Re: [Qemu-devel] [PATCH 1/2] block: sync bdrv_co_get_block_status_above() with bdrv_is_allocated_above()

[Vladimir Sementsov-Ogievskiy]

On 09.09.2016 15:31, Denis V. Lunev wrote:
> They should work very similar, covering same areas if backing store is
> shorter than the image. This change is necessary for the followup patch
> switching to bdrv_get_block_status_above() in mirror to avoid assert
> in check_block.
>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Stefan Hajnoczi <address@hidden>
> CC: Fam Zheng <address@hidden>
> CC: Kevin Wolf <address@hidden>
> CC: Max Reitz <address@hidden>
> CC: Jeff Cody <address@hidden>
> ---
>   block/io.c | 26 ++++++++++++++++++++------
>   1 file changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index 420944d..0422123 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1745,14 +1745,28 @@ static int64_t coroutine_fn 
> bdrv_co_get_block_status_above(BlockDriverState *bs,
>   
>       assert(bs != base);
>       for (p = bs; p != base; p = backing_bs(p)) {
> -        ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, pnum, file);
> -        if (ret < 0 || ret & BDRV_BLOCK_ALLOCATED) {
> -            break;
> +        int sc;
> +        ret = bdrv_co_get_block_status(p, sector_num, nb_sectors, &sc, file);
> +        if (ret < 0) {
> +            return ret;
> +        } else if (ret & BDRV_BLOCK_ALLOCATED) {
> +            *pnum = sc;
> +            return ret;
> +        }
> +
> +        /*
> +         * [sector_num, nb_sectors] is unallocated on top but intermediate
> +         * might have
> +         *
> +         * [sector_num+x, nr_sectors] allocated.
> +         */

this comment is unrelated here, as you reduce nb_sectors (used in 
bdrv_co_get_block_status() above) in the following "if"

> +        if (nb_sectors > sc &&
> +            (p == bs || sector_num + sc < p->total_sectors)) {
> +            nb_sectors = sc;
>           }
> -        /* [sector_num, pnum] unallocated on this layer, which could be only
> -         * the first part of [sector_num, nb_sectors].  */
> -        nb_sectors = MIN(nb_sectors, *pnum);
>       }
> +
> +    *pnum = nb_sectors;
>       return ret;
>   }
>   


--
Best regards,
Vladimir