Re: [PATCH v3 3/8] qcow2: Declare BDRV_REQ_NO_FALLBACK supported

[Eric Blake <eblake@redhat.com>]

On 11/22/19 10:05 AM, Kevin Wolf wrote:
> 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>
> ---
>   block/qcow2.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index b201383c3d..3fa10bf807 100644
> --- 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 &&
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org