From 04d360a4c1e7b29bafe4aa4a9e91e98360932d31 Mon Sep 17 00:00:00 2001
From: Josh Durgin <jdurgin@redhat.com>
Date: Mon, 23 Feb 2015 19:50:55 -0800
Subject: [PATCH] librbd: take ImageCtx->snap_lock for write in add_snap()

add_snap() updates the ImageCtx snapshot metadata in memory, as well
as reading the flags as part of the object map snapshot. Both of these
require holding snap_lock.

Signed-off-by: Josh Durgin <jdurgin@redhat.com>
---
 src/librbd/internal.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/librbd/internal.cc b/src/librbd/internal.cc
index 6db4eba4985..d3ee11696a5 100644
--- a/src/librbd/internal.cc
+++ b/src/librbd/internal.cc
@@ -1783,6 +1783,7 @@ reprotect_and_return_err:
       return r;
     }
 
+    RWLock::WLocker l(ictx->snap_lock);
     if (!ictx->old_format) {
       if (ictx->object_map != NULL) {
 	ictx->object_map->snapshot(snap_id);