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TOMOYO Linux Cross Reference
Linux/fs/ceph/snap.c

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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  */
 62 void 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 
 80 static 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  */
107 static 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  */
135 static 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 
155 struct 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 
165 static void __put_snap_realm(struct ceph_mds_client *mdsc,
166                              struct ceph_snap_realm *realm);
167 
168 /*
169  * called with snap_rwsem (write)
170  */
171 static 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  */
192 static 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  */
204 void 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  */
229 static 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 
245 void 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  */
260 static 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 
289 static 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  */
302 static 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 
380 fail:
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  */
397 static 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  */
413 static 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 
430 static 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  */
453 void 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 
567 update_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  */
586 int __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  */
621 static 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  */
662 int 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);
676 more:
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 
770 bad:
771         err = -EINVAL;
772 fail:
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  */
788 static 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  */
829 void 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 
946 skip_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 
980 bad:
981         pr_err("corrupt snap message from mds%d\n", mds);
982         ceph_msg_dump(msg);
983 out:
984         if (locked_rwsem)
985                 up_write(&mdsc->snap_rwsem);
986         return;
987 }
988 

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