ceph: add missing locking to protect i_snap_realm_item during split

All ci->i_snap_realm_item/realm->inodes_with_caps manipulation should be
protected by realm->inodes_with_caps_lock.  This bug would have only bit
us in a rare race with a realm split (during some snap creations).

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

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index bf2a5f3846a4..8a43bc8675eb 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -818,7 +818,9 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc,
                          * queued (again) by ceph_update_snap_trace()
                          * below.  Queue it _now_, under the old context.
                          */
+                        spin_lock(&realm->inodes_with_caps_lock);
                         list_del_init(&ci->i_snap_realm_item);
+                        spin_unlock(&realm->inodes_with_caps_lock);
                         spin_unlock(&inode->i_lock);
 
                         ceph_queue_cap_snap(ci,