | if (!(*vm_flags & VM_MERGEABLE)) | |
2491 | return 0; /* just ignore the advice */ | |
2492 | ||
d952b791 HD |
2493 | if (vma->anon_vma) { |
2494 | err = unmerge_ksm_pages(vma, start, end); | |
2495 | if (err) | |
2496 | return err; | |
2497 | } | |
f8af4da3 HD |
2498 | |
2499 | *vm_flags &= ~VM_MERGEABLE; | |
2500 | break; | |
2501 | } | |
2502 | ||
2503 | return 0; | |
2504 | } | |
33cf1707 | 2505 | EXPORT_SYMBOL_GPL(ksm_madvise); |
f8af4da3 HD |
2506 | |
2507 | int __ksm_enter(struct mm_struct *mm) | |
2508 | { | |
6e158384 HD |
2509 | struct mm_slot *mm_slot; |
2510 | int needs_wakeup; | |
2511 | ||
2512 | mm_slot = alloc_mm_slot(); | |
31dbd01f IE |
2513 | if (!mm_slot) |
2514 | return -ENOMEM; | |
2515 | ||
6e158384 HD |
2516 | /* Check ksm_run too? Would need tighter locking */ |
2517 | needs_wakeup = list_empty(&ksm_mm_head.mm_list); | |
2518 | ||
31dbd01f IE |
2519 | spin_lock(&ksm_mmlist_lock); |
2520 | insert_to_mm_slots_hash(mm, mm_slot); | |
2521 | /* | |
cbf86cfe HD |
2522 | * When KSM_RUN_MERGE (or KSM_RUN_STOP), |
2523 | * insert just behind the scanning cursor, to let the area settle | |
31dbd01f IE |
2524 | * down a little; when fork is followed by immediate exec, we don't |
2525 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
cbf86cfe HD |
2526 | * |
2527 | * But when KSM_RUN_UNMERGE, it's important to insert ahead of its | |
2528 | * scanning cursor, otherwise KSM pages in newly forked mms will be | |
2529 | * missed: then we might as well insert at the end of the list. | |
31dbd01f | 2530 | */ |
cbf86cfe HD |
2531 | if (ksm_run & KSM_RUN_UNMERGE) |
2532 | list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list); | |
2533 | else | |
2534 | list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list); | |
31dbd01f IE |
2535 | spin_unlock(&ksm_mmlist_lock); |
2536 | ||
f8af4da3 | 2537 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
f1f10076 | 2538 | mmgrab(mm); |
6e158384 HD |
2539 | |
2540 | if (needs_wakeup) | |
2541 | wake_up_interruptible(&ksm_thread_wait); | |
2542 | ||
f8af4da3 HD |
2543 | return 0; |
2544 | } | |
2545 | ||
1c2fb7a4 | 2546 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 2547 | { |
cd551f97 | 2548 | struct mm_slot *mm_slot; |
9ba69294 | 2549 | int easy_to_free = 0; |
cd551f97 | 2550 | |
31dbd01f | 2551 | /* |
9ba69294 HD |
2552 | * This process is exiting: if it's straightforward (as is the |
2553 | * case when ksmd was never running), free mm_slot immediately. | |
2554 | * But if it's at the cursor or has rmap_items linked to it, use | |
c1e8d7c6 | 2555 | * mmap_lock to synchronize with any break_cows before pagetables |
9ba69294 HD |
2556 | * are freed, and leave the mm_slot on the list for ksmd to free. |
2557 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 2558 | */ |
9ba69294 | 2559 | |
cd551f97 HD |
2560 | spin_lock(&ksm_mmlist_lock); |
2561 | mm_slot = get_mm_slot(mm); | |
9ba69294 | 2562 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 2563 | if (!mm_slot->rmap_list) { |
4ca3a69b | 2564 | hash_del(&mm_slot->link); |
9ba69294 HD |
2565 | list_del(&mm_slot->mm_list); |
2566 | easy_to_free = 1; | |
2567 | } else { | |
2568 | list_move(&mm_slot->mm_list, | |
2569 | &ksm_scan.mm_slot->mm_list); | |
2570 | } | |
cd551f97 | 2571 | } |
cd551f97 HD |
2572 | spin_unlock(&ksm_mmlist_lock); |
2573 | ||
9ba69294 HD |
2574 | if (easy_to_free) { |
2575 | free_mm_slot(mm_slot); | |
2576 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); | |
2577 | mmdrop(mm); | |
2578 | } else if (mm_slot) { | |
d8ed45c5 ML |
2579 | mmap_write_lock(mm); |
2580 | mmap_write_unlock(mm); | |
9ba69294 | 2581 | } |
31dbd01f IE |
2582 | } |
2583 | ||
cbf86cfe | 2584 | struct page *ksm_might_need_to_copy(struct page *page, |
5ad64688 HD |
2585 | struct vm_area_struct *vma, unsigned long address) |
2586 | { | |
e05b3453 MWO |
2587 | struct folio *folio = page_folio(page); |
2588 | struct anon_vma *anon_vma = folio_anon_vma(folio); | |
5ad64688 HD |
2589 | struct page *new_page; |
2590 | ||
cbf86cfe HD |
2591 | if (PageKsm(page)) { |
2592 | if (page_stable_node(page) && | |
2593 | !(ksm_run & KSM_RUN_UNMERGE)) | |
2594 | return page; /* no need to copy it */ | |
2595 | } else if (!anon_vma) { | |
2596 | return page; /* no need to copy it */ | |
e1c63e11 NS |
2597 | } else if (page->index == linear_page_index(vma, address) && |
2598 | anon_vma->root == vma->anon_vma->root) { | |
cbf86cfe HD |
2599 | return page; /* still no need to copy it */ |
2600 | } | |
2601 | if (!PageUptodate(page)) | |
2602 | return page; /* let do_swap_page report the error */ | |
2603 | ||
5ad64688 | 2604 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
8f425e4e MWO |
2605 | if (new_page && |
2606 | mem_cgroup_charge(page_folio(new_page), vma->vm_mm, GFP_KERNEL)) { | |
62fdb163 HD |
2607 | put_page(new_page); |
2608 | new_page = NULL; | |
2609 | } | |
5ad64688 HD |
2610 | if (new_page) { |
2611 | copy_user_highpage(new_page, page, address, vma); | |
2612 | ||
2613 | SetPageDirty(new_page); | |
2614 | __SetPageUptodate(new_page); | |
48c935ad | 2615 | __SetPageLocked(new_page); |
4d45c3af YY |
2616 | #ifdef CONFIG_SWAP |
2617 | count_vm_event(KSM_SWPIN_COPY); | |
2618 | #endif | |
5ad64688 HD |
2619 | } |
2620 | ||
5ad64688 HD |
2621 | return new_page; |
2622 | } | |
2623 | ||
6d4675e6 | 2624 | void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc) |
e9995ef9 HD |
2625 | { |
2626 | struct stable_node *stable_node; | |
e9995ef9 | 2627 | struct rmap_item *rmap_item; |
e9995ef9 HD |
2628 | int search_new_forks = 0; |
2629 | ||
2f031c6f | 2630 | VM_BUG_ON_FOLIO(!folio_test_ksm(folio), folio); |
9f32624b JK |
2631 | |
2632 | /* | |
2633 | * Rely on the page lock to protect against concurrent modifications | |
2634 | * to that page's node of the stable tree. | |
2635 | */ | |
2f031c6f | 2636 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
e9995ef9 | 2637 | |
2f031c6f | 2638 | stable_node = folio_stable_node(folio); |
e9995ef9 | 2639 | if (!stable_node) |
1df631ae | 2640 | return; |
e9995ef9 | 2641 | again: |
b67bfe0d | 2642 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
e9995ef9 | 2643 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 2644 | struct anon_vma_chain *vmac; |
e9995ef9 HD |
2645 | struct vm_area_struct *vma; |
2646 | ||
ad12695f | 2647 | cond_resched(); |
6d4675e6 MK |
2648 | if (!anon_vma_trylock_read(anon_vma)) { |
2649 | if (rwc->try_lock) { | |
2650 | rwc->contended = true; | |
2651 | return; | |
2652 | } | |
2653 | anon_vma_lock_read(anon_vma); | |
2654 | } | |
bf181b9f ML |
2655 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
2656 | 0, ULONG_MAX) { | |
1105a2fc JH |
2657 | unsigned long addr; |
2658 | ||
ad12695f | 2659 | cond_resched(); |
5beb4930 | 2660 | vma = vmac->vma; |
1105a2fc JH |
2661 | |
2662 | /* Ignore the stable/unstable/sqnr flags */ | |
cd7fae26 | 2663 | addr = rmap_item->address & PAGE_MASK; |
1105a2fc JH |
2664 | |
2665 | if (addr < vma->vm_start || addr >= vma->vm_end) | |
e9995ef9 HD |
2666 | continue; |
2667 | /* | |
2668 | * Initially we examine only the vma which covers this | |
2669 | * rmap_item; but later, if there is still work to do, | |
2670 | * we examine covering vmas in other mms: in case they | |
2671 | * were forked from the original since ksmd passed. | |
2672 | */ | |
2673 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
2674 | continue; | |
2675 | ||
0dd1c7bb JK |
2676 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
2677 | continue; | |
2678 | ||
2f031c6f | 2679 | if (!rwc->rmap_one(folio, vma, addr, rwc->arg)) { |
b6b19f25 | 2680 | anon_vma_unlock_read(anon_vma); |
1df631ae | 2681 | return; |
e9995ef9 | 2682 | } |
2f031c6f | 2683 | if (rwc->done && rwc->done(folio)) { |
0dd1c7bb | 2684 | anon_vma_unlock_read(anon_vma); |
1df631ae | 2685 | return; |
0dd1c7bb | 2686 | } |
e9995ef9 | 2687 | } |
b6b19f25 | 2688 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
2689 | } |
2690 | if (!search_new_forks++) | |
2691 | goto again; | |
e9995ef9 HD |
2692 | } |
2693 | ||
52629506 | 2694 | #ifdef CONFIG_MIGRATION |
19138349 | 2695 | void folio_migrate_ksm(struct folio *newfolio, struct folio *folio) |
e9995ef9 HD |
2696 | { |
2697 | struct stable_node *stable_node; | |
2698 | ||
19138349 MWO |
2699 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
2700 | VM_BUG_ON_FOLIO(!folio_test_locked(newfolio), newfolio); | |
2701 | VM_BUG_ON_FOLIO(newfolio->mapping != folio->mapping, newfolio); | |
e9995ef9 | 2702 | |
19138349 | 2703 | stable_node = folio_stable_node(folio); |
e9995ef9 | 2704 | if (stable_node) { |
19138349 MWO |
2705 | VM_BUG_ON_FOLIO(stable_node->kpfn != folio_pfn(folio), folio); |
2706 | stable_node->kpfn = folio_pfn(newfolio); | |
c8d6553b | 2707 | /* |
19138349 | 2708 | * newfolio->mapping was set in advance; now we need smp_wmb() |
c8d6553b | 2709 | * to make sure that the new stable_node->kpfn is visible |
19138349 MWO |
2710 | * to get_ksm_page() before it can see that folio->mapping |
2711 | * has gone stale (or that folio_test_swapcache has been cleared). | |
c8d6553b HD |
2712 | */ |
2713 | smp_wmb(); | |
19138349 | 2714 | set_page_stable_node(&folio->page, NULL); |
e9995ef9 HD |
2715 | } |
2716 | } | |
2717 | #endif /* CONFIG_MIGRATION */ | |
2718 | ||
62b61f61 | 2719 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 HD |
2720 | static void wait_while_offlining(void) |
2721 | { | |
2722 | while (ksm_run & KSM_RUN_OFFLINE) { | |
2723 | mutex_unlock(&ksm_thread_mutex); | |
2724 | wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), | |
74316201 | 2725 | TASK_UNINTERRUPTIBLE); |
ef4d43a8 HD |
2726 | mutex_lock(&ksm_thread_mutex); |
2727 | } | |
2728 | } | |
2729 | ||
2c653d0e AA |
2730 | static bool stable_node_dup_remove_range(struct stable_node *stable_node, |
2731 | unsigned long start_pfn, | |
2732 | unsigned long end_pfn) | |
2733 | { | |
2734 | if (stable_node->kpfn >= start_pfn && | |
2735 | stable_node->kpfn < end_pfn) { | |
2736 | /* | |
2737 | * Don't get_ksm_page, page has already gone: | |
2738 | * which is why we keep kpfn instead of page* | |
2739 | */ | |
2740 | remove_node_from_stable_tree(stable_node); | |
2741 | return true; | |
2742 | } | |
2743 | return false; | |
2744 | } | |
2745 | ||
2746 | static bool stable_node_chain_remove_range(struct stable_node *stable_node, | |
2747 | unsigned long start_pfn, | |
2748 | unsigned long end_pfn, | |
2749 | struct rb_root *root) | |
2750 | { | |
2751 | struct stable_node *dup; | |
2752 | struct hlist_node *hlist_safe; | |
2753 | ||
2754 | if (!is_stable_node_chain(stable_node)) { | |
2755 | VM_BUG_ON(is_stable_node_dup(stable_node)); | |
2756 | return stable_node_dup_remove_range(stable_node, start_pfn, | |
2757 | end_pfn); | |
2758 | } | |
2759 | ||
2760 | hlist_for_each_entry_safe(dup, hlist_safe, | |
2761 | &stable_node->hlist, hlist_dup) { | |
2762 | VM_BUG_ON(!is_stable_node_dup(dup)); | |
2763 | stable_node_dup_remove_range(dup, start_pfn, end_pfn); | |
2764 | } | |
2765 | if (hlist_empty(&stable_node->hlist)) { | |
2766 | free_stable_node_chain(stable_node, root); | |
2767 | return true; /* notify caller that tree was rebalanced */ | |
2768 | } else | |
2769 | return false; | |
2770 | } | |
2771 | ||
ee0ea59c HD |
2772 | static void ksm_check_stable_tree(unsigned long start_pfn, |
2773 | unsigned long end_pfn) | |
62b61f61 | 2774 | { |
03640418 | 2775 | struct stable_node *stable_node, *next; |
62b61f61 | 2776 | struct rb_node *node; |
90bd6fd3 | 2777 | int nid; |
62b61f61 | 2778 | |
ef53d16c HD |
2779 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
2780 | node = rb_first(root_stable_tree + nid); | |
ee0ea59c | 2781 | while (node) { |
90bd6fd3 | 2782 | stable_node = rb_entry(node, struct stable_node, node); |
2c653d0e AA |
2783 | if (stable_node_chain_remove_range(stable_node, |
2784 | start_pfn, end_pfn, | |
2785 | root_stable_tree + | |
2786 | nid)) | |
ef53d16c | 2787 | node = rb_first(root_stable_tree + nid); |
2c653d0e | 2788 | else |
ee0ea59c HD |
2789 | node = rb_next(node); |
2790 | cond_resched(); | |
90bd6fd3 | 2791 | } |
ee0ea59c | 2792 | } |
03640418 | 2793 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
2794 | if (stable_node->kpfn >= start_pfn && |
2795 | stable_node->kpfn < end_pfn) | |
2796 | remove_node_from_stable_tree(stable_node); | |
2797 | cond_resched(); | |
2798 | } | |
62b61f61 HD |
2799 | } |
2800 | ||
2801 | static int ksm_memory_callback(struct notifier_block *self, | |
2802 | unsigned long action, void *arg) | |
2803 | { | |
2804 | struct memory_notify *mn = arg; | |
62b61f61 HD |
2805 | |
2806 | switch (action) { | |
2807 | case MEM_GOING_OFFLINE: | |
2808 | /* | |
ef4d43a8 HD |
2809 | * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() |
2810 | * and remove_all_stable_nodes() while memory is going offline: | |
2811 | * it is unsafe for them to touch the stable tree at this time. | |
2812 | * But unmerge_ksm_pages(), rmap lookups and other entry points | |
2813 | * which do not need the ksm_thread_mutex are all safe. | |
62b61f61 | 2814 | */ |
ef4d43a8 HD |
2815 | mutex_lock(&ksm_thread_mutex); |
2816 | ksm_run |= KSM_RUN_OFFLINE; | |
2817 | mutex_unlock(&ksm_thread_mutex); | |
62b61f61 HD |
2818 | break; |
2819 | ||
2820 | case MEM_OFFLINE: | |
2821 | /* | |
2822 | * Most of the work is done by page migration; but there might | |
2823 | * be a few stable_nodes left over, still pointing to struct | |
ee0ea59c HD |
2824 | * pages which have been offlined: prune those from the tree, |
2825 | * otherwise get_ksm_page() might later try to access a | |
2826 | * non-existent struct page. | |
62b61f61 | 2827 | */ |
ee0ea59c HD |
2828 | ksm_check_stable_tree(mn->start_pfn, |
2829 | mn->start_pfn + mn->nr_pages); | |
e4a9bc58 | 2830 | fallthrough; |
62b61f61 | 2831 | case MEM_CANCEL_OFFLINE: |
ef4d43a8 HD |
2832 | mutex_lock(&ksm_thread_mutex); |
2833 | ksm_run &= ~KSM_RUN_OFFLINE; | |
62b61f61 | 2834 | mutex_unlock(&ksm_thread_mutex); |
ef4d43a8 HD |
2835 | |
2836 | smp_mb(); /* wake_up_bit advises this */ | |
2837 | wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); | |
62b61f61 HD |
2838 | break; |
2839 | } | |
2840 | return NOTIFY_OK; | |
2841 | } | |
ef4d43a8 HD |
2842 | #else |
2843 | static void wait_while_offlining(void) | |
2844 | { | |
2845 | } | |
62b61f61 HD |
2846 | #endif /* CONFIG_MEMORY_HOTREMOVE */ |
2847 | ||
2ffd8679 HD |
2848 | #ifdef CONFIG_SYSFS |
2849 | /* | |
2850 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
2851 | */ | |
2852 | ||
31dbd01f IE |
2853 | #define KSM_ATTR_RO(_name) \ |
2854 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
2855 | #define KSM_ATTR(_name) \ | |
1bad2e5c | 2856 | static struct kobj_attribute _name##_attr = __ATTR_RW(_name) |
31dbd01f IE |
2857 | |
2858 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
2859 | struct kobj_attribute *attr, char *buf) | |
2860 | { | |
ae7a927d | 2861 | return sysfs_emit(buf, "%u\n", ksm_thread_sleep_millisecs); |
31dbd01f IE |
2862 | } |
2863 | ||
2864 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
2865 | struct kobj_attribute *attr, | |
2866 | const char *buf, size_t count) | |
2867 | { | |
dfefd226 | 2868 | unsigned int msecs; |
31dbd01f IE |
2869 | int err; |
2870 | ||
dfefd226 AD |
2871 | err = kstrtouint(buf, 10, &msecs); |
2872 | if (err) | |
31dbd01f IE |
2873 | return -EINVAL; |
2874 | ||
2875 | ksm_thread_sleep_millisecs = msecs; | |
fcf9a0ef | 2876 | wake_up_interruptible(&ksm_iter_wait); |
31dbd01f IE |
2877 | |
2878 | return count; | |
2879 | } | |
2880 | KSM_ATTR(sleep_millisecs); | |
2881 | ||
2882 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
2883 | struct kobj_attribute *attr, char *buf) | |
2884 | { | |
ae7a927d | 2885 | return sysfs_emit(buf, "%u\n", ksm_thread_pages_to_scan); |
31dbd01f IE |
2886 | } |
2887 | ||
2888 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
2889 | struct kobj_attribute *attr, | |
2890 | const char *buf, size_t count) | |
2891 | { | |
dfefd226 | 2892 | unsigned int nr_pages; |
31dbd01f | 2893 | int err; |
31dbd01f | 2894 | |
dfefd226 AD |
2895 | err = kstrtouint(buf, 10, &nr_pages); |
2896 | if (err) | |
31dbd01f IE |
2897 | return -EINVAL; |
2898 | ||
2899 | ksm_thread_pages_to_scan = nr_pages; | |
2900 | ||
2901 | return count; | |
2902 | } | |
2903 | KSM_ATTR(pages_to_scan); | |
2904 | ||
2905 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
2906 | char *buf) | |
2907 | { | |
ae7a927d | 2908 | return sysfs_emit(buf, "%lu\n", ksm_run); |
31dbd01f IE |
2909 | } |
2910 | ||
2911 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
2912 | const char *buf, size_t count) | |
2913 | { | |
dfefd226 | 2914 | unsigned int flags; |
31dbd01f | 2915 | int err; |
31dbd01f | 2916 | |
dfefd226 AD |
2917 | err = kstrtouint(buf, 10, &flags); |
2918 | if (err) | |
31dbd01f IE |
2919 | return -EINVAL; |
2920 | if (flags > KSM_RUN_UNMERGE) | |
2921 | return -EINVAL; | |
2922 | ||
2923 | /* | |
2924 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
2925 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
d0f209f6 HD |
2926 | * breaking COW to free the pages_shared (but leaves mm_slots |
2927 | * on the list for when ksmd may be set running again). | |
31dbd01f IE |
2928 | */ |
2929 | ||
2930 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2931 | wait_while_offlining(); |
31dbd01f IE |
2932 | if (ksm_run != flags) { |
2933 | ksm_run = flags; | |
d952b791 | 2934 | if (flags & KSM_RUN_UNMERGE) { |
e1e12d2f | 2935 | set_current_oom_origin(); |
d952b791 | 2936 | err = unmerge_and_remove_all_rmap_items(); |
e1e12d2f | 2937 | clear_current_oom_origin(); |
d952b791 HD |
2938 | if (err) { |
2939 | ksm_run = KSM_RUN_STOP; | |
2940 | count = err; | |
2941 | } | |
2942 | } | |
31dbd01f IE |
2943 | } |
2944 | mutex_unlock(&ksm_thread_mutex); | |
2945 | ||
2946 | if (flags & KSM_RUN_MERGE) | |
2947 | wake_up_interruptible(&ksm_thread_wait); | |
2948 | ||
2949 | return count; | |
2950 | } | |
2951 | KSM_ATTR(run); | |
2952 | ||
90bd6fd3 PH |
2953 | #ifdef CONFIG_NUMA |
2954 | static ssize_t merge_across_nodes_show(struct kobject *kobj, | |
ae7a927d | 2955 | struct kobj_attribute *attr, char *buf) |
90bd6fd3 | 2956 | { |
ae7a927d | 2957 | return sysfs_emit(buf, "%u\n", ksm_merge_across_nodes); |
90bd6fd3 PH |
2958 | } |
2959 | ||
2960 | static ssize_t merge_across_nodes_store(struct kobject *kobj, | |
2961 | struct kobj_attribute *attr, | |
2962 | const char *buf, size_t count) | |
2963 | { | |
2964 | int err; | |
2965 | unsigned long knob; | |
2966 | ||
2967 | err = kstrtoul(buf, 10, &knob); | |
2968 | if (err) | |
2969 | return err; | |
2970 | if (knob > 1) | |
2971 | return -EINVAL; | |
2972 | ||
2973 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 2974 | wait_while_offlining(); |
90bd6fd3 | 2975 | if (ksm_merge_across_nodes != knob) { |
cbf86cfe | 2976 | if (ksm_pages_shared || remove_all_stable_nodes()) |
90bd6fd3 | 2977 | err = -EBUSY; |
ef53d16c HD |
2978 | else if (root_stable_tree == one_stable_tree) { |
2979 | struct rb_root *buf; | |
2980 | /* | |
2981 | * This is the first time that we switch away from the | |
2982 | * default of merging across nodes: must now allocate | |
2983 | * a buffer to hold as many roots as may be needed. | |
2984 | * Allocate stable and unstable together: | |
2985 | * MAXSMP NODES_SHIFT 10 will use 16kB. | |
2986 | */ | |
bafe1e14 JP |
2987 | buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf), |
2988 | GFP_KERNEL); | |
ef53d16c HD |
2989 | /* Let us assume that RB_ROOT is NULL is zero */ |
2990 | if (!buf) | |
2991 | err = -ENOMEM; | |
2992 | else { | |
2993 | root_stable_tree = buf; | |
2994 | root_unstable_tree = buf + nr_node_ids; | |
2995 | /* Stable tree is empty but not the unstable */ | |
2996 | root_unstable_tree[0] = one_unstable_tree[0]; | |
2997 | } | |
2998 | } | |
2999 | if (!err) { | |
90bd6fd3 | 3000 | ksm_merge_across_nodes = knob; |
ef53d16c HD |
3001 | ksm_nr_node_ids = knob ? 1 : nr_node_ids; |
3002 | } | |
90bd6fd3 PH |
3003 | } |
3004 | mutex_unlock(&ksm_thread_mutex); | |
3005 | ||
3006 | return err ? err : count; | |
3007 | } | |
3008 | KSM_ATTR(merge_across_nodes); | |
3009 | #endif | |
3010 | ||
e86c59b1 | 3011 | static ssize_t use_zero_pages_show(struct kobject *kobj, |
ae7a927d | 3012 | struct kobj_attribute *attr, char *buf) |
e86c59b1 | 3013 | { |
ae7a927d | 3014 | return sysfs_emit(buf, "%u\n", ksm_use_zero_pages); |
e86c59b1 CI |
3015 | } |
3016 | static ssize_t use_zero_pages_store(struct kobject *kobj, | |
3017 | struct kobj_attribute *attr, | |
3018 | const char *buf, size_t count) | |
3019 | { | |
3020 | int err; | |
3021 | bool value; | |
3022 | ||
3023 | err = kstrtobool(buf, &value); | |
3024 | if (err) | |
3025 | return -EINVAL; | |
3026 | ||
3027 | ksm_use_zero_pages = value; | |
3028 | ||
3029 | return count; | |
3030 | } | |
3031 | KSM_ATTR(use_zero_pages); | |
3032 | ||
2c653d0e AA |
3033 | static ssize_t max_page_sharing_show(struct kobject *kobj, |
3034 | struct kobj_attribute *attr, char *buf) | |
3035 | { | |
ae7a927d | 3036 | return sysfs_emit(buf, "%u\n", ksm_max_page_sharing); |
2c653d0e AA |
3037 | } |
3038 | ||
3039 | static ssize_t max_page_sharing_store(struct kobject *kobj, | |
3040 | struct kobj_attribute *attr, | |
3041 | const char *buf, size_t count) | |
3042 | { | |
3043 | int err; | |
3044 | int knob; | |
3045 | ||
3046 | err = kstrtoint(buf, 10, &knob); | |
3047 | if (err) | |
3048 | return err; | |
3049 | /* | |
3050 | * When a KSM page is created it is shared by 2 mappings. This | |
3051 | * being a signed comparison, it implicitly verifies it's not | |
3052 | * negative. | |
3053 | */ | |
3054 | if (knob < 2) | |
3055 | return -EINVAL; | |
3056 | ||
3057 | if (READ_ONCE(ksm_max_page_sharing) == knob) | |
3058 | return count; | |
3059 | ||
3060 | mutex_lock(&ksm_thread_mutex); | |
3061 | wait_while_offlining(); | |
3062 | if (ksm_max_page_sharing != knob) { | |
3063 | if (ksm_pages_shared || remove_all_stable_nodes()) | |
3064 | err = -EBUSY; | |
3065 | else | |
3066 | ksm_max_page_sharing = knob; | |
3067 | } | |
3068 | mutex_unlock(&ksm_thread_mutex); | |
3069 | ||
3070 | return err ? err : count; | |
3071 | } | |
3072 | KSM_ATTR(max_page_sharing); | |
3073 | ||
b4028260 HD |
3074 | static ssize_t pages_shared_show(struct kobject *kobj, |
3075 | struct kobj_attribute *attr, char *buf) | |
3076 | { | |
ae7a927d | 3077 | return sysfs_emit(buf, "%lu\n", ksm_pages_shared); |
b4028260 HD |
3078 | } |
3079 | KSM_ATTR_RO(pages_shared); | |
3080 | ||
3081 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
3082 | struct kobj_attribute *attr, char *buf) | |
3083 | { | |
ae7a927d | 3084 | return sysfs_emit(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
3085 | } |
3086 | KSM_ATTR_RO(pages_sharing); | |
3087 | ||
473b0ce4 HD |
3088 | static ssize_t pages_unshared_show(struct kobject *kobj, |
3089 | struct kobj_attribute *attr, char *buf) | |
3090 | { | |
ae7a927d | 3091 | return sysfs_emit(buf, "%lu\n", ksm_pages_unshared); |
473b0ce4 HD |
3092 | } |
3093 | KSM_ATTR_RO(pages_unshared); | |
3094 | ||
3095 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
3096 | struct kobj_attribute *attr, char *buf) | |
3097 | { | |
3098 | long ksm_pages_volatile; | |
3099 | ||
3100 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
3101 | - ksm_pages_sharing - ksm_pages_unshared; | |
3102 | /* | |
3103 | * It was not worth any locking to calculate that statistic, | |
3104 | * but it might therefore sometimes be negative: conceal that. | |
3105 | */ | |
3106 | if (ksm_pages_volatile < 0) | |
3107 | ksm_pages_volatile = 0; | |
ae7a927d | 3108 | return sysfs_emit(buf, "%ld\n", ksm_pages_volatile); |
473b0ce4 HD |
3109 | } |
3110 | KSM_ATTR_RO(pages_volatile); | |
3111 | ||
2c653d0e AA |
3112 | static ssize_t stable_node_dups_show(struct kobject *kobj, |
3113 | struct kobj_attribute *attr, char *buf) | |
3114 | { | |
ae7a927d | 3115 | return sysfs_emit(buf, "%lu\n", ksm_stable_node_dups); |
2c653d0e AA |
3116 | } |
3117 | KSM_ATTR_RO(stable_node_dups); | |
3118 | ||
3119 | static ssize_t stable_node_chains_show(struct kobject *kobj, | |
3120 | struct kobj_attribute *attr, char *buf) | |
3121 | { | |
ae7a927d | 3122 | return sysfs_emit(buf, "%lu\n", ksm_stable_node_chains); |
2c653d0e AA |
3123 | } |
3124 | KSM_ATTR_RO(stable_node_chains); | |
3125 | ||
3126 | static ssize_t | |
3127 | stable_node_chains_prune_millisecs_show(struct kobject *kobj, | |
3128 | struct kobj_attribute *attr, | |
3129 | char *buf) | |
3130 | { | |
ae7a927d | 3131 | return sysfs_emit(buf, "%u\n", ksm_stable_node_chains_prune_millisecs); |
2c653d0e AA |
3132 | } |
3133 | ||
3134 | static ssize_t | |
3135 | stable_node_chains_prune_millisecs_store(struct kobject *kobj, | |
3136 | struct kobj_attribute *attr, | |
3137 | const char *buf, size_t count) | |
3138 | { | |
584ff0df | 3139 | unsigned int msecs; |
2c653d0e AA |
3140 | int err; |
3141 | ||
584ff0df ZB |
3142 | err = kstrtouint(buf, 10, &msecs); |
3143 | if (err) | |
2c653d0e AA |
3144 | return -EINVAL; |
3145 | ||
3146 | ksm_stable_node_chains_prune_millisecs = msecs; | |
3147 | ||
3148 | return count; | |
3149 | } | |
3150 | KSM_ATTR(stable_node_chains_prune_millisecs); | |
3151 | ||
473b0ce4 HD |
3152 | static ssize_t full_scans_show(struct kobject *kobj, |
3153 | struct kobj_attribute *attr, char *buf) | |
3154 | { | |
ae7a927d | 3155 | return sysfs_emit(buf, "%lu\n", ksm_scan.seqnr); |
473b0ce4 HD |
3156 | } |
3157 | KSM_ATTR_RO(full_scans); | |
3158 | ||
31dbd01f IE |
3159 | static struct attribute *ksm_attrs[] = { |
3160 | &sleep_millisecs_attr.attr, | |
3161 | &pages_to_scan_attr.attr, | |
3162 | &run_attr.attr, | |
b4028260 HD |
3163 | &pages_shared_attr.attr, |
3164 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
3165 | &pages_unshared_attr.attr, |
3166 | &pages_volatile_attr.attr, | |
3167 | &full_scans_attr.attr, | |
90bd6fd3 PH |
3168 | #ifdef CONFIG_NUMA |
3169 | &merge_across_nodes_attr.attr, | |
3170 | #endif | |
2c653d0e AA |
3171 | &max_page_sharing_attr.attr, |
3172 | &stable_node_chains_attr.attr, | |
3173 | &stable_node_dups_attr.attr, | |
3174 | &stable_node_chains_prune_millisecs_attr.attr, | |
e86c59b1 | 3175 | &use_zero_pages_attr.attr, |
31dbd01f IE |
3176 | NULL, |
3177 | }; | |
3178 | ||
f907c26a | 3179 | static const struct attribute_group ksm_attr_group = { |
31dbd01f IE |
3180 | .attrs = ksm_attrs, |
3181 | .name = "ksm", | |
3182 | }; | |
2ffd8679 | 3183 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
3184 | |
3185 | static int __init ksm_init(void) | |
3186 | { | |
3187 | struct task_struct *ksm_thread; | |
3188 | int err; | |
3189 | ||
e86c59b1 CI |
3190 | /* The correct value depends on page size and endianness */ |
3191 | zero_checksum = calc_checksum(ZERO_PAGE(0)); | |
3192 | /* Default to false for backwards compatibility */ | |
3193 | ksm_use_zero_pages = false; | |
3194 | ||
31dbd01f IE |
3195 | err = ksm_slab_init(); |
3196 | if (err) | |
3197 | goto out; | |
3198 | ||
31dbd01f IE |
3199 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
3200 | if (IS_ERR(ksm_thread)) { | |
25acde31 | 3201 | pr_err("ksm: creating kthread failed\n"); |
31dbd01f | 3202 | err = PTR_ERR(ksm_thread); |
d9f8984c | 3203 | goto out_free; |
31dbd01f IE |
3204 | } |
3205 | ||
2ffd8679 | 3206 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
3207 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
3208 | if (err) { | |
25acde31 | 3209 | pr_err("ksm: register sysfs failed\n"); |
2ffd8679 | 3210 | kthread_stop(ksm_thread); |
d9f8984c | 3211 | goto out_free; |
31dbd01f | 3212 | } |
c73602ad HD |
3213 | #else |
3214 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
3215 | ||
2ffd8679 | 3216 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 3217 | |
62b61f61 | 3218 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 | 3219 | /* There is no significance to this priority 100 */ |
62b61f61 HD |
3220 | hotplug_memory_notifier(ksm_memory_callback, 100); |
3221 | #endif | |
31dbd01f IE |
3222 | return 0; |
3223 | ||
d9f8984c | 3224 | out_free: |
31dbd01f IE |
3225 | ksm_slab_free(); |
3226 | out: | |
3227 | return err; | |
f8af4da3 | 3228 | } |
a64fb3cd | 3229 | subsys_initcall(ksm_init); |