On Thu, 06/23 16:37, Eric Blake wrote:
> During bdrv_merge_limits(), we were computing initial limits
> based on another BDS in two places. At first glance, the two
> computations are not identical (one is doing straight copying,
> the other is doing merging towards or away from zero) - but
> when you realize that the first round is starting with all-0
> memory, all of the merging happens to work. Factoring out the
> merging makes it easier to track how two BDS limits are merged,
> in case we have future reasons to merge in even more limits.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
>
> ---
> v3: Split raw block driver changes to its own patch, make new
> function static
> v2: new patch
> ---
> block/io.c | 31 +++++++++++++------------------
> 1 file changed, 13 insertions(+), 18 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index 0f15d05..69dbbd3 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -67,6 +67,17 @@ static void bdrv_parent_drained_end(BlockDriverState *bs)
> }
> }
>
> +static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
> +{
> + dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer);
> + dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer);
> + dst->opt_mem_alignment = MAX(dst->opt_mem_alignment,
> + src->opt_mem_alignment);
> + dst->min_mem_alignment = MAX(dst->min_mem_alignment,
> + src->min_mem_alignment);
> + dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
> +}
> +
> void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
> {
> BlockDriver *drv = bs->drv;
> @@ -88,11 +99,7 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error
> **errp)
> error_propagate(errp, local_err);
> return;
> }
> - bs->bl.opt_transfer = bs->file->bs->bl.opt_transfer;
> - bs->bl.max_transfer = bs->file->bs->bl.max_transfer;
> - bs->bl.min_mem_alignment = bs->file->bs->bl.min_mem_alignment;
> - bs->bl.opt_mem_alignment = bs->file->bs->bl.opt_mem_alignment;
> - bs->bl.max_iov = bs->file->bs->bl.max_iov;
> + bdrv_merge_limits(&bs->bl, &bs->file->bs->bl);
> } else {
> bs->bl.min_mem_alignment = 512;
> bs->bl.opt_mem_alignment = getpagesize();
> @@ -107,19 +114,7 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error
> **errp)
> error_propagate(errp, local_err);
> return;
> }
> - bs->bl.opt_transfer = MAX(bs->bl.opt_transfer,
> - bs->backing->bs->bl.opt_transfer);
> - bs->bl.max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
> - bs->backing->bs->bl.max_transfer);
> - bs->bl.opt_mem_alignment =
> - MAX(bs->bl.opt_mem_alignment,
> - bs->backing->bs->bl.opt_mem_alignment);
> - bs->bl.min_mem_alignment =
> - MAX(bs->bl.min_mem_alignment,
> - bs->backing->bs->bl.min_mem_alignment);
> - bs->bl.max_iov =
> - MIN(bs->bl.max_iov,
> - bs->backing->bs->bl.max_iov);
> + bdrv_merge_limits(&bs->bl, &bs->backing->bs->bl);
> }
>
> /* Then let the driver override it */
> --
> 2.5.5
>
Reviewed-by: Fam Zheng <f...@redhat.com>
