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

Version: ~ [ linux-5.2 ] ~ [ linux-5.1.16 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.57 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.132 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.184 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.184 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.69 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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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_read(&realm->nref) == 0) {
 74                 spin_lock(&mdsc->snap_empty_lock);
 75                 list_del_init(&realm->empty_item);
 76                 spin_unlock(&mdsc->snap_empty_lock);
 77         }
 78 
 79         atomic_inc(&realm->nref);
 80 }
 81 
 82 static void __insert_snap_realm(struct rb_root *root,
 83                                 struct ceph_snap_realm *new)
 84 {
 85         struct rb_node **p = &root->rb_node;
 86         struct rb_node *parent = NULL;
 87         struct ceph_snap_realm *r = NULL;
 88 
 89         while (*p) {
 90                 parent = *p;
 91                 r = rb_entry(parent, struct ceph_snap_realm, node);
 92                 if (new->ino < r->ino)
 93                         p = &(*p)->rb_left;
 94                 else if (new->ino > r->ino)
 95                         p = &(*p)->rb_right;
 96                 else
 97                         BUG();
 98         }
 99 
100         rb_link_node(&new->node, parent, p);
101         rb_insert_color(&new->node, root);
102 }
103 
104 /*
105  * create and get the realm rooted at @ino and bump its ref count.
106  *
107  * caller must hold snap_rwsem for write.
108  */
109 static struct ceph_snap_realm *ceph_create_snap_realm(
110         struct ceph_mds_client *mdsc,
111         u64 ino)
112 {
113         struct ceph_snap_realm *realm;
114 
115         realm = kzalloc(sizeof(*realm), GFP_NOFS);
116         if (!realm)
117                 return ERR_PTR(-ENOMEM);
118 
119         atomic_set(&realm->nref, 0);    /* tree does not take a ref */
120         realm->ino = ino;
121         INIT_LIST_HEAD(&realm->children);
122         INIT_LIST_HEAD(&realm->child_item);
123         INIT_LIST_HEAD(&realm->empty_item);
124         INIT_LIST_HEAD(&realm->dirty_item);
125         INIT_LIST_HEAD(&realm->inodes_with_caps);
126         spin_lock_init(&realm->inodes_with_caps_lock);
127         __insert_snap_realm(&mdsc->snap_realms, realm);
128         dout("create_snap_realm %llx %p\n", realm->ino, realm);
129         return realm;
130 }
131 
132 /*
133  * lookup the realm rooted at @ino.
134  *
135  * caller must hold snap_rwsem for write.
136  */
137 struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc,
138                                                u64 ino)
139 {
140         struct rb_node *n = mdsc->snap_realms.rb_node;
141         struct ceph_snap_realm *r;
142 
143         while (n) {
144                 r = rb_entry(n, struct ceph_snap_realm, node);
145                 if (ino < r->ino)
146                         n = n->rb_left;
147                 else if (ino > r->ino)
148                         n = n->rb_right;
149                 else {
150                         dout("lookup_snap_realm %llx %p\n", r->ino, r);
151                         return r;
152                 }
153         }
154         return NULL;
155 }
156 
157 static void __put_snap_realm(struct ceph_mds_client *mdsc,
158                              struct ceph_snap_realm *realm);
159 
160 /*
161  * called with snap_rwsem (write)
162  */
163 static void __destroy_snap_realm(struct ceph_mds_client *mdsc,
164                                  struct ceph_snap_realm *realm)
165 {
166         dout("__destroy_snap_realm %p %llx\n", realm, realm->ino);
167 
168         rb_erase(&realm->node, &mdsc->snap_realms);
169 
170         if (realm->parent) {
171                 list_del_init(&realm->child_item);
172                 __put_snap_realm(mdsc, realm->parent);
173         }
174 
175         kfree(realm->prior_parent_snaps);
176         kfree(realm->snaps);
177         ceph_put_snap_context(realm->cached_context);
178         kfree(realm);
179 }
180 
181 /*
182  * caller holds snap_rwsem (write)
183  */
184 static void __put_snap_realm(struct ceph_mds_client *mdsc,
185                              struct ceph_snap_realm *realm)
186 {
187         dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
188              atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
189         if (atomic_dec_and_test(&realm->nref))
190                 __destroy_snap_realm(mdsc, realm);
191 }
192 
193 /*
194  * caller needn't hold any locks
195  */
196 void ceph_put_snap_realm(struct ceph_mds_client *mdsc,
197                          struct ceph_snap_realm *realm)
198 {
199         dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm,
200              atomic_read(&realm->nref), atomic_read(&realm->nref)-1);
201         if (!atomic_dec_and_test(&realm->nref))
202                 return;
203 
204         if (down_write_trylock(&mdsc->snap_rwsem)) {
205                 __destroy_snap_realm(mdsc, realm);
206                 up_write(&mdsc->snap_rwsem);
207         } else {
208                 spin_lock(&mdsc->snap_empty_lock);
209                 list_add(&realm->empty_item, &mdsc->snap_empty);
210                 spin_unlock(&mdsc->snap_empty_lock);
211         }
212 }
213 
214 /*
215  * Clean up any realms whose ref counts have dropped to zero.  Note
216  * that this does not include realms who were created but not yet
217  * used.
218  *
219  * Called under snap_rwsem (write)
220  */
221 static void __cleanup_empty_realms(struct ceph_mds_client *mdsc)
222 {
223         struct ceph_snap_realm *realm;
224 
225         spin_lock(&mdsc->snap_empty_lock);
226         while (!list_empty(&mdsc->snap_empty)) {
227                 realm = list_first_entry(&mdsc->snap_empty,
228                                    struct ceph_snap_realm, empty_item);
229                 list_del(&realm->empty_item);
230                 spin_unlock(&mdsc->snap_empty_lock);
231                 __destroy_snap_realm(mdsc, realm);
232                 spin_lock(&mdsc->snap_empty_lock);
233         }
234         spin_unlock(&mdsc->snap_empty_lock);
235 }
236 
237 void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc)
238 {
239         down_write(&mdsc->snap_rwsem);
240         __cleanup_empty_realms(mdsc);
241         up_write(&mdsc->snap_rwsem);
242 }
243 
244 /*
245  * adjust the parent realm of a given @realm.  adjust child list, and parent
246  * pointers, and ref counts appropriately.
247  *
248  * return true if parent was changed, 0 if unchanged, <0 on error.
249  *
250  * caller must hold snap_rwsem for write.
251  */
252 static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc,
253                                     struct ceph_snap_realm *realm,
254                                     u64 parentino)
255 {
256         struct ceph_snap_realm *parent;
257 
258         if (realm->parent_ino == parentino)
259                 return 0;
260 
261         parent = ceph_lookup_snap_realm(mdsc, parentino);
262         if (!parent) {
263                 parent = ceph_create_snap_realm(mdsc, parentino);
264                 if (IS_ERR(parent))
265                         return PTR_ERR(parent);
266         }
267         dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n",
268              realm->ino, realm, realm->parent_ino, realm->parent,
269              parentino, parent);
270         if (realm->parent) {
271                 list_del_init(&realm->child_item);
272                 ceph_put_snap_realm(mdsc, realm->parent);
273         }
274         realm->parent_ino = parentino;
275         realm->parent = parent;
276         ceph_get_snap_realm(mdsc, parent);
277         list_add(&realm->child_item, &parent->children);
278         return 1;
279 }
280 
281 
282 static int cmpu64_rev(const void *a, const void *b)
283 {
284         if (*(u64 *)a < *(u64 *)b)
285                 return 1;
286         if (*(u64 *)a > *(u64 *)b)
287                 return -1;
288         return 0;
289 }
290 
291 /*
292  * build the snap context for a given realm.
293  */
294 static int build_snap_context(struct ceph_snap_realm *realm)
295 {
296         struct ceph_snap_realm *parent = realm->parent;
297         struct ceph_snap_context *snapc;
298         int err = 0;
299         u32 num = realm->num_prior_parent_snaps + realm->num_snaps;
300 
301         /*
302          * build parent context, if it hasn't been built.
303          * conservatively estimate that all parent snaps might be
304          * included by us.
305          */
306         if (parent) {
307                 if (!parent->cached_context) {
308                         err = build_snap_context(parent);
309                         if (err)
310                                 goto fail;
311                 }
312                 num += parent->cached_context->num_snaps;
313         }
314 
315         /* do i actually need to update?  not if my context seq
316            matches realm seq, and my parents' does to.  (this works
317            because we rebuild_snap_realms() works _downward_ in
318            hierarchy after each update.) */
319         if (realm->cached_context &&
320             realm->cached_context->seq == realm->seq &&
321             (!parent ||
322              realm->cached_context->seq >= parent->cached_context->seq)) {
323                 dout("build_snap_context %llx %p: %p seq %lld (%u snaps)"
324                      " (unchanged)\n",
325                      realm->ino, realm, realm->cached_context,
326                      realm->cached_context->seq,
327                      (unsigned int) realm->cached_context->num_snaps);
328                 return 0;
329         }
330 
331         /* alloc new snap context */
332         err = -ENOMEM;
333         if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
334                 goto fail;
335         snapc = ceph_create_snap_context(num, GFP_NOFS);
336         if (!snapc)
337                 goto fail;
338 
339         /* build (reverse sorted) snap vector */
340         num = 0;
341         snapc->seq = realm->seq;
342         if (parent) {
343                 u32 i;
344 
345                 /* include any of parent's snaps occurring _after_ my
346                    parent became my parent */
347                 for (i = 0; i < parent->cached_context->num_snaps; i++)
348                         if (parent->cached_context->snaps[i] >=
349                             realm->parent_since)
350                                 snapc->snaps[num++] =
351                                         parent->cached_context->snaps[i];
352                 if (parent->cached_context->seq > snapc->seq)
353                         snapc->seq = parent->cached_context->seq;
354         }
355         memcpy(snapc->snaps + num, realm->snaps,
356                sizeof(u64)*realm->num_snaps);
357         num += realm->num_snaps;
358         memcpy(snapc->snaps + num, realm->prior_parent_snaps,
359                sizeof(u64)*realm->num_prior_parent_snaps);
360         num += realm->num_prior_parent_snaps;
361 
362         sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL);
363         snapc->num_snaps = num;
364         dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n",
365              realm->ino, realm, snapc, snapc->seq,
366              (unsigned int) snapc->num_snaps);
367 
368         if (realm->cached_context)
369                 ceph_put_snap_context(realm->cached_context);
370         realm->cached_context = snapc;
371         return 0;
372 
373 fail:
374         /*
375          * if we fail, clear old (incorrect) cached_context... hopefully
376          * we'll have better luck building it later
377          */
378         if (realm->cached_context) {
379                 ceph_put_snap_context(realm->cached_context);
380                 realm->cached_context = NULL;
381         }
382         pr_err("build_snap_context %llx %p fail %d\n", realm->ino,
383                realm, err);
384         return err;
385 }
386 
387 /*
388  * rebuild snap context for the given realm and all of its children.
389  */
390 static void rebuild_snap_realms(struct ceph_snap_realm *realm)
391 {
392         struct ceph_snap_realm *child;
393 
394         dout("rebuild_snap_realms %llx %p\n", realm->ino, realm);
395         build_snap_context(realm);
396 
397         list_for_each_entry(child, &realm->children, child_item)
398                 rebuild_snap_realms(child);
399 }
400 
401 
402 /*
403  * helper to allocate and decode an array of snapids.  free prior
404  * instance, if any.
405  */
406 static int dup_array(u64 **dst, __le64 *src, u32 num)
407 {
408         u32 i;
409 
410         kfree(*dst);
411         if (num) {
412                 *dst = kcalloc(num, sizeof(u64), GFP_NOFS);
413                 if (!*dst)
414                         return -ENOMEM;
415                 for (i = 0; i < num; i++)
416                         (*dst)[i] = get_unaligned_le64(src + i);
417         } else {
418                 *dst = NULL;
419         }
420         return 0;
421 }
422 
423 
424 /*
425  * When a snapshot is applied, the size/mtime inode metadata is queued
426  * in a ceph_cap_snap (one for each snapshot) until writeback
427  * completes and the metadata can be flushed back to the MDS.
428  *
429  * However, if a (sync) write is currently in-progress when we apply
430  * the snapshot, we have to wait until the write succeeds or fails
431  * (and a final size/mtime is known).  In this case the
432  * cap_snap->writing = 1, and is said to be "pending."  When the write
433  * finishes, we __ceph_finish_cap_snap().
434  *
435  * Caller must hold snap_rwsem for read (i.e., the realm topology won't
436  * change).
437  */
438 void ceph_queue_cap_snap(struct ceph_inode_info *ci)
439 {
440         struct inode *inode = &ci->vfs_inode;
441         struct ceph_cap_snap *capsnap;
442         int used, dirty;
443 
444         capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
445         if (!capsnap) {
446                 pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode);
447                 return;
448         }
449 
450         spin_lock(&ci->i_ceph_lock);
451         used = __ceph_caps_used(ci);
452         dirty = __ceph_caps_dirty(ci);
453 
454         /*
455          * If there is a write in progress, treat that as a dirty Fw,
456          * even though it hasn't completed yet; by the time we finish
457          * up this capsnap it will be.
458          */
459         if (used & CEPH_CAP_FILE_WR)
460                 dirty |= CEPH_CAP_FILE_WR;
461 
462         if (__ceph_have_pending_cap_snap(ci)) {
463                 /* there is no point in queuing multiple "pending" cap_snaps,
464                    as no new writes are allowed to start when pending, so any
465                    writes in progress now were started before the previous
466                    cap_snap.  lucky us. */
467                 dout("queue_cap_snap %p already pending\n", inode);
468                 kfree(capsnap);
469         } else if (dirty & (CEPH_CAP_AUTH_EXCL|CEPH_CAP_XATTR_EXCL|
470                             CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR)) {
471                 struct ceph_snap_context *snapc = ci->i_head_snapc;
472 
473                 /*
474                  * if we are a sync write, we may need to go to the snaprealm
475                  * to get the current snapc.
476                  */
477                 if (!snapc)
478                         snapc = ci->i_snap_realm->cached_context;
479 
480                 dout("queue_cap_snap %p cap_snap %p queuing under %p %s\n",
481                      inode, capsnap, snapc, ceph_cap_string(dirty));
482                 ihold(inode);
483 
484                 atomic_set(&capsnap->nref, 1);
485                 capsnap->ci = ci;
486                 INIT_LIST_HEAD(&capsnap->ci_item);
487                 INIT_LIST_HEAD(&capsnap->flushing_item);
488 
489                 capsnap->follows = snapc->seq;
490                 capsnap->issued = __ceph_caps_issued(ci, NULL);
491                 capsnap->dirty = dirty;
492 
493                 capsnap->mode = inode->i_mode;
494                 capsnap->uid = inode->i_uid;
495                 capsnap->gid = inode->i_gid;
496 
497                 if (dirty & CEPH_CAP_XATTR_EXCL) {
498                         __ceph_build_xattrs_blob(ci);
499                         capsnap->xattr_blob =
500                                 ceph_buffer_get(ci->i_xattrs.blob);
501                         capsnap->xattr_version = ci->i_xattrs.version;
502                 } else {
503                         capsnap->xattr_blob = NULL;
504                         capsnap->xattr_version = 0;
505                 }
506 
507                 /* dirty page count moved from _head to this cap_snap;
508                    all subsequent writes page dirties occur _after_ this
509                    snapshot. */
510                 capsnap->dirty_pages = ci->i_wrbuffer_ref_head;
511                 ci->i_wrbuffer_ref_head = 0;
512                 capsnap->context = snapc;
513                 ci->i_head_snapc =
514                         ceph_get_snap_context(ci->i_snap_realm->cached_context);
515                 dout(" new snapc is %p\n", ci->i_head_snapc);
516                 list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps);
517 
518                 if (used & CEPH_CAP_FILE_WR) {
519                         dout("queue_cap_snap %p cap_snap %p snapc %p"
520                              " seq %llu used WR, now pending\n", inode,
521                              capsnap, snapc, snapc->seq);
522                         capsnap->writing = 1;
523                 } else {
524                         /* note mtime, size NOW. */
525                         __ceph_finish_cap_snap(ci, capsnap);
526                 }
527         } else {
528                 dout("queue_cap_snap %p nothing dirty|writing\n", inode);
529                 kfree(capsnap);
530         }
531 
532         spin_unlock(&ci->i_ceph_lock);
533 }
534 
535 /*
536  * Finalize the size, mtime for a cap_snap.. that is, settle on final values
537  * to be used for the snapshot, to be flushed back to the mds.
538  *
539  * If capsnap can now be flushed, add to snap_flush list, and return 1.
540  *
541  * Caller must hold i_ceph_lock.
542  */
543 int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
544                             struct ceph_cap_snap *capsnap)
545 {
546         struct inode *inode = &ci->vfs_inode;
547         struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;
548 
549         BUG_ON(capsnap->writing);
550         capsnap->size = inode->i_size;
551         capsnap->mtime = inode->i_mtime;
552         capsnap->atime = inode->i_atime;
553         capsnap->ctime = inode->i_ctime;
554         capsnap->time_warp_seq = ci->i_time_warp_seq;
555         if (capsnap->dirty_pages) {
556                 dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu "
557                      "still has %d dirty pages\n", inode, capsnap,
558                      capsnap->context, capsnap->context->seq,
559                      ceph_cap_string(capsnap->dirty), capsnap->size,
560                      capsnap->dirty_pages);
561                 return 0;
562         }
563         dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n",
564              inode, capsnap, capsnap->context,
565              capsnap->context->seq, ceph_cap_string(capsnap->dirty),
566              capsnap->size);
567 
568         spin_lock(&mdsc->snap_flush_lock);
569         list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list);
570         spin_unlock(&mdsc->snap_flush_lock);
571         return 1;  /* caller may want to ceph_flush_snaps */
572 }
573 
574 /*
575  * Queue cap_snaps for snap writeback for this realm and its children.
576  * Called under snap_rwsem, so realm topology won't change.
577  */
578 static void queue_realm_cap_snaps(struct ceph_snap_realm *realm)
579 {
580         struct ceph_inode_info *ci;
581         struct inode *lastinode = NULL;
582         struct ceph_snap_realm *child;
583 
584         dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino);
585 
586         spin_lock(&realm->inodes_with_caps_lock);
587         list_for_each_entry(ci, &realm->inodes_with_caps,
588                             i_snap_realm_item) {
589                 struct inode *inode = igrab(&ci->vfs_inode);
590                 if (!inode)
591                         continue;
592                 spin_unlock(&realm->inodes_with_caps_lock);
593                 if (lastinode)
594                         iput(lastinode);
595                 lastinode = inode;
596                 ceph_queue_cap_snap(ci);
597                 spin_lock(&realm->inodes_with_caps_lock);
598         }
599         spin_unlock(&realm->inodes_with_caps_lock);
600         if (lastinode)
601                 iput(lastinode);
602 
603         list_for_each_entry(child, &realm->children, child_item) {
604                 dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n",
605                      realm, realm->ino, child, child->ino);
606                 list_del_init(&child->dirty_item);
607                 list_add(&child->dirty_item, &realm->dirty_item);
608         }
609 
610         list_del_init(&realm->dirty_item);
611         dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
612 }
613 
614 /*
615  * Parse and apply a snapblob "snap trace" from the MDS.  This specifies
616  * the snap realm parameters from a given realm and all of its ancestors,
617  * up to the root.
618  *
619  * Caller must hold snap_rwsem for write.
620  */
621 int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
622                            void *p, void *e, bool deletion)
623 {
624         struct ceph_mds_snap_realm *ri;    /* encoded */
625         __le64 *snaps;                     /* encoded */
626         __le64 *prior_parent_snaps;        /* encoded */
627         struct ceph_snap_realm *realm;
628         int invalidate = 0;
629         int err = -ENOMEM;
630         LIST_HEAD(dirty_realms);
631 
632         dout("update_snap_trace deletion=%d\n", deletion);
633 more:
634         ceph_decode_need(&p, e, sizeof(*ri), bad);
635         ri = p;
636         p += sizeof(*ri);
637         ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) +
638                             le32_to_cpu(ri->num_prior_parent_snaps)), bad);
639         snaps = p;
640         p += sizeof(u64) * le32_to_cpu(ri->num_snaps);
641         prior_parent_snaps = p;
642         p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps);
643 
644         realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino));
645         if (!realm) {
646                 realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino));
647                 if (IS_ERR(realm)) {
648                         err = PTR_ERR(realm);
649                         goto fail;
650                 }
651         }
652 
653         /* ensure the parent is correct */
654         err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent));
655         if (err < 0)
656                 goto fail;
657         invalidate += err;
658 
659         if (le64_to_cpu(ri->seq) > realm->seq) {
660                 dout("update_snap_trace updating %llx %p %lld -> %lld\n",
661                      realm->ino, realm, realm->seq, le64_to_cpu(ri->seq));
662                 /* update realm parameters, snap lists */
663                 realm->seq = le64_to_cpu(ri->seq);
664                 realm->created = le64_to_cpu(ri->created);
665                 realm->parent_since = le64_to_cpu(ri->parent_since);
666 
667                 realm->num_snaps = le32_to_cpu(ri->num_snaps);
668                 err = dup_array(&realm->snaps, snaps, realm->num_snaps);
669                 if (err < 0)
670                         goto fail;
671 
672                 realm->num_prior_parent_snaps =
673                         le32_to_cpu(ri->num_prior_parent_snaps);
674                 err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps,
675                                 realm->num_prior_parent_snaps);
676                 if (err < 0)
677                         goto fail;
678 
679                 /* queue realm for cap_snap creation */
680                 list_add(&realm->dirty_item, &dirty_realms);
681 
682                 invalidate = 1;
683         } else if (!realm->cached_context) {
684                 dout("update_snap_trace %llx %p seq %lld new\n",
685                      realm->ino, realm, realm->seq);
686                 invalidate = 1;
687         } else {
688                 dout("update_snap_trace %llx %p seq %lld unchanged\n",
689                      realm->ino, realm, realm->seq);
690         }
691 
692         dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino,
693              realm, invalidate, p, e);
694 
695         if (p < e)
696                 goto more;
697 
698         /* invalidate when we reach the _end_ (root) of the trace */
699         if (invalidate)
700                 rebuild_snap_realms(realm);
701 
702         /*
703          * queue cap snaps _after_ we've built the new snap contexts,
704          * so that i_head_snapc can be set appropriately.
705          */
706         while (!list_empty(&dirty_realms)) {
707                 realm = list_first_entry(&dirty_realms, struct ceph_snap_realm,
708                                          dirty_item);
709                 queue_realm_cap_snaps(realm);
710         }
711 
712         __cleanup_empty_realms(mdsc);
713         return 0;
714 
715 bad:
716         err = -EINVAL;
717 fail:
718         pr_err("update_snap_trace error %d\n", err);
719         return err;
720 }
721 
722 
723 /*
724  * Send any cap_snaps that are queued for flush.  Try to carry
725  * s_mutex across multiple snap flushes to avoid locking overhead.
726  *
727  * Caller holds no locks.
728  */
729 static void flush_snaps(struct ceph_mds_client *mdsc)
730 {
731         struct ceph_inode_info *ci;
732         struct inode *inode;
733         struct ceph_mds_session *session = NULL;
734 
735         dout("flush_snaps\n");
736         spin_lock(&mdsc->snap_flush_lock);
737         while (!list_empty(&mdsc->snap_flush_list)) {
738                 ci = list_first_entry(&mdsc->snap_flush_list,
739                                 struct ceph_inode_info, i_snap_flush_item);
740                 inode = &ci->vfs_inode;
741                 ihold(inode);
742                 spin_unlock(&mdsc->snap_flush_lock);
743                 spin_lock(&ci->i_ceph_lock);
744                 __ceph_flush_snaps(ci, &session, 0);
745                 spin_unlock(&ci->i_ceph_lock);
746                 iput(inode);
747                 spin_lock(&mdsc->snap_flush_lock);
748         }
749         spin_unlock(&mdsc->snap_flush_lock);
750 
751         if (session) {
752                 mutex_unlock(&session->s_mutex);
753                 ceph_put_mds_session(session);
754         }
755         dout("flush_snaps done\n");
756 }
757 
758 
759 /*
760  * Handle a snap notification from the MDS.
761  *
762  * This can take two basic forms: the simplest is just a snap creation
763  * or deletion notification on an existing realm.  This should update the
764  * realm and its children.
765  *
766  * The more difficult case is realm creation, due to snap creation at a
767  * new point in the file hierarchy, or due to a rename that moves a file or
768  * directory into another realm.
769  */
770 void ceph_handle_snap(struct ceph_mds_client *mdsc,
771                       struct ceph_mds_session *session,
772                       struct ceph_msg *msg)
773 {
774         struct super_block *sb = mdsc->fsc->sb;
775         int mds = session->s_mds;
776         u64 split;
777         int op;
778         int trace_len;
779         struct ceph_snap_realm *realm = NULL;
780         void *p = msg->front.iov_base;
781         void *e = p + msg->front.iov_len;
782         struct ceph_mds_snap_head *h;
783         int num_split_inos, num_split_realms;
784         __le64 *split_inos = NULL, *split_realms = NULL;
785         int i;
786         int locked_rwsem = 0;
787 
788         /* decode */
789         if (msg->front.iov_len < sizeof(*h))
790                 goto bad;
791         h = p;
792         op = le32_to_cpu(h->op);
793         split = le64_to_cpu(h->split);   /* non-zero if we are splitting an
794                                           * existing realm */
795         num_split_inos = le32_to_cpu(h->num_split_inos);
796         num_split_realms = le32_to_cpu(h->num_split_realms);
797         trace_len = le32_to_cpu(h->trace_len);
798         p += sizeof(*h);
799 
800         dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds,
801              ceph_snap_op_name(op), split, trace_len);
802 
803         mutex_lock(&session->s_mutex);
804         session->s_seq++;
805         mutex_unlock(&session->s_mutex);
806 
807         down_write(&mdsc->snap_rwsem);
808         locked_rwsem = 1;
809 
810         if (op == CEPH_SNAP_OP_SPLIT) {
811                 struct ceph_mds_snap_realm *ri;
812 
813                 /*
814                  * A "split" breaks part of an existing realm off into
815                  * a new realm.  The MDS provides a list of inodes
816                  * (with caps) and child realms that belong to the new
817                  * child.
818                  */
819                 split_inos = p;
820                 p += sizeof(u64) * num_split_inos;
821                 split_realms = p;
822                 p += sizeof(u64) * num_split_realms;
823                 ceph_decode_need(&p, e, sizeof(*ri), bad);
824                 /* we will peek at realm info here, but will _not_
825                  * advance p, as the realm update will occur below in
826                  * ceph_update_snap_trace. */
827                 ri = p;
828 
829                 realm = ceph_lookup_snap_realm(mdsc, split);
830                 if (!realm) {
831                         realm = ceph_create_snap_realm(mdsc, split);
832                         if (IS_ERR(realm))
833                                 goto out;
834                 }
835                 ceph_get_snap_realm(mdsc, realm);
836 
837                 dout("splitting snap_realm %llx %p\n", realm->ino, realm);
838                 for (i = 0; i < num_split_inos; i++) {
839                         struct ceph_vino vino = {
840                                 .ino = le64_to_cpu(split_inos[i]),
841                                 .snap = CEPH_NOSNAP,
842                         };
843                         struct inode *inode = ceph_find_inode(sb, vino);
844                         struct ceph_inode_info *ci;
845                         struct ceph_snap_realm *oldrealm;
846 
847                         if (!inode)
848                                 continue;
849                         ci = ceph_inode(inode);
850 
851                         spin_lock(&ci->i_ceph_lock);
852                         if (!ci->i_snap_realm)
853                                 goto skip_inode;
854                         /*
855                          * If this inode belongs to a realm that was
856                          * created after our new realm, we experienced
857                          * a race (due to another split notifications
858                          * arriving from a different MDS).  So skip
859                          * this inode.
860                          */
861                         if (ci->i_snap_realm->created >
862                             le64_to_cpu(ri->created)) {
863                                 dout(" leaving %p in newer realm %llx %p\n",
864                                      inode, ci->i_snap_realm->ino,
865                                      ci->i_snap_realm);
866                                 goto skip_inode;
867                         }
868                         dout(" will move %p to split realm %llx %p\n",
869                              inode, realm->ino, realm);
870                         /*
871                          * Move the inode to the new realm
872                          */
873                         spin_lock(&realm->inodes_with_caps_lock);
874                         list_del_init(&ci->i_snap_realm_item);
875                         list_add(&ci->i_snap_realm_item,
876                                  &realm->inodes_with_caps);
877                         oldrealm = ci->i_snap_realm;
878                         ci->i_snap_realm = realm;
879                         spin_unlock(&realm->inodes_with_caps_lock);
880                         spin_unlock(&ci->i_ceph_lock);
881 
882                         ceph_get_snap_realm(mdsc, realm);
883                         ceph_put_snap_realm(mdsc, oldrealm);
884 
885                         iput(inode);
886                         continue;
887 
888 skip_inode:
889                         spin_unlock(&ci->i_ceph_lock);
890                         iput(inode);
891                 }
892 
893                 /* we may have taken some of the old realm's children. */
894                 for (i = 0; i < num_split_realms; i++) {
895                         struct ceph_snap_realm *child =
896                                 ceph_lookup_snap_realm(mdsc,
897                                            le64_to_cpu(split_realms[i]));
898                         if (!child)
899                                 continue;
900                         adjust_snap_realm_parent(mdsc, child, realm->ino);
901                 }
902         }
903 
904         /*
905          * update using the provided snap trace. if we are deleting a
906          * snap, we can avoid queueing cap_snaps.
907          */
908         ceph_update_snap_trace(mdsc, p, e,
909                                op == CEPH_SNAP_OP_DESTROY);
910 
911         if (op == CEPH_SNAP_OP_SPLIT)
912                 /* we took a reference when we created the realm, above */
913                 ceph_put_snap_realm(mdsc, realm);
914 
915         __cleanup_empty_realms(mdsc);
916 
917         up_write(&mdsc->snap_rwsem);
918 
919         flush_snaps(mdsc);
920         return;
921 
922 bad:
923         pr_err("corrupt snap message from mds%d\n", mds);
924         ceph_msg_dump(msg);
925 out:
926         if (locked_rwsem)
927                 up_write(&mdsc->snap_rwsem);
928         return;
929 }
930 
931 
932 
933 

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