librbd: quickly check for duplicate snap name upon create

During journal replay, quickly check for a duplicate snap name
before allocating a snapshot sequence from the OSDs and
reverting due to the duplicate name.

Signed-off-by: Jason Dillaman <dillaman@redhat.com>
(cherry picked from commit 8374d45c7644666103f88c410a2b1b781f3a0cb8)

diff --git a/src/librbd/Operations.cc b/src/librbd/Operations.cc
index c523b912680d3d2a36a2139dbb57207edad72fdd..7766a1222f8652095c0f7e4a0eb9c50896dec33d 100644 (file)
--- a/src/librbd/Operations.cc
+++ b/src/librbd/Operations.cc
@@ -617,6 +617,14 @@ void Operations<I>::execute_snap_create(const char *snap_name,
   ldout(cct, 5) << this << " " << __func__ << ": snap_name=" << snap_name
                 << dendl;
 
+  m_image_ctx.snap_lock.get_read();
+  if (m_image_ctx.get_snap_id(snap_name) != CEPH_NOSNAP) {
+    m_image_ctx.snap_lock.put_read();
+    on_finish->complete(-EEXIST);
+    return;
+  }
+  m_image_ctx.snap_lock.put_read();
+
   operation::SnapshotCreateRequest<I> *req =
     new operation::SnapshotCreateRequest<I>(
       m_image_ctx, new C_NotifyUpdate<I>(m_image_ctx, on_finish), snap_name,