[Qemu-devel] [PATCH 2/2] block: Handle multiwrite errors only when all requests have completed

[Kevin Wolf <kwolf@redhat.com>]

Don't try to be clever by freeing all temporary data and calling all callbacks
when the return value (an error) is certain. Doing so has at least two
important problems:

* The temporary data that is freed (qiov, possibly zero buffer) is still used
  by the requests that have not yet completed.
* Calling the callbacks for all requests in the multiwrite means for the caller
  that it may free buffers etc. which are still in use.

Just remember the error value and do the cleanup when all requests have
completed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/block.c b/block.c
index 9719649..bff7d5a 100644
--- a/block.c
+++ b/block.c
@@ -2056,14 +2056,11 @@ static void multiwrite_cb(void *opaque, int ret)
 
     if (ret < 0 && !mcb->error) {
         mcb->error = ret;
-        multiwrite_user_cb(mcb);
     }
 
     mcb->num_requests--;
     if (mcb->num_requests == 0) {
-        if (mcb->error == 0) {
-            multiwrite_user_cb(mcb);
-        }
+        multiwrite_user_cb(mcb);
         qemu_free(mcb);
     }
 }
-- 
1.6.6.1