Re: [Qemu-block] [RFC PATCH 11/41] vvfat: Implement .bdrv_child_perm()

[Max Reitz]

On 13.02.2017 18:22, Kevin Wolf wrote:
> vvfat is the last remaining driver that can have children, but doesn't
> implement .bdrv_child_perm() yet. The default handlers aren't suitable
> here, so let's implement a very simple driver-specific one that protects
> the internal child from being used by other users as good as our
> permissions permit.
> 
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  block/vvfat.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/block/vvfat.c b/block/vvfat.c
> index c6bf67e..7246432 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -3052,6 +3052,18 @@ err:
>      return ret;
>  }
>  
> +static void vvfat_child_perm(BlockDriverState *bs, BdrvChild *c,
> +                             const BdrvChildRole *role,
> +                             uint64_t perm, uint64_t shared,
> +                             uint64_t *nperm, uint64_t *nshared)
> +{
> +    assert(role == &child_vvfat_qcow);
> +
> +    /* This is a private node, nobody should try to attach to it */
> +    *nperm = BLK_PERM_WRITE;
> +    *nshared = 0;

0 for shared is probably enough to ward every other access off, but
maybe we should still pro forma request consistent read access...?

Max

> +}
> +
>  static void vvfat_close(BlockDriverState *bs)
>  {
>      BDRVVVFATState *s = bs->opaque;
> @@ -3077,6 +3089,7 @@ static BlockDriver bdrv_vvfat = {
>      .bdrv_file_open         = vvfat_open,
>      .bdrv_refresh_limits    = vvfat_refresh_limits,
>      .bdrv_close             = vvfat_close,
> +    .bdrv_child_perm        = vvfat_child_perm,
>  
>      .bdrv_co_preadv         = vvfat_co_preadv,
>      .bdrv_co_pwritev        = vvfat_co_pwritev,
>

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