summaryrefslogtreecommitdiffstats
path: root/fs/ceph/snap.c
blob: 15105f9da3fd2ad9790fa4e5110c83cd6eb8ab70 (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
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
// SPDX-License-Identifier: GPL-2.0
#include <linux/ceph/ceph_debug.h>

#include <linux/sort.h>
#include <linux/slab.h>
#include <linux/iversion.h>
#include "super.h"
#include "mds_client.h"
#include <linux/ceph/decode.h>

/* unused map expires after 5 minutes */
#define CEPH_SNAPID_MAP_TIMEOUT	(5 * 60 * HZ)

/*
 * Snapshots in ceph are driven in large part by cooperation from the
 * client.  In contrast to local file systems or file servers that
 * implement snapshots at a single point in the system, ceph's
 * distributed access to storage requires clients to help decide
 * whether a write logically occurs before or after a recently created
 * snapshot.
 *
 * This provides a perfect instantanous client-wide snapshot.  Between
 * clients, however, snapshots may appear to be applied at slightly
 * different points in time, depending on delays in delivering the
 * snapshot notification.
 *
 * Snapshots are _not_ file system-wide.  Instead, each snapshot
 * applies to the subdirectory nested beneath some directory.  This
 * effectively divides the hierarchy into multiple "realms," where all
 * of the files contained by each realm share the same set of
 * snapshots.  An individual realm's snap set contains snapshots
 * explicitly created on that realm, as well as any snaps in its
 * parent's snap set _after_ the point at which the parent became it's
 * parent (due to, say, a rename).  Similarly, snaps from prior parents
 * during the time intervals during which they were the parent are included.
 *
 * The client is spared most of this detail, fortunately... it must only
 * maintains a hierarchy of realms reflecting the current parent/child
 * realm relationship, and for each realm has an explicit list of snaps
 * inherited from prior parents.
 *
 * A snap_realm struct is maintained for realms containing every inode
 * with an open cap in the system.  (The needed snap realm information is
 * provided by the MDS whenever a cap is issued, i.e., on open.)  A 'seq'
 * version number is used to ensure that as realm parameters change (new
 * snapshot, new parent, etc.) the client's realm hierarchy is updated.
 *
 * The realm hierarchy drives the generation of a 'snap context' for each
 * realm, which simply lists the resulting set of snaps for the realm.  This
 * is attached to any writes sent to OSDs.
 */
/*
 * Unfortunately error handling is a bit mixed here.  If we get a snap
 * update, but don't have enough memory to update our realm hierarchy,
 * it's not clear what we can do about it (besides complaining to the
 * console).
 */


/*
 * increase ref count for the realm
 *
 * caller must hold snap_rwsem.
 */
void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
			 struct ceph_snap_realm *realm)
{
	lockdep_assert_held(&mdsc->snap_rwsem);

	/*
	 * The 0->1 and 1->0 transitions must take the snap_empty_lock
	 * atomically with the refcount change. Go ahead and bump the
	 * nref here, unless it's 0, in which case we take the spinlock
	 * and then do the increment and remove it from the list.
	 */
	if (atomic_inc_not_zero(&realm->nref))
		return;

	spin_lock(&mdsc->snap_empty_lock);
	if (atomic_inc_return(&realm->nref) == 1)
		list_del_init(&realm->empty_item);
	spin_unlock(&mdsc->snap_empty_lock);
}

static void __insert_snap_realm(struct rb_root *root,
				struct ceph_snap_realm *new)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent = NULL;
	struct ceph_snap_realm *r = NULL;

	while (*p) {
		parent = *p;
		r = rb_entry(parent, struct ceph_snap_realm, node);
		if (new->ino < r->ino)
			p = &(*p)->rb_left;
		else if (new->ino > r->ino)
			p = &(*p)->rb_right;
		else
			BUG();
	}

	rb_link_node(&new->node, parent, p);
	rb_insert_color(&new->node, root);
}

/*
 * create and get the realm rooted at @ino and bump its ref count.
 *
 * caller must hold snap_rwsem for write.
 */
static struct ceph_snap_realm *ceph_create_snap_realm(
	struct ceph_mds_client *mdsc,
	u64 ino)
{
	struct ceph_snap_realm *realm;

	lockdep_assert_held_write(&mdsc->snap_rwsem);

	realm = kzalloc(sizeof(*realm), GFP_NOFS);
	if (!realm)
		return ERR_PTR(-ENOMEM);

	atomic_set(&realm->nref, 1);    /* for caller */
	realm->ino = ino;
	INIT_LIST_HEAD(&realm->children);
	INIT_LIST_HEAD(&realm->child_item);
	INIT_LIST_HEAD(&realm->empty_item);
	INIT_LIST_HEAD(&realm->dirty_item);
	INIT_LIST_HEAD(&realm->inodes_with_caps);
	spin_lock_init(&realm->inodes_with_caps_lock);
	__insert_snap_realm(&mdsc->snap_realms, realm);
	mdsc->num_snap_realms++;

	dout("create_snap_realm %llx %p\n", realm->ino, realm);
	return realm;
}

/*
 * lookup the realm rooted at @ino.
 *
 * caller must hold snap_rwsem.
 */
static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
						   u64 ino)
{
	struct rb_node *n = mdsc->snap_realms.rb_node;
	struct ceph_snap_realm *r;

	lockdep_assert_held(&mdsc->snap_rwsem);

	while (n) {
		r = rb_entry(n, struct ceph_snap_realm, node);
		if (ino < r->ino)
			n = n->rb_left;
		else if (ino > r->ino)
			n = n->rb_right;
		else {
			dout("lookup_snap_realm %llx %p\n", r->ino, r);
			return r;
		}
	}
	return NULL;
}

struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
					       u64 ino)
{
	struct ceph_snap_realm *r;
	r = __lookup_snap_realm(mdsc, ino);
	if (r)
		ceph_get_snap_realm(mdsc, r);
	return r;
}

static void __put_snap_realm(struct ceph_mds_client *mdsc,
			     struct ceph_snap_realm *realm);

/*
 * called with snap_rwsem (write)
 */
static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
				 struct ceph_snap_realm *realm)
{
	lockdep_assert_held_write(&mdsc->snap_rwsem);

	dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);

	rb_erase(&realm->node, &mdsc->snap_realms);
	mdsc->num_snap_realms--;

	if (realm->parent) {
		list_del_init(&realm->child_item);
		__put_snap_realm(mdsc, realm->parent);
	}

	kfree(realm->prior_parent_snaps);
	kfree(realm->snaps);
	ceph_put_snap_context(realm->cached_context);
	kfree(realm);
}

/*
 * caller holds snap_rwsem (write)
 */
static void __put_snap_realm(struct ceph_mds_client *mdsc,
			     struct ceph_snap_realm *realm)
{
	lockdep_assert_held_write(&mdsc->snap_rwsem);

	/*
	 * We do not require the snap_empty_lock here, as any caller that
	 * increments the value must hold the snap_rwsem.
	 */
	if (atomic_dec_and_test(&realm->nref))
		__destroy_snap_realm(mdsc, realm);
}

/*
 * See comments in ceph_get_snap_realm. Caller needn't hold any locks.
 */
void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
			 struct ceph_snap_realm *realm)
{
	if (!atomic_dec_and_lock(&realm->nref, &mdsc->snap_empty_lock))
		return;

	if (down_write_trylock(&mdsc->snap_rwsem)) {
		spin_unlock(&mdsc->snap_empty_lock);
		__destroy_snap_realm(mdsc, realm);
		up_write(&mdsc->snap_rwsem);
	} else {
		list_add(&realm->empty_item, &mdsc->snap_empty);
		spin_unlock(&mdsc->snap_empty_lock);
	}
}

/*
 * Clean up any realms whose ref counts have dropped to zero.  Note
 * that this does not include realms who were created but not yet
 * used.
 *
 * Called under snap_rwsem (write)
 */
static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
{
	struct ceph_snap_realm *realm;

	lockdep_assert_held_write(&mdsc->snap_rwsem);

	spin_lock(&mdsc->snap_empty_lock);
	while (!list_empty(&mdsc->snap_empty)) {
		realm = list_first_entry(&mdsc->snap_empty,
				   struct ceph_snap_realm, empty_item);
		list_del(&realm->empty_item);
		spin_unlock(&mdsc->snap_empty_lock);
		__destroy_snap_realm(mdsc, realm);
		spin_lock(&mdsc->snap_empty_lock);
	}
	spin_unlock(&mdsc->snap_empty_lock);
}

void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
{
	down_write(&mdsc->snap_rwsem);
	__cleanup_empty_realms(mdsc);
	up_write(&mdsc->snap_rwsem);
}

/*
 * adjust the parent realm of a given @realm.  adjust child list, and parent
 * pointers, and ref counts appropriately.
 *
 * return true if parent was changed, 0 if unchanged, <0 on error.
 *
 * caller must hold snap_rwsem for write.
 */
static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
				    struct ceph_snap_realm *realm,
				    u64 parentino)
{
	struct ceph_snap_realm *parent;

	lockdep_assert_held_write(&mdsc->snap_rwsem);

	if (realm->parent_ino == parentino)
		return 0;

	parent = ceph_lookup_snap_realm(mdsc, parentino);
	if (!parent) {
		parent = ceph_create_snap_realm(mdsc, parentino);
		if (IS_ERR(parent))
			return PTR_ERR(parent);
	}
	dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
	     realm->ino, realm, realm->parent_ino, realm->parent,
	     parentino, parent);
	if (realm->parent) {
		list_del_init(&realm->child_item);
		ceph_put_snap_realm(mdsc, realm->parent);
	}
	realm->parent_ino = parentino;
	realm->parent = parent;
	list_add(&realm->child_item, &parent->children);
	return 1;
}


static int cmpu64_rev(const void *a, const void *b)
{
	if (*(u64 *)a < *(u64 *)b)
		return 1;
	if (*(u64 *)a > *(u64 *)b)
		return -1;
	return 0;
}


/*
 * build the snap context for a given realm.
 */
static int build_snap_context(struct ceph_snap_realm *realm,
			      struct list_head* dirty_realms)
{
	struct ceph_snap_realm *parent = realm->parent;
	struct ceph_snap_context *snapc;
	int err = 0;
	u32 num = realm->num_prior_parent_snaps + realm->num_snaps;

	/*
	 * build parent context, if it hasn't been built.
	 * conservatively estimate that all parent snaps might be
	 * included by us.
	 */
	if (parent) {
		if (!parent->cached_context) {
			err = build_snap_context(parent, dirty_realms);
			if (err)
				goto fail;
		}
		num += parent->cached_context->num_snaps;
	}

	/* do i actually need to update?  not if my context seq
	   matches realm seq, and my parents' does to.  (this works
	   because we rebuild_snap_realms() works _downward_ in
	   hierarchy after each update.) */
	if (realm->cached_context &&
	    realm->cached_context->seq == realm->seq &&
	    (!parent ||
	     realm->cached_context->seq >= parent->cached_context->seq)) {
		dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
		     " (unchanged)\n",
		     realm->ino, realm, realm->cached_context,
		     realm->cached_context->seq,
		     (unsigned int)realm->cached_context->num_snaps);
		return 0;
	}

	/* alloc new snap context */
	err = -ENOMEM;
	if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
		goto fail;
	snapc = ceph_create_snap_context(num, GFP_NOFS);
	if (!snapc)
		goto fail;

	/* build (reverse sorted) snap vector */
	num = 0;
	snapc->seq = realm->seq;
	if (parent) {
		u32 i;

		/* include any of parent's snaps occurring _after_ my
		   parent became my parent */
		for (i = 0; i < parent->cached_context->num_snaps; i++)
			if (parent->cached_context->snaps[i] >=
			    realm->parent_since)
				snapc->snaps[num++] =
					parent->cached_context->snaps[i];
		if (parent->cached_context->seq > snapc->seq)
			snapc->seq = parent->cached_context->seq;
	}
	memcpy(snapc->snaps + num, realm->snaps,
	       sizeof(u64)*realm->num_snaps);
	num += realm->num_snaps;
	memcpy(snapc->snaps + num, realm->prior_parent_snaps,
	       sizeof(u64)*realm->num_prior_parent_snaps);
	num += realm->num_prior_parent_snaps;

	sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
	snapc->num_snaps = num;
	dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
	     realm->ino, realm, snapc, snapc->seq,
	     (unsigned int) snapc->num_snaps);

	ceph_put_snap_context(realm->cached_context);
	realm->cached_context = snapc;
	/* queue realm for cap_snap creation */
	list_add_tail(&realm->dirty_item, dirty_realms);
	return 0;

fail:
	/*
	 * if we fail, clear old (incorrect) cached_context... hopefully
	 * we'll have better luck building it later
	 */
	if (realm->cached_context) {
		ceph_put_snap_context(realm->cached_context);
		realm->cached_context = NULL;
	}
	pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
	       realm, err);
	return err;
}

/*
 * rebuild snap context for the given realm and all of its children.
 */
static void rebuild_snap_realms(struct ceph_snap_realm *realm,
				struct list_head *dirty_realms)
{
	struct ceph_snap_realm *child;

	dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
	build_snap_context(realm, dirty_realms);

	list_for_each_entry(child, &realm->children, child_item)
		rebuild_snap_realms(child, dirty_realms);
}


/*
 * helper to allocate and decode an array of snapids.  free prior
 * instance, if any.
 */
static int dup_array(u64 **dst, __le64 *src, u32 num)
{
	u32 i;

	kfree(*dst);
	if (num) {
		*dst = kcalloc(num, sizeof(u64), GFP_NOFS);
		if (!*dst)
			return -ENOMEM;
		for (i = 0; i < num; i++)
			(*dst)[i] = get_unaligned_le64(src + i);
	} else {
		*dst = NULL;
	}
	return 0;
}

static bool has_new_snaps(struct ceph_snap_context *o,
			  struct ceph_snap_context *n)
{
	if (n->num_snaps == 0)
		return false;
	/* snaps are in descending order */
	return n->snaps[0] > o->seq;
}

/*
 * When a snapshot is applied, the size/mtime inode metadata is queued
 * in a ceph_cap_snap (one for each snapshot) until writeback
 * completes and the metadata can be flushed back to the MDS.
 *
 * However, if a (sync) write is currently in-progress when we apply
 * the snapshot, we have to wait until the write succeeds or fails
 * (and a final size/mtime is known).  In this case the
 * cap_snap->writing = 1, and is said to be "pending."  When the write
 * finishes, we __ceph_finish_cap_snap().
 *
 * Caller must hold snap_rwsem for read (i.e., the realm topology won't
 * change).
 */
static void ceph_queue_cap_snap(struct ceph_inode_info *ci)
{
	struct inode *inode = &ci->vfs_inode;
	struct ceph_cap_snap *capsnap;
	struct ceph_snap_context *old_snapc, *new_snapc;
	struct ceph_buffer *old_blob = NULL;
	int used, dirty;

	capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
	if (!capsnap) {
		pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
		return;
	}
	capsnap->cap_flush.is_capsnap = true;
	INIT_LIST_HEAD(&capsnap->cap_flush.i_list);
	INIT_LIST_HEAD(&capsnap->cap_flush.g_list);

	spin_lock(&ci->i_ceph_lock);
	used = __ceph_caps_used(ci);
	dirty = __ceph_caps_dirty(ci);

	old_snapc = ci->i_head_snapc;
	new_snapc = ci->i_snap_realm->cached_context;

	/*
	 * If there is a write in progress, treat that as a dirty Fw,
	 * even though it hasn't completed yet; by the time we finish
	 * up this capsnap it will be.
	 */
	if (used & CEPH_CAP_FILE_WR)
		dirty |= CEPH_CAP_FILE_WR;

	if (__ceph_have_pending_cap_snap(ci)) {
		/* there is no point in queuing multiple "pending" cap_snaps,
		   as no new writes are allowed to start when pending, so any
		   writes in progress now were started before the previous
		   cap_snap.  lucky us. */
		dout("queue_cap_snap %p already pending\n", inode);
		goto update_snapc;
	}
	if (ci->i_wrbuffer_ref_head == 0 &&
	    !(dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))) {
		dout("queue_cap_snap %p nothing dirty|writing\n", inode);
		goto update_snapc;
	}

	BUG_ON(!old_snapc);

	/*
	 * There is no need to send FLUSHSNAP message to MDS if there is
	 * no new snapshot. But when there is dirty pages or on-going
	 * writes, we still need to create cap_snap. cap_snap is needed
	 * by the write path and page writeback path.
	 *
	 * also see ceph_try_drop_cap_snap()
	 */
	if (has_new_snaps(old_snapc, new_snapc)) {
		if (dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))
			capsnap->need_flush = true;
	} else {
		if (!(used & CEPH_CAP_FILE_WR) &&
		    ci->i_wrbuffer_ref_head == 0) {
			dout("queue_cap_snap %p "
			     "no new_snap|dirty_page|writing\n", inode);
			goto update_snapc;
		}
	}

	dout("queue_cap_snap %p cap_snap %p queuing under %p %s %s\n",
	     inode, capsnap, old_snapc, ceph_cap_string(dirty),
	     capsnap->need_flush ? "" : "no_flush");
	ihold(inode);

	refcount_set(&capsnap->nref, 1);
	INIT_LIST_HEAD(&capsnap->ci_item);

	capsnap->follows = old_snapc->seq;
	capsnap->issued = __ceph_caps_issued(ci, NULL);
	capsnap->dirty = dirty;

	capsnap->mode = inode->i_mode;
	capsnap->uid = inode->i_uid;
	capsnap->gid = inode->i_gid;

	if (dirty & CEPH_CAP_XATTR_EXCL) {
		old_blob = __ceph_build_xattrs_blob(ci);
		capsnap->xattr_blob =
			ceph_buffer_get(ci->i_xattrs.blob);
		capsnap->xattr_version = ci->i_xattrs.version;
	} else {
		capsnap->xattr_blob = NULL;
		capsnap->xattr_version = 0;
	}

	capsnap->inline_data = ci->i_inline_version != CEPH_INLINE_NONE;

	/* dirty page count moved from _head to this cap_snap;
	   all subsequent writes page dirties occur _after_ this
	   snapshot. */
	capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
	ci->i_wrbuffer_ref_head = 0;
	capsnap->context = old_snapc;
	list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);

	if (used & CEPH_CAP_FILE_WR) {
		dout("queue_cap_snap %p cap_snap %p snapc %p"
		     " seq %llu used WR, now pending\n", inode,
		     capsnap, old_snapc, old_snapc->seq);
		capsnap->writing = 1;
	} else {
		/* note mtime, size NOW. */
		__ceph_finish_cap_snap(ci, capsnap);
	}
	capsnap = NULL;
	old_snapc = NULL;

update_snapc:
       if (ci->i_wrbuffer_ref_head == 0 &&
           ci->i_wr_ref == 0 &&
           ci->i_dirty_caps == 0 &&
           ci->i_flushing_caps == 0) {
               ci->i_head_snapc = NULL;
       } else {
		ci->i_head_snapc = ceph_get_snap_context(new_snapc);
		dout(" new snapc is %p\n", new_snapc);
	}
	spin_unlock(&ci->i_ceph_lock);

	ceph_buffer_put(old_blob);
	kfree(capsnap);
	ceph_put_snap_context(old_snapc);
}

/*
 * Finalize the size, mtime for a cap_snap.. that is, settle on final values
 * to be used for the snapshot, to be flushed back to the mds.
 *
 * If capsnap can now be flushed, add to snap_flush list, and return 1.
 *
 * Caller must hold i_ceph_lock.
 */
int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
			    struct ceph_cap_snap *capsnap)
{
	struct inode *inode = &ci->vfs_inode;
	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(inode->i_sb);

	BUG_ON(capsnap->writing);
	capsnap->size = i_size_read(inode);
	capsnap->mtime = inode->i_mtime;
	capsnap->atime = inode->i_atime;
	capsnap->ctime = inode->i_ctime;
	capsnap->btime = ci->i_btime;
	capsnap->change_attr = inode_peek_iversion_raw(inode);
	capsnap->time_warp_seq = ci->i_time_warp_seq;
	capsnap->truncate_size = ci->i_truncate_size;
	capsnap->truncate_seq = ci->i_truncate_seq;
	if (capsnap->dirty_pages) {
		dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
		     "still has %d dirty pages\n", inode, capsnap,
		     capsnap->context, capsnap->context->seq,
		     ceph_cap_string(capsnap->dirty), capsnap->size,
		     capsnap->dirty_pages);
		return 0;
	}

	/* Fb cap still in use, delay it */
	if (ci->i_wb_ref) {
		dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
		     "used WRBUFFER, delaying\n", inode, capsnap,
		     capsnap->context, capsnap->context->seq,
		     ceph_cap_string(capsnap->dirty), capsnap->size);
		capsnap->writing = 1;
		return 0;
	}

	ci->i_ceph_flags |= CEPH_I_FLUSH_SNAPS;
	dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
	     inode, capsnap, capsnap->context,
	     capsnap->context->seq, ceph_cap_string(capsnap->dirty),
	     capsnap->size);

	spin_lock(&mdsc->snap_flush_lock);
	if (list_empty(&ci->i_snap_flush_item))
		list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
	spin_unlock(&mdsc->snap_flush_lock);
	return 1;  /* caller may want to ceph_flush_snaps */
}

/*
 * Queue cap_snaps for snap writeback for this realm and its children.
 * Called under snap_rwsem, so realm topology won't change.
 */
static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
{
	struct ceph_inode_info *ci;
	struct inode *lastinode = NULL;

	dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);

	spin_lock(&realm->inodes_with_caps_lock);
	list_for_each_entry(ci, &realm->inodes_with_caps, i_snap_realm_item) {
		struct inode *inode = igrab(&ci->vfs_inode);
		if (!inode)
			continue;
		spin_unlock(&realm->inodes_with_caps_lock);
		iput(lastinode);
		lastinode = inode;
		ceph_queue_cap_snap(ci);
		spin_lock(&realm->inodes_with_caps_lock);
	}
	spin_unlock(&realm->inodes_with_caps_lock);
	iput(lastinode);

	dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
}

/*
 * Parse and apply a snapblob "snap trace" from the MDS.  This specifies
 * the snap realm parameters from a given realm and all of its ancestors,
 * up to the root.
 *
 * Caller must hold snap_rwsem for write.
 */
int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
			   void *p, void *e, bool deletion,
			   struct ceph_snap_realm **realm_ret)
{
	struct ceph_mds_snap_realm *ri;    /* encoded */
	__le64 *snaps;                     /* encoded */
	__le64 *prior_parent_snaps;        /* encoded */
	struct ceph_snap_realm *realm = NULL;
	struct ceph_snap_realm *first_realm = NULL;
	int invalidate = 0;
	int err = -ENOMEM;
	LIST_HEAD(dirty_realms);

	lockdep_assert_held_write(&mdsc->snap_rwsem);

	dout("update_snap_trace deletion=%d\n", deletion);
more:
	ceph_decode_need(&p, e, sizeof(*ri), bad);
	ri = p;
	p += sizeof(*ri);
	ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) +
			    le32_to_cpu(ri->num_prior_parent_snaps)), bad);
	snaps = p;
	p += sizeof(u64) * le32_to_cpu(ri->num_snaps);
	prior_parent_snaps = p;
	p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps);

	realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino));
	if (!realm) {
		realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino));
		if (IS_ERR(realm)) {
			err = PTR_ERR(realm);
			goto fail;
		}
	}

	/* ensure the parent is correct */
	err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
	if (err < 0)
		goto fail;
	invalidate += err;

	if (le64_to_cpu(ri->seq) > realm->seq) {
		dout("update_snap_trace updating %llx %p %lld -> %lld\n",
		     realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
		/* update realm parameters, snap lists */
		realm->seq = le64_to_cpu(ri->seq);
		realm->created = le64_to_cpu(ri->created);
		realm->parent_since = le64_to_cpu(ri->parent_since);

		realm->num_snaps = le32_to_cpu(ri->num_snaps);
		err = dup_array(&realm->snaps, snaps, realm->num_snaps);
		if (err < 0)
			goto fail;

		realm->num_prior_parent_snaps =
			le32_to_cpu(ri->num_prior_parent_snaps);
		err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps,
				realm->num_prior_parent_snaps);
		if (err < 0)
			goto fail;

		if (realm->seq > mdsc->last_snap_seq)
			mdsc->last_snap_seq = realm->seq;

		invalidate = 1;
	} else if (!realm->cached_context) {
		dout("update_snap_trace %llx %p seq %lld new\n",
		     realm->ino, realm, realm->seq);
		invalidate = 1;
	} else {
		dout("update_snap_trace %llx %p seq %lld unchanged\n",
		     realm->ino, realm, realm->seq);
	}

	dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
	     realm, invalidate, p, e);

	/* invalidate when we reach the _end_ (root) of the trace */
	if (invalidate && p >= e)
		rebuild_snap_realms(realm, &dirty_realms);

	if (!first_realm)
		first_realm = realm;
	else
		ceph_put_snap_realm(mdsc, realm);

	if (p < e)
		goto more;

	/*
	 * queue cap snaps _after_ we've built the new snap contexts,
	 * so that i_head_snapc can be set appropriately.
	 */
	while (!list_empty(&dirty_realms)) {
		realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
					 dirty_item);
		list_del_init(&realm->dirty_item);
		queue_realm_cap_snaps(realm);
	}

	if (realm_ret)
		*realm_ret = first_realm;
	else
		ceph_put_snap_realm(mdsc, first_realm);

	__cleanup_empty_realms(mdsc);
	return 0;

bad:
	err = -EIO;
fail:
	if (realm && !IS_ERR(realm))
		ceph_put_snap_realm(mdsc, realm);
	if (first_realm)
		ceph_put_snap_realm(mdsc, first_realm);
	pr_err("update_snap_trace error %d\n", err);
	return err;
}


/*
 * Send any cap_snaps that are queued for flush.  Try to carry
 * s_mutex across multiple snap flushes to avoid locking overhead.
 *
 * Caller holds no locks.
 */
static void flush_snaps(struct ceph_mds_client *mdsc)
{
	struct ceph_inode_info *ci;
	struct inode *inode;
	struct ceph_mds_session *session = NULL;

	dout("flush_snaps\n");
	spin_lock(&mdsc->snap_flush_lock);
	while (!list_empty(&mdsc->snap_flush_list)) {
		ci = list_first_entry(&mdsc->snap_flush_list,
				struct ceph_inode_info, i_snap_flush_item);
		inode = &ci->vfs_inode;
		ihold(inode);
		spin_unlock(&mdsc->snap_flush_lock);
		ceph_flush_snaps(ci, &session);
		iput(inode);
		spin_lock(&mdsc->snap_flush_lock);
	}
	spin_unlock(&mdsc->snap_flush_lock);

	ceph_put_mds_session(session);
	dout("flush_snaps done\n");
}


/*
 * Handle a snap notification from the MDS.
 *
 * This can take two basic forms: the simplest is just a snap creation
 * or deletion notification on an existing realm.  This should update the
 * realm and its children.
 *
 * The more difficult case is realm creation, due to snap creation at a
 * new point in the file hierarchy, or due to a rename that moves a file or
 * directory into another realm.
 */
void ceph_handle_snap(struct ceph_mds_client *mdsc,
		      struct ceph_mds_session *session,
		      struct ceph_msg *msg)
{
	struct super_block *sb = mdsc->fsc->sb;
	int mds = session->s_mds;
	u64 split;
	int op;
	int trace_len;
	struct ceph_snap_realm *realm = NULL;
	void *p = msg->front.iov_base;
	void *e = p + msg->front.iov_len;
	struct ceph_mds_snap_head *h;
	int num_split_inos, num_split_realms;
	__le64 *split_inos = NULL, *split_realms = NULL;
	int i;
	int locked_rwsem = 0;

	/* decode */
	if (msg->front.iov_len < sizeof(*h))
		goto bad;
	h = p;
	op = le32_to_cpu(h->op);
	split = le64_to_cpu(h->split);   /* non-zero if we are splitting an
					  * existing realm */
	num_split_inos = le32_to_cpu(h->num_split_inos);
	num_split_realms = le32_to_cpu(h->num_split_realms);
	trace_len = le32_to_cpu(h->trace_len);
	p += sizeof(*h);

	dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
	     ceph_snap_op_name(op), split, trace_len);

	mutex_lock(&session->s_mutex);
	inc_session_sequence(session);
	mutex_unlock(&session->s_mutex);

	down_write(&mdsc->snap_rwsem);
	locked_rwsem = 1;

	if (op == CEPH_SNAP_OP_SPLIT) {
		struct ceph_mds_snap_realm *ri;

		/*
		 * A "split" breaks part of an existing realm off into
		 * a new realm.  The MDS provides a list of inodes
		 * (with caps) and child realms that belong to the new
		 * child.
		 */
		split_inos = p;
		p += sizeof(u64) * num_split_inos;
		split_realms = p;
		p += sizeof(u64) * num_split_realms;
		ceph_decode_need(&p, e, sizeof(*ri), bad);
		/* we will peek at realm info here, but will _not_
		 * advance p, as the realm update will occur below in
		 * ceph_update_snap_trace. */
		ri = p;

		realm = ceph_lookup_snap_realm(mdsc, split);
		if (!realm) {
			realm = ceph_create_snap_realm(mdsc, split);
			if (IS_ERR(realm))
				goto out;
		}

		dout("splitting snap_realm %llx %p\n", realm->ino, realm);
		for (i = 0; i < num_split_inos; i++) {
			struct ceph_vino vino = {
				.ino = le64_to_cpu(split_inos[i]),
				.snap = CEPH_NOSNAP,
			};
			struct inode *inode = ceph_find_inode(sb, vino);
			struct ceph_inode_info *ci;
			struct ceph_snap_realm *oldrealm;

			if (!inode)
				continue;
			ci = ceph_inode(inode);

			spin_lock(&ci->i_ceph_lock);
			if (!ci->i_snap_realm)
				goto skip_inode;
			/*
			 * If this inode belongs to a realm that was
			 * created after our new realm, we experienced
			 * a race (due to another split notifications
			 * arriving from a different MDS).  So skip
			 * this inode.
			 */
			if (ci->i_snap_realm->created >
			    le64_to_cpu(ri->created)) {
				dout(" leaving %p in newer realm %llx %p\n",
				     inode, ci->i_snap_realm->ino,
				     ci->i_snap_realm);
				goto skip_inode;
			}
			dout(" will move %p to split realm %llx %p\n",
			     inode, realm->ino, realm);
			/*
			 * Move the inode to the new realm
			 */
			oldrealm = ci->i_snap_realm;
			spin_lock(&oldrealm->inodes_with_caps_lock);
			list_del_init(&ci->i_snap_realm_item);
			spin_unlock(&oldrealm->inodes_with_caps_lock);

			spin_lock(&realm->inodes_with_caps_lock);
			list_add(&ci->i_snap_realm_item,
				 &realm->inodes_with_caps);
			ci->i_snap_realm = realm;
			if (realm->ino == ci->i_vino.ino)
                                realm->inode = inode;
			spin_unlock(&realm->inodes_with_caps_lock);

			spin_unlock(&ci->i_ceph_lock);

			ceph_get_snap_realm(mdsc, realm);
			ceph_put_snap_realm(mdsc, oldrealm);

			iput(inode);
			continue;

skip_inode:
			spin_unlock(&ci->i_ceph_lock);
			iput(inode);
		}

		/* we may have taken some of the old realm's children. */
		for (i = 0; i < num_split_realms; i++) {
			struct ceph_snap_realm *child =
				__lookup_snap_realm(mdsc,
					   le64_to_cpu(split_realms[i]));
			if (!child)
				continue;
			adjust_snap_realm_parent(mdsc, child, realm->ino);
		}
	}

	/*
	 * update using the provided snap trace. if we are deleting a
	 * snap, we can avoid queueing cap_snaps.
	 */
	ceph_update_snap_trace(mdsc, p, e,
			       op == CEPH_SNAP_OP_DESTROY, NULL);

	if (op == CEPH_SNAP_OP_SPLIT)
		/* we took a reference when we created the realm, above */
		ceph_put_snap_realm(mdsc, realm);

	__cleanup_empty_realms(mdsc);

	up_write(&mdsc->snap_rwsem);

	flush_snaps(mdsc);
	return;

bad:
	pr_err("corrupt snap message from mds%d\n", mds);
	ceph_msg_dump(msg);
out:
	if (locked_rwsem)
		up_write(&mdsc->snap_rwsem);
	return;
}

struct ceph_snapid_map* ceph_get_snapid_map(struct ceph_mds_client *mdsc,
					    u64 snap)
{
	struct ceph_snapid_map *sm, *exist;
	struct rb_node **p, *parent;
	int ret;

	exist = NULL;
	spin_lock(&mdsc->snapid_map_lock);
	p = &mdsc->snapid_map_tree.rb_node;
	while (*p) {
		exist = rb_entry(*p, struct ceph_snapid_map, node);
		if (snap > exist->snap) {
			p = &(*p)->rb_left;
		} else if (snap < exist->snap) {
			p = &(*p)->rb_right;
		} else {
			if (atomic_inc_return(&exist->ref) == 1)
				list_del_init(&exist->lru);
			break;
		}
		exist = NULL;
	}
	spin_unlock(&mdsc->snapid_map_lock);
	if (exist) {
		dout("found snapid map %llx -> %x\n", exist->snap, exist->dev);
		return exist;
	}

	sm = kmalloc(sizeof(*sm), GFP_NOFS);
	if (!sm)
		return NULL;

	ret = get_anon_bdev(&sm->dev);
	if (ret < 0) {
		kfree(sm);
		return NULL;
	}

	INIT_LIST_HEAD(&sm->lru);
	atomic_set(&sm->ref, 1);
	sm->snap = snap;

	exist = NULL;
	parent = NULL;
	p = &mdsc->snapid_map_tree.rb_node;
	spin_lock(&mdsc->snapid_map_lock);
	while (*p) {
		parent = *p;
		exist = rb_entry(*p, struct ceph_snapid_map, node);
		if (snap > exist->snap)
			p = &(*p)->rb_left;
		else if (snap < exist->snap)
			p = &(*p)->rb_right;
		else
			break;
		exist = NULL;
	}
	if (exist) {
		if (atomic_inc_return(&exist->ref) == 1)
			list_del_init(&exist->lru);
	} else {
		rb_link_node(&sm->node, parent, p);
		rb_insert_color(&sm->node, &mdsc->snapid_map_tree);
	}
	spin_unlock(&mdsc->snapid_map_lock);
	if (exist) {
		free_anon_bdev(sm->dev);
		kfree(sm);
		dout("found snapid map %llx -> %x\n", exist->snap, exist->dev);
		return exist;
	}

	dout("create snapid map %llx -> %x\n", sm->snap, sm->dev);
	return sm;
}

void ceph_put_snapid_map(struct ceph_mds_client* mdsc,
			 struct ceph_snapid_map *sm)
{
	if (!sm)
		return;
	if (atomic_dec_and_lock(&sm->ref, &mdsc->snapid_map_lock)) {
		if (!RB_EMPTY_NODE(&sm->node)) {
			sm->last_used = jiffies;
			list_add_tail(&sm->lru, &mdsc->snapid_map_lru);
			spin_unlock(&mdsc->snapid_map_lock);
		} else {
			/* already cleaned up by
			 * ceph_cleanup_snapid_map() */
			spin_unlock(&mdsc->snapid_map_lock);
			kfree(sm);
		}
	}
}

void ceph_trim_snapid_map(struct ceph_mds_client *mdsc)
{
	struct ceph_snapid_map *sm;
	unsigned long now;
	LIST_HEAD(to_free);

	spin_lock(&mdsc->snapid_map_lock);
	now = jiffies;

	while (!list_empty(&mdsc->snapid_map_lru)) {
		sm = list_first_entry(&mdsc->snapid_map_lru,
				      struct ceph_snapid_map, lru);
		if (time_after(sm->last_used + CEPH_SNAPID_MAP_TIMEOUT, now))
			break;

		rb_erase(&sm->node, &mdsc->snapid_map_tree);
		list_move(&sm->lru, &to_free);
	}
	spin_unlock(&mdsc->snapid_map_lock);

	while (!list_empty(&to_free)) {
		sm = list_first_entry(&to_free, struct ceph_snapid_map, lru);
		list_del(&sm->lru);
		dout("trim snapid map %llx -> %x\n", sm->snap, sm->dev);
		free_anon_bdev(sm->dev);
		kfree(sm);
	}
}

void ceph_cleanup_snapid_map(struct ceph_mds_client *mdsc)
{
	struct ceph_snapid_map *sm;
	struct rb_node *p;
	LIST_HEAD(to_free);

	spin_lock(&mdsc->snapid_map_lock);
	while ((p = rb_first(&mdsc->snapid_map_tree))) {
		sm = rb_entry(p, struct ceph_snapid_map, node);
		rb_erase(p, &mdsc->snapid_map_tree);
		RB_CLEAR_NODE(p);
		list_move(&sm->lru, &to_free);
	}
	spin_unlock(&mdsc->snapid_map_lock);

	while (!list_empty(&to_free)) {
		sm = list_first_entry(&to_free, struct ceph_snapid_map, lru);
		list_del(&sm->lru);
		free_anon_bdev(sm->dev);
		if (WARN_ON_ONCE(atomic_read(&sm->ref))) {
			pr_err("snapid map %llx -> %x still in use\n",
			       sm->snap, sm->dev);
		}
		kfree(sm);
	}
}