Re: [PATCH v4 5/9] raw-format: Support BDRV_REQ_ZERO_WRITE for truncate

[Eric Blake <eblake@redhat.com>]

On 4/20/20 8:32 AM, Kevin Wolf wrote:
> The raw format driver can simply forward the flag and let its bs->file
> child take care of actually providing the zeros.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block/raw-format.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/raw-format.c b/block/raw-format.c
> index 3465c9a865..ab69ac46d3 100644
> --- a/block/raw-format.c
> +++ b/block/raw-format.c
> @@ -387,7 +387,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>   
>       s->size = offset;
>       offset += s->offset;
> -    return bdrv_co_truncate(bs->file, offset, exact, prealloc, 0, errp);
> +    return bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
>   }
>   
>   static void raw_eject(BlockDriverState *bs, bool eject_flag)
> @@ -445,6 +445,7 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags,
>       bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
>           ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
>               bs->file->bs->supported_zero_flags);
> +    bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;

Shouldn't this be:

bs->supported_truncate_flags = (bs->file->bs->supported_truncate_flags &
                                 BDRV_REQ_ZERO_WRITE);

rather than unconditionally advertising something that the underlying 
layer may lack?

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