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f8af4da3 1/*
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2 * Memory merging support.
3 *
4 * This code enables dynamic sharing of identical pages found in different
5 * memory areas, even if they are not shared by fork()
6 *
36b2528d 7 * Copyright (C) 2008-2009 Red Hat, Inc.
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8 * Authors:
9 * Izik Eidus
10 * Andrea Arcangeli
11 * Chris Wright
36b2528d 12 * Hugh Dickins
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13 *
14 * This work is licensed under the terms of the GNU GPL, version 2.
f8af4da3
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15 */
16
17#include <linux/errno.h>
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18#include <linux/mm.h>
19#include <linux/fs.h>
f8af4da3 20#include <linux/mman.h>
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21#include <linux/sched.h>
22#include <linux/rwsem.h>
23#include <linux/pagemap.h>
24#include <linux/rmap.h>
25#include <linux/spinlock.h>
26#include <linux/jhash.h>
27#include <linux/delay.h>
28#include <linux/kthread.h>
29#include <linux/wait.h>
30#include <linux/slab.h>
31#include <linux/rbtree.h>
62b61f61 32#include <linux/memory.h>
31dbd01f 33#include <linux/mmu_notifier.h>
2c6854fd 34#include <linux/swap.h>
f8af4da3 35#include <linux/ksm.h>
4ca3a69b 36#include <linux/hashtable.h>
878aee7d 37#include <linux/freezer.h>
72788c38 38#include <linux/oom.h>
90bd6fd3 39#include <linux/numa.h>
f8af4da3 40
31dbd01f 41#include <asm/tlbflush.h>
73848b46 42#include "internal.h"
31dbd01f 43
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44#ifdef CONFIG_NUMA
45#define NUMA(x) (x)
46#define DO_NUMA(x) do { (x); } while (0)
47#else
48#define NUMA(x) (0)
49#define DO_NUMA(x) do { } while (0)
50#endif
51
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52/*
53 * A few notes about the KSM scanning process,
54 * to make it easier to understand the data structures below:
55 *
56 * In order to reduce excessive scanning, KSM sorts the memory pages by their
57 * contents into a data structure that holds pointers to the pages' locations.
58 *
59 * Since the contents of the pages may change at any moment, KSM cannot just
60 * insert the pages into a normal sorted tree and expect it to find anything.
61 * Therefore KSM uses two data structures - the stable and the unstable tree.
62 *
63 * The stable tree holds pointers to all the merged pages (ksm pages), sorted
64 * by their contents. Because each such page is write-protected, searching on
65 * this tree is fully assured to be working (except when pages are unmapped),
66 * and therefore this tree is called the stable tree.
67 *
68 * In addition to the stable tree, KSM uses a second data structure called the
69 * unstable tree: this tree holds pointers to pages which have been found to
70 * be "unchanged for a period of time". The unstable tree sorts these pages
71 * by their contents, but since they are not write-protected, KSM cannot rely
72 * upon the unstable tree to work correctly - the unstable tree is liable to
73 * be corrupted as its contents are modified, and so it is called unstable.
74 *
75 * KSM solves this problem by several techniques:
76 *
77 * 1) The unstable tree is flushed every time KSM completes scanning all
78 * memory areas, and then the tree is rebuilt again from the beginning.
79 * 2) KSM will only insert into the unstable tree, pages whose hash value
80 * has not changed since the previous scan of all memory areas.
81 * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the
82 * colors of the nodes and not on their contents, assuring that even when
83 * the tree gets "corrupted" it won't get out of balance, so scanning time
84 * remains the same (also, searching and inserting nodes in an rbtree uses
85 * the same algorithm, so we have no overhead when we flush and rebuild).
86 * 4) KSM never flushes the stable tree, which means that even if it were to
87 * take 10 attempts to find a page in the unstable tree, once it is found,
88 * it is secured in the stable tree. (When we scan a new page, we first
89 * compare it against the stable tree, and then against the unstable tree.)
8fdb3dbf
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90 *
91 * If the merge_across_nodes tunable is unset, then KSM maintains multiple
92 * stable trees and multiple unstable trees: one of each for each NUMA node.
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93 */
94
95/**
96 * struct mm_slot - ksm information per mm that is being scanned
97 * @link: link to the mm_slots hash list
98 * @mm_list: link into the mm_slots list, rooted in ksm_mm_head
6514d511 99 * @rmap_list: head for this mm_slot's singly-linked list of rmap_items
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100 * @mm: the mm that this information is valid for
101 */
102struct mm_slot {
103 struct hlist_node link;
104 struct list_head mm_list;
6514d511 105 struct rmap_item *rmap_list;
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106 struct mm_struct *mm;
107};
108
109/**
110 * struct ksm_scan - cursor for scanning
111 * @mm_slot: the current mm_slot we are scanning
112 * @address: the next address inside that to be scanned
6514d511 113 * @rmap_list: link to the next rmap to be scanned in the rmap_list
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114 * @seqnr: count of completed full scans (needed when removing unstable node)
115 *
116 * There is only the one ksm_scan instance of this cursor structure.
117 */
118struct ksm_scan {
119 struct mm_slot *mm_slot;
120 unsigned long address;
6514d511 121 struct rmap_item **rmap_list;
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122 unsigned long seqnr;
123};
124
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125/**
126 * struct stable_node - node of the stable rbtree
127 * @node: rb node of this ksm page in the stable tree
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128 * @head: (overlaying parent) &migrate_nodes indicates temporarily on that list
129 * @list: linked into migrate_nodes, pending placement in the proper node tree
7b6ba2c7 130 * @hlist: hlist head of rmap_items using this ksm page
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131 * @kpfn: page frame number of this ksm page (perhaps temporarily on wrong nid)
132 * @nid: NUMA node id of stable tree in which linked (may not match kpfn)
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133 */
134struct stable_node {
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135 union {
136 struct rb_node node; /* when node of stable tree */
137 struct { /* when listed for migration */
138 struct list_head *head;
139 struct list_head list;
140 };
141 };
7b6ba2c7 142 struct hlist_head hlist;
62b61f61 143 unsigned long kpfn;
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144#ifdef CONFIG_NUMA
145 int nid;
146#endif
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HD
147};
148
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149/**
150 * struct rmap_item - reverse mapping item for virtual addresses
6514d511 151 * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list
db114b83 152 * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree
bc56620b 153 * @nid: NUMA node id of unstable tree in which linked (may not match page)
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154 * @mm: the memory structure this rmap_item is pointing into
155 * @address: the virtual address this rmap_item tracks (+ flags in low bits)
156 * @oldchecksum: previous checksum of the page at that virtual address
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157 * @node: rb node of this rmap_item in the unstable tree
158 * @head: pointer to stable_node heading this list in the stable tree
159 * @hlist: link into hlist of rmap_items hanging off that stable_node
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160 */
161struct rmap_item {
6514d511 162 struct rmap_item *rmap_list;
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163 union {
164 struct anon_vma *anon_vma; /* when stable */
165#ifdef CONFIG_NUMA
166 int nid; /* when node of unstable tree */
167#endif
168 };
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169 struct mm_struct *mm;
170 unsigned long address; /* + low bits used for flags below */
7b6ba2c7 171 unsigned int oldchecksum; /* when unstable */
31dbd01f 172 union {
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173 struct rb_node node; /* when node of unstable tree */
174 struct { /* when listed from stable tree */
175 struct stable_node *head;
176 struct hlist_node hlist;
177 };
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178 };
179};
180
181#define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */
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182#define UNSTABLE_FLAG 0x100 /* is a node of the unstable tree */
183#define STABLE_FLAG 0x200 /* is listed from the stable tree */
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184
185/* The stable and unstable tree heads */
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186static struct rb_root one_stable_tree[1] = { RB_ROOT };
187static struct rb_root one_unstable_tree[1] = { RB_ROOT };
188static struct rb_root *root_stable_tree = one_stable_tree;
189static struct rb_root *root_unstable_tree = one_unstable_tree;
31dbd01f 190
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191/* Recently migrated nodes of stable tree, pending proper placement */
192static LIST_HEAD(migrate_nodes);
193
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194#define MM_SLOTS_HASH_BITS 10
195static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
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196
197static struct mm_slot ksm_mm_head = {
198 .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list),
199};
200static struct ksm_scan ksm_scan = {
201 .mm_slot = &ksm_mm_head,
202};
203
204static struct kmem_cache *rmap_item_cache;
7b6ba2c7 205static struct kmem_cache *stable_node_cache;
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206static struct kmem_cache *mm_slot_cache;
207
208/* The number of nodes in the stable tree */
b4028260 209static unsigned long ksm_pages_shared;
31dbd01f 210
e178dfde 211/* The number of page slots additionally sharing those nodes */
b4028260 212static unsigned long ksm_pages_sharing;
31dbd01f 213
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214/* The number of nodes in the unstable tree */
215static unsigned long ksm_pages_unshared;
216
217/* The number of rmap_items in use: to calculate pages_volatile */
218static unsigned long ksm_rmap_items;
219
31dbd01f 220/* Number of pages ksmd should scan in one batch */
2c6854fd 221static unsigned int ksm_thread_pages_to_scan = 100;
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222
223/* Milliseconds ksmd should sleep between batches */
2ffd8679 224static unsigned int ksm_thread_sleep_millisecs = 20;
31dbd01f 225
e850dcf5 226#ifdef CONFIG_NUMA
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227/* Zeroed when merging across nodes is not allowed */
228static unsigned int ksm_merge_across_nodes = 1;
ef53d16c 229static int ksm_nr_node_ids = 1;
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230#else
231#define ksm_merge_across_nodes 1U
ef53d16c 232#define ksm_nr_node_ids 1
e850dcf5 233#endif
90bd6fd3 234
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235#define KSM_RUN_STOP 0
236#define KSM_RUN_MERGE 1
237#define KSM_RUN_UNMERGE 2
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HD
238#define KSM_RUN_OFFLINE 4
239static unsigned long ksm_run = KSM_RUN_STOP;
240static void wait_while_offlining(void);
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241
242static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait);
243static DEFINE_MUTEX(ksm_thread_mutex);
244static DEFINE_SPINLOCK(ksm_mmlist_lock);
245
246#define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\
247 sizeof(struct __struct), __alignof__(struct __struct),\
248 (__flags), NULL)
249
250static int __init ksm_slab_init(void)
251{
252 rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0);
253 if (!rmap_item_cache)
254 goto out;
255
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HD
256 stable_node_cache = KSM_KMEM_CACHE(stable_node, 0);
257 if (!stable_node_cache)
258 goto out_free1;
259
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260 mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0);
261 if (!mm_slot_cache)
7b6ba2c7 262 goto out_free2;
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263
264 return 0;
265
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HD
266out_free2:
267 kmem_cache_destroy(stable_node_cache);
268out_free1:
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269 kmem_cache_destroy(rmap_item_cache);
270out:
271 return -ENOMEM;
272}
273
274static void __init ksm_slab_free(void)
275{
276 kmem_cache_destroy(mm_slot_cache);
7b6ba2c7 277 kmem_cache_destroy(stable_node_cache);
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278 kmem_cache_destroy(rmap_item_cache);
279 mm_slot_cache = NULL;
280}
281
282static inline struct rmap_item *alloc_rmap_item(void)
283{
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HD
284 struct rmap_item *rmap_item;
285
286 rmap_item = kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL);
287 if (rmap_item)
288 ksm_rmap_items++;
289 return rmap_item;
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290}
291
292static inline void free_rmap_item(struct rmap_item *rmap_item)
293{
473b0ce4 294 ksm_rmap_items--;
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295 rmap_item->mm = NULL; /* debug safety */
296 kmem_cache_free(rmap_item_cache, rmap_item);
297}
298
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299static inline struct stable_node *alloc_stable_node(void)
300{
301 return kmem_cache_alloc(stable_node_cache, GFP_KERNEL);
302}
303
304static inline void free_stable_node(struct stable_node *stable_node)
305{
306 kmem_cache_free(stable_node_cache, stable_node);
307}
308
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309static inline struct mm_slot *alloc_mm_slot(void)
310{
311 if (!mm_slot_cache) /* initialization failed */
312 return NULL;
313 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
314}
315
316static inline void free_mm_slot(struct mm_slot *mm_slot)
317{
318 kmem_cache_free(mm_slot_cache, mm_slot);
319}
320
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321static struct mm_slot *get_mm_slot(struct mm_struct *mm)
322{
4ca3a69b
SL
323 struct mm_slot *slot;
324
b67bfe0d 325 hash_for_each_possible(mm_slots_hash, slot, link, (unsigned long)mm)
4ca3a69b
SL
326 if (slot->mm == mm)
327 return slot;
31dbd01f 328
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329 return NULL;
330}
331
332static void insert_to_mm_slots_hash(struct mm_struct *mm,
333 struct mm_slot *mm_slot)
334{
31dbd01f 335 mm_slot->mm = mm;
4ca3a69b 336 hash_add(mm_slots_hash, &mm_slot->link, (unsigned long)mm);
31dbd01f
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337}
338
a913e182
HD
339/*
340 * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's
341 * page tables after it has passed through ksm_exit() - which, if necessary,
342 * takes mmap_sem briefly to serialize against them. ksm_exit() does not set
343 * a special flag: they can just back out as soon as mm_users goes to zero.
344 * ksm_test_exit() is used throughout to make this test for exit: in some
345 * places for correctness, in some places just to avoid unnecessary work.
346 */
347static inline bool ksm_test_exit(struct mm_struct *mm)
348{
349 return atomic_read(&mm->mm_users) == 0;
350}
351
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352/*
353 * We use break_ksm to break COW on a ksm page: it's a stripped down
354 *
355 * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1)
356 * put_page(page);
357 *
358 * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma,
359 * in case the application has unmapped and remapped mm,addr meanwhile.
360 * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP
361 * mmap of /dev/mem or /dev/kmem, where we would not want to touch it.
362 */
d952b791 363static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
31dbd01f
IE
364{
365 struct page *page;
d952b791 366 int ret = 0;
31dbd01f
IE
367
368 do {
369 cond_resched();
5117b3b8 370 page = follow_page(vma, addr, FOLL_GET | FOLL_MIGRATION);
22eccdd7 371 if (IS_ERR_OR_NULL(page))
31dbd01f
IE
372 break;
373 if (PageKsm(page))
374 ret = handle_mm_fault(vma->vm_mm, vma, addr,
375 FAULT_FLAG_WRITE);
376 else
377 ret = VM_FAULT_WRITE;
378 put_page(page);
33692f27 379 } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM)));
d952b791
HD
380 /*
381 * We must loop because handle_mm_fault() may back out if there's
382 * any difficulty e.g. if pte accessed bit gets updated concurrently.
383 *
384 * VM_FAULT_WRITE is what we have been hoping for: it indicates that
385 * COW has been broken, even if the vma does not permit VM_WRITE;
386 * but note that a concurrent fault might break PageKsm for us.
387 *
388 * VM_FAULT_SIGBUS could occur if we race with truncation of the
389 * backing file, which also invalidates anonymous pages: that's
390 * okay, that truncation will have unmapped the PageKsm for us.
391 *
392 * VM_FAULT_OOM: at the time of writing (late July 2009), setting
393 * aside mem_cgroup limits, VM_FAULT_OOM would only be set if the
394 * current task has TIF_MEMDIE set, and will be OOM killed on return
395 * to user; and ksmd, having no mm, would never be chosen for that.
396 *
397 * But if the mm is in a limited mem_cgroup, then the fault may fail
398 * with VM_FAULT_OOM even if the current task is not TIF_MEMDIE; and
399 * even ksmd can fail in this way - though it's usually breaking ksm
400 * just to undo a merge it made a moment before, so unlikely to oom.
401 *
402 * That's a pity: we might therefore have more kernel pages allocated
403 * than we're counting as nodes in the stable tree; but ksm_do_scan
404 * will retry to break_cow on each pass, so should recover the page
405 * in due course. The important thing is to not let VM_MERGEABLE
406 * be cleared while any such pages might remain in the area.
407 */
408 return (ret & VM_FAULT_OOM) ? -ENOMEM : 0;
31dbd01f
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409}
410
ef694222
BL
411static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm,
412 unsigned long addr)
413{
414 struct vm_area_struct *vma;
415 if (ksm_test_exit(mm))
416 return NULL;
417 vma = find_vma(mm, addr);
418 if (!vma || vma->vm_start > addr)
419 return NULL;
420 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
421 return NULL;
422 return vma;
423}
424
8dd3557a 425static void break_cow(struct rmap_item *rmap_item)
31dbd01f 426{
8dd3557a
HD
427 struct mm_struct *mm = rmap_item->mm;
428 unsigned long addr = rmap_item->address;
31dbd01f
IE
429 struct vm_area_struct *vma;
430
4035c07a
HD
431 /*
432 * It is not an accident that whenever we want to break COW
433 * to undo, we also need to drop a reference to the anon_vma.
434 */
9e60109f 435 put_anon_vma(rmap_item->anon_vma);
4035c07a 436
81464e30 437 down_read(&mm->mmap_sem);
ef694222
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438 vma = find_mergeable_vma(mm, addr);
439 if (vma)
440 break_ksm(vma, addr);
31dbd01f
IE
441 up_read(&mm->mmap_sem);
442}
443
29ad768c
AA
444static struct page *page_trans_compound_anon(struct page *page)
445{
446 if (PageTransCompound(page)) {
668f9abb 447 struct page *head = compound_head(page);
29ad768c 448 /*
22e5c47e
AA
449 * head may actually be splitted and freed from under
450 * us but it's ok here.
29ad768c 451 */
29ad768c
AA
452 if (PageAnon(head))
453 return head;
454 }
455 return NULL;
456}
457
31dbd01f
IE
458static struct page *get_mergeable_page(struct rmap_item *rmap_item)
459{
460 struct mm_struct *mm = rmap_item->mm;
461 unsigned long addr = rmap_item->address;
462 struct vm_area_struct *vma;
463 struct page *page;
464
465 down_read(&mm->mmap_sem);
ef694222
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466 vma = find_mergeable_vma(mm, addr);
467 if (!vma)
31dbd01f
IE
468 goto out;
469
470 page = follow_page(vma, addr, FOLL_GET);
22eccdd7 471 if (IS_ERR_OR_NULL(page))
31dbd01f 472 goto out;
29ad768c 473 if (PageAnon(page) || page_trans_compound_anon(page)) {
31dbd01f
IE
474 flush_anon_page(vma, page, addr);
475 flush_dcache_page(page);
476 } else {
477 put_page(page);
c8f95ed1
AA
478out:
479 page = NULL;
31dbd01f
IE
480 }
481 up_read(&mm->mmap_sem);
482 return page;
483}
484
90bd6fd3
PH
485/*
486 * This helper is used for getting right index into array of tree roots.
487 * When merge_across_nodes knob is set to 1, there are only two rb-trees for
488 * stable and unstable pages from all nodes with roots in index 0. Otherwise,
489 * every node has its own stable and unstable tree.
490 */
491static inline int get_kpfn_nid(unsigned long kpfn)
492{
d8fc16a8 493 return ksm_merge_across_nodes ? 0 : NUMA(pfn_to_nid(kpfn));
90bd6fd3
PH
494}
495
4035c07a
HD
496static void remove_node_from_stable_tree(struct stable_node *stable_node)
497{
498 struct rmap_item *rmap_item;
4035c07a 499
b67bfe0d 500 hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
4035c07a
HD
501 if (rmap_item->hlist.next)
502 ksm_pages_sharing--;
503 else
504 ksm_pages_shared--;
9e60109f 505 put_anon_vma(rmap_item->anon_vma);
4035c07a
HD
506 rmap_item->address &= PAGE_MASK;
507 cond_resched();
508 }
509
4146d2d6
HD
510 if (stable_node->head == &migrate_nodes)
511 list_del(&stable_node->list);
512 else
513 rb_erase(&stable_node->node,
ef53d16c 514 root_stable_tree + NUMA(stable_node->nid));
4035c07a
HD
515 free_stable_node(stable_node);
516}
517
518/*
519 * get_ksm_page: checks if the page indicated by the stable node
520 * is still its ksm page, despite having held no reference to it.
521 * In which case we can trust the content of the page, and it
522 * returns the gotten page; but if the page has now been zapped,
523 * remove the stale node from the stable tree and return NULL.
c8d6553b 524 * But beware, the stable node's page might be being migrated.
4035c07a
HD
525 *
526 * You would expect the stable_node to hold a reference to the ksm page.
527 * But if it increments the page's count, swapping out has to wait for
528 * ksmd to come around again before it can free the page, which may take
529 * seconds or even minutes: much too unresponsive. So instead we use a
530 * "keyhole reference": access to the ksm page from the stable node peeps
531 * out through its keyhole to see if that page still holds the right key,
532 * pointing back to this stable node. This relies on freeing a PageAnon
533 * page to reset its page->mapping to NULL, and relies on no other use of
534 * a page to put something that might look like our key in page->mapping.
4035c07a
HD
535 * is on its way to being freed; but it is an anomaly to bear in mind.
536 */
8fdb3dbf 537static struct page *get_ksm_page(struct stable_node *stable_node, bool lock_it)
4035c07a
HD
538{
539 struct page *page;
540 void *expected_mapping;
c8d6553b 541 unsigned long kpfn;
4035c07a 542
4035c07a
HD
543 expected_mapping = (void *)stable_node +
544 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
c8d6553b 545again:
4db0c3c2 546 kpfn = READ_ONCE(stable_node->kpfn);
c8d6553b
HD
547 page = pfn_to_page(kpfn);
548
549 /*
550 * page is computed from kpfn, so on most architectures reading
551 * page->mapping is naturally ordered after reading node->kpfn,
552 * but on Alpha we need to be more careful.
553 */
554 smp_read_barrier_depends();
4db0c3c2 555 if (READ_ONCE(page->mapping) != expected_mapping)
4035c07a 556 goto stale;
c8d6553b
HD
557
558 /*
559 * We cannot do anything with the page while its refcount is 0.
560 * Usually 0 means free, or tail of a higher-order page: in which
561 * case this node is no longer referenced, and should be freed;
562 * however, it might mean that the page is under page_freeze_refs().
563 * The __remove_mapping() case is easy, again the node is now stale;
564 * but if page is swapcache in migrate_page_move_mapping(), it might
565 * still be our page, in which case it's essential to keep the node.
566 */
567 while (!get_page_unless_zero(page)) {
568 /*
569 * Another check for page->mapping != expected_mapping would
570 * work here too. We have chosen the !PageSwapCache test to
571 * optimize the common case, when the page is or is about to
572 * be freed: PageSwapCache is cleared (under spin_lock_irq)
573 * in the freeze_refs section of __remove_mapping(); but Anon
574 * page->mapping reset to NULL later, in free_pages_prepare().
575 */
576 if (!PageSwapCache(page))
577 goto stale;
578 cpu_relax();
579 }
580
4db0c3c2 581 if (READ_ONCE(page->mapping) != expected_mapping) {
4035c07a
HD
582 put_page(page);
583 goto stale;
584 }
c8d6553b 585
8fdb3dbf 586 if (lock_it) {
8aafa6a4 587 lock_page(page);
4db0c3c2 588 if (READ_ONCE(page->mapping) != expected_mapping) {
8aafa6a4
HD
589 unlock_page(page);
590 put_page(page);
591 goto stale;
592 }
593 }
4035c07a 594 return page;
c8d6553b 595
4035c07a 596stale:
c8d6553b
HD
597 /*
598 * We come here from above when page->mapping or !PageSwapCache
599 * suggests that the node is stale; but it might be under migration.
600 * We need smp_rmb(), matching the smp_wmb() in ksm_migrate_page(),
601 * before checking whether node->kpfn has been changed.
602 */
603 smp_rmb();
4db0c3c2 604 if (READ_ONCE(stable_node->kpfn) != kpfn)
c8d6553b 605 goto again;
4035c07a
HD
606 remove_node_from_stable_tree(stable_node);
607 return NULL;
608}
609
31dbd01f
IE
610/*
611 * Removing rmap_item from stable or unstable tree.
612 * This function will clean the information from the stable/unstable tree.
613 */
614static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
615{
7b6ba2c7
HD
616 if (rmap_item->address & STABLE_FLAG) {
617 struct stable_node *stable_node;
5ad64688 618 struct page *page;
31dbd01f 619
7b6ba2c7 620 stable_node = rmap_item->head;
8aafa6a4 621 page = get_ksm_page(stable_node, true);
4035c07a
HD
622 if (!page)
623 goto out;
5ad64688 624
7b6ba2c7 625 hlist_del(&rmap_item->hlist);
4035c07a
HD
626 unlock_page(page);
627 put_page(page);
08beca44 628
98666f8a 629 if (!hlist_empty(&stable_node->hlist))
4035c07a
HD
630 ksm_pages_sharing--;
631 else
7b6ba2c7 632 ksm_pages_shared--;
31dbd01f 633
9e60109f 634 put_anon_vma(rmap_item->anon_vma);
93d17715 635 rmap_item->address &= PAGE_MASK;
31dbd01f 636
7b6ba2c7 637 } else if (rmap_item->address & UNSTABLE_FLAG) {
31dbd01f
IE
638 unsigned char age;
639 /*
9ba69294 640 * Usually ksmd can and must skip the rb_erase, because
31dbd01f 641 * root_unstable_tree was already reset to RB_ROOT.
9ba69294
HD
642 * But be careful when an mm is exiting: do the rb_erase
643 * if this rmap_item was inserted by this scan, rather
644 * than left over from before.
31dbd01f
IE
645 */
646 age = (unsigned char)(ksm_scan.seqnr - rmap_item->address);
cd551f97 647 BUG_ON(age > 1);
31dbd01f 648 if (!age)
90bd6fd3 649 rb_erase(&rmap_item->node,
ef53d16c 650 root_unstable_tree + NUMA(rmap_item->nid));
473b0ce4 651 ksm_pages_unshared--;
93d17715 652 rmap_item->address &= PAGE_MASK;
31dbd01f 653 }
4035c07a 654out:
31dbd01f
IE
655 cond_resched(); /* we're called from many long loops */
656}
657
31dbd01f 658static void remove_trailing_rmap_items(struct mm_slot *mm_slot,
6514d511 659 struct rmap_item **rmap_list)
31dbd01f 660{
6514d511
HD
661 while (*rmap_list) {
662 struct rmap_item *rmap_item = *rmap_list;
663 *rmap_list = rmap_item->rmap_list;
31dbd01f 664 remove_rmap_item_from_tree(rmap_item);
31dbd01f
IE
665 free_rmap_item(rmap_item);
666 }
667}
668
669/*
e850dcf5 670 * Though it's very tempting to unmerge rmap_items from stable tree rather
31dbd01f
IE
671 * than check every pte of a given vma, the locking doesn't quite work for
672 * that - an rmap_item is assigned to the stable tree after inserting ksm
673 * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing
674 * rmap_items from parent to child at fork time (so as not to waste time
675 * if exit comes before the next scan reaches it).
81464e30
HD
676 *
677 * Similarly, although we'd like to remove rmap_items (so updating counts
678 * and freeing memory) when unmerging an area, it's easier to leave that
679 * to the next pass of ksmd - consider, for example, how ksmd might be
680 * in cmp_and_merge_page on one of the rmap_items we would be removing.
31dbd01f 681 */
d952b791
HD
682static int unmerge_ksm_pages(struct vm_area_struct *vma,
683 unsigned long start, unsigned long end)
31dbd01f
IE
684{
685 unsigned long addr;
d952b791 686 int err = 0;
31dbd01f 687
d952b791 688 for (addr = start; addr < end && !err; addr += PAGE_SIZE) {
9ba69294
HD
689 if (ksm_test_exit(vma->vm_mm))
690 break;
d952b791
HD
691 if (signal_pending(current))
692 err = -ERESTARTSYS;
693 else
694 err = break_ksm(vma, addr);
695 }
696 return err;
31dbd01f
IE
697}
698
2ffd8679
HD
699#ifdef CONFIG_SYSFS
700/*
701 * Only called through the sysfs control interface:
702 */
cbf86cfe
HD
703static int remove_stable_node(struct stable_node *stable_node)
704{
705 struct page *page;
706 int err;
707
708 page = get_ksm_page(stable_node, true);
709 if (!page) {
710 /*
711 * get_ksm_page did remove_node_from_stable_tree itself.
712 */
713 return 0;
714 }
715
8fdb3dbf
HD
716 if (WARN_ON_ONCE(page_mapped(page))) {
717 /*
718 * This should not happen: but if it does, just refuse to let
719 * merge_across_nodes be switched - there is no need to panic.
720 */
cbf86cfe 721 err = -EBUSY;
8fdb3dbf 722 } else {
cbf86cfe 723 /*
8fdb3dbf
HD
724 * The stable node did not yet appear stale to get_ksm_page(),
725 * since that allows for an unmapped ksm page to be recognized
726 * right up until it is freed; but the node is safe to remove.
cbf86cfe
HD
727 * This page might be in a pagevec waiting to be freed,
728 * or it might be PageSwapCache (perhaps under writeback),
729 * or it might have been removed from swapcache a moment ago.
730 */
731 set_page_stable_node(page, NULL);
732 remove_node_from_stable_tree(stable_node);
733 err = 0;
734 }
735
736 unlock_page(page);
737 put_page(page);
738 return err;
739}
740
741static int remove_all_stable_nodes(void)
742{
743 struct stable_node *stable_node;
4146d2d6 744 struct list_head *this, *next;
cbf86cfe
HD
745 int nid;
746 int err = 0;
747
ef53d16c 748 for (nid = 0; nid < ksm_nr_node_ids; nid++) {
cbf86cfe
HD
749 while (root_stable_tree[nid].rb_node) {
750 stable_node = rb_entry(root_stable_tree[nid].rb_node,
751 struct stable_node, node);
752 if (remove_stable_node(stable_node)) {
753 err = -EBUSY;
754 break; /* proceed to next nid */
755 }
756 cond_resched();
757 }
758 }
4146d2d6
HD
759 list_for_each_safe(this, next, &migrate_nodes) {
760 stable_node = list_entry(this, struct stable_node, list);
761 if (remove_stable_node(stable_node))
762 err = -EBUSY;
763 cond_resched();
764 }
cbf86cfe
HD
765 return err;
766}
767
d952b791 768static int unmerge_and_remove_all_rmap_items(void)
31dbd01f
IE
769{
770 struct mm_slot *mm_slot;
771 struct mm_struct *mm;
772 struct vm_area_struct *vma;
d952b791
HD
773 int err = 0;
774
775 spin_lock(&ksm_mmlist_lock);
9ba69294 776 ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_list.next,
d952b791
HD
777 struct mm_slot, mm_list);
778 spin_unlock(&ksm_mmlist_lock);
31dbd01f 779
9ba69294
HD
780 for (mm_slot = ksm_scan.mm_slot;
781 mm_slot != &ksm_mm_head; mm_slot = ksm_scan.mm_slot) {
31dbd01f
IE
782 mm = mm_slot->mm;
783 down_read(&mm->mmap_sem);
784 for (vma = mm->mmap; vma; vma = vma->vm_next) {
9ba69294
HD
785 if (ksm_test_exit(mm))
786 break;
31dbd01f
IE
787 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
788 continue;
d952b791
HD
789 err = unmerge_ksm_pages(vma,
790 vma->vm_start, vma->vm_end);
9ba69294
HD
791 if (err)
792 goto error;
31dbd01f 793 }
9ba69294 794
6514d511 795 remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list);
d952b791
HD
796
797 spin_lock(&ksm_mmlist_lock);
9ba69294 798 ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next,
d952b791 799 struct mm_slot, mm_list);
9ba69294 800 if (ksm_test_exit(mm)) {
4ca3a69b 801 hash_del(&mm_slot->link);
9ba69294
HD
802 list_del(&mm_slot->mm_list);
803 spin_unlock(&ksm_mmlist_lock);
804
805 free_mm_slot(mm_slot);
806 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
807 up_read(&mm->mmap_sem);
808 mmdrop(mm);
809 } else {
810 spin_unlock(&ksm_mmlist_lock);
811 up_read(&mm->mmap_sem);
812 }
31dbd01f
IE
813 }
814
cbf86cfe
HD
815 /* Clean up stable nodes, but don't worry if some are still busy */
816 remove_all_stable_nodes();
d952b791 817 ksm_scan.seqnr = 0;
9ba69294
HD
818 return 0;
819
820error:
821 up_read(&mm->mmap_sem);
31dbd01f 822 spin_lock(&ksm_mmlist_lock);
d952b791 823 ksm_scan.mm_slot = &ksm_mm_head;
31dbd01f 824 spin_unlock(&ksm_mmlist_lock);
d952b791 825 return err;
31dbd01f 826}
2ffd8679 827#endif /* CONFIG_SYSFS */
31dbd01f 828
31dbd01f
IE
829static u32 calc_checksum(struct page *page)
830{
831 u32 checksum;
9b04c5fe 832 void *addr = kmap_atomic(page);
31dbd01f 833 checksum = jhash2(addr, PAGE_SIZE / 4, 17);
9b04c5fe 834 kunmap_atomic(addr);
31dbd01f
IE
835 return checksum;
836}
837
838static int memcmp_pages(struct page *page1, struct page *page2)
839{
840 char *addr1, *addr2;
841 int ret;
842
9b04c5fe
CW
843 addr1 = kmap_atomic(page1);
844 addr2 = kmap_atomic(page2);
31dbd01f 845 ret = memcmp(addr1, addr2, PAGE_SIZE);
9b04c5fe
CW
846 kunmap_atomic(addr2);
847 kunmap_atomic(addr1);
31dbd01f
IE
848 return ret;
849}
850
851static inline int pages_identical(struct page *page1, struct page *page2)
852{
853 return !memcmp_pages(page1, page2);
854}
855
856static int write_protect_page(struct vm_area_struct *vma, struct page *page,
857 pte_t *orig_pte)
858{
859 struct mm_struct *mm = vma->vm_mm;
860 unsigned long addr;
861 pte_t *ptep;
862 spinlock_t *ptl;
863 int swapped;
864 int err = -EFAULT;
6bdb913f
HE
865 unsigned long mmun_start; /* For mmu_notifiers */
866 unsigned long mmun_end; /* For mmu_notifiers */
31dbd01f
IE
867
868 addr = page_address_in_vma(page, vma);
869 if (addr == -EFAULT)
870 goto out;
871
29ad768c 872 BUG_ON(PageTransCompound(page));
6bdb913f
HE
873
874 mmun_start = addr;
875 mmun_end = addr + PAGE_SIZE;
876 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
877
31dbd01f
IE
878 ptep = page_check_address(page, mm, addr, &ptl, 0);
879 if (!ptep)
6bdb913f 880 goto out_mn;
31dbd01f 881
4e31635c 882 if (pte_write(*ptep) || pte_dirty(*ptep)) {
31dbd01f
IE
883 pte_t entry;
884
885 swapped = PageSwapCache(page);
886 flush_cache_page(vma, addr, page_to_pfn(page));
887 /*
25985edc 888 * Ok this is tricky, when get_user_pages_fast() run it doesn't
31dbd01f
IE
889 * take any lock, therefore the check that we are going to make
890 * with the pagecount against the mapcount is racey and
891 * O_DIRECT can happen right after the check.
892 * So we clear the pte and flush the tlb before the check
893 * this assure us that no O_DIRECT can happen after the check
894 * or in the middle of the check.
895 */
34ee645e 896 entry = ptep_clear_flush_notify(vma, addr, ptep);
31dbd01f
IE
897 /*
898 * Check that no O_DIRECT or similar I/O is in progress on the
899 * page
900 */
31e855ea 901 if (page_mapcount(page) + 1 + swapped != page_count(page)) {
cb532375 902 set_pte_at(mm, addr, ptep, entry);
31dbd01f
IE
903 goto out_unlock;
904 }
4e31635c
HD
905 if (pte_dirty(entry))
906 set_page_dirty(page);
907 entry = pte_mkclean(pte_wrprotect(entry));
31dbd01f
IE
908 set_pte_at_notify(mm, addr, ptep, entry);
909 }
910 *orig_pte = *ptep;
911 err = 0;
912
913out_unlock:
914 pte_unmap_unlock(ptep, ptl);
6bdb913f
HE
915out_mn:
916 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
31dbd01f
IE
917out:
918 return err;
919}
920
921/**
922 * replace_page - replace page in vma by new ksm page
8dd3557a
HD
923 * @vma: vma that holds the pte pointing to page
924 * @page: the page we are replacing by kpage
925 * @kpage: the ksm page we replace page by
31dbd01f
IE
926 * @orig_pte: the original value of the pte
927 *
928 * Returns 0 on success, -EFAULT on failure.
929 */
8dd3557a
HD
930static int replace_page(struct vm_area_struct *vma, struct page *page,
931 struct page *kpage, pte_t orig_pte)
31dbd01f
IE
932{
933 struct mm_struct *mm = vma->vm_mm;
31dbd01f
IE
934 pmd_t *pmd;
935 pte_t *ptep;
936 spinlock_t *ptl;
937 unsigned long addr;
31dbd01f 938 int err = -EFAULT;
6bdb913f
HE
939 unsigned long mmun_start; /* For mmu_notifiers */
940 unsigned long mmun_end; /* For mmu_notifiers */
31dbd01f 941
8dd3557a 942 addr = page_address_in_vma(page, vma);
31dbd01f
IE
943 if (addr == -EFAULT)
944 goto out;
945
6219049a
BL
946 pmd = mm_find_pmd(mm, addr);
947 if (!pmd)
31dbd01f 948 goto out;
31dbd01f 949
6bdb913f
HE
950 mmun_start = addr;
951 mmun_end = addr + PAGE_SIZE;
952 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
953
31dbd01f
IE
954 ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
955 if (!pte_same(*ptep, orig_pte)) {
956 pte_unmap_unlock(ptep, ptl);
6bdb913f 957 goto out_mn;
31dbd01f
IE
958 }
959
8dd3557a 960 get_page(kpage);
5ad64688 961 page_add_anon_rmap(kpage, vma, addr);
31dbd01f
IE
962
963 flush_cache_page(vma, addr, pte_pfn(*ptep));
34ee645e 964 ptep_clear_flush_notify(vma, addr, ptep);
8dd3557a 965 set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
31dbd01f 966
8dd3557a 967 page_remove_rmap(page);
ae52a2ad
HD
968 if (!page_mapped(page))
969 try_to_free_swap(page);
8dd3557a 970 put_page(page);
31dbd01f
IE
971
972 pte_unmap_unlock(ptep, ptl);
973 err = 0;
6bdb913f
HE
974out_mn:
975 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
31dbd01f
IE
976out:
977 return err;
978}
979
29ad768c
AA
980static int page_trans_compound_anon_split(struct page *page)
981{
982 int ret = 0;
983 struct page *transhuge_head = page_trans_compound_anon(page);
984 if (transhuge_head) {
985 /* Get the reference on the head to split it. */
986 if (get_page_unless_zero(transhuge_head)) {
987 /*
988 * Recheck we got the reference while the head
989 * was still anonymous.
990 */
991 if (PageAnon(transhuge_head))
992 ret = split_huge_page(transhuge_head);
993 else
994 /*
995 * Retry later if split_huge_page run
996 * from under us.
997 */
998 ret = 1;
999 put_page(transhuge_head);
1000 } else
1001 /* Retry later if split_huge_page run from under us. */
1002 ret = 1;
1003 }
1004 return ret;
1005}
1006
31dbd01f
IE
1007/*
1008 * try_to_merge_one_page - take two pages and merge them into one
8dd3557a
HD
1009 * @vma: the vma that holds the pte pointing to page
1010 * @page: the PageAnon page that we want to replace with kpage
80e14822
HD
1011 * @kpage: the PageKsm page that we want to map instead of page,
1012 * or NULL the first time when we want to use page as kpage.
31dbd01f
IE
1013 *
1014 * This function returns 0 if the pages were merged, -EFAULT otherwise.
1015 */
1016static int try_to_merge_one_page(struct vm_area_struct *vma,
8dd3557a 1017 struct page *page, struct page *kpage)
31dbd01f
IE
1018{
1019 pte_t orig_pte = __pte(0);
1020 int err = -EFAULT;
1021
db114b83
HD
1022 if (page == kpage) /* ksm page forked */
1023 return 0;
1024
29ad768c
AA
1025 if (PageTransCompound(page) && page_trans_compound_anon_split(page))
1026 goto out;
1027 BUG_ON(PageTransCompound(page));
8dd3557a 1028 if (!PageAnon(page))
31dbd01f
IE
1029 goto out;
1030
31dbd01f
IE
1031 /*
1032 * We need the page lock to read a stable PageSwapCache in
1033 * write_protect_page(). We use trylock_page() instead of
1034 * lock_page() because we don't want to wait here - we
1035 * prefer to continue scanning and merging different pages,
1036 * then come back to this page when it is unlocked.
1037 */
8dd3557a 1038 if (!trylock_page(page))
31e855ea 1039 goto out;
31dbd01f
IE
1040 /*
1041 * If this anonymous page is mapped only here, its pte may need
1042 * to be write-protected. If it's mapped elsewhere, all of its
1043 * ptes are necessarily already write-protected. But in either
1044 * case, we need to lock and check page_count is not raised.
1045 */
80e14822
HD
1046 if (write_protect_page(vma, page, &orig_pte) == 0) {
1047 if (!kpage) {
1048 /*
1049 * While we hold page lock, upgrade page from
1050 * PageAnon+anon_vma to PageKsm+NULL stable_node:
1051 * stable_tree_insert() will update stable_node.
1052 */
1053 set_page_stable_node(page, NULL);
1054 mark_page_accessed(page);
1055 err = 0;
1056 } else if (pages_identical(page, kpage))
1057 err = replace_page(vma, page, kpage, orig_pte);
1058 }
31dbd01f 1059
80e14822 1060 if ((vma->vm_flags & VM_LOCKED) && kpage && !err) {
73848b46 1061 munlock_vma_page(page);
5ad64688
HD
1062 if (!PageMlocked(kpage)) {
1063 unlock_page(page);
5ad64688
HD
1064 lock_page(kpage);
1065 mlock_vma_page(kpage);
1066 page = kpage; /* for final unlock */
1067 }
1068 }
73848b46 1069
8dd3557a 1070 unlock_page(page);
31dbd01f
IE
1071out:
1072 return err;
1073}
1074
81464e30
HD
1075/*
1076 * try_to_merge_with_ksm_page - like try_to_merge_two_pages,
1077 * but no new kernel page is allocated: kpage must already be a ksm page.
8dd3557a
HD
1078 *
1079 * This function returns 0 if the pages were merged, -EFAULT otherwise.
81464e30 1080 */
8dd3557a
HD
1081static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
1082 struct page *page, struct page *kpage)
81464e30 1083{
8dd3557a 1084 struct mm_struct *mm = rmap_item->mm;
81464e30
HD
1085 struct vm_area_struct *vma;
1086 int err = -EFAULT;
1087
8dd3557a 1088 down_read(&mm->mmap_sem);
85c6e8dd
AA
1089 vma = find_mergeable_vma(mm, rmap_item->address);
1090 if (!vma)
81464e30
HD
1091 goto out;
1092
8dd3557a 1093 err = try_to_merge_one_page(vma, page, kpage);
db114b83
HD
1094 if (err)
1095 goto out;
1096
bc56620b
HD
1097 /* Unstable nid is in union with stable anon_vma: remove first */
1098 remove_rmap_item_from_tree(rmap_item);
1099
db114b83 1100 /* Must get reference to anon_vma while still holding mmap_sem */
9e60109f
PZ
1101 rmap_item->anon_vma = vma->anon_vma;
1102 get_anon_vma(vma->anon_vma);
81464e30 1103out:
8dd3557a 1104 up_read(&mm->mmap_sem);
81464e30
HD
1105 return err;
1106}
1107
31dbd01f
IE
1108/*
1109 * try_to_merge_two_pages - take two identical pages and prepare them
1110 * to be merged into one page.
1111 *
8dd3557a
HD
1112 * This function returns the kpage if we successfully merged two identical
1113 * pages into one ksm page, NULL otherwise.
31dbd01f 1114 *
80e14822 1115 * Note that this function upgrades page to ksm page: if one of the pages
31dbd01f
IE
1116 * is already a ksm page, try_to_merge_with_ksm_page should be used.
1117 */
8dd3557a
HD
1118static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item,
1119 struct page *page,
1120 struct rmap_item *tree_rmap_item,
1121 struct page *tree_page)
31dbd01f 1122{
80e14822 1123 int err;
31dbd01f 1124
80e14822 1125 err = try_to_merge_with_ksm_page(rmap_item, page, NULL);
31dbd01f 1126 if (!err) {
8dd3557a 1127 err = try_to_merge_with_ksm_page(tree_rmap_item,
80e14822 1128 tree_page, page);
31dbd01f 1129 /*
81464e30
HD
1130 * If that fails, we have a ksm page with only one pte
1131 * pointing to it: so break it.
31dbd01f 1132 */
4035c07a 1133 if (err)
8dd3557a 1134 break_cow(rmap_item);
31dbd01f 1135 }
80e14822 1136 return err ? NULL : page;
31dbd01f
IE
1137}
1138
31dbd01f 1139/*
8dd3557a 1140 * stable_tree_search - search for page inside the stable tree
31dbd01f
IE
1141 *
1142 * This function checks if there is a page inside the stable tree
1143 * with identical content to the page that we are scanning right now.
1144 *
7b6ba2c7 1145 * This function returns the stable tree node of identical content if found,
31dbd01f
IE
1146 * NULL otherwise.
1147 */
62b61f61 1148static struct page *stable_tree_search(struct page *page)
31dbd01f 1149{
90bd6fd3 1150 int nid;
ef53d16c 1151 struct rb_root *root;
4146d2d6
HD
1152 struct rb_node **new;
1153 struct rb_node *parent;
1154 struct stable_node *stable_node;
1155 struct stable_node *page_node;
31dbd01f 1156
4146d2d6
HD
1157 page_node = page_stable_node(page);
1158 if (page_node && page_node->head != &migrate_nodes) {
1159 /* ksm page forked */
08beca44 1160 get_page(page);
62b61f61 1161 return page;
08beca44
HD
1162 }
1163
90bd6fd3 1164 nid = get_kpfn_nid(page_to_pfn(page));
ef53d16c 1165 root = root_stable_tree + nid;
4146d2d6 1166again:
ef53d16c 1167 new = &root->rb_node;
4146d2d6 1168 parent = NULL;
90bd6fd3 1169
4146d2d6 1170 while (*new) {
4035c07a 1171 struct page *tree_page;
31dbd01f
IE
1172 int ret;
1173
08beca44 1174 cond_resched();
4146d2d6 1175 stable_node = rb_entry(*new, struct stable_node, node);
8aafa6a4 1176 tree_page = get_ksm_page(stable_node, false);
f2e5ff85
AA
1177 if (!tree_page) {
1178 /*
1179 * If we walked over a stale stable_node,
1180 * get_ksm_page() will call rb_erase() and it
1181 * may rebalance the tree from under us. So
1182 * restart the search from scratch. Returning
1183 * NULL would be safe too, but we'd generate
1184 * false negative insertions just because some
1185 * stable_node was stale.
1186 */
1187 goto again;
1188 }
31dbd01f 1189
4035c07a 1190 ret = memcmp_pages(page, tree_page);
c8d6553b 1191 put_page(tree_page);
31dbd01f 1192
4146d2d6 1193 parent = *new;
c8d6553b 1194 if (ret < 0)
4146d2d6 1195 new = &parent->rb_left;
c8d6553b 1196 else if (ret > 0)
4146d2d6 1197 new = &parent->rb_right;
c8d6553b
HD
1198 else {
1199 /*
1200 * Lock and unlock the stable_node's page (which
1201 * might already have been migrated) so that page
1202 * migration is sure to notice its raised count.
1203 * It would be more elegant to return stable_node
1204 * than kpage, but that involves more changes.
1205 */
1206 tree_page = get_ksm_page(stable_node, true);
4146d2d6 1207 if (tree_page) {
c8d6553b 1208 unlock_page(tree_page);
4146d2d6
HD
1209 if (get_kpfn_nid(stable_node->kpfn) !=
1210 NUMA(stable_node->nid)) {
1211 put_page(tree_page);
1212 goto replace;
1213 }
1214 return tree_page;
1215 }
1216 /*
1217 * There is now a place for page_node, but the tree may
1218 * have been rebalanced, so re-evaluate parent and new.
1219 */
1220 if (page_node)
1221 goto again;
1222 return NULL;
c8d6553b 1223 }
31dbd01f
IE
1224 }
1225
4146d2d6
HD
1226 if (!page_node)
1227 return NULL;
1228
1229 list_del(&page_node->list);
1230 DO_NUMA(page_node->nid = nid);
1231 rb_link_node(&page_node->node, parent, new);
ef53d16c 1232 rb_insert_color(&page_node->node, root);
4146d2d6
HD
1233 get_page(page);
1234 return page;
1235
1236replace:
1237 if (page_node) {
1238 list_del(&page_node->list);
1239 DO_NUMA(page_node->nid = nid);
ef53d16c 1240 rb_replace_node(&stable_node->node, &page_node->node, root);
4146d2d6
HD
1241 get_page(page);
1242 } else {
ef53d16c 1243 rb_erase(&stable_node->node, root);
4146d2d6
HD
1244 page = NULL;
1245 }
1246 stable_node->head = &migrate_nodes;
1247 list_add(&stable_node->list, stable_node->head);
1248 return page;
31dbd01f
IE
1249}
1250
1251/*
e850dcf5 1252 * stable_tree_insert - insert stable tree node pointing to new ksm page
31dbd01f
IE
1253 * into the stable tree.
1254 *
7b6ba2c7
HD
1255 * This function returns the stable tree node just allocated on success,
1256 * NULL otherwise.
31dbd01f 1257 */
7b6ba2c7 1258static struct stable_node *stable_tree_insert(struct page *kpage)
31dbd01f 1259{
90bd6fd3
PH
1260 int nid;
1261 unsigned long kpfn;
ef53d16c 1262 struct rb_root *root;
90bd6fd3 1263 struct rb_node **new;
f2e5ff85 1264 struct rb_node *parent;
7b6ba2c7 1265 struct stable_node *stable_node;
31dbd01f 1266
90bd6fd3
PH
1267 kpfn = page_to_pfn(kpage);
1268 nid = get_kpfn_nid(kpfn);
ef53d16c 1269 root = root_stable_tree + nid;
f2e5ff85
AA
1270again:
1271 parent = NULL;
ef53d16c 1272 new = &root->rb_node;
90bd6fd3 1273
31dbd01f 1274 while (*new) {
4035c07a 1275 struct page *tree_page;
31dbd01f
IE
1276 int ret;
1277
08beca44 1278 cond_resched();
7b6ba2c7 1279 stable_node = rb_entry(*new, struct stable_node, node);
8aafa6a4 1280 tree_page = get_ksm_page(stable_node, false);
f2e5ff85
AA
1281 if (!tree_page) {
1282 /*
1283 * If we walked over a stale stable_node,
1284 * get_ksm_page() will call rb_erase() and it
1285 * may rebalance the tree from under us. So
1286 * restart the search from scratch. Returning
1287 * NULL would be safe too, but we'd generate
1288 * false negative insertions just because some
1289 * stable_node was stale.
1290 */
1291 goto again;
1292 }
31dbd01f 1293
4035c07a
HD
1294 ret = memcmp_pages(kpage, tree_page);
1295 put_page(tree_page);
31dbd01f
IE
1296
1297 parent = *new;
1298 if (ret < 0)
1299 new = &parent->rb_left;
1300 else if (ret > 0)
1301 new = &parent->rb_right;
1302 else {
1303 /*
1304 * It is not a bug that stable_tree_search() didn't
1305 * find this node: because at that time our page was
1306 * not yet write-protected, so may have changed since.
1307 */
1308 return NULL;
1309 }
1310 }
1311
7b6ba2c7
HD
1312 stable_node = alloc_stable_node();
1313 if (!stable_node)
1314 return NULL;
31dbd01f 1315
7b6ba2c7 1316 INIT_HLIST_HEAD(&stable_node->hlist);
90bd6fd3 1317 stable_node->kpfn = kpfn;
08beca44 1318 set_page_stable_node(kpage, stable_node);
4146d2d6 1319 DO_NUMA(stable_node->nid = nid);
e850dcf5 1320 rb_link_node(&stable_node->node, parent, new);
ef53d16c 1321 rb_insert_color(&stable_node->node, root);
08beca44 1322
7b6ba2c7 1323 return stable_node;
31dbd01f
IE
1324}
1325
1326/*
8dd3557a
HD
1327 * unstable_tree_search_insert - search for identical page,
1328 * else insert rmap_item into the unstable tree.
31dbd01f
IE
1329 *
1330 * This function searches for a page in the unstable tree identical to the
1331 * page currently being scanned; and if no identical page is found in the
1332 * tree, we insert rmap_item as a new object into the unstable tree.
1333 *
1334 * This function returns pointer to rmap_item found to be identical
1335 * to the currently scanned page, NULL otherwise.
1336 *
1337 * This function does both searching and inserting, because they share
1338 * the same walking algorithm in an rbtree.
1339 */
8dd3557a
HD
1340static
1341struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item,
1342 struct page *page,
1343 struct page **tree_pagep)
31dbd01f 1344{
90bd6fd3
PH
1345 struct rb_node **new;
1346 struct rb_root *root;
31dbd01f 1347 struct rb_node *parent = NULL;
90bd6fd3
PH
1348 int nid;
1349
1350 nid = get_kpfn_nid(page_to_pfn(page));
ef53d16c 1351 root = root_unstable_tree + nid;
90bd6fd3 1352 new = &root->rb_node;
31dbd01f
IE
1353
1354 while (*new) {
1355 struct rmap_item *tree_rmap_item;
8dd3557a 1356 struct page *tree_page;
31dbd01f
IE
1357 int ret;
1358
d178f27f 1359 cond_resched();
31dbd01f 1360 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
8dd3557a 1361 tree_page = get_mergeable_page(tree_rmap_item);
c8f95ed1 1362 if (!tree_page)
31dbd01f
IE
1363 return NULL;
1364
1365 /*
8dd3557a 1366 * Don't substitute a ksm page for a forked page.
31dbd01f 1367 */
8dd3557a
HD
1368 if (page == tree_page) {
1369 put_page(tree_page);
31dbd01f
IE
1370 return NULL;
1371 }
1372
8dd3557a 1373 ret = memcmp_pages(page, tree_page);
31dbd01f
IE
1374
1375 parent = *new;
1376 if (ret < 0) {
8dd3557a 1377 put_page(tree_page);
31dbd01f
IE
1378 new = &parent->rb_left;
1379 } else if (ret > 0) {
8dd3557a 1380 put_page(tree_page);
31dbd01f 1381 new = &parent->rb_right;
b599cbdf
HD
1382 } else if (!ksm_merge_across_nodes &&
1383 page_to_nid(tree_page) != nid) {
1384 /*
1385 * If tree_page has been migrated to another NUMA node,
1386 * it will be flushed out and put in the right unstable
1387 * tree next time: only merge with it when across_nodes.
1388 */
1389 put_page(tree_page);
1390 return NULL;
31dbd01f 1391 } else {
8dd3557a 1392 *tree_pagep = tree_page;
31dbd01f
IE
1393 return tree_rmap_item;
1394 }
1395 }
1396
7b6ba2c7 1397 rmap_item->address |= UNSTABLE_FLAG;
31dbd01f 1398 rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK);
e850dcf5 1399 DO_NUMA(rmap_item->nid = nid);
31dbd01f 1400 rb_link_node(&rmap_item->node, parent, new);
90bd6fd3 1401 rb_insert_color(&rmap_item->node, root);
31dbd01f 1402
473b0ce4 1403 ksm_pages_unshared++;
31dbd01f
IE
1404 return NULL;
1405}
1406
1407/*
1408 * stable_tree_append - add another rmap_item to the linked list of
1409 * rmap_items hanging off a given node of the stable tree, all sharing
1410 * the same ksm page.
1411 */
1412static void stable_tree_append(struct rmap_item *rmap_item,
7b6ba2c7 1413 struct stable_node *stable_node)
31dbd01f 1414{
7b6ba2c7 1415 rmap_item->head = stable_node;
31dbd01f 1416 rmap_item->address |= STABLE_FLAG;
7b6ba2c7 1417 hlist_add_head(&rmap_item->hlist, &stable_node->hlist);
e178dfde 1418
7b6ba2c7
HD
1419 if (rmap_item->hlist.next)
1420 ksm_pages_sharing++;
1421 else
1422 ksm_pages_shared++;
31dbd01f
IE
1423}
1424
1425/*
81464e30
HD
1426 * cmp_and_merge_page - first see if page can be merged into the stable tree;
1427 * if not, compare checksum to previous and if it's the same, see if page can
1428 * be inserted into the unstable tree, or merged with a page already there and
1429 * both transferred to the stable tree.
31dbd01f
IE
1430 *
1431 * @page: the page that we are searching identical page to.
1432 * @rmap_item: the reverse mapping into the virtual address of this page
1433 */
1434static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
1435{
31dbd01f 1436 struct rmap_item *tree_rmap_item;
8dd3557a 1437 struct page *tree_page = NULL;
7b6ba2c7 1438 struct stable_node *stable_node;
8dd3557a 1439 struct page *kpage;
31dbd01f
IE
1440 unsigned int checksum;
1441 int err;
1442
4146d2d6
HD
1443 stable_node = page_stable_node(page);
1444 if (stable_node) {
1445 if (stable_node->head != &migrate_nodes &&
1446 get_kpfn_nid(stable_node->kpfn) != NUMA(stable_node->nid)) {
1447 rb_erase(&stable_node->node,
ef53d16c 1448 root_stable_tree + NUMA(stable_node->nid));
4146d2d6
HD
1449 stable_node->head = &migrate_nodes;
1450 list_add(&stable_node->list, stable_node->head);
1451 }
1452 if (stable_node->head != &migrate_nodes &&
1453 rmap_item->head == stable_node)
1454 return;
1455 }
31dbd01f
IE
1456
1457 /* We first start with searching the page inside the stable tree */
62b61f61 1458 kpage = stable_tree_search(page);
4146d2d6
HD
1459 if (kpage == page && rmap_item->head == stable_node) {
1460 put_page(kpage);
1461 return;
1462 }
1463
1464 remove_rmap_item_from_tree(rmap_item);
1465
62b61f61 1466 if (kpage) {
08beca44 1467 err = try_to_merge_with_ksm_page(rmap_item, page, kpage);
31dbd01f
IE
1468 if (!err) {
1469 /*
1470 * The page was successfully merged:
1471 * add its rmap_item to the stable tree.
1472 */
5ad64688 1473 lock_page(kpage);
62b61f61 1474 stable_tree_append(rmap_item, page_stable_node(kpage));
5ad64688 1475 unlock_page(kpage);
31dbd01f 1476 }
8dd3557a 1477 put_page(kpage);
31dbd01f
IE
1478 return;
1479 }
1480
1481 /*
4035c07a
HD
1482 * If the hash value of the page has changed from the last time
1483 * we calculated it, this page is changing frequently: therefore we
1484 * don't want to insert it in the unstable tree, and we don't want
1485 * to waste our time searching for something identical to it there.
31dbd01f
IE
1486 */
1487 checksum = calc_checksum(page);
1488 if (rmap_item->oldchecksum != checksum) {
1489 rmap_item->oldchecksum = checksum;
1490 return;
1491 }
1492
8dd3557a
HD
1493 tree_rmap_item =
1494 unstable_tree_search_insert(rmap_item, page, &tree_page);
31dbd01f 1495 if (tree_rmap_item) {
8dd3557a
HD
1496 kpage = try_to_merge_two_pages(rmap_item, page,
1497 tree_rmap_item, tree_page);
1498 put_page(tree_page);
8dd3557a 1499 if (kpage) {
bc56620b
HD
1500 /*
1501 * The pages were successfully merged: insert new
1502 * node in the stable tree and add both rmap_items.
1503 */
5ad64688 1504 lock_page(kpage);
7b6ba2c7
HD
1505 stable_node = stable_tree_insert(kpage);
1506 if (stable_node) {
1507 stable_tree_append(tree_rmap_item, stable_node);
1508 stable_tree_append(rmap_item, stable_node);
1509 }
5ad64688 1510 unlock_page(kpage);
7b6ba2c7 1511
31dbd01f
IE
1512 /*
1513 * If we fail to insert the page into the stable tree,
1514 * we will have 2 virtual addresses that are pointing
1515 * to a ksm page left outside the stable tree,
1516 * in which case we need to break_cow on both.
1517 */
7b6ba2c7 1518 if (!stable_node) {
8dd3557a
HD
1519 break_cow(tree_rmap_item);
1520 break_cow(rmap_item);
31dbd01f
IE
1521 }
1522 }
31dbd01f
IE
1523 }
1524}
1525
1526static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot,
6514d511 1527 struct rmap_item **rmap_list,
31dbd01f
IE
1528 unsigned long addr)
1529{
1530 struct rmap_item *rmap_item;
1531
6514d511
HD
1532 while (*rmap_list) {
1533 rmap_item = *rmap_list;
93d17715 1534 if ((rmap_item->address & PAGE_MASK) == addr)
31dbd01f 1535 return rmap_item;
31dbd01f
IE
1536 if (rmap_item->address > addr)
1537 break;
6514d511 1538 *rmap_list = rmap_item->rmap_list;
31dbd01f 1539 remove_rmap_item_from_tree(rmap_item);
31dbd01f
IE
1540 free_rmap_item(rmap_item);
1541 }
1542
1543 rmap_item = alloc_rmap_item();
1544 if (rmap_item) {
1545 /* It has already been zeroed */
1546 rmap_item->mm = mm_slot->mm;
1547 rmap_item->address = addr;
6514d511
HD
1548 rmap_item->rmap_list = *rmap_list;
1549 *rmap_list = rmap_item;
31dbd01f
IE
1550 }
1551 return rmap_item;
1552}
1553
1554static struct rmap_item *scan_get_next_rmap_item(struct page **page)
1555{
1556 struct mm_struct *mm;
1557 struct mm_slot *slot;
1558 struct vm_area_struct *vma;
1559 struct rmap_item *rmap_item;
90bd6fd3 1560 int nid;
31dbd01f
IE
1561
1562 if (list_empty(&ksm_mm_head.mm_list))
1563 return NULL;
1564
1565 slot = ksm_scan.mm_slot;
1566 if (slot == &ksm_mm_head) {
2919bfd0
HD
1567 /*
1568 * A number of pages can hang around indefinitely on per-cpu
1569 * pagevecs, raised page count preventing write_protect_page
1570 * from merging them. Though it doesn't really matter much,
1571 * it is puzzling to see some stuck in pages_volatile until
1572 * other activity jostles them out, and they also prevented
1573 * LTP's KSM test from succeeding deterministically; so drain
1574 * them here (here rather than on entry to ksm_do_scan(),
1575 * so we don't IPI too often when pages_to_scan is set low).
1576 */
1577 lru_add_drain_all();
1578
4146d2d6
HD
1579 /*
1580 * Whereas stale stable_nodes on the stable_tree itself
1581 * get pruned in the regular course of stable_tree_search(),
1582 * those moved out to the migrate_nodes list can accumulate:
1583 * so prune them once before each full scan.
1584 */
1585 if (!ksm_merge_across_nodes) {
1586 struct stable_node *stable_node;
1587 struct list_head *this, *next;
1588 struct page *page;
1589
1590 list_for_each_safe(this, next, &migrate_nodes) {
1591 stable_node = list_entry(this,
1592 struct stable_node, list);
1593 page = get_ksm_page(stable_node, false);
1594 if (page)
1595 put_page(page);
1596 cond_resched();
1597 }
1598 }
1599
ef53d16c 1600 for (nid = 0; nid < ksm_nr_node_ids; nid++)
90bd6fd3 1601 root_unstable_tree[nid] = RB_ROOT;
31dbd01f
IE
1602
1603 spin_lock(&ksm_mmlist_lock);
1604 slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list);
1605 ksm_scan.mm_slot = slot;
1606 spin_unlock(&ksm_mmlist_lock);
2b472611
HD
1607 /*
1608 * Although we tested list_empty() above, a racing __ksm_exit
1609 * of the last mm on the list may have removed it since then.
1610 */
1611 if (slot == &ksm_mm_head)
1612 return NULL;
31dbd01f
IE
1613next_mm:
1614 ksm_scan.address = 0;
6514d511 1615 ksm_scan.rmap_list = &slot->rmap_list;
31dbd01f
IE
1616 }
1617
1618 mm = slot->mm;
1619 down_read(&mm->mmap_sem);
9ba69294
HD
1620 if (ksm_test_exit(mm))
1621 vma = NULL;
1622 else
1623 vma = find_vma(mm, ksm_scan.address);
1624
1625 for (; vma; vma = vma->vm_next) {
31dbd01f
IE
1626 if (!(vma->vm_flags & VM_MERGEABLE))
1627 continue;
1628 if (ksm_scan.address < vma->vm_start)
1629 ksm_scan.address = vma->vm_start;
1630 if (!vma->anon_vma)
1631 ksm_scan.address = vma->vm_end;
1632
1633 while (ksm_scan.address < vma->vm_end) {
9ba69294
HD
1634 if (ksm_test_exit(mm))
1635 break;
31dbd01f 1636 *page = follow_page(vma, ksm_scan.address, FOLL_GET);
21ae5b01
AA
1637 if (IS_ERR_OR_NULL(*page)) {
1638 ksm_scan.address += PAGE_SIZE;
1639 cond_resched();
1640 continue;
1641 }
29ad768c
AA
1642 if (PageAnon(*page) ||
1643 page_trans_compound_anon(*page)) {
31dbd01f
IE
1644 flush_anon_page(vma, *page, ksm_scan.address);
1645 flush_dcache_page(*page);
1646 rmap_item = get_next_rmap_item(slot,
6514d511 1647 ksm_scan.rmap_list, ksm_scan.address);
31dbd01f 1648 if (rmap_item) {
6514d511
HD
1649 ksm_scan.rmap_list =
1650 &rmap_item->rmap_list;
31dbd01f
IE
1651 ksm_scan.address += PAGE_SIZE;
1652 } else
1653 put_page(*page);
1654 up_read(&mm->mmap_sem);
1655 return rmap_item;
1656 }
21ae5b01 1657 put_page(*page);
31dbd01f
IE
1658 ksm_scan.address += PAGE_SIZE;
1659 cond_resched();
1660 }
1661 }
1662
9ba69294
HD
1663 if (ksm_test_exit(mm)) {
1664 ksm_scan.address = 0;
6514d511 1665 ksm_scan.rmap_list = &slot->rmap_list;
9ba69294 1666 }
31dbd01f
IE
1667 /*
1668 * Nuke all the rmap_items that are above this current rmap:
1669 * because there were no VM_MERGEABLE vmas with such addresses.
1670 */
6514d511 1671 remove_trailing_rmap_items(slot, ksm_scan.rmap_list);
31dbd01f
IE
1672
1673 spin_lock(&ksm_mmlist_lock);
cd551f97
HD
1674 ksm_scan.mm_slot = list_entry(slot->mm_list.next,
1675 struct mm_slot, mm_list);
1676 if (ksm_scan.address == 0) {
1677 /*
1678 * We've completed a full scan of all vmas, holding mmap_sem
1679 * throughout, and found no VM_MERGEABLE: so do the same as
1680 * __ksm_exit does to remove this mm from all our lists now.
9ba69294
HD
1681 * This applies either when cleaning up after __ksm_exit
1682 * (but beware: we can reach here even before __ksm_exit),
1683 * or when all VM_MERGEABLE areas have been unmapped (and
1684 * mmap_sem then protects against race with MADV_MERGEABLE).
cd551f97 1685 */
4ca3a69b 1686 hash_del(&slot->link);
cd551f97 1687 list_del(&slot->mm_list);
9ba69294
HD
1688 spin_unlock(&ksm_mmlist_lock);
1689
cd551f97
HD
1690 free_mm_slot(slot);
1691 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
9ba69294
HD
1692 up_read(&mm->mmap_sem);
1693 mmdrop(mm);
1694 } else {
1695 spin_unlock(&ksm_mmlist_lock);
1696 up_read(&mm->mmap_sem);
cd551f97 1697 }
31dbd01f
IE
1698
1699 /* Repeat until we've completed scanning the whole list */
cd551f97 1700 slot = ksm_scan.mm_slot;
31dbd01f
IE
1701 if (slot != &ksm_mm_head)
1702 goto next_mm;
1703
31dbd01f
IE
1704 ksm_scan.seqnr++;
1705 return NULL;
1706}
1707
1708/**
1709 * ksm_do_scan - the ksm scanner main worker function.
1710 * @scan_npages - number of pages we want to scan before we return.
1711 */
1712static void ksm_do_scan(unsigned int scan_npages)
1713{
1714 struct rmap_item *rmap_item;
22eccdd7 1715 struct page *uninitialized_var(page);
31dbd01f 1716
878aee7d 1717 while (scan_npages-- && likely(!freezing(current))) {
31dbd01f
IE
1718 cond_resched();
1719 rmap_item = scan_get_next_rmap_item(&page);
1720 if (!rmap_item)
1721 return;
4146d2d6 1722 cmp_and_merge_page(page, rmap_item);
31dbd01f
IE
1723 put_page(page);
1724 }
1725}
1726
6e158384
HD
1727static int ksmd_should_run(void)
1728{
1729 return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list);
1730}
1731
31dbd01f
IE
1732static int ksm_scan_thread(void *nothing)
1733{
878aee7d 1734 set_freezable();
339aa624 1735 set_user_nice(current, 5);
31dbd01f
IE
1736
1737 while (!kthread_should_stop()) {
6e158384 1738 mutex_lock(&ksm_thread_mutex);
ef4d43a8 1739 wait_while_offlining();
6e158384 1740 if (ksmd_should_run())
31dbd01f 1741 ksm_do_scan(ksm_thread_pages_to_scan);
6e158384
HD
1742 mutex_unlock(&ksm_thread_mutex);
1743
878aee7d
AA
1744 try_to_freeze();
1745
6e158384 1746 if (ksmd_should_run()) {
31dbd01f
IE
1747 schedule_timeout_interruptible(
1748 msecs_to_jiffies(ksm_thread_sleep_millisecs));
1749 } else {
878aee7d 1750 wait_event_freezable(ksm_thread_wait,
6e158384 1751 ksmd_should_run() || kthread_should_stop());
31dbd01f
IE
1752 }
1753 }
1754 return 0;
1755}
1756
f8af4da3
HD
1757int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
1758 unsigned long end, int advice, unsigned long *vm_flags)
1759{
1760 struct mm_struct *mm = vma->vm_mm;
d952b791 1761 int err;
f8af4da3
HD
1762
1763 switch (advice) {
1764 case MADV_MERGEABLE:
1765 /*
1766 * Be somewhat over-protective for now!
1767 */
1768 if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE |
1769 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
0661a336 1770 VM_HUGETLB | VM_MIXEDMAP))
f8af4da3
HD
1771 return 0; /* just ignore the advice */
1772
cc2383ec
KK
1773#ifdef VM_SAO
1774 if (*vm_flags & VM_SAO)
1775 return 0;
1776#endif
1777
d952b791
HD
1778 if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) {
1779 err = __ksm_enter(mm);
1780 if (err)
1781 return err;
1782 }
f8af4da3
HD
1783
1784 *vm_flags |= VM_MERGEABLE;
1785 break;
1786
1787 case MADV_UNMERGEABLE:
1788 if (!(*vm_flags & VM_MERGEABLE))
1789 return 0; /* just ignore the advice */
1790
d952b791
HD
1791 if (vma->anon_vma) {
1792 err = unmerge_ksm_pages(vma, start, end);
1793 if (err)
1794 return err;
1795 }
f8af4da3
HD
1796
1797 *vm_flags &= ~VM_MERGEABLE;
1798 break;
1799 }
1800
1801 return 0;
1802}
1803
1804int __ksm_enter(struct mm_struct *mm)
1805{
6e158384
HD
1806 struct mm_slot *mm_slot;
1807 int needs_wakeup;
1808
1809 mm_slot = alloc_mm_slot();
31dbd01f
IE
1810 if (!mm_slot)
1811 return -ENOMEM;
1812
6e158384
HD
1813 /* Check ksm_run too? Would need tighter locking */
1814 needs_wakeup = list_empty(&ksm_mm_head.mm_list);
1815
31dbd01f
IE
1816 spin_lock(&ksm_mmlist_lock);
1817 insert_to_mm_slots_hash(mm, mm_slot);
1818 /*
cbf86cfe
HD
1819 * When KSM_RUN_MERGE (or KSM_RUN_STOP),
1820 * insert just behind the scanning cursor, to let the area settle
31dbd01f
IE
1821 * down a little; when fork is followed by immediate exec, we don't
1822 * want ksmd to waste time setting up and tearing down an rmap_list.
cbf86cfe
HD
1823 *
1824 * But when KSM_RUN_UNMERGE, it's important to insert ahead of its
1825 * scanning cursor, otherwise KSM pages in newly forked mms will be
1826 * missed: then we might as well insert at the end of the list.
31dbd01f 1827 */
cbf86cfe
HD
1828 if (ksm_run & KSM_RUN_UNMERGE)
1829 list_add_tail(&mm_slot->mm_list, &ksm_mm_head.mm_list);
1830 else
1831 list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list);
31dbd01f
IE
1832 spin_unlock(&ksm_mmlist_lock);
1833
f8af4da3 1834 set_bit(MMF_VM_MERGEABLE, &mm->flags);
9ba69294 1835 atomic_inc(&mm->mm_count);
6e158384
HD
1836
1837 if (needs_wakeup)
1838 wake_up_interruptible(&ksm_thread_wait);
1839
f8af4da3
HD
1840 return 0;
1841}
1842
1c2fb7a4 1843void __ksm_exit(struct mm_struct *mm)
f8af4da3 1844{
cd551f97 1845 struct mm_slot *mm_slot;
9ba69294 1846 int easy_to_free = 0;
cd551f97 1847
31dbd01f 1848 /*
9ba69294
HD
1849 * This process is exiting: if it's straightforward (as is the
1850 * case when ksmd was never running), free mm_slot immediately.
1851 * But if it's at the cursor or has rmap_items linked to it, use
1852 * mmap_sem to synchronize with any break_cows before pagetables
1853 * are freed, and leave the mm_slot on the list for ksmd to free.
1854 * Beware: ksm may already have noticed it exiting and freed the slot.
31dbd01f 1855 */
9ba69294 1856
cd551f97
HD
1857 spin_lock(&ksm_mmlist_lock);
1858 mm_slot = get_mm_slot(mm);
9ba69294 1859 if (mm_slot && ksm_scan.mm_slot != mm_slot) {
6514d511 1860 if (!mm_slot->rmap_list) {
4ca3a69b 1861 hash_del(&mm_slot->link);
9ba69294
HD
1862 list_del(&mm_slot->mm_list);
1863 easy_to_free = 1;
1864 } else {
1865 list_move(&mm_slot->mm_list,
1866 &ksm_scan.mm_slot->mm_list);
1867 }
cd551f97 1868 }
cd551f97
HD
1869 spin_unlock(&ksm_mmlist_lock);
1870
9ba69294
HD
1871 if (easy_to_free) {
1872 free_mm_slot(mm_slot);
1873 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
1874 mmdrop(mm);
1875 } else if (mm_slot) {
9ba69294
HD
1876 down_write(&mm->mmap_sem);
1877 up_write(&mm->mmap_sem);
9ba69294 1878 }
31dbd01f
IE
1879}
1880
cbf86cfe 1881struct page *ksm_might_need_to_copy(struct page *page,
5ad64688
HD
1882 struct vm_area_struct *vma, unsigned long address)
1883{
cbf86cfe 1884 struct anon_vma *anon_vma = page_anon_vma(page);
5ad64688
HD
1885 struct page *new_page;
1886
cbf86cfe
HD
1887 if (PageKsm(page)) {
1888 if (page_stable_node(page) &&
1889 !(ksm_run & KSM_RUN_UNMERGE))
1890 return page; /* no need to copy it */
1891 } else if (!anon_vma) {
1892 return page; /* no need to copy it */
1893 } else if (anon_vma->root == vma->anon_vma->root &&
1894 page->index == linear_page_index(vma, address)) {
1895 return page; /* still no need to copy it */
1896 }
1897 if (!PageUptodate(page))
1898 return page; /* let do_swap_page report the error */
1899
5ad64688
HD
1900 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
1901 if (new_page) {
1902 copy_user_highpage(new_page, page, address, vma);
1903
1904 SetPageDirty(new_page);
1905 __SetPageUptodate(new_page);
5ad64688 1906 __set_page_locked(new_page);
5ad64688
HD
1907 }
1908
5ad64688
HD
1909 return new_page;
1910}
1911
051ac83a 1912int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
e9995ef9
HD
1913{
1914 struct stable_node *stable_node;
e9995ef9
HD
1915 struct rmap_item *rmap_item;
1916 int ret = SWAP_AGAIN;
1917 int search_new_forks = 0;
1918
309381fe 1919 VM_BUG_ON_PAGE(!PageKsm(page), page);
9f32624b
JK
1920
1921 /*
1922 * Rely on the page lock to protect against concurrent modifications
1923 * to that page's node of the stable tree.
1924 */
309381fe 1925 VM_BUG_ON_PAGE(!PageLocked(page), page);
e9995ef9
HD
1926
1927 stable_node = page_stable_node(page);
1928 if (!stable_node)
1929 return ret;
1930again:
b67bfe0d 1931 hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
e9995ef9 1932 struct anon_vma *anon_vma = rmap_item->anon_vma;
5beb4930 1933 struct anon_vma_chain *vmac;
e9995ef9
HD
1934 struct vm_area_struct *vma;
1935
ad12695f 1936 cond_resched();
b6b19f25 1937 anon_vma_lock_read(anon_vma);
bf181b9f
ML
1938 anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
1939 0, ULONG_MAX) {
ad12695f 1940 cond_resched();
5beb4930 1941 vma = vmac->vma;
e9995ef9
HD
1942 if (rmap_item->address < vma->vm_start ||
1943 rmap_item->address >= vma->vm_end)
1944 continue;
1945 /*
1946 * Initially we examine only the vma which covers this
1947 * rmap_item; but later, if there is still work to do,
1948 * we examine covering vmas in other mms: in case they
1949 * were forked from the original since ksmd passed.
1950 */
1951 if ((rmap_item->mm == vma->vm_mm) == search_new_forks)
1952 continue;
1953
0dd1c7bb
JK
1954 if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
1955 continue;
1956
051ac83a
JK
1957 ret = rwc->rmap_one(page, vma,
1958 rmap_item->address, rwc->arg);
e9995ef9 1959 if (ret != SWAP_AGAIN) {
b6b19f25 1960 anon_vma_unlock_read(anon_vma);
e9995ef9
HD
1961 goto out;
1962 }
0dd1c7bb
JK
1963 if (rwc->done && rwc->done(page)) {
1964 anon_vma_unlock_read(anon_vma);
1965 goto out;
1966 }
e9995ef9 1967 }
b6b19f25 1968 anon_vma_unlock_read(anon_vma);
e9995ef9
HD
1969 }
1970 if (!search_new_forks++)
1971 goto again;
1972out:
1973 return ret;
1974}
1975
52629506 1976#ifdef CONFIG_MIGRATION
e9995ef9
HD
1977void ksm_migrate_page(struct page *newpage, struct page *oldpage)
1978{
1979 struct stable_node *stable_node;
1980
309381fe
SL
1981 VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
1982 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1983 VM_BUG_ON_PAGE(newpage->mapping != oldpage->mapping, newpage);
e9995ef9
HD
1984
1985 stable_node = page_stable_node(newpage);
1986 if (stable_node) {
309381fe 1987 VM_BUG_ON_PAGE(stable_node->kpfn != page_to_pfn(oldpage), oldpage);
62b61f61 1988 stable_node->kpfn = page_to_pfn(newpage);
c8d6553b
HD
1989 /*
1990 * newpage->mapping was set in advance; now we need smp_wmb()
1991 * to make sure that the new stable_node->kpfn is visible
1992 * to get_ksm_page() before it can see that oldpage->mapping
1993 * has gone stale (or that PageSwapCache has been cleared).
1994 */
1995 smp_wmb();
1996 set_page_stable_node(oldpage, NULL);
e9995ef9
HD
1997 }
1998}
1999#endif /* CONFIG_MIGRATION */
2000
62b61f61 2001#ifdef CONFIG_MEMORY_HOTREMOVE
ef4d43a8
HD
2002static void wait_while_offlining(void)
2003{
2004 while (ksm_run & KSM_RUN_OFFLINE) {
2005 mutex_unlock(&ksm_thread_mutex);
2006 wait_on_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE),
74316201 2007 TASK_UNINTERRUPTIBLE);
ef4d43a8
HD
2008 mutex_lock(&ksm_thread_mutex);
2009 }
2010}
2011
ee0ea59c
HD
2012static void ksm_check_stable_tree(unsigned long start_pfn,
2013 unsigned long end_pfn)
62b61f61 2014{
ee0ea59c 2015 struct stable_node *stable_node;
4146d2d6 2016 struct list_head *this, *next;
62b61f61 2017 struct rb_node *node;
90bd6fd3 2018 int nid;
62b61f61 2019
ef53d16c
HD
2020 for (nid = 0; nid < ksm_nr_node_ids; nid++) {
2021 node = rb_first(root_stable_tree + nid);
ee0ea59c 2022 while (node) {
90bd6fd3
PH
2023 stable_node = rb_entry(node, struct stable_node, node);
2024 if (stable_node->kpfn >= start_pfn &&
ee0ea59c
HD
2025 stable_node->kpfn < end_pfn) {
2026 /*
2027 * Don't get_ksm_page, page has already gone:
2028 * which is why we keep kpfn instead of page*
2029 */
2030 remove_node_from_stable_tree(stable_node);
ef53d16c 2031 node = rb_first(root_stable_tree + nid);
ee0ea59c
HD
2032 } else
2033 node = rb_next(node);
2034 cond_resched();
90bd6fd3 2035 }
ee0ea59c 2036 }
4146d2d6
HD
2037 list_for_each_safe(this, next, &migrate_nodes) {
2038 stable_node = list_entry(this, struct stable_node, list);
2039 if (stable_node->kpfn >= start_pfn &&
2040 stable_node->kpfn < end_pfn)
2041 remove_node_from_stable_tree(stable_node);
2042 cond_resched();
2043 }
62b61f61
HD
2044}
2045
2046static int ksm_memory_callback(struct notifier_block *self,
2047 unsigned long action, void *arg)
2048{
2049 struct memory_notify *mn = arg;
62b61f61
HD
2050
2051 switch (action) {
2052 case MEM_GOING_OFFLINE:
2053 /*
ef4d43a8
HD
2054 * Prevent ksm_do_scan(), unmerge_and_remove_all_rmap_items()
2055 * and remove_all_stable_nodes() while memory is going offline:
2056 * it is unsafe for them to touch the stable tree at this time.
2057 * But unmerge_ksm_pages(), rmap lookups and other entry points
2058 * which do not need the ksm_thread_mutex are all safe.
62b61f61 2059 */
ef4d43a8
HD
2060 mutex_lock(&ksm_thread_mutex);
2061 ksm_run |= KSM_RUN_OFFLINE;
2062 mutex_unlock(&ksm_thread_mutex);
62b61f61
HD
2063 break;
2064
2065 case MEM_OFFLINE:
2066 /*
2067 * Most of the work is done by page migration; but there might
2068 * be a few stable_nodes left over, still pointing to struct
ee0ea59c
HD
2069 * pages which have been offlined: prune those from the tree,
2070 * otherwise get_ksm_page() might later try to access a
2071 * non-existent struct page.
62b61f61 2072 */
ee0ea59c
HD
2073 ksm_check_stable_tree(mn->start_pfn,
2074 mn->start_pfn + mn->nr_pages);
62b61f61
HD
2075 /* fallthrough */
2076
2077 case MEM_CANCEL_OFFLINE:
ef4d43a8
HD
2078 mutex_lock(&ksm_thread_mutex);
2079 ksm_run &= ~KSM_RUN_OFFLINE;
62b61f61 2080 mutex_unlock(&ksm_thread_mutex);
ef4d43a8
HD
2081
2082 smp_mb(); /* wake_up_bit advises this */
2083 wake_up_bit(&ksm_run, ilog2(KSM_RUN_OFFLINE));
62b61f61
HD
2084 break;
2085 }
2086 return NOTIFY_OK;
2087}
ef4d43a8
HD
2088#else
2089static void wait_while_offlining(void)
2090{
2091}
62b61f61
HD
2092#endif /* CONFIG_MEMORY_HOTREMOVE */
2093
2ffd8679
HD
2094#ifdef CONFIG_SYSFS
2095/*
2096 * This all compiles without CONFIG_SYSFS, but is a waste of space.
2097 */
2098
31dbd01f
IE
2099#define KSM_ATTR_RO(_name) \
2100 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
2101#define KSM_ATTR(_name) \
2102 static struct kobj_attribute _name##_attr = \
2103 __ATTR(_name, 0644, _name##_show, _name##_store)
2104
2105static ssize_t sleep_millisecs_show(struct kobject *kobj,
2106 struct kobj_attribute *attr, char *buf)
2107{
2108 return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs);
2109}
2110
2111static ssize_t sleep_millisecs_store(struct kobject *kobj,
2112 struct kobj_attribute *attr,
2113 const char *buf, size_t count)
2114{
2115 unsigned long msecs;
2116 int err;
2117
3dbb95f7 2118 err = kstrtoul(buf, 10, &msecs);
31dbd01f
IE
2119 if (err || msecs > UINT_MAX)
2120 return -EINVAL;
2121
2122 ksm_thread_sleep_millisecs = msecs;
2123
2124 return count;
2125}
2126KSM_ATTR(sleep_millisecs);
2127
2128static ssize_t pages_to_scan_show(struct kobject *kobj,
2129 struct kobj_attribute *attr, char *buf)
2130{
2131 return sprintf(buf, "%u\n", ksm_thread_pages_to_scan);
2132}
2133
2134static ssize_t pages_to_scan_store(struct kobject *kobj,
2135 struct kobj_attribute *attr,
2136 const char *buf, size_t count)
2137{
2138 int err;
2139 unsigned long nr_pages;
2140
3dbb95f7 2141 err = kstrtoul(buf, 10, &nr_pages);
31dbd01f
IE
2142 if (err || nr_pages > UINT_MAX)
2143 return -EINVAL;
2144
2145 ksm_thread_pages_to_scan = nr_pages;
2146
2147 return count;
2148}
2149KSM_ATTR(pages_to_scan);
2150
2151static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr,
2152 char *buf)
2153{
ef4d43a8 2154 return sprintf(buf, "%lu\n", ksm_run);
31dbd01f
IE
2155}
2156
2157static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
2158 const char *buf, size_t count)
2159{
2160 int err;
2161 unsigned long flags;
2162
3dbb95f7 2163 err = kstrtoul(buf, 10, &flags);
31dbd01f
IE
2164 if (err || flags > UINT_MAX)
2165 return -EINVAL;
2166 if (flags > KSM_RUN_UNMERGE)
2167 return -EINVAL;
2168
2169 /*
2170 * KSM_RUN_MERGE sets ksmd running, and 0 stops it running.
2171 * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items,
d0f209f6
HD
2172 * breaking COW to free the pages_shared (but leaves mm_slots
2173 * on the list for when ksmd may be set running again).
31dbd01f
IE
2174 */
2175
2176 mutex_lock(&ksm_thread_mutex);
ef4d43a8 2177 wait_while_offlining();
31dbd01f
IE
2178 if (ksm_run != flags) {
2179 ksm_run = flags;
d952b791 2180 if (flags & KSM_RUN_UNMERGE) {
e1e12d2f 2181 set_current_oom_origin();
d952b791 2182 err = unmerge_and_remove_all_rmap_items();
e1e12d2f 2183 clear_current_oom_origin();
d952b791
HD
2184 if (err) {
2185 ksm_run = KSM_RUN_STOP;
2186 count = err;
2187 }
2188 }
31dbd01f
IE
2189 }
2190 mutex_unlock(&ksm_thread_mutex);
2191
2192 if (flags & KSM_RUN_MERGE)
2193 wake_up_interruptible(&ksm_thread_wait);
2194
2195 return count;
2196}
2197KSM_ATTR(run);
2198
90bd6fd3
PH
2199#ifdef CONFIG_NUMA
2200static ssize_t merge_across_nodes_show(struct kobject *kobj,
2201 struct kobj_attribute *attr, char *buf)
2202{
2203 return sprintf(buf, "%u\n", ksm_merge_across_nodes);
2204}
2205
2206static ssize_t merge_across_nodes_store(struct kobject *kobj,
2207 struct kobj_attribute *attr,
2208 const char *buf, size_t count)
2209{
2210 int err;
2211 unsigned long knob;
2212
2213 err = kstrtoul(buf, 10, &knob);
2214 if (err)
2215 return err;
2216 if (knob > 1)
2217 return -EINVAL;
2218
2219 mutex_lock(&ksm_thread_mutex);
ef4d43a8 2220 wait_while_offlining();
90bd6fd3 2221 if (ksm_merge_across_nodes != knob) {
cbf86cfe 2222 if (ksm_pages_shared || remove_all_stable_nodes())
90bd6fd3 2223 err = -EBUSY;
ef53d16c
HD
2224 else if (root_stable_tree == one_stable_tree) {
2225 struct rb_root *buf;
2226 /*
2227 * This is the first time that we switch away from the
2228 * default of merging across nodes: must now allocate
2229 * a buffer to hold as many roots as may be needed.
2230 * Allocate stable and unstable together:
2231 * MAXSMP NODES_SHIFT 10 will use 16kB.
2232 */
bafe1e14
JP
2233 buf = kcalloc(nr_node_ids + nr_node_ids, sizeof(*buf),
2234 GFP_KERNEL);
ef53d16c
HD
2235 /* Let us assume that RB_ROOT is NULL is zero */
2236 if (!buf)
2237 err = -ENOMEM;
2238 else {
2239 root_stable_tree = buf;
2240 root_unstable_tree = buf + nr_node_ids;
2241 /* Stable tree is empty but not the unstable */
2242 root_unstable_tree[0] = one_unstable_tree[0];
2243 }
2244 }
2245 if (!err) {
90bd6fd3 2246 ksm_merge_across_nodes = knob;
ef53d16c
HD
2247 ksm_nr_node_ids = knob ? 1 : nr_node_ids;
2248 }
90bd6fd3
PH
2249 }
2250 mutex_unlock(&ksm_thread_mutex);
2251
2252 return err ? err : count;
2253}
2254KSM_ATTR(merge_across_nodes);
2255#endif
2256
b4028260
HD
2257static ssize_t pages_shared_show(struct kobject *kobj,
2258 struct kobj_attribute *attr, char *buf)
2259{
2260 return sprintf(buf, "%lu\n", ksm_pages_shared);
2261}
2262KSM_ATTR_RO(pages_shared);
2263
2264static ssize_t pages_sharing_show(struct kobject *kobj,
2265 struct kobj_attribute *attr, char *buf)
2266{
e178dfde 2267 return sprintf(buf, "%lu\n", ksm_pages_sharing);
b4028260
HD
2268}
2269KSM_ATTR_RO(pages_sharing);
2270
473b0ce4
HD
2271static ssize_t pages_unshared_show(struct kobject *kobj,
2272 struct kobj_attribute *attr, char *buf)
2273{
2274 return sprintf(buf, "%lu\n", ksm_pages_unshared);
2275}
2276KSM_ATTR_RO(pages_unshared);
2277
2278static ssize_t pages_volatile_show(struct kobject *kobj,
2279 struct kobj_attribute *attr, char *buf)
2280{
2281 long ksm_pages_volatile;
2282
2283 ksm_pages_volatile = ksm_rmap_items - ksm_pages_shared
2284 - ksm_pages_sharing - ksm_pages_unshared;
2285 /*
2286 * It was not worth any locking to calculate that statistic,
2287 * but it might therefore sometimes be negative: conceal that.
2288 */
2289 if (ksm_pages_volatile < 0)
2290 ksm_pages_volatile = 0;
2291 return sprintf(buf, "%ld\n", ksm_pages_volatile);
2292}
2293KSM_ATTR_RO(pages_volatile);
2294
2295static ssize_t full_scans_show(struct kobject *kobj,
2296 struct kobj_attribute *attr, char *buf)
2297{
2298 return sprintf(buf, "%lu\n", ksm_scan.seqnr);
2299}
2300KSM_ATTR_RO(full_scans);
2301
31dbd01f
IE
2302static struct attribute *ksm_attrs[] = {
2303 &sleep_millisecs_attr.attr,
2304 &pages_to_scan_attr.attr,
2305 &run_attr.attr,
b4028260
HD
2306 &pages_shared_attr.attr,
2307 &pages_sharing_attr.attr,
473b0ce4
HD
2308 &pages_unshared_attr.attr,
2309 &pages_volatile_attr.attr,
2310 &full_scans_attr.attr,
90bd6fd3
PH
2311#ifdef CONFIG_NUMA
2312 &merge_across_nodes_attr.attr,
2313#endif
31dbd01f
IE
2314 NULL,
2315};
2316
2317static struct attribute_group ksm_attr_group = {
2318 .attrs = ksm_attrs,
2319 .name = "ksm",
2320};
2ffd8679 2321#endif /* CONFIG_SYSFS */
31dbd01f
IE
2322
2323static int __init ksm_init(void)
2324{
2325 struct task_struct *ksm_thread;
2326 int err;
2327
2328 err = ksm_slab_init();
2329 if (err)
2330 goto out;
2331
31dbd01f
IE
2332 ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd");
2333 if (IS_ERR(ksm_thread)) {
25acde31 2334 pr_err("ksm: creating kthread failed\n");
31dbd01f 2335 err = PTR_ERR(ksm_thread);
d9f8984c 2336 goto out_free;
31dbd01f
IE
2337 }
2338
2ffd8679 2339#ifdef CONFIG_SYSFS
31dbd01f
IE
2340 err = sysfs_create_group(mm_kobj, &ksm_attr_group);
2341 if (err) {
25acde31 2342 pr_err("ksm: register sysfs failed\n");
2ffd8679 2343 kthread_stop(ksm_thread);
d9f8984c 2344 goto out_free;
31dbd01f 2345 }
c73602ad
HD
2346#else
2347 ksm_run = KSM_RUN_MERGE; /* no way for user to start it */
2348
2ffd8679 2349#endif /* CONFIG_SYSFS */
31dbd01f 2350
62b61f61 2351#ifdef CONFIG_MEMORY_HOTREMOVE
ef4d43a8 2352 /* There is no significance to this priority 100 */
62b61f61
HD
2353 hotplug_memory_notifier(ksm_memory_callback, 100);
2354#endif
31dbd01f
IE
2355 return 0;
2356
d9f8984c 2357out_free:
31dbd01f
IE
2358 ksm_slab_free();
2359out:
2360 return err;
f8af4da3 2361}
a64fb3cd 2362subsys_initcall(ksm_init);