Re: [Qemu-devel] [PATCH v3 02/29] block: Inherit opt_transfer_length

["Benoît Canet" <benoit.canet@irqsave.net>]

Le Friday 17 Jan 2014 à 15:14:52 (+0100), Kevin Wolf a écrit :
> When there is a format driver between the backend, it's not guaranteed
> that exposing the opt_transfer_length for the format driver results in
> the optimal requests (because of fragmentation etc.), but it can't make
> things worse, so let's just do it.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
> Reviewed-by: Max Reitz <mreitz@redhat.com>
> ---
>  block.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/block.c b/block.c
> index 99e69da..20f85cb 100644
> --- a/block.c
> +++ b/block.c
> @@ -485,7 +485,25 @@ static int bdrv_refresh_limits(BlockDriverState *bs)
>  
>      memset(&bs->bl, 0, sizeof(bs->bl));
>  
> -    if (drv && drv->bdrv_refresh_limits) {
> +    if (!drv) {
> +        return 0;
> +    }
> +
> +    /* Take some limits from the children as a default */
> +    if (bs->file) {
> +        bdrv_refresh_limits(bs->file);
> +        bs->bl.opt_transfer_length = bs->file->bl.opt_transfer_length;
> +    }
> +
> +    if (bs->backing_hd) {
> +        bdrv_refresh_limits(bs->backing_hd);
> +        bs->bl.opt_transfer_length =
> +            MAX(bs->bl.opt_transfer_length,
> +                bs->backing_hd->bl.opt_transfer_length);
> +    }
> +
> +    /* Then let the driver override it */
> +    if (drv->bdrv_refresh_limits) {
>          return drv->bdrv_refresh_limits(bs);
>      }

Reviewed-by: Benoît Canet <benoit@irqsave.net>
>  
> -- 
> 1.8.1.4
> 
>