Re: [PATCH v12 5/7] config: add check to block layer

[Dmitry Fomichev]

On Sun, 2022-10-16 at 22:51 +0800, 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>
> Reviewed-by: Hannes Reinecke <hare@suse.de>

Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>

> ---
>  block.c                          | 19 +++++++++++++++++++
>  block/file-posix.c               | 12 ++++++++++++
>  block/raw-format.c               |  1 +
>  include/block/block_int-common.h |  5 +++++
>  4 files changed, 37 insertions(+)
> 
> diff --git a/block.c b/block.c
> index 1fbf6b9e69..5d6fa4a25a 100644
> --- a/block.c
> +++ b/block.c
> @@ -7951,6 +7951,25 @@ 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) {
> +        /*
> +         * The host-aware model allows zoned storage constraints and random
> +         * write. Allow mixing host-aware and non-zoned drivers. Using
> +         * host-aware device as a regular device.
> +         */
> +        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 bd28e3eaea..7c5a330fc1 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -776,6 +776,18 @@ static int raw_open_common(BlockDriverState *bs, QDict
> *options,
>              goto fail;
>          }
>      }
> +#ifdef CONFIG_BLKZONED
> +    /*
> +     * The kernel page cache 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) &&
> +        (!(s->open_flags & O_DIRECT))) {
> +        error_setg(errp, "driver=zoned_host_device was specified, but it "
> +                   "requires cache.direct=on, which was not specified.");
> +        return -EINVAL; /* No host kernel page cache */
> +    }
> +#endif
>  
>      if (S_ISBLK(st.st_mode)) {
>  #ifdef __linux__
> diff --git a/block/raw-format.c b/block/raw-format.c
> index bac43f1d25..18dc52a150 100644
> --- a/block/raw-format.c
> +++ b/block/raw-format.c
> @@ -615,6 +615,7 @@ 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 cdc06e77a6..37dddc603c 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