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Date: Sat, 18 Jan 2014 00:50:33 +0100
From: Max Reitz <mreitz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 26/29] blkdebug: Make required alignment
	configurable
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To: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org
Cc: pbonzini@redhat.com, pl@kamp.de, xiawenc@linux.vnet.ibm.com, stefanha@redhat.com

On 17.01.2014 15:15, Kevin Wolf wrote:
> The new 'align' option of blkdebug can be used in order to emulate
> backends with a required 4k alignment on hosts which only really requir=
e
> 512 byte alignment.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block/blkdebug.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)

The patch itself is okay, but will have to be rebased on the=20
blkdebug/blkverify series =96 specifically, we'll need to add this new=20
option to qapi-schema.json (BlockdevOptionsBlkdebug).

> diff --git a/block/blkdebug.c b/block/blkdebug.c
> index ebc5f13..dc4ba46 100644
> --- a/block/blkdebug.c
> +++ b/block/blkdebug.c
> @@ -346,6 +346,11 @@ static QemuOptsList runtime_opts =3D {
>               .type =3D QEMU_OPT_STRING,
>               .help =3D "[internal use only, will be removed]",
>           },
> +        {
> +            .name =3D "align",
> +            .type =3D QEMU_OPT_SIZE,
> +            .help =3D "Required alignment in bytes",
> +        },
>           { /* end of list */ }
>       },
>   };
> @@ -357,6 +362,7 @@ static int blkdebug_open(BlockDriverState *bs, QDic=
t *options, int flags,
>       QemuOpts *opts;
>       Error *local_err =3D NULL;
>       const char *filename, *config;
> +    uint64_t align;
>       int ret;
>  =20
>       opts =3D qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
> @@ -394,6 +400,16 @@ static int blkdebug_open(BlockDriverState *bs, QDi=
ct *options, int flags,
>           goto fail;
>       }
>  =20
> +    /* Set request alignment */
> +    align =3D qemu_opt_get_size(opts, "align", bs->request_alignment);
> +    if (align > 0 && align < INT_MAX && !(align & (align - 1))) {

Hm, I like that test to check whether align is a power of two. ;-)

Max

> +        bs->request_alignment =3D align;
> +    } else {
> +        error_setg(errp, "Invalid alignment");
> +        ret =3D -EINVAL;
> +        goto fail;
> +    }
> +
>       ret =3D 0;
>   fail:
>       qemu_opts_del(opts);