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1#include <linux/ceph/ceph_debug.h>
2
3#include <linux/sort.h>
4#include <linux/slab.h>
5
6#include "super.h"
7#include "mds_client.h"
8
9#include <linux/ceph/decode.h>
10
11/*
12 * Snapshots in ceph are driven in large part by cooperation from the
13 * client. In contrast to local file systems or file servers that
14 * implement snapshots at a single point in the system, ceph's
15 * distributed access to storage requires clients to help decide
16 * whether a write logically occurs before or after a recently created
17 * snapshot.
18 *
19 * This provides a perfect instantanous client-wide snapshot. Between
20 * clients, however, snapshots may appear to be applied at slightly
21 * different points in time, depending on delays in delivering the
22 * snapshot notification.
23 *
24 * Snapshots are _not_ file system-wide. Instead, each snapshot
25 * applies to the subdirectory nested beneath some directory. This
26 * effectively divides the hierarchy into multiple "realms," where all
27 * of the files contained by each realm share the same set of
28 * snapshots. An individual realm's snap set contains snapshots
29 * explicitly created on that realm, as well as any snaps in its
30 * parent's snap set _after_ the point at which the parent became it's
31 * parent (due to, say, a rename). Similarly, snaps from prior parents
32 * during the time intervals during which they were the parent are included.
33 *
34 * The client is spared most of this detail, fortunately... it must only
35 * maintains a hierarchy of realms reflecting the current parent/child
36 * realm relationship, and for each realm has an explicit list of snaps
37 * inherited from prior parents.
38 *
39 * A snap_realm struct is maintained for realms containing every inode
40 * with an open cap in the system. (The needed snap realm information is
41 * provided by the MDS whenever a cap is issued, i.e., on open.) A 'seq'
42 * version number is used to ensure that as realm parameters change (new
43 * snapshot, new parent, etc.) the client's realm hierarchy is updated.
44 *
45 * The realm hierarchy drives the generation of a 'snap context' for each
46 * realm, which simply lists the resulting set of snaps for the realm. This
47 * is attached to any writes sent to OSDs.
48 */
49/*
50 * Unfortunately error handling is a bit mixed here. If we get a snap
51 * update, but don't have enough memory to update our realm hierarchy,
52 * it's not clear what we can do about it (besides complaining to the
53 * console).
54 */
55
56
57/*
58 * increase ref count for the realm
59 *
60 * caller must hold snap_rwsem for write.
61 */
62void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
63 struct ceph_snap_realm *realm)
64{
65 dout("get_realm %p %d -> %d\n", realm,
66 atomic_read(&realm->nref), atomic_read(&realm->nref)+1);
67 /*
68 * since we _only_ increment realm refs or empty the empty
69 * list with snap_rwsem held, adjusting the empty list here is
70 * safe. we do need to protect against concurrent empty list
71 * additions, however.
72 */
73 if (atomic_inc_return(&realm->nref) == 1) {
74 spin_lock(&mdsc->snap_empty_lock);
75 list_del_init(&realm->empty_item);
76 spin_unlock(&mdsc->snap_empty_lock);
77 }
78}
79
80static void __insert_snap_realm(struct rb_root *root,
81 struct ceph_snap_realm *new)
82{
83 struct rb_node **p = &root->rb_node;
84 struct rb_node *parent = NULL;
85 struct ceph_snap_realm *r = NULL;
86
87 while (*p) {
88 parent = *p;
89 r = rb_entry(parent, struct ceph_snap_realm, node);
90 if (new->ino < r->ino)
91 p = &(*p)->rb_left;
92 else if (new->ino > r->ino)
93 p = &(*p)->rb_right;
94 else
95 BUG();
96 }
97
98 rb_link_node(&new->node, parent, p);
99 rb_insert_color(&new->node, root);
100}
101
102/*
103 * create and get the realm rooted at @ino and bump its ref count.
104 *
105 * caller must hold snap_rwsem for write.
106 */
107static struct ceph_snap_realm *ceph_create_snap_realm(
108 struct ceph_mds_client *mdsc,
109 u64 ino)
110{
111 struct ceph_snap_realm *realm;
112
113 realm = kzalloc(sizeof(*realm), GFP_NOFS);
114 if (!realm)
115 return ERR_PTR(-ENOMEM);
116
117 atomic_set(&realm->nref, 1); /* for caller */
118 realm->ino = ino;
119 INIT_LIST_HEAD(&realm->children);
120 INIT_LIST_HEAD(&realm->child_item);
121 INIT_LIST_HEAD(&realm->empty_item);
122 INIT_LIST_HEAD(&realm->dirty_item);
123 INIT_LIST_HEAD(&realm->inodes_with_caps);
124 spin_lock_init(&realm->inodes_with_caps_lock);
125 __insert_snap_realm(&mdsc->snap_realms, realm);
126 dout("create_snap_realm %llx %p\n", realm->ino, realm);
127 return realm;
128}
129
130/*
131 * lookup the realm rooted at @ino.
132 *
133 * caller must hold snap_rwsem for write.
134 */
135static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
136 u64 ino)
137{
138 struct rb_node *n = mdsc->snap_realms.rb_node;
139 struct ceph_snap_realm *r;
140
141 while (n) {
142 r = rb_entry(n, struct ceph_snap_realm, node);
143 if (ino < r->ino)
144 n = n->rb_left;
145 else if (ino > r->ino)
146 n = n->rb_right;
147 else {
148 dout("lookup_snap_realm %llx %p\n", r->ino, r);
149 return r;
150 }
151 }
152 return NULL;
153}
154
155struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
156 u64 ino)
157{
158 struct ceph_snap_realm *r;
159 r = __lookup_snap_realm(mdsc, ino);
160 if (r)
161 ceph_get_snap_realm(mdsc, r);
162 return r;
163}
164
165static void __put_snap_realm(struct ceph_mds_client *mdsc,
166 struct ceph_snap_realm *realm);
167
168/*
169 * called with snap_rwsem (write)
170 */
171static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
172 struct ceph_snap_realm *realm)
173{
174 dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);
175
176 rb_erase(&realm->node, &mdsc->snap_realms);
177
178 if (realm->parent) {
179 list_del_init(&realm->child_item);
180 __put_snap_realm(mdsc, realm->parent);
181 }
182
183 kfree(realm->prior_parent_snaps);
184 kfree(realm->snaps);
185 ceph_put_snap_context(realm->cached_context);
186 kfree(realm);
187}
188
189/*
190 * caller holds snap_rwsem (write)
191 */
192static void __put_snap_realm(struct ceph_mds_client *mdsc,
193 struct ceph_snap_realm *realm)
194{
195 dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
196 atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
197 if (atomic_dec_and_test(&realm->nref))
198 __destroy_snap_realm(mdsc, realm);
199}
200
201/*
202 * caller needn't hold any locks
203 */
204void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
205 struct ceph_snap_realm *realm)
206{
207 dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
208 atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
209 if (!atomic_dec_and_test(&realm->nref))
210 return;
211
212 if (down_write_trylock(&mdsc->snap_rwsem)) {
213 __destroy_snap_realm(mdsc, realm);
214 up_write(&mdsc->snap_rwsem);
215 } else {
216 spin_lock(&mdsc->snap_empty_lock);
217 list_add(&realm->empty_item, &mdsc->snap_empty);
218 spin_unlock(&mdsc->snap_empty_lock);
219 }
220}
221
222/*
223 * Clean up any realms whose ref counts have dropped to zero. Note
224 * that this does not include realms who were created but not yet
225 * used.
226 *
227 * Called under snap_rwsem (write)
228 */
229static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
230{
231 struct ceph_snap_realm *realm;
232
233 spin_lock(&mdsc->snap_empty_lock);
234 while (!list_empty(&mdsc->snap_empty)) {
235 realm = list_first_entry(&mdsc->snap_empty,
236 struct ceph_snap_realm, empty_item);
237 list_del(&realm->empty_item);
238 spin_unlock(&mdsc->snap_empty_lock);
239 __destroy_snap_realm(mdsc, realm);
240 spin_lock(&mdsc->snap_empty_lock);
241 }
242 spin_unlock(&mdsc->snap_empty_lock);
243}
244
245void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
246{
247 down_write(&mdsc->snap_rwsem);
248 __cleanup_empty_realms(mdsc);
249 up_write(&mdsc->snap_rwsem);
250}
251
252/*
253 * adjust the parent realm of a given @realm. adjust child list, and parent
254 * pointers, and ref counts appropriately.
255 *
256 * return true if parent was changed, 0 if unchanged, <0 on error.
257 *
258 * caller must hold snap_rwsem for write.
259 */
260static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
261 struct ceph_snap_realm *realm,
262 u64 parentino)
263{
264 struct ceph_snap_realm *parent;
265
266 if (realm->parent_ino == parentino)
267 return 0;
268
269 parent = ceph_lookup_snap_realm(mdsc, parentino);
270 if (!parent) {
271 parent = ceph_create_snap_realm(mdsc, parentino);
272 if (IS_ERR(parent))
273 return PTR_ERR(parent);
274 }
275 dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
276 realm->ino, realm, realm->parent_ino, realm->parent,
277 parentino, parent);
278 if (realm->parent) {
279 list_del_init(&realm->child_item);
280 ceph_put_snap_realm(mdsc, realm->parent);
281 }
282 realm->parent_ino = parentino;
283 realm->parent = parent;
284 list_add(&realm->child_item, &parent->children);
285 return 1;
286}
287
288
289static int cmpu64_rev(const void *a, const void *b)
290{
291 if (*(u64 *)a < *(u64 *)b)
292 return 1;
293 if (*(u64 *)a > *(u64 *)b)
294 return -1;
295 return 0;
296}
297
298
299/*
300 * build the snap context for a given realm.
301 */
302static int build_snap_context(struct ceph_snap_realm *realm)
303{
304 struct ceph_snap_realm *parent = realm->parent;
305 struct ceph_snap_context *snapc;
306 int err = 0;
307 u32 num = realm->num_prior_parent_snaps + realm->num_snaps;
308
309 /*
310 * build parent context, if it hasn't been built.
311 * conservatively estimate that all parent snaps might be
312 * included by us.
313 */
314 if (parent) {
315 if (!parent->cached_context) {
316 err = build_snap_context(parent);
317 if (err)
318 goto fail;
319 }
320 num += parent->cached_context->num_snaps;
321 }
322
323 /* do i actually need to update? not if my context seq
324 matches realm seq, and my parents' does to. (this works
325 because we rebuild_snap_realms() works _downward_ in
326 hierarchy after each update.) */
327 if (realm->cached_context &&
328 realm->cached_context->seq == realm->seq &&
329 (!parent ||
330 realm->cached_context->seq >= parent->cached_context->seq)) {
331 dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
332 " (unchanged)\n",
333 realm->ino, realm, realm->cached_context,
334 realm->cached_context->seq,
335 (unsigned int) realm->cached_context->num_snaps);
336 return 0;
337 }
338
339 /* alloc new snap context */
340 err = -ENOMEM;
341 if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
342 goto fail;
343 snapc = ceph_create_snap_context(num, GFP_NOFS);
344 if (!snapc)
345 goto fail;
346
347 /* build (reverse sorted) snap vector */
348 num = 0;
349 snapc->seq = realm->seq;
350 if (parent) {
351 u32 i;
352
353 /* include any of parent's snaps occurring _after_ my
354 parent became my parent */
355 for (i = 0; i < parent->cached_context->num_snaps; i++)
356 if (parent->cached_context->snaps[i] >=
357 realm->parent_since)
358 snapc->snaps[num++] =
359 parent->cached_context->snaps[i];
360 if (parent->cached_context->seq > snapc->seq)
361 snapc->seq = parent->cached_context->seq;
362 }
363 memcpy(snapc->snaps + num, realm->snaps,
364 sizeof(u64)*realm->num_snaps);
365 num += realm->num_snaps;
366 memcpy(snapc->snaps + num, realm->prior_parent_snaps,
367 sizeof(u64)*realm->num_prior_parent_snaps);
368 num += realm->num_prior_parent_snaps;
369
370 sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
371 snapc->num_snaps = num;
372 dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
373 realm->ino, realm, snapc, snapc->seq,
374 (unsigned int) snapc->num_snaps);
375
376 ceph_put_snap_context(realm->cached_context);
377 realm->cached_context = snapc;
378 return 0;
379
380fail:
381 /*
382 * if we fail, clear old (incorrect) cached_context... hopefully
383 * we'll have better luck building it later
384 */
385 if (realm->cached_context) {
386 ceph_put_snap_context(realm->cached_context);
387 realm->cached_context = NULL;
388 }
389 pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
390 realm, err);
391 return err;
392}
393
394/*
395 * rebuild snap context for the given realm and all of its children.
396 */
397static void rebuild_snap_realms(struct ceph_snap_realm *realm)
398{
399 struct ceph_snap_realm *child;
400
401 dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
402 build_snap_context(realm);
403
404 list_for_each_entry(child, &realm->children, child_item)
405 rebuild_snap_realms(child);
406}
407
408
409/*
410 * helper to allocate and decode an array of snapids. free prior
411 * instance, if any.
412 */
413static int dup_array(u64 **dst, __le64 *src, u32 num)
414{
415 u32 i;
416
417 kfree(*dst);
418 if (num) {
419 *dst = kcalloc(num, sizeof(u64), GFP_NOFS);
420 if (!*dst)
421 return -ENOMEM;
422 for (i = 0; i < num; i++)
423 (*dst)[i] = get_unaligned_le64(src + i);
424 } else {
425 *dst = NULL;
426 }
427 return 0;
428}
429
430static bool has_new_snaps(struct ceph_snap_context *o,
431 struct ceph_snap_context *n)
432{
433 if (n->num_snaps == 0)
434 return false;
435 /* snaps are in descending order */
436 return n->snaps[0] > o->seq;
437}
438
439/*
440 * When a snapshot is applied, the size/mtime inode metadata is queued
441 * in a ceph_cap_snap (one for each snapshot) until writeback
442 * completes and the metadata can be flushed back to the MDS.
443 *
444 * However, if a (sync) write is currently in-progress when we apply
445 * the snapshot, we have to wait until the write succeeds or fails
446 * (and a final size/mtime is known). In this case the
447 * cap_snap->writing = 1, and is said to be "pending." When the write
448 * finishes, we __ceph_finish_cap_snap().
449 *
450 * Caller must hold snap_rwsem for read (i.e., the realm topology won't
451 * change).
452 */
453void ceph_queue_cap_snap(struct ceph_inode_info *ci)
454{
455 struct inode *inode = &ci->vfs_inode;
456 struct ceph_cap_snap *capsnap;
457 struct ceph_snap_context *old_snapc, *new_snapc;
458 int used, dirty;
459
460 capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
461 if (!capsnap) {
462 pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
463 return;
464 }
465
466 spin_lock(&ci->i_ceph_lock);
467 used = __ceph_caps_used(ci);
468 dirty = __ceph_caps_dirty(ci);
469
470 old_snapc = ci->i_head_snapc;
471 new_snapc = ci->i_snap_realm->cached_context;
472
473 /*
474 * If there is a write in progress, treat that as a dirty Fw,
475 * even though it hasn't completed yet; by the time we finish
476 * up this capsnap it will be.
477 */
478 if (used & CEPH_CAP_FILE_WR)
479 dirty |= CEPH_CAP_FILE_WR;
480
481 if (__ceph_have_pending_cap_snap(ci)) {
482 /* there is no point in queuing multiple "pending" cap_snaps,
483 as no new writes are allowed to start when pending, so any
484 writes in progress now were started before the previous
485 cap_snap. lucky us. */
486 dout("queue_cap_snap %p already pending\n", inode);
487 goto update_snapc;
488 }
489 if (ci->i_wrbuffer_ref_head == 0 &&
490 !(dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))) {
491 dout("queue_cap_snap %p nothing dirty|writing\n", inode);
492 goto update_snapc;
493 }
494
495 BUG_ON(!old_snapc);
496
497 /*
498 * There is no need to send FLUSHSNAP message to MDS if there is
499 * no new snapshot. But when there is dirty pages or on-going
500 * writes, we still need to create cap_snap. cap_snap is needed
501 * by the write path and page writeback path.
502 *
503 * also see ceph_try_drop_cap_snap()
504 */
505 if (has_new_snaps(old_snapc, new_snapc)) {
506 if (dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))
507 capsnap->need_flush = true;
508 } else {
509 if (!(used & CEPH_CAP_FILE_WR) &&
510 ci->i_wrbuffer_ref_head == 0) {
511 dout("queue_cap_snap %p "
512 "no new_snap|dirty_page|writing\n", inode);
513 goto update_snapc;
514 }
515 }
516
517 dout("queue_cap_snap %p cap_snap %p queuing under %p %s %s\n",
518 inode, capsnap, old_snapc, ceph_cap_string(dirty),
519 capsnap->need_flush ? "" : "no_flush");
520 ihold(inode);
521
522 atomic_set(&capsnap->nref, 1);
523 capsnap->ci = ci;
524 INIT_LIST_HEAD(&capsnap->ci_item);
525 INIT_LIST_HEAD(&capsnap->flushing_item);
526
527 capsnap->follows = old_snapc->seq;
528 capsnap->issued = __ceph_caps_issued(ci, NULL);
529 capsnap->dirty = dirty;
530
531 capsnap->mode = inode->i_mode;
532 capsnap->uid = inode->i_uid;
533 capsnap->gid = inode->i_gid;
534
535 if (dirty & CEPH_CAP_XATTR_EXCL) {
536 __ceph_build_xattrs_blob(ci);
537 capsnap->xattr_blob =
538 ceph_buffer_get(ci->i_xattrs.blob);
539 capsnap->xattr_version = ci->i_xattrs.version;
540 } else {
541 capsnap->xattr_blob = NULL;
542 capsnap->xattr_version = 0;
543 }
544
545 capsnap->inline_data = ci->i_inline_version != CEPH_INLINE_NONE;
546
547 /* dirty page count moved from _head to this cap_snap;
548 all subsequent writes page dirties occur _after_ this
549 snapshot. */
550 capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
551 ci->i_wrbuffer_ref_head = 0;
552 capsnap->context = old_snapc;
553 list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
554 old_snapc = NULL;
555
556 if (used & CEPH_CAP_FILE_WR) {
557 dout("queue_cap_snap %p cap_snap %p snapc %p"
558 " seq %llu used WR, now pending\n", inode,
559 capsnap, old_snapc, old_snapc->seq);
560 capsnap->writing = 1;
561 } else {
562 /* note mtime, size NOW. */
563 __ceph_finish_cap_snap(ci, capsnap);
564 }
565 capsnap = NULL;
566
567update_snapc:
568 if (ci->i_head_snapc) {
569 ci->i_head_snapc = ceph_get_snap_context(new_snapc);
570 dout(" new snapc is %p\n", new_snapc);
571 }
572 spin_unlock(&ci->i_ceph_lock);
573
574 kfree(capsnap);
575 ceph_put_snap_context(old_snapc);
576}
577
578/*
579 * Finalize the size, mtime for a cap_snap.. that is, settle on final values
580 * to be used for the snapshot, to be flushed back to the mds.
581 *
582 * If capsnap can now be flushed, add to snap_flush list, and return 1.
583 *
584 * Caller must hold i_ceph_lock.
585 */
586int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
587 struct ceph_cap_snap *capsnap)
588{
589 struct inode *inode = &ci->vfs_inode;
590 struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
591
592 BUG_ON(capsnap->writing);
593 capsnap->size = inode->i_size;
594 capsnap->mtime = inode->i_mtime;
595 capsnap->atime = inode->i_atime;
596 capsnap->ctime = inode->i_ctime;
597 capsnap->time_warp_seq = ci->i_time_warp_seq;
598 if (capsnap->dirty_pages) {
599 dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
600 "still has %d dirty pages\n", inode, capsnap,
601 capsnap->context, capsnap->context->seq,
602 ceph_cap_string(capsnap->dirty), capsnap->size,
603 capsnap->dirty_pages);
604 return 0;
605 }
606 dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
607 inode, capsnap, capsnap->context,
608 capsnap->context->seq, ceph_cap_string(capsnap->dirty),
609 capsnap->size);
610
611 spin_lock(&mdsc->snap_flush_lock);
612 list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
613 spin_unlock(&mdsc->snap_flush_lock);
614 return 1; /* caller may want to ceph_flush_snaps */
615}
616
617/*
618 * Queue cap_snaps for snap writeback for this realm and its children.
619 * Called under snap_rwsem, so realm topology won't change.
620 */
621static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
622{
623 struct ceph_inode_info *ci;
624 struct inode *lastinode = NULL;
625 struct ceph_snap_realm *child;
626
627 dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);
628
629 spin_lock(&realm->inodes_with_caps_lock);
630 list_for_each_entry(ci, &realm->inodes_with_caps,
631 i_snap_realm_item) {
632 struct inode *inode = igrab(&ci->vfs_inode);
633 if (!inode)
634 continue;
635 spin_unlock(&realm->inodes_with_caps_lock);
636 iput(lastinode);
637 lastinode = inode;
638 ceph_queue_cap_snap(ci);
639 spin_lock(&realm->inodes_with_caps_lock);
640 }
641 spin_unlock(&realm->inodes_with_caps_lock);
642 iput(lastinode);
643
644 list_for_each_entry(child, &realm->children, child_item) {
645 dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
646 realm, realm->ino, child, child->ino);
647 list_del_init(&child->dirty_item);
648 list_add(&child->dirty_item, &realm->dirty_item);
649 }
650
651 list_del_init(&realm->dirty_item);
652 dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
653}
654
655/*
656 * Parse and apply a snapblob "snap trace" from the MDS. This specifies
657 * the snap realm parameters from a given realm and all of its ancestors,
658 * up to the root.
659 *
660 * Caller must hold snap_rwsem for write.
661 */
662int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
663 void *p, void *e, bool deletion,
664 struct ceph_snap_realm **realm_ret)
665{
666 struct ceph_mds_snap_realm *ri; /* encoded */
667 __le64 *snaps; /* encoded */
668 __le64 *prior_parent_snaps; /* encoded */
669 struct ceph_snap_realm *realm = NULL;
670 struct ceph_snap_realm *first_realm = NULL;
671 int invalidate = 0;
672 int err = -ENOMEM;
673 LIST_HEAD(dirty_realms);
674
675 dout("update_snap_trace deletion=%d\n", deletion);
676more:
677 ceph_decode_need(&p, e, sizeof(*ri), bad);
678 ri = p;
679 p += sizeof(*ri);
680 ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) +
681 le32_to_cpu(ri->num_prior_parent_snaps)), bad);
682 snaps = p;
683 p += sizeof(u64) * le32_to_cpu(ri->num_snaps);
684 prior_parent_snaps = p;
685 p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps);
686
687 realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino));
688 if (!realm) {
689 realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino));
690 if (IS_ERR(realm)) {
691 err = PTR_ERR(realm);
692 goto fail;
693 }
694 }
695
696 /* ensure the parent is correct */
697 err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
698 if (err < 0)
699 goto fail;
700 invalidate += err;
701
702 if (le64_to_cpu(ri->seq) > realm->seq) {
703 dout("update_snap_trace updating %llx %p %lld -> %lld\n",
704 realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
705 /* update realm parameters, snap lists */
706 realm->seq = le64_to_cpu(ri->seq);
707 realm->created = le64_to_cpu(ri->created);
708 realm->parent_since = le64_to_cpu(ri->parent_since);
709
710 realm->num_snaps = le32_to_cpu(ri->num_snaps);
711 err = dup_array(&realm->snaps, snaps, realm->num_snaps);
712 if (err < 0)
713 goto fail;
714
715 realm->num_prior_parent_snaps =
716 le32_to_cpu(ri->num_prior_parent_snaps);
717 err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps,
718 realm->num_prior_parent_snaps);
719 if (err < 0)
720 goto fail;
721
722 /* queue realm for cap_snap creation */
723 list_add(&realm->dirty_item, &dirty_realms);
724 if (realm->seq > mdsc->last_snap_seq)
725 mdsc->last_snap_seq = realm->seq;
726
727 invalidate = 1;
728 } else if (!realm->cached_context) {
729 dout("update_snap_trace %llx %p seq %lld new\n",
730 realm->ino, realm, realm->seq);
731 invalidate = 1;
732 } else {
733 dout("update_snap_trace %llx %p seq %lld unchanged\n",
734 realm->ino, realm, realm->seq);
735 }
736
737 dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
738 realm, invalidate, p, e);
739
740 /* invalidate when we reach the _end_ (root) of the trace */
741 if (invalidate && p >= e)
742 rebuild_snap_realms(realm);
743
744 if (!first_realm)
745 first_realm = realm;
746 else
747 ceph_put_snap_realm(mdsc, realm);
748
749 if (p < e)
750 goto more;
751
752 /*
753 * queue cap snaps _after_ we've built the new snap contexts,
754 * so that i_head_snapc can be set appropriately.
755 */
756 while (!list_empty(&dirty_realms)) {
757 realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
758 dirty_item);
759 queue_realm_cap_snaps(realm);
760 }
761
762 if (realm_ret)
763 *realm_ret = first_realm;
764 else
765 ceph_put_snap_realm(mdsc, first_realm);
766
767 __cleanup_empty_realms(mdsc);
768 return 0;
769
770bad:
771 err = -EINVAL;
772fail:
773 if (realm && !IS_ERR(realm))
774 ceph_put_snap_realm(mdsc, realm);
775 if (first_realm)
776 ceph_put_snap_realm(mdsc, first_realm);
777 pr_err("update_snap_trace error %d\n", err);
778 return err;
779}
780
781
782/*
783 * Send any cap_snaps that are queued for flush. Try to carry
784 * s_mutex across multiple snap flushes to avoid locking overhead.
785 *
786 * Caller holds no locks.
787 */
788static void flush_snaps(struct ceph_mds_client *mdsc)
789{
790 struct ceph_inode_info *ci;
791 struct inode *inode;
792 struct ceph_mds_session *session = NULL;
793
794 dout("flush_snaps\n");
795 spin_lock(&mdsc->snap_flush_lock);
796 while (!list_empty(&mdsc->snap_flush_list)) {
797 ci = list_first_entry(&mdsc->snap_flush_list,
798 struct ceph_inode_info, i_snap_flush_item);
799 inode = &ci->vfs_inode;
800 ihold(inode);
801 spin_unlock(&mdsc->snap_flush_lock);
802 spin_lock(&ci->i_ceph_lock);
803 __ceph_flush_snaps(ci, &session, 0);
804 spin_unlock(&ci->i_ceph_lock);
805 iput(inode);
806 spin_lock(&mdsc->snap_flush_lock);
807 }
808 spin_unlock(&mdsc->snap_flush_lock);
809
810 if (session) {
811 mutex_unlock(&session->s_mutex);
812 ceph_put_mds_session(session);
813 }
814 dout("flush_snaps done\n");
815}
816
817
818/*
819 * Handle a snap notification from the MDS.
820 *
821 * This can take two basic forms: the simplest is just a snap creation
822 * or deletion notification on an existing realm. This should update the
823 * realm and its children.
824 *
825 * The more difficult case is realm creation, due to snap creation at a
826 * new point in the file hierarchy, or due to a rename that moves a file or
827 * directory into another realm.
828 */
829void ceph_handle_snap(struct ceph_mds_client *mdsc,
830 struct ceph_mds_session *session,
831 struct ceph_msg *msg)
832{
833 struct super_block *sb = mdsc->fsc->sb;
834 int mds = session->s_mds;
835 u64 split;
836 int op;
837 int trace_len;
838 struct ceph_snap_realm *realm = NULL;
839 void *p = msg->front.iov_base;
840 void *e = p + msg->front.iov_len;
841 struct ceph_mds_snap_head *h;
842 int num_split_inos, num_split_realms;
843 __le64 *split_inos = NULL, *split_realms = NULL;
844 int i;
845 int locked_rwsem = 0;
846
847 /* decode */
848 if (msg->front.iov_len < sizeof(*h))
849 goto bad;
850 h = p;
851 op = le32_to_cpu(h->op);
852 split = le64_to_cpu(h->split); /* non-zero if we are splitting an
853 * existing realm */
854 num_split_inos = le32_to_cpu(h->num_split_inos);
855 num_split_realms = le32_to_cpu(h->num_split_realms);
856 trace_len = le32_to_cpu(h->trace_len);
857 p += sizeof(*h);
858
859 dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
860 ceph_snap_op_name(op), split, trace_len);
861
862 mutex_lock(&session->s_mutex);
863 session->s_seq++;
864 mutex_unlock(&session->s_mutex);
865
866 down_write(&mdsc->snap_rwsem);
867 locked_rwsem = 1;
868
869 if (op == CEPH_SNAP_OP_SPLIT) {
870 struct ceph_mds_snap_realm *ri;
871
872 /*
873 * A "split" breaks part of an existing realm off into
874 * a new realm. The MDS provides a list of inodes
875 * (with caps) and child realms that belong to the new
876 * child.
877 */
878 split_inos = p;
879 p += sizeof(u64) * num_split_inos;
880 split_realms = p;
881 p += sizeof(u64) * num_split_realms;
882 ceph_decode_need(&p, e, sizeof(*ri), bad);
883 /* we will peek at realm info here, but will _not_
884 * advance p, as the realm update will occur below in
885 * ceph_update_snap_trace. */
886 ri = p;
887
888 realm = ceph_lookup_snap_realm(mdsc, split);
889 if (!realm) {
890 realm = ceph_create_snap_realm(mdsc, split);
891 if (IS_ERR(realm))
892 goto out;
893 }
894
895 dout("splitting snap_realm %llx %p\n", realm->ino, realm);
896 for (i = 0; i < num_split_inos; i++) {
897 struct ceph_vino vino = {
898 .ino = le64_to_cpu(split_inos[i]),
899 .snap = CEPH_NOSNAP,
900 };
901 struct inode *inode = ceph_find_inode(sb, vino);
902 struct ceph_inode_info *ci;
903 struct ceph_snap_realm *oldrealm;
904
905 if (!inode)
906 continue;
907 ci = ceph_inode(inode);
908
909 spin_lock(&ci->i_ceph_lock);
910 if (!ci->i_snap_realm)
911 goto skip_inode;
912 /*
913 * If this inode belongs to a realm that was
914 * created after our new realm, we experienced
915 * a race (due to another split notifications
916 * arriving from a different MDS). So skip
917 * this inode.
918 */
919 if (ci->i_snap_realm->created >
920 le64_to_cpu(ri->created)) {
921 dout(" leaving %p in newer realm %llx %p\n",
922 inode, ci->i_snap_realm->ino,
923 ci->i_snap_realm);
924 goto skip_inode;
925 }
926 dout(" will move %p to split realm %llx %p\n",
927 inode, realm->ino, realm);
928 /*
929 * Move the inode to the new realm
930 */
931 spin_lock(&realm->inodes_with_caps_lock);
932 list_del_init(&ci->i_snap_realm_item);
933 list_add(&ci->i_snap_realm_item,
934 &realm->inodes_with_caps);
935 oldrealm = ci->i_snap_realm;
936 ci->i_snap_realm = realm;
937 spin_unlock(&realm->inodes_with_caps_lock);
938 spin_unlock(&ci->i_ceph_lock);
939
940 ceph_get_snap_realm(mdsc, realm);
941 ceph_put_snap_realm(mdsc, oldrealm);
942
943 iput(inode);
944 continue;
945
946skip_inode:
947 spin_unlock(&ci->i_ceph_lock);
948 iput(inode);
949 }
950
951 /* we may have taken some of the old realm's children. */
952 for (i = 0; i < num_split_realms; i++) {
953 struct ceph_snap_realm *child =
954 __lookup_snap_realm(mdsc,
955 le64_to_cpu(split_realms[i]));
956 if (!child)
957 continue;
958 adjust_snap_realm_parent(mdsc, child, realm->ino);
959 }
960 }
961
962 /*
963 * update using the provided snap trace. if we are deleting a
964 * snap, we can avoid queueing cap_snaps.
965 */
966 ceph_update_snap_trace(mdsc, p, e,
967 op == CEPH_SNAP_OP_DESTROY, NULL);
968
969 if (op == CEPH_SNAP_OP_SPLIT)
970 /* we took a reference when we created the realm, above */
971 ceph_put_snap_realm(mdsc, realm);
972
973 __cleanup_empty_realms(mdsc);
974
975 up_write(&mdsc->snap_rwsem);
976
977 flush_snaps(mdsc);
978 return;
979
980bad:
981 pr_err("corrupt snap message from mds%d\n", mds);
982 ceph_msg_dump(msg);
983out:
984 if (locked_rwsem)
985 up_write(&mdsc->snap_rwsem);
986 return;
987}
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/ceph/ceph_debug.h>
3
4#include <linux/sort.h>
5#include <linux/slab.h>
6
7#include "super.h"
8#include "mds_client.h"
9
10#include <linux/ceph/decode.h>
11
12/*
13 * Snapshots in ceph are driven in large part by cooperation from the
14 * client. In contrast to local file systems or file servers that
15 * implement snapshots at a single point in the system, ceph's
16 * distributed access to storage requires clients to help decide
17 * whether a write logically occurs before or after a recently created
18 * snapshot.
19 *
20 * This provides a perfect instantanous client-wide snapshot. Between
21 * clients, however, snapshots may appear to be applied at slightly
22 * different points in time, depending on delays in delivering the
23 * snapshot notification.
24 *
25 * Snapshots are _not_ file system-wide. Instead, each snapshot
26 * applies to the subdirectory nested beneath some directory. This
27 * effectively divides the hierarchy into multiple "realms," where all
28 * of the files contained by each realm share the same set of
29 * snapshots. An individual realm's snap set contains snapshots
30 * explicitly created on that realm, as well as any snaps in its
31 * parent's snap set _after_ the point at which the parent became it's
32 * parent (due to, say, a rename). Similarly, snaps from prior parents
33 * during the time intervals during which they were the parent are included.
34 *
35 * The client is spared most of this detail, fortunately... it must only
36 * maintains a hierarchy of realms reflecting the current parent/child
37 * realm relationship, and for each realm has an explicit list of snaps
38 * inherited from prior parents.
39 *
40 * A snap_realm struct is maintained for realms containing every inode
41 * with an open cap in the system. (The needed snap realm information is
42 * provided by the MDS whenever a cap is issued, i.e., on open.) A 'seq'
43 * version number is used to ensure that as realm parameters change (new
44 * snapshot, new parent, etc.) the client's realm hierarchy is updated.
45 *
46 * The realm hierarchy drives the generation of a 'snap context' for each
47 * realm, which simply lists the resulting set of snaps for the realm. This
48 * is attached to any writes sent to OSDs.
49 */
50/*
51 * Unfortunately error handling is a bit mixed here. If we get a snap
52 * update, but don't have enough memory to update our realm hierarchy,
53 * it's not clear what we can do about it (besides complaining to the
54 * console).
55 */
56
57
58/*
59 * increase ref count for the realm
60 *
61 * caller must hold snap_rwsem for write.
62 */
63void ceph_get_snap_realm(struct ceph_mds_client *mdsc,
64 struct ceph_snap_realm *realm)
65{
66 dout("get_realm %p %d -> %d\n", realm,
67 atomic_read(&realm->nref), atomic_read(&realm->nref)+1);
68 /*
69 * since we _only_ increment realm refs or empty the empty
70 * list with snap_rwsem held, adjusting the empty list here is
71 * safe. we do need to protect against concurrent empty list
72 * additions, however.
73 */
74 if (atomic_inc_return(&realm->nref) == 1) {
75 spin_lock(&mdsc->snap_empty_lock);
76 list_del_init(&realm->empty_item);
77 spin_unlock(&mdsc->snap_empty_lock);
78 }
79}
80
81static void __insert_snap_realm(struct rb_root *root,
82 struct ceph_snap_realm *new)
83{
84 struct rb_node **p = &root->rb_node;
85 struct rb_node *parent = NULL;
86 struct ceph_snap_realm *r = NULL;
87
88 while (*p) {
89 parent = *p;
90 r = rb_entry(parent, struct ceph_snap_realm, node);
91 if (new->ino < r->ino)
92 p = &(*p)->rb_left;
93 else if (new->ino > r->ino)
94 p = &(*p)->rb_right;
95 else
96 BUG();
97 }
98
99 rb_link_node(&new->node, parent, p);
100 rb_insert_color(&new->node, root);
101}
102
103/*
104 * create and get the realm rooted at @ino and bump its ref count.
105 *
106 * caller must hold snap_rwsem for write.
107 */
108static struct ceph_snap_realm *ceph_create_snap_realm(
109 struct ceph_mds_client *mdsc,
110 u64 ino)
111{
112 struct ceph_snap_realm *realm;
113
114 realm = kzalloc(sizeof(*realm), GFP_NOFS);
115 if (!realm)
116 return ERR_PTR(-ENOMEM);
117
118 atomic_set(&realm->nref, 1); /* for caller */
119 realm->ino = ino;
120 INIT_LIST_HEAD(&realm->children);
121 INIT_LIST_HEAD(&realm->child_item);
122 INIT_LIST_HEAD(&realm->empty_item);
123 INIT_LIST_HEAD(&realm->dirty_item);
124 INIT_LIST_HEAD(&realm->inodes_with_caps);
125 spin_lock_init(&realm->inodes_with_caps_lock);
126 __insert_snap_realm(&mdsc->snap_realms, realm);
127 dout("create_snap_realm %llx %p\n", realm->ino, realm);
128 return realm;
129}
130
131/*
132 * lookup the realm rooted at @ino.
133 *
134 * caller must hold snap_rwsem for write.
135 */
136static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc,
137 u64 ino)
138{
139 struct rb_node *n = mdsc->snap_realms.rb_node;
140 struct ceph_snap_realm *r;
141
142 while (n) {
143 r = rb_entry(n, struct ceph_snap_realm, node);
144 if (ino < r->ino)
145 n = n->rb_left;
146 else if (ino > r->ino)
147 n = n->rb_right;
148 else {
149 dout("lookup_snap_realm %llx %p\n", r->ino, r);
150 return r;
151 }
152 }
153 return NULL;
154}
155
156struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
157 u64 ino)
158{
159 struct ceph_snap_realm *r;
160 r = __lookup_snap_realm(mdsc, ino);
161 if (r)
162 ceph_get_snap_realm(mdsc, r);
163 return r;
164}
165
166static void __put_snap_realm(struct ceph_mds_client *mdsc,
167 struct ceph_snap_realm *realm);
168
169/*
170 * called with snap_rwsem (write)
171 */
172static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
173 struct ceph_snap_realm *realm)
174{
175 dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);
176
177 rb_erase(&realm->node, &mdsc->snap_realms);
178
179 if (realm->parent) {
180 list_del_init(&realm->child_item);
181 __put_snap_realm(mdsc, realm->parent);
182 }
183
184 kfree(realm->prior_parent_snaps);
185 kfree(realm->snaps);
186 ceph_put_snap_context(realm->cached_context);
187 kfree(realm);
188}
189
190/*
191 * caller holds snap_rwsem (write)
192 */
193static void __put_snap_realm(struct ceph_mds_client *mdsc,
194 struct ceph_snap_realm *realm)
195{
196 dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
197 atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
198 if (atomic_dec_and_test(&realm->nref))
199 __destroy_snap_realm(mdsc, realm);
200}
201
202/*
203 * caller needn't hold any locks
204 */
205void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
206 struct ceph_snap_realm *realm)
207{
208 dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
209 atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
210 if (!atomic_dec_and_test(&realm->nref))
211 return;
212
213 if (down_write_trylock(&mdsc->snap_rwsem)) {
214 __destroy_snap_realm(mdsc, realm);
215 up_write(&mdsc->snap_rwsem);
216 } else {
217 spin_lock(&mdsc->snap_empty_lock);
218 list_add(&realm->empty_item, &mdsc->snap_empty);
219 spin_unlock(&mdsc->snap_empty_lock);
220 }
221}
222
223/*
224 * Clean up any realms whose ref counts have dropped to zero. Note
225 * that this does not include realms who were created but not yet
226 * used.
227 *
228 * Called under snap_rwsem (write)
229 */
230static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
231{
232 struct ceph_snap_realm *realm;
233
234 spin_lock(&mdsc->snap_empty_lock);
235 while (!list_empty(&mdsc->snap_empty)) {
236 realm = list_first_entry(&mdsc->snap_empty,
237 struct ceph_snap_realm, empty_item);
238 list_del(&realm->empty_item);
239 spin_unlock(&mdsc->snap_empty_lock);
240 __destroy_snap_realm(mdsc, realm);
241 spin_lock(&mdsc->snap_empty_lock);
242 }
243 spin_unlock(&mdsc->snap_empty_lock);
244}
245
246void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
247{
248 down_write(&mdsc->snap_rwsem);
249 __cleanup_empty_realms(mdsc);
250 up_write(&mdsc->snap_rwsem);
251}
252
253/*
254 * adjust the parent realm of a given @realm. adjust child list, and parent
255 * pointers, and ref counts appropriately.
256 *
257 * return true if parent was changed, 0 if unchanged, <0 on error.
258 *
259 * caller must hold snap_rwsem for write.
260 */
261static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
262 struct ceph_snap_realm *realm,
263 u64 parentino)
264{
265 struct ceph_snap_realm *parent;
266
267 if (realm->parent_ino == parentino)
268 return 0;
269
270 parent = ceph_lookup_snap_realm(mdsc, parentino);
271 if (!parent) {
272 parent = ceph_create_snap_realm(mdsc, parentino);
273 if (IS_ERR(parent))
274 return PTR_ERR(parent);
275 }
276 dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
277 realm->ino, realm, realm->parent_ino, realm->parent,
278 parentino, parent);
279 if (realm->parent) {
280 list_del_init(&realm->child_item);
281 ceph_put_snap_realm(mdsc, realm->parent);
282 }
283 realm->parent_ino = parentino;
284 realm->parent = parent;
285 list_add(&realm->child_item, &parent->children);
286 return 1;
287}
288
289
290static int cmpu64_rev(const void *a, const void *b)
291{
292 if (*(u64 *)a < *(u64 *)b)
293 return 1;
294 if (*(u64 *)a > *(u64 *)b)
295 return -1;
296 return 0;
297}
298
299
300/*
301 * build the snap context for a given realm.
302 */
303static int build_snap_context(struct ceph_snap_realm *realm,
304 struct list_head* dirty_realms)
305{
306 struct ceph_snap_realm *parent = realm->parent;
307 struct ceph_snap_context *snapc;
308 int err = 0;
309 u32 num = realm->num_prior_parent_snaps + realm->num_snaps;
310
311 /*
312 * build parent context, if it hasn't been built.
313 * conservatively estimate that all parent snaps might be
314 * included by us.
315 */
316 if (parent) {
317 if (!parent->cached_context) {
318 err = build_snap_context(parent, dirty_realms);
319 if (err)
320 goto fail;
321 }
322 num += parent->cached_context->num_snaps;
323 }
324
325 /* do i actually need to update? not if my context seq
326 matches realm seq, and my parents' does to. (this works
327 because we rebuild_snap_realms() works _downward_ in
328 hierarchy after each update.) */
329 if (realm->cached_context &&
330 realm->cached_context->seq == realm->seq &&
331 (!parent ||
332 realm->cached_context->seq >= parent->cached_context->seq)) {
333 dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
334 " (unchanged)\n",
335 realm->ino, realm, realm->cached_context,
336 realm->cached_context->seq,
337 (unsigned int)realm->cached_context->num_snaps);
338 return 0;
339 }
340
341 /* alloc new snap context */
342 err = -ENOMEM;
343 if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
344 goto fail;
345 snapc = ceph_create_snap_context(num, GFP_NOFS);
346 if (!snapc)
347 goto fail;
348
349 /* build (reverse sorted) snap vector */
350 num = 0;
351 snapc->seq = realm->seq;
352 if (parent) {
353 u32 i;
354
355 /* include any of parent's snaps occurring _after_ my
356 parent became my parent */
357 for (i = 0; i < parent->cached_context->num_snaps; i++)
358 if (parent->cached_context->snaps[i] >=
359 realm->parent_since)
360 snapc->snaps[num++] =
361 parent->cached_context->snaps[i];
362 if (parent->cached_context->seq > snapc->seq)
363 snapc->seq = parent->cached_context->seq;
364 }
365 memcpy(snapc->snaps + num, realm->snaps,
366 sizeof(u64)*realm->num_snaps);
367 num += realm->num_snaps;
368 memcpy(snapc->snaps + num, realm->prior_parent_snaps,
369 sizeof(u64)*realm->num_prior_parent_snaps);
370 num += realm->num_prior_parent_snaps;
371
372 sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
373 snapc->num_snaps = num;
374 dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
375 realm->ino, realm, snapc, snapc->seq,
376 (unsigned int) snapc->num_snaps);
377
378 ceph_put_snap_context(realm->cached_context);
379 realm->cached_context = snapc;
380 /* queue realm for cap_snap creation */
381 list_add_tail(&realm->dirty_item, dirty_realms);
382 return 0;
383
384fail:
385 /*
386 * if we fail, clear old (incorrect) cached_context... hopefully
387 * we'll have better luck building it later
388 */
389 if (realm->cached_context) {
390 ceph_put_snap_context(realm->cached_context);
391 realm->cached_context = NULL;
392 }
393 pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
394 realm, err);
395 return err;
396}
397
398/*
399 * rebuild snap context for the given realm and all of its children.
400 */
401static void rebuild_snap_realms(struct ceph_snap_realm *realm,
402 struct list_head *dirty_realms)
403{
404 struct ceph_snap_realm *child;
405
406 dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
407 build_snap_context(realm, dirty_realms);
408
409 list_for_each_entry(child, &realm->children, child_item)
410 rebuild_snap_realms(child, dirty_realms);
411}
412
413
414/*
415 * helper to allocate and decode an array of snapids. free prior
416 * instance, if any.
417 */
418static int dup_array(u64 **dst, __le64 *src, u32 num)
419{
420 u32 i;
421
422 kfree(*dst);
423 if (num) {
424 *dst = kcalloc(num, sizeof(u64), GFP_NOFS);
425 if (!*dst)
426 return -ENOMEM;
427 for (i = 0; i < num; i++)
428 (*dst)[i] = get_unaligned_le64(src + i);
429 } else {
430 *dst = NULL;
431 }
432 return 0;
433}
434
435static bool has_new_snaps(struct ceph_snap_context *o,
436 struct ceph_snap_context *n)
437{
438 if (n->num_snaps == 0)
439 return false;
440 /* snaps are in descending order */
441 return n->snaps[0] > o->seq;
442}
443
444/*
445 * When a snapshot is applied, the size/mtime inode metadata is queued
446 * in a ceph_cap_snap (one for each snapshot) until writeback
447 * completes and the metadata can be flushed back to the MDS.
448 *
449 * However, if a (sync) write is currently in-progress when we apply
450 * the snapshot, we have to wait until the write succeeds or fails
451 * (and a final size/mtime is known). In this case the
452 * cap_snap->writing = 1, and is said to be "pending." When the write
453 * finishes, we __ceph_finish_cap_snap().
454 *
455 * Caller must hold snap_rwsem for read (i.e., the realm topology won't
456 * change).
457 */
458void ceph_queue_cap_snap(struct ceph_inode_info *ci)
459{
460 struct inode *inode = &ci->vfs_inode;
461 struct ceph_cap_snap *capsnap;
462 struct ceph_snap_context *old_snapc, *new_snapc;
463 int used, dirty;
464
465 capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
466 if (!capsnap) {
467 pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
468 return;
469 }
470
471 spin_lock(&ci->i_ceph_lock);
472 used = __ceph_caps_used(ci);
473 dirty = __ceph_caps_dirty(ci);
474
475 old_snapc = ci->i_head_snapc;
476 new_snapc = ci->i_snap_realm->cached_context;
477
478 /*
479 * If there is a write in progress, treat that as a dirty Fw,
480 * even though it hasn't completed yet; by the time we finish
481 * up this capsnap it will be.
482 */
483 if (used & CEPH_CAP_FILE_WR)
484 dirty |= CEPH_CAP_FILE_WR;
485
486 if (__ceph_have_pending_cap_snap(ci)) {
487 /* there is no point in queuing multiple "pending" cap_snaps,
488 as no new writes are allowed to start when pending, so any
489 writes in progress now were started before the previous
490 cap_snap. lucky us. */
491 dout("queue_cap_snap %p already pending\n", inode);
492 goto update_snapc;
493 }
494 if (ci->i_wrbuffer_ref_head == 0 &&
495 !(dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))) {
496 dout("queue_cap_snap %p nothing dirty|writing\n", inode);
497 goto update_snapc;
498 }
499
500 BUG_ON(!old_snapc);
501
502 /*
503 * There is no need to send FLUSHSNAP message to MDS if there is
504 * no new snapshot. But when there is dirty pages or on-going
505 * writes, we still need to create cap_snap. cap_snap is needed
506 * by the write path and page writeback path.
507 *
508 * also see ceph_try_drop_cap_snap()
509 */
510 if (has_new_snaps(old_snapc, new_snapc)) {
511 if (dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))
512 capsnap->need_flush = true;
513 } else {
514 if (!(used & CEPH_CAP_FILE_WR) &&
515 ci->i_wrbuffer_ref_head == 0) {
516 dout("queue_cap_snap %p "
517 "no new_snap|dirty_page|writing\n", inode);
518 goto update_snapc;
519 }
520 }
521
522 dout("queue_cap_snap %p cap_snap %p queuing under %p %s %s\n",
523 inode, capsnap, old_snapc, ceph_cap_string(dirty),
524 capsnap->need_flush ? "" : "no_flush");
525 ihold(inode);
526
527 refcount_set(&capsnap->nref, 1);
528 INIT_LIST_HEAD(&capsnap->ci_item);
529
530 capsnap->follows = old_snapc->seq;
531 capsnap->issued = __ceph_caps_issued(ci, NULL);
532 capsnap->dirty = dirty;
533
534 capsnap->mode = inode->i_mode;
535 capsnap->uid = inode->i_uid;
536 capsnap->gid = inode->i_gid;
537
538 if (dirty & CEPH_CAP_XATTR_EXCL) {
539 __ceph_build_xattrs_blob(ci);
540 capsnap->xattr_blob =
541 ceph_buffer_get(ci->i_xattrs.blob);
542 capsnap->xattr_version = ci->i_xattrs.version;
543 } else {
544 capsnap->xattr_blob = NULL;
545 capsnap->xattr_version = 0;
546 }
547
548 capsnap->inline_data = ci->i_inline_version != CEPH_INLINE_NONE;
549
550 /* dirty page count moved from _head to this cap_snap;
551 all subsequent writes page dirties occur _after_ this
552 snapshot. */
553 capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
554 ci->i_wrbuffer_ref_head = 0;
555 capsnap->context = old_snapc;
556 list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
557
558 if (used & CEPH_CAP_FILE_WR) {
559 dout("queue_cap_snap %p cap_snap %p snapc %p"
560 " seq %llu used WR, now pending\n", inode,
561 capsnap, old_snapc, old_snapc->seq);
562 capsnap->writing = 1;
563 } else {
564 /* note mtime, size NOW. */
565 __ceph_finish_cap_snap(ci, capsnap);
566 }
567 capsnap = NULL;
568 old_snapc = NULL;
569
570update_snapc:
571 if (ci->i_head_snapc) {
572 ci->i_head_snapc = ceph_get_snap_context(new_snapc);
573 dout(" new snapc is %p\n", new_snapc);
574 }
575 spin_unlock(&ci->i_ceph_lock);
576
577 kfree(capsnap);
578 ceph_put_snap_context(old_snapc);
579}
580
581/*
582 * Finalize the size, mtime for a cap_snap.. that is, settle on final values
583 * to be used for the snapshot, to be flushed back to the mds.
584 *
585 * If capsnap can now be flushed, add to snap_flush list, and return 1.
586 *
587 * Caller must hold i_ceph_lock.
588 */
589int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
590 struct ceph_cap_snap *capsnap)
591{
592 struct inode *inode = &ci->vfs_inode;
593 struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
594
595 BUG_ON(capsnap->writing);
596 capsnap->size = inode->i_size;
597 capsnap->mtime = inode->i_mtime;
598 capsnap->atime = inode->i_atime;
599 capsnap->ctime = inode->i_ctime;
600 capsnap->time_warp_seq = ci->i_time_warp_seq;
601 capsnap->truncate_size = ci->i_truncate_size;
602 capsnap->truncate_seq = ci->i_truncate_seq;
603 if (capsnap->dirty_pages) {
604 dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
605 "still has %d dirty pages\n", inode, capsnap,
606 capsnap->context, capsnap->context->seq,
607 ceph_cap_string(capsnap->dirty), capsnap->size,
608 capsnap->dirty_pages);
609 return 0;
610 }
611
612 ci->i_ceph_flags |= CEPH_I_FLUSH_SNAPS;
613 dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
614 inode, capsnap, capsnap->context,
615 capsnap->context->seq, ceph_cap_string(capsnap->dirty),
616 capsnap->size);
617
618 spin_lock(&mdsc->snap_flush_lock);
619 list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
620 spin_unlock(&mdsc->snap_flush_lock);
621 return 1; /* caller may want to ceph_flush_snaps */
622}
623
624/*
625 * Queue cap_snaps for snap writeback for this realm and its children.
626 * Called under snap_rwsem, so realm topology won't change.
627 */
628static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
629{
630 struct ceph_inode_info *ci;
631 struct inode *lastinode = NULL;
632
633 dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);
634
635 spin_lock(&realm->inodes_with_caps_lock);
636 list_for_each_entry(ci, &realm->inodes_with_caps, i_snap_realm_item) {
637 struct inode *inode = igrab(&ci->vfs_inode);
638 if (!inode)
639 continue;
640 spin_unlock(&realm->inodes_with_caps_lock);
641 iput(lastinode);
642 lastinode = inode;
643 ceph_queue_cap_snap(ci);
644 spin_lock(&realm->inodes_with_caps_lock);
645 }
646 spin_unlock(&realm->inodes_with_caps_lock);
647 iput(lastinode);
648
649 dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
650}
651
652/*
653 * Parse and apply a snapblob "snap trace" from the MDS. This specifies
654 * the snap realm parameters from a given realm and all of its ancestors,
655 * up to the root.
656 *
657 * Caller must hold snap_rwsem for write.
658 */
659int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
660 void *p, void *e, bool deletion,
661 struct ceph_snap_realm **realm_ret)
662{
663 struct ceph_mds_snap_realm *ri; /* encoded */
664 __le64 *snaps; /* encoded */
665 __le64 *prior_parent_snaps; /* encoded */
666 struct ceph_snap_realm *realm = NULL;
667 struct ceph_snap_realm *first_realm = NULL;
668 int invalidate = 0;
669 int err = -ENOMEM;
670 LIST_HEAD(dirty_realms);
671
672 dout("update_snap_trace deletion=%d\n", deletion);
673more:
674 ceph_decode_need(&p, e, sizeof(*ri), bad);
675 ri = p;
676 p += sizeof(*ri);
677 ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) +
678 le32_to_cpu(ri->num_prior_parent_snaps)), bad);
679 snaps = p;
680 p += sizeof(u64) * le32_to_cpu(ri->num_snaps);
681 prior_parent_snaps = p;
682 p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps);
683
684 realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino));
685 if (!realm) {
686 realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino));
687 if (IS_ERR(realm)) {
688 err = PTR_ERR(realm);
689 goto fail;
690 }
691 }
692
693 /* ensure the parent is correct */
694 err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
695 if (err < 0)
696 goto fail;
697 invalidate += err;
698
699 if (le64_to_cpu(ri->seq) > realm->seq) {
700 dout("update_snap_trace updating %llx %p %lld -> %lld\n",
701 realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
702 /* update realm parameters, snap lists */
703 realm->seq = le64_to_cpu(ri->seq);
704 realm->created = le64_to_cpu(ri->created);
705 realm->parent_since = le64_to_cpu(ri->parent_since);
706
707 realm->num_snaps = le32_to_cpu(ri->num_snaps);
708 err = dup_array(&realm->snaps, snaps, realm->num_snaps);
709 if (err < 0)
710 goto fail;
711
712 realm->num_prior_parent_snaps =
713 le32_to_cpu(ri->num_prior_parent_snaps);
714 err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps,
715 realm->num_prior_parent_snaps);
716 if (err < 0)
717 goto fail;
718
719 if (realm->seq > mdsc->last_snap_seq)
720 mdsc->last_snap_seq = realm->seq;
721
722 invalidate = 1;
723 } else if (!realm->cached_context) {
724 dout("update_snap_trace %llx %p seq %lld new\n",
725 realm->ino, realm, realm->seq);
726 invalidate = 1;
727 } else {
728 dout("update_snap_trace %llx %p seq %lld unchanged\n",
729 realm->ino, realm, realm->seq);
730 }
731
732 dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
733 realm, invalidate, p, e);
734
735 /* invalidate when we reach the _end_ (root) of the trace */
736 if (invalidate && p >= e)
737 rebuild_snap_realms(realm, &dirty_realms);
738
739 if (!first_realm)
740 first_realm = realm;
741 else
742 ceph_put_snap_realm(mdsc, realm);
743
744 if (p < e)
745 goto more;
746
747 /*
748 * queue cap snaps _after_ we've built the new snap contexts,
749 * so that i_head_snapc can be set appropriately.
750 */
751 while (!list_empty(&dirty_realms)) {
752 realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
753 dirty_item);
754 list_del_init(&realm->dirty_item);
755 queue_realm_cap_snaps(realm);
756 }
757
758 if (realm_ret)
759 *realm_ret = first_realm;
760 else
761 ceph_put_snap_realm(mdsc, first_realm);
762
763 __cleanup_empty_realms(mdsc);
764 return 0;
765
766bad:
767 err = -EINVAL;
768fail:
769 if (realm && !IS_ERR(realm))
770 ceph_put_snap_realm(mdsc, realm);
771 if (first_realm)
772 ceph_put_snap_realm(mdsc, first_realm);
773 pr_err("update_snap_trace error %d\n", err);
774 return err;
775}
776
777
778/*
779 * Send any cap_snaps that are queued for flush. Try to carry
780 * s_mutex across multiple snap flushes to avoid locking overhead.
781 *
782 * Caller holds no locks.
783 */
784static void flush_snaps(struct ceph_mds_client *mdsc)
785{
786 struct ceph_inode_info *ci;
787 struct inode *inode;
788 struct ceph_mds_session *session = NULL;
789
790 dout("flush_snaps\n");
791 spin_lock(&mdsc->snap_flush_lock);
792 while (!list_empty(&mdsc->snap_flush_list)) {
793 ci = list_first_entry(&mdsc->snap_flush_list,
794 struct ceph_inode_info, i_snap_flush_item);
795 inode = &ci->vfs_inode;
796 ihold(inode);
797 spin_unlock(&mdsc->snap_flush_lock);
798 ceph_flush_snaps(ci, &session);
799 iput(inode);
800 spin_lock(&mdsc->snap_flush_lock);
801 }
802 spin_unlock(&mdsc->snap_flush_lock);
803
804 if (session) {
805 mutex_unlock(&session->s_mutex);
806 ceph_put_mds_session(session);
807 }
808 dout("flush_snaps done\n");
809}
810
811
812/*
813 * Handle a snap notification from the MDS.
814 *
815 * This can take two basic forms: the simplest is just a snap creation
816 * or deletion notification on an existing realm. This should update the
817 * realm and its children.
818 *
819 * The more difficult case is realm creation, due to snap creation at a
820 * new point in the file hierarchy, or due to a rename that moves a file or
821 * directory into another realm.
822 */
823void ceph_handle_snap(struct ceph_mds_client *mdsc,
824 struct ceph_mds_session *session,
825 struct ceph_msg *msg)
826{
827 struct super_block *sb = mdsc->fsc->sb;
828 int mds = session->s_mds;
829 u64 split;
830 int op;
831 int trace_len;
832 struct ceph_snap_realm *realm = NULL;
833 void *p = msg->front.iov_base;
834 void *e = p + msg->front.iov_len;
835 struct ceph_mds_snap_head *h;
836 int num_split_inos, num_split_realms;
837 __le64 *split_inos = NULL, *split_realms = NULL;
838 int i;
839 int locked_rwsem = 0;
840
841 /* decode */
842 if (msg->front.iov_len < sizeof(*h))
843 goto bad;
844 h = p;
845 op = le32_to_cpu(h->op);
846 split = le64_to_cpu(h->split); /* non-zero if we are splitting an
847 * existing realm */
848 num_split_inos = le32_to_cpu(h->num_split_inos);
849 num_split_realms = le32_to_cpu(h->num_split_realms);
850 trace_len = le32_to_cpu(h->trace_len);
851 p += sizeof(*h);
852
853 dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
854 ceph_snap_op_name(op), split, trace_len);
855
856 mutex_lock(&session->s_mutex);
857 session->s_seq++;
858 mutex_unlock(&session->s_mutex);
859
860 down_write(&mdsc->snap_rwsem);
861 locked_rwsem = 1;
862
863 if (op == CEPH_SNAP_OP_SPLIT) {
864 struct ceph_mds_snap_realm *ri;
865
866 /*
867 * A "split" breaks part of an existing realm off into
868 * a new realm. The MDS provides a list of inodes
869 * (with caps) and child realms that belong to the new
870 * child.
871 */
872 split_inos = p;
873 p += sizeof(u64) * num_split_inos;
874 split_realms = p;
875 p += sizeof(u64) * num_split_realms;
876 ceph_decode_need(&p, e, sizeof(*ri), bad);
877 /* we will peek at realm info here, but will _not_
878 * advance p, as the realm update will occur below in
879 * ceph_update_snap_trace. */
880 ri = p;
881
882 realm = ceph_lookup_snap_realm(mdsc, split);
883 if (!realm) {
884 realm = ceph_create_snap_realm(mdsc, split);
885 if (IS_ERR(realm))
886 goto out;
887 }
888
889 dout("splitting snap_realm %llx %p\n", realm->ino, realm);
890 for (i = 0; i < num_split_inos; i++) {
891 struct ceph_vino vino = {
892 .ino = le64_to_cpu(split_inos[i]),
893 .snap = CEPH_NOSNAP,
894 };
895 struct inode *inode = ceph_find_inode(sb, vino);
896 struct ceph_inode_info *ci;
897 struct ceph_snap_realm *oldrealm;
898
899 if (!inode)
900 continue;
901 ci = ceph_inode(inode);
902
903 spin_lock(&ci->i_ceph_lock);
904 if (!ci->i_snap_realm)
905 goto skip_inode;
906 /*
907 * If this inode belongs to a realm that was
908 * created after our new realm, we experienced
909 * a race (due to another split notifications
910 * arriving from a different MDS). So skip
911 * this inode.
912 */
913 if (ci->i_snap_realm->created >
914 le64_to_cpu(ri->created)) {
915 dout(" leaving %p in newer realm %llx %p\n",
916 inode, ci->i_snap_realm->ino,
917 ci->i_snap_realm);
918 goto skip_inode;
919 }
920 dout(" will move %p to split realm %llx %p\n",
921 inode, realm->ino, realm);
922 /*
923 * Move the inode to the new realm
924 */
925 oldrealm = ci->i_snap_realm;
926 spin_lock(&oldrealm->inodes_with_caps_lock);
927 list_del_init(&ci->i_snap_realm_item);
928 spin_unlock(&oldrealm->inodes_with_caps_lock);
929
930 spin_lock(&realm->inodes_with_caps_lock);
931 list_add(&ci->i_snap_realm_item,
932 &realm->inodes_with_caps);
933 ci->i_snap_realm = realm;
934 if (realm->ino == ci->i_vino.ino)
935 realm->inode = inode;
936 spin_unlock(&realm->inodes_with_caps_lock);
937
938 spin_unlock(&ci->i_ceph_lock);
939
940 ceph_get_snap_realm(mdsc, realm);
941 ceph_put_snap_realm(mdsc, oldrealm);
942
943 iput(inode);
944 continue;
945
946skip_inode:
947 spin_unlock(&ci->i_ceph_lock);
948 iput(inode);
949 }
950
951 /* we may have taken some of the old realm's children. */
952 for (i = 0; i < num_split_realms; i++) {
953 struct ceph_snap_realm *child =
954 __lookup_snap_realm(mdsc,
955 le64_to_cpu(split_realms[i]));
956 if (!child)
957 continue;
958 adjust_snap_realm_parent(mdsc, child, realm->ino);
959 }
960 }
961
962 /*
963 * update using the provided snap trace. if we are deleting a
964 * snap, we can avoid queueing cap_snaps.
965 */
966 ceph_update_snap_trace(mdsc, p, e,
967 op == CEPH_SNAP_OP_DESTROY, NULL);
968
969 if (op == CEPH_SNAP_OP_SPLIT)
970 /* we took a reference when we created the realm, above */
971 ceph_put_snap_realm(mdsc, realm);
972
973 __cleanup_empty_realms(mdsc);
974
975 up_write(&mdsc->snap_rwsem);
976
977 flush_snaps(mdsc);
978 return;
979
980bad:
981 pr_err("corrupt snap message from mds%d\n", mds);
982 ceph_msg_dump(msg);
983out:
984 if (locked_rwsem)
985 up_write(&mdsc->snap_rwsem);
986 return;
987}