diff options
Diffstat (limited to 'kernel/fs/ceph/snap.c')
| -rw-r--r-- | kernel/fs/ceph/snap.c | 977 |
1 files changed, 977 insertions, 0 deletions
diff --git a/kernel/fs/ceph/snap.c b/kernel/fs/ceph/snap.c new file mode 100644 index 000000000..a97e39f09 --- /dev/null +++ b/kernel/fs/ceph/snap.c @@ -0,0 +1,977 @@ +#include <linux/ceph/ceph_debug.h> + +#include <linux/sort.h> +#include <linux/slab.h> + +#include "super.h" +#include "mds_client.h" + +#include <linux/ceph/decode.h> + +/* + * Snapshots in ceph are driven in large part by cooperation from the + * client. In contrast to local file systems or file servers that + * implement snapshots at a single point in the system, ceph's + * distributed access to storage requires clients to help decide + * whether a write logically occurs before or after a recently created + * snapshot. + * + * This provides a perfect instantanous client-wide snapshot. Between + * clients, however, snapshots may appear to be applied at slightly + * different points in time, depending on delays in delivering the + * snapshot notification. + * + * Snapshots are _not_ file system-wide. Instead, each snapshot + * applies to the subdirectory nested beneath some directory. This + * effectively divides the hierarchy into multiple "realms," where all + * of the files contained by each realm share the same set of + * snapshots. An individual realm's snap set contains snapshots + * explicitly created on that realm, as well as any snaps in its + * parent's snap set _after_ the point at which the parent became it's + * parent (due to, say, a rename). Similarly, snaps from prior parents + * during the time intervals during which they were the parent are included. + * + * The client is spared most of this detail, fortunately... it must only + * maintains a hierarchy of realms reflecting the current parent/child + * realm relationship, and for each realm has an explicit list of snaps + * inherited from prior parents. + * + * A snap_realm struct is maintained for realms containing every inode + * with an open cap in the system. (The needed snap realm information is + * provided by the MDS whenever a cap is issued, i.e., on open.) A 'seq' + * version number is used to ensure that as realm parameters change (new + * snapshot, new parent, etc.) the client's realm hierarchy is updated. + * + * The realm hierarchy drives the generation of a 'snap context' for each + * realm, which simply lists the resulting set of snaps for the realm. This + * is attached to any writes sent to OSDs. + */ +/* + * Unfortunately error handling is a bit mixed here. If we get a snap + * update, but don't have enough memory to update our realm hierarchy, + * it's not clear what we can do about it (besides complaining to the + * console). + */ + + +/* + * increase ref count for the realm + * + * caller must hold snap_rwsem for write. + */ +void ceph_get_snap_realm(struct ceph_mds_client *mdsc, + struct ceph_snap_realm *realm) +{ + dout("get_realm %p %d -> %d\n", realm, + atomic_read(&realm->nref), atomic_read(&realm->nref)+1); + /* + * since we _only_ increment realm refs or empty the empty + * list with snap_rwsem held, adjusting the empty list here is + * safe. we do need to protect against concurrent empty list + * additions, however. + */ + if (atomic_inc_return(&realm->nref) == 1) { + spin_lock(&mdsc->snap_empty_lock); + list_del_init(&realm->empty_item); + spin_unlock(&mdsc->snap_empty_lock); + } +} + +static void __insert_snap_realm(struct rb_root *root, + struct ceph_snap_realm *new) +{ + struct rb_node **p = &root->rb_node; + struct rb_node *parent = NULL; + struct ceph_snap_realm *r = NULL; + + while (*p) { + parent = *p; + r = rb_entry(parent, struct ceph_snap_realm, node); + if (new->ino < r->ino) + p = &(*p)->rb_left; + else if (new->ino > r->ino) + p = &(*p)->rb_right; + else + BUG(); + } + + rb_link_node(&new->node, parent, p); + rb_insert_color(&new->node, root); +} + +/* + * create and get the realm rooted at @ino and bump its ref count. + * + * caller must hold snap_rwsem for write. + */ +static struct ceph_snap_realm *ceph_create_snap_realm( + struct ceph_mds_client *mdsc, + u64 ino) +{ + struct ceph_snap_realm *realm; + + realm = kzalloc(sizeof(*realm), GFP_NOFS); + if (!realm) + return ERR_PTR(-ENOMEM); + + atomic_set(&realm->nref, 1); /* for caller */ + realm->ino = ino; + INIT_LIST_HEAD(&realm->children); + INIT_LIST_HEAD(&realm->child_item); + INIT_LIST_HEAD(&realm->empty_item); + INIT_LIST_HEAD(&realm->dirty_item); + INIT_LIST_HEAD(&realm->inodes_with_caps); + spin_lock_init(&realm->inodes_with_caps_lock); + __insert_snap_realm(&mdsc->snap_realms, realm); + dout("create_snap_realm %llx %p\n", realm->ino, realm); + return realm; +} + +/* + * lookup the realm rooted at @ino. + * + * caller must hold snap_rwsem for write. + */ +static struct ceph_snap_realm *__lookup_snap_realm(struct ceph_mds_client *mdsc, + u64 ino) +{ + struct rb_node *n = mdsc->snap_realms.rb_node; + struct ceph_snap_realm *r; + + while (n) { + r = rb_entry(n, struct ceph_snap_realm, node); + if (ino < r->ino) + n = n->rb_left; + else if (ino > r->ino) + n = n->rb_right; + else { + dout("lookup_snap_realm %llx %p\n", r->ino, r); + return r; + } + } + return NULL; +} + +struct ceph_snap_realm *ceph_lookup_snap_realm(struct ceph_mds_client *mdsc, + u64 ino) +{ + struct ceph_snap_realm *r; + r = __lookup_snap_realm(mdsc, ino); + if (r) + ceph_get_snap_realm(mdsc, r); + return r; +} + +static void __put_snap_realm(struct ceph_mds_client *mdsc, + struct ceph_snap_realm *realm); + +/* + * called with snap_rwsem (write) + */ +static void __destroy_snap_realm(struct ceph_mds_client *mdsc, + struct ceph_snap_realm *realm) +{ + dout("__destroy_snap_realm %p %llx\n", realm, realm->ino); + + rb_erase(&realm->node, &mdsc->snap_realms); + + if (realm->parent) { + list_del_init(&realm->child_item); + __put_snap_realm(mdsc, realm->parent); + } + + kfree(realm->prior_parent_snaps); + kfree(realm->snaps); + ceph_put_snap_context(realm->cached_context); + kfree(realm); +} + +/* + * caller holds snap_rwsem (write) + */ +static void __put_snap_realm(struct ceph_mds_client *mdsc, + struct ceph_snap_realm *realm) +{ + dout("__put_snap_realm %llx %p %d -> %d\n", realm->ino, realm, + atomic_read(&realm->nref), atomic_read(&realm->nref)-1); + if (atomic_dec_and_test(&realm->nref)) + __destroy_snap_realm(mdsc, realm); +} + +/* + * caller needn't hold any locks + */ +void ceph_put_snap_realm(struct ceph_mds_client *mdsc, + struct ceph_snap_realm *realm) +{ + dout("put_snap_realm %llx %p %d -> %d\n", realm->ino, realm, + atomic_read(&realm->nref), atomic_read(&realm->nref)-1); + if (!atomic_dec_and_test(&realm->nref)) + return; + + if (down_write_trylock(&mdsc->snap_rwsem)) { + __destroy_snap_realm(mdsc, realm); + up_write(&mdsc->snap_rwsem); + } else { + spin_lock(&mdsc->snap_empty_lock); + list_add(&realm->empty_item, &mdsc->snap_empty); + spin_unlock(&mdsc->snap_empty_lock); + } +} + +/* + * Clean up any realms whose ref counts have dropped to zero. Note + * that this does not include realms who were created but not yet + * used. + * + * Called under snap_rwsem (write) + */ +static void __cleanup_empty_realms(struct ceph_mds_client *mdsc) +{ + struct ceph_snap_realm *realm; + + spin_lock(&mdsc->snap_empty_lock); + while (!list_empty(&mdsc->snap_empty)) { + realm = list_first_entry(&mdsc->snap_empty, + struct ceph_snap_realm, empty_item); + list_del(&realm->empty_item); + spin_unlock(&mdsc->snap_empty_lock); + __destroy_snap_realm(mdsc, realm); + spin_lock(&mdsc->snap_empty_lock); + } + spin_unlock(&mdsc->snap_empty_lock); +} + +void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc) +{ + down_write(&mdsc->snap_rwsem); + __cleanup_empty_realms(mdsc); + up_write(&mdsc->snap_rwsem); +} + +/* + * adjust the parent realm of a given @realm. adjust child list, and parent + * pointers, and ref counts appropriately. + * + * return true if parent was changed, 0 if unchanged, <0 on error. + * + * caller must hold snap_rwsem for write. + */ +static int adjust_snap_realm_parent(struct ceph_mds_client *mdsc, + struct ceph_snap_realm *realm, + u64 parentino) +{ + struct ceph_snap_realm *parent; + + if (realm->parent_ino == parentino) + return 0; + + parent = ceph_lookup_snap_realm(mdsc, parentino); + if (!parent) { + parent = ceph_create_snap_realm(mdsc, parentino); + if (IS_ERR(parent)) + return PTR_ERR(parent); + } + dout("adjust_snap_realm_parent %llx %p: %llx %p -> %llx %p\n", + realm->ino, realm, realm->parent_ino, realm->parent, + parentino, parent); + if (realm->parent) { + list_del_init(&realm->child_item); + ceph_put_snap_realm(mdsc, realm->parent); + } + realm->parent_ino = parentino; + realm->parent = parent; + list_add(&realm->child_item, &parent->children); + return 1; +} + + +static int cmpu64_rev(const void *a, const void *b) +{ + if (*(u64 *)a < *(u64 *)b) + return 1; + if (*(u64 *)a > *(u64 *)b) + return -1; + return 0; +} + + +static struct ceph_snap_context *empty_snapc; + +/* + * build the snap context for a given realm. + */ +static int build_snap_context(struct ceph_snap_realm *realm) +{ + struct ceph_snap_realm *parent = realm->parent; + struct ceph_snap_context *snapc; + int err = 0; + u32 num = realm->num_prior_parent_snaps + realm->num_snaps; + + /* + * build parent context, if it hasn't been built. + * conservatively estimate that all parent snaps might be + * included by us. + */ + if (parent) { + if (!parent->cached_context) { + err = build_snap_context(parent); + if (err) + goto fail; + } + num += parent->cached_context->num_snaps; + } + + /* do i actually need to update? not if my context seq + matches realm seq, and my parents' does to. (this works + because we rebuild_snap_realms() works _downward_ in + hierarchy after each update.) */ + if (realm->cached_context && + realm->cached_context->seq == realm->seq && + (!parent || + realm->cached_context->seq >= parent->cached_context->seq)) { + dout("build_snap_context %llx %p: %p seq %lld (%u snaps)" + " (unchanged)\n", + realm->ino, realm, realm->cached_context, + realm->cached_context->seq, + (unsigned int) realm->cached_context->num_snaps); + return 0; + } + + if (num == 0 && realm->seq == empty_snapc->seq) { + ceph_get_snap_context(empty_snapc); + snapc = empty_snapc; + goto done; + } + + /* alloc new snap context */ + err = -ENOMEM; + if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64)) + goto fail; + snapc = ceph_create_snap_context(num, GFP_NOFS); + if (!snapc) + goto fail; + + /* build (reverse sorted) snap vector */ + num = 0; + snapc->seq = realm->seq; + if (parent) { + u32 i; + + /* include any of parent's snaps occurring _after_ my + parent became my parent */ + for (i = 0; i < parent->cached_context->num_snaps; i++) + if (parent->cached_context->snaps[i] >= + realm->parent_since) + snapc->snaps[num++] = + parent->cached_context->snaps[i]; + if (parent->cached_context->seq > snapc->seq) + snapc->seq = parent->cached_context->seq; + } + memcpy(snapc->snaps + num, realm->snaps, + sizeof(u64)*realm->num_snaps); + num += realm->num_snaps; + memcpy(snapc->snaps + num, realm->prior_parent_snaps, + sizeof(u64)*realm->num_prior_parent_snaps); + num += realm->num_prior_parent_snaps; + + sort(snapc->snaps, num, sizeof(u64), cmpu64_rev, NULL); + snapc->num_snaps = num; + dout("build_snap_context %llx %p: %p seq %lld (%u snaps)\n", + realm->ino, realm, snapc, snapc->seq, + (unsigned int) snapc->num_snaps); + +done: + ceph_put_snap_context(realm->cached_context); + realm->cached_context = snapc; + return 0; + +fail: + /* + * if we fail, clear old (incorrect) cached_context... hopefully + * we'll have better luck building it later + */ + if (realm->cached_context) { + ceph_put_snap_context(realm->cached_context); + realm->cached_context = NULL; + } + pr_err("build_snap_context %llx %p fail %d\n", realm->ino, + realm, err); + return err; +} + +/* + * rebuild snap context for the given realm and all of its children. + */ +static void rebuild_snap_realms(struct ceph_snap_realm *realm) +{ + struct ceph_snap_realm *child; + + dout("rebuild_snap_realms %llx %p\n", realm->ino, realm); + build_snap_context(realm); + + list_for_each_entry(child, &realm->children, child_item) + rebuild_snap_realms(child); +} + + +/* + * helper to allocate and decode an array of snapids. free prior + * instance, if any. + */ +static int dup_array(u64 **dst, __le64 *src, u32 num) +{ + u32 i; + + kfree(*dst); + if (num) { + *dst = kcalloc(num, sizeof(u64), GFP_NOFS); + if (!*dst) + return -ENOMEM; + for (i = 0; i < num; i++) + (*dst)[i] = get_unaligned_le64(src + i); + } else { + *dst = NULL; + } + return 0; +} + + +/* + * When a snapshot is applied, the size/mtime inode metadata is queued + * in a ceph_cap_snap (one for each snapshot) until writeback + * completes and the metadata can be flushed back to the MDS. + * + * However, if a (sync) write is currently in-progress when we apply + * the snapshot, we have to wait until the write succeeds or fails + * (and a final size/mtime is known). In this case the + * cap_snap->writing = 1, and is said to be "pending." When the write + * finishes, we __ceph_finish_cap_snap(). + * + * Caller must hold snap_rwsem for read (i.e., the realm topology won't + * change). + */ +void ceph_queue_cap_snap(struct ceph_inode_info *ci) +{ + struct inode *inode = &ci->vfs_inode; + struct ceph_cap_snap *capsnap; + int used, dirty; + + capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS); + if (!capsnap) { + pr_err("ENOMEM allocating ceph_cap_snap on %p\n", inode); + return; + } + + spin_lock(&ci->i_ceph_lock); + used = __ceph_caps_used(ci); + dirty = __ceph_caps_dirty(ci); + + /* + * If there is a write in progress, treat that as a dirty Fw, + * even though it hasn't completed yet; by the time we finish + * up this capsnap it will be. + */ + if (used & CEPH_CAP_FILE_WR) + dirty |= CEPH_CAP_FILE_WR; + + if (__ceph_have_pending_cap_snap(ci)) { + /* there is no point in queuing multiple "pending" cap_snaps, + as no new writes are allowed to start when pending, so any + writes in progress now were started before the previous + cap_snap. lucky us. */ + dout("queue_cap_snap %p already pending\n", inode); + kfree(capsnap); + } else if (ci->i_snap_realm->cached_context == empty_snapc) { + dout("queue_cap_snap %p empty snapc\n", inode); + kfree(capsnap); + } else if (dirty & (CEPH_CAP_AUTH_EXCL|CEPH_CAP_XATTR_EXCL| + CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR)) { + struct ceph_snap_context *snapc = ci->i_head_snapc; + + /* + * if we are a sync write, we may need to go to the snaprealm + * to get the current snapc. + */ + if (!snapc) + snapc = ci->i_snap_realm->cached_context; + + dout("queue_cap_snap %p cap_snap %p queuing under %p %s\n", + inode, capsnap, snapc, ceph_cap_string(dirty)); + ihold(inode); + + atomic_set(&capsnap->nref, 1); + capsnap->ci = ci; + INIT_LIST_HEAD(&capsnap->ci_item); + INIT_LIST_HEAD(&capsnap->flushing_item); + + capsnap->follows = snapc->seq; + capsnap->issued = __ceph_caps_issued(ci, NULL); + capsnap->dirty = dirty; + + capsnap->mode = inode->i_mode; + capsnap->uid = inode->i_uid; + capsnap->gid = inode->i_gid; + + if (dirty & CEPH_CAP_XATTR_EXCL) { + __ceph_build_xattrs_blob(ci); + capsnap->xattr_blob = + ceph_buffer_get(ci->i_xattrs.blob); + capsnap->xattr_version = ci->i_xattrs.version; + } else { + capsnap->xattr_blob = NULL; + capsnap->xattr_version = 0; + } + + capsnap->inline_data = ci->i_inline_version != CEPH_INLINE_NONE; + + /* dirty page count moved from _head to this cap_snap; + all subsequent writes page dirties occur _after_ this + snapshot. */ + capsnap->dirty_pages = ci->i_wrbuffer_ref_head; + ci->i_wrbuffer_ref_head = 0; + capsnap->context = snapc; + ci->i_head_snapc = + ceph_get_snap_context(ci->i_snap_realm->cached_context); + dout(" new snapc is %p\n", ci->i_head_snapc); + list_add_tail(&capsnap->ci_item, &ci->i_cap_snaps); + + if (used & CEPH_CAP_FILE_WR) { + dout("queue_cap_snap %p cap_snap %p snapc %p" + " seq %llu used WR, now pending\n", inode, + capsnap, snapc, snapc->seq); + capsnap->writing = 1; + } else { + /* note mtime, size NOW. */ + __ceph_finish_cap_snap(ci, capsnap); + } + } else { + dout("queue_cap_snap %p nothing dirty|writing\n", inode); + kfree(capsnap); + } + + spin_unlock(&ci->i_ceph_lock); +} + +/* + * Finalize the size, mtime for a cap_snap.. that is, settle on final values + * to be used for the snapshot, to be flushed back to the mds. + * + * If capsnap can now be flushed, add to snap_flush list, and return 1. + * + * Caller must hold i_ceph_lock. + */ +int __ceph_finish_cap_snap(struct ceph_inode_info *ci, + struct ceph_cap_snap *capsnap) +{ + struct inode *inode = &ci->vfs_inode; + struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc; + + BUG_ON(capsnap->writing); + capsnap->size = inode->i_size; + capsnap->mtime = inode->i_mtime; + capsnap->atime = inode->i_atime; + capsnap->ctime = inode->i_ctime; + capsnap->time_warp_seq = ci->i_time_warp_seq; + if (capsnap->dirty_pages) { + dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu " + "still has %d dirty pages\n", inode, capsnap, + capsnap->context, capsnap->context->seq, + ceph_cap_string(capsnap->dirty), capsnap->size, + capsnap->dirty_pages); + return 0; + } + dout("finish_cap_snap %p cap_snap %p snapc %p %llu %s s=%llu\n", + inode, capsnap, capsnap->context, + capsnap->context->seq, ceph_cap_string(capsnap->dirty), + capsnap->size); + + spin_lock(&mdsc->snap_flush_lock); + list_add_tail(&ci->i_snap_flush_item, &mdsc->snap_flush_list); + spin_unlock(&mdsc->snap_flush_lock); + return 1; /* caller may want to ceph_flush_snaps */ +} + +/* + * Queue cap_snaps for snap writeback for this realm and its children. + * Called under snap_rwsem, so realm topology won't change. + */ +static void queue_realm_cap_snaps(struct ceph_snap_realm *realm) +{ + struct ceph_inode_info *ci; + struct inode *lastinode = NULL; + struct ceph_snap_realm *child; + + dout("queue_realm_cap_snaps %p %llx inodes\n", realm, realm->ino); + + spin_lock(&realm->inodes_with_caps_lock); + list_for_each_entry(ci, &realm->inodes_with_caps, + i_snap_realm_item) { + struct inode *inode = igrab(&ci->vfs_inode); + if (!inode) + continue; + spin_unlock(&realm->inodes_with_caps_lock); + iput(lastinode); + lastinode = inode; + ceph_queue_cap_snap(ci); + spin_lock(&realm->inodes_with_caps_lock); + } + spin_unlock(&realm->inodes_with_caps_lock); + iput(lastinode); + + list_for_each_entry(child, &realm->children, child_item) { + dout("queue_realm_cap_snaps %p %llx queue child %p %llx\n", + realm, realm->ino, child, child->ino); + list_del_init(&child->dirty_item); + list_add(&child->dirty_item, &realm->dirty_item); + } + + list_del_init(&realm->dirty_item); + dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino); +} + +/* + * Parse and apply a snapblob "snap trace" from the MDS. This specifies + * the snap realm parameters from a given realm and all of its ancestors, + * up to the root. + * + * Caller must hold snap_rwsem for write. + */ +int ceph_update_snap_trace(struct ceph_mds_client *mdsc, + void *p, void *e, bool deletion, + struct ceph_snap_realm **realm_ret) +{ + struct ceph_mds_snap_realm *ri; /* encoded */ + __le64 *snaps; /* encoded */ + __le64 *prior_parent_snaps; /* encoded */ + struct ceph_snap_realm *realm = NULL; + struct ceph_snap_realm *first_realm = NULL; + int invalidate = 0; + int err = -ENOMEM; + LIST_HEAD(dirty_realms); + + dout("update_snap_trace deletion=%d\n", deletion); +more: + ceph_decode_need(&p, e, sizeof(*ri), bad); + ri = p; + p += sizeof(*ri); + ceph_decode_need(&p, e, sizeof(u64)*(le32_to_cpu(ri->num_snaps) + + le32_to_cpu(ri->num_prior_parent_snaps)), bad); + snaps = p; + p += sizeof(u64) * le32_to_cpu(ri->num_snaps); + prior_parent_snaps = p; + p += sizeof(u64) * le32_to_cpu(ri->num_prior_parent_snaps); + + realm = ceph_lookup_snap_realm(mdsc, le64_to_cpu(ri->ino)); + if (!realm) { + realm = ceph_create_snap_realm(mdsc, le64_to_cpu(ri->ino)); + if (IS_ERR(realm)) { + err = PTR_ERR(realm); + goto fail; + } + } + + /* ensure the parent is correct */ + err = adjust_snap_realm_parent(mdsc, realm, le64_to_cpu(ri->parent)); + if (err < 0) + goto fail; + invalidate += err; + + if (le64_to_cpu(ri->seq) > realm->seq) { + dout("update_snap_trace updating %llx %p %lld -> %lld\n", + realm->ino, realm, realm->seq, le64_to_cpu(ri->seq)); + /* update realm parameters, snap lists */ + realm->seq = le64_to_cpu(ri->seq); + realm->created = le64_to_cpu(ri->created); + realm->parent_since = le64_to_cpu(ri->parent_since); + + realm->num_snaps = le32_to_cpu(ri->num_snaps); + err = dup_array(&realm->snaps, snaps, realm->num_snaps); + if (err < 0) + goto fail; + + realm->num_prior_parent_snaps = + le32_to_cpu(ri->num_prior_parent_snaps); + err = dup_array(&realm->prior_parent_snaps, prior_parent_snaps, + realm->num_prior_parent_snaps); + if (err < 0) + goto fail; + + /* queue realm for cap_snap creation */ + list_add(&realm->dirty_item, &dirty_realms); + + invalidate = 1; + } else if (!realm->cached_context) { + dout("update_snap_trace %llx %p seq %lld new\n", + realm->ino, realm, realm->seq); + invalidate = 1; + } else { + dout("update_snap_trace %llx %p seq %lld unchanged\n", + realm->ino, realm, realm->seq); + } + + dout("done with %llx %p, invalidated=%d, %p %p\n", realm->ino, + realm, invalidate, p, e); + + /* invalidate when we reach the _end_ (root) of the trace */ + if (invalidate && p >= e) + rebuild_snap_realms(realm); + + if (!first_realm) + first_realm = realm; + else + ceph_put_snap_realm(mdsc, realm); + + if (p < e) + goto more; + + /* + * queue cap snaps _after_ we've built the new snap contexts, + * so that i_head_snapc can be set appropriately. + */ + while (!list_empty(&dirty_realms)) { + realm = list_first_entry(&dirty_realms, struct ceph_snap_realm, + dirty_item); + queue_realm_cap_snaps(realm); + } + + if (realm_ret) + *realm_ret = first_realm; + else + ceph_put_snap_realm(mdsc, first_realm); + + __cleanup_empty_realms(mdsc); + return 0; + +bad: + err = -EINVAL; +fail: + if (realm && !IS_ERR(realm)) + ceph_put_snap_realm(mdsc, realm); + if (first_realm) + ceph_put_snap_realm(mdsc, first_realm); + pr_err("update_snap_trace error %d\n", err); + return err; +} + + +/* + * Send any cap_snaps that are queued for flush. Try to carry + * s_mutex across multiple snap flushes to avoid locking overhead. + * + * Caller holds no locks. + */ +static void flush_snaps(struct ceph_mds_client *mdsc) +{ + struct ceph_inode_info *ci; + struct inode *inode; + struct ceph_mds_session *session = NULL; + + dout("flush_snaps\n"); + spin_lock(&mdsc->snap_flush_lock); + while (!list_empty(&mdsc->snap_flush_list)) { + ci = list_first_entry(&mdsc->snap_flush_list, + struct ceph_inode_info, i_snap_flush_item); + inode = &ci->vfs_inode; + ihold(inode); + spin_unlock(&mdsc->snap_flush_lock); + spin_lock(&ci->i_ceph_lock); + __ceph_flush_snaps(ci, &session, 0); + spin_unlock(&ci->i_ceph_lock); + iput(inode); + spin_lock(&mdsc->snap_flush_lock); + } + spin_unlock(&mdsc->snap_flush_lock); + + if (session) { + mutex_unlock(&session->s_mutex); + ceph_put_mds_session(session); + } + dout("flush_snaps done\n"); +} + + +/* + * Handle a snap notification from the MDS. + * + * This can take two basic forms: the simplest is just a snap creation + * or deletion notification on an existing realm. This should update the + * realm and its children. + * + * The more difficult case is realm creation, due to snap creation at a + * new point in the file hierarchy, or due to a rename that moves a file or + * directory into another realm. + */ +void ceph_handle_snap(struct ceph_mds_client *mdsc, + struct ceph_mds_session *session, + struct ceph_msg *msg) +{ + struct super_block *sb = mdsc->fsc->sb; + int mds = session->s_mds; + u64 split; + int op; + int trace_len; + struct ceph_snap_realm *realm = NULL; + void *p = msg->front.iov_base; + void *e = p + msg->front.iov_len; + struct ceph_mds_snap_head *h; + int num_split_inos, num_split_realms; + __le64 *split_inos = NULL, *split_realms = NULL; + int i; + int locked_rwsem = 0; + + /* decode */ + if (msg->front.iov_len < sizeof(*h)) + goto bad; + h = p; + op = le32_to_cpu(h->op); + split = le64_to_cpu(h->split); /* non-zero if we are splitting an + * existing realm */ + num_split_inos = le32_to_cpu(h->num_split_inos); + num_split_realms = le32_to_cpu(h->num_split_realms); + trace_len = le32_to_cpu(h->trace_len); + p += sizeof(*h); + + dout("handle_snap from mds%d op %s split %llx tracelen %d\n", mds, + ceph_snap_op_name(op), split, trace_len); + + mutex_lock(&session->s_mutex); + session->s_seq++; + mutex_unlock(&session->s_mutex); + + down_write(&mdsc->snap_rwsem); + locked_rwsem = 1; + + if (op == CEPH_SNAP_OP_SPLIT) { + struct ceph_mds_snap_realm *ri; + + /* + * A "split" breaks part of an existing realm off into + * a new realm. The MDS provides a list of inodes + * (with caps) and child realms that belong to the new + * child. + */ + split_inos = p; + p += sizeof(u64) * num_split_inos; + split_realms = p; + p += sizeof(u64) * num_split_realms; + ceph_decode_need(&p, e, sizeof(*ri), bad); + /* we will peek at realm info here, but will _not_ + * advance p, as the realm update will occur below in + * ceph_update_snap_trace. */ + ri = p; + + realm = ceph_lookup_snap_realm(mdsc, split); + if (!realm) { + realm = ceph_create_snap_realm(mdsc, split); + if (IS_ERR(realm)) + goto out; + } + + dout("splitting snap_realm %llx %p\n", realm->ino, realm); + for (i = 0; i < num_split_inos; i++) { + struct ceph_vino vino = { + .ino = le64_to_cpu(split_inos[i]), + .snap = CEPH_NOSNAP, + }; + struct inode *inode = ceph_find_inode(sb, vino); + struct ceph_inode_info *ci; + struct ceph_snap_realm *oldrealm; + + if (!inode) + continue; + ci = ceph_inode(inode); + + spin_lock(&ci->i_ceph_lock); + if (!ci->i_snap_realm) + goto skip_inode; + /* + * If this inode belongs to a realm that was + * created after our new realm, we experienced + * a race (due to another split notifications + * arriving from a different MDS). So skip + * this inode. + */ + if (ci->i_snap_realm->created > + le64_to_cpu(ri->created)) { + dout(" leaving %p in newer realm %llx %p\n", + inode, ci->i_snap_realm->ino, + ci->i_snap_realm); + goto skip_inode; + } + dout(" will move %p to split realm %llx %p\n", + inode, realm->ino, realm); + /* + * Move the inode to the new realm + */ + spin_lock(&realm->inodes_with_caps_lock); + list_del_init(&ci->i_snap_realm_item); + list_add(&ci->i_snap_realm_item, + &realm->inodes_with_caps); + oldrealm = ci->i_snap_realm; + ci->i_snap_realm = realm; + spin_unlock(&realm->inodes_with_caps_lock); + spin_unlock(&ci->i_ceph_lock); + + ceph_get_snap_realm(mdsc, realm); + ceph_put_snap_realm(mdsc, oldrealm); + + iput(inode); + continue; + +skip_inode: + spin_unlock(&ci->i_ceph_lock); + iput(inode); + } + + /* we may have taken some of the old realm's children. */ + for (i = 0; i < num_split_realms; i++) { + struct ceph_snap_realm *child = + __lookup_snap_realm(mdsc, + le64_to_cpu(split_realms[i])); + if (!child) + continue; + adjust_snap_realm_parent(mdsc, child, realm->ino); + } + } + + /* + * update using the provided snap trace. if we are deleting a + * snap, we can avoid queueing cap_snaps. + */ + ceph_update_snap_trace(mdsc, p, e, + op == CEPH_SNAP_OP_DESTROY, NULL); + + if (op == CEPH_SNAP_OP_SPLIT) + /* we took a reference when we created the realm, above */ + ceph_put_snap_realm(mdsc, realm); + + __cleanup_empty_realms(mdsc); + + up_write(&mdsc->snap_rwsem); + + flush_snaps(mdsc); + return; + +bad: + pr_err("corrupt snap message from mds%d\n", mds); + ceph_msg_dump(msg); +out: + if (locked_rwsem) + up_write(&mdsc->snap_rwsem); + return; +} + +int __init ceph_snap_init(void) +{ + empty_snapc = ceph_create_snap_context(0, GFP_NOFS); + if (!empty_snapc) + return -ENOMEM; + empty_snapc->seq = 1; + return 0; +} + +void ceph_snap_exit(void) +{ + ceph_put_snap_context(empty_snapc); +} |