ceph: queue cap snap writeback for realm children on snap update

When a realm is updated, we need to queue writeback on inodes in that
realm _and_ its children.  Otherwise, if the inode gets cowed on the
server, we can get a hang later due to out-of-sync cap/snap state.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index 2cb190c2bd99d38fcc29d5ffa46467259abcba87..6bdbf3ae7082663727cdafbfb495e9167b2df7b3 100644 (file)
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -548,6 +548,41 @@ int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
        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);
+               if (lastinode)
+                       iput(lastinode);
+               lastinode = inode;
+               ceph_queue_cap_snap(ci);
+               spin_lock(&realm->inodes_with_caps_lock);
+       }
+       spin_unlock(&realm->inodes_with_caps_lock);
+       if (lastinode)
+               iput(lastinode);
+
+       dout("queue_realm_cap_snaps %p %llx children\n", realm, realm->ino);
+       list_for_each_entry(child, &realm->children, child_item)
+               queue_realm_cap_snaps(child);
+
+       dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino);
+}
 
 /*
  * Parse and apply a snapblob "snap trace" from the MDS.  This specifies
@@ -598,29 +633,8 @@ more:
                 *
                 * ...unless it's a snap deletion!
                 */
-               if (!deletion) {
-                       struct ceph_inode_info *ci;
-                       struct inode *lastinode = NULL;
-
-                       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);
-                               if (lastinode)
-                                       iput(lastinode);
-                               lastinode = inode;
-                               ceph_queue_cap_snap(ci);
-                               spin_lock(&realm->inodes_with_caps_lock);
-                       }
-                       spin_unlock(&realm->inodes_with_caps_lock);
-                       if (lastinode)
-                               iput(lastinode);
-                       dout("update_snap_trace cap_snaps queued\n");
-               }
-
+               if (!deletion)
+                       queue_realm_cap_snaps(realm);
        } else {
                dout("update_snap_trace %llx %p seq %lld unchanged\n",
                     realm->ino, realm, realm->seq);