ceph: buffer decoding helpers

Helper for decoding into a ceph_buffer, and other misc decoding helpers
we will need.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/buffer.h b/fs/ceph/buffer.h
index 47b9514..58d1901 100644
--- a/fs/ceph/buffer.h
+++ b/fs/ceph/buffer.h
@@ -34,4 +34,6 @@
 	kref_put(&b->kref, ceph_buffer_release);
 }
 
+extern int ceph_decode_buffer(struct ceph_buffer **b, void **p, void *end);
+
 #endif