Re: [PATCH v9 5/7] config: add check to block layer

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 2022/09/10 14:27, Sam Li wrote:
> Putting zoned/non-zoned BlockDrivers on top of each other is not
> allowed.
> 
> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  block.c                          | 14 ++++++++++++++
>  block/file-posix.c               | 14 ++++++++++++++
>  block/raw-format.c               |  1 +
>  include/block/block_int-common.h |  5 +++++
>  4 files changed, 34 insertions(+)
> 
> diff --git a/block.c b/block.c
> index bc85f46eed..dad2ed3959 100644
> --- a/block.c
> +++ b/block.c
> @@ -7947,6 +7947,20 @@ void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
>          return;
>      }
>  
> +    /*
> +     * Non-zoned block drivers do not follow zoned storage constraints
> +     * (i.e. sequential writes to zones). Refuse mixing zoned and non-zoned
> +     * drivers in a graph.
> +     */
> +    if (!parent_bs->drv->supports_zoned_children &&
> +        child_bs->bl.zoned == BLK_Z_HM) {

Shouldn't this be "child_bs->bl.zoned != BLK_Z_NONE" ?

> +        error_setg(errp, "Cannot add a %s child to a %s parent",
> +                   child_bs->bl.zoned == BLK_Z_HM ? "zoned" : "non-zoned",
> +                   parent_bs->drv->supports_zoned_children ?
> +                   "support zoned children" : "not support zoned children");
> +        return;
> +    }
> +
>      if (!QLIST_EMPTY(&child_bs->parents)) {
>          error_setg(errp, "The node %s already has a parent",
>                     child_bs->node_name);
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 4edfa25d04..354de22860 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -779,6 +779,20 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
>              goto fail;
>          }
>      }
> +#ifdef CONFIG_BLKZONED
> +    /*
> +     * The kernel page chache does not reliably work for writes to SWR zones
> +     * of zoned block device because it can not guarantee the order of writes.
> +     */
> +    if (strcmp(bs->drv->format_name, "zoned_host_device") == 0) {
> +        if (!(s->open_flags & O_DIRECT)) {
> +            error_setg(errp, "driver=zoned_host_device was specified, but it "
> +                             "requires cache.direct=on, which was not specified.");
> +            ret = -EINVAL;

This line is not needed. Simply "return -EINVAL;".

> +            return ret; /* No host kernel page cache */
> +        }
> +    }
> +#endif
>  
>      if (S_ISBLK(st.st_mode)) {
>  #ifdef BLKDISCARDZEROES
> diff --git a/block/raw-format.c b/block/raw-format.c
> index 6b20bd22ef..9441536819 100644
> --- a/block/raw-format.c
> +++ b/block/raw-format.c
> @@ -614,6 +614,7 @@ static void raw_child_perm(BlockDriverState *bs, BdrvChild *c,
>  BlockDriver bdrv_raw = {
>      .format_name          = "raw",
>      .instance_size        = sizeof(BDRVRawState),
> +    .supports_zoned_children = true,
>      .bdrv_probe           = &raw_probe,
>      .bdrv_reopen_prepare  = &raw_reopen_prepare,
>      .bdrv_reopen_commit   = &raw_reopen_commit,
> diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
> index 078ddd7e67..043aa161a0 100644
> --- a/include/block/block_int-common.h
> +++ b/include/block/block_int-common.h
> @@ -127,6 +127,11 @@ struct BlockDriver {
>       */
>      bool is_format;
>  
> +    /*
> +     * Set to true if the BlockDriver supports zoned children.
> +     */
> +    bool supports_zoned_children;
> +
>      /*
>       * Drivers not implementing bdrv_parse_filename nor bdrv_open should have
>       * this field set to true, except ones that are defined only by their

-- 
Damien Le Moal
Western Digital Research