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Date: Mon, 25 Nov 2013 11:06:55 +0100
From: Peter Lieven <pl@kamp.de>
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Subject: Re: [Qemu-devel] [PATCH v3 05/19] block: handle ENOTSUP from
 discard in generic code
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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:
> Similar to write_zeroes, let the generic code receive a ENOTSUP for
> discard operations.  Since bdrv_discard has advisory semantics,
> we can just swallow the error.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   block.c           |  2 +-
>   block/raw-posix.c | 12 ++++++------
>   2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/block.c b/block.c
> index f9674d9..b18ee6b 100644
> --- a/block.c
> +++ b/block.c
> @@ -4364,7 +4364,7 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
>                   ret = co.ret;
>               }
>           }
> -        if (ret) {
> +        if (ret && ret != -ENOTSUP) {
>               return ret;
>           }
>   
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index f836c8e..cfa3162 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -323,10 +323,10 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
>       }
>   #endif
>   
> -    s->has_discard = 1;
> +    s->has_discard = true;
>   #ifdef CONFIG_XFS
>       if (platform_test_xfs_fd(s->fd)) {
> -        s->is_xfs = 1;
> +        s->is_xfs = true;
>       }
>   #endif
>   
> @@ -698,8 +698,8 @@ static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)
>       int ret = -EOPNOTSUPP;
>       BDRVRawState *s = aiocb->bs->opaque;
>   
> -    if (s->has_discard == 0) {
> -        return 0;
> +    if (!s->has_discard) {
> +        return -ENOTSUP;
>       }
>   
>       if (aiocb->aio_type & QEMU_AIO_BLKDEV) {
> @@ -734,8 +734,8 @@ static ssize_t handle_aiocb_discard(RawPosixAIOData *aiocb)
>   
>       if (ret == -ENODEV || ret == -ENOSYS || ret == -EOPNOTSUPP ||
>           ret == -ENOTTY) {
> -        s->has_discard = 0;
> -        ret = 0;
> +        s->has_discard = false;
> +        ret = -ENOTSUP;
>       }
>       return ret;
>   }
wouldn't it make sense to return -ENOTSUP in other drivers a well if the
operation is not supported and not return 0?

Otherwise:
Reviewed-by: Peter Lieven <pl@kamp.de>