[Qemu-devel] [PATCH 1/8] block: fix aio_flush segfaults for read-only protocols (e.g. curl)

[Kevin Wolf <kwolf@redhat.com>]

From: Avi Kivity <avi@redhat.com>

Not all block format drivers expose an io_flush method (reasonable for
read-only protocols), so calling io_flush there will immediately segfault.

Fix by checking for the method's existence before calling it.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 aio.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/aio.c b/aio.c
index f164a47..2f08655 100644
--- a/aio.c
+++ b/aio.c
@@ -113,7 +113,9 @@ void qemu_aio_flush(void)
         qemu_aio_wait();
 
         QLIST_FOREACH(node, &aio_handlers, node) {
-            ret |= node->io_flush(node->opaque);
+            if (node->io_flush) {
+                ret |= node->io_flush(node->opaque);
+            }
         }
     } while (qemu_bh_poll() || ret > 0);
 }
-- 
1.6.6.1