qcow2: Declare BDRV_REQ_NO_FALLBACK supported

In the common case, qcow2_co_pwrite_zeroes() already only modifies
metadata case, so we're fine with or without BDRV_REQ_NO_FALLBACK set.

The only exception is when using an external data file, where the
request is passed down to the block driver of the external data file. We
are forwarding the BDRV_REQ_NO_FALLBACK flag there, though, so this is
fine, too.

Declare the flag supported therefore.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>

diff --git a/block/qcow2.c b/block/qcow2.c
index 7c18721741eacfb7f6c2c1f0efe63b048967d000..de0e89cf25003869530ae52b8703cdeded525d81 100644 (file)
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1722,7 +1722,8 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
         }
     }
 
-    bs->supported_zero_flags = header.version >= 3 ? BDRV_REQ_MAY_UNMAP : 0;
+    bs->supported_zero_flags = header.version >= 3 ?
+                               BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK : 0;
 
     /* Repair image if dirty */
     if (!(flags & (BDRV_O_CHECK | BDRV_O_INACTIVE)) && !bs->read_only &&