Re: [PATCH 4/6] block/gluster: Do not force-cap *pnum

[Vladimir Sementsov-Ogievskiy]

17.06.2021 18:52, Max Reitz wrote:
> bdrv_co_block_status() does it for us, we do not need to do it here.
>
> The advantage of not capping *pnum is that bdrv_co_block_status() can
> cache larger data regions than requested by its caller.
>
> Signed-off-by: Max Reitz <mreitz@redhat.com>


Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>


> ---
>   block/gluster.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/block/gluster.c b/block/gluster.c
> index e8ee14c8e9..8ef7bb18d5 100644
> --- a/block/gluster.c
> +++ b/block/gluster.c
> @@ -1461,7 +1461,8 @@ exit:
>    * the specified offset) that are known to be in the same
>    * allocated/unallocated state.
>    *
> - * 'bytes' is the max value 'pnum' should be set to.
> + * 'bytes' is a soft cap for 'pnum'.  If the information is free, 'pnum' may
> + * well exceed it.
>    *
>    * (Based on raw_co_block_status() from file-posix.c.)
>    */
> @@ -1500,12 +1501,12 @@ static int coroutine_fn 
> qemu_gluster_co_block_status(BlockDriverState *bs,
>       } else if (data == offset) {
>           /* On a data extent, compute bytes to the end of the extent,
>            * possibly including a partial sector at EOF. */
> -        *pnum = MIN(bytes, hole - offset);
> +        *pnum = hole - offset;
>           ret = BDRV_BLOCK_DATA;

Interesting, isn't it a bug that we don't ROUND_UP *pnum to request_alignment 
here like it is done in file-posix ?

>       } else {
>           /* On a hole, compute bytes to the beginning of the next extent.  */
>           assert(hole == offset);
> -        *pnum = MIN(bytes, data - offset);
> +        *pnum = data - offset;
>           ret = BDRV_BLOCK_ZERO;
>       }
>   


--
Best regards,
Vladimir