summaryrefslogtreecommitdiff
path: root/mm/memcontrol.c
blob: 904e9a9c223dd1c019c1478872326b6ba4a1fc01 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
/* memcontrol.c - Memory Controller
 *
 * Copyright IBM Corporation, 2007
 * Author Balbir Singh <balbir@linux.vnet.ibm.com>
 *
 * Copyright 2007 OpenVZ SWsoft Inc
 * Author: Pavel Emelianov <xemul@openvz.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/res_counter.h>
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/page-flags.h>
#include <linux/backing-dev.h>
#include <linux/bit_spinlock.h>
#include <linux/rcupdate.h>
#include <linux/swap.h>
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/seq_file.h>

#include <asm/uaccess.h>

struct cgroup_subsys mem_cgroup_subsys;
static const int MEM_CGROUP_RECLAIM_RETRIES = 5;

/*
 * Statistics for memory cgroup.
 */
enum mem_cgroup_stat_index {
	/*
	 * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
	 */
	MEM_CGROUP_STAT_CACHE, 	   /* # of pages charged as cache */
	MEM_CGROUP_STAT_RSS,	   /* # of pages charged as rss */

	MEM_CGROUP_STAT_NSTATS,
};

struct mem_cgroup_stat_cpu {
	s64 count[MEM_CGROUP_STAT_NSTATS];
} ____cacheline_aligned_in_smp;

struct mem_cgroup_stat {
	struct mem_cgroup_stat_cpu cpustat[NR_CPUS];
};

/*
 * For accounting under irq disable, no need for increment preempt count.
 */
static void __mem_cgroup_stat_add_safe(struct mem_cgroup_stat *stat,
		enum mem_cgroup_stat_index idx, int val)
{
	int cpu = smp_processor_id();
	stat->cpustat[cpu].count[idx] += val;
}

static s64 mem_cgroup_read_stat(struct mem_cgroup_stat *stat,
		enum mem_cgroup_stat_index idx)
{
	int cpu;
	s64 ret = 0;
	for_each_possible_cpu(cpu)
		ret += stat->cpustat[cpu].count[idx];
	return ret;
}

/*
 * The memory controller data structure. The memory controller controls both
 * page cache and RSS per cgroup. We would eventually like to provide
 * statistics based on the statistics developed by Rik Van Riel for clock-pro,
 * to help the administrator determine what knobs to tune.
 *
 * TODO: Add a water mark for the memory controller. Reclaim will begin when
 * we hit the water mark. May be even add a low water mark, such that
 * no reclaim occurs from a cgroup at it's low water mark, this is
 * a feature that will be implemented much later in the future.
 */
struct mem_cgroup {
	struct cgroup_subsys_state css;
	/*
	 * the counter to account for memory usage
	 */
	struct res_counter res;
	/*
	 * Per cgroup active and inactive list, similar to the
	 * per zone LRU lists.
	 * TODO: Consider making these lists per zone
	 */
	struct list_head active_list;
	struct list_head inactive_list;
	/*
	 * spin_lock to protect the per cgroup LRU
	 */
	spinlock_t lru_lock;
	unsigned long control_type;	/* control RSS or RSS+Pagecache */
	/*
	 * statistics.
	 */
	struct mem_cgroup_stat stat;
};

/*
 * We use the lower bit of the page->page_cgroup pointer as a bit spin
 * lock. We need to ensure that page->page_cgroup is atleast two
 * byte aligned (based on comments from Nick Piggin)
 */
#define PAGE_CGROUP_LOCK_BIT 	0x0
#define PAGE_CGROUP_LOCK 		(1 << PAGE_CGROUP_LOCK_BIT)

/*
 * A page_cgroup page is associated with every page descriptor. The
 * page_cgroup helps us identify information about the cgroup
 */
struct page_cgroup {
	struct list_head lru;		/* per cgroup LRU list */
	struct page *page;
	struct mem_cgroup *mem_cgroup;
	atomic_t ref_cnt;		/* Helpful when pages move b/w  */
					/* mapped and cached states     */
	int	 flags;
};
#define PAGE_CGROUP_FLAG_CACHE	(0x1)	/* charged as cache */
#define PAGE_CGROUP_FLAG_ACTIVE (0x2)	/* page is active in this cgroup */

enum {
	MEM_CGROUP_TYPE_UNSPEC = 0,
	MEM_CGROUP_TYPE_MAPPED,
	MEM_CGROUP_TYPE_CACHED,
	MEM_CGROUP_TYPE_ALL,
	MEM_CGROUP_TYPE_MAX,
};

enum charge_type {
	MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
	MEM_CGROUP_CHARGE_TYPE_MAPPED,
};

/*
 * Always modified under lru lock. Then, not necessary to preempt_disable()
 */
static void mem_cgroup_charge_statistics(struct mem_cgroup *mem, int flags,
					bool charge)
{
	int val = (charge)? 1 : -1;
	struct mem_cgroup_stat *stat = &mem->stat;
	VM_BUG_ON(!irqs_disabled());

	if (flags & PAGE_CGROUP_FLAG_CACHE)
		__mem_cgroup_stat_add_safe(stat,
					MEM_CGROUP_STAT_CACHE, val);
	else
		__mem_cgroup_stat_add_safe(stat, MEM_CGROUP_STAT_RSS, val);

}

static struct mem_cgroup init_mem_cgroup;

static inline
struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
{
	return container_of(cgroup_subsys_state(cont,
				mem_cgroup_subsys_id), struct mem_cgroup,
				css);
}

static inline
struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
{
	return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
				struct mem_cgroup, css);
}

void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p)
{
	struct mem_cgroup *mem;

	mem = mem_cgroup_from_task(p);
	css_get(&mem->css);
	mm->mem_cgroup = mem;
}

void mm_free_cgroup(struct mm_struct *mm)
{
	css_put(&mm->mem_cgroup->css);
}

static inline int page_cgroup_locked(struct page *page)
{
	return bit_spin_is_locked(PAGE_CGROUP_LOCK_BIT,
					&page->page_cgroup);
}

void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
{
	int locked;

	/*
	 * While resetting the page_cgroup we might not hold the
	 * page_cgroup lock. free_hot_cold_page() is an example
	 * of such a scenario
	 */
	if (pc)
		VM_BUG_ON(!page_cgroup_locked(page));
	locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
	page->page_cgroup = ((unsigned long)pc | locked);
}

struct page_cgroup *page_get_page_cgroup(struct page *page)
{
	return (struct page_cgroup *)
		(page->page_cgroup & ~PAGE_CGROUP_LOCK);
}

static void __always_inline lock_page_cgroup(struct page *page)
{
	bit_spin_lock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
	VM_BUG_ON(!page_cgroup_locked(page));
}

static void __always_inline unlock_page_cgroup(struct page *page)
{
	bit_spin_unlock(PAGE_CGROUP_LOCK_BIT, &page->page_cgroup);
}

/*
 * Tie new page_cgroup to struct page under lock_page_cgroup()
 * This can fail if the page has been tied to a page_cgroup.
 * If success, returns 0.
 */
static int page_cgroup_assign_new_page_cgroup(struct page *page,
						struct page_cgroup *pc)
{
	int ret = 0;

	lock_page_cgroup(page);
	if (!page_get_page_cgroup(page))
		page_assign_page_cgroup(page, pc);
	else /* A page is tied to other pc. */
		ret = 1;
	unlock_page_cgroup(page);
	return ret;
}

/*
 * Clear page->page_cgroup member under lock_page_cgroup().
 * If given "pc" value is different from one page->page_cgroup,
 * page->cgroup is not cleared.
 * Returns a value of page->page_cgroup at lock taken.
 * A can can detect failure of clearing by following
 *  clear_page_cgroup(page, pc) == pc
 */

static struct page_cgroup *clear_page_cgroup(struct page *page,
						struct page_cgroup *pc)
{
	struct page_cgroup *ret;
	/* lock and clear */
	lock_page_cgroup(page);
	ret = page_get_page_cgroup(page);
	if (likely(ret == pc))
		page_assign_page_cgroup(page, NULL);
	unlock_page_cgroup(page);
	return ret;
}

static void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
{
	if (active) {
		pc->flags |= PAGE_CGROUP_FLAG_ACTIVE;
		list_move(&pc->lru, &pc->mem_cgroup->active_list);
	} else {
		pc->flags &= ~PAGE_CGROUP_FLAG_ACTIVE;
		list_move(&pc->lru, &pc->mem_cgroup->inactive_list);
	}
}

int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
{
	int ret;

	task_lock(task);
	ret = task->mm && mm_cgroup(task->mm) == mem;
	task_unlock(task);
	return ret;
}

/*
 * This routine assumes that the appropriate zone's lru lock is already held
 */
void mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
{
	struct mem_cgroup *mem;
	if (!pc)
		return;

	mem = pc->mem_cgroup;

	spin_lock(&mem->lru_lock);
	__mem_cgroup_move_lists(pc, active);
	spin_unlock(&mem->lru_lock);
}

unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
					struct list_head *dst,
					unsigned long *scanned, int order,
					int mode, struct zone *z,
					struct mem_cgroup *mem_cont,
					int active)
{
	unsigned long nr_taken = 0;
	struct page *page;
	unsigned long scan;
	LIST_HEAD(pc_list);
	struct list_head *src;
	struct page_cgroup *pc, *tmp;

	if (active)
		src = &mem_cont->active_list;
	else
		src = &mem_cont->inactive_list;

	spin_lock(&mem_cont->lru_lock);
	scan = 0;
	list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
		if (scan >= nr_to_scan)
			break;
		page = pc->page;
		VM_BUG_ON(!pc);

		if (unlikely(!PageLRU(page)))
			continue;

		if (PageActive(page) && !active) {
			__mem_cgroup_move_lists(pc, true);
			continue;
		}
		if (!PageActive(page) && active) {
			__mem_cgroup_move_lists(pc, false);
			continue;
		}

		/*
		 * Reclaim, per zone
		 * TODO: make the active/inactive lists per zone
		 */
		if (page_zone(page) != z)
			continue;

		scan++;
		list_move(&pc->lru, &pc_list);

		if (__isolate_lru_page(page, mode) == 0) {
			list_move(&page->lru, dst);
			nr_taken++;
		}
	}

	list_splice(&pc_list, src);
	spin_unlock(&mem_cont->lru_lock);

	*scanned = scan;
	return nr_taken;
}

/*
 * Charge the memory controller for page usage.
 * Return
 * 0 if the charge was successful
 * < 0 if the cgroup is over its limit
 */
static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
				gfp_t gfp_mask, enum charge_type ctype)
{
	struct mem_cgroup *mem;
	struct page_cgroup *pc;
	unsigned long flags;
	unsigned long nr_retries = MEM_CGROUP_RECLAIM_RETRIES;

	/*
	 * Should page_cgroup's go to their own slab?
	 * One could optimize the performance of the charging routine
	 * by saving a bit in the page_flags and using it as a lock
	 * to see if the cgroup page already has a page_cgroup associated
	 * with it
	 */
retry:
	if (page) {
		lock_page_cgroup(page);
		pc = page_get_page_cgroup(page);
		/*
		 * The page_cgroup exists and
		 * the page has already been accounted.
		 */
		if (pc) {
			if (unlikely(!atomic_inc_not_zero(&pc->ref_cnt))) {
				/* this page is under being uncharged ? */
				unlock_page_cgroup(page);
				cpu_relax();
				goto retry;
			} else {
				unlock_page_cgroup(page);
				goto done;
			}
		}
		unlock_page_cgroup(page);
	}

	pc = kzalloc(sizeof(struct page_cgroup), gfp_mask);
	if (pc == NULL)
		goto err;

	/*
	 * We always charge the cgroup the mm_struct belongs to.
	 * The mm_struct's mem_cgroup changes on task migration if the
	 * thread group leader migrates. It's possible that mm is not
	 * set, if so charge the init_mm (happens for pagecache usage).
	 */
	if (!mm)
		mm = &init_mm;

	rcu_read_lock();
	mem = rcu_dereference(mm->mem_cgroup);
	/*
	 * For every charge from the cgroup, increment reference
	 * count
	 */
	css_get(&mem->css);
	rcu_read_unlock();

	/*
	 * If we created the page_cgroup, we should free it on exceeding
	 * the cgroup limit.
	 */
	while (res_counter_charge(&mem->res, PAGE_SIZE)) {
		if (!(gfp_mask & __GFP_WAIT))
			goto out;

		if (try_to_free_mem_cgroup_pages(mem, gfp_mask))
			continue;

		/*
 		 * try_to_free_mem_cgroup_pages() might not give us a full
 		 * picture of reclaim. Some pages are reclaimed and might be
 		 * moved to swap cache or just unmapped from the cgroup.
 		 * Check the limit again to see if the reclaim reduced the
 		 * current usage of the cgroup before giving up
 		 */
		if (res_counter_check_under_limit(&mem->res))
			continue;

		if (!nr_retries--) {
			mem_cgroup_out_of_memory(mem, gfp_mask);
			goto out;
		}
		congestion_wait(WRITE, HZ/10);
	}

	atomic_set(&pc->ref_cnt, 1);
	pc->mem_cgroup = mem;
	pc->page = page;
	pc->flags = PAGE_CGROUP_FLAG_ACTIVE;
	if (ctype == MEM_CGROUP_CHARGE_TYPE_CACHE)
		pc->flags |= PAGE_CGROUP_FLAG_CACHE;

	if (!page || page_cgroup_assign_new_page_cgroup(page, pc)) {
		/*
		 * Another charge has been added to this page already.
		 * We take lock_page_cgroup(page) again and read
		 * page->cgroup, increment refcnt.... just retry is OK.
		 */
		res_counter_uncharge(&mem->res, PAGE_SIZE);
		css_put(&mem->css);
		kfree(pc);
		if (!page)
			goto done;
		goto retry;
	}

	spin_lock_irqsave(&mem->lru_lock, flags);
	/* Update statistics vector */
	mem_cgroup_charge_statistics(mem, pc->flags, true);
	list_add(&pc->lru, &mem->active_list);
	spin_unlock_irqrestore(&mem->lru_lock, flags);

done:
	return 0;
out:
	css_put(&mem->css);
	kfree(pc);
err:
	return -ENOMEM;
}

int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
			gfp_t gfp_mask)
{
	return mem_cgroup_charge_common(page, mm, gfp_mask,
			MEM_CGROUP_CHARGE_TYPE_MAPPED);
}

/*
 * See if the cached pages should be charged at all?
 */
int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
				gfp_t gfp_mask)
{
	int ret = 0;
	struct mem_cgroup *mem;
	if (!mm)
		mm = &init_mm;

	rcu_read_lock();
	mem = rcu_dereference(mm->mem_cgroup);
	css_get(&mem->css);
	rcu_read_unlock();
	if (mem->control_type == MEM_CGROUP_TYPE_ALL)
		ret = mem_cgroup_charge_common(page, mm, gfp_mask,
				MEM_CGROUP_CHARGE_TYPE_CACHE);
	css_put(&mem->css);
	return ret;
}

/*
 * Uncharging is always a welcome operation, we never complain, simply
 * uncharge.
 */
void mem_cgroup_uncharge(struct page_cgroup *pc)
{
	struct mem_cgroup *mem;
	struct page *page;
	unsigned long flags;

	/*
	 * This can handle cases when a page is not charged at all and we
	 * are switching between handling the control_type.
	 */
	if (!pc)
		return;

	if (atomic_dec_and_test(&pc->ref_cnt)) {
		page = pc->page;
		/*
		 * get page->cgroup and clear it under lock.
		 * force_empty can drop page->cgroup without checking refcnt.
		 */
		if (clear_page_cgroup(page, pc) == pc) {
			mem = pc->mem_cgroup;
			css_put(&mem->css);
			res_counter_uncharge(&mem->res, PAGE_SIZE);
			spin_lock_irqsave(&mem->lru_lock, flags);
			list_del_init(&pc->lru);
			mem_cgroup_charge_statistics(mem, pc->flags, false);
			spin_unlock_irqrestore(&mem->lru_lock, flags);
			kfree(pc);
		}
	}
}
/*
 * Returns non-zero if a page (under migration) has valid page_cgroup member.
 * Refcnt of page_cgroup is incremented.
 */

int mem_cgroup_prepare_migration(struct page *page)
{
	struct page_cgroup *pc;
	int ret = 0;
	lock_page_cgroup(page);
	pc = page_get_page_cgroup(page);
	if (pc && atomic_inc_not_zero(&pc->ref_cnt))
		ret = 1;
	unlock_page_cgroup(page);
	return ret;
}

void mem_cgroup_end_migration(struct page *page)
{
	struct page_cgroup *pc = page_get_page_cgroup(page);
	mem_cgroup_uncharge(pc);
}
/*
 * We know both *page* and *newpage* are now not-on-LRU and Pg_locked.
 * And no race with uncharge() routines because page_cgroup for *page*
 * has extra one reference by mem_cgroup_prepare_migration.
 */

void mem_cgroup_page_migration(struct page *page, struct page *newpage)
{
	struct page_cgroup *pc;
retry:
	pc = page_get_page_cgroup(page);
	if (!pc)
		return;
	if (clear_page_cgroup(page, pc) != pc)
		goto retry;
	pc->page = newpage;
	lock_page_cgroup(newpage);
	page_assign_page_cgroup(newpage, pc);
	unlock_page_cgroup(newpage);
	return;
}

/*
 * This routine traverse page_cgroup in given list and drop them all.
 * This routine ignores page_cgroup->ref_cnt.
 * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
 */
#define FORCE_UNCHARGE_BATCH	(128)
static void
mem_cgroup_force_empty_list(struct mem_cgroup *mem, struct list_head *list)
{
	struct page_cgroup *pc;
	struct page *page;
	int count;
	unsigned long flags;

retry:
	count = FORCE_UNCHARGE_BATCH;
	spin_lock_irqsave(&mem->lru_lock, flags);

	while (--count && !list_empty(list)) {
		pc = list_entry(list->prev, struct page_cgroup, lru);
		page = pc->page;
		/* Avoid race with charge */
		atomic_set(&pc->ref_cnt, 0);
		if (clear_page_cgroup(page, pc) == pc) {
			css_put(&mem->css);
			res_counter_uncharge(&mem->res, PAGE_SIZE);
			list_del_init(&pc->lru);
			mem_cgroup_charge_statistics(mem, pc->flags, false);
			kfree(pc);
		} else 	/* being uncharged ? ...do relax */
			break;
	}
	spin_unlock_irqrestore(&mem->lru_lock, flags);
	if (!list_empty(list)) {
		cond_resched();
		goto retry;
	}
	return;
}

/*
 * make mem_cgroup's charge to be 0 if there is no task.
 * This enables deleting this mem_cgroup.
 */

int mem_cgroup_force_empty(struct mem_cgroup *mem)
{
	int ret = -EBUSY;
	css_get(&mem->css);
	/*
	 * page reclaim code (kswapd etc..) will move pages between
`	 * active_list <-> inactive_list while we don't take a lock.
	 * So, we have to do loop here until all lists are empty.
	 */
	while (!(list_empty(&mem->active_list) &&
		 list_empty(&mem->inactive_list))) {
		if (atomic_read(&mem->css.cgroup->count) > 0)
			goto out;
		/* drop all page_cgroup in active_list */
		mem_cgroup_force_empty_list(mem, &mem->active_list);
		/* drop all page_cgroup in inactive_list */
		mem_cgroup_force_empty_list(mem, &mem->inactive_list);
	}
	ret = 0;
out:
	css_put(&mem->css);
	return ret;
}



int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
{
	*tmp = memparse(buf, &buf);
	if (*buf != '\0')
		return -EINVAL;

	/*
	 * Round up the value to the closest page size
	 */
	*tmp = ((*tmp + PAGE_SIZE - 1) >> PAGE_SHIFT) << PAGE_SHIFT;
	return 0;
}

static ssize_t mem_cgroup_read(struct cgroup *cont,
			struct cftype *cft, struct file *file,
			char __user *userbuf, size_t nbytes, loff_t *ppos)
{
	return res_counter_read(&mem_cgroup_from_cont(cont)->res,
				cft->private, userbuf, nbytes, ppos,
				NULL);
}

static ssize_t mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
				struct file *file, const char __user *userbuf,
				size_t nbytes, loff_t *ppos)
{
	return res_counter_write(&mem_cgroup_from_cont(cont)->res,
				cft->private, userbuf, nbytes, ppos,
				mem_cgroup_write_strategy);
}

static ssize_t mem_control_type_write(struct cgroup *cont,
			struct cftype *cft, struct file *file,
			const char __user *userbuf,
			size_t nbytes, loff_t *pos)
{
	int ret;
	char *buf, *end;
	unsigned long tmp;
	struct mem_cgroup *mem;

	mem = mem_cgroup_from_cont(cont);
	buf = kmalloc(nbytes + 1, GFP_KERNEL);
	ret = -ENOMEM;
	if (buf == NULL)
		goto out;

	buf[nbytes] = 0;
	ret = -EFAULT;
	if (copy_from_user(buf, userbuf, nbytes))
		goto out_free;

	ret = -EINVAL;
	tmp = simple_strtoul(buf, &end, 10);
	if (*end != '\0')
		goto out_free;

	if (tmp <= MEM_CGROUP_TYPE_UNSPEC || tmp >= MEM_CGROUP_TYPE_MAX)
		goto out_free;

	mem->control_type = tmp;
	ret = nbytes;
out_free:
	kfree(buf);
out:
	return ret;
}

static ssize_t mem_control_type_read(struct cgroup *cont,
				struct cftype *cft,
				struct file *file, char __user *userbuf,
				size_t nbytes, loff_t *ppos)
{
	unsigned long val;
	char buf[64], *s;
	struct mem_cgroup *mem;

	mem = mem_cgroup_from_cont(cont);
	s = buf;
	val = mem->control_type;
	s += sprintf(s, "%lu\n", val);
	return simple_read_from_buffer((void __user *)userbuf, nbytes,
			ppos, buf, s - buf);
}


static ssize_t mem_force_empty_write(struct cgroup *cont,
				struct cftype *cft, struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *ppos)
{
	struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
	int ret;
	ret = mem_cgroup_force_empty(mem);
	if (!ret)
		ret = nbytes;
	return ret;
}

/*
 * Note: This should be removed if cgroup supports write-only file.
 */

static ssize_t mem_force_empty_read(struct cgroup *cont,
				struct cftype *cft,
				struct file *file, char __user *userbuf,
				size_t nbytes, loff_t *ppos)
{
	return -EINVAL;
}


static const struct mem_cgroup_stat_desc {
	const char *msg;
	u64 unit;
} mem_cgroup_stat_desc[] = {
	[MEM_CGROUP_STAT_CACHE] = { "cache", PAGE_SIZE, },
	[MEM_CGROUP_STAT_RSS] = { "rss", PAGE_SIZE, },
};

static int mem_control_stat_show(struct seq_file *m, void *arg)
{
	struct cgroup *cont = m->private;
	struct mem_cgroup *mem_cont = mem_cgroup_from_cont(cont);
	struct mem_cgroup_stat *stat = &mem_cont->stat;
	int i;

	for (i = 0; i < ARRAY_SIZE(stat->cpustat[0].count); i++) {
		s64 val;

		val = mem_cgroup_read_stat(stat, i);
		val *= mem_cgroup_stat_desc[i].unit;
		seq_printf(m, "%s %lld\n", mem_cgroup_stat_desc[i].msg,
				(long long)val);
	}
	return 0;
}

static const struct file_operations mem_control_stat_file_operations = {
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static int mem_control_stat_open(struct inode *unused, struct file *file)
{
	/* XXX __d_cont */
	struct cgroup *cont = file->f_dentry->d_parent->d_fsdata;

	file->f_op = &mem_control_stat_file_operations;
	return single_open(file, mem_control_stat_show, cont);
}



static struct cftype mem_cgroup_files[] = {
	{
		.name = "usage_in_bytes",
		.private = RES_USAGE,
		.read = mem_cgroup_read,
	},
	{
		.name = "limit_in_bytes",
		.private = RES_LIMIT,
		.write = mem_cgroup_write,
		.read = mem_cgroup_read,
	},
	{
		.name = "failcnt",
		.private = RES_FAILCNT,
		.read = mem_cgroup_read,
	},
	{
		.name = "control_type",
		.write = mem_control_type_write,
		.read = mem_control_type_read,
	},
	{
		.name = "force_empty",
		.write = mem_force_empty_write,
		.read = mem_force_empty_read,
	},
	{
		.name = "stat",
		.open = mem_control_stat_open,
	},
};

static struct mem_cgroup init_mem_cgroup;

static struct cgroup_subsys_state *
mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
	struct mem_cgroup *mem;

	if (unlikely((cont->parent) == NULL)) {
		mem = &init_mem_cgroup;
		init_mm.mem_cgroup = mem;
	} else
		mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);

	if (mem == NULL)
		return NULL;

	res_counter_init(&mem->res);
	INIT_LIST_HEAD(&mem->active_list);
	INIT_LIST_HEAD(&mem->inactive_list);
	spin_lock_init(&mem->lru_lock);
	mem->control_type = MEM_CGROUP_TYPE_ALL;
	return &mem->css;
}

static void mem_cgroup_destroy(struct cgroup_subsys *ss,
				struct cgroup *cont)
{
	kfree(mem_cgroup_from_cont(cont));
}

static int mem_cgroup_populate(struct cgroup_subsys *ss,
				struct cgroup *cont)
{
	return cgroup_add_files(cont, ss, mem_cgroup_files,
					ARRAY_SIZE(mem_cgroup_files));
}

static void mem_cgroup_move_task(struct cgroup_subsys *ss,
				struct cgroup *cont,
				struct cgroup *old_cont,
				struct task_struct *p)
{
	struct mm_struct *mm;
	struct mem_cgroup *mem, *old_mem;

	mm = get_task_mm(p);
	if (mm == NULL)
		return;

	mem = mem_cgroup_from_cont(cont);
	old_mem = mem_cgroup_from_cont(old_cont);

	if (mem == old_mem)
		goto out;

	/*
	 * Only thread group leaders are allowed to migrate, the mm_struct is
	 * in effect owned by the leader
	 */
	if (p->tgid != p->pid)
		goto out;

	css_get(&mem->css);
	rcu_assign_pointer(mm->mem_cgroup, mem);
	css_put(&old_mem->css);

out:
	mmput(mm);
	return;
}

struct cgroup_subsys mem_cgroup_subsys = {
	.name = "memory",
	.subsys_id = mem_cgroup_subsys_id,
	.create = mem_cgroup_create,
	.destroy = mem_cgroup_destroy,
	.populate = mem_cgroup_populate,
	.attach = mem_cgroup_move_task,
	.early_init = 1,
};