[Qemu-devel] [PATCH V2 03/12] blockdev: allow BdrvActionOps->commit() to be NULL

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

From: Stefan Hajnoczi <stefanha@redhat.com>

Some QMP 'transaction' types don't need to do anything on .commit().
Make .commit() optional just like .abort().

The "drive-backup" action will take advantage of this, it only needs to
cancel the block job on .abort().  Other block job actions will probably
follow the same pattern, so allow .commit() to be NULL.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
---
 blockdev.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 46a43b0..4bd6cbc 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -789,7 +789,7 @@ typedef struct BdrvActionOps {
     size_t instance_size;
     /* Prepare the work, must NOT be NULL. */
     void (*prepare)(BlkTransactionState *common, Error **errp);
-    /* Commit the changes, must NOT be NULL. */
+    /* Commit the changes, can be NULL. */
     void (*commit)(BlkTransactionState *common);
     /* Abort the changes on fail, can be NULL. */
     void (*abort)(BlkTransactionState *common);
@@ -969,7 +969,9 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
     }
 
     QSIMPLEQ_FOREACH(state, &snap_bdrv_states, entry) {
-        state->ops->commit(state);
+        if (state->ops->commit) {
+            state->ops->commit(state);
+        }
     }
 
     /* success */
-- 
1.7.1