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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> |
d7c0e68d | 42 | #include <linux/pagewalk.h> |
f8af4da3 | 43 | |
31dbd01f | 44 | #include <asm/tlbflush.h> |
73848b46 | 45 | #include "internal.h" |
58730ab6 | 46 | #include "mm_slot.h" |
31dbd01f | 47 | |
739100c8 SR |
48 | #define CREATE_TRACE_POINTS |
49 | #include <trace/events/ksm.h> | |
50 | ||
e850dcf5 HD |
51 | #ifdef CONFIG_NUMA |
52 | #define NUMA(x) (x) | |
53 | #define DO_NUMA(x) do { (x); } while (0) | |
54 | #else | |
55 | #define NUMA(x) (0) | |
56 | #define DO_NUMA(x) do { } while (0) | |
57 | #endif | |
58 | ||
5a2ca3ef MR |
59 | /** |
60 | * DOC: Overview | |
61 | * | |
31dbd01f IE |
62 | * A few notes about the KSM scanning process, |
63 | * to make it easier to understand the data structures below: | |
64 | * | |
65 | * In order to reduce excessive scanning, KSM sorts the memory pages by their | |
66 | * contents into a data structure that holds pointers to the pages' locations. | |
67 | * | |
68 | * Since the contents of the pages may change at any moment, KSM cannot just | |
69 | * insert the pages into a normal sorted tree and expect it to find anything. | |
70 | * Therefore KSM uses two data structures - the stable and the unstable tree. | |
71 | * | |
72 | * The stable tree holds pointers to all the merged pages (ksm pages), sorted | |
73 | * by their contents. Because each such page is write-protected, searching on | |
74 | * this tree is fully assured to be working (except when pages are unmapped), | |
75 | * and therefore this tree is called the stable tree. | |
76 | * | |
5a2ca3ef MR |
77 | * The stable tree node includes information required for reverse |
78 | * mapping from a KSM page to virtual addresses that map this page. | |
79 | * | |
80 | * In order to avoid large latencies of the rmap walks on KSM pages, | |
81 | * KSM maintains two types of nodes in the stable tree: | |
82 | * | |
83 | * * the regular nodes that keep the reverse mapping structures in a | |
84 | * linked list | |
85 | * * the "chains" that link nodes ("dups") that represent the same | |
86 | * write protected memory content, but each "dup" corresponds to a | |
87 | * different KSM page copy of that content | |
88 | * | |
89 | * Internally, the regular nodes, "dups" and "chains" are represented | |
21fbd591 | 90 | * using the same struct ksm_stable_node structure. |
5a2ca3ef | 91 | * |
31dbd01f IE |
92 | * In addition to the stable tree, KSM uses a second data structure called the |
93 | * unstable tree: this tree holds pointers to pages which have been found to | |
94 | * be "unchanged for a period of time". The unstable tree sorts these pages | |
95 | * by their contents, but since they are not write-protected, KSM cannot rely | |
96 | * upon the unstable tree to work correctly - the unstable tree is liable to | |
97 | * be corrupted as its contents are modified, and so it is called unstable. | |
98 | * | |
99 | * KSM solves this problem by several techniques: | |
100 | * | |
101 | * 1) The unstable tree is flushed every time KSM completes scanning all | |
102 | * memory areas, and then the tree is rebuilt again from the beginning. | |
103 | * 2) KSM will only insert into the unstable tree, pages whose hash value | |
104 | * has not changed since the previous scan of all memory areas. | |
105 | * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the | |
106 | * colors of the nodes and not on their contents, assuring that even when | |
107 | * the tree gets "corrupted" it won't get out of balance, so scanning time | |
108 | * remains the same (also, searching and inserting nodes in an rbtree uses | |
109 | * the same algorithm, so we have no overhead when we flush and rebuild). | |
110 | * 4) KSM never flushes the stable tree, which means that even if it were to | |
111 | * take 10 attempts to find a page in the unstable tree, once it is found, | |
112 | * it is secured in the stable tree. (When we scan a new page, we first | |
113 | * compare it against the stable tree, and then against the unstable tree.) | |
8fdb3dbf HD |
114 | * |
115 | * If the merge_across_nodes tunable is unset, then KSM maintains multiple | |
116 | * stable trees and multiple unstable trees: one of each for each NUMA node. | |
31dbd01f IE |
117 | */ |
118 | ||
119 | /** | |
21fbd591 | 120 | * struct ksm_mm_slot - ksm information per mm that is being scanned |
58730ab6 | 121 | * @slot: hash lookup from mm to mm_slot |
6514d511 | 122 | * @rmap_list: head for this mm_slot's singly-linked list of rmap_items |
31dbd01f | 123 | */ |
21fbd591 | 124 | struct ksm_mm_slot { |
58730ab6 | 125 | struct mm_slot slot; |
21fbd591 | 126 | struct ksm_rmap_item *rmap_list; |
31dbd01f IE |
127 | }; |
128 | ||
129 | /** | |
130 | * struct ksm_scan - cursor for scanning | |
131 | * @mm_slot: the current mm_slot we are scanning | |
132 | * @address: the next address inside that to be scanned | |
6514d511 | 133 | * @rmap_list: link to the next rmap to be scanned in the rmap_list |
31dbd01f IE |
134 | * @seqnr: count of completed full scans (needed when removing unstable node) |
135 | * | |
136 | * There is only the one ksm_scan instance of this cursor structure. | |
137 | */ | |
138 | struct ksm_scan { | |
21fbd591 | 139 | struct ksm_mm_slot *mm_slot; |
31dbd01f | 140 | unsigned long address; |
21fbd591 | 141 | struct ksm_rmap_item **rmap_list; |
31dbd01f IE |
142 | unsigned long seqnr; |
143 | }; | |
144 | ||
7b6ba2c7 | 145 | /** |
21fbd591 | 146 | * struct ksm_stable_node - node of the stable rbtree |
7b6ba2c7 | 147 | * @node: rb node of this ksm page in the stable tree |
4146d2d6 | 148 | * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list |
2c653d0e | 149 | * @hlist_dup: linked into the stable_node->hlist with a stable_node chain |
4146d2d6 | 150 | * @list: linked into migrate_nodes, pending placement in the proper node tree |
7b6ba2c7 | 151 | * @hlist: hlist head of rmap_items using this ksm page |
4146d2d6 | 152 | * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid) |
2c653d0e AA |
153 | * @chain_prune_time: time of the last full garbage collection |
154 | * @rmap_hlist_len: number of rmap_item entries in hlist or STABLE_NODE_CHAIN | |
4146d2d6 | 155 | * @nid: NUMA node id of stable tree in which linked (may not match kpfn) |
7b6ba2c7 | 156 | */ |
21fbd591 | 157 | struct ksm_stable_node { |
4146d2d6 HD |
158 | union { |
159 | struct rb_node node; /* when node of stable tree */ | |
160 | struct { /* when listed for migration */ | |
161 | struct list_head *head; | |
2c653d0e AA |
162 | struct { |
163 | struct hlist_node hlist_dup; | |
164 | struct list_head list; | |
165 | }; | |
4146d2d6 HD |
166 | }; |
167 | }; | |
7b6ba2c7 | 168 | struct hlist_head hlist; |
2c653d0e AA |
169 | union { |
170 | unsigned long kpfn; | |
171 | unsigned long chain_prune_time; | |
172 | }; | |
173 | /* | |
174 | * STABLE_NODE_CHAIN can be any negative number in | |
175 | * rmap_hlist_len negative range, but better not -1 to be able | |
176 | * to reliably detect underflows. | |
177 | */ | |
178 | #define STABLE_NODE_CHAIN -1024 | |
179 | int rmap_hlist_len; | |
4146d2d6 HD |
180 | #ifdef CONFIG_NUMA |
181 | int nid; | |
182 | #endif | |
7b6ba2c7 HD |
183 | }; |
184 | ||
31dbd01f | 185 | /** |
21fbd591 | 186 | * struct ksm_rmap_item - reverse mapping item for virtual addresses |
6514d511 | 187 | * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list |
db114b83 | 188 | * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree |
bc56620b | 189 | * @nid: NUMA node id of unstable tree in which linked (may not match page) |
31dbd01f IE |
190 | * @mm: the memory structure this rmap_item is pointing into |
191 | * @address: the virtual address this rmap_item tracks (+ flags in low bits) | |
192 | * @oldchecksum: previous checksum of the page at that virtual address | |
7b6ba2c7 HD |
193 | * @node: rb node of this rmap_item in the unstable tree |
194 | * @head: pointer to stable_node heading this list in the stable tree | |
195 | * @hlist: link into hlist of rmap_items hanging off that stable_node | |
31dbd01f | 196 | */ |
21fbd591 QZ |
197 | struct ksm_rmap_item { |
198 | struct ksm_rmap_item *rmap_list; | |
bc56620b HD |
199 | union { |
200 | struct anon_vma *anon_vma; /* when stable */ | |
201 | #ifdef CONFIG_NUMA | |
202 | int nid; /* when node of unstable tree */ | |
203 | #endif | |
204 | }; | |
31dbd01f IE |
205 | struct mm_struct *mm; |
206 | unsigned long address; /* + low bits used for flags below */ | |
7b6ba2c7 | 207 | unsigned int oldchecksum; /* when unstable */ |
31dbd01f | 208 | union { |
7b6ba2c7 HD |
209 | struct rb_node node; /* when node of unstable tree */ |
210 | struct { /* when listed from stable tree */ | |
21fbd591 | 211 | struct ksm_stable_node *head; |
7b6ba2c7 HD |
212 | struct hlist_node hlist; |
213 | }; | |
31dbd01f IE |
214 | }; |
215 | }; | |
216 | ||
217 | #define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */ | |
7b6ba2c7 HD |
218 | #define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */ |
219 | #define STABLE_FLAG 0x200 /* is listed from the stable tree */ | |
31dbd01f IE |
220 | |
221 | /* The stable and unstable tree heads */ | |
ef53d16c HD |
222 | static struct rb_root one_stable_tree[1] = { RB_ROOT }; |
223 | static struct rb_root one_unstable_tree[1] = { RB_ROOT }; | |
224 | static struct rb_root *root_stable_tree = one_stable_tree; | |
225 | static struct rb_root *root_unstable_tree = one_unstable_tree; | |
31dbd01f | 226 | |
4146d2d6 HD |
227 | /* Recently migrated nodes of stable tree, pending proper placement */ |
228 | static LIST_HEAD(migrate_nodes); | |
2c653d0e | 229 | #define STABLE_NODE_DUP_HEAD ((struct list_head *)&migrate_nodes.prev) |
4146d2d6 | 230 | |
4ca3a69b SL |
231 | #define MM_SLOTS_HASH_BITS 10 |
232 | static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
31dbd01f | 233 | |
21fbd591 | 234 | static struct ksm_mm_slot ksm_mm_head = { |
58730ab6 | 235 | .slot.mm_node = LIST_HEAD_INIT(ksm_mm_head.slot.mm_node), |
31dbd01f IE |
236 | }; |
237 | static struct ksm_scan ksm_scan = { | |
238 | .mm_slot = &ksm_mm_head, | |
239 | }; | |
240 | ||
241 | static struct kmem_cache *rmap_item_cache; | |
7b6ba2c7 | 242 | static struct kmem_cache *stable_node_cache; |
31dbd01f IE |
243 | static struct kmem_cache *mm_slot_cache; |
244 | ||
245 | /* The number of nodes in the stable tree */ | |
b4028260 | 246 | static unsigned long ksm_pages_shared; |
31dbd01f | 247 | |
e178dfde | 248 | /* The number of page slots additionally sharing those nodes */ |
b4028260 | 249 | static unsigned long ksm_pages_sharing; |
31dbd01f | 250 | |
473b0ce4 HD |
251 | /* The number of nodes in the unstable tree */ |
252 | static unsigned long ksm_pages_unshared; | |
253 | ||
254 | /* The number of rmap_items in use: to calculate pages_volatile */ | |
255 | static unsigned long ksm_rmap_items; | |
256 | ||
2c653d0e AA |
257 | /* The number of stable_node chains */ |
258 | static unsigned long ksm_stable_node_chains; | |
259 | ||
260 | /* The number of stable_node dups linked to the stable_node chains */ | |
261 | static unsigned long ksm_stable_node_dups; | |
262 | ||
263 | /* Delay in pruning stale stable_node_dups in the stable_node_chains */ | |
584ff0df | 264 | static unsigned int ksm_stable_node_chains_prune_millisecs = 2000; |
2c653d0e AA |
265 | |
266 | /* Maximum number of page slots sharing a stable node */ | |
267 | static int ksm_max_page_sharing = 256; | |
268 | ||
31dbd01f | 269 | /* Number of pages ksmd should scan in one batch */ |
2c6854fd | 270 | static unsigned int ksm_thread_pages_to_scan = 100; |
31dbd01f IE |
271 | |
272 | /* Milliseconds ksmd should sleep between batches */ | |
2ffd8679 | 273 | static unsigned int ksm_thread_sleep_millisecs = 20; |
31dbd01f | 274 | |
e86c59b1 CI |
275 | /* Checksum of an empty (zeroed) page */ |
276 | static unsigned int zero_checksum __read_mostly; | |
277 | ||
278 | /* Whether to merge empty (zeroed) pages with actual zero pages */ | |
279 | static bool ksm_use_zero_pages __read_mostly; | |
280 | ||
e850dcf5 | 281 | #ifdef CONFIG_NUMA |
90bd6fd3 PH |
282 | /* Zeroed when merging across nodes is not allowed */ |
283 | static unsigned int ksm_merge_across_nodes = 1; | |
ef53d16c | 284 | static int ksm_nr_node_ids = 1; |
e850dcf5 HD |
285 | #else |
286 | #define ksm_merge_across_nodes 1U | |
ef53d16c | 287 | #define ksm_nr_node_ids 1 |
e850dcf5 | 288 | #endif |
90bd6fd3 | 289 | |
31dbd01f IE |
290 | #define KSM_RUN_STOP 0 |
291 | #define KSM_RUN_MERGE 1 | |
292 | #define KSM_RUN_UNMERGE 2 | |
ef4d43a8 HD |
293 | #define KSM_RUN_OFFLINE 4 |
294 | static unsigned long ksm_run = KSM_RUN_STOP; | |
295 | static void wait_while_offlining(void); | |
31dbd01f IE |
296 | |
297 | static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait); | |
fcf9a0ef | 298 | static DECLARE_WAIT_QUEUE_HEAD(ksm_iter_wait); |
31dbd01f IE |
299 | static DEFINE_MUTEX(ksm_thread_mutex); |
300 | static DEFINE_SPINLOCK(ksm_mmlist_lock); | |
301 | ||
21fbd591 | 302 | #define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\ |
31dbd01f IE |
303 | sizeof(struct __struct), __alignof__(struct __struct),\ |
304 | (__flags), NULL) | |
305 | ||
306 | static int __init ksm_slab_init(void) | |
307 | { | |
21fbd591 | 308 | rmap_item_cache = KSM_KMEM_CACHE(ksm_rmap_item, 0); |
31dbd01f IE |
309 | if (!rmap_item_cache) |
310 | goto out; | |
311 | ||
21fbd591 | 312 | stable_node_cache = KSM_KMEM_CACHE(ksm_stable_node, 0); |
7b6ba2c7 HD |
313 | if (!stable_node_cache) |
314 | goto out_free1; | |
315 | ||
21fbd591 | 316 | mm_slot_cache = KSM_KMEM_CACHE(ksm_mm_slot, 0); |
31dbd01f | 317 | if (!mm_slot_cache) |
7b6ba2c7 | 318 | goto out_free2; |
31dbd01f IE |
319 | |
320 | return 0; | |
321 | ||
7b6ba2c7 HD |
322 | out_free2: |
323 | kmem_cache_destroy(stable_node_cache); | |
324 | out_free1: | |
31dbd01f IE |
325 | kmem_cache_destroy(rmap_item_cache); |
326 | out: | |
327 | return -ENOMEM; | |
328 | } | |
329 | ||
330 | static void __init ksm_slab_free(void) | |
331 | { | |
332 | kmem_cache_destroy(mm_slot_cache); | |
7b6ba2c7 | 333 | kmem_cache_destroy(stable_node_cache); |
31dbd01f IE |
334 | kmem_cache_destroy(rmap_item_cache); |
335 | mm_slot_cache = NULL; | |
336 | } | |
337 | ||
21fbd591 | 338 | static __always_inline bool is_stable_node_chain(struct ksm_stable_node *chain) |
2c653d0e AA |
339 | { |
340 | return chain->rmap_hlist_len == STABLE_NODE_CHAIN; | |
341 | } | |
342 | ||
21fbd591 | 343 | static __always_inline bool is_stable_node_dup(struct ksm_stable_node *dup) |
2c653d0e AA |
344 | { |
345 | return dup->head == STABLE_NODE_DUP_HEAD; | |
346 | } | |
347 | ||
21fbd591 QZ |
348 | static inline void stable_node_chain_add_dup(struct ksm_stable_node *dup, |
349 | struct ksm_stable_node *chain) | |
2c653d0e AA |
350 | { |
351 | VM_BUG_ON(is_stable_node_dup(dup)); | |
352 | dup->head = STABLE_NODE_DUP_HEAD; | |
353 | VM_BUG_ON(!is_stable_node_chain(chain)); | |
354 | hlist_add_head(&dup->hlist_dup, &chain->hlist); | |
355 | ksm_stable_node_dups++; | |
356 | } | |
357 | ||
21fbd591 | 358 | static inline void __stable_node_dup_del(struct ksm_stable_node *dup) |
2c653d0e | 359 | { |
b4fecc67 | 360 | VM_BUG_ON(!is_stable_node_dup(dup)); |
2c653d0e AA |
361 | hlist_del(&dup->hlist_dup); |
362 | ksm_stable_node_dups--; | |
363 | } | |
364 | ||
21fbd591 | 365 | static inline void stable_node_dup_del(struct ksm_stable_node *dup) |
2c653d0e AA |
366 | { |
367 | VM_BUG_ON(is_stable_node_chain(dup)); | |
368 | if (is_stable_node_dup(dup)) | |
369 | __stable_node_dup_del(dup); | |
370 | else | |
371 | rb_erase(&dup->node, root_stable_tree + NUMA(dup->nid)); | |
372 | #ifdef CONFIG_DEBUG_VM | |
373 | dup->head = NULL; | |
374 | #endif | |
375 | } | |
376 | ||
21fbd591 | 377 | static inline struct ksm_rmap_item *alloc_rmap_item(void) |
31dbd01f | 378 | { |
21fbd591 | 379 | struct ksm_rmap_item *rmap_item; |
473b0ce4 | 380 | |
5b398e41 | 381 | rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL | |
382 | __GFP_NORETRY | __GFP_NOWARN); | |
473b0ce4 HD |
383 | if (rmap_item) |
384 | ksm_rmap_items++; | |
385 | return rmap_item; | |
31dbd01f IE |
386 | } |
387 | ||
21fbd591 | 388 | static inline void free_rmap_item(struct ksm_rmap_item *rmap_item) |
31dbd01f | 389 | { |
473b0ce4 | 390 | ksm_rmap_items--; |
cb4df4ca | 391 | rmap_item->mm->ksm_rmap_items--; |
31dbd01f IE |
392 | rmap_item->mm = NULL; /* debug safety */ |
393 | kmem_cache_free(rmap_item_cache, rmap_item); | |
394 | } | |
395 | ||
21fbd591 | 396 | static inline struct ksm_stable_node *alloc_stable_node(void) |
7b6ba2c7 | 397 | { |
6213055f | 398 | /* |
399 | * The allocation can take too long with GFP_KERNEL when memory is under | |
400 | * pressure, which may lead to hung task warnings. Adding __GFP_HIGH | |
401 | * grants access to memory reserves, helping to avoid this problem. | |
402 | */ | |
403 | return kmem_cache_alloc(stable_node_cache, GFP_KERNEL | __GFP_HIGH); | |
7b6ba2c7 HD |
404 | } |
405 | ||
21fbd591 | 406 | static inline void free_stable_node(struct ksm_stable_node *stable_node) |
7b6ba2c7 | 407 | { |
2c653d0e AA |
408 | VM_BUG_ON(stable_node->rmap_hlist_len && |
409 | !is_stable_node_chain(stable_node)); | |
7b6ba2c7 HD |
410 | kmem_cache_free(stable_node_cache, stable_node); |
411 | } | |
412 | ||
a913e182 HD |
413 | /* |
414 | * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's | |
415 | * page tables after it has passed through ksm_exit() - which, if necessary, | |
c1e8d7c6 | 416 | * takes mmap_lock briefly to serialize against them. ksm_exit() does not set |
a913e182 HD |
417 | * a special flag: they can just back out as soon as mm_users goes to zero. |
418 | * ksm_test_exit() is used throughout to make this test for exit: in some | |
419 | * places for correctness, in some places just to avoid unnecessary work. | |
420 | */ | |
421 | static inline bool ksm_test_exit(struct mm_struct *mm) | |
422 | { | |
423 | return atomic_read(&mm->mm_users) == 0; | |
424 | } | |
425 | ||
d7c0e68d DH |
426 | static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long next, |
427 | struct mm_walk *walk) | |
428 | { | |
429 | struct page *page = NULL; | |
430 | spinlock_t *ptl; | |
431 | pte_t *pte; | |
432 | int ret; | |
433 | ||
434 | if (pmd_leaf(*pmd) || !pmd_present(*pmd)) | |
435 | return 0; | |
436 | ||
437 | pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); | |
438 | if (pte_present(*pte)) { | |
439 | page = vm_normal_page(walk->vma, addr, *pte); | |
440 | } else if (!pte_none(*pte)) { | |
441 | swp_entry_t entry = pte_to_swp_entry(*pte); | |
442 | ||
443 | /* | |
444 | * As KSM pages remain KSM pages until freed, no need to wait | |
445 | * here for migration to end. | |
446 | */ | |
447 | if (is_migration_entry(entry)) | |
448 | page = pfn_swap_entry_to_page(entry); | |
449 | } | |
450 | ret = page && PageKsm(page); | |
451 | pte_unmap_unlock(pte, ptl); | |
452 | return ret; | |
453 | } | |
454 | ||
455 | static const struct mm_walk_ops break_ksm_ops = { | |
456 | .pmd_entry = break_ksm_pmd_entry, | |
457 | }; | |
458 | ||
31dbd01f | 459 | /* |
6cce3314 DH |
460 | * We use break_ksm to break COW on a ksm page by triggering unsharing, |
461 | * such that the ksm page will get replaced by an exclusive anonymous page. | |
31dbd01f | 462 | * |
6cce3314 | 463 | * We take great care only to touch a ksm page, in a VM_MERGEABLE vma, |
31dbd01f IE |
464 | * in case the application has unmapped and remapped mm,addr meanwhile. |
465 | * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP | |
bbcd53c9 | 466 | * mmap of /dev/mem, where we would not want to touch it. |
1b2ee126 | 467 | * |
6cce3314 | 468 | * FAULT_FLAG_REMOTE/FOLL_REMOTE are because we do this outside the context |
1b2ee126 DH |
469 | * of the process that owns 'vma'. We also do not want to enforce |
470 | * protection keys here anyway. | |
31dbd01f | 471 | */ |
d952b791 | 472 | static int break_ksm(struct vm_area_struct *vma, unsigned long addr) |
31dbd01f | 473 | { |
50a7ca3c | 474 | vm_fault_t ret = 0; |
31dbd01f IE |
475 | |
476 | do { | |
d7c0e68d | 477 | int ksm_page; |
58f595c6 | 478 | |
31dbd01f | 479 | cond_resched(); |
d7c0e68d DH |
480 | ksm_page = walk_page_range_vma(vma, addr, addr + 1, |
481 | &break_ksm_ops, NULL); | |
482 | if (WARN_ON_ONCE(ksm_page < 0)) | |
483 | return ksm_page; | |
58f595c6 DH |
484 | if (!ksm_page) |
485 | return 0; | |
486 | ret = handle_mm_fault(vma, addr, | |
6cce3314 | 487 | FAULT_FLAG_UNSHARE | FAULT_FLAG_REMOTE, |
58f595c6 DH |
488 | NULL); |
489 | } while (!(ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM))); | |
d952b791 | 490 | /* |
58f595c6 DH |
491 | * We must loop until we no longer find a KSM page because |
492 | * handle_mm_fault() may back out if there's any difficulty e.g. if | |
493 | * pte accessed bit gets updated concurrently. | |
d952b791 HD |
494 | * |
495 | * VM_FAULT_SIGBUS could occur if we race with truncation of the | |
496 | * backing file, which also invalidates anonymous pages: that's | |
497 | * okay, that truncation will have unmapped the PageKsm for us. | |
498 | * | |
499 | * VM_FAULT_OOM: at the time of writing (late July 2009), setting | |
500 | * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the | |
501 | * current task has TIF_MEMDIE set, and will be OOM killed on return | |
502 | * to user; and ksmd, having no mm, would never be chosen for that. | |
503 | * | |
504 | * But if the mm is in a limited mem_cgroup, then the fault may fail | |
505 | * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and | |
506 | * even ksmd can fail in this way - though it's usually breaking ksm | |
507 | * just to undo a merge it made a moment before, so unlikely to oom. | |
508 | * | |
509 | * That's a pity: we might therefore have more kernel pages allocated | |
510 | * than we're counting as nodes in the stable tree; but ksm_do_scan | |
511 | * will retry to break_cow on each pass, so should recover the page | |
512 | * in due course. The important thing is to not let VM_MERGEABLE | |
513 | * be cleared while any such pages might remain in the area. | |
514 | */ | |
515 | return (ret & VM_FAULT_OOM) ? -ENOMEM : 0; | |
31dbd01f IE |
516 | } |
517 | ||
d7597f59 SR |
518 | static bool vma_ksm_compatible(struct vm_area_struct *vma) |
519 | { | |
520 | if (vma->vm_flags & (VM_SHARED | VM_MAYSHARE | VM_PFNMAP | | |
521 | VM_IO | VM_DONTEXPAND | VM_HUGETLB | | |
522 | VM_MIXEDMAP)) | |
523 | return false; /* just ignore the advice */ | |
524 | ||
525 | if (vma_is_dax(vma)) | |
526 | return false; | |
527 | ||
528 | #ifdef VM_SAO | |
529 | if (vma->vm_flags & VM_SAO) | |
530 | return false; | |
531 | #endif | |
532 | #ifdef VM_SPARC_ADI | |
533 | if (vma->vm_flags & VM_SPARC_ADI) | |
534 | return false; | |
535 | #endif | |
536 | ||
537 | return true; | |
538 | } | |
539 | ||
ef694222 BL |
540 | static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm, |
541 | unsigned long addr) | |
542 | { | |
543 | struct vm_area_struct *vma; | |
544 | if (ksm_test_exit(mm)) | |
545 | return NULL; | |
ff69fb81 LH |
546 | vma = vma_lookup(mm, addr); |
547 | if (!vma || !(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) | |
ef694222 BL |
548 | return NULL; |
549 | return vma; | |
550 | } | |
551 | ||
21fbd591 | 552 | static void break_cow(struct ksm_rmap_item *rmap_item) |
31dbd01f | 553 | { |
8dd3557a HD |
554 | struct mm_struct *mm = rmap_item->mm; |
555 | unsigned long addr = rmap_item->address; | |
31dbd01f IE |
556 | struct vm_area_struct *vma; |
557 | ||
4035c07a HD |
558 | /* |
559 | * It is not an accident that whenever we want to break COW | |
560 | * to undo, we also need to drop a reference to the anon_vma. | |
561 | */ | |
9e60109f | 562 | put_anon_vma(rmap_item->anon_vma); |
4035c07a | 563 | |
d8ed45c5 | 564 | mmap_read_lock(mm); |
ef694222 BL |
565 | vma = find_mergeable_vma(mm, addr); |
566 | if (vma) | |
567 | break_ksm(vma, addr); | |
d8ed45c5 | 568 | mmap_read_unlock(mm); |
31dbd01f IE |
569 | } |
570 | ||
21fbd591 | 571 | static struct page *get_mergeable_page(struct ksm_rmap_item *rmap_item) |
31dbd01f IE |
572 | { |
573 | struct mm_struct *mm = rmap_item->mm; | |
574 | unsigned long addr = rmap_item->address; | |
575 | struct vm_area_struct *vma; | |
576 | struct page *page; | |
577 | ||
d8ed45c5 | 578 | mmap_read_lock(mm); |
ef694222 BL |
579 | vma = find_mergeable_vma(mm, addr); |
580 | if (!vma) | |
31dbd01f IE |
581 | goto out; |
582 | ||
583 | page = follow_page(vma, addr, FOLL_GET); | |
f7091ed6 | 584 | if (IS_ERR_OR_NULL(page)) |
31dbd01f | 585 | goto out; |
f7091ed6 HW |
586 | if (is_zone_device_page(page)) |
587 | goto out_putpage; | |
f765f540 | 588 | if (PageAnon(page)) { |
31dbd01f IE |
589 | flush_anon_page(vma, page, addr); |
590 | flush_dcache_page(page); | |
591 | } else { | |
f7091ed6 | 592 | out_putpage: |
31dbd01f | 593 | put_page(page); |
c8f95ed1 AA |
594 | out: |
595 | page = NULL; | |
31dbd01f | 596 | } |
d8ed45c5 | 597 | mmap_read_unlock(mm); |
31dbd01f IE |
598 | return page; |
599 | } | |
600 | ||
90bd6fd3 PH |
601 | /* |
602 | * This helper is used for getting right index into array of tree roots. | |
603 | * When merge_across_nodes knob is set to 1, there are only two rb-trees for | |
604 | * stable and unstable pages from all nodes with roots in index 0. Otherwise, | |
605 | * every node has its own stable and unstable tree. | |
606 | */ | |
607 | static inline int get_kpfn_nid(unsigned long kpfn) | |
608 | { | |
d8fc16a8 | 609 | return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn)); |
90bd6fd3 PH |
610 | } |
611 | ||
21fbd591 | 612 | static struct ksm_stable_node *alloc_stable_node_chain(struct ksm_stable_node *dup, |
2c653d0e AA |
613 | struct rb_root *root) |
614 | { | |
21fbd591 | 615 | struct ksm_stable_node *chain = alloc_stable_node(); |
2c653d0e AA |
616 | VM_BUG_ON(is_stable_node_chain(dup)); |
617 | if (likely(chain)) { | |
618 | INIT_HLIST_HEAD(&chain->hlist); | |
619 | chain->chain_prune_time = jiffies; | |
620 | chain->rmap_hlist_len = STABLE_NODE_CHAIN; | |
621 | #if defined (CONFIG_DEBUG_VM) && defined(CONFIG_NUMA) | |
98fa15f3 | 622 | chain->nid = NUMA_NO_NODE; /* debug */ |
2c653d0e AA |
623 | #endif |
624 | ksm_stable_node_chains++; | |
625 | ||
626 | /* | |
627 | * Put the stable node chain in the first dimension of | |
628 | * the stable tree and at the same time remove the old | |
629 | * stable node. | |
630 | */ | |
631 | rb_replace_node(&dup->node, &chain->node, root); | |
632 | ||
633 | /* | |
634 | * Move the old stable node to the second dimension | |
635 | * queued in the hlist_dup. The invariant is that all | |
636 | * dup stable_nodes in the chain->hlist point to pages | |
457aef94 | 637 | * that are write protected and have the exact same |
2c653d0e AA |
638 | * content. |
639 | */ | |
640 | stable_node_chain_add_dup(dup, chain); | |
641 | } | |
642 | return chain; | |
643 | } | |
644 | ||
21fbd591 | 645 | static inline void free_stable_node_chain(struct ksm_stable_node *chain, |
2c653d0e AA |
646 | struct rb_root *root) |
647 | { | |
648 | rb_erase(&chain->node, root); | |
649 | free_stable_node(chain); | |
650 | ksm_stable_node_chains--; | |
651 | } | |
652 | ||
21fbd591 | 653 | static void remove_node_from_stable_tree(struct ksm_stable_node *stable_node) |
4035c07a | 654 | { |
21fbd591 | 655 | struct ksm_rmap_item *rmap_item; |
4035c07a | 656 | |
2c653d0e AA |
657 | /* check it's not STABLE_NODE_CHAIN or negative */ |
658 | BUG_ON(stable_node->rmap_hlist_len < 0); | |
659 | ||
b67bfe0d | 660 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
739100c8 | 661 | if (rmap_item->hlist.next) { |
4035c07a | 662 | ksm_pages_sharing--; |
739100c8 SR |
663 | trace_ksm_remove_rmap_item(stable_node->kpfn, rmap_item, rmap_item->mm); |
664 | } else { | |
4035c07a | 665 | ksm_pages_shared--; |
739100c8 | 666 | } |
76093853 | 667 | |
668 | rmap_item->mm->ksm_merging_pages--; | |
669 | ||
2c653d0e AA |
670 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
671 | stable_node->rmap_hlist_len--; | |
9e60109f | 672 | put_anon_vma(rmap_item->anon_vma); |
4035c07a HD |
673 | rmap_item->address &= PAGE_MASK; |
674 | cond_resched(); | |
675 | } | |
676 | ||
2c653d0e AA |
677 | /* |
678 | * We need the second aligned pointer of the migrate_nodes | |
679 | * list_head to stay clear from the rb_parent_color union | |
680 | * (aligned and different than any node) and also different | |
681 | * from &migrate_nodes. This will verify that future list.h changes | |
815f0ddb | 682 | * don't break STABLE_NODE_DUP_HEAD. Only recent gcc can handle it. |
2c653d0e | 683 | */ |
2c653d0e AA |
684 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD <= &migrate_nodes); |
685 | BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1); | |
2c653d0e | 686 | |
739100c8 | 687 | trace_ksm_remove_ksm_page(stable_node->kpfn); |
4146d2d6 HD |
688 | if (stable_node->head == &migrate_nodes) |
689 | list_del(&stable_node->list); | |
690 | else | |
2c653d0e | 691 | stable_node_dup_del(stable_node); |
4035c07a HD |
692 | free_stable_node(stable_node); |
693 | } | |
694 | ||
2cee57d1 YS |
695 | enum get_ksm_page_flags { |
696 | GET_KSM_PAGE_NOLOCK, | |
697 | GET_KSM_PAGE_LOCK, | |
698 | GET_KSM_PAGE_TRYLOCK | |
699 | }; | |
700 | ||
4035c07a HD |
701 | /* |
702 | * get_ksm_page: checks if the page indicated by the stable node | |
703 | * is still its ksm page, despite having held no reference to it. | |
704 | * In which case we can trust the content of the page, and it | |
705 | * returns the gotten page; but if the page has now been zapped, | |
706 | * remove the stale node from the stable tree and return NULL. | |
c8d6553b | 707 | * But beware, the stable node's page might be being migrated. |
4035c07a HD |
708 | * |
709 | * You would expect the stable_node to hold a reference to the ksm page. | |
710 | * But if it increments the page's count, swapping out has to wait for | |
711 | * ksmd to come around again before it can free the page, which may take | |
712 | * seconds or even minutes: much too unresponsive. So instead we use a | |
713 | * "keyhole reference": access to the ksm page from the stable node peeps | |
714 | * out through its keyhole to see if that page still holds the right key, | |
715 | * pointing back to this stable node. This relies on freeing a PageAnon | |
716 | * page to reset its page->mapping to NULL, and relies on no other use of | |
717 | * a page to put something that might look like our key in page->mapping. | |
4035c07a HD |
718 | * is on its way to being freed; but it is an anomaly to bear in mind. |
719 | */ | |
21fbd591 | 720 | static struct page *get_ksm_page(struct ksm_stable_node *stable_node, |
2cee57d1 | 721 | enum get_ksm_page_flags flags) |
4035c07a HD |
722 | { |
723 | struct page *page; | |
724 | void *expected_mapping; | |
c8d6553b | 725 | unsigned long kpfn; |
4035c07a | 726 | |
bda807d4 MK |
727 | expected_mapping = (void *)((unsigned long)stable_node | |
728 | PAGE_MAPPING_KSM); | |
c8d6553b | 729 | again: |
08df4774 | 730 | kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */ |
c8d6553b | 731 | page = pfn_to_page(kpfn); |
4db0c3c2 | 732 | if (READ_ONCE(page->mapping) != expected_mapping) |
4035c07a | 733 | goto stale; |
c8d6553b HD |
734 | |
735 | /* | |
736 | * We cannot do anything with the page while its refcount is 0. | |
737 | * Usually 0 means free, or tail of a higher-order page: in which | |
738 | * case this node is no longer referenced, and should be freed; | |
1c4c3b99 | 739 | * however, it might mean that the page is under page_ref_freeze(). |
c8d6553b | 740 | * The __remove_mapping() case is easy, again the node is now stale; |
52d1e606 | 741 | * the same is in reuse_ksm_page() case; but if page is swapcache |
9800562f | 742 | * in folio_migrate_mapping(), it might still be our page, |
52d1e606 | 743 | * in which case it's essential to keep the node. |
c8d6553b HD |
744 | */ |
745 | while (!get_page_unless_zero(page)) { | |
746 | /* | |
747 | * Another check for page->mapping != expected_mapping would | |
748 | * work here too. We have chosen the !PageSwapCache test to | |
749 | * optimize the common case, when the page is or is about to | |
750 | * be freed: PageSwapCache is cleared (under spin_lock_irq) | |
1c4c3b99 | 751 | * in the ref_freeze section of __remove_mapping(); but Anon |
c8d6553b HD |
752 | * page->mapping reset to NULL later, in free_pages_prepare(). |
753 | */ | |
754 | if (!PageSwapCache(page)) | |
755 | goto stale; | |
756 | cpu_relax(); | |
757 | } | |
758 | ||
4db0c3c2 | 759 | if (READ_ONCE(page->mapping) != expected_mapping) { |
4035c07a HD |
760 | put_page(page); |
761 | goto stale; | |
762 | } | |
c8d6553b | 763 | |
2cee57d1 YS |
764 | if (flags == GET_KSM_PAGE_TRYLOCK) { |
765 | if (!trylock_page(page)) { | |
766 | put_page(page); | |
767 | return ERR_PTR(-EBUSY); | |
768 | } | |
769 | } else if (flags == GET_KSM_PAGE_LOCK) | |
8aafa6a4 | 770 | lock_page(page); |
2cee57d1 YS |
771 | |
772 | if (flags != GET_KSM_PAGE_NOLOCK) { | |
4db0c3c2 | 773 | if (READ_ONCE(page->mapping) != expected_mapping) { |
8aafa6a4 HD |
774 | unlock_page(page); |
775 | put_page(page); | |
776 | goto stale; | |
777 | } | |
778 | } | |
4035c07a | 779 | return page; |
c8d6553b | 780 | |
4035c07a | 781 | stale: |
c8d6553b HD |
782 | /* |
783 | * We come here from above when page->mapping or !PageSwapCache | |
784 | * suggests that the node is stale; but it might be under migration. | |
19138349 | 785 | * We need smp_rmb(), matching the smp_wmb() in folio_migrate_ksm(), |
c8d6553b HD |
786 | * before checking whether node->kpfn has been changed. |
787 | */ | |
788 | smp_rmb(); | |
4db0c3c2 | 789 | if (READ_ONCE(stable_node->kpfn) != kpfn) |
c8d6553b | 790 | goto again; |
4035c07a HD |
791 | remove_node_from_stable_tree(stable_node); |
792 | return NULL; | |
793 | } | |
794 | ||
31dbd01f IE |
795 | /* |
796 | * Removing rmap_item from stable or unstable tree. | |
797 | * This function will clean the information from the stable/unstable tree. | |
798 | */ | |
21fbd591 | 799 | static void remove_rmap_item_from_tree(struct ksm_rmap_item *rmap_item) |
31dbd01f | 800 | { |
7b6ba2c7 | 801 | if (rmap_item->address & STABLE_FLAG) { |
21fbd591 | 802 | struct ksm_stable_node *stable_node; |
5ad64688 | 803 | struct page *page; |
31dbd01f | 804 | |
7b6ba2c7 | 805 | stable_node = rmap_item->head; |
62862290 | 806 | page = get_ksm_page(stable_node, GET_KSM_PAGE_LOCK); |
4035c07a HD |
807 | if (!page) |
808 | goto out; | |
5ad64688 | 809 | |
7b6ba2c7 | 810 | hlist_del(&rmap_item->hlist); |
62862290 | 811 | unlock_page(page); |
4035c07a | 812 | put_page(page); |
08beca44 | 813 | |
98666f8a | 814 | if (!hlist_empty(&stable_node->hlist)) |
4035c07a HD |
815 | ksm_pages_sharing--; |
816 | else | |
7b6ba2c7 | 817 | ksm_pages_shared--; |
76093853 | 818 | |
819 | rmap_item->mm->ksm_merging_pages--; | |
820 | ||
2c653d0e AA |
821 | VM_BUG_ON(stable_node->rmap_hlist_len <= 0); |
822 | stable_node->rmap_hlist_len--; | |
31dbd01f | 823 | |
9e60109f | 824 | put_anon_vma(rmap_item->anon_vma); |
c89a384e | 825 | rmap_item->head = NULL; |
93d17715 | 826 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 827 | |
7b6ba2c7 | 828 | } else if (rmap_item->address & UNSTABLE_FLAG) { |
31dbd01f IE |
829 | unsigned char age; |
830 | /* | |
9ba69294 | 831 | * Usually ksmd can and must skip the rb_erase, because |
31dbd01f | 832 | * root_unstable_tree was already reset to RB_ROOT. |
9ba69294 HD |
833 | * But be careful when an mm is exiting: do the rb_erase |
834 | * if this rmap_item was inserted by this scan, rather | |
835 | * than left over from before. | |
31dbd01f IE |
836 | */ |
837 | age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); | |
cd551f97 | 838 | BUG_ON(age > 1); |
31dbd01f | 839 | if (!age) |
90bd6fd3 | 840 | rb_erase(&rmap_item->node, |
ef53d16c | 841 | root_unstable_tree + NUMA(rmap_item->nid)); |
473b0ce4 | 842 | ksm_pages_unshared--; |
93d17715 | 843 | rmap_item->address &= PAGE_MASK; |
31dbd01f | 844 | } |
4035c07a | 845 | out: |
31dbd01f IE |
846 | cond_resched(); /* we're called from many long loops */ |
847 | } | |
848 | ||
21fbd591 | 849 | static void remove_trailing_rmap_items(struct ksm_rmap_item **rmap_list) |
31dbd01f | 850 | { |
6514d511 | 851 | while (*rmap_list) { |
21fbd591 | 852 | struct ksm_rmap_item *rmap_item = *rmap_list; |
6514d511 | 853 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 854 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
855 | free_rmap_item(rmap_item); |
856 | } | |
857 | } | |
858 | ||
859 | /* | |
e850dcf5 | 860 | * Though it's very tempting to unmerge rmap_items from stable tree rather |
31dbd01f IE |
861 | * than check every pte of a given vma, the locking doesn't quite work for |
862 | * that - an rmap_item is assigned to the stable tree after inserting ksm | |
c1e8d7c6 | 863 | * page and upping mmap_lock. Nor does it fit with the way we skip dup'ing |
31dbd01f IE |
864 | * rmap_items from parent to child at fork time (so as not to waste time |
865 | * if exit comes before the next scan reaches it). | |
81464e30 HD |
866 | * |
867 | * Similarly, although we'd like to remove rmap_items (so updating counts | |
868 | * and freeing memory) when unmerging an area, it's easier to leave that | |
869 | * to the next pass of ksmd - consider, for example, how ksmd might be | |
870 | * in cmp_and_merge_page on one of the rmap_items we would be removing. | |
31dbd01f | 871 | */ |
d952b791 HD |
872 | static int unmerge_ksm_pages(struct vm_area_struct *vma, |
873 | unsigned long start, unsigned long end) | |
31dbd01f IE |
874 | { |
875 | unsigned long addr; | |
d952b791 | 876 | int err = 0; |
31dbd01f | 877 | |
d952b791 | 878 | for (addr = start; addr < end && !err; addr += PAGE_SIZE) { |
9ba69294 HD |
879 | if (ksm_test_exit(vma->vm_mm)) |
880 | break; | |
d952b791 HD |
881 | if (signal_pending(current)) |
882 | err = -ERESTARTSYS; | |
883 | else | |
884 | err = break_ksm(vma, addr); | |
885 | } | |
886 | return err; | |
31dbd01f IE |
887 | } |
888 | ||
21fbd591 | 889 | static inline struct ksm_stable_node *folio_stable_node(struct folio *folio) |
19138349 MWO |
890 | { |
891 | return folio_test_ksm(folio) ? folio_raw_mapping(folio) : NULL; | |
892 | } | |
893 | ||
21fbd591 | 894 | static inline struct ksm_stable_node *page_stable_node(struct page *page) |
88484826 | 895 | { |
19138349 | 896 | return folio_stable_node(page_folio(page)); |
88484826 MR |
897 | } |
898 | ||
899 | static inline void set_page_stable_node(struct page *page, | |
21fbd591 | 900 | struct ksm_stable_node *stable_node) |
88484826 | 901 | { |
6c287605 | 902 | VM_BUG_ON_PAGE(PageAnon(page) && PageAnonExclusive(page), page); |
88484826 MR |
903 | page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM); |
904 | } | |
905 | ||
2ffd8679 HD |
906 | #ifdef CONFIG_SYSFS |
907 | /* | |
908 | * Only called through the sysfs control interface: | |
909 | */ | |
21fbd591 | 910 | static int remove_stable_node(struct ksm_stable_node *stable_node) |
cbf86cfe HD |
911 | { |
912 | struct page *page; | |
913 | int err; | |
914 | ||
2cee57d1 | 915 | page = get_ksm_page(stable_node, GET_KSM_PAGE_LOCK); |
cbf86cfe HD |
916 | if (!page) { |
917 | /* | |
918 | * get_ksm_page did remove_node_from_stable_tree itself. | |
919 | */ | |
920 | return 0; | |
921 | } | |
922 | ||
9a63236f AR |
923 | /* |
924 | * Page could be still mapped if this races with __mmput() running in | |
925 | * between ksm_exit() and exit_mmap(). Just refuse to let | |
926 | * merge_across_nodes/max_page_sharing be switched. | |
927 | */ | |
928 | err = -EBUSY; | |
929 | if (!page_mapped(page)) { | |
cbf86cfe | 930 | /* |
8fdb3dbf HD |
931 | * The stable node did not yet appear stale to get_ksm_page(), |
932 | * since that allows for an unmapped ksm page to be recognized | |
933 | * right up until it is freed; but the node is safe to remove. | |
cbf86cfe HD |
934 | * This page might be in a pagevec waiting to be freed, |
935 | * or it might be PageSwapCache (perhaps under writeback), | |
936 | * or it might have been removed from swapcache a moment ago. | |
937 | */ | |
938 | set_page_stable_node(page, NULL); | |
939 | remove_node_from_stable_tree(stable_node); | |
940 | err = 0; | |
941 | } | |
942 | ||
943 | unlock_page(page); | |
944 | put_page(page); | |
945 | return err; | |
946 | } | |
947 | ||
21fbd591 | 948 | static int remove_stable_node_chain(struct ksm_stable_node *stable_node, |
2c653d0e AA |
949 | struct rb_root *root) |
950 | { | |
21fbd591 | 951 | struct ksm_stable_node *dup; |
2c653d0e AA |
952 | struct hlist_node *hlist_safe; |
953 | ||
954 | if (!is_stable_node_chain(stable_node)) { | |
955 | VM_BUG_ON(is_stable_node_dup(stable_node)); | |
956 | if (remove_stable_node(stable_node)) | |
957 | return true; | |
958 | else | |
959 | return false; | |
960 | } | |
961 | ||
962 | hlist_for_each_entry_safe(dup, hlist_safe, | |
963 | &stable_node->hlist, hlist_dup) { | |
964 | VM_BUG_ON(!is_stable_node_dup(dup)); | |
965 | if (remove_stable_node(dup)) | |
966 | return true; | |
967 | } | |
968 | BUG_ON(!hlist_empty(&stable_node->hlist)); | |
969 | free_stable_node_chain(stable_node, root); | |
970 | return false; | |
971 | } | |
972 | ||
cbf86cfe HD |
973 | static int remove_all_stable_nodes(void) |
974 | { | |
21fbd591 | 975 | struct ksm_stable_node *stable_node, *next; |
cbf86cfe HD |
976 | int nid; |
977 | int err = 0; | |
978 | ||
ef53d16c | 979 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
cbf86cfe HD |
980 | while (root_stable_tree[nid].rb_node) { |
981 | stable_node = rb_entry(root_stable_tree[nid].rb_node, | |
21fbd591 | 982 | struct ksm_stable_node, node); |
2c653d0e AA |
983 | if (remove_stable_node_chain(stable_node, |
984 | root_stable_tree + nid)) { | |
cbf86cfe HD |
985 | err = -EBUSY; |
986 | break; /* proceed to next nid */ | |
987 | } | |
988 | cond_resched(); | |
989 | } | |
990 | } | |
03640418 | 991 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
992 | if (remove_stable_node(stable_node)) |
993 | err = -EBUSY; | |
994 | cond_resched(); | |
995 | } | |
cbf86cfe HD |
996 | return err; |
997 | } | |
998 | ||
d952b791 | 999 | static int unmerge_and_remove_all_rmap_items(void) |
31dbd01f | 1000 | { |
21fbd591 | 1001 | struct ksm_mm_slot *mm_slot; |
58730ab6 | 1002 | struct mm_slot *slot; |
31dbd01f IE |
1003 | struct mm_struct *mm; |
1004 | struct vm_area_struct *vma; | |
d952b791 HD |
1005 | int err = 0; |
1006 | ||
1007 | spin_lock(&ksm_mmlist_lock); | |
58730ab6 QZ |
1008 | slot = list_entry(ksm_mm_head.slot.mm_node.next, |
1009 | struct mm_slot, mm_node); | |
1010 | ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); | |
d952b791 | 1011 | spin_unlock(&ksm_mmlist_lock); |
31dbd01f | 1012 | |
a5f18ba0 MWO |
1013 | for (mm_slot = ksm_scan.mm_slot; mm_slot != &ksm_mm_head; |
1014 | mm_slot = ksm_scan.mm_slot) { | |
58730ab6 | 1015 | VMA_ITERATOR(vmi, mm_slot->slot.mm, 0); |
a5f18ba0 | 1016 | |
58730ab6 | 1017 | mm = mm_slot->slot.mm; |
d8ed45c5 | 1018 | mmap_read_lock(mm); |
6db504ce LH |
1019 | |
1020 | /* | |
1021 | * Exit right away if mm is exiting to avoid lockdep issue in | |
1022 | * the maple tree | |
1023 | */ | |
1024 | if (ksm_test_exit(mm)) | |
1025 | goto mm_exiting; | |
1026 | ||
a5f18ba0 | 1027 | for_each_vma(vmi, vma) { |
31dbd01f IE |
1028 | if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma) |
1029 | continue; | |
d952b791 HD |
1030 | err = unmerge_ksm_pages(vma, |
1031 | vma->vm_start, vma->vm_end); | |
9ba69294 HD |
1032 | if (err) |
1033 | goto error; | |
31dbd01f | 1034 | } |
9ba69294 | 1035 | |
6db504ce | 1036 | mm_exiting: |
420be4ed | 1037 | remove_trailing_rmap_items(&mm_slot->rmap_list); |
d8ed45c5 | 1038 | mmap_read_unlock(mm); |
d952b791 HD |
1039 | |
1040 | spin_lock(&ksm_mmlist_lock); | |
58730ab6 QZ |
1041 | slot = list_entry(mm_slot->slot.mm_node.next, |
1042 | struct mm_slot, mm_node); | |
1043 | ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); | |
9ba69294 | 1044 | if (ksm_test_exit(mm)) { |
58730ab6 QZ |
1045 | hash_del(&mm_slot->slot.hash); |
1046 | list_del(&mm_slot->slot.mm_node); | |
9ba69294 HD |
1047 | spin_unlock(&ksm_mmlist_lock); |
1048 | ||
58730ab6 | 1049 | mm_slot_free(mm_slot_cache, mm_slot); |
9ba69294 | 1050 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
d7597f59 | 1051 | clear_bit(MMF_VM_MERGE_ANY, &mm->flags); |
9ba69294 | 1052 | mmdrop(mm); |
7496fea9 | 1053 | } else |
9ba69294 | 1054 | spin_unlock(&ksm_mmlist_lock); |
31dbd01f IE |
1055 | } |
1056 | ||
cbf86cfe HD |
1057 | /* Clean up stable nodes, but don't worry if some are still busy */ |
1058 | remove_all_stable_nodes(); | |
d952b791 | 1059 | ksm_scan.seqnr = 0; |
9ba69294 HD |
1060 | return 0; |
1061 | ||
1062 | error: | |
d8ed45c5 | 1063 | mmap_read_unlock(mm); |
31dbd01f | 1064 | spin_lock(&ksm_mmlist_lock); |
d952b791 | 1065 | ksm_scan.mm_slot = &ksm_mm_head; |
31dbd01f | 1066 | spin_unlock(&ksm_mmlist_lock); |
d952b791 | 1067 | return err; |
31dbd01f | 1068 | } |
2ffd8679 | 1069 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 1070 | |
31dbd01f IE |
1071 | static u32 calc_checksum(struct page *page) |
1072 | { | |
1073 | u32 checksum; | |
9b04c5fe | 1074 | void *addr = kmap_atomic(page); |
59e1a2f4 | 1075 | checksum = xxhash(addr, PAGE_SIZE, 0); |
9b04c5fe | 1076 | kunmap_atomic(addr); |
31dbd01f IE |
1077 | return checksum; |
1078 | } | |
1079 | ||
31dbd01f IE |
1080 | static int write_protect_page(struct vm_area_struct *vma, struct page *page, |
1081 | pte_t *orig_pte) | |
1082 | { | |
1083 | struct mm_struct *mm = vma->vm_mm; | |
eed05e54 | 1084 | DEFINE_PAGE_VMA_WALK(pvmw, page, vma, 0, 0); |
31dbd01f IE |
1085 | int swapped; |
1086 | int err = -EFAULT; | |
ac46d4f3 | 1087 | struct mmu_notifier_range range; |
6c287605 | 1088 | bool anon_exclusive; |
31dbd01f | 1089 | |
36eaff33 KS |
1090 | pvmw.address = page_address_in_vma(page, vma); |
1091 | if (pvmw.address == -EFAULT) | |
31dbd01f IE |
1092 | goto out; |
1093 | ||
29ad768c | 1094 | BUG_ON(PageTransCompound(page)); |
6bdb913f | 1095 | |
7d4a8be0 | 1096 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, pvmw.address, |
ac46d4f3 JG |
1097 | pvmw.address + PAGE_SIZE); |
1098 | mmu_notifier_invalidate_range_start(&range); | |
6bdb913f | 1099 | |
36eaff33 | 1100 | if (!page_vma_mapped_walk(&pvmw)) |
6bdb913f | 1101 | goto out_mn; |
36eaff33 KS |
1102 | if (WARN_ONCE(!pvmw.pte, "Unexpected PMD mapping?")) |
1103 | goto out_unlock; | |
31dbd01f | 1104 | |
6c287605 | 1105 | anon_exclusive = PageAnonExclusive(page); |
595cd8f2 | 1106 | if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) || |
6c287605 | 1107 | anon_exclusive || mm_tlb_flush_pending(mm)) { |
31dbd01f IE |
1108 | pte_t entry; |
1109 | ||
1110 | swapped = PageSwapCache(page); | |
36eaff33 | 1111 | flush_cache_page(vma, pvmw.address, page_to_pfn(page)); |
31dbd01f | 1112 | /* |
25985edc | 1113 | * Ok this is tricky, when get_user_pages_fast() run it doesn't |
31dbd01f | 1114 | * take any lock, therefore the check that we are going to make |
f0953a1b | 1115 | * with the pagecount against the mapcount is racy and |
31dbd01f IE |
1116 | * O_DIRECT can happen right after the check. |
1117 | * So we clear the pte and flush the tlb before the check | |
1118 | * this assure us that no O_DIRECT can happen after the check | |
1119 | * or in the middle of the check. | |
0f10851e JG |
1120 | * |
1121 | * No need to notify as we are downgrading page table to read | |
1122 | * only not changing it to point to a new page. | |
1123 | * | |
ee65728e | 1124 | * See Documentation/mm/mmu_notifier.rst |
31dbd01f | 1125 | */ |
0f10851e | 1126 | entry = ptep_clear_flush(vma, pvmw.address, pvmw.pte); |
31dbd01f IE |
1127 | /* |
1128 | * Check that no O_DIRECT or similar I/O is in progress on the | |
1129 | * page | |
1130 | */ | |
31e855ea | 1131 | if (page_mapcount(page) + 1 + swapped != page_count(page)) { |
36eaff33 | 1132 | set_pte_at(mm, pvmw.address, pvmw.pte, entry); |
31dbd01f IE |
1133 | goto out_unlock; |
1134 | } | |
6c287605 | 1135 | |
088b8aa5 | 1136 | /* See page_try_share_anon_rmap(): clear PTE first. */ |
6c287605 DH |
1137 | if (anon_exclusive && page_try_share_anon_rmap(page)) { |
1138 | set_pte_at(mm, pvmw.address, pvmw.pte, entry); | |
1139 | goto out_unlock; | |
1140 | } | |
1141 | ||
4e31635c HD |
1142 | if (pte_dirty(entry)) |
1143 | set_page_dirty(page); | |
6a56ccbc DH |
1144 | entry = pte_mkclean(entry); |
1145 | ||
1146 | if (pte_write(entry)) | |
1147 | entry = pte_wrprotect(entry); | |
595cd8f2 | 1148 | |
36eaff33 | 1149 | set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry); |
31dbd01f | 1150 | } |
36eaff33 | 1151 | *orig_pte = *pvmw.pte; |
31dbd01f IE |
1152 | err = 0; |
1153 | ||
1154 | out_unlock: | |
36eaff33 | 1155 | page_vma_mapped_walk_done(&pvmw); |
6bdb913f | 1156 | out_mn: |
ac46d4f3 | 1157 | mmu_notifier_invalidate_range_end(&range); |
31dbd01f IE |
1158 | out: |
1159 | return err; | |
1160 | } | |
1161 | ||
1162 | /** | |
1163 | * replace_page - replace page in vma by new ksm page | |
8dd3557a HD |
1164 | * @vma: vma that holds the pte pointing to page |
1165 | * @page: the page we are replacing by kpage | |
1166 | * @kpage: the ksm page we replace page by | |
31dbd01f IE |
1167 | * @orig_pte: the original value of the pte |
1168 | * | |
1169 | * Returns 0 on success, -EFAULT on failure. | |
1170 | */ | |
8dd3557a HD |
1171 | static int replace_page(struct vm_area_struct *vma, struct page *page, |
1172 | struct page *kpage, pte_t orig_pte) | |
31dbd01f IE |
1173 | { |
1174 | struct mm_struct *mm = vma->vm_mm; | |
b4e6f66e | 1175 | struct folio *folio; |
31dbd01f | 1176 | pmd_t *pmd; |
50722804 | 1177 | pmd_t pmde; |
31dbd01f | 1178 | pte_t *ptep; |
e86c59b1 | 1179 | pte_t newpte; |
31dbd01f IE |
1180 | spinlock_t *ptl; |
1181 | unsigned long addr; | |
31dbd01f | 1182 | int err = -EFAULT; |
ac46d4f3 | 1183 | struct mmu_notifier_range range; |
31dbd01f | 1184 | |
8dd3557a | 1185 | addr = page_address_in_vma(page, vma); |
31dbd01f IE |
1186 | if (addr == -EFAULT) |
1187 | goto out; | |
1188 | ||
6219049a BL |
1189 | pmd = mm_find_pmd(mm, addr); |
1190 | if (!pmd) | |
31dbd01f | 1191 | goto out; |
50722804 ZK |
1192 | /* |
1193 | * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() | |
1194 | * without holding anon_vma lock for write. So when looking for a | |
1195 | * genuine pmde (in which to find pte), test present and !THP together. | |
1196 | */ | |
1197 | pmde = *pmd; | |
1198 | barrier(); | |
1199 | if (!pmd_present(pmde) || pmd_trans_huge(pmde)) | |
1200 | goto out; | |
31dbd01f | 1201 | |
7d4a8be0 | 1202 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, addr, |
6f4f13e8 | 1203 | addr + PAGE_SIZE); |
ac46d4f3 | 1204 | mmu_notifier_invalidate_range_start(&range); |
6bdb913f | 1205 | |
31dbd01f IE |
1206 | ptep = pte_offset_map_lock(mm, pmd, addr, &ptl); |
1207 | if (!pte_same(*ptep, orig_pte)) { | |
1208 | pte_unmap_unlock(ptep, ptl); | |
6bdb913f | 1209 | goto out_mn; |
31dbd01f | 1210 | } |
6c287605 DH |
1211 | VM_BUG_ON_PAGE(PageAnonExclusive(page), page); |
1212 | VM_BUG_ON_PAGE(PageAnon(kpage) && PageAnonExclusive(kpage), kpage); | |
31dbd01f | 1213 | |
e86c59b1 CI |
1214 | /* |
1215 | * No need to check ksm_use_zero_pages here: we can only have a | |
457aef94 | 1216 | * zero_page here if ksm_use_zero_pages was enabled already. |
e86c59b1 CI |
1217 | */ |
1218 | if (!is_zero_pfn(page_to_pfn(kpage))) { | |
1219 | get_page(kpage); | |
f1e2db12 | 1220 | page_add_anon_rmap(kpage, vma, addr, RMAP_NONE); |
e86c59b1 CI |
1221 | newpte = mk_pte(kpage, vma->vm_page_prot); |
1222 | } else { | |
1223 | newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), | |
1224 | vma->vm_page_prot)); | |
a38c015f CI |
1225 | /* |
1226 | * We're replacing an anonymous page with a zero page, which is | |
1227 | * not anonymous. We need to do proper accounting otherwise we | |
1228 | * will get wrong values in /proc, and a BUG message in dmesg | |
1229 | * when tearing down the mm. | |
1230 | */ | |
1231 | dec_mm_counter(mm, MM_ANONPAGES); | |
e86c59b1 | 1232 | } |
31dbd01f IE |
1233 | |
1234 | flush_cache_page(vma, addr, pte_pfn(*ptep)); | |
0f10851e JG |
1235 | /* |
1236 | * No need to notify as we are replacing a read only page with another | |
1237 | * read only page with the same content. | |
1238 | * | |
ee65728e | 1239 | * See Documentation/mm/mmu_notifier.rst |
0f10851e JG |
1240 | */ |
1241 | ptep_clear_flush(vma, addr, ptep); | |
e86c59b1 | 1242 | set_pte_at_notify(mm, addr, ptep, newpte); |
31dbd01f | 1243 | |
b4e6f66e | 1244 | folio = page_folio(page); |
cea86fe2 | 1245 | page_remove_rmap(page, vma, false); |
b4e6f66e MWO |
1246 | if (!folio_mapped(folio)) |
1247 | folio_free_swap(folio); | |
1248 | folio_put(folio); | |
31dbd01f IE |
1249 | |
1250 | pte_unmap_unlock(ptep, ptl); | |
1251 | err = 0; | |
6bdb913f | 1252 | out_mn: |
ac46d4f3 | 1253 | mmu_notifier_invalidate_range_end(&range); |
31dbd01f IE |
1254 | out: |
1255 | return err; | |
1256 | } | |
1257 | ||
1258 | /* | |
1259 | * try_to_merge_one_page - take two pages and merge them into one | |
8dd3557a HD |
1260 | * @vma: the vma that holds the pte pointing to page |
1261 | * @page: the PageAnon page that we want to replace with kpage | |
80e14822 HD |
1262 | * @kpage: the PageKsm page that we want to map instead of page, |
1263 | * or NULL the first time when we want to use page as kpage. | |
31dbd01f IE |
1264 | * |
1265 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
1266 | */ | |
1267 | static int try_to_merge_one_page(struct vm_area_struct *vma, | |
8dd3557a | 1268 | struct page *page, struct page *kpage) |
31dbd01f IE |
1269 | { |
1270 | pte_t orig_pte = __pte(0); | |
1271 | int err = -EFAULT; | |
1272 | ||
db114b83 HD |
1273 | if (page == kpage) /* ksm page forked */ |
1274 | return 0; | |
1275 | ||
8dd3557a | 1276 | if (!PageAnon(page)) |
31dbd01f IE |
1277 | goto out; |
1278 | ||
31dbd01f IE |
1279 | /* |
1280 | * We need the page lock to read a stable PageSwapCache in | |
1281 | * write_protect_page(). We use trylock_page() instead of | |
1282 | * lock_page() because we don't want to wait here - we | |
1283 | * prefer to continue scanning and merging different pages, | |
1284 | * then come back to this page when it is unlocked. | |
1285 | */ | |
8dd3557a | 1286 | if (!trylock_page(page)) |
31e855ea | 1287 | goto out; |
f765f540 KS |
1288 | |
1289 | if (PageTransCompound(page)) { | |
a7306c34 | 1290 | if (split_huge_page(page)) |
f765f540 KS |
1291 | goto out_unlock; |
1292 | } | |
1293 | ||
31dbd01f IE |
1294 | /* |
1295 | * If this anonymous page is mapped only here, its pte may need | |
1296 | * to be write-protected. If it's mapped elsewhere, all of its | |
1297 | * ptes are necessarily already write-protected. But in either | |
1298 | * case, we need to lock and check page_count is not raised. | |
1299 | */ | |
80e14822 HD |
1300 | if (write_protect_page(vma, page, &orig_pte) == 0) { |
1301 | if (!kpage) { | |
1302 | /* | |
1303 | * While we hold page lock, upgrade page from | |
1304 | * PageAnon+anon_vma to PageKsm+NULL stable_node: | |
1305 | * stable_tree_insert() will update stable_node. | |
1306 | */ | |
1307 | set_page_stable_node(page, NULL); | |
1308 | mark_page_accessed(page); | |
337ed7eb MK |
1309 | /* |
1310 | * Page reclaim just frees a clean page with no dirty | |
1311 | * ptes: make sure that the ksm page would be swapped. | |
1312 | */ | |
1313 | if (!PageDirty(page)) | |
1314 | SetPageDirty(page); | |
80e14822 HD |
1315 | err = 0; |
1316 | } else if (pages_identical(page, kpage)) | |
1317 | err = replace_page(vma, page, kpage, orig_pte); | |
1318 | } | |
31dbd01f | 1319 | |
f765f540 | 1320 | out_unlock: |
8dd3557a | 1321 | unlock_page(page); |
31dbd01f IE |
1322 | out: |
1323 | return err; | |
1324 | } | |
1325 | ||
81464e30 HD |
1326 | /* |
1327 | * try_to_merge_with_ksm_page - like try_to_merge_two_pages, | |
1328 | * but no new kernel page is allocated: kpage must already be a ksm page. | |
8dd3557a HD |
1329 | * |
1330 | * This function returns 0 if the pages were merged, -EFAULT otherwise. | |
81464e30 | 1331 | */ |
21fbd591 | 1332 | static int try_to_merge_with_ksm_page(struct ksm_rmap_item *rmap_item, |
8dd3557a | 1333 | struct page *page, struct page *kpage) |
81464e30 | 1334 | { |
8dd3557a | 1335 | struct mm_struct *mm = rmap_item->mm; |
81464e30 HD |
1336 | struct vm_area_struct *vma; |
1337 | int err = -EFAULT; | |
1338 | ||
d8ed45c5 | 1339 | mmap_read_lock(mm); |
85c6e8dd AA |
1340 | vma = find_mergeable_vma(mm, rmap_item->address); |
1341 | if (!vma) | |
81464e30 HD |
1342 | goto out; |
1343 | ||
8dd3557a | 1344 | err = try_to_merge_one_page(vma, page, kpage); |
db114b83 HD |
1345 | if (err) |
1346 | goto out; | |
1347 | ||
bc56620b HD |
1348 | /* Unstable nid is in union with stable anon_vma: remove first */ |
1349 | remove_rmap_item_from_tree(rmap_item); | |
1350 | ||
c1e8d7c6 | 1351 | /* Must get reference to anon_vma while still holding mmap_lock */ |
9e60109f PZ |
1352 | rmap_item->anon_vma = vma->anon_vma; |
1353 | get_anon_vma(vma->anon_vma); | |
81464e30 | 1354 | out: |
d8ed45c5 | 1355 | mmap_read_unlock(mm); |
739100c8 SR |
1356 | trace_ksm_merge_with_ksm_page(kpage, page_to_pfn(kpage ? kpage : page), |
1357 | rmap_item, mm, err); | |
81464e30 HD |
1358 | return err; |
1359 | } | |
1360 | ||
31dbd01f IE |
1361 | /* |
1362 | * try_to_merge_two_pages - take two identical pages and prepare them | |
1363 | * to be merged into one page. | |
1364 | * | |
8dd3557a HD |
1365 | * This function returns the kpage if we successfully merged two identical |
1366 | * pages into one ksm page, NULL otherwise. | |
31dbd01f | 1367 | * |
80e14822 | 1368 | * Note that this function upgrades page to ksm page: if one of the pages |
31dbd01f IE |
1369 | * is already a ksm page, try_to_merge_with_ksm_page should be used. |
1370 | */ | |
21fbd591 | 1371 | static struct page *try_to_merge_two_pages(struct ksm_rmap_item *rmap_item, |
8dd3557a | 1372 | struct page *page, |
21fbd591 | 1373 | struct ksm_rmap_item *tree_rmap_item, |
8dd3557a | 1374 | struct page *tree_page) |
31dbd01f | 1375 | { |
80e14822 | 1376 | int err; |
31dbd01f | 1377 | |
80e14822 | 1378 | err = try_to_merge_with_ksm_page(rmap_item, page, NULL); |
31dbd01f | 1379 | if (!err) { |
8dd3557a | 1380 | err = try_to_merge_with_ksm_page(tree_rmap_item, |
80e14822 | 1381 | tree_page, page); |
31dbd01f | 1382 | /* |
81464e30 HD |
1383 | * If that fails, we have a ksm page with only one pte |
1384 | * pointing to it: so break it. | |
31dbd01f | 1385 | */ |
4035c07a | 1386 | if (err) |
8dd3557a | 1387 | break_cow(rmap_item); |
31dbd01f | 1388 | } |
80e14822 | 1389 | return err ? NULL : page; |
31dbd01f IE |
1390 | } |
1391 | ||
2c653d0e | 1392 | static __always_inline |
21fbd591 | 1393 | bool __is_page_sharing_candidate(struct ksm_stable_node *stable_node, int offset) |
2c653d0e AA |
1394 | { |
1395 | VM_BUG_ON(stable_node->rmap_hlist_len < 0); | |
1396 | /* | |
1397 | * Check that at least one mapping still exists, otherwise | |
1398 | * there's no much point to merge and share with this | |
1399 | * stable_node, as the underlying tree_page of the other | |
1400 | * sharer is going to be freed soon. | |
1401 | */ | |
1402 | return stable_node->rmap_hlist_len && | |
1403 | stable_node->rmap_hlist_len + offset < ksm_max_page_sharing; | |
1404 | } | |
1405 | ||
1406 | static __always_inline | |
21fbd591 | 1407 | bool is_page_sharing_candidate(struct ksm_stable_node *stable_node) |
2c653d0e AA |
1408 | { |
1409 | return __is_page_sharing_candidate(stable_node, 0); | |
1410 | } | |
1411 | ||
21fbd591 QZ |
1412 | static struct page *stable_node_dup(struct ksm_stable_node **_stable_node_dup, |
1413 | struct ksm_stable_node **_stable_node, | |
c01f0b54 CIK |
1414 | struct rb_root *root, |
1415 | bool prune_stale_stable_nodes) | |
2c653d0e | 1416 | { |
21fbd591 | 1417 | struct ksm_stable_node *dup, *found = NULL, *stable_node = *_stable_node; |
2c653d0e | 1418 | struct hlist_node *hlist_safe; |
8dc5ffcd | 1419 | struct page *_tree_page, *tree_page = NULL; |
2c653d0e AA |
1420 | int nr = 0; |
1421 | int found_rmap_hlist_len; | |
1422 | ||
1423 | if (!prune_stale_stable_nodes || | |
1424 | time_before(jiffies, stable_node->chain_prune_time + | |
1425 | msecs_to_jiffies( | |
1426 | ksm_stable_node_chains_prune_millisecs))) | |
1427 | prune_stale_stable_nodes = false; | |
1428 | else | |
1429 | stable_node->chain_prune_time = jiffies; | |
1430 | ||
1431 | hlist_for_each_entry_safe(dup, hlist_safe, | |
1432 | &stable_node->hlist, hlist_dup) { | |
1433 | cond_resched(); | |
1434 | /* | |
1435 | * We must walk all stable_node_dup to prune the stale | |
1436 | * stable nodes during lookup. | |
1437 | * | |
1438 | * get_ksm_page can drop the nodes from the | |
1439 | * stable_node->hlist if they point to freed pages | |
1440 | * (that's why we do a _safe walk). The "dup" | |
1441 | * stable_node parameter itself will be freed from | |
1442 | * under us if it returns NULL. | |
1443 | */ | |
2cee57d1 | 1444 | _tree_page = get_ksm_page(dup, GET_KSM_PAGE_NOLOCK); |
2c653d0e AA |
1445 | if (!_tree_page) |
1446 | continue; | |
1447 | nr += 1; | |
1448 | if (is_page_sharing_candidate(dup)) { | |
1449 | if (!found || | |
1450 | dup->rmap_hlist_len > found_rmap_hlist_len) { | |
1451 | if (found) | |
8dc5ffcd | 1452 | put_page(tree_page); |
2c653d0e AA |
1453 | found = dup; |
1454 | found_rmap_hlist_len = found->rmap_hlist_len; | |
8dc5ffcd | 1455 | tree_page = _tree_page; |
2c653d0e | 1456 | |
8dc5ffcd | 1457 | /* skip put_page for found dup */ |
2c653d0e AA |
1458 | if (!prune_stale_stable_nodes) |
1459 | break; | |
2c653d0e AA |
1460 | continue; |
1461 | } | |
1462 | } | |
1463 | put_page(_tree_page); | |
1464 | } | |
1465 | ||
80b18dfa AA |
1466 | if (found) { |
1467 | /* | |
1468 | * nr is counting all dups in the chain only if | |
1469 | * prune_stale_stable_nodes is true, otherwise we may | |
1470 | * break the loop at nr == 1 even if there are | |
1471 | * multiple entries. | |
1472 | */ | |
1473 | if (prune_stale_stable_nodes && nr == 1) { | |
2c653d0e AA |
1474 | /* |
1475 | * If there's not just one entry it would | |
1476 | * corrupt memory, better BUG_ON. In KSM | |
1477 | * context with no lock held it's not even | |
1478 | * fatal. | |
1479 | */ | |
1480 | BUG_ON(stable_node->hlist.first->next); | |
1481 | ||
1482 | /* | |
1483 | * There's just one entry and it is below the | |
1484 | * deduplication limit so drop the chain. | |
1485 | */ | |
1486 | rb_replace_node(&stable_node->node, &found->node, | |
1487 | root); | |
1488 | free_stable_node(stable_node); | |
1489 | ksm_stable_node_chains--; | |
1490 | ksm_stable_node_dups--; | |
b4fecc67 | 1491 | /* |
0ba1d0f7 AA |
1492 | * NOTE: the caller depends on the stable_node |
1493 | * to be equal to stable_node_dup if the chain | |
1494 | * was collapsed. | |
b4fecc67 | 1495 | */ |
0ba1d0f7 AA |
1496 | *_stable_node = found; |
1497 | /* | |
f0953a1b | 1498 | * Just for robustness, as stable_node is |
0ba1d0f7 AA |
1499 | * otherwise left as a stable pointer, the |
1500 | * compiler shall optimize it away at build | |
1501 | * time. | |
1502 | */ | |
1503 | stable_node = NULL; | |
80b18dfa AA |
1504 | } else if (stable_node->hlist.first != &found->hlist_dup && |
1505 | __is_page_sharing_candidate(found, 1)) { | |
2c653d0e | 1506 | /* |
80b18dfa AA |
1507 | * If the found stable_node dup can accept one |
1508 | * more future merge (in addition to the one | |
1509 | * that is underway) and is not at the head of | |
1510 | * the chain, put it there so next search will | |
1511 | * be quicker in the !prune_stale_stable_nodes | |
1512 | * case. | |
1513 | * | |
1514 | * NOTE: it would be inaccurate to use nr > 1 | |
1515 | * instead of checking the hlist.first pointer | |
1516 | * directly, because in the | |
1517 | * prune_stale_stable_nodes case "nr" isn't | |
1518 | * the position of the found dup in the chain, | |
1519 | * but the total number of dups in the chain. | |
2c653d0e AA |
1520 | */ |
1521 | hlist_del(&found->hlist_dup); | |
1522 | hlist_add_head(&found->hlist_dup, | |
1523 | &stable_node->hlist); | |
1524 | } | |
1525 | } | |
1526 | ||
8dc5ffcd AA |
1527 | *_stable_node_dup = found; |
1528 | return tree_page; | |
2c653d0e AA |
1529 | } |
1530 | ||
21fbd591 | 1531 | static struct ksm_stable_node *stable_node_dup_any(struct ksm_stable_node *stable_node, |
2c653d0e AA |
1532 | struct rb_root *root) |
1533 | { | |
1534 | if (!is_stable_node_chain(stable_node)) | |
1535 | return stable_node; | |
1536 | if (hlist_empty(&stable_node->hlist)) { | |
1537 | free_stable_node_chain(stable_node, root); | |
1538 | return NULL; | |
1539 | } | |
1540 | return hlist_entry(stable_node->hlist.first, | |
1541 | typeof(*stable_node), hlist_dup); | |
1542 | } | |
1543 | ||
8dc5ffcd AA |
1544 | /* |
1545 | * Like for get_ksm_page, this function can free the *_stable_node and | |
1546 | * *_stable_node_dup if the returned tree_page is NULL. | |
1547 | * | |
1548 | * It can also free and overwrite *_stable_node with the found | |
1549 | * stable_node_dup if the chain is collapsed (in which case | |
1550 | * *_stable_node will be equal to *_stable_node_dup like if the chain | |
1551 | * never existed). It's up to the caller to verify tree_page is not | |
1552 | * NULL before dereferencing *_stable_node or *_stable_node_dup. | |
1553 | * | |
1554 | * *_stable_node_dup is really a second output parameter of this | |
1555 | * function and will be overwritten in all cases, the caller doesn't | |
1556 | * need to initialize it. | |
1557 | */ | |
21fbd591 QZ |
1558 | static struct page *__stable_node_chain(struct ksm_stable_node **_stable_node_dup, |
1559 | struct ksm_stable_node **_stable_node, | |
8dc5ffcd AA |
1560 | struct rb_root *root, |
1561 | bool prune_stale_stable_nodes) | |
2c653d0e | 1562 | { |
21fbd591 | 1563 | struct ksm_stable_node *stable_node = *_stable_node; |
2c653d0e AA |
1564 | if (!is_stable_node_chain(stable_node)) { |
1565 | if (is_page_sharing_candidate(stable_node)) { | |
8dc5ffcd | 1566 | *_stable_node_dup = stable_node; |
2cee57d1 | 1567 | return get_ksm_page(stable_node, GET_KSM_PAGE_NOLOCK); |
2c653d0e | 1568 | } |
8dc5ffcd AA |
1569 | /* |
1570 | * _stable_node_dup set to NULL means the stable_node | |
1571 | * reached the ksm_max_page_sharing limit. | |
1572 | */ | |
1573 | *_stable_node_dup = NULL; | |
2c653d0e AA |
1574 | return NULL; |
1575 | } | |
8dc5ffcd | 1576 | return stable_node_dup(_stable_node_dup, _stable_node, root, |
2c653d0e AA |
1577 | prune_stale_stable_nodes); |
1578 | } | |
1579 | ||
21fbd591 QZ |
1580 | static __always_inline struct page *chain_prune(struct ksm_stable_node **s_n_d, |
1581 | struct ksm_stable_node **s_n, | |
8dc5ffcd | 1582 | struct rb_root *root) |
2c653d0e | 1583 | { |
8dc5ffcd | 1584 | return __stable_node_chain(s_n_d, s_n, root, true); |
2c653d0e AA |
1585 | } |
1586 | ||
21fbd591 QZ |
1587 | static __always_inline struct page *chain(struct ksm_stable_node **s_n_d, |
1588 | struct ksm_stable_node *s_n, | |
8dc5ffcd | 1589 | struct rb_root *root) |
2c653d0e | 1590 | { |
21fbd591 | 1591 | struct ksm_stable_node *old_stable_node = s_n; |
8dc5ffcd AA |
1592 | struct page *tree_page; |
1593 | ||
1594 | tree_page = __stable_node_chain(s_n_d, &s_n, root, false); | |
1595 | /* not pruning dups so s_n cannot have changed */ | |
1596 | VM_BUG_ON(s_n != old_stable_node); | |
1597 | return tree_page; | |
2c653d0e AA |
1598 | } |
1599 | ||
31dbd01f | 1600 | /* |
8dd3557a | 1601 | * stable_tree_search - search for page inside the stable tree |
31dbd01f IE |
1602 | * |
1603 | * This function checks if there is a page inside the stable tree | |
1604 | * with identical content to the page that we are scanning right now. | |
1605 | * | |
7b6ba2c7 | 1606 | * This function returns the stable tree node of identical content if found, |
31dbd01f IE |
1607 | * NULL otherwise. |
1608 | */ | |
62b61f61 | 1609 | static struct page *stable_tree_search(struct page *page) |
31dbd01f | 1610 | { |
90bd6fd3 | 1611 | int nid; |
ef53d16c | 1612 | struct rb_root *root; |
4146d2d6 HD |
1613 | struct rb_node **new; |
1614 | struct rb_node *parent; | |
21fbd591 QZ |
1615 | struct ksm_stable_node *stable_node, *stable_node_dup, *stable_node_any; |
1616 | struct ksm_stable_node *page_node; | |
31dbd01f | 1617 | |
4146d2d6 HD |
1618 | page_node = page_stable_node(page); |
1619 | if (page_node && page_node->head != &migrate_nodes) { | |
1620 | /* ksm page forked */ | |
08beca44 | 1621 | get_page(page); |
62b61f61 | 1622 | return page; |
08beca44 HD |
1623 | } |
1624 | ||
90bd6fd3 | 1625 | nid = get_kpfn_nid(page_to_pfn(page)); |
ef53d16c | 1626 | root = root_stable_tree + nid; |
4146d2d6 | 1627 | again: |
ef53d16c | 1628 | new = &root->rb_node; |
4146d2d6 | 1629 | parent = NULL; |
90bd6fd3 | 1630 | |
4146d2d6 | 1631 | while (*new) { |
4035c07a | 1632 | struct page *tree_page; |
31dbd01f IE |
1633 | int ret; |
1634 | ||
08beca44 | 1635 | cond_resched(); |
21fbd591 | 1636 | stable_node = rb_entry(*new, struct ksm_stable_node, node); |
2c653d0e | 1637 | stable_node_any = NULL; |
8dc5ffcd | 1638 | tree_page = chain_prune(&stable_node_dup, &stable_node, root); |
b4fecc67 AA |
1639 | /* |
1640 | * NOTE: stable_node may have been freed by | |
1641 | * chain_prune() if the returned stable_node_dup is | |
1642 | * not NULL. stable_node_dup may have been inserted in | |
1643 | * the rbtree instead as a regular stable_node (in | |
1644 | * order to collapse the stable_node chain if a single | |
0ba1d0f7 | 1645 | * stable_node dup was found in it). In such case the |
3413b2c8 | 1646 | * stable_node is overwritten by the callee to point |
0ba1d0f7 AA |
1647 | * to the stable_node_dup that was collapsed in the |
1648 | * stable rbtree and stable_node will be equal to | |
1649 | * stable_node_dup like if the chain never existed. | |
b4fecc67 | 1650 | */ |
2c653d0e AA |
1651 | if (!stable_node_dup) { |
1652 | /* | |
1653 | * Either all stable_node dups were full in | |
1654 | * this stable_node chain, or this chain was | |
1655 | * empty and should be rb_erased. | |
1656 | */ | |
1657 | stable_node_any = stable_node_dup_any(stable_node, | |
1658 | root); | |
1659 | if (!stable_node_any) { | |
1660 | /* rb_erase just run */ | |
1661 | goto again; | |
1662 | } | |
1663 | /* | |
1664 | * Take any of the stable_node dups page of | |
1665 | * this stable_node chain to let the tree walk | |
1666 | * continue. All KSM pages belonging to the | |
1667 | * stable_node dups in a stable_node chain | |
1668 | * have the same content and they're | |
457aef94 | 1669 | * write protected at all times. Any will work |
2c653d0e AA |
1670 | * fine to continue the walk. |
1671 | */ | |
2cee57d1 YS |
1672 | tree_page = get_ksm_page(stable_node_any, |
1673 | GET_KSM_PAGE_NOLOCK); | |
2c653d0e AA |
1674 | } |
1675 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); | |
f2e5ff85 AA |
1676 | if (!tree_page) { |
1677 | /* | |
1678 | * If we walked over a stale stable_node, | |
1679 | * get_ksm_page() will call rb_erase() and it | |
1680 | * may rebalance the tree from under us. So | |
1681 | * restart the search from scratch. Returning | |
1682 | * NULL would be safe too, but we'd generate | |
1683 | * false negative insertions just because some | |
1684 | * stable_node was stale. | |
1685 | */ | |
1686 | goto again; | |
1687 | } | |
31dbd01f | 1688 | |
4035c07a | 1689 | ret = memcmp_pages(page, tree_page); |
c8d6553b | 1690 | put_page(tree_page); |
31dbd01f | 1691 | |
4146d2d6 | 1692 | parent = *new; |
c8d6553b | 1693 | if (ret < 0) |
4146d2d6 | 1694 | new = &parent->rb_left; |
c8d6553b | 1695 | else if (ret > 0) |
4146d2d6 | 1696 | new = &parent->rb_right; |
c8d6553b | 1697 | else { |
2c653d0e AA |
1698 | if (page_node) { |
1699 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1700 | /* | |
1701 | * Test if the migrated page should be merged | |
1702 | * into a stable node dup. If the mapcount is | |
1703 | * 1 we can migrate it with another KSM page | |
1704 | * without adding it to the chain. | |
1705 | */ | |
1706 | if (page_mapcount(page) > 1) | |
1707 | goto chain_append; | |
1708 | } | |
1709 | ||
1710 | if (!stable_node_dup) { | |
1711 | /* | |
1712 | * If the stable_node is a chain and | |
1713 | * we got a payload match in memcmp | |
1714 | * but we cannot merge the scanned | |
1715 | * page in any of the existing | |
1716 | * stable_node dups because they're | |
1717 | * all full, we need to wait the | |
1718 | * scanned page to find itself a match | |
1719 | * in the unstable tree to create a | |
1720 | * brand new KSM page to add later to | |
1721 | * the dups of this stable_node. | |
1722 | */ | |
1723 | return NULL; | |
1724 | } | |
1725 | ||
c8d6553b HD |
1726 | /* |
1727 | * Lock and unlock the stable_node's page (which | |
1728 | * might already have been migrated) so that page | |
1729 | * migration is sure to notice its raised count. | |
1730 | * It would be more elegant to return stable_node | |
1731 | * than kpage, but that involves more changes. | |
1732 | */ | |
2cee57d1 YS |
1733 | tree_page = get_ksm_page(stable_node_dup, |
1734 | GET_KSM_PAGE_TRYLOCK); | |
1735 | ||
1736 | if (PTR_ERR(tree_page) == -EBUSY) | |
1737 | return ERR_PTR(-EBUSY); | |
1738 | ||
2c653d0e AA |
1739 | if (unlikely(!tree_page)) |
1740 | /* | |
1741 | * The tree may have been rebalanced, | |
1742 | * so re-evaluate parent and new. | |
1743 | */ | |
4146d2d6 | 1744 | goto again; |
2c653d0e AA |
1745 | unlock_page(tree_page); |
1746 | ||
1747 | if (get_kpfn_nid(stable_node_dup->kpfn) != | |
1748 | NUMA(stable_node_dup->nid)) { | |
1749 | put_page(tree_page); | |
1750 | goto replace; | |
1751 | } | |
1752 | return tree_page; | |
c8d6553b | 1753 | } |
31dbd01f IE |
1754 | } |
1755 | ||
4146d2d6 HD |
1756 | if (!page_node) |
1757 | return NULL; | |
1758 | ||
1759 | list_del(&page_node->list); | |
1760 | DO_NUMA(page_node->nid = nid); | |
1761 | rb_link_node(&page_node->node, parent, new); | |
ef53d16c | 1762 | rb_insert_color(&page_node->node, root); |
2c653d0e AA |
1763 | out: |
1764 | if (is_page_sharing_candidate(page_node)) { | |
1765 | get_page(page); | |
1766 | return page; | |
1767 | } else | |
1768 | return NULL; | |
4146d2d6 HD |
1769 | |
1770 | replace: | |
b4fecc67 AA |
1771 | /* |
1772 | * If stable_node was a chain and chain_prune collapsed it, | |
0ba1d0f7 AA |
1773 | * stable_node has been updated to be the new regular |
1774 | * stable_node. A collapse of the chain is indistinguishable | |
1775 | * from the case there was no chain in the stable | |
1776 | * rbtree. Otherwise stable_node is the chain and | |
1777 | * stable_node_dup is the dup to replace. | |
b4fecc67 | 1778 | */ |
0ba1d0f7 | 1779 | if (stable_node_dup == stable_node) { |
b4fecc67 AA |
1780 | VM_BUG_ON(is_stable_node_chain(stable_node_dup)); |
1781 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); | |
2c653d0e AA |
1782 | /* there is no chain */ |
1783 | if (page_node) { | |
1784 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1785 | list_del(&page_node->list); | |
1786 | DO_NUMA(page_node->nid = nid); | |
b4fecc67 AA |
1787 | rb_replace_node(&stable_node_dup->node, |
1788 | &page_node->node, | |
2c653d0e AA |
1789 | root); |
1790 | if (is_page_sharing_candidate(page_node)) | |
1791 | get_page(page); | |
1792 | else | |
1793 | page = NULL; | |
1794 | } else { | |
b4fecc67 | 1795 | rb_erase(&stable_node_dup->node, root); |
2c653d0e AA |
1796 | page = NULL; |
1797 | } | |
4146d2d6 | 1798 | } else { |
2c653d0e AA |
1799 | VM_BUG_ON(!is_stable_node_chain(stable_node)); |
1800 | __stable_node_dup_del(stable_node_dup); | |
1801 | if (page_node) { | |
1802 | VM_BUG_ON(page_node->head != &migrate_nodes); | |
1803 | list_del(&page_node->list); | |
1804 | DO_NUMA(page_node->nid = nid); | |
1805 | stable_node_chain_add_dup(page_node, stable_node); | |
1806 | if (is_page_sharing_candidate(page_node)) | |
1807 | get_page(page); | |
1808 | else | |
1809 | page = NULL; | |
1810 | } else { | |
1811 | page = NULL; | |
1812 | } | |
4146d2d6 | 1813 | } |
2c653d0e AA |
1814 | stable_node_dup->head = &migrate_nodes; |
1815 | list_add(&stable_node_dup->list, stable_node_dup->head); | |
4146d2d6 | 1816 | return page; |
2c653d0e AA |
1817 | |
1818 | chain_append: | |
1819 | /* stable_node_dup could be null if it reached the limit */ | |
1820 | if (!stable_node_dup) | |
1821 | stable_node_dup = stable_node_any; | |
b4fecc67 AA |
1822 | /* |
1823 | * If stable_node was a chain and chain_prune collapsed it, | |
0ba1d0f7 AA |
1824 | * stable_node has been updated to be the new regular |
1825 | * stable_node. A collapse of the chain is indistinguishable | |
1826 | * from the case there was no chain in the stable | |
1827 | * rbtree. Otherwise stable_node is the chain and | |
1828 | * stable_node_dup is the dup to replace. | |
b4fecc67 | 1829 | */ |
0ba1d0f7 | 1830 | if (stable_node_dup == stable_node) { |
b4fecc67 | 1831 | VM_BUG_ON(is_stable_node_dup(stable_node_dup)); |
2c653d0e AA |
1832 | /* chain is missing so create it */ |
1833 | stable_node = alloc_stable_node_chain(stable_node_dup, | |
1834 | root); | |
1835 | if (!stable_node) | |
1836 | return NULL; | |
1837 | } | |
1838 | /* | |
1839 | * Add this stable_node dup that was | |
1840 | * migrated to the stable_node chain | |
1841 | * of the current nid for this page | |
1842 | * content. | |
1843 | */ | |
b4fecc67 | 1844 | VM_BUG_ON(!is_stable_node_dup(stable_node_dup)); |
2c653d0e AA |
1845 | VM_BUG_ON(page_node->head != &migrate_nodes); |
1846 | list_del(&page_node->list); | |
1847 | DO_NUMA(page_node->nid = nid); | |
1848 | stable_node_chain_add_dup(page_node, stable_node); | |
1849 | goto out; | |
31dbd01f IE |
1850 | } |
1851 | ||
1852 | /* | |
e850dcf5 | 1853 | * stable_tree_insert - insert stable tree node pointing to new ksm page |
31dbd01f IE |
1854 | * into the stable tree. |
1855 | * | |
7b6ba2c7 HD |
1856 | * This function returns the stable tree node just allocated on success, |
1857 | * NULL otherwise. | |
31dbd01f | 1858 | */ |
21fbd591 | 1859 | static struct ksm_stable_node *stable_tree_insert(struct page *kpage) |
31dbd01f | 1860 | { |
90bd6fd3 PH |
1861 | int nid; |
1862 | unsigned long kpfn; | |
ef53d16c | 1863 | struct rb_root *root; |
90bd6fd3 | 1864 | struct rb_node **new; |
f2e5ff85 | 1865 | struct rb_node *parent; |
21fbd591 | 1866 | struct ksm_stable_node *stable_node, *stable_node_dup, *stable_node_any; |
2c653d0e | 1867 | bool need_chain = false; |
31dbd01f | 1868 | |
90bd6fd3 PH |
1869 | kpfn = page_to_pfn(kpage); |
1870 | nid = get_kpfn_nid(kpfn); | |
ef53d16c | 1871 | root = root_stable_tree + nid; |
f2e5ff85 AA |
1872 | again: |
1873 | parent = NULL; | |
ef53d16c | 1874 | new = &root->rb_node; |
90bd6fd3 | 1875 | |
31dbd01f | 1876 | while (*new) { |
4035c07a | 1877 | struct page *tree_page; |
31dbd01f IE |
1878 | int ret; |
1879 | ||
08beca44 | 1880 | cond_resched(); |
21fbd591 | 1881 | stable_node = rb_entry(*new, struct ksm_stable_node, node); |
2c653d0e | 1882 | stable_node_any = NULL; |
8dc5ffcd | 1883 | tree_page = chain(&stable_node_dup, stable_node, root); |
2c653d0e AA |
1884 | if (!stable_node_dup) { |
1885 | /* | |
1886 | * Either all stable_node dups were full in | |
1887 | * this stable_node chain, or this chain was | |
1888 | * empty and should be rb_erased. | |
1889 | */ | |
1890 | stable_node_any = stable_node_dup_any(stable_node, | |
1891 | root); | |
1892 | if (!stable_node_any) { | |
1893 | /* rb_erase just run */ | |
1894 | goto again; | |
1895 | } | |
1896 | /* | |
1897 | * Take any of the stable_node dups page of | |
1898 | * this stable_node chain to let the tree walk | |
1899 | * continue. All KSM pages belonging to the | |
1900 | * stable_node dups in a stable_node chain | |
1901 | * have the same content and they're | |
457aef94 | 1902 | * write protected at all times. Any will work |
2c653d0e AA |
1903 | * fine to continue the walk. |
1904 | */ | |
2cee57d1 YS |
1905 | tree_page = get_ksm_page(stable_node_any, |
1906 | GET_KSM_PAGE_NOLOCK); | |
2c653d0e AA |
1907 | } |
1908 | VM_BUG_ON(!stable_node_dup ^ !!stable_node_any); | |
f2e5ff85 AA |
1909 | if (!tree_page) { |
1910 | /* | |
1911 | * If we walked over a stale stable_node, | |
1912 | * get_ksm_page() will call rb_erase() and it | |
1913 | * may rebalance the tree from under us. So | |
1914 | * restart the search from scratch. Returning | |
1915 | * NULL would be safe too, but we'd generate | |
1916 | * false negative insertions just because some | |
1917 | * stable_node was stale. | |
1918 | */ | |
1919 | goto again; | |
1920 | } | |
31dbd01f | 1921 | |
4035c07a HD |
1922 | ret = memcmp_pages(kpage, tree_page); |
1923 | put_page(tree_page); | |
31dbd01f IE |
1924 | |
1925 | parent = *new; | |
1926 | if (ret < 0) | |
1927 | new = &parent->rb_left; | |
1928 | else if (ret > 0) | |
1929 | new = &parent->rb_right; | |
1930 | else { | |
2c653d0e AA |
1931 | need_chain = true; |
1932 | break; | |
31dbd01f IE |
1933 | } |
1934 | } | |
1935 | ||
2c653d0e AA |
1936 | stable_node_dup = alloc_stable_node(); |
1937 | if (!stable_node_dup) | |
7b6ba2c7 | 1938 | return NULL; |
31dbd01f | 1939 | |
2c653d0e AA |
1940 | INIT_HLIST_HEAD(&stable_node_dup->hlist); |
1941 | stable_node_dup->kpfn = kpfn; | |
1942 | set_page_stable_node(kpage, stable_node_dup); | |
1943 | stable_node_dup->rmap_hlist_len = 0; | |
1944 | DO_NUMA(stable_node_dup->nid = nid); | |
1945 | if (!need_chain) { | |
1946 | rb_link_node(&stable_node_dup->node, parent, new); | |
1947 | rb_insert_color(&stable_node_dup->node, root); | |
1948 | } else { | |
1949 | if (!is_stable_node_chain(stable_node)) { | |
21fbd591 | 1950 | struct ksm_stable_node *orig = stable_node; |
2c653d0e AA |
1951 | /* chain is missing so create it */ |
1952 | stable_node = alloc_stable_node_chain(orig, root); | |
1953 | if (!stable_node) { | |
1954 | free_stable_node(stable_node_dup); | |
1955 | return NULL; | |
1956 | } | |
1957 | } | |
1958 | stable_node_chain_add_dup(stable_node_dup, stable_node); | |
1959 | } | |
08beca44 | 1960 | |
2c653d0e | 1961 | return stable_node_dup; |
31dbd01f IE |
1962 | } |
1963 | ||
1964 | /* | |
8dd3557a HD |
1965 | * unstable_tree_search_insert - search for identical page, |
1966 | * else insert rmap_item into the unstable tree. | |
31dbd01f IE |
1967 | * |
1968 | * This function searches for a page in the unstable tree identical to the | |
1969 | * page currently being scanned; and if no identical page is found in the | |
1970 | * tree, we insert rmap_item as a new object into the unstable tree. | |
1971 | * | |
1972 | * This function returns pointer to rmap_item found to be identical | |
1973 | * to the currently scanned page, NULL otherwise. | |
1974 | * | |
1975 | * This function does both searching and inserting, because they share | |
1976 | * the same walking algorithm in an rbtree. | |
1977 | */ | |
8dd3557a | 1978 | static |
21fbd591 | 1979 | struct ksm_rmap_item *unstable_tree_search_insert(struct ksm_rmap_item *rmap_item, |
8dd3557a HD |
1980 | struct page *page, |
1981 | struct page **tree_pagep) | |
31dbd01f | 1982 | { |
90bd6fd3 PH |
1983 | struct rb_node **new; |
1984 | struct rb_root *root; | |
31dbd01f | 1985 | struct rb_node *parent = NULL; |
90bd6fd3 PH |
1986 | int nid; |
1987 | ||
1988 | nid = get_kpfn_nid(page_to_pfn(page)); | |
ef53d16c | 1989 | root = root_unstable_tree + nid; |
90bd6fd3 | 1990 | new = &root->rb_node; |
31dbd01f IE |
1991 | |
1992 | while (*new) { | |
21fbd591 | 1993 | struct ksm_rmap_item *tree_rmap_item; |
8dd3557a | 1994 | struct page *tree_page; |
31dbd01f IE |
1995 | int ret; |
1996 | ||
d178f27f | 1997 | cond_resched(); |
21fbd591 | 1998 | tree_rmap_item = rb_entry(*new, struct ksm_rmap_item, node); |
8dd3557a | 1999 | tree_page = get_mergeable_page(tree_rmap_item); |
c8f95ed1 | 2000 | if (!tree_page) |
31dbd01f IE |
2001 | return NULL; |
2002 | ||
2003 | /* | |
8dd3557a | 2004 | * Don't substitute a ksm page for a forked page. |
31dbd01f | 2005 | */ |
8dd3557a HD |
2006 | if (page == tree_page) { |
2007 | put_page(tree_page); | |
31dbd01f IE |
2008 | return NULL; |
2009 | } | |
2010 | ||
8dd3557a | 2011 | ret = memcmp_pages(page, tree_page); |
31dbd01f IE |
2012 | |
2013 | parent = *new; | |
2014 | if (ret < 0) { | |
8dd3557a | 2015 | put_page(tree_page); |
31dbd01f IE |
2016 | new = &parent->rb_left; |
2017 | } else if (ret > 0) { | |
8dd3557a | 2018 | put_page(tree_page); |
31dbd01f | 2019 | new = &parent->rb_right; |
b599cbdf HD |
2020 | } else if (!ksm_merge_across_nodes && |
2021 | page_to_nid(tree_page) != nid) { | |
2022 | /* | |
2023 | * If tree_page has been migrated to another NUMA node, | |
2024 | * it will be flushed out and put in the right unstable | |
2025 | * tree next time: only merge with it when across_nodes. | |
2026 | */ | |
2027 | put_page(tree_page); | |
2028 | return NULL; | |
31dbd01f | 2029 | } else { |
8dd3557a | 2030 | *tree_pagep = tree_page; |
31dbd01f IE |
2031 | return tree_rmap_item; |
2032 | } | |
2033 | } | |
2034 | ||
7b6ba2c7 | 2035 | rmap_item->address |= UNSTABLE_FLAG; |
31dbd01f | 2036 | rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK); |
e850dcf5 | 2037 | DO_NUMA(rmap_item->nid = nid); |
31dbd01f | 2038 | rb_link_node(&rmap_item->node, parent, new); |
90bd6fd3 | 2039 | rb_insert_color(&rmap_item->node, root); |
31dbd01f | 2040 | |
473b0ce4 | 2041 | ksm_pages_unshared++; |
31dbd01f IE |
2042 | return NULL; |
2043 | } | |
2044 | ||
2045 | /* | |
2046 | * stable_tree_append - add another rmap_item to the linked list of | |
2047 | * rmap_items hanging off a given node of the stable tree, all sharing | |
2048 | * the same ksm page. | |
2049 | */ | |
21fbd591 QZ |
2050 | static void stable_tree_append(struct ksm_rmap_item *rmap_item, |
2051 | struct ksm_stable_node *stable_node, | |
2c653d0e | 2052 | bool max_page_sharing_bypass) |
31dbd01f | 2053 | { |
2c653d0e AA |
2054 | /* |
2055 | * rmap won't find this mapping if we don't insert the | |
2056 | * rmap_item in the right stable_node | |
2057 | * duplicate. page_migration could break later if rmap breaks, | |
2058 | * so we can as well crash here. We really need to check for | |
2059 | * rmap_hlist_len == STABLE_NODE_CHAIN, but we can as well check | |
457aef94 | 2060 | * for other negative values as an underflow if detected here |
2c653d0e AA |
2061 | * for the first time (and not when decreasing rmap_hlist_len) |
2062 | * would be sign of memory corruption in the stable_node. | |
2063 | */ | |
2064 | BUG_ON(stable_node->rmap_hlist_len < 0); | |
2065 | ||
2066 | stable_node->rmap_hlist_len++; | |
2067 | if (!max_page_sharing_bypass) | |
2068 | /* possibly non fatal but unexpected overflow, only warn */ | |
2069 | WARN_ON_ONCE(stable_node->rmap_hlist_len > | |
2070 | ksm_max_page_sharing); | |
2071 | ||
7b6ba2c7 | 2072 | rmap_item->head = stable_node; |
31dbd01f | 2073 | rmap_item->address |= STABLE_FLAG; |
7b6ba2c7 | 2074 | hlist_add_head(&rmap_item->hlist, &stable_node->hlist); |
e178dfde | 2075 | |
7b6ba2c7 HD |
2076 | if (rmap_item->hlist.next) |
2077 | ksm_pages_sharing++; | |
2078 | else | |
2079 | ksm_pages_shared++; | |
76093853 | 2080 | |
2081 | rmap_item->mm->ksm_merging_pages++; | |
31dbd01f IE |
2082 | } |
2083 | ||
2084 | /* | |
81464e30 HD |
2085 | * cmp_and_merge_page - first see if page can be merged into the stable tree; |
2086 | * if not, compare checksum to previous and if it's the same, see if page can | |
2087 | * be inserted into the unstable tree, or merged with a page already there and | |
2088 | * both transferred to the stable tree. | |
31dbd01f IE |
2089 | * |
2090 | * @page: the page that we are searching identical page to. | |
2091 | * @rmap_item: the reverse mapping into the virtual address of this page | |
2092 | */ | |
21fbd591 | 2093 | static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_item) |
31dbd01f | 2094 | { |
4b22927f | 2095 | struct mm_struct *mm = rmap_item->mm; |
21fbd591 | 2096 | struct ksm_rmap_item *tree_rmap_item; |
8dd3557a | 2097 | struct page *tree_page = NULL; |
21fbd591 | 2098 | struct ksm_stable_node *stable_node; |
8dd3557a | 2099 | struct page *kpage; |
31dbd01f IE |
2100 | unsigned int checksum; |
2101 | int err; | |
2c653d0e | 2102 | bool max_page_sharing_bypass = false; |
31dbd01f | 2103 | |
4146d2d6 HD |
2104 | stable_node = page_stable_node(page); |
2105 | if (stable_node) { | |
2106 | if (stable_node->head != &migrate_nodes && | |
2c653d0e AA |
2107 | get_kpfn_nid(READ_ONCE(stable_node->kpfn)) != |
2108 | NUMA(stable_node->nid)) { | |
2109 | stable_node_dup_del(stable_node); | |
4146d2d6 HD |
2110 | stable_node->head = &migrate_nodes; |
2111 | list_add(&stable_node->list, stable_node->head); | |
2112 | } | |
2113 | if (stable_node->head != &migrate_nodes && | |
2114 | rmap_item->head == stable_node) | |
2115 | return; | |
2c653d0e AA |
2116 | /* |
2117 | * If it's a KSM fork, allow it to go over the sharing limit | |
2118 | * without warnings. | |
2119 | */ | |
2120 | if (!is_page_sharing_candidate(stable_node)) | |
2121 | max_page_sharing_bypass = true; | |
4146d2d6 | 2122 | } |
31dbd01f IE |
2123 | |
2124 | /* We first start with searching the page inside the stable tree */ | |
62b61f61 | 2125 | kpage = stable_tree_search(page); |
4146d2d6 HD |
2126 | if (kpage == page && rmap_item->head == stable_node) { |
2127 | put_page(kpage); | |
2128 | return; | |
2129 | } | |
2130 | ||
2131 | remove_rmap_item_from_tree(rmap_item); | |
2132 | ||
62b61f61 | 2133 | if (kpage) { |
2cee57d1 YS |
2134 | if (PTR_ERR(kpage) == -EBUSY) |
2135 | return; | |
2136 | ||
08beca44 | 2137 | err = try_to_merge_with_ksm_page(rmap_item, page, kpage); |
31dbd01f IE |
2138 | if (!err) { |
2139 | /* | |
2140 | * The page was successfully merged: | |
2141 | * add its rmap_item to the stable tree. | |
2142 | */ | |
5ad64688 | 2143 | lock_page(kpage); |
2c653d0e AA |
2144 | stable_tree_append(rmap_item, page_stable_node(kpage), |
2145 | max_page_sharing_bypass); | |
5ad64688 | 2146 | unlock_page(kpage); |
31dbd01f | 2147 | } |
8dd3557a | 2148 | put_page(kpage); |
31dbd01f IE |
2149 | return; |
2150 | } | |
2151 | ||
2152 | /* | |
4035c07a HD |
2153 | * If the hash value of the page has changed from the last time |
2154 | * we calculated it, this page is changing frequently: therefore we | |
2155 | * don't want to insert it in the unstable tree, and we don't want | |
2156 | * to waste our time searching for something identical to it there. | |
31dbd01f IE |
2157 | */ |
2158 | checksum = calc_checksum(page); | |
2159 | if (rmap_item->oldchecksum != checksum) { | |
2160 | rmap_item->oldchecksum = checksum; | |
2161 | return; | |
2162 | } | |
2163 | ||
e86c59b1 CI |
2164 | /* |
2165 | * Same checksum as an empty page. We attempt to merge it with the | |
2166 | * appropriate zero page if the user enabled this via sysfs. | |
2167 | */ | |
2168 | if (ksm_use_zero_pages && (checksum == zero_checksum)) { | |
2169 | struct vm_area_struct *vma; | |
2170 | ||
d8ed45c5 | 2171 | mmap_read_lock(mm); |
4b22927f | 2172 | vma = find_mergeable_vma(mm, rmap_item->address); |
56df70a6 MS |
2173 | if (vma) { |
2174 | err = try_to_merge_one_page(vma, page, | |
2175 | ZERO_PAGE(rmap_item->address)); | |
739100c8 SR |
2176 | trace_ksm_merge_one_page( |
2177 | page_to_pfn(ZERO_PAGE(rmap_item->address)), | |
2178 | rmap_item, mm, err); | |
56df70a6 MS |
2179 | } else { |
2180 | /* | |
2181 | * If the vma is out of date, we do not need to | |
2182 | * continue. | |
2183 | */ | |
2184 | err = 0; | |
2185 | } | |
d8ed45c5 | 2186 | mmap_read_unlock(mm); |
e86c59b1 CI |
2187 | /* |
2188 | * In case of failure, the page was not really empty, so we | |
2189 | * need to continue. Otherwise we're done. | |
2190 | */ | |
2191 | if (!err) | |
2192 | return; | |
2193 | } | |
8dd3557a HD |
2194 | tree_rmap_item = |
2195 | unstable_tree_search_insert(rmap_item, page, &tree_page); | |
31dbd01f | 2196 | if (tree_rmap_item) { |
77da2ba0 CI |
2197 | bool split; |
2198 | ||
8dd3557a HD |
2199 | kpage = try_to_merge_two_pages(rmap_item, page, |
2200 | tree_rmap_item, tree_page); | |
77da2ba0 CI |
2201 | /* |
2202 | * If both pages we tried to merge belong to the same compound | |
2203 | * page, then we actually ended up increasing the reference | |
2204 | * count of the same compound page twice, and split_huge_page | |
2205 | * failed. | |
2206 | * Here we set a flag if that happened, and we use it later to | |
2207 | * try split_huge_page again. Since we call put_page right | |
2208 | * afterwards, the reference count will be correct and | |
2209 | * split_huge_page should succeed. | |
2210 | */ | |
2211 | split = PageTransCompound(page) | |
2212 | && compound_head(page) == compound_head(tree_page); | |
8dd3557a | 2213 | put_page(tree_page); |
8dd3557a | 2214 | if (kpage) { |
bc56620b HD |
2215 | /* |
2216 | * The pages were successfully merged: insert new | |
2217 | * node in the stable tree and add both rmap_items. | |
2218 | */ | |
5ad64688 | 2219 | lock_page(kpage); |
7b6ba2c7 HD |
2220 | stable_node = stable_tree_insert(kpage); |
2221 | if (stable_node) { | |
2c653d0e AA |
2222 | stable_tree_append(tree_rmap_item, stable_node, |
2223 | false); | |
2224 | stable_tree_append(rmap_item, stable_node, | |
2225 | false); | |
7b6ba2c7 | 2226 | } |
5ad64688 | 2227 | unlock_page(kpage); |
7b6ba2c7 | 2228 | |
31dbd01f IE |
2229 | /* |
2230 | * If we fail to insert the page into the stable tree, | |
2231 | * we will have 2 virtual addresses that are pointing | |
2232 | * to a ksm page left outside the stable tree, | |
2233 | * in which case we need to break_cow on both. | |
2234 | */ | |
7b6ba2c7 | 2235 | if (!stable_node) { |
8dd3557a HD |
2236 | break_cow(tree_rmap_item); |
2237 | break_cow(rmap_item); | |
31dbd01f | 2238 | } |
77da2ba0 CI |
2239 | } else if (split) { |
2240 | /* | |
2241 | * We are here if we tried to merge two pages and | |
2242 | * failed because they both belonged to the same | |
2243 | * compound page. We will split the page now, but no | |
2244 | * merging will take place. | |
2245 | * We do not want to add the cost of a full lock; if | |
2246 | * the page is locked, it is better to skip it and | |
2247 | * perhaps try again later. | |
2248 | */ | |
2249 | if (!trylock_page(page)) | |
2250 | return; | |
2251 | split_huge_page(page); | |
2252 | unlock_page(page); | |
31dbd01f | 2253 | } |
31dbd01f IE |
2254 | } |
2255 | } | |
2256 | ||
21fbd591 QZ |
2257 | static struct ksm_rmap_item *get_next_rmap_item(struct ksm_mm_slot *mm_slot, |
2258 | struct ksm_rmap_item **rmap_list, | |
31dbd01f IE |
2259 | unsigned long addr) |
2260 | { | |
21fbd591 | 2261 | struct ksm_rmap_item *rmap_item; |
31dbd01f | 2262 | |
6514d511 HD |
2263 | while (*rmap_list) { |
2264 | rmap_item = *rmap_list; | |
93d17715 | 2265 | if ((rmap_item->address & PAGE_MASK) == addr) |
31dbd01f | 2266 | return rmap_item; |
31dbd01f IE |
2267 | if (rmap_item->address > addr) |
2268 | break; | |
6514d511 | 2269 | *rmap_list = rmap_item->rmap_list; |
31dbd01f | 2270 | remove_rmap_item_from_tree(rmap_item); |
31dbd01f IE |
2271 | free_rmap_item(rmap_item); |
2272 | } | |
2273 | ||
2274 | rmap_item = alloc_rmap_item(); | |
2275 | if (rmap_item) { | |
2276 | /* It has already been zeroed */ | |
58730ab6 | 2277 | rmap_item->mm = mm_slot->slot.mm; |
cb4df4ca | 2278 | rmap_item->mm->ksm_rmap_items++; |
31dbd01f | 2279 | rmap_item->address = addr; |
6514d511 HD |
2280 | rmap_item->rmap_list = *rmap_list; |
2281 | *rmap_list = rmap_item; | |
31dbd01f IE |
2282 | } |
2283 | return rmap_item; | |
2284 | } | |
2285 | ||
21fbd591 | 2286 | static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page) |
31dbd01f IE |
2287 | { |
2288 | struct mm_struct *mm; | |
58730ab6 QZ |
2289 | struct ksm_mm_slot *mm_slot; |
2290 | struct mm_slot *slot; | |
31dbd01f | 2291 | struct vm_area_struct *vma; |
21fbd591 | 2292 | struct ksm_rmap_item *rmap_item; |
a5f18ba0 | 2293 | struct vma_iterator vmi; |
90bd6fd3 | 2294 | int nid; |
31dbd01f | 2295 | |
58730ab6 | 2296 | if (list_empty(&ksm_mm_head.slot.mm_node)) |
31dbd01f IE |
2297 | return NULL; |
2298 | ||
58730ab6 QZ |
2299 | mm_slot = ksm_scan.mm_slot; |
2300 | if (mm_slot == &ksm_mm_head) { | |
739100c8 SR |
2301 | trace_ksm_start_scan(ksm_scan.seqnr, ksm_rmap_items); |
2302 | ||
2919bfd0 HD |
2303 | /* |
2304 | * A number of pages can hang around indefinitely on per-cpu | |
2305 | * pagevecs, raised page count preventing write_protect_page | |
2306 | * from merging them. Though it doesn't really matter much, | |
2307 | * it is puzzling to see some stuck in pages_volatile until | |
2308 | * other activity jostles them out, and they also prevented | |
2309 | * LTP's KSM test from succeeding deterministically; so drain | |
2310 | * them here (here rather than on entry to ksm_do_scan(), | |
2311 | * so we don't IPI too often when pages_to_scan is set low). | |
2312 | */ | |
2313 | lru_add_drain_all(); | |
2314 | ||
4146d2d6 HD |
2315 | /* |
2316 | * Whereas stale stable_nodes on the stable_tree itself | |
2317 | * get pruned in the regular course of stable_tree_search(), | |
2318 | * those moved out to the migrate_nodes list can accumulate: | |
2319 | * so prune them once before each full scan. | |
2320 | */ | |
2321 | if (!ksm_merge_across_nodes) { | |
21fbd591 | 2322 | struct ksm_stable_node *stable_node, *next; |
4146d2d6 HD |
2323 | struct page *page; |
2324 | ||
03640418 GT |
2325 | list_for_each_entry_safe(stable_node, next, |
2326 | &migrate_nodes, list) { | |
2cee57d1 YS |
2327 | page = get_ksm_page(stable_node, |
2328 | GET_KSM_PAGE_NOLOCK); | |
4146d2d6 HD |
2329 | if (page) |
2330 | put_page(page); | |
2331 | cond_resched(); | |
2332 | } | |
2333 | } | |
2334 | ||
ef53d16c | 2335 | for (nid = 0; nid < ksm_nr_node_ids; nid++) |
90bd6fd3 | 2336 | root_unstable_tree[nid] = RB_ROOT; |
31dbd01f IE |
2337 | |
2338 | spin_lock(&ksm_mmlist_lock); | |
58730ab6 QZ |
2339 | slot = list_entry(mm_slot->slot.mm_node.next, |
2340 | struct mm_slot, mm_node); | |
2341 | mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); | |
2342 | ksm_scan.mm_slot = mm_slot; | |
31dbd01f | 2343 | spin_unlock(&ksm_mmlist_lock); |
2b472611 HD |
2344 | /* |
2345 | * Although we tested list_empty() above, a racing __ksm_exit | |
2346 | * of the last mm on the list may have removed it since then. | |
2347 | */ | |
58730ab6 | 2348 | if (mm_slot == &ksm_mm_head) |
2b472611 | 2349 | return NULL; |
31dbd01f IE |
2350 | next_mm: |
2351 | ksm_scan.address = 0; | |
58730ab6 | 2352 | ksm_scan.rmap_list = &mm_slot->rmap_list; |
31dbd01f IE |
2353 | } |
2354 | ||
58730ab6 | 2355 | slot = &mm_slot->slot; |
31dbd01f | 2356 | mm = slot->mm; |
a5f18ba0 MWO |
2357 | vma_iter_init(&vmi, mm, ksm_scan.address); |
2358 | ||
d8ed45c5 | 2359 | mmap_read_lock(mm); |
9ba69294 | 2360 | if (ksm_test_exit(mm)) |
a5f18ba0 | 2361 | goto no_vmas; |
9ba69294 | 2362 | |
a5f18ba0 | 2363 | for_each_vma(vmi, vma) { |
31dbd01f IE |
2364 | if (!(vma->vm_flags & VM_MERGEABLE)) |
2365 | continue; | |
2366 | if (ksm_scan.address < vma->vm_start) | |
2367 | ksm_scan.address = vma->vm_start; | |
2368 | if (!vma->anon_vma) | |
2369 | ksm_scan.address = vma->vm_end; | |
2370 | ||
2371 | while (ksm_scan.address < vma->vm_end) { | |
9ba69294 HD |
2372 | if (ksm_test_exit(mm)) |
2373 | break; | |
31dbd01f | 2374 | *page = follow_page(vma, ksm_scan.address, FOLL_GET); |
f7091ed6 | 2375 | if (IS_ERR_OR_NULL(*page)) { |
21ae5b01 AA |
2376 | ksm_scan.address += PAGE_SIZE; |
2377 | cond_resched(); | |
2378 | continue; | |
2379 | } | |
f7091ed6 HW |
2380 | if (is_zone_device_page(*page)) |
2381 | goto next_page; | |
f765f540 | 2382 | if (PageAnon(*page)) { |
31dbd01f IE |
2383 | flush_anon_page(vma, *page, ksm_scan.address); |
2384 | flush_dcache_page(*page); | |
58730ab6 | 2385 | rmap_item = get_next_rmap_item(mm_slot, |
6514d511 | 2386 | ksm_scan.rmap_list, ksm_scan.address); |
31dbd01f | 2387 | if (rmap_item) { |
6514d511 HD |
2388 | ksm_scan.rmap_list = |
2389 | &rmap_item->rmap_list; | |
31dbd01f IE |
2390 | ksm_scan.address += PAGE_SIZE; |
2391 | } else | |
2392 | put_page(*page); | |
d8ed45c5 | 2393 | mmap_read_unlock(mm); |
31dbd01f IE |
2394 | return rmap_item; |
2395 | } | |
f7091ed6 | 2396 | next_page: |
21ae5b01 | 2397 | put_page(*page); |
31dbd01f IE |
2398 | ksm_scan.address += PAGE_SIZE; |
2399 | cond_resched(); | |
2400 | } | |
2401 | } | |
2402 | ||
9ba69294 | 2403 | if (ksm_test_exit(mm)) { |
a5f18ba0 | 2404 | no_vmas: |
9ba69294 | 2405 | ksm_scan.address = 0; |
58730ab6 | 2406 | ksm_scan.rmap_list = &mm_slot->rmap_list; |
9ba69294 | 2407 | } |
31dbd01f IE |
2408 | /* |
2409 | * Nuke all the rmap_items that are above this current rmap: | |
2410 | * because there were no VM_MERGEABLE vmas with such addresses. | |
2411 | */ | |
420be4ed | 2412 | remove_trailing_rmap_items(ksm_scan.rmap_list); |
31dbd01f IE |
2413 | |
2414 | spin_lock(&ksm_mmlist_lock); | |
58730ab6 QZ |
2415 | slot = list_entry(mm_slot->slot.mm_node.next, |
2416 | struct mm_slot, mm_node); | |
2417 | ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); | |
cd551f97 HD |
2418 | if (ksm_scan.address == 0) { |
2419 | /* | |
c1e8d7c6 | 2420 | * We've completed a full scan of all vmas, holding mmap_lock |
cd551f97 HD |
2421 | * throughout, and found no VM_MERGEABLE: so do the same as |
2422 | * __ksm_exit does to remove this mm from all our lists now. | |
9ba69294 HD |
2423 | * This applies either when cleaning up after __ksm_exit |
2424 | * (but beware: we can reach here even before __ksm_exit), | |
2425 | * or when all VM_MERGEABLE areas have been unmapped (and | |
c1e8d7c6 | 2426 | * mmap_lock then protects against race with MADV_MERGEABLE). |
cd551f97 | 2427 | */ |
58730ab6 QZ |
2428 | hash_del(&mm_slot->slot.hash); |
2429 | list_del(&mm_slot->slot.mm_node); | |
9ba69294 HD |
2430 | spin_unlock(&ksm_mmlist_lock); |
2431 | ||
58730ab6 | 2432 | mm_slot_free(mm_slot_cache, mm_slot); |
cd551f97 | 2433 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
d7597f59 | 2434 | clear_bit(MMF_VM_MERGE_ANY, &mm->flags); |
d8ed45c5 | 2435 | mmap_read_unlock(mm); |
9ba69294 HD |
2436 | mmdrop(mm); |
2437 | } else { | |
d8ed45c5 | 2438 | mmap_read_unlock(mm); |
7496fea9 | 2439 | /* |
3e4e28c5 | 2440 | * mmap_read_unlock(mm) first because after |
7496fea9 ZC |
2441 | * spin_unlock(&ksm_mmlist_lock) run, the "mm" may |
2442 | * already have been freed under us by __ksm_exit() | |
2443 | * because the "mm_slot" is still hashed and | |
2444 | * ksm_scan.mm_slot doesn't point to it anymore. | |
2445 | */ | |
2446 | spin_unlock(&ksm_mmlist_lock); | |
cd551f97 | 2447 | } |
31dbd01f IE |
2448 | |
2449 | /* Repeat until we've completed scanning the whole list */ | |
58730ab6 QZ |
2450 | mm_slot = ksm_scan.mm_slot; |
2451 | if (mm_slot != &ksm_mm_head) | |
31dbd01f IE |
2452 | goto next_mm; |
2453 | ||
739100c8 | 2454 | trace_ksm_stop_scan(ksm_scan.seqnr, ksm_rmap_items); |
31dbd01f IE |
2455 | ksm_scan.seqnr++; |
2456 | return NULL; | |
2457 | } | |
2458 | ||
2459 | /** | |
2460 | * ksm_do_scan - the ksm scanner main worker function. | |
b7701a5f | 2461 | * @scan_npages: number of pages we want to scan before we return. |
31dbd01f IE |
2462 | */ |
2463 | static void ksm_do_scan(unsigned int scan_npages) | |
2464 | { | |
21fbd591 | 2465 | struct ksm_rmap_item *rmap_item; |
3f649ab7 | 2466 | struct page *page; |
31dbd01f | 2467 | |
878aee7d | 2468 | while (scan_npages-- && likely(!freezing(current))) { |
31dbd01f IE |
2469 | cond_resched(); |
2470 | rmap_item = scan_get_next_rmap_item(&page); | |
2471 | if (!rmap_item) | |
2472 | return; | |
4146d2d6 | 2473 | cmp_and_merge_page(page, rmap_item); |
31dbd01f IE |
2474 | put_page(page); |
2475 | } | |
2476 | } | |
2477 | ||
6e158384 HD |
2478 | static int ksmd_should_run(void) |
2479 | { | |
58730ab6 | 2480 | return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.slot.mm_node); |
6e158384 HD |
2481 | } |
2482 | ||
31dbd01f IE |
2483 | static int ksm_scan_thread(void *nothing) |
2484 | { | |
fcf9a0ef KT |
2485 | unsigned int sleep_ms; |
2486 | ||
878aee7d | 2487 | set_freezable(); |
339aa624 | 2488 | set_user_nice(current, 5); |
31dbd01f IE |
2489 | |
2490 | while (!kthread_should_stop()) { | |
6e158384 | 2491 | mutex_lock(&ksm_thread_mutex); |
ef4d43a8 | 2492 | wait_while_offlining(); |
6e158384 | 2493 | if (ksmd_should_run()) |
31dbd01f | 2494 | ksm_do_scan(ksm_thread_pages_to_scan); |
6e158384 HD |
2495 | mutex_unlock(&ksm_thread_mutex); |
2496 | ||
878aee7d AA |
2497 | try_to_freeze(); |
2498 | ||
6e158384 | 2499 | if (ksmd_should_run()) { |
fcf9a0ef KT |
2500 | sleep_ms = READ_ONCE(ksm_thread_sleep_millisecs); |
2501 | wait_event_interruptible_timeout(ksm_iter_wait, | |
2502 | sleep_ms != READ_ONCE(ksm_thread_sleep_millisecs), | |
2503 | msecs_to_jiffies(sleep_ms)); | |
31dbd01f | 2504 | } else { |
878aee7d | 2505 | wait_event_freezable(ksm_thread_wait, |
6e158384 | 2506 | ksmd_should_run() || kthread_should_stop()); |
31dbd01f IE |
2507 | } |
2508 | } | |
2509 | return 0; | |
2510 | } | |
2511 | ||
d7597f59 SR |
2512 | static void __ksm_add_vma(struct vm_area_struct *vma) |
2513 | { | |
2514 | unsigned long vm_flags = vma->vm_flags; | |
2515 | ||
2516 | if (vm_flags & VM_MERGEABLE) | |
2517 | return; | |
2518 | ||
2519 | if (vma_ksm_compatible(vma)) | |
2520 | vm_flags_set(vma, VM_MERGEABLE); | |
2521 | } | |
2522 | ||
24139c07 DH |
2523 | static int __ksm_del_vma(struct vm_area_struct *vma) |
2524 | { | |
2525 | int err; | |
2526 | ||
2527 | if (!(vma->vm_flags & VM_MERGEABLE)) | |
2528 | return 0; | |
2529 | ||
2530 | if (vma->anon_vma) { | |
2531 | err = unmerge_ksm_pages(vma, vma->vm_start, vma->vm_end); | |
2532 | if (err) | |
2533 | return err; | |
2534 | } | |
2535 | ||
2536 | vm_flags_clear(vma, VM_MERGEABLE); | |
2537 | return 0; | |
2538 | } | |
d7597f59 SR |
2539 | /** |
2540 | * ksm_add_vma - Mark vma as mergeable if compatible | |
2541 | * | |
2542 | * @vma: Pointer to vma | |
2543 | */ | |
2544 | void ksm_add_vma(struct vm_area_struct *vma) | |
2545 | { | |
2546 | struct mm_struct *mm = vma->vm_mm; | |
2547 | ||
2548 | if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) | |
2549 | __ksm_add_vma(vma); | |
2550 | } | |
2551 | ||
2552 | static void ksm_add_vmas(struct mm_struct *mm) | |
2553 | { | |
2554 | struct vm_area_struct *vma; | |
2555 | ||
2556 | VMA_ITERATOR(vmi, mm, 0); | |
2557 | for_each_vma(vmi, vma) | |
2558 | __ksm_add_vma(vma); | |
2559 | } | |
2560 | ||
24139c07 DH |
2561 | static int ksm_del_vmas(struct mm_struct *mm) |
2562 | { | |
2563 | struct vm_area_struct *vma; | |
2564 | int err; | |
2565 | ||
2566 | VMA_ITERATOR(vmi, mm, 0); | |
2567 | for_each_vma(vmi, vma) { | |
2568 | err = __ksm_del_vma(vma); | |
2569 | if (err) | |
2570 | return err; | |
2571 | } | |
2572 | return 0; | |
2573 | } | |
2574 | ||
d7597f59 SR |
2575 | /** |
2576 | * ksm_enable_merge_any - Add mm to mm ksm list and enable merging on all | |
2577 | * compatible VMA's | |
2578 | * | |
2579 | * @mm: Pointer to mm | |
2580 | * | |
2581 | * Returns 0 on success, otherwise error code | |
2582 | */ | |
2583 | int ksm_enable_merge_any(struct mm_struct *mm) | |
2584 | { | |
2585 | int err; | |
2586 | ||
2587 | if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) | |
2588 | return 0; | |
2589 | ||
2590 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { | |
2591 | err = __ksm_enter(mm); | |
2592 | if (err) | |
2593 | return err; | |
2594 | } | |
2595 | ||
2596 | set_bit(MMF_VM_MERGE_ANY, &mm->flags); | |
2597 | ksm_add_vmas(mm); | |
2598 | ||
2599 | return 0; | |
2600 | } | |
2601 | ||
24139c07 DH |
2602 | /** |
2603 | * ksm_disable_merge_any - Disable merging on all compatible VMA's of the mm, | |
2604 | * previously enabled via ksm_enable_merge_any(). | |
2605 | * | |
2606 | * Disabling merging implies unmerging any merged pages, like setting | |
2607 | * MADV_UNMERGEABLE would. If unmerging fails, the whole operation fails and | |
2608 | * merging on all compatible VMA's remains enabled. | |
2609 | * | |
2610 | * @mm: Pointer to mm | |
2611 | * | |
2612 | * Returns 0 on success, otherwise error code | |
2613 | */ | |
2614 | int ksm_disable_merge_any(struct mm_struct *mm) | |
2615 | { | |
2616 | int err; | |
2617 | ||
2618 | if (!test_bit(MMF_VM_MERGE_ANY, &mm->flags)) | |
2619 | return 0; | |
2620 | ||
2621 | err = ksm_del_vmas(mm); | |
2622 | if (err) { | |
2623 | ksm_add_vmas(mm); | |
2624 | return err; | |
2625 | } | |
2626 | ||
2627 | clear_bit(MMF_VM_MERGE_ANY, &mm->flags); | |
2628 | return 0; | |
2629 | } | |
2630 | ||
2c281f54 DH |
2631 | int ksm_disable(struct mm_struct *mm) |
2632 | { | |
2633 | mmap_assert_write_locked(mm); | |
2634 | ||
2635 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) | |
2636 | return 0; | |
2637 | if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) | |
2638 | return ksm_disable_merge_any(mm); | |
2639 | return ksm_del_vmas(mm); | |
2640 | } | |
2641 | ||
f8af4da3 HD |
2642 | int ksm_madvise(struct vm_area_struct *vma, unsigned long start, |
2643 | unsigned long end, int advice, unsigned long *vm_flags) | |
2644 | { | |
2645 | struct mm_struct *mm = vma->vm_mm; | |
d952b791 | 2646 | int err; |
f8af4da3 HD |
2647 | |
2648 | switch (advice) { | |
2649 | case MADV_MERGEABLE: | |
d7597f59 | 2650 | if (vma->vm_flags & VM_MERGEABLE) |
e1fb4a08 | 2651 | return 0; |
d7597f59 | 2652 | if (!vma_ksm_compatible(vma)) |
74a04967 | 2653 | return 0; |
cc2383ec | 2654 | |
d952b791 HD |
2655 | if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { |
2656 | err = __ksm_enter(mm); | |
2657 | if (err) | |
2658 | return err; | |
2659 | } | |
f8af4da3 HD |
2660 | |
2661 | *vm_flags |= VM_MERGEABLE; | |
2662 | break; | |
2663 | ||
2664 | case MADV_UNMERGEABLE: | |
2665 | if (!(*vm_flags & VM_MERGEABLE)) | |
2666 | return 0; /* just ignore the advice */ | |
2667 | ||
d952b791 HD |
2668 | if (vma->anon_vma) { |
2669 | err = unmerge_ksm_pages(vma, start, end); | |
2670 | if (err) | |
2671 | return err; | |
2672 | } | |
f8af4da3 HD |
2673 | |
2674 | *vm_flags &= ~VM_MERGEABLE; | |
2675 | break; | |
2676 | } | |
2677 | ||
2678 | return 0; | |
2679 | } | |
33cf1707 | 2680 | EXPORT_SYMBOL_GPL(ksm_madvise); |
f8af4da3 HD |
2681 | |
2682 | int __ksm_enter(struct mm_struct *mm) | |
2683 | { | |
21fbd591 | 2684 | struct ksm_mm_slot *mm_slot; |
58730ab6 | 2685 | struct mm_slot *slot; |
6e158384 HD |
2686 | int needs_wakeup; |
2687 | ||
58730ab6 | 2688 | mm_slot = mm_slot_alloc(mm_slot_cache); |
31dbd01f IE |
2689 | if (!mm_slot) |
2690 | return -ENOMEM; | |
2691 | ||
58730ab6 QZ |
2692 | slot = &mm_slot->slot; |
2693 | ||
6e158384 | 2694 | /* Check ksm_run too? Would need tighter locking */ |
58730ab6 | 2695 | needs_wakeup = list_empty(&ksm_mm_head.slot.mm_node); |
6e158384 | 2696 | |
31dbd01f | 2697 | spin_lock(&ksm_mmlist_lock); |
58730ab6 | 2698 | mm_slot_insert(mm_slots_hash, mm, slot); |
31dbd01f | 2699 | /* |
cbf86cfe HD |
2700 | * When KSM_RUN_MERGE (or KSM_RUN_STOP), |
2701 | * insert just behind the scanning cursor, to let the area settle | |
31dbd01f IE |
2702 | * down a little; when fork is followed by immediate exec, we don't |
2703 | * want ksmd to waste time setting up and tearing down an rmap_list. | |
cbf86cfe HD |
2704 | * |
2705 | * But when KSM_RUN_UNMERGE, it's important to insert ahead of its | |
2706 | * scanning cursor, otherwise KSM pages in newly forked mms will be | |
2707 | * missed: then we might as well insert at the end of the list. | |
31dbd01f | 2708 | */ |
cbf86cfe | 2709 | if (ksm_run & KSM_RUN_UNMERGE) |
58730ab6 | 2710 | list_add_tail(&slot->mm_node, &ksm_mm_head.slot.mm_node); |
cbf86cfe | 2711 | else |
58730ab6 | 2712 | list_add_tail(&slot->mm_node, &ksm_scan.mm_slot->slot.mm_node); |
31dbd01f IE |
2713 | spin_unlock(&ksm_mmlist_lock); |
2714 | ||
f8af4da3 | 2715 | set_bit(MMF_VM_MERGEABLE, &mm->flags); |
f1f10076 | 2716 | mmgrab(mm); |
6e158384 HD |
2717 | |
2718 | if (needs_wakeup) | |
2719 | wake_up_interruptible(&ksm_thread_wait); | |
2720 | ||
739100c8 | 2721 | trace_ksm_enter(mm); |
f8af4da3 HD |
2722 | return 0; |
2723 | } | |
2724 | ||
1c2fb7a4 | 2725 | void __ksm_exit(struct mm_struct *mm) |
f8af4da3 | 2726 | { |
21fbd591 | 2727 | struct ksm_mm_slot *mm_slot; |
58730ab6 | 2728 | struct mm_slot *slot; |
9ba69294 | 2729 | int easy_to_free = 0; |
cd551f97 | 2730 | |
31dbd01f | 2731 | /* |
9ba69294 HD |
2732 | * This process is exiting: if it's straightforward (as is the |
2733 | * case when ksmd was never running), free mm_slot immediately. | |
2734 | * But if it's at the cursor or has rmap_items linked to it, use | |
c1e8d7c6 | 2735 | * mmap_lock to synchronize with any break_cows before pagetables |
9ba69294 HD |
2736 | * are freed, and leave the mm_slot on the list for ksmd to free. |
2737 | * Beware: ksm may already have noticed it exiting and freed the slot. | |
31dbd01f | 2738 | */ |
9ba69294 | 2739 | |
cd551f97 | 2740 | spin_lock(&ksm_mmlist_lock); |
58730ab6 QZ |
2741 | slot = mm_slot_lookup(mm_slots_hash, mm); |
2742 | mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); | |
9ba69294 | 2743 | if (mm_slot && ksm_scan.mm_slot != mm_slot) { |
6514d511 | 2744 | if (!mm_slot->rmap_list) { |
58730ab6 QZ |
2745 | hash_del(&slot->hash); |
2746 | list_del(&slot->mm_node); | |
9ba69294 HD |
2747 | easy_to_free = 1; |
2748 | } else { | |
58730ab6 QZ |
2749 | list_move(&slot->mm_node, |
2750 | &ksm_scan.mm_slot->slot.mm_node); | |
9ba69294 | 2751 | } |
cd551f97 | 2752 | } |
cd551f97 HD |
2753 | spin_unlock(&ksm_mmlist_lock); |
2754 | ||
9ba69294 | 2755 | if (easy_to_free) { |
58730ab6 | 2756 | mm_slot_free(mm_slot_cache, mm_slot); |
d7597f59 | 2757 | clear_bit(MMF_VM_MERGE_ANY, &mm->flags); |
9ba69294 HD |
2758 | clear_bit(MMF_VM_MERGEABLE, &mm->flags); |
2759 | mmdrop(mm); | |
2760 | } else if (mm_slot) { | |
d8ed45c5 ML |
2761 | mmap_write_lock(mm); |
2762 | mmap_write_unlock(mm); | |
9ba69294 | 2763 | } |
739100c8 SR |
2764 | |
2765 | trace_ksm_exit(mm); | |
31dbd01f IE |
2766 | } |
2767 | ||
cbf86cfe | 2768 | struct page *ksm_might_need_to_copy(struct page *page, |
5ad64688 HD |
2769 | struct vm_area_struct *vma, unsigned long address) |
2770 | { | |
e05b3453 MWO |
2771 | struct folio *folio = page_folio(page); |
2772 | struct anon_vma *anon_vma = folio_anon_vma(folio); | |
5ad64688 HD |
2773 | struct page *new_page; |
2774 | ||
cbf86cfe HD |
2775 | if (PageKsm(page)) { |
2776 | if (page_stable_node(page) && | |
2777 | !(ksm_run & KSM_RUN_UNMERGE)) | |
2778 | return page; /* no need to copy it */ | |
2779 | } else if (!anon_vma) { | |
2780 | return page; /* no need to copy it */ | |
e1c63e11 NS |
2781 | } else if (page->index == linear_page_index(vma, address) && |
2782 | anon_vma->root == vma->anon_vma->root) { | |
cbf86cfe HD |
2783 | return page; /* still no need to copy it */ |
2784 | } | |
2785 | if (!PageUptodate(page)) | |
2786 | return page; /* let do_swap_page report the error */ | |
2787 | ||
5ad64688 | 2788 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); |
8f425e4e MWO |
2789 | if (new_page && |
2790 | mem_cgroup_charge(page_folio(new_page), vma->vm_mm, GFP_KERNEL)) { | |
62fdb163 HD |
2791 | put_page(new_page); |
2792 | new_page = NULL; | |
2793 | } | |
5ad64688 | 2794 | if (new_page) { |
6b970599 KW |
2795 | if (copy_mc_user_highpage(new_page, page, address, vma)) { |
2796 | put_page(new_page); | |
2797 | memory_failure_queue(page_to_pfn(page), 0); | |
2798 | return ERR_PTR(-EHWPOISON); | |
2799 | } | |
5ad64688 HD |
2800 | SetPageDirty(new_page); |
2801 | __SetPageUptodate(new_page); | |
48c935ad | 2802 | __SetPageLocked(new_page); |
4d45c3af YY |
2803 | #ifdef CONFIG_SWAP |
2804 | count_vm_event(KSM_SWPIN_COPY); | |
2805 | #endif | |
5ad64688 HD |
2806 | } |
2807 | ||
5ad64688 HD |
2808 | return new_page; |
2809 | } | |
2810 | ||
6d4675e6 | 2811 | void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc) |
e9995ef9 | 2812 | { |
21fbd591 QZ |
2813 | struct ksm_stable_node *stable_node; |
2814 | struct ksm_rmap_item *rmap_item; | |
e9995ef9 HD |
2815 | int search_new_forks = 0; |
2816 | ||
2f031c6f | 2817 | VM_BUG_ON_FOLIO(!folio_test_ksm(folio), folio); |
9f32624b JK |
2818 | |
2819 | /* | |
2820 | * Rely on the page lock to protect against concurrent modifications | |
2821 | * to that page's node of the stable tree. | |
2822 | */ | |
2f031c6f | 2823 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
e9995ef9 | 2824 | |
2f031c6f | 2825 | stable_node = folio_stable_node(folio); |
e9995ef9 | 2826 | if (!stable_node) |
1df631ae | 2827 | return; |
e9995ef9 | 2828 | again: |
b67bfe0d | 2829 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { |
e9995ef9 | 2830 | struct anon_vma *anon_vma = rmap_item->anon_vma; |
5beb4930 | 2831 | struct anon_vma_chain *vmac; |
e9995ef9 HD |
2832 | struct vm_area_struct *vma; |
2833 | ||
ad12695f | 2834 | cond_resched(); |
6d4675e6 MK |
2835 | if (!anon_vma_trylock_read(anon_vma)) { |
2836 | if (rwc->try_lock) { | |
2837 | rwc->contended = true; | |
2838 | return; | |
2839 | } | |
2840 | anon_vma_lock_read(anon_vma); | |
2841 | } | |
bf181b9f ML |
2842 | anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root, |
2843 | 0, ULONG_MAX) { | |
1105a2fc JH |
2844 | unsigned long addr; |
2845 | ||
ad12695f | 2846 | cond_resched(); |
5beb4930 | 2847 | vma = vmac->vma; |
1105a2fc JH |
2848 | |
2849 | /* Ignore the stable/unstable/sqnr flags */ | |
cd7fae26 | 2850 | addr = rmap_item->address & PAGE_MASK; |
1105a2fc JH |
2851 | |
2852 | if (addr < vma->vm_start || addr >= vma->vm_end) | |
e9995ef9 HD |
2853 | continue; |
2854 | /* | |
2855 | * Initially we examine only the vma which covers this | |
2856 | * rmap_item; but later, if there is still work to do, | |
2857 | * we examine covering vmas in other mms: in case they | |
2858 | * were forked from the original since ksmd passed. | |
2859 | */ | |
2860 | if ((rmap_item->mm == vma->vm_mm) == search_new_forks) | |
2861 | continue; | |
2862 | ||
0dd1c7bb JK |
2863 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
2864 | continue; | |
2865 | ||
2f031c6f | 2866 | if (!rwc->rmap_one(folio, vma, addr, rwc->arg)) { |
b6b19f25 | 2867 | anon_vma_unlock_read(anon_vma); |
1df631ae | 2868 | return; |
e9995ef9 | 2869 | } |
2f031c6f | 2870 | if (rwc->done && rwc->done(folio)) { |
0dd1c7bb | 2871 | anon_vma_unlock_read(anon_vma); |
1df631ae | 2872 | return; |
0dd1c7bb | 2873 | } |
e9995ef9 | 2874 | } |
b6b19f25 | 2875 | anon_vma_unlock_read(anon_vma); |
e9995ef9 HD |
2876 | } |
2877 | if (!search_new_forks++) | |
2878 | goto again; | |
e9995ef9 HD |
2879 | } |
2880 | ||
4248d008 LX |
2881 | #ifdef CONFIG_MEMORY_FAILURE |
2882 | /* | |
2883 | * Collect processes when the error hit an ksm page. | |
2884 | */ | |
2885 | void collect_procs_ksm(struct page *page, struct list_head *to_kill, | |
2886 | int force_early) | |
2887 | { | |
2888 | struct ksm_stable_node *stable_node; | |
2889 | struct ksm_rmap_item *rmap_item; | |
2890 | struct folio *folio = page_folio(page); | |
2891 | struct vm_area_struct *vma; | |
2892 | struct task_struct *tsk; | |
2893 | ||
2894 | stable_node = folio_stable_node(folio); | |
2895 | if (!stable_node) | |
2896 | return; | |
2897 | hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) { | |
2898 | struct anon_vma *av = rmap_item->anon_vma; | |
2899 | ||
2900 | anon_vma_lock_read(av); | |
2901 | read_lock(&tasklist_lock); | |
2902 | for_each_process(tsk) { | |
2903 | struct anon_vma_chain *vmac; | |
2904 | unsigned long addr; | |
2905 | struct task_struct *t = | |
2906 | task_early_kill(tsk, force_early); | |
2907 | if (!t) | |
2908 | continue; | |
2909 | anon_vma_interval_tree_foreach(vmac, &av->rb_root, 0, | |
2910 | ULONG_MAX) | |
2911 | { | |
2912 | vma = vmac->vma; | |
2913 | if (vma->vm_mm == t->mm) { | |
2914 | addr = rmap_item->address & PAGE_MASK; | |
2915 | add_to_kill_ksm(t, page, vma, to_kill, | |
2916 | addr); | |
2917 | } | |
2918 | } | |
2919 | } | |
2920 | read_unlock(&tasklist_lock); | |
2921 | anon_vma_unlock_read(av); | |
2922 | } | |
2923 | } | |
2924 | #endif | |
2925 | ||
52629506 | 2926 | #ifdef CONFIG_MIGRATION |
19138349 | 2927 | void folio_migrate_ksm(struct folio *newfolio, struct folio *folio) |
e9995ef9 | 2928 | { |
21fbd591 | 2929 | struct ksm_stable_node *stable_node; |
e9995ef9 | 2930 | |
19138349 MWO |
2931 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
2932 | VM_BUG_ON_FOLIO(!folio_test_locked(newfolio), newfolio); | |
2933 | VM_BUG_ON_FOLIO(newfolio->mapping != folio->mapping, newfolio); | |
e9995ef9 | 2934 | |
19138349 | 2935 | stable_node = folio_stable_node(folio); |
e9995ef9 | 2936 | if (stable_node) { |
19138349 MWO |
2937 | VM_BUG_ON_FOLIO(stable_node->kpfn != folio_pfn(folio), folio); |
2938 | stable_node->kpfn = folio_pfn(newfolio); | |
c8d6553b | 2939 | /* |
19138349 | 2940 | * newfolio->mapping was set in advance; now we need smp_wmb() |
c8d6553b | 2941 | * to make sure that the new stable_node->kpfn is visible |
19138349 MWO |
2942 | * to get_ksm_page() before it can see that folio->mapping |
2943 | * has gone stale (or that folio_test_swapcache has been cleared). | |
c8d6553b HD |
2944 | */ |
2945 | smp_wmb(); | |
19138349 | 2946 | set_page_stable_node(&folio->page, NULL); |
e9995ef9 HD |
2947 | } |
2948 | } | |
2949 | #endif /* CONFIG_MIGRATION */ | |
2950 | ||
62b61f61 | 2951 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 HD |
2952 | static void wait_while_offlining(void) |
2953 | { | |
2954 | while (ksm_run & KSM_RUN_OFFLINE) { | |
2955 | mutex_unlock(&ksm_thread_mutex); | |
2956 | wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE), | |
74316201 | 2957 | TASK_UNINTERRUPTIBLE); |
ef4d43a8 HD |
2958 | mutex_lock(&ksm_thread_mutex); |
2959 | } | |
2960 | } | |
2961 | ||
21fbd591 | 2962 | static bool stable_node_dup_remove_range(struct ksm_stable_node *stable_node, |
2c653d0e AA |
2963 | unsigned long start_pfn, |
2964 | unsigned long end_pfn) | |
2965 | { | |
2966 | if (stable_node->kpfn >= start_pfn && | |
2967 | stable_node->kpfn < end_pfn) { | |
2968 | /* | |
2969 | * Don't get_ksm_page, page has already gone: | |
2970 | * which is why we keep kpfn instead of page* | |
2971 | */ | |
2972 | remove_node_from_stable_tree(stable_node); | |
2973 | return true; | |
2974 | } | |
2975 | return false; | |
2976 | } | |
2977 | ||
21fbd591 | 2978 | static bool stable_node_chain_remove_range(struct ksm_stable_node *stable_node, |
2c653d0e AA |
2979 | unsigned long start_pfn, |
2980 | unsigned long end_pfn, | |
2981 | struct rb_root *root) | |
2982 | { | |
21fbd591 | 2983 | struct ksm_stable_node *dup; |
2c653d0e AA |
2984 | struct hlist_node *hlist_safe; |
2985 | ||
2986 | if (!is_stable_node_chain(stable_node)) { | |
2987 | VM_BUG_ON(is_stable_node_dup(stable_node)); | |
2988 | return stable_node_dup_remove_range(stable_node, start_pfn, | |
2989 | end_pfn); | |
2990 | } | |
2991 | ||
2992 | hlist_for_each_entry_safe(dup, hlist_safe, | |
2993 | &stable_node->hlist, hlist_dup) { | |
2994 | VM_BUG_ON(!is_stable_node_dup(dup)); | |
2995 | stable_node_dup_remove_range(dup, start_pfn, end_pfn); | |
2996 | } | |
2997 | if (hlist_empty(&stable_node->hlist)) { | |
2998 | free_stable_node_chain(stable_node, root); | |
2999 | return true; /* notify caller that tree was rebalanced */ | |
3000 | } else | |
3001 | return false; | |
3002 | } | |
3003 | ||
ee0ea59c HD |
3004 | static void ksm_check_stable_tree(unsigned long start_pfn, |
3005 | unsigned long end_pfn) | |
62b61f61 | 3006 | { |
21fbd591 | 3007 | struct ksm_stable_node *stable_node, *next; |
62b61f61 | 3008 | struct rb_node *node; |
90bd6fd3 | 3009 | int nid; |
62b61f61 | 3010 | |
ef53d16c HD |
3011 | for (nid = 0; nid < ksm_nr_node_ids; nid++) { |
3012 | node = rb_first(root_stable_tree + nid); | |
ee0ea59c | 3013 | while (node) { |
21fbd591 | 3014 | stable_node = rb_entry(node, struct ksm_stable_node, node); |
2c653d0e AA |
3015 | if (stable_node_chain_remove_range(stable_node, |
3016 | start_pfn, end_pfn, | |
3017 | root_stable_tree + | |
3018 | nid)) | |
ef53d16c | 3019 | node = rb_first(root_stable_tree + nid); |
2c653d0e | 3020 | else |
ee0ea59c HD |
3021 | node = rb_next(node); |
3022 | cond_resched(); | |
90bd6fd3 | 3023 | } |
ee0ea59c | 3024 | } |
03640418 | 3025 | list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) { |
4146d2d6 HD |
3026 | if (stable_node->kpfn >= start_pfn && |
3027 | stable_node->kpfn < end_pfn) | |
3028 | remove_node_from_stable_tree(stable_node); | |
3029 | cond_resched(); | |
3030 | } | |
62b61f61 HD |
3031 | } |
3032 | ||
3033 | static int ksm_memory_callback(struct notifier_block *self, | |
3034 | unsigned long action, void *arg) | |
3035 | { | |
3036 | struct memory_notify *mn = arg; | |
62b61f61 HD |
3037 | |
3038 | switch (action) { | |
3039 | case MEM_GOING_OFFLINE: | |
3040 | /* | |
ef4d43a8 HD |
3041 | * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items() |
3042 | * and remove_all_stable_nodes() while memory is going offline: | |
3043 | * it is unsafe for them to touch the stable tree at this time. | |
3044 | * But unmerge_ksm_pages(), rmap lookups and other entry points | |
3045 | * which do not need the ksm_thread_mutex are all safe. | |
62b61f61 | 3046 | */ |
ef4d43a8 HD |
3047 | mutex_lock(&ksm_thread_mutex); |
3048 | ksm_run |= KSM_RUN_OFFLINE; | |
3049 | mutex_unlock(&ksm_thread_mutex); | |
62b61f61 HD |
3050 | break; |
3051 | ||
3052 | case MEM_OFFLINE: | |
3053 | /* | |
3054 | * Most of the work is done by page migration; but there might | |
3055 | * be a few stable_nodes left over, still pointing to struct | |
ee0ea59c HD |
3056 | * pages which have been offlined: prune those from the tree, |
3057 | * otherwise get_ksm_page() might later try to access a | |
3058 | * non-existent struct page. | |
62b61f61 | 3059 | */ |
ee0ea59c HD |
3060 | ksm_check_stable_tree(mn->start_pfn, |
3061 | mn->start_pfn + mn->nr_pages); | |
e4a9bc58 | 3062 | fallthrough; |
62b61f61 | 3063 | case MEM_CANCEL_OFFLINE: |
ef4d43a8 HD |
3064 | mutex_lock(&ksm_thread_mutex); |
3065 | ksm_run &= ~KSM_RUN_OFFLINE; | |
62b61f61 | 3066 | mutex_unlock(&ksm_thread_mutex); |
ef4d43a8 HD |
3067 | |
3068 | smp_mb(); /* wake_up_bit advises this */ | |
3069 | wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE)); | |
62b61f61 HD |
3070 | break; |
3071 | } | |
3072 | return NOTIFY_OK; | |
3073 | } | |
ef4d43a8 HD |
3074 | #else |
3075 | static void wait_while_offlining(void) | |
3076 | { | |
3077 | } | |
62b61f61 HD |
3078 | #endif /* CONFIG_MEMORY_HOTREMOVE */ |
3079 | ||
d21077fb SR |
3080 | #ifdef CONFIG_PROC_FS |
3081 | long ksm_process_profit(struct mm_struct *mm) | |
3082 | { | |
3083 | return mm->ksm_merging_pages * PAGE_SIZE - | |
3084 | mm->ksm_rmap_items * sizeof(struct ksm_rmap_item); | |
3085 | } | |
3086 | #endif /* CONFIG_PROC_FS */ | |
3087 | ||
2ffd8679 HD |
3088 | #ifdef CONFIG_SYSFS |
3089 | /* | |
3090 | * This all compiles without CONFIG_SYSFS, but is a waste of space. | |
3091 | */ | |
3092 | ||
31dbd01f IE |
3093 | #define KSM_ATTR_RO(_name) \ |
3094 | static struct kobj_attribute _name##_attr = __ATTR_RO(_name) | |
3095 | #define KSM_ATTR(_name) \ | |
1bad2e5c | 3096 | static struct kobj_attribute _name##_attr = __ATTR_RW(_name) |
31dbd01f IE |
3097 | |
3098 | static ssize_t sleep_millisecs_show(struct kobject *kobj, | |
3099 | struct kobj_attribute *attr, char *buf) | |
3100 | { | |
ae7a927d | 3101 | return sysfs_emit(buf, "%u\n", ksm_thread_sleep_millisecs); |
31dbd01f IE |
3102 | } |
3103 | ||
3104 | static ssize_t sleep_millisecs_store(struct kobject *kobj, | |
3105 | struct kobj_attribute *attr, | |
3106 | const char *buf, size_t count) | |
3107 | { | |
dfefd226 | 3108 | unsigned int msecs; |
31dbd01f IE |
3109 | int err; |
3110 | ||
dfefd226 AD |
3111 | err = kstrtouint(buf, 10, &msecs); |
3112 | if (err) | |
31dbd01f IE |
3113 | return -EINVAL; |
3114 | ||
3115 | ksm_thread_sleep_millisecs = msecs; | |
fcf9a0ef | 3116 | wake_up_interruptible(&ksm_iter_wait); |
31dbd01f IE |
3117 | |
3118 | return count; | |
3119 | } | |
3120 | KSM_ATTR(sleep_millisecs); | |
3121 | ||
3122 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
3123 | struct kobj_attribute *attr, char *buf) | |
3124 | { | |
ae7a927d | 3125 | return sysfs_emit(buf, "%u\n", ksm_thread_pages_to_scan); |
31dbd01f IE |
3126 | } |
3127 | ||
3128 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
3129 | struct kobj_attribute *attr, | |
3130 | const char *buf, size_t count) | |
3131 | { | |
dfefd226 | 3132 | unsigned int nr_pages; |
31dbd01f | 3133 | int err; |
31dbd01f | 3134 | |
dfefd226 AD |
3135 | err = kstrtouint(buf, 10, &nr_pages); |
3136 | if (err) | |
31dbd01f IE |
3137 | return -EINVAL; |
3138 | ||
3139 | ksm_thread_pages_to_scan = nr_pages; | |
3140 | ||
3141 | return count; | |
3142 | } | |
3143 | KSM_ATTR(pages_to_scan); | |
3144 | ||
3145 | static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr, | |
3146 | char *buf) | |
3147 | { | |
ae7a927d | 3148 | return sysfs_emit(buf, "%lu\n", ksm_run); |
31dbd01f IE |
3149 | } |
3150 | ||
3151 | static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr, | |
3152 | const char *buf, size_t count) | |
3153 | { | |
dfefd226 | 3154 | unsigned int flags; |
31dbd01f | 3155 | int err; |
31dbd01f | 3156 | |
dfefd226 AD |
3157 | err = kstrtouint(buf, 10, &flags); |
3158 | if (err) | |
31dbd01f IE |
3159 | return -EINVAL; |
3160 | if (flags > KSM_RUN_UNMERGE) | |
3161 | return -EINVAL; | |
3162 | ||
3163 | /* | |
3164 | * KSM_RUN_MERGE sets ksmd running, and 0 stops it running. | |
3165 | * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items, | |
d0f209f6 HD |
3166 | * breaking COW to free the pages_shared (but leaves mm_slots |
3167 | * on the list for when ksmd may be set running again). | |
31dbd01f IE |
3168 | */ |
3169 | ||
3170 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 3171 | wait_while_offlining(); |
31dbd01f IE |
3172 | if (ksm_run != flags) { |
3173 | ksm_run = flags; | |
d952b791 | 3174 | if (flags & KSM_RUN_UNMERGE) { |
e1e12d2f | 3175 | set_current_oom_origin(); |
d952b791 | 3176 | err = unmerge_and_remove_all_rmap_items(); |
e1e12d2f | 3177 | clear_current_oom_origin(); |
d952b791 HD |
3178 | if (err) { |
3179 | ksm_run = KSM_RUN_STOP; | |
3180 | count = err; | |
3181 | } | |
3182 | } | |
31dbd01f IE |
3183 | } |
3184 | mutex_unlock(&ksm_thread_mutex); | |
3185 | ||
3186 | if (flags & KSM_RUN_MERGE) | |
3187 | wake_up_interruptible(&ksm_thread_wait); | |
3188 | ||
3189 | return count; | |
3190 | } | |
3191 | KSM_ATTR(run); | |
3192 | ||
90bd6fd3 PH |
3193 | #ifdef CONFIG_NUMA |
3194 | static ssize_t merge_across_nodes_show(struct kobject *kobj, | |
ae7a927d | 3195 | struct kobj_attribute *attr, char *buf) |
90bd6fd3 | 3196 | { |
ae7a927d | 3197 | return sysfs_emit(buf, "%u\n", ksm_merge_across_nodes); |
90bd6fd3 PH |
3198 | } |
3199 | ||
3200 | static ssize_t merge_across_nodes_store(struct kobject *kobj, | |
3201 | struct kobj_attribute *attr, | |
3202 | const char *buf, size_t count) | |
3203 | { | |
3204 | int err; | |
3205 | unsigned long knob; | |
3206 | ||
3207 | err = kstrtoul(buf, 10, &knob); | |
3208 | if (err) | |
3209 | return err; | |
3210 | if (knob > 1) | |
3211 | return -EINVAL; | |
3212 | ||
3213 | mutex_lock(&ksm_thread_mutex); | |
ef4d43a8 | 3214 | wait_while_offlining(); |
90bd6fd3 | 3215 | if (ksm_merge_across_nodes != knob) { |
cbf86cfe | 3216 | if (ksm_pages_shared || remove_all_stable_nodes()) |
90bd6fd3 | 3217 | err = -EBUSY; |
ef53d16c HD |
3218 | else if (root_stable_tree == one_stable_tree) { |
3219 | struct rb_root *buf; | |
3220 | /* | |
3221 | * This is the first time that we switch away from the | |
3222 | * default of merging across nodes: must now allocate | |
3223 | * a buffer to hold as many roots as may be needed. | |
3224 | * Allocate stable and unstable together: | |
3225 | * MAXSMP NODES_SHIFT 10 will use 16kB. | |
3226 | */ | |
bafe1e14 JP |
3227 | buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf), |
3228 | GFP_KERNEL); | |
ef53d16c HD |
3229 | /* Let us assume that RB_ROOT is NULL is zero */ |
3230 | if (!buf) | |
3231 | err = -ENOMEM; | |
3232 | else { | |
3233 | root_stable_tree = buf; | |
3234 | root_unstable_tree = buf + nr_node_ids; | |
3235 | /* Stable tree is empty but not the unstable */ | |
3236 | root_unstable_tree[0] = one_unstable_tree[0]; | |
3237 | } | |
3238 | } | |
3239 | if (!err) { | |
90bd6fd3 | 3240 | ksm_merge_across_nodes = knob; |
ef53d16c HD |
3241 | ksm_nr_node_ids = knob ? 1 : nr_node_ids; |
3242 | } | |
90bd6fd3 PH |
3243 | } |
3244 | mutex_unlock(&ksm_thread_mutex); | |
3245 | ||
3246 | return err ? err : count; | |
3247 | } | |
3248 | KSM_ATTR(merge_across_nodes); | |
3249 | #endif | |
3250 | ||
e86c59b1 | 3251 | static ssize_t use_zero_pages_show(struct kobject *kobj, |
ae7a927d | 3252 | struct kobj_attribute *attr, char *buf) |
e86c59b1 | 3253 | { |
ae7a927d | 3254 | return sysfs_emit(buf, "%u\n", ksm_use_zero_pages); |
e86c59b1 CI |
3255 | } |
3256 | static ssize_t use_zero_pages_store(struct kobject *kobj, | |
3257 | struct kobj_attribute *attr, | |
3258 | const char *buf, size_t count) | |
3259 | { | |
3260 | int err; | |
3261 | bool value; | |
3262 | ||
3263 | err = kstrtobool(buf, &value); | |
3264 | if (err) | |
3265 | return -EINVAL; | |
3266 | ||
3267 | ksm_use_zero_pages = value; | |
3268 | ||
3269 | return count; | |
3270 | } | |
3271 | KSM_ATTR(use_zero_pages); | |
3272 | ||
2c653d0e AA |
3273 | static ssize_t max_page_sharing_show(struct kobject *kobj, |
3274 | struct kobj_attribute *attr, char *buf) | |
3275 | { | |
ae7a927d | 3276 | return sysfs_emit(buf, "%u\n", ksm_max_page_sharing); |
2c653d0e AA |
3277 | } |
3278 | ||
3279 | static ssize_t max_page_sharing_store(struct kobject *kobj, | |
3280 | struct kobj_attribute *attr, | |
3281 | const char *buf, size_t count) | |
3282 | { | |
3283 | int err; | |
3284 | int knob; | |
3285 | ||
3286 | err = kstrtoint(buf, 10, &knob); | |
3287 | if (err) | |
3288 | return err; | |
3289 | /* | |
3290 | * When a KSM page is created it is shared by 2 mappings. This | |
3291 | * being a signed comparison, it implicitly verifies it's not | |
3292 | * negative. | |
3293 | */ | |
3294 | if (knob < 2) | |
3295 | return -EINVAL; | |
3296 | ||
3297 | if (READ_ONCE(ksm_max_page_sharing) == knob) | |
3298 | return count; | |
3299 | ||
3300 | mutex_lock(&ksm_thread_mutex); | |
3301 | wait_while_offlining(); | |
3302 | if (ksm_max_page_sharing != knob) { | |
3303 | if (ksm_pages_shared || remove_all_stable_nodes()) | |
3304 | err = -EBUSY; | |
3305 | else | |
3306 | ksm_max_page_sharing = knob; | |
3307 | } | |
3308 | mutex_unlock(&ksm_thread_mutex); | |
3309 | ||
3310 | return err ? err : count; | |
3311 | } | |
3312 | KSM_ATTR(max_page_sharing); | |
3313 | ||
b4028260 HD |
3314 | static ssize_t pages_shared_show(struct kobject *kobj, |
3315 | struct kobj_attribute *attr, char *buf) | |
3316 | { | |
ae7a927d | 3317 | return sysfs_emit(buf, "%lu\n", ksm_pages_shared); |
b4028260 HD |
3318 | } |
3319 | KSM_ATTR_RO(pages_shared); | |
3320 | ||
3321 | static ssize_t pages_sharing_show(struct kobject *kobj, | |
3322 | struct kobj_attribute *attr, char *buf) | |
3323 | { | |
ae7a927d | 3324 | return sysfs_emit(buf, "%lu\n", ksm_pages_sharing); |
b4028260 HD |
3325 | } |
3326 | KSM_ATTR_RO(pages_sharing); | |
3327 | ||
473b0ce4 HD |
3328 | static ssize_t pages_unshared_show(struct kobject *kobj, |
3329 | struct kobj_attribute *attr, char *buf) | |
3330 | { | |
ae7a927d | 3331 | return sysfs_emit(buf, "%lu\n", ksm_pages_unshared); |
473b0ce4 HD |
3332 | } |
3333 | KSM_ATTR_RO(pages_unshared); | |
3334 | ||
3335 | static ssize_t pages_volatile_show(struct kobject *kobj, | |
3336 | struct kobj_attribute *attr, char *buf) | |
3337 | { | |
3338 | long ksm_pages_volatile; | |
3339 | ||
3340 | ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared | |
3341 | - ksm_pages_sharing - ksm_pages_unshared; | |
3342 | /* | |
3343 | * It was not worth any locking to calculate that statistic, | |
3344 | * but it might therefore sometimes be negative: conceal that. | |
3345 | */ | |
3346 | if (ksm_pages_volatile < 0) | |
3347 | ksm_pages_volatile = 0; | |
ae7a927d | 3348 | return sysfs_emit(buf, "%ld\n", ksm_pages_volatile); |
473b0ce4 HD |
3349 | } |
3350 | KSM_ATTR_RO(pages_volatile); | |
3351 | ||
d21077fb SR |
3352 | static ssize_t general_profit_show(struct kobject *kobj, |
3353 | struct kobj_attribute *attr, char *buf) | |
3354 | { | |
3355 | long general_profit; | |
3356 | ||
3357 | general_profit = ksm_pages_sharing * PAGE_SIZE - | |
3358 | ksm_rmap_items * sizeof(struct ksm_rmap_item); | |
3359 | ||
3360 | return sysfs_emit(buf, "%ld\n", general_profit); | |
3361 | } | |
3362 | KSM_ATTR_RO(general_profit); | |
3363 | ||
2c653d0e AA |
3364 | static ssize_t stable_node_dups_show(struct kobject *kobj, |
3365 | struct kobj_attribute *attr, char *buf) | |
3366 | { | |
ae7a927d | 3367 | return sysfs_emit(buf, "%lu\n", ksm_stable_node_dups); |
2c653d0e AA |
3368 | } |
3369 | KSM_ATTR_RO(stable_node_dups); | |
3370 | ||
3371 | static ssize_t stable_node_chains_show(struct kobject *kobj, | |
3372 | struct kobj_attribute *attr, char *buf) | |
3373 | { | |
ae7a927d | 3374 | return sysfs_emit(buf, "%lu\n", ksm_stable_node_chains); |
2c653d0e AA |
3375 | } |
3376 | KSM_ATTR_RO(stable_node_chains); | |
3377 | ||
3378 | static ssize_t | |
3379 | stable_node_chains_prune_millisecs_show(struct kobject *kobj, | |
3380 | struct kobj_attribute *attr, | |
3381 | char *buf) | |
3382 | { | |
ae7a927d | 3383 | return sysfs_emit(buf, "%u\n", ksm_stable_node_chains_prune_millisecs); |
2c653d0e AA |
3384 | } |
3385 | ||
3386 | static ssize_t | |
3387 | stable_node_chains_prune_millisecs_store(struct kobject *kobj, | |
3388 | struct kobj_attribute *attr, | |
3389 | const char *buf, size_t count) | |
3390 | { | |
584ff0df | 3391 | unsigned int msecs; |
2c653d0e AA |
3392 | int err; |
3393 | ||
584ff0df ZB |
3394 | err = kstrtouint(buf, 10, &msecs); |
3395 | if (err) | |
2c653d0e AA |
3396 | return -EINVAL; |
3397 | ||
3398 | ksm_stable_node_chains_prune_millisecs = msecs; | |
3399 | ||
3400 | return count; | |
3401 | } | |
3402 | KSM_ATTR(stable_node_chains_prune_millisecs); | |
3403 | ||
473b0ce4 HD |
3404 | static ssize_t full_scans_show(struct kobject *kobj, |
3405 | struct kobj_attribute *attr, char *buf) | |
3406 | { | |
ae7a927d | 3407 | return sysfs_emit(buf, "%lu\n", ksm_scan.seqnr); |
473b0ce4 HD |
3408 | } |
3409 | KSM_ATTR_RO(full_scans); | |
3410 | ||
31dbd01f IE |
3411 | static struct attribute *ksm_attrs[] = { |
3412 | &sleep_millisecs_attr.attr, | |
3413 | &pages_to_scan_attr.attr, | |
3414 | &run_attr.attr, | |
b4028260 HD |
3415 | &pages_shared_attr.attr, |
3416 | &pages_sharing_attr.attr, | |
473b0ce4 HD |
3417 | &pages_unshared_attr.attr, |
3418 | &pages_volatile_attr.attr, | |
3419 | &full_scans_attr.attr, | |
90bd6fd3 PH |
3420 | #ifdef CONFIG_NUMA |
3421 | &merge_across_nodes_attr.attr, | |
3422 | #endif | |
2c653d0e AA |
3423 | &max_page_sharing_attr.attr, |
3424 | &stable_node_chains_attr.attr, | |
3425 | &stable_node_dups_attr.attr, | |
3426 | &stable_node_chains_prune_millisecs_attr.attr, | |
e86c59b1 | 3427 | &use_zero_pages_attr.attr, |
d21077fb | 3428 | &general_profit_attr.attr, |
31dbd01f IE |
3429 | NULL, |
3430 | }; | |
3431 | ||
f907c26a | 3432 | static const struct attribute_group ksm_attr_group = { |
31dbd01f IE |
3433 | .attrs = ksm_attrs, |
3434 | .name = "ksm", | |
3435 | }; | |
2ffd8679 | 3436 | #endif /* CONFIG_SYSFS */ |
31dbd01f IE |
3437 | |
3438 | static int __init ksm_init(void) | |
3439 | { | |
3440 | struct task_struct *ksm_thread; | |
3441 | int err; | |
3442 | ||
e86c59b1 CI |
3443 | /* The correct value depends on page size and endianness */ |
3444 | zero_checksum = calc_checksum(ZERO_PAGE(0)); | |
3445 | /* Default to false for backwards compatibility */ | |
3446 | ksm_use_zero_pages = false; | |
3447 | ||
31dbd01f IE |
3448 | err = ksm_slab_init(); |
3449 | if (err) | |
3450 | goto out; | |
3451 | ||
31dbd01f IE |
3452 | ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd"); |
3453 | if (IS_ERR(ksm_thread)) { | |
25acde31 | 3454 | pr_err("ksm: creating kthread failed\n"); |
31dbd01f | 3455 | err = PTR_ERR(ksm_thread); |
d9f8984c | 3456 | goto out_free; |
31dbd01f IE |
3457 | } |
3458 | ||
2ffd8679 | 3459 | #ifdef CONFIG_SYSFS |
31dbd01f IE |
3460 | err = sysfs_create_group(mm_kobj, &ksm_attr_group); |
3461 | if (err) { | |
25acde31 | 3462 | pr_err("ksm: register sysfs failed\n"); |
2ffd8679 | 3463 | kthread_stop(ksm_thread); |
d9f8984c | 3464 | goto out_free; |
31dbd01f | 3465 | } |
c73602ad HD |
3466 | #else |
3467 | ksm_run = KSM_RUN_MERGE; /* no way for user to start it */ | |
3468 | ||
2ffd8679 | 3469 | #endif /* CONFIG_SYSFS */ |
31dbd01f | 3470 | |
62b61f61 | 3471 | #ifdef CONFIG_MEMORY_HOTREMOVE |
ef4d43a8 | 3472 | /* There is no significance to this priority 100 */ |
1eeaa4fd | 3473 | hotplug_memory_notifier(ksm_memory_callback, KSM_CALLBACK_PRI); |
62b61f61 | 3474 | #endif |
31dbd01f IE |
3475 | return 0; |
3476 | ||
d9f8984c | 3477 | out_free: |
31dbd01f IE |
3478 | ksm_slab_free(); |
3479 | out: | |
3480 | return err; | |
f8af4da3 | 3481 | } |
a64fb3cd | 3482 | subsys_initcall(ksm_init); |