1 files changed, 25 insertions, 1 deletions

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index c1cc993225e3..f64576e72b79 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -288,6 +288,9 @@ static int cmpu64_rev(const void *a, const void *b)
         return 0;
 }
 
+
+static struct ceph_snap_context *empty_snapc;
+
 /*
  * build the snap context for a given realm.
  */
@@ -328,6 +331,12 @@ static int build_snap_context(struct ceph_snap_realm *realm)
                 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))
@@ -365,6 +374,7 @@ static int build_snap_context(struct ceph_snap_realm *realm)
              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;
@@ -465,6 +475,9 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci)
                    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;
@@ -925,5 +938,16 @@ out:
         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);
+}