3 files changed, 35 insertions, 3 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);
+}
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index f6e12377335c..3b5c1e3335db 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -1028,15 +1028,20 @@ static int __init init_ceph(void)
 
         ceph_flock_init();
         ceph_xattr_init();
+        ret = ceph_snap_init();
+        if (ret)
+                goto out_xattr;
         ret = register_filesystem(&ceph_fs_type);
         if (ret)
-                goto out_icache;
+                goto out_snap;
 
         pr_info("loaded (mds proto %d)\n", CEPH_MDSC_PROTOCOL);
 
         return 0;
 
-out_icache:
+out_snap:
+        ceph_snap_exit();
+out_xattr:
         ceph_xattr_exit();
         destroy_caches();
 out:
@@ -1047,6 +1052,7 @@ static void __exit exit_ceph(void)
 {
         dout("exit_ceph\n");
         unregister_filesystem(&ceph_fs_type);
+        ceph_snap_exit();
         ceph_xattr_exit();
         destroy_caches();
 }
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index aca22879b41f..fc1c8255dead 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -699,6 +699,8 @@ extern void ceph_queue_cap_snap(struct ceph_inode_info *ci);
 extern int __ceph_finish_cap_snap(struct ceph_inode_info *ci,
                                   struct ceph_cap_snap *capsnap);
 extern void ceph_cleanup_empty_realms(struct ceph_mds_client *mdsc);
+extern int ceph_snap_init(void);
+extern void ceph_snap_exit(void);
 
 /*
  * a cap_snap is "pending" if it is still awaiting an in-progress