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Christoph Lameterb20a3502006-03-22 00:09:12 -08001/*
2 * Memory Migration functionality - linux/mm/migration.c
3 *
4 * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
5 *
6 * Page migration was first developed in the context of the memory hotplug
7 * project. The main authors of the migration code are:
8 *
9 * IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
10 * Hirokazu Takahashi <taka@valinux.co.jp>
11 * Dave Hansen <haveblue@us.ibm.com>
Christoph Lametercde53532008-07-04 09:59:22 -070012 * Christoph Lameter
Christoph Lameterb20a3502006-03-22 00:09:12 -080013 */
14
15#include <linux/migrate.h>
16#include <linux/module.h>
17#include <linux/swap.h>
Christoph Lameter06972122006-06-23 02:03:35 -070018#include <linux/swapops.h>
Christoph Lameterb20a3502006-03-22 00:09:12 -080019#include <linux/pagemap.h>
Christoph Lametere23ca002006-04-10 22:52:57 -070020#include <linux/buffer_head.h>
Christoph Lameterb20a3502006-03-22 00:09:12 -080021#include <linux/mm_inline.h>
Pavel Emelyanovb4888932007-10-18 23:40:14 -070022#include <linux/nsproxy.h>
Christoph Lameterb20a3502006-03-22 00:09:12 -080023#include <linux/pagevec.h>
24#include <linux/rmap.h>
25#include <linux/topology.h>
26#include <linux/cpu.h>
27#include <linux/cpuset.h>
Christoph Lameter04e62a22006-06-23 02:03:38 -070028#include <linux/writeback.h>
Christoph Lameter742755a2006-06-23 02:03:55 -070029#include <linux/mempolicy.h>
30#include <linux/vmalloc.h>
David Quigley86c3a762006-06-23 02:04:02 -070031#include <linux/security.h>
Balbir Singh8a9f3cc2008-02-07 00:13:53 -080032#include <linux/memcontrol.h>
Adrian Bunk4f5ca262008-07-23 21:27:02 -070033#include <linux/syscalls.h>
Christoph Lameterb20a3502006-03-22 00:09:12 -080034
35#include "internal.h"
36
Christoph Lameterb20a3502006-03-22 00:09:12 -080037#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
38
39/*
Christoph Lameter742755a2006-06-23 02:03:55 -070040 * migrate_prep() needs to be called before we start compiling a list of pages
41 * to be migrated using isolate_lru_page().
Christoph Lameterb20a3502006-03-22 00:09:12 -080042 */
43int migrate_prep(void)
44{
Christoph Lameterb20a3502006-03-22 00:09:12 -080045 /*
46 * Clear the LRU lists so pages can be isolated.
47 * Note that pages may be moved off the LRU after we have
48 * drained them. Those pages will fail to migrate like other
49 * pages that may be busy.
50 */
51 lru_add_drain_all();
52
53 return 0;
54}
55
Christoph Lameterb20a3502006-03-22 00:09:12 -080056/*
Lee Schermerhorn894bc312008-10-18 20:26:39 -070057 * Add isolated pages on the list back to the LRU under page lock
58 * to avoid leaking evictable pages back onto unevictable list.
Christoph Lameterb20a3502006-03-22 00:09:12 -080059 *
60 * returns the number of pages put back.
61 */
62int putback_lru_pages(struct list_head *l)
63{
64 struct page *page;
65 struct page *page2;
66 int count = 0;
67
68 list_for_each_entry_safe(page, page2, l, lru) {
Christoph Lametere24f0b82006-06-23 02:03:51 -070069 list_del(&page->lru);
Lee Schermerhorn894bc312008-10-18 20:26:39 -070070 putback_lru_page(page);
Christoph Lameterb20a3502006-03-22 00:09:12 -080071 count++;
72 }
73 return count;
74}
75
Christoph Lameter06972122006-06-23 02:03:35 -070076/*
77 * Restore a potential migration pte to a working pte entry
78 */
Christoph Lameter04e62a22006-06-23 02:03:38 -070079static void remove_migration_pte(struct vm_area_struct *vma,
Christoph Lameter06972122006-06-23 02:03:35 -070080 struct page *old, struct page *new)
81{
82 struct mm_struct *mm = vma->vm_mm;
83 swp_entry_t entry;
84 pgd_t *pgd;
85 pud_t *pud;
86 pmd_t *pmd;
87 pte_t *ptep, pte;
88 spinlock_t *ptl;
Christoph Lameter04e62a22006-06-23 02:03:38 -070089 unsigned long addr = page_address_in_vma(new, vma);
90
91 if (addr == -EFAULT)
92 return;
Christoph Lameter06972122006-06-23 02:03:35 -070093
94 pgd = pgd_offset(mm, addr);
95 if (!pgd_present(*pgd))
96 return;
97
98 pud = pud_offset(pgd, addr);
99 if (!pud_present(*pud))
100 return;
101
102 pmd = pmd_offset(pud, addr);
103 if (!pmd_present(*pmd))
104 return;
105
106 ptep = pte_offset_map(pmd, addr);
107
108 if (!is_swap_pte(*ptep)) {
109 pte_unmap(ptep);
110 return;
111 }
112
113 ptl = pte_lockptr(mm, pmd);
114 spin_lock(ptl);
115 pte = *ptep;
116 if (!is_swap_pte(pte))
117 goto out;
118
119 entry = pte_to_swp_entry(pte);
120
121 if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)
122 goto out;
123
Hugh Dickins98837c72008-03-04 14:29:06 -0800124 /*
125 * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge.
126 * Failure is not an option here: we're now expected to remove every
127 * migration pte, and will cause crashes otherwise. Normally this
128 * is not an issue: mem_cgroup_prepare_migration bumped up the old
129 * page_cgroup count for safety, that's now attached to the new page,
130 * so this charge should just be another incrementation of the count,
131 * to keep in balance with rmap.c's mem_cgroup_uncharging. But if
132 * there's been a force_empty, those reference counts may no longer
133 * be reliable, and this charge can actually fail: oh well, we don't
134 * make the situation any worse by proceeding as if it had succeeded.
135 */
136 mem_cgroup_charge(new, mm, GFP_ATOMIC);
137
Christoph Lameter06972122006-06-23 02:03:35 -0700138 get_page(new);
139 pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
140 if (is_write_migration_entry(entry))
141 pte = pte_mkwrite(pte);
KAMEZAWA Hiroyuki97ee0522007-10-16 01:25:43 -0700142 flush_cache_page(vma, addr, pte_pfn(pte));
Christoph Lameter06972122006-06-23 02:03:35 -0700143 set_pte_at(mm, addr, ptep, pte);
Christoph Lameter04e62a22006-06-23 02:03:38 -0700144
145 if (PageAnon(new))
146 page_add_anon_rmap(new, vma, addr);
147 else
148 page_add_file_rmap(new);
149
150 /* No need to invalidate - it was non-present before */
151 update_mmu_cache(vma, addr, pte);
Christoph Lameter04e62a22006-06-23 02:03:38 -0700152
Christoph Lameter06972122006-06-23 02:03:35 -0700153out:
154 pte_unmap_unlock(ptep, ptl);
155}
156
157/*
Christoph Lameter04e62a22006-06-23 02:03:38 -0700158 * Note that remove_file_migration_ptes will only work on regular mappings,
159 * Nonlinear mappings do not use migration entries.
160 */
161static void remove_file_migration_ptes(struct page *old, struct page *new)
162{
163 struct vm_area_struct *vma;
164 struct address_space *mapping = page_mapping(new);
165 struct prio_tree_iter iter;
166 pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
167
168 if (!mapping)
169 return;
170
171 spin_lock(&mapping->i_mmap_lock);
172
173 vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
174 remove_migration_pte(vma, old, new);
175
176 spin_unlock(&mapping->i_mmap_lock);
177}
178
179/*
Christoph Lameter06972122006-06-23 02:03:35 -0700180 * Must hold mmap_sem lock on at least one of the vmas containing
181 * the page so that the anon_vma cannot vanish.
182 */
Christoph Lameter04e62a22006-06-23 02:03:38 -0700183static void remove_anon_migration_ptes(struct page *old, struct page *new)
Christoph Lameter06972122006-06-23 02:03:35 -0700184{
185 struct anon_vma *anon_vma;
186 struct vm_area_struct *vma;
187 unsigned long mapping;
188
189 mapping = (unsigned long)new->mapping;
190
191 if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
192 return;
193
194 /*
195 * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
196 */
197 anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
198 spin_lock(&anon_vma->lock);
199
200 list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
Christoph Lameter04e62a22006-06-23 02:03:38 -0700201 remove_migration_pte(vma, old, new);
Christoph Lameter06972122006-06-23 02:03:35 -0700202
203 spin_unlock(&anon_vma->lock);
204}
205
206/*
Christoph Lameter04e62a22006-06-23 02:03:38 -0700207 * Get rid of all migration entries and replace them by
208 * references to the indicated page.
209 */
210static void remove_migration_ptes(struct page *old, struct page *new)
211{
212 if (PageAnon(new))
213 remove_anon_migration_ptes(old, new);
214 else
215 remove_file_migration_ptes(old, new);
216}
217
218/*
Christoph Lameter06972122006-06-23 02:03:35 -0700219 * Something used the pte of a page under migration. We need to
220 * get to the page and wait until migration is finished.
221 * When we return from this function the fault will be retried.
222 *
223 * This function is called from do_swap_page().
224 */
225void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
226 unsigned long address)
227{
228 pte_t *ptep, pte;
229 spinlock_t *ptl;
230 swp_entry_t entry;
231 struct page *page;
232
233 ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
234 pte = *ptep;
235 if (!is_swap_pte(pte))
236 goto out;
237
238 entry = pte_to_swp_entry(pte);
239 if (!is_migration_entry(entry))
240 goto out;
241
242 page = migration_entry_to_page(entry);
243
Nick Piggine2867812008-07-25 19:45:30 -0700244 /*
245 * Once radix-tree replacement of page migration started, page_count
246 * *must* be zero. And, we don't want to call wait_on_page_locked()
247 * against a page without get_page().
248 * So, we use get_page_unless_zero(), here. Even failed, page fault
249 * will occur again.
250 */
251 if (!get_page_unless_zero(page))
252 goto out;
Christoph Lameter06972122006-06-23 02:03:35 -0700253 pte_unmap_unlock(ptep, ptl);
254 wait_on_page_locked(page);
255 put_page(page);
256 return;
257out:
258 pte_unmap_unlock(ptep, ptl);
259}
260
Christoph Lameterb20a3502006-03-22 00:09:12 -0800261/*
Christoph Lameterc3fcf8a2006-06-23 02:03:32 -0700262 * Replace the page in the mapping.
Christoph Lameter5b5c7122006-06-23 02:03:29 -0700263 *
264 * The number of remaining references must be:
265 * 1 for anonymous pages without a mapping
266 * 2 for pages with a mapping
267 * 3 for pages with a mapping and PagePrivate set.
Christoph Lameterb20a3502006-03-22 00:09:12 -0800268 */
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700269static int migrate_page_move_mapping(struct address_space *mapping,
270 struct page *newpage, struct page *page)
Christoph Lameterb20a3502006-03-22 00:09:12 -0800271{
Nick Piggine2867812008-07-25 19:45:30 -0700272 int expected_count;
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800273 void **pslot;
Christoph Lameterb20a3502006-03-22 00:09:12 -0800274
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700275 if (!mapping) {
Christoph Lameter0e8c7d02007-04-23 14:41:09 -0700276 /* Anonymous page without mapping */
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700277 if (page_count(page) != 1)
278 return -EAGAIN;
279 return 0;
280 }
281
Nick Piggin19fd6232008-07-25 19:45:32 -0700282 spin_lock_irq(&mapping->tree_lock);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800283
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800284 pslot = radix_tree_lookup_slot(&mapping->page_tree,
285 page_index(page));
Christoph Lameterb20a3502006-03-22 00:09:12 -0800286
Nick Piggine2867812008-07-25 19:45:30 -0700287 expected_count = 2 + !!PagePrivate(page);
288 if (page_count(page) != expected_count ||
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800289 (struct page *)radix_tree_deref_slot(pslot) != page) {
Nick Piggin19fd6232008-07-25 19:45:32 -0700290 spin_unlock_irq(&mapping->tree_lock);
Christoph Lametere23ca002006-04-10 22:52:57 -0700291 return -EAGAIN;
Christoph Lameterb20a3502006-03-22 00:09:12 -0800292 }
293
Nick Piggine2867812008-07-25 19:45:30 -0700294 if (!page_freeze_refs(page, expected_count)) {
Nick Piggin19fd6232008-07-25 19:45:32 -0700295 spin_unlock_irq(&mapping->tree_lock);
Nick Piggine2867812008-07-25 19:45:30 -0700296 return -EAGAIN;
297 }
298
Christoph Lameterb20a3502006-03-22 00:09:12 -0800299 /*
300 * Now we know that no one else is looking at the page.
Christoph Lameterb20a3502006-03-22 00:09:12 -0800301 */
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800302 get_page(newpage); /* add cache reference */
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700303#ifdef CONFIG_SWAP
Christoph Lameterb20a3502006-03-22 00:09:12 -0800304 if (PageSwapCache(page)) {
305 SetPageSwapCache(newpage);
306 set_page_private(newpage, page_private(page));
307 }
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700308#endif
Christoph Lameterb20a3502006-03-22 00:09:12 -0800309
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800310 radix_tree_replace_slot(pslot, newpage);
311
Nick Piggine2867812008-07-25 19:45:30 -0700312 page_unfreeze_refs(page, expected_count);
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800313 /*
314 * Drop cache reference from old page.
315 * We know this isn't the last reference.
316 */
Christoph Lameterb20a3502006-03-22 00:09:12 -0800317 __put_page(page);
Nick Piggin7cf9c2c2006-12-06 20:33:44 -0800318
Christoph Lameter0e8c7d02007-04-23 14:41:09 -0700319 /*
320 * If moved to a different zone then also account
321 * the page for that zone. Other VM counters will be
322 * taken care of when we establish references to the
323 * new page and drop references to the old page.
324 *
325 * Note that anonymous pages are accounted for
326 * via NR_FILE_PAGES and NR_ANON_PAGES if they
327 * are mapped to swap space.
328 */
329 __dec_zone_page_state(page, NR_FILE_PAGES);
330 __inc_zone_page_state(newpage, NR_FILE_PAGES);
331
Nick Piggin19fd6232008-07-25 19:45:32 -0700332 spin_unlock_irq(&mapping->tree_lock);
333 if (!PageSwapCache(newpage))
KAMEZAWA Hiroyuki69029cd2008-07-25 01:47:14 -0700334 mem_cgroup_uncharge_cache_page(page);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800335
336 return 0;
337}
Christoph Lameterb20a3502006-03-22 00:09:12 -0800338
339/*
340 * Copy the page to its new location
341 */
Christoph Lametere7340f72006-06-23 02:03:29 -0700342static void migrate_page_copy(struct page *newpage, struct page *page)
Christoph Lameterb20a3502006-03-22 00:09:12 -0800343{
344 copy_highpage(newpage, page);
345
346 if (PageError(page))
347 SetPageError(newpage);
348 if (PageReferenced(page))
349 SetPageReferenced(newpage);
350 if (PageUptodate(page))
351 SetPageUptodate(newpage);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700352 if (TestClearPageActive(page)) {
353 VM_BUG_ON(PageUnevictable(page));
Christoph Lameterb20a3502006-03-22 00:09:12 -0800354 SetPageActive(newpage);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700355 } else
356 unevictable_migrate_page(newpage, page);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800357 if (PageChecked(page))
358 SetPageChecked(newpage);
359 if (PageMappedToDisk(page))
360 SetPageMappedToDisk(newpage);
361
362 if (PageDirty(page)) {
363 clear_page_dirty_for_io(page);
Nick Piggin3a902c52008-04-30 00:55:16 -0700364 /*
365 * Want to mark the page and the radix tree as dirty, and
366 * redo the accounting that clear_page_dirty_for_io undid,
367 * but we can't use set_page_dirty because that function
368 * is actually a signal that all of the page has become dirty.
369 * Wheras only part of our page may be dirty.
370 */
371 __set_page_dirty_nobuffers(newpage);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800372 }
373
Nick Pigginb291f002008-10-18 20:26:44 -0700374 mlock_migrate_page(newpage, page);
375
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700376#ifdef CONFIG_SWAP
Christoph Lameterb20a3502006-03-22 00:09:12 -0800377 ClearPageSwapCache(page);
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700378#endif
Christoph Lameterb20a3502006-03-22 00:09:12 -0800379 ClearPagePrivate(page);
380 set_page_private(page, 0);
381 page->mapping = NULL;
382
383 /*
384 * If any waiters have accumulated on the new page then
385 * wake them up.
386 */
387 if (PageWriteback(newpage))
388 end_page_writeback(newpage);
389}
Christoph Lameterb20a3502006-03-22 00:09:12 -0800390
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700391/************************************************************
392 * Migration functions
393 ***********************************************************/
394
395/* Always fail migration. Used for mappings that are not movable */
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700396int fail_migrate_page(struct address_space *mapping,
397 struct page *newpage, struct page *page)
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700398{
399 return -EIO;
400}
401EXPORT_SYMBOL(fail_migrate_page);
402
Christoph Lameterb20a3502006-03-22 00:09:12 -0800403/*
404 * Common logic to directly migrate a single page suitable for
405 * pages that do not use PagePrivate.
406 *
407 * Pages are locked upon entry and exit.
408 */
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700409int migrate_page(struct address_space *mapping,
410 struct page *newpage, struct page *page)
Christoph Lameterb20a3502006-03-22 00:09:12 -0800411{
412 int rc;
413
414 BUG_ON(PageWriteback(page)); /* Writeback must be complete */
415
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700416 rc = migrate_page_move_mapping(mapping, newpage, page);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800417
418 if (rc)
419 return rc;
420
421 migrate_page_copy(newpage, page);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800422 return 0;
423}
424EXPORT_SYMBOL(migrate_page);
425
David Howells93614012006-09-30 20:45:40 +0200426#ifdef CONFIG_BLOCK
Christoph Lameterb20a3502006-03-22 00:09:12 -0800427/*
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700428 * Migration function for pages with buffers. This function can only be used
429 * if the underlying filesystem guarantees that no other references to "page"
430 * exist.
431 */
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700432int buffer_migrate_page(struct address_space *mapping,
433 struct page *newpage, struct page *page)
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700434{
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700435 struct buffer_head *bh, *head;
436 int rc;
437
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700438 if (!page_has_buffers(page))
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700439 return migrate_page(mapping, newpage, page);
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700440
441 head = page_buffers(page);
442
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700443 rc = migrate_page_move_mapping(mapping, newpage, page);
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700444
445 if (rc)
446 return rc;
447
448 bh = head;
449 do {
450 get_bh(bh);
451 lock_buffer(bh);
452 bh = bh->b_this_page;
453
454 } while (bh != head);
455
456 ClearPagePrivate(page);
457 set_page_private(newpage, page_private(page));
458 set_page_private(page, 0);
459 put_page(page);
460 get_page(newpage);
461
462 bh = head;
463 do {
464 set_bh_page(bh, newpage, bh_offset(bh));
465 bh = bh->b_this_page;
466
467 } while (bh != head);
468
469 SetPagePrivate(newpage);
470
471 migrate_page_copy(newpage, page);
472
473 bh = head;
474 do {
475 unlock_buffer(bh);
476 put_bh(bh);
477 bh = bh->b_this_page;
478
479 } while (bh != head);
480
481 return 0;
482}
483EXPORT_SYMBOL(buffer_migrate_page);
David Howells93614012006-09-30 20:45:40 +0200484#endif
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700485
Christoph Lameter04e62a22006-06-23 02:03:38 -0700486/*
487 * Writeback a page to clean the dirty state
488 */
489static int writeout(struct address_space *mapping, struct page *page)
490{
491 struct writeback_control wbc = {
492 .sync_mode = WB_SYNC_NONE,
493 .nr_to_write = 1,
494 .range_start = 0,
495 .range_end = LLONG_MAX,
496 .nonblocking = 1,
497 .for_reclaim = 1
498 };
499 int rc;
500
501 if (!mapping->a_ops->writepage)
502 /* No write method for the address space */
503 return -EINVAL;
504
505 if (!clear_page_dirty_for_io(page))
506 /* Someone else already triggered a write */
507 return -EAGAIN;
508
509 /*
510 * A dirty page may imply that the underlying filesystem has
511 * the page on some queue. So the page must be clean for
512 * migration. Writeout may mean we loose the lock and the
513 * page state is no longer what we checked for earlier.
514 * At this point we know that the migration attempt cannot
515 * be successful.
516 */
517 remove_migration_ptes(page, page);
518
519 rc = mapping->a_ops->writepage(page, &wbc);
520 if (rc < 0)
521 /* I/O Error writing */
522 return -EIO;
523
524 if (rc != AOP_WRITEPAGE_ACTIVATE)
525 /* unlocked. Relock */
526 lock_page(page);
527
528 return -EAGAIN;
529}
530
531/*
532 * Default handling if a filesystem does not provide a migration function.
533 */
Christoph Lameter8351a6e2006-06-23 02:03:33 -0700534static int fallback_migrate_page(struct address_space *mapping,
535 struct page *newpage, struct page *page)
536{
Christoph Lameter04e62a22006-06-23 02:03:38 -0700537 if (PageDirty(page))
538 return writeout(mapping, page);
Christoph Lameter8351a6e2006-06-23 02:03:33 -0700539
540 /*
541 * Buffers may be managed in a filesystem specific way.
542 * We must have no buffers or drop them.
543 */
David Howellsb398f6b2006-08-29 19:05:58 +0100544 if (PagePrivate(page) &&
Christoph Lameter8351a6e2006-06-23 02:03:33 -0700545 !try_to_release_page(page, GFP_KERNEL))
546 return -EAGAIN;
547
548 return migrate_page(mapping, newpage, page);
549}
550
Christoph Lameter1d8b85c2006-06-23 02:03:28 -0700551/*
Christoph Lametere24f0b82006-06-23 02:03:51 -0700552 * Move a page to a newly allocated page
553 * The page is locked and all ptes have been successfully removed.
554 *
555 * The new page will have replaced the old page if this function
556 * is successful.
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700557 *
558 * Return value:
559 * < 0 - error code
560 * == 0 - success
Christoph Lametere24f0b82006-06-23 02:03:51 -0700561 */
562static int move_to_new_page(struct page *newpage, struct page *page)
563{
564 struct address_space *mapping;
565 int rc;
566
567 /*
568 * Block others from accessing the page when we get around to
569 * establishing additional references. We are the only one
570 * holding a reference to the new page at this point.
571 */
Nick Piggin529ae9a2008-08-02 12:01:03 +0200572 if (!trylock_page(newpage))
Christoph Lametere24f0b82006-06-23 02:03:51 -0700573 BUG();
574
575 /* Prepare mapping for the new page.*/
576 newpage->index = page->index;
577 newpage->mapping = page->mapping;
Rik van Rielb2e18532008-10-18 20:26:30 -0700578 if (PageSwapBacked(page))
579 SetPageSwapBacked(newpage);
Christoph Lametere24f0b82006-06-23 02:03:51 -0700580
581 mapping = page_mapping(page);
582 if (!mapping)
583 rc = migrate_page(mapping, newpage, page);
584 else if (mapping->a_ops->migratepage)
585 /*
586 * Most pages have a mapping and most filesystems
587 * should provide a migration function. Anonymous
588 * pages are part of swap space which also has its
589 * own migration function. This is the most common
590 * path for page migration.
591 */
592 rc = mapping->a_ops->migratepage(mapping,
593 newpage, page);
594 else
595 rc = fallback_migrate_page(mapping, newpage, page);
596
KAMEZAWA Hiroyukiae41be32008-02-07 00:14:10 -0800597 if (!rc) {
Christoph Lametere24f0b82006-06-23 02:03:51 -0700598 remove_migration_ptes(page, newpage);
KAMEZAWA Hiroyukiae41be32008-02-07 00:14:10 -0800599 } else
Christoph Lametere24f0b82006-06-23 02:03:51 -0700600 newpage->mapping = NULL;
601
602 unlock_page(newpage);
603
604 return rc;
605}
606
607/*
608 * Obtain the lock on page, remove all ptes and migrate the page
609 * to the newly allocated page in newpage.
610 */
Christoph Lameter95a402c2006-06-23 02:03:53 -0700611static int unmap_and_move(new_page_t get_new_page, unsigned long private,
612 struct page *page, int force)
Christoph Lametere24f0b82006-06-23 02:03:51 -0700613{
614 int rc = 0;
Christoph Lameter742755a2006-06-23 02:03:55 -0700615 int *result = NULL;
616 struct page *newpage = get_new_page(page, private, &result);
KAMEZAWA Hiroyuki989f89c2007-08-30 23:56:21 -0700617 int rcu_locked = 0;
KAMEZAWA Hiroyukiae41be32008-02-07 00:14:10 -0800618 int charge = 0;
Christoph Lameter95a402c2006-06-23 02:03:53 -0700619
620 if (!newpage)
621 return -ENOMEM;
Christoph Lametere24f0b82006-06-23 02:03:51 -0700622
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700623 if (page_count(page) == 1) {
Christoph Lametere24f0b82006-06-23 02:03:51 -0700624 /* page was freed from under us. So we are done. */
Christoph Lameter95a402c2006-06-23 02:03:53 -0700625 goto move_newpage;
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700626 }
Christoph Lametere24f0b82006-06-23 02:03:51 -0700627
KAMEZAWA Hiroyukie8589cc2008-07-25 01:47:10 -0700628 charge = mem_cgroup_prepare_migration(page, newpage);
629 if (charge == -ENOMEM) {
630 rc = -ENOMEM;
631 goto move_newpage;
632 }
633 /* prepare cgroup just returns 0 or -ENOMEM */
634 BUG_ON(charge);
635
Christoph Lametere24f0b82006-06-23 02:03:51 -0700636 rc = -EAGAIN;
Nick Piggin529ae9a2008-08-02 12:01:03 +0200637 if (!trylock_page(page)) {
Christoph Lametere24f0b82006-06-23 02:03:51 -0700638 if (!force)
Christoph Lameter95a402c2006-06-23 02:03:53 -0700639 goto move_newpage;
Christoph Lametere24f0b82006-06-23 02:03:51 -0700640 lock_page(page);
641 }
642
643 if (PageWriteback(page)) {
644 if (!force)
645 goto unlock;
646 wait_on_page_writeback(page);
647 }
Christoph Lametere24f0b82006-06-23 02:03:51 -0700648 /*
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700649 * By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
650 * we cannot notice that anon_vma is freed while we migrates a page.
651 * This rcu_read_lock() delays freeing anon_vma pointer until the end
652 * of migration. File cache pages are no problem because of page_lock()
KAMEZAWA Hiroyuki989f89c2007-08-30 23:56:21 -0700653 * File Caches may use write_page() or lock_page() in migration, then,
654 * just care Anon page here.
Christoph Lametere24f0b82006-06-23 02:03:51 -0700655 */
KAMEZAWA Hiroyuki989f89c2007-08-30 23:56:21 -0700656 if (PageAnon(page)) {
657 rcu_read_lock();
658 rcu_locked = 1;
659 }
Shaohua Li62e1c552008-02-04 22:29:33 -0800660
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700661 /*
Shaohua Li62e1c552008-02-04 22:29:33 -0800662 * Corner case handling:
663 * 1. When a new swap-cache page is read into, it is added to the LRU
664 * and treated as swapcache but it has no rmap yet.
665 * Calling try_to_unmap() against a page->mapping==NULL page will
666 * trigger a BUG. So handle it here.
667 * 2. An orphaned page (see truncate_complete_page) might have
668 * fs-private metadata. The page can be picked up due to memory
669 * offlining. Everywhere else except page reclaim, the page is
670 * invisible to the vm, so the page can not be migrated. So try to
671 * free the metadata, so the page can be freed.
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700672 */
Shaohua Li62e1c552008-02-04 22:29:33 -0800673 if (!page->mapping) {
674 if (!PageAnon(page) && PagePrivate(page)) {
675 /*
676 * Go direct to try_to_free_buffers() here because
677 * a) that's what try_to_release_page() would do anyway
678 * b) we may be under rcu_read_lock() here, so we can't
679 * use GFP_KERNEL which is what try_to_release_page()
680 * needs to be effective.
681 */
682 try_to_free_buffers(page);
683 }
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700684 goto rcu_unlock;
Shaohua Li62e1c552008-02-04 22:29:33 -0800685 }
686
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700687 /* Establish migration ptes or remove ptes */
Christoph Lametere6a15302006-06-25 05:46:49 -0700688 try_to_unmap(page, 1);
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700689
Christoph Lametere6a15302006-06-25 05:46:49 -0700690 if (!page_mapped(page))
691 rc = move_to_new_page(newpage, page);
Christoph Lametere24f0b82006-06-23 02:03:51 -0700692
KAMEZAWA Hiroyukie8589cc2008-07-25 01:47:10 -0700693 if (rc)
Christoph Lametere24f0b82006-06-23 02:03:51 -0700694 remove_migration_ptes(page, page);
KAMEZAWA Hiroyukidc386d42007-07-26 10:41:07 -0700695rcu_unlock:
KAMEZAWA Hiroyuki989f89c2007-08-30 23:56:21 -0700696 if (rcu_locked)
697 rcu_read_unlock();
Christoph Lametere6a15302006-06-25 05:46:49 -0700698
Christoph Lametere24f0b82006-06-23 02:03:51 -0700699unlock:
700 unlock_page(page);
Christoph Lameter95a402c2006-06-23 02:03:53 -0700701
Christoph Lametere24f0b82006-06-23 02:03:51 -0700702 if (rc != -EAGAIN) {
Christoph Lameteraaa994b2006-06-23 02:03:52 -0700703 /*
704 * A page that has been migrated has all references
705 * removed and will be freed. A page that has not been
706 * migrated will have kepts its references and be
707 * restored.
708 */
709 list_del(&page->lru);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700710 putback_lru_page(page);
Christoph Lametere24f0b82006-06-23 02:03:51 -0700711 }
Christoph Lameter95a402c2006-06-23 02:03:53 -0700712
713move_newpage:
KAMEZAWA Hiroyukie8589cc2008-07-25 01:47:10 -0700714 if (!charge)
715 mem_cgroup_end_migration(newpage);
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700716
Christoph Lameter95a402c2006-06-23 02:03:53 -0700717 /*
718 * Move the new page to the LRU. If migration was not successful
719 * then this will free the page.
720 */
Lee Schermerhorn894bc312008-10-18 20:26:39 -0700721 putback_lru_page(newpage);
722
Christoph Lameter742755a2006-06-23 02:03:55 -0700723 if (result) {
724 if (rc)
725 *result = rc;
726 else
727 *result = page_to_nid(newpage);
728 }
Christoph Lametere24f0b82006-06-23 02:03:51 -0700729 return rc;
730}
731
732/*
Christoph Lameterb20a3502006-03-22 00:09:12 -0800733 * migrate_pages
734 *
Christoph Lameter95a402c2006-06-23 02:03:53 -0700735 * The function takes one list of pages to migrate and a function
736 * that determines from the page to be migrated and the private data
737 * the target of the move and allocates the page.
Christoph Lameterb20a3502006-03-22 00:09:12 -0800738 *
739 * The function returns after 10 attempts or if no pages
740 * are movable anymore because to has become empty
Christoph Lameteraaa994b2006-06-23 02:03:52 -0700741 * or no retryable pages exist anymore. All pages will be
Gabriel Craciunescue9534b32007-10-20 02:13:26 +0200742 * returned to the LRU or freed.
Christoph Lameterb20a3502006-03-22 00:09:12 -0800743 *
Christoph Lameter95a402c2006-06-23 02:03:53 -0700744 * Return: Number of pages not migrated or error code.
Christoph Lameterb20a3502006-03-22 00:09:12 -0800745 */
Christoph Lameter95a402c2006-06-23 02:03:53 -0700746int migrate_pages(struct list_head *from,
747 new_page_t get_new_page, unsigned long private)
Christoph Lameterb20a3502006-03-22 00:09:12 -0800748{
Christoph Lametere24f0b82006-06-23 02:03:51 -0700749 int retry = 1;
Christoph Lameterb20a3502006-03-22 00:09:12 -0800750 int nr_failed = 0;
751 int pass = 0;
752 struct page *page;
753 struct page *page2;
754 int swapwrite = current->flags & PF_SWAPWRITE;
755 int rc;
756
757 if (!swapwrite)
758 current->flags |= PF_SWAPWRITE;
759
Christoph Lametere24f0b82006-06-23 02:03:51 -0700760 for(pass = 0; pass < 10 && retry; pass++) {
761 retry = 0;
Christoph Lameterb20a3502006-03-22 00:09:12 -0800762
Christoph Lametere24f0b82006-06-23 02:03:51 -0700763 list_for_each_entry_safe(page, page2, from, lru) {
Christoph Lametere24f0b82006-06-23 02:03:51 -0700764 cond_resched();
Christoph Lameterb20a3502006-03-22 00:09:12 -0800765
Christoph Lameter95a402c2006-06-23 02:03:53 -0700766 rc = unmap_and_move(get_new_page, private,
767 page, pass > 2);
Christoph Lameterb20a3502006-03-22 00:09:12 -0800768
Christoph Lametere24f0b82006-06-23 02:03:51 -0700769 switch(rc) {
Christoph Lameter95a402c2006-06-23 02:03:53 -0700770 case -ENOMEM:
771 goto out;
Christoph Lametere24f0b82006-06-23 02:03:51 -0700772 case -EAGAIN:
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700773 retry++;
Christoph Lametere24f0b82006-06-23 02:03:51 -0700774 break;
775 case 0:
Christoph Lametere24f0b82006-06-23 02:03:51 -0700776 break;
777 default:
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700778 /* Permanent failure */
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700779 nr_failed++;
Christoph Lametere24f0b82006-06-23 02:03:51 -0700780 break;
Christoph Lameter2d1db3b2006-06-23 02:03:33 -0700781 }
Christoph Lameterb20a3502006-03-22 00:09:12 -0800782 }
783 }
Christoph Lameter95a402c2006-06-23 02:03:53 -0700784 rc = 0;
785out:
Christoph Lameterb20a3502006-03-22 00:09:12 -0800786 if (!swapwrite)
787 current->flags &= ~PF_SWAPWRITE;
788
Christoph Lameteraaa994b2006-06-23 02:03:52 -0700789 putback_lru_pages(from);
Christoph Lameter95a402c2006-06-23 02:03:53 -0700790
791 if (rc)
792 return rc;
793
Christoph Lameterb20a3502006-03-22 00:09:12 -0800794 return nr_failed + retry;
795}
796
Christoph Lameter742755a2006-06-23 02:03:55 -0700797#ifdef CONFIG_NUMA
798/*
799 * Move a list of individual pages
800 */
801struct page_to_node {
802 unsigned long addr;
803 struct page *page;
804 int node;
805 int status;
806};
807
808static struct page *new_page_node(struct page *p, unsigned long private,
809 int **result)
810{
811 struct page_to_node *pm = (struct page_to_node *)private;
812
813 while (pm->node != MAX_NUMNODES && pm->page != p)
814 pm++;
815
816 if (pm->node == MAX_NUMNODES)
817 return NULL;
818
819 *result = &pm->status;
820
Mel Gorman769848c2007-07-17 04:03:05 -0700821 return alloc_pages_node(pm->node,
822 GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
Christoph Lameter742755a2006-06-23 02:03:55 -0700823}
824
825/*
826 * Move a set of pages as indicated in the pm array. The addr
827 * field must be set to the virtual address of the page to be moved
828 * and the node number must contain a valid target node.
829 */
830static int do_move_pages(struct mm_struct *mm, struct page_to_node *pm,
831 int migrate_all)
832{
833 int err;
834 struct page_to_node *pp;
835 LIST_HEAD(pagelist);
836
837 down_read(&mm->mmap_sem);
838
839 /*
840 * Build a list of pages to migrate
841 */
842 migrate_prep();
843 for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
844 struct vm_area_struct *vma;
845 struct page *page;
846
847 /*
848 * A valid page pointer that will not match any of the
849 * pages that will be moved.
850 */
851 pp->page = ZERO_PAGE(0);
852
853 err = -EFAULT;
854 vma = find_vma(mm, pp->addr);
Christoph Lameter0dc952d2007-03-05 00:30:33 -0800855 if (!vma || !vma_migratable(vma))
Christoph Lameter742755a2006-06-23 02:03:55 -0700856 goto set_status;
857
858 page = follow_page(vma, pp->addr, FOLL_GET);
Linus Torvalds89f5b7d2008-06-20 11:18:25 -0700859
860 err = PTR_ERR(page);
861 if (IS_ERR(page))
862 goto set_status;
863
Christoph Lameter742755a2006-06-23 02:03:55 -0700864 err = -ENOENT;
865 if (!page)
866 goto set_status;
867
868 if (PageReserved(page)) /* Check for zero page */
869 goto put_and_set;
870
871 pp->page = page;
872 err = page_to_nid(page);
873
874 if (err == pp->node)
875 /*
876 * Node already in the right place
877 */
878 goto put_and_set;
879
880 err = -EACCES;
881 if (page_mapcount(page) > 1 &&
882 !migrate_all)
883 goto put_and_set;
884
Nick Piggin62695a82008-10-18 20:26:09 -0700885 err = isolate_lru_page(page);
886 if (!err)
887 list_add_tail(&page->lru, &pagelist);
Christoph Lameter742755a2006-06-23 02:03:55 -0700888put_and_set:
889 /*
890 * Either remove the duplicate refcount from
891 * isolate_lru_page() or drop the page ref if it was
892 * not isolated.
893 */
894 put_page(page);
895set_status:
896 pp->status = err;
897 }
898
Brice Gogline78bbfa2008-10-18 20:27:15 -0700899 err = 0;
Christoph Lameter742755a2006-06-23 02:03:55 -0700900 if (!list_empty(&pagelist))
901 err = migrate_pages(&pagelist, new_page_node,
902 (unsigned long)pm);
Christoph Lameter742755a2006-06-23 02:03:55 -0700903
904 up_read(&mm->mmap_sem);
905 return err;
906}
907
908/*
909 * Determine the nodes of a list of pages. The addr in the pm array
910 * must have been set to the virtual address of which we want to determine
911 * the node number.
912 */
913static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm)
914{
915 down_read(&mm->mmap_sem);
916
917 for ( ; pm->node != MAX_NUMNODES; pm++) {
918 struct vm_area_struct *vma;
919 struct page *page;
920 int err;
921
922 err = -EFAULT;
923 vma = find_vma(mm, pm->addr);
924 if (!vma)
925 goto set_status;
926
927 page = follow_page(vma, pm->addr, 0);
Linus Torvalds89f5b7d2008-06-20 11:18:25 -0700928
929 err = PTR_ERR(page);
930 if (IS_ERR(page))
931 goto set_status;
932
Christoph Lameter742755a2006-06-23 02:03:55 -0700933 err = -ENOENT;
934 /* Use PageReserved to check for zero page */
935 if (!page || PageReserved(page))
936 goto set_status;
937
938 err = page_to_nid(page);
939set_status:
940 pm->status = err;
941 }
942
943 up_read(&mm->mmap_sem);
944 return 0;
945}
946
947/*
948 * Move a list of pages in the address space of the currently executing
949 * process.
950 */
951asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
952 const void __user * __user *pages,
953 const int __user *nodes,
954 int __user *status, int flags)
955{
956 int err = 0;
957 int i;
958 struct task_struct *task;
959 nodemask_t task_nodes;
960 struct mm_struct *mm;
961 struct page_to_node *pm = NULL;
962
963 /* Check flags */
964 if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
965 return -EINVAL;
966
967 if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
968 return -EPERM;
969
970 /* Find the mm_struct */
971 read_lock(&tasklist_lock);
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -0700972 task = pid ? find_task_by_vpid(pid) : current;
Christoph Lameter742755a2006-06-23 02:03:55 -0700973 if (!task) {
974 read_unlock(&tasklist_lock);
975 return -ESRCH;
976 }
977 mm = get_task_mm(task);
978 read_unlock(&tasklist_lock);
979
980 if (!mm)
981 return -EINVAL;
982
983 /*
984 * Check if this process has the right to modify the specified
985 * process. The right exists if the process has administrative
986 * capabilities, superuser privileges or the same
987 * userid as the target process.
988 */
989 if ((current->euid != task->suid) && (current->euid != task->uid) &&
990 (current->uid != task->suid) && (current->uid != task->uid) &&
991 !capable(CAP_SYS_NICE)) {
992 err = -EPERM;
993 goto out2;
994 }
995
David Quigley86c3a762006-06-23 02:04:02 -0700996 err = security_task_movememory(task);
997 if (err)
998 goto out2;
999
1000
Christoph Lameter742755a2006-06-23 02:03:55 -07001001 task_nodes = cpuset_mems_allowed(task);
1002
1003 /* Limit nr_pages so that the multiplication may not overflow */
1004 if (nr_pages >= ULONG_MAX / sizeof(struct page_to_node) - 1) {
1005 err = -E2BIG;
1006 goto out2;
1007 }
1008
1009 pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node));
1010 if (!pm) {
1011 err = -ENOMEM;
1012 goto out2;
1013 }
1014
1015 /*
1016 * Get parameters from user space and initialize the pm
1017 * array. Return various errors if the user did something wrong.
1018 */
1019 for (i = 0; i < nr_pages; i++) {
Al Viro9d966d42007-10-14 19:34:10 +01001020 const void __user *p;
Christoph Lameter742755a2006-06-23 02:03:55 -07001021
1022 err = -EFAULT;
1023 if (get_user(p, pages + i))
1024 goto out;
1025
1026 pm[i].addr = (unsigned long)p;
1027 if (nodes) {
1028 int node;
1029
1030 if (get_user(node, nodes + i))
1031 goto out;
1032
1033 err = -ENODEV;
Christoph Lameter56bbd652007-10-16 01:25:35 -07001034 if (!node_state(node, N_HIGH_MEMORY))
Christoph Lameter742755a2006-06-23 02:03:55 -07001035 goto out;
1036
1037 err = -EACCES;
1038 if (!node_isset(node, task_nodes))
1039 goto out;
1040
1041 pm[i].node = node;
Stephen Rothwell8ce08462006-11-02 22:07:28 -08001042 } else
1043 pm[i].node = 0; /* anything to not match MAX_NUMNODES */
Christoph Lameter742755a2006-06-23 02:03:55 -07001044 }
1045 /* End marker */
1046 pm[nr_pages].node = MAX_NUMNODES;
1047
1048 if (nodes)
1049 err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL);
1050 else
1051 err = do_pages_stat(mm, pm);
1052
1053 if (err >= 0)
1054 /* Return status information */
1055 for (i = 0; i < nr_pages; i++)
1056 if (put_user(pm[i].status, status + i))
1057 err = -EFAULT;
1058
1059out:
1060 vfree(pm);
1061out2:
1062 mmput(mm);
1063 return err;
1064}
Christoph Lameter742755a2006-06-23 02:03:55 -07001065
Christoph Lameter7b2259b2006-06-25 05:46:48 -07001066/*
1067 * Call migration functions in the vma_ops that may prepare
1068 * memory in a vm for migration. migration functions may perform
1069 * the migration for vmas that do not have an underlying page struct.
1070 */
1071int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
1072 const nodemask_t *from, unsigned long flags)
1073{
1074 struct vm_area_struct *vma;
1075 int err = 0;
1076
1077 for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) {
1078 if (vma->vm_ops && vma->vm_ops->migrate) {
1079 err = vma->vm_ops->migrate(vma, to, from, flags);
1080 if (err)
1081 break;
1082 }
1083 }
1084 return err;
1085}
Gerald Schaefer83d16742008-07-23 21:28:22 -07001086#endif