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Date: Mon, 25 Nov 2013 10:09:29 +0100
From: Peter Lieven <pl@kamp.de>
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Subject: Re: [Qemu-devel] [PATCH v3 01/19] block: generalize BlockLimits
 handling to cover bdrv_aio_discard too
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To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, ronniesahlberg@gmail.com, stefanha@redhat.com

On 22.11.2013 13:39, Paolo Bonzini wrote:
> bdrv_co_discard is only covering drivers which have a .bdrv_co_discard()
> implementation, but not those with .bdrv_aio_discard(). Not very nice,
> and easy to avoid.
>
> Suggested-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   block.c | 80 +++++++++++++++++++++++++++++++++--------------------------------
>   1 file changed, 41 insertions(+), 39 deletions(-)
>
> diff --git a/block.c b/block.c
> index e22b55f..1b3e8b2 100644
> --- a/block.c
> +++ b/block.c
> @@ -4288,6 +4288,8 @@ static void coroutine_fn bdrv_discard_co_entry(void *opaque)
>   int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
>                                    int nb_sectors)
>   {
> +    int max_discard;
> +
>       if (!bs->drv) {
>           return -ENOMEDIUM;
>       } else if (bdrv_check_request(bs, sector_num, nb_sectors)) {
> @@ -4305,55 +4307,55 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
>           return 0;
>       }
>   
> -    if (bs->drv->bdrv_co_discard) {
> -        int max_discard = bs->bl.max_discard ?
> -                          bs->bl.max_discard : MAX_DISCARD_DEFAULT;
> +    if (!bs->drv->bdrv_co_discard && !bs->drv->bdrv_aio_discard) {
> +        return 0;
> +    }
>   
> -        while (nb_sectors > 0) {
> -            int ret;
> -            int num = nb_sectors;
> +    max_discard = bs->bl.max_discard ?  bs->bl.max_discard : MAX_DISCARD_DEFAULT;
> +    while (nb_sectors > 0) {
> +        int ret;
> +        int num = nb_sectors;
>   
> -            /* align request */
> -            if (bs->bl.discard_alignment &&
> -                num >= bs->bl.discard_alignment &&
> -                sector_num % bs->bl.discard_alignment) {
> -                if (num > bs->bl.discard_alignment) {
> -                    num = bs->bl.discard_alignment;
> -                }
> -                num -= sector_num % bs->bl.discard_alignment;
> +        /* align request */
> +        if (bs->bl.discard_alignment &&
> +            num >= bs->bl.discard_alignment &&
> +            sector_num % bs->bl.discard_alignment) {
> +            if (num > bs->bl.discard_alignment) {
> +                num = bs->bl.discard_alignment;
>               }
> +            num -= sector_num % bs->bl.discard_alignment;
> +        }
>   
> -            /* limit request size */
> -            if (num > max_discard) {
> -                num = max_discard;
> -            }
> +        /* limit request size */
> +        if (num > max_discard) {
> +            num = max_discard;
> +        }
>   
> +        if (bs->drv->bdrv_co_discard) {
>               ret = bs->drv->bdrv_co_discard(bs, sector_num, num);
> -            if (ret) {
> -                return ret;
> +        } else {
> +            BlockDriverAIOCB *acb;
> +            CoroutineIOCompletion co = {
> +                .coroutine = qemu_coroutine_self(),
> +            };
> +
> +            acb = bs->drv->bdrv_aio_discard(bs, sector_num, nb_sectors,
> +                                            bdrv_co_io_em_complete, &co);
> +            if (acb == NULL) {
> +                return -EIO;
> +            } else {
> +                qemu_coroutine_yield();
> +                ret = co.ret;
>               }
> -
> -            sector_num += num;
> -            nb_sectors -= num;
>           }
> -        return 0;
> -    } else if (bs->drv->bdrv_aio_discard) {
> -        BlockDriverAIOCB *acb;
> -        CoroutineIOCompletion co = {
> -            .coroutine = qemu_coroutine_self(),
> -        };
> -
> -        acb = bs->drv->bdrv_aio_discard(bs, sector_num, nb_sectors,
> -                                        bdrv_co_io_em_complete, &co);
> -        if (acb == NULL) {
> -            return -EIO;
> -        } else {
> -            qemu_coroutine_yield();
> -            return co.ret;
> +        if (ret) {
> +            return ret;
>           }
> -    } else {
> -        return 0;
> +
> +        sector_num += num;
> +        nb_sectors -= num;
>       }
> +    return 0;
>   }
>   
>   int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
Reviewed-by: Peter Lieven <pl@kamp.de>