qcow2: Flush image after creation
Opening the qcow2 image with BDRV_O_NO_FLUSH prevents any flushes during
the image creation. This means that the image has not yet been flushed
to disk when qemu-img create exits. This flush is delayed until the next
operation on the image involving opening it without BDRV_O_NO_FLUSH and
closing (or directly flushing) it. For large images and/or images with a
small cluster size and preallocated metadata, this flush may take a
significant amount of time and may occur unexpectedly.
Reopening the image without BDRV_O_NO_FLUSH right before the end of
qcow2_create2() results in hoisting the potentially costly flush into
the image creation, which is expected to take some time (whereas
successive image operations may be not).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/qcow2.c b/block/qcow2.c
index 01269f9..6e5d98d 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1584,6 +1584,16 @@
}
}
+ bdrv_close(bs);
+
+ /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
+ ret = bdrv_open(bs, filename, NULL,
+ BDRV_O_RDWR | BDRV_O_CACHE_WB, drv, &local_err);
+ if (error_is_set(&local_err)) {
+ error_propagate(errp, local_err);
+ goto out;
+ }
+
ret = 0;
out:
bdrv_unref(bs);
