stubdom: fix read-only disks access

There is no need for a flush on read-only disks.  It would actually even
error out and disturb the guest.

Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>

diff --git a/block-vbd.c b/block-vbd.c
index a3465b748adbc22b2143667b2feec16feda37758..58015bdf007e70e7c8e0455ed78c92388a46708e 100644 (file)
--- a/block-vbd.c
+++ b/block-vbd.c
@@ -273,6 +273,10 @@ static BlockDriverAIOCB *vbd_aio_flush(BlockDriverState *bs,
     BDRVVbdState *s = bs->opaque;
     VbdAIOCB *acb = NULL;
 
+    if (s->info.mode == O_RDONLY) {
+        cb(opaque, 0);
+        return NULL;
+    }
     if (s->info.barrier == 1) {
         acb = vbd_aio_setup(bs, 0, NULL, 0,
                 s->info.flush == 1 ? vbd_nop_cb : cb, opaque);