ceph: fix a buffer leak in __ceph_setxattr()

The old_blob in __ceph_setxattr() can store
ci->i_xattrs.prealloc_blob value during the retry.
However, it is never called the ceph_buffer_put()
for the old_blob object. This patch fixes the issue of
the buffer leak.

Cc: stable@vger.kernel.org
Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/xattr.c

@@ -1294,6 +1294,7 @@ retry:
 
 do_sync:
 	spin_unlock(&ci->i_ceph_lock);
+	ceph_buffer_put(old_blob);
 do_sync_unlocked:
 	if (lock_snap_rwsem)
 		up_read(&mdsc->snap_rwsem);