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-rw-r--r--mm/ksm.c1489
1 files changed, 1484 insertions, 5 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 8b76008fcd32..2c02094807e0 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1,11 +1,1285 @@
1/* 1/*
2 * Initial dummy version just to illustrate KSM's interface to other files. 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 *
7 * Copyright (C) 2008 Red Hat, Inc.
8 * Authors:
9 * Izik Eidus
10 * Andrea Arcangeli
11 * Chris Wright
12 *
13 * This work is licensed under the terms of the GNU GPL, version 2.
3 */ 14 */
4 15
5#include <linux/errno.h> 16#include <linux/errno.h>
17#include <linux/mm.h>
18#include <linux/fs.h>
6#include <linux/mman.h> 19#include <linux/mman.h>
20#include <linux/sched.h>
21#include <linux/rwsem.h>
22#include <linux/pagemap.h>
23#include <linux/rmap.h>
24#include <linux/spinlock.h>
25#include <linux/jhash.h>
26#include <linux/delay.h>
27#include <linux/kthread.h>
28#include <linux/wait.h>
29#include <linux/slab.h>
30#include <linux/rbtree.h>
31#include <linux/mmu_notifier.h>
7#include <linux/ksm.h> 32#include <linux/ksm.h>
8 33
34#include <asm/tlbflush.h>
35
36/*
37 * A few notes about the KSM scanning process,
38 * to make it easier to understand the data structures below:
39 *
40 * In order to reduce excessive scanning, KSM sorts the memory pages by their
41 * contents into a data structure that holds pointers to the pages' locations.
42 *
43 * Since the contents of the pages may change at any moment, KSM cannot just
44 * insert the pages into a normal sorted tree and expect it to find anything.
45 * Therefore KSM uses two data structures - the stable and the unstable tree.
46 *
47 * The stable tree holds pointers to all the merged pages (ksm pages), sorted
48 * by their contents. Because each such page is write-protected, searching on
49 * this tree is fully assured to be working (except when pages are unmapped),
50 * and therefore this tree is called the stable tree.
51 *
52 * In addition to the stable tree, KSM uses a second data structure called the
53 * unstable tree: this tree holds pointers to pages which have been found to
54 * be "unchanged for a period of time". The unstable tree sorts these pages
55 * by their contents, but since they are not write-protected, KSM cannot rely
56 * upon the unstable tree to work correctly - the unstable tree is liable to
57 * be corrupted as its contents are modified, and so it is called unstable.
58 *
59 * KSM solves this problem by several techniques:
60 *
61 * 1) The unstable tree is flushed every time KSM completes scanning all
62 * memory areas, and then the tree is rebuilt again from the beginning.
63 * 2) KSM will only insert into the unstable tree, pages whose hash value
64 * has not changed since the previous scan of all memory areas.
65 * 3) The unstable tree is a RedBlack Tree - so its balancing is based on the
66 * colors of the nodes and not on their contents, assuring that even when
67 * the tree gets "corrupted" it won't get out of balance, so scanning time
68 * remains the same (also, searching and inserting nodes in an rbtree uses
69 * the same algorithm, so we have no overhead when we flush and rebuild).
70 * 4) KSM never flushes the stable tree, which means that even if it were to
71 * take 10 attempts to find a page in the unstable tree, once it is found,
72 * it is secured in the stable tree. (When we scan a new page, we first
73 * compare it against the stable tree, and then against the unstable tree.)
74 */
75
76/**
77 * struct mm_slot - ksm information per mm that is being scanned
78 * @link: link to the mm_slots hash list
79 * @mm_list: link into the mm_slots list, rooted in ksm_mm_head
80 * @rmap_list: head for this mm_slot's list of rmap_items
81 * @mm: the mm that this information is valid for
82 */
83struct mm_slot {
84 struct hlist_node link;
85 struct list_head mm_list;
86 struct list_head rmap_list;
87 struct mm_struct *mm;
88};
89
90/**
91 * struct ksm_scan - cursor for scanning
92 * @mm_slot: the current mm_slot we are scanning
93 * @address: the next address inside that to be scanned
94 * @rmap_item: the current rmap that we are scanning inside the rmap_list
95 * @seqnr: count of completed full scans (needed when removing unstable node)
96 *
97 * There is only the one ksm_scan instance of this cursor structure.
98 */
99struct ksm_scan {
100 struct mm_slot *mm_slot;
101 unsigned long address;
102 struct rmap_item *rmap_item;
103 unsigned long seqnr;
104};
105
106/**
107 * struct rmap_item - reverse mapping item for virtual addresses
108 * @link: link into mm_slot's rmap_list (rmap_list is per mm)
109 * @mm: the memory structure this rmap_item is pointing into
110 * @address: the virtual address this rmap_item tracks (+ flags in low bits)
111 * @oldchecksum: previous checksum of the page at that virtual address
112 * @node: rb_node of this rmap_item in either unstable or stable tree
113 * @next: next rmap_item hanging off the same node of the stable tree
114 * @prev: previous rmap_item hanging off the same node of the stable tree
115 */
116struct rmap_item {
117 struct list_head link;
118 struct mm_struct *mm;
119 unsigned long address; /* + low bits used for flags below */
120 union {
121 unsigned int oldchecksum; /* when unstable */
122 struct rmap_item *next; /* when stable */
123 };
124 union {
125 struct rb_node node; /* when tree node */
126 struct rmap_item *prev; /* in stable list */
127 };
128};
129
130#define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */
131#define NODE_FLAG 0x100 /* is a node of unstable or stable tree */
132#define STABLE_FLAG 0x200 /* is a node or list item of stable tree */
133
134/* The stable and unstable tree heads */
135static struct rb_root root_stable_tree = RB_ROOT;
136static struct rb_root root_unstable_tree = RB_ROOT;
137
138#define MM_SLOTS_HASH_HEADS 1024
139static struct hlist_head *mm_slots_hash;
140
141static struct mm_slot ksm_mm_head = {
142 .mm_list = LIST_HEAD_INIT(ksm_mm_head.mm_list),
143};
144static struct ksm_scan ksm_scan = {
145 .mm_slot = &ksm_mm_head,
146};
147
148static struct kmem_cache *rmap_item_cache;
149static struct kmem_cache *mm_slot_cache;
150
151/* The number of nodes in the stable tree */
152static unsigned long ksm_kernel_pages_allocated;
153
154/* The number of page slots sharing those nodes */
155static unsigned long ksm_pages_shared;
156
157/* Limit on the number of unswappable pages used */
158static unsigned long ksm_max_kernel_pages;
159
160/* Number of pages ksmd should scan in one batch */
161static unsigned int ksm_thread_pages_to_scan;
162
163/* Milliseconds ksmd should sleep between batches */
164static unsigned int ksm_thread_sleep_millisecs;
165
166#define KSM_RUN_STOP 0
167#define KSM_RUN_MERGE 1
168#define KSM_RUN_UNMERGE 2
169static unsigned int ksm_run;
170
171static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait);
172static DEFINE_MUTEX(ksm_thread_mutex);
173static DEFINE_SPINLOCK(ksm_mmlist_lock);
174
175#define KSM_KMEM_CACHE(__struct, __flags) kmem_cache_create("ksm_"#__struct,\
176 sizeof(struct __struct), __alignof__(struct __struct),\
177 (__flags), NULL)
178
179static int __init ksm_slab_init(void)
180{
181 rmap_item_cache = KSM_KMEM_CACHE(rmap_item, 0);
182 if (!rmap_item_cache)
183 goto out;
184
185 mm_slot_cache = KSM_KMEM_CACHE(mm_slot, 0);
186 if (!mm_slot_cache)
187 goto out_free;
188
189 return 0;
190
191out_free:
192 kmem_cache_destroy(rmap_item_cache);
193out:
194 return -ENOMEM;
195}
196
197static void __init ksm_slab_free(void)
198{
199 kmem_cache_destroy(mm_slot_cache);
200 kmem_cache_destroy(rmap_item_cache);
201 mm_slot_cache = NULL;
202}
203
204static inline struct rmap_item *alloc_rmap_item(void)
205{
206 return kmem_cache_zalloc(rmap_item_cache, GFP_KERNEL);
207}
208
209static inline void free_rmap_item(struct rmap_item *rmap_item)
210{
211 rmap_item->mm = NULL; /* debug safety */
212 kmem_cache_free(rmap_item_cache, rmap_item);
213}
214
215static inline struct mm_slot *alloc_mm_slot(void)
216{
217 if (!mm_slot_cache) /* initialization failed */
218 return NULL;
219 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
220}
221
222static inline void free_mm_slot(struct mm_slot *mm_slot)
223{
224 kmem_cache_free(mm_slot_cache, mm_slot);
225}
226
227static int __init mm_slots_hash_init(void)
228{
229 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
230 GFP_KERNEL);
231 if (!mm_slots_hash)
232 return -ENOMEM;
233 return 0;
234}
235
236static void __init mm_slots_hash_free(void)
237{
238 kfree(mm_slots_hash);
239}
240
241static struct mm_slot *get_mm_slot(struct mm_struct *mm)
242{
243 struct mm_slot *mm_slot;
244 struct hlist_head *bucket;
245 struct hlist_node *node;
246
247 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
248 % MM_SLOTS_HASH_HEADS];
249 hlist_for_each_entry(mm_slot, node, bucket, link) {
250 if (mm == mm_slot->mm)
251 return mm_slot;
252 }
253 return NULL;
254}
255
256static void insert_to_mm_slots_hash(struct mm_struct *mm,
257 struct mm_slot *mm_slot)
258{
259 struct hlist_head *bucket;
260
261 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
262 % MM_SLOTS_HASH_HEADS];
263 mm_slot->mm = mm;
264 INIT_LIST_HEAD(&mm_slot->rmap_list);
265 hlist_add_head(&mm_slot->link, bucket);
266}
267
268static inline int in_stable_tree(struct rmap_item *rmap_item)
269{
270 return rmap_item->address & STABLE_FLAG;
271}
272
273/*
274 * We use break_ksm to break COW on a ksm page: it's a stripped down
275 *
276 * if (get_user_pages(current, mm, addr, 1, 1, 1, &page, NULL) == 1)
277 * put_page(page);
278 *
279 * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma,
280 * in case the application has unmapped and remapped mm,addr meanwhile.
281 * Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP
282 * mmap of /dev/mem or /dev/kmem, where we would not want to touch it.
283 */
284static void break_ksm(struct vm_area_struct *vma, unsigned long addr)
285{
286 struct page *page;
287 int ret;
288
289 do {
290 cond_resched();
291 page = follow_page(vma, addr, FOLL_GET);
292 if (!page)
293 break;
294 if (PageKsm(page))
295 ret = handle_mm_fault(vma->vm_mm, vma, addr,
296 FAULT_FLAG_WRITE);
297 else
298 ret = VM_FAULT_WRITE;
299 put_page(page);
300 } while (!(ret & (VM_FAULT_WRITE | VM_FAULT_SIGBUS)));
301
302 /* Which leaves us looping there if VM_FAULT_OOM: hmmm... */
303}
304
305static void __break_cow(struct mm_struct *mm, unsigned long addr)
306{
307 struct vm_area_struct *vma;
308
309 vma = find_vma(mm, addr);
310 if (!vma || vma->vm_start > addr)
311 return;
312 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
313 return;
314 break_ksm(vma, addr);
315}
316
317static void break_cow(struct mm_struct *mm, unsigned long addr)
318{
319 down_read(&mm->mmap_sem);
320 __break_cow(mm, addr);
321 up_read(&mm->mmap_sem);
322}
323
324static struct page *get_mergeable_page(struct rmap_item *rmap_item)
325{
326 struct mm_struct *mm = rmap_item->mm;
327 unsigned long addr = rmap_item->address;
328 struct vm_area_struct *vma;
329 struct page *page;
330
331 down_read(&mm->mmap_sem);
332 vma = find_vma(mm, addr);
333 if (!vma || vma->vm_start > addr)
334 goto out;
335 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
336 goto out;
337
338 page = follow_page(vma, addr, FOLL_GET);
339 if (!page)
340 goto out;
341 if (PageAnon(page)) {
342 flush_anon_page(vma, page, addr);
343 flush_dcache_page(page);
344 } else {
345 put_page(page);
346out: page = NULL;
347 }
348 up_read(&mm->mmap_sem);
349 return page;
350}
351
352/*
353 * get_ksm_page: checks if the page at the virtual address in rmap_item
354 * is still PageKsm, in which case we can trust the content of the page,
355 * and it returns the gotten page; but NULL if the page has been zapped.
356 */
357static struct page *get_ksm_page(struct rmap_item *rmap_item)
358{
359 struct page *page;
360
361 page = get_mergeable_page(rmap_item);
362 if (page && !PageKsm(page)) {
363 put_page(page);
364 page = NULL;
365 }
366 return page;
367}
368
369/*
370 * Removing rmap_item from stable or unstable tree.
371 * This function will clean the information from the stable/unstable tree.
372 */
373static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
374{
375 if (in_stable_tree(rmap_item)) {
376 struct rmap_item *next_item = rmap_item->next;
377
378 if (rmap_item->address & NODE_FLAG) {
379 if (next_item) {
380 rb_replace_node(&rmap_item->node,
381 &next_item->node,
382 &root_stable_tree);
383 next_item->address |= NODE_FLAG;
384 } else {
385 rb_erase(&rmap_item->node, &root_stable_tree);
386 ksm_kernel_pages_allocated--;
387 }
388 } else {
389 struct rmap_item *prev_item = rmap_item->prev;
390
391 BUG_ON(prev_item->next != rmap_item);
392 prev_item->next = next_item;
393 if (next_item) {
394 BUG_ON(next_item->prev != rmap_item);
395 next_item->prev = rmap_item->prev;
396 }
397 }
398
399 rmap_item->next = NULL;
400 ksm_pages_shared--;
401
402 } else if (rmap_item->address & NODE_FLAG) {
403 unsigned char age;
404 /*
405 * ksm_thread can and must skip the rb_erase, because
406 * root_unstable_tree was already reset to RB_ROOT.
407 * But __ksm_exit has to be careful: do the rb_erase
408 * if it's interrupting a scan, and this rmap_item was
409 * inserted by this scan rather than left from before.
410 *
411 * Because of the case in which remove_mm_from_lists
412 * increments seqnr before removing rmaps, unstable_nr
413 * may even be 2 behind seqnr, but should never be
414 * further behind. Yes, I did have trouble with this!
415 */
416 age = (unsigned char)(ksm_scan.seqnr - rmap_item->address);
417 BUG_ON(age > 2);
418 if (!age)
419 rb_erase(&rmap_item->node, &root_unstable_tree);
420 }
421
422 rmap_item->address &= PAGE_MASK;
423
424 cond_resched(); /* we're called from many long loops */
425}
426
427static void remove_all_slot_rmap_items(struct mm_slot *mm_slot)
428{
429 struct rmap_item *rmap_item, *node;
430
431 list_for_each_entry_safe(rmap_item, node, &mm_slot->rmap_list, link) {
432 remove_rmap_item_from_tree(rmap_item);
433 list_del(&rmap_item->link);
434 free_rmap_item(rmap_item);
435 }
436}
437
438static void remove_trailing_rmap_items(struct mm_slot *mm_slot,
439 struct list_head *cur)
440{
441 struct rmap_item *rmap_item;
442
443 while (cur != &mm_slot->rmap_list) {
444 rmap_item = list_entry(cur, struct rmap_item, link);
445 cur = cur->next;
446 remove_rmap_item_from_tree(rmap_item);
447 list_del(&rmap_item->link);
448 free_rmap_item(rmap_item);
449 }
450}
451
452/*
453 * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather
454 * than check every pte of a given vma, the locking doesn't quite work for
455 * that - an rmap_item is assigned to the stable tree after inserting ksm
456 * page and upping mmap_sem. Nor does it fit with the way we skip dup'ing
457 * rmap_items from parent to child at fork time (so as not to waste time
458 * if exit comes before the next scan reaches it).
459 */
460static void unmerge_ksm_pages(struct vm_area_struct *vma,
461 unsigned long start, unsigned long end)
462{
463 unsigned long addr;
464
465 for (addr = start; addr < end; addr += PAGE_SIZE)
466 break_ksm(vma, addr);
467}
468
469static void unmerge_and_remove_all_rmap_items(void)
470{
471 struct mm_slot *mm_slot;
472 struct mm_struct *mm;
473 struct vm_area_struct *vma;
474
475 list_for_each_entry(mm_slot, &ksm_mm_head.mm_list, mm_list) {
476 mm = mm_slot->mm;
477 down_read(&mm->mmap_sem);
478 for (vma = mm->mmap; vma; vma = vma->vm_next) {
479 if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
480 continue;
481 unmerge_ksm_pages(vma, vma->vm_start, vma->vm_end);
482 }
483 remove_all_slot_rmap_items(mm_slot);
484 up_read(&mm->mmap_sem);
485 }
486
487 spin_lock(&ksm_mmlist_lock);
488 if (ksm_scan.mm_slot != &ksm_mm_head) {
489 ksm_scan.mm_slot = &ksm_mm_head;
490 ksm_scan.seqnr++;
491 }
492 spin_unlock(&ksm_mmlist_lock);
493}
494
495static void remove_mm_from_lists(struct mm_struct *mm)
496{
497 struct mm_slot *mm_slot;
498
499 spin_lock(&ksm_mmlist_lock);
500 mm_slot = get_mm_slot(mm);
501
502 /*
503 * This mm_slot is always at the scanning cursor when we're
504 * called from scan_get_next_rmap_item; but it's a special
505 * case when we're called from __ksm_exit.
506 */
507 if (ksm_scan.mm_slot == mm_slot) {
508 ksm_scan.mm_slot = list_entry(
509 mm_slot->mm_list.next, struct mm_slot, mm_list);
510 ksm_scan.address = 0;
511 ksm_scan.rmap_item = list_entry(
512 &ksm_scan.mm_slot->rmap_list, struct rmap_item, link);
513 if (ksm_scan.mm_slot == &ksm_mm_head)
514 ksm_scan.seqnr++;
515 }
516
517 hlist_del(&mm_slot->link);
518 list_del(&mm_slot->mm_list);
519 spin_unlock(&ksm_mmlist_lock);
520
521 remove_all_slot_rmap_items(mm_slot);
522 free_mm_slot(mm_slot);
523 clear_bit(MMF_VM_MERGEABLE, &mm->flags);
524}
525
526static u32 calc_checksum(struct page *page)
527{
528 u32 checksum;
529 void *addr = kmap_atomic(page, KM_USER0);
530 checksum = jhash2(addr, PAGE_SIZE / 4, 17);
531 kunmap_atomic(addr, KM_USER0);
532 return checksum;
533}
534
535static int memcmp_pages(struct page *page1, struct page *page2)
536{
537 char *addr1, *addr2;
538 int ret;
539
540 addr1 = kmap_atomic(page1, KM_USER0);
541 addr2 = kmap_atomic(page2, KM_USER1);
542 ret = memcmp(addr1, addr2, PAGE_SIZE);
543 kunmap_atomic(addr2, KM_USER1);
544 kunmap_atomic(addr1, KM_USER0);
545 return ret;
546}
547
548static inline int pages_identical(struct page *page1, struct page *page2)
549{
550 return !memcmp_pages(page1, page2);
551}
552
553static int write_protect_page(struct vm_area_struct *vma, struct page *page,
554 pte_t *orig_pte)
555{
556 struct mm_struct *mm = vma->vm_mm;
557 unsigned long addr;
558 pte_t *ptep;
559 spinlock_t *ptl;
560 int swapped;
561 int err = -EFAULT;
562
563 addr = page_address_in_vma(page, vma);
564 if (addr == -EFAULT)
565 goto out;
566
567 ptep = page_check_address(page, mm, addr, &ptl, 0);
568 if (!ptep)
569 goto out;
570
571 if (pte_write(*ptep)) {
572 pte_t entry;
573
574 swapped = PageSwapCache(page);
575 flush_cache_page(vma, addr, page_to_pfn(page));
576 /*
577 * Ok this is tricky, when get_user_pages_fast() run it doesnt
578 * take any lock, therefore the check that we are going to make
579 * with the pagecount against the mapcount is racey and
580 * O_DIRECT can happen right after the check.
581 * So we clear the pte and flush the tlb before the check
582 * this assure us that no O_DIRECT can happen after the check
583 * or in the middle of the check.
584 */
585 entry = ptep_clear_flush(vma, addr, ptep);
586 /*
587 * Check that no O_DIRECT or similar I/O is in progress on the
588 * page
589 */
590 if ((page_mapcount(page) + 2 + swapped) != page_count(page)) {
591 set_pte_at_notify(mm, addr, ptep, entry);
592 goto out_unlock;
593 }
594 entry = pte_wrprotect(entry);
595 set_pte_at_notify(mm, addr, ptep, entry);
596 }
597 *orig_pte = *ptep;
598 err = 0;
599
600out_unlock:
601 pte_unmap_unlock(ptep, ptl);
602out:
603 return err;
604}
605
606/**
607 * replace_page - replace page in vma by new ksm page
608 * @vma: vma that holds the pte pointing to oldpage
609 * @oldpage: the page we are replacing by newpage
610 * @newpage: the ksm page we replace oldpage by
611 * @orig_pte: the original value of the pte
612 *
613 * Returns 0 on success, -EFAULT on failure.
614 */
615static int replace_page(struct vm_area_struct *vma, struct page *oldpage,
616 struct page *newpage, pte_t orig_pte)
617{
618 struct mm_struct *mm = vma->vm_mm;
619 pgd_t *pgd;
620 pud_t *pud;
621 pmd_t *pmd;
622 pte_t *ptep;
623 spinlock_t *ptl;
624 unsigned long addr;
625 pgprot_t prot;
626 int err = -EFAULT;
627
628 prot = vm_get_page_prot(vma->vm_flags & ~VM_WRITE);
629
630 addr = page_address_in_vma(oldpage, vma);
631 if (addr == -EFAULT)
632 goto out;
633
634 pgd = pgd_offset(mm, addr);
635 if (!pgd_present(*pgd))
636 goto out;
637
638 pud = pud_offset(pgd, addr);
639 if (!pud_present(*pud))
640 goto out;
641
642 pmd = pmd_offset(pud, addr);
643 if (!pmd_present(*pmd))
644 goto out;
645
646 ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
647 if (!pte_same(*ptep, orig_pte)) {
648 pte_unmap_unlock(ptep, ptl);
649 goto out;
650 }
651
652 get_page(newpage);
653 page_add_ksm_rmap(newpage);
654
655 flush_cache_page(vma, addr, pte_pfn(*ptep));
656 ptep_clear_flush(vma, addr, ptep);
657 set_pte_at_notify(mm, addr, ptep, mk_pte(newpage, prot));
658
659 page_remove_rmap(oldpage);
660 put_page(oldpage);
661
662 pte_unmap_unlock(ptep, ptl);
663 err = 0;
664out:
665 return err;
666}
667
668/*
669 * try_to_merge_one_page - take two pages and merge them into one
670 * @vma: the vma that hold the pte pointing into oldpage
671 * @oldpage: the page that we want to replace with newpage
672 * @newpage: the page that we want to map instead of oldpage
673 *
674 * Note:
675 * oldpage should be a PageAnon page, while newpage should be a PageKsm page,
676 * or a newly allocated kernel page which page_add_ksm_rmap will make PageKsm.
677 *
678 * This function returns 0 if the pages were merged, -EFAULT otherwise.
679 */
680static int try_to_merge_one_page(struct vm_area_struct *vma,
681 struct page *oldpage,
682 struct page *newpage)
683{
684 pte_t orig_pte = __pte(0);
685 int err = -EFAULT;
686
687 if (!(vma->vm_flags & VM_MERGEABLE))
688 goto out;
689
690 if (!PageAnon(oldpage))
691 goto out;
692
693 get_page(newpage);
694 get_page(oldpage);
695
696 /*
697 * We need the page lock to read a stable PageSwapCache in
698 * write_protect_page(). We use trylock_page() instead of
699 * lock_page() because we don't want to wait here - we
700 * prefer to continue scanning and merging different pages,
701 * then come back to this page when it is unlocked.
702 */
703 if (!trylock_page(oldpage))
704 goto out_putpage;
705 /*
706 * If this anonymous page is mapped only here, its pte may need
707 * to be write-protected. If it's mapped elsewhere, all of its
708 * ptes are necessarily already write-protected. But in either
709 * case, we need to lock and check page_count is not raised.
710 */
711 if (write_protect_page(vma, oldpage, &orig_pte)) {
712 unlock_page(oldpage);
713 goto out_putpage;
714 }
715 unlock_page(oldpage);
716
717 if (pages_identical(oldpage, newpage))
718 err = replace_page(vma, oldpage, newpage, orig_pte);
719
720out_putpage:
721 put_page(oldpage);
722 put_page(newpage);
723out:
724 return err;
725}
726
727/*
728 * try_to_merge_two_pages - take two identical pages and prepare them
729 * to be merged into one page.
730 *
731 * This function returns 0 if we successfully mapped two identical pages
732 * into one page, -EFAULT otherwise.
733 *
734 * Note that this function allocates a new kernel page: if one of the pages
735 * is already a ksm page, try_to_merge_with_ksm_page should be used.
736 */
737static int try_to_merge_two_pages(struct mm_struct *mm1, unsigned long addr1,
738 struct page *page1, struct mm_struct *mm2,
739 unsigned long addr2, struct page *page2)
740{
741 struct vm_area_struct *vma;
742 struct page *kpage;
743 int err = -EFAULT;
744
745 /*
746 * The number of nodes in the stable tree
747 * is the number of kernel pages that we hold.
748 */
749 if (ksm_max_kernel_pages &&
750 ksm_max_kernel_pages <= ksm_kernel_pages_allocated)
751 return err;
752
753 kpage = alloc_page(GFP_HIGHUSER);
754 if (!kpage)
755 return err;
756
757 down_read(&mm1->mmap_sem);
758 vma = find_vma(mm1, addr1);
759 if (!vma || vma->vm_start > addr1) {
760 put_page(kpage);
761 up_read(&mm1->mmap_sem);
762 return err;
763 }
764
765 copy_user_highpage(kpage, page1, addr1, vma);
766 err = try_to_merge_one_page(vma, page1, kpage);
767 up_read(&mm1->mmap_sem);
768
769 if (!err) {
770 down_read(&mm2->mmap_sem);
771 vma = find_vma(mm2, addr2);
772 if (!vma || vma->vm_start > addr2) {
773 put_page(kpage);
774 up_read(&mm2->mmap_sem);
775 break_cow(mm1, addr1);
776 return -EFAULT;
777 }
778
779 err = try_to_merge_one_page(vma, page2, kpage);
780 up_read(&mm2->mmap_sem);
781
782 /*
783 * If the second try_to_merge_one_page failed, we have a
784 * ksm page with just one pte pointing to it, so break it.
785 */
786 if (err)
787 break_cow(mm1, addr1);
788 else
789 ksm_pages_shared += 2;
790 }
791
792 put_page(kpage);
793 return err;
794}
795
796/*
797 * try_to_merge_with_ksm_page - like try_to_merge_two_pages,
798 * but no new kernel page is allocated: kpage must already be a ksm page.
799 */
800static int try_to_merge_with_ksm_page(struct mm_struct *mm1,
801 unsigned long addr1,
802 struct page *page1,
803 struct page *kpage)
804{
805 struct vm_area_struct *vma;
806 int err = -EFAULT;
807
808 down_read(&mm1->mmap_sem);
809 vma = find_vma(mm1, addr1);
810 if (!vma || vma->vm_start > addr1) {
811 up_read(&mm1->mmap_sem);
812 return err;
813 }
814
815 err = try_to_merge_one_page(vma, page1, kpage);
816 up_read(&mm1->mmap_sem);
817
818 if (!err)
819 ksm_pages_shared++;
820
821 return err;
822}
823
824/*
825 * stable_tree_search - search page inside the stable tree
826 * @page: the page that we are searching identical pages to.
827 * @page2: pointer into identical page that we are holding inside the stable
828 * tree that we have found.
829 * @rmap_item: the reverse mapping item
830 *
831 * This function checks if there is a page inside the stable tree
832 * with identical content to the page that we are scanning right now.
833 *
834 * This function return rmap_item pointer to the identical item if found,
835 * NULL otherwise.
836 */
837static struct rmap_item *stable_tree_search(struct page *page,
838 struct page **page2,
839 struct rmap_item *rmap_item)
840{
841 struct rb_node *node = root_stable_tree.rb_node;
842
843 while (node) {
844 struct rmap_item *tree_rmap_item, *next_rmap_item;
845 int ret;
846
847 tree_rmap_item = rb_entry(node, struct rmap_item, node);
848 while (tree_rmap_item) {
849 BUG_ON(!in_stable_tree(tree_rmap_item));
850 cond_resched();
851 page2[0] = get_ksm_page(tree_rmap_item);
852 if (page2[0])
853 break;
854 next_rmap_item = tree_rmap_item->next;
855 remove_rmap_item_from_tree(tree_rmap_item);
856 tree_rmap_item = next_rmap_item;
857 }
858 if (!tree_rmap_item)
859 return NULL;
860
861 ret = memcmp_pages(page, page2[0]);
862
863 if (ret < 0) {
864 put_page(page2[0]);
865 node = node->rb_left;
866 } else if (ret > 0) {
867 put_page(page2[0]);
868 node = node->rb_right;
869 } else {
870 return tree_rmap_item;
871 }
872 }
873
874 return NULL;
875}
876
877/*
878 * stable_tree_insert - insert rmap_item pointing to new ksm page
879 * into the stable tree.
880 *
881 * @page: the page that we are searching identical page to inside the stable
882 * tree.
883 * @rmap_item: pointer to the reverse mapping item.
884 *
885 * This function returns rmap_item if success, NULL otherwise.
886 */
887static struct rmap_item *stable_tree_insert(struct page *page,
888 struct rmap_item *rmap_item)
889{
890 struct rb_node **new = &root_stable_tree.rb_node;
891 struct rb_node *parent = NULL;
892
893 while (*new) {
894 struct rmap_item *tree_rmap_item, *next_rmap_item;
895 struct page *tree_page;
896 int ret;
897
898 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
899 while (tree_rmap_item) {
900 BUG_ON(!in_stable_tree(tree_rmap_item));
901 cond_resched();
902 tree_page = get_ksm_page(tree_rmap_item);
903 if (tree_page)
904 break;
905 next_rmap_item = tree_rmap_item->next;
906 remove_rmap_item_from_tree(tree_rmap_item);
907 tree_rmap_item = next_rmap_item;
908 }
909 if (!tree_rmap_item)
910 return NULL;
911
912 ret = memcmp_pages(page, tree_page);
913 put_page(tree_page);
914
915 parent = *new;
916 if (ret < 0)
917 new = &parent->rb_left;
918 else if (ret > 0)
919 new = &parent->rb_right;
920 else {
921 /*
922 * It is not a bug that stable_tree_search() didn't
923 * find this node: because at that time our page was
924 * not yet write-protected, so may have changed since.
925 */
926 return NULL;
927 }
928 }
929
930 ksm_kernel_pages_allocated++;
931
932 rmap_item->address |= NODE_FLAG | STABLE_FLAG;
933 rmap_item->next = NULL;
934 rb_link_node(&rmap_item->node, parent, new);
935 rb_insert_color(&rmap_item->node, &root_stable_tree);
936
937 return rmap_item;
938}
939
940/*
941 * unstable_tree_search_insert - search and insert items into the unstable tree.
942 *
943 * @page: the page that we are going to search for identical page or to insert
944 * into the unstable tree
945 * @page2: pointer into identical page that was found inside the unstable tree
946 * @rmap_item: the reverse mapping item of page
947 *
948 * This function searches for a page in the unstable tree identical to the
949 * page currently being scanned; and if no identical page is found in the
950 * tree, we insert rmap_item as a new object into the unstable tree.
951 *
952 * This function returns pointer to rmap_item found to be identical
953 * to the currently scanned page, NULL otherwise.
954 *
955 * This function does both searching and inserting, because they share
956 * the same walking algorithm in an rbtree.
957 */
958static struct rmap_item *unstable_tree_search_insert(struct page *page,
959 struct page **page2,
960 struct rmap_item *rmap_item)
961{
962 struct rb_node **new = &root_unstable_tree.rb_node;
963 struct rb_node *parent = NULL;
964
965 while (*new) {
966 struct rmap_item *tree_rmap_item;
967 int ret;
968
969 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
970 page2[0] = get_mergeable_page(tree_rmap_item);
971 if (!page2[0])
972 return NULL;
973
974 /*
975 * Don't substitute an unswappable ksm page
976 * just for one good swappable forked page.
977 */
978 if (page == page2[0]) {
979 put_page(page2[0]);
980 return NULL;
981 }
982
983 ret = memcmp_pages(page, page2[0]);
984
985 parent = *new;
986 if (ret < 0) {
987 put_page(page2[0]);
988 new = &parent->rb_left;
989 } else if (ret > 0) {
990 put_page(page2[0]);
991 new = &parent->rb_right;
992 } else {
993 return tree_rmap_item;
994 }
995 }
996
997 rmap_item->address |= NODE_FLAG;
998 rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK);
999 rb_link_node(&rmap_item->node, parent, new);
1000 rb_insert_color(&rmap_item->node, &root_unstable_tree);
1001
1002 return NULL;
1003}
1004
1005/*
1006 * stable_tree_append - add another rmap_item to the linked list of
1007 * rmap_items hanging off a given node of the stable tree, all sharing
1008 * the same ksm page.
1009 */
1010static void stable_tree_append(struct rmap_item *rmap_item,
1011 struct rmap_item *tree_rmap_item)
1012{
1013 rmap_item->next = tree_rmap_item->next;
1014 rmap_item->prev = tree_rmap_item;
1015
1016 if (tree_rmap_item->next)
1017 tree_rmap_item->next->prev = rmap_item;
1018
1019 tree_rmap_item->next = rmap_item;
1020 rmap_item->address |= STABLE_FLAG;
1021}
1022
1023/*
1024 * cmp_and_merge_page - take a page computes its hash value and check if there
1025 * is similar hash value to different page,
1026 * in case we find that there is similar hash to different page we call to
1027 * try_to_merge_two_pages().
1028 *
1029 * @page: the page that we are searching identical page to.
1030 * @rmap_item: the reverse mapping into the virtual address of this page
1031 */
1032static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
1033{
1034 struct page *page2[1];
1035 struct rmap_item *tree_rmap_item;
1036 unsigned int checksum;
1037 int err;
1038
1039 if (in_stable_tree(rmap_item))
1040 remove_rmap_item_from_tree(rmap_item);
1041
1042 /* We first start with searching the page inside the stable tree */
1043 tree_rmap_item = stable_tree_search(page, page2, rmap_item);
1044 if (tree_rmap_item) {
1045 if (page == page2[0]) { /* forked */
1046 ksm_pages_shared++;
1047 err = 0;
1048 } else
1049 err = try_to_merge_with_ksm_page(rmap_item->mm,
1050 rmap_item->address,
1051 page, page2[0]);
1052 put_page(page2[0]);
1053
1054 if (!err) {
1055 /*
1056 * The page was successfully merged:
1057 * add its rmap_item to the stable tree.
1058 */
1059 stable_tree_append(rmap_item, tree_rmap_item);
1060 }
1061 return;
1062 }
1063
1064 /*
1065 * A ksm page might have got here by fork, but its other
1066 * references have already been removed from the stable tree.
1067 */
1068 if (PageKsm(page))
1069 break_cow(rmap_item->mm, rmap_item->address);
1070
1071 /*
1072 * In case the hash value of the page was changed from the last time we
1073 * have calculated it, this page to be changed frequely, therefore we
1074 * don't want to insert it to the unstable tree, and we don't want to
1075 * waste our time to search if there is something identical to it there.
1076 */
1077 checksum = calc_checksum(page);
1078 if (rmap_item->oldchecksum != checksum) {
1079 rmap_item->oldchecksum = checksum;
1080 return;
1081 }
1082
1083 tree_rmap_item = unstable_tree_search_insert(page, page2, rmap_item);
1084 if (tree_rmap_item) {
1085 err = try_to_merge_two_pages(rmap_item->mm,
1086 rmap_item->address, page,
1087 tree_rmap_item->mm,
1088 tree_rmap_item->address, page2[0]);
1089 /*
1090 * As soon as we merge this page, we want to remove the
1091 * rmap_item of the page we have merged with from the unstable
1092 * tree, and insert it instead as new node in the stable tree.
1093 */
1094 if (!err) {
1095 rb_erase(&tree_rmap_item->node, &root_unstable_tree);
1096 tree_rmap_item->address &= ~NODE_FLAG;
1097 /*
1098 * If we fail to insert the page into the stable tree,
1099 * we will have 2 virtual addresses that are pointing
1100 * to a ksm page left outside the stable tree,
1101 * in which case we need to break_cow on both.
1102 */
1103 if (stable_tree_insert(page2[0], tree_rmap_item))
1104 stable_tree_append(rmap_item, tree_rmap_item);
1105 else {
1106 break_cow(tree_rmap_item->mm,
1107 tree_rmap_item->address);
1108 break_cow(rmap_item->mm, rmap_item->address);
1109 ksm_pages_shared -= 2;
1110 }
1111 }
1112
1113 put_page(page2[0]);
1114 }
1115}
1116
1117static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot,
1118 struct list_head *cur,
1119 unsigned long addr)
1120{
1121 struct rmap_item *rmap_item;
1122
1123 while (cur != &mm_slot->rmap_list) {
1124 rmap_item = list_entry(cur, struct rmap_item, link);
1125 if ((rmap_item->address & PAGE_MASK) == addr) {
1126 if (!in_stable_tree(rmap_item))
1127 remove_rmap_item_from_tree(rmap_item);
1128 return rmap_item;
1129 }
1130 if (rmap_item->address > addr)
1131 break;
1132 cur = cur->next;
1133 remove_rmap_item_from_tree(rmap_item);
1134 list_del(&rmap_item->link);
1135 free_rmap_item(rmap_item);
1136 }
1137
1138 rmap_item = alloc_rmap_item();
1139 if (rmap_item) {
1140 /* It has already been zeroed */
1141 rmap_item->mm = mm_slot->mm;
1142 rmap_item->address = addr;
1143 list_add_tail(&rmap_item->link, cur);
1144 }
1145 return rmap_item;
1146}
1147
1148static struct rmap_item *scan_get_next_rmap_item(struct page **page)
1149{
1150 struct mm_struct *mm;
1151 struct mm_slot *slot;
1152 struct vm_area_struct *vma;
1153 struct rmap_item *rmap_item;
1154
1155 if (list_empty(&ksm_mm_head.mm_list))
1156 return NULL;
1157
1158 slot = ksm_scan.mm_slot;
1159 if (slot == &ksm_mm_head) {
1160 root_unstable_tree = RB_ROOT;
1161
1162 spin_lock(&ksm_mmlist_lock);
1163 slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list);
1164 ksm_scan.mm_slot = slot;
1165 spin_unlock(&ksm_mmlist_lock);
1166next_mm:
1167 ksm_scan.address = 0;
1168 ksm_scan.rmap_item = list_entry(&slot->rmap_list,
1169 struct rmap_item, link);
1170 }
1171
1172 mm = slot->mm;
1173 down_read(&mm->mmap_sem);
1174 for (vma = find_vma(mm, ksm_scan.address); vma; vma = vma->vm_next) {
1175 if (!(vma->vm_flags & VM_MERGEABLE))
1176 continue;
1177 if (ksm_scan.address < vma->vm_start)
1178 ksm_scan.address = vma->vm_start;
1179 if (!vma->anon_vma)
1180 ksm_scan.address = vma->vm_end;
1181
1182 while (ksm_scan.address < vma->vm_end) {
1183 *page = follow_page(vma, ksm_scan.address, FOLL_GET);
1184 if (*page && PageAnon(*page)) {
1185 flush_anon_page(vma, *page, ksm_scan.address);
1186 flush_dcache_page(*page);
1187 rmap_item = get_next_rmap_item(slot,
1188 ksm_scan.rmap_item->link.next,
1189 ksm_scan.address);
1190 if (rmap_item) {
1191 ksm_scan.rmap_item = rmap_item;
1192 ksm_scan.address += PAGE_SIZE;
1193 } else
1194 put_page(*page);
1195 up_read(&mm->mmap_sem);
1196 return rmap_item;
1197 }
1198 if (*page)
1199 put_page(*page);
1200 ksm_scan.address += PAGE_SIZE;
1201 cond_resched();
1202 }
1203 }
1204
1205 if (!ksm_scan.address) {
1206 /*
1207 * We've completed a full scan of all vmas, holding mmap_sem
1208 * throughout, and found no VM_MERGEABLE: so do the same as
1209 * __ksm_exit does to remove this mm from all our lists now.
1210 */
1211 remove_mm_from_lists(mm);
1212 up_read(&mm->mmap_sem);
1213 slot = ksm_scan.mm_slot;
1214 if (slot != &ksm_mm_head)
1215 goto next_mm;
1216 return NULL;
1217 }
1218
1219 /*
1220 * Nuke all the rmap_items that are above this current rmap:
1221 * because there were no VM_MERGEABLE vmas with such addresses.
1222 */
1223 remove_trailing_rmap_items(slot, ksm_scan.rmap_item->link.next);
1224 up_read(&mm->mmap_sem);
1225
1226 spin_lock(&ksm_mmlist_lock);
1227 slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list);
1228 ksm_scan.mm_slot = slot;
1229 spin_unlock(&ksm_mmlist_lock);
1230
1231 /* Repeat until we've completed scanning the whole list */
1232 if (slot != &ksm_mm_head)
1233 goto next_mm;
1234
1235 /*
1236 * Bump seqnr here rather than at top, so that __ksm_exit
1237 * can skip rb_erase on unstable tree until we run again.
1238 */
1239 ksm_scan.seqnr++;
1240 return NULL;
1241}
1242
1243/**
1244 * ksm_do_scan - the ksm scanner main worker function.
1245 * @scan_npages - number of pages we want to scan before we return.
1246 */
1247static void ksm_do_scan(unsigned int scan_npages)
1248{
1249 struct rmap_item *rmap_item;
1250 struct page *page;
1251
1252 while (scan_npages--) {
1253 cond_resched();
1254 rmap_item = scan_get_next_rmap_item(&page);
1255 if (!rmap_item)
1256 return;
1257 if (!PageKsm(page) || !in_stable_tree(rmap_item))
1258 cmp_and_merge_page(page, rmap_item);
1259 put_page(page);
1260 }
1261}
1262
1263static int ksm_scan_thread(void *nothing)
1264{
1265 set_user_nice(current, 0);
1266
1267 while (!kthread_should_stop()) {
1268 if (ksm_run & KSM_RUN_MERGE) {
1269 mutex_lock(&ksm_thread_mutex);
1270 ksm_do_scan(ksm_thread_pages_to_scan);
1271 mutex_unlock(&ksm_thread_mutex);
1272 schedule_timeout_interruptible(
1273 msecs_to_jiffies(ksm_thread_sleep_millisecs));
1274 } else {
1275 wait_event_interruptible(ksm_thread_wait,
1276 (ksm_run & KSM_RUN_MERGE) ||
1277 kthread_should_stop());
1278 }
1279 }
1280 return 0;
1281}
1282
9int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 1283int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
10 unsigned long end, int advice, unsigned long *vm_flags) 1284 unsigned long end, int advice, unsigned long *vm_flags)
11{ 1285{
@@ -33,7 +1307,8 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
33 if (!(*vm_flags & VM_MERGEABLE)) 1307 if (!(*vm_flags & VM_MERGEABLE))
34 return 0; /* just ignore the advice */ 1308 return 0; /* just ignore the advice */
35 1309
36 /* Unmerge any merged pages here */ 1310 if (vma->anon_vma)
1311 unmerge_ksm_pages(vma, start, end);
37 1312
38 *vm_flags &= ~VM_MERGEABLE; 1313 *vm_flags &= ~VM_MERGEABLE;
39 break; 1314 break;
@@ -44,13 +1319,217 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
44 1319
45int __ksm_enter(struct mm_struct *mm) 1320int __ksm_enter(struct mm_struct *mm)
46{ 1321{
47 /* Allocate a structure to track mm and link it into KSM's list */ 1322 struct mm_slot *mm_slot = alloc_mm_slot();
1323 if (!mm_slot)
1324 return -ENOMEM;
1325
1326 spin_lock(&ksm_mmlist_lock);
1327 insert_to_mm_slots_hash(mm, mm_slot);
1328 /*
1329 * Insert just behind the scanning cursor, to let the area settle
1330 * down a little; when fork is followed by immediate exec, we don't
1331 * want ksmd to waste time setting up and tearing down an rmap_list.
1332 */
1333 list_add_tail(&mm_slot->mm_list, &ksm_scan.mm_slot->mm_list);
1334 spin_unlock(&ksm_mmlist_lock);
1335
48 set_bit(MMF_VM_MERGEABLE, &mm->flags); 1336 set_bit(MMF_VM_MERGEABLE, &mm->flags);
49 return 0; 1337 return 0;
50} 1338}
51 1339
52void __ksm_exit(struct mm_struct *mm) 1340void __ksm_exit(struct mm_struct *mm)
53{ 1341{
54 /* Unlink and free all KSM's structures which track this mm */ 1342 /*
55 clear_bit(MMF_VM_MERGEABLE, &mm->flags); 1343 * This process is exiting: doesn't hold and doesn't need mmap_sem;
1344 * but we do need to exclude ksmd and other exiters while we modify
1345 * the various lists and trees.
1346 */
1347 mutex_lock(&ksm_thread_mutex);
1348 remove_mm_from_lists(mm);
1349 mutex_unlock(&ksm_thread_mutex);
1350}
1351
1352#define KSM_ATTR_RO(_name) \
1353 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
1354#define KSM_ATTR(_name) \
1355 static struct kobj_attribute _name##_attr = \
1356 __ATTR(_name, 0644, _name##_show, _name##_store)
1357
1358static ssize_t sleep_millisecs_show(struct kobject *kobj,
1359 struct kobj_attribute *attr, char *buf)
1360{
1361 return sprintf(buf, "%u\n", ksm_thread_sleep_millisecs);
1362}
1363
1364static ssize_t sleep_millisecs_store(struct kobject *kobj,
1365 struct kobj_attribute *attr,
1366 const char *buf, size_t count)
1367{
1368 unsigned long msecs;
1369 int err;
1370
1371 err = strict_strtoul(buf, 10, &msecs);
1372 if (err || msecs > UINT_MAX)
1373 return -EINVAL;
1374
1375 ksm_thread_sleep_millisecs = msecs;
1376
1377 return count;
1378}
1379KSM_ATTR(sleep_millisecs);
1380
1381static ssize_t pages_to_scan_show(struct kobject *kobj,
1382 struct kobj_attribute *attr, char *buf)
1383{
1384 return sprintf(buf, "%u\n", ksm_thread_pages_to_scan);
1385}
1386
1387static ssize_t pages_to_scan_store(struct kobject *kobj,
1388 struct kobj_attribute *attr,
1389 const char *buf, size_t count)
1390{
1391 int err;
1392 unsigned long nr_pages;
1393
1394 err = strict_strtoul(buf, 10, &nr_pages);
1395 if (err || nr_pages > UINT_MAX)
1396 return -EINVAL;
1397
1398 ksm_thread_pages_to_scan = nr_pages;
1399
1400 return count;
1401}
1402KSM_ATTR(pages_to_scan);
1403
1404static ssize_t run_show(struct kobject *kobj, struct kobj_attribute *attr,
1405 char *buf)
1406{
1407 return sprintf(buf, "%u\n", ksm_run);
1408}
1409
1410static ssize_t run_store(struct kobject *kobj, struct kobj_attribute *attr,
1411 const char *buf, size_t count)
1412{
1413 int err;
1414 unsigned long flags;
1415
1416 err = strict_strtoul(buf, 10, &flags);
1417 if (err || flags > UINT_MAX)
1418 return -EINVAL;
1419 if (flags > KSM_RUN_UNMERGE)
1420 return -EINVAL;
1421
1422 /*
1423 * KSM_RUN_MERGE sets ksmd running, and 0 stops it running.
1424 * KSM_RUN_UNMERGE stops it running and unmerges all rmap_items,
1425 * breaking COW to free the kernel_pages_allocated (but leaves
1426 * mm_slots on the list for when ksmd may be set running again).
1427 */
1428
1429 mutex_lock(&ksm_thread_mutex);
1430 if (ksm_run != flags) {
1431 ksm_run = flags;
1432 if (flags & KSM_RUN_UNMERGE)
1433 unmerge_and_remove_all_rmap_items();
1434 }
1435 mutex_unlock(&ksm_thread_mutex);
1436
1437 if (flags & KSM_RUN_MERGE)
1438 wake_up_interruptible(&ksm_thread_wait);
1439
1440 return count;
1441}
1442KSM_ATTR(run);
1443
1444static ssize_t pages_shared_show(struct kobject *kobj,
1445 struct kobj_attribute *attr, char *buf)
1446{
1447 return sprintf(buf, "%lu\n",
1448 ksm_pages_shared - ksm_kernel_pages_allocated);
1449}
1450KSM_ATTR_RO(pages_shared);
1451
1452static ssize_t kernel_pages_allocated_show(struct kobject *kobj,
1453 struct kobj_attribute *attr,
1454 char *buf)
1455{
1456 return sprintf(buf, "%lu\n", ksm_kernel_pages_allocated);
1457}
1458KSM_ATTR_RO(kernel_pages_allocated);
1459
1460static ssize_t max_kernel_pages_store(struct kobject *kobj,
1461 struct kobj_attribute *attr,
1462 const char *buf, size_t count)
1463{
1464 int err;
1465 unsigned long nr_pages;
1466
1467 err = strict_strtoul(buf, 10, &nr_pages);
1468 if (err)
1469 return -EINVAL;
1470
1471 ksm_max_kernel_pages = nr_pages;
1472
1473 return count;
1474}
1475
1476static ssize_t max_kernel_pages_show(struct kobject *kobj,
1477 struct kobj_attribute *attr, char *buf)
1478{
1479 return sprintf(buf, "%lu\n", ksm_max_kernel_pages);
1480}
1481KSM_ATTR(max_kernel_pages);
1482
1483static struct attribute *ksm_attrs[] = {
1484 &sleep_millisecs_attr.attr,
1485 &pages_to_scan_attr.attr,
1486 &run_attr.attr,
1487 &pages_shared_attr.attr,
1488 &kernel_pages_allocated_attr.attr,
1489 &max_kernel_pages_attr.attr,
1490 NULL,
1491};
1492
1493static struct attribute_group ksm_attr_group = {
1494 .attrs = ksm_attrs,
1495 .name = "ksm",
1496};
1497
1498static int __init ksm_init(void)
1499{
1500 struct task_struct *ksm_thread;
1501 int err;
1502
1503 err = ksm_slab_init();
1504 if (err)
1505 goto out;
1506
1507 err = mm_slots_hash_init();
1508 if (err)
1509 goto out_free1;
1510
1511 ksm_thread = kthread_run(ksm_scan_thread, NULL, "ksmd");
1512 if (IS_ERR(ksm_thread)) {
1513 printk(KERN_ERR "ksm: creating kthread failed\n");
1514 err = PTR_ERR(ksm_thread);
1515 goto out_free2;
1516 }
1517
1518 err = sysfs_create_group(mm_kobj, &ksm_attr_group);
1519 if (err) {
1520 printk(KERN_ERR "ksm: register sysfs failed\n");
1521 goto out_free3;
1522 }
1523
1524 return 0;
1525
1526out_free3:
1527 kthread_stop(ksm_thread);
1528out_free2:
1529 mm_slots_hash_free();
1530out_free1:
1531 ksm_slab_free();
1532out:
1533 return err;
56} 1534}
1535module_init(ksm_init)
generated by cgit v1.2.2 (git 2.25.0) at 2025-03-31 18:20:52 -0400