Re: [RFC PATCH -next v3 06/10] dm: add BLK_FEAT_WRITE_ZEROES_UNMAP support

[Benjamin Marzinski <bmarzins@redhat.com>]

On Tue, Mar 18, 2025 at 03:35:41PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
> 
> Set the BLK_FEAT_WRITE_ZEROES_UNMAP feature on stacking queue limits by
> default. This feature shall be disabled if any underlying device does
> not support it.
> 
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>

> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> ---
>  drivers/md/dm-table.c | 7 +++++--
>  drivers/md/dm.c       | 1 +
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 453803f1edf5..d4a483287e26 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -598,7 +598,8 @@ int dm_split_args(int *argc, char ***argvp, char *input)
>  static void dm_set_stacking_limits(struct queue_limits *limits)
>  {
>  	blk_set_stacking_limits(limits);
> -	limits->features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT | BLK_FEAT_POLL;
> +	limits->features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT | BLK_FEAT_POLL |
> +			    BLK_FEAT_WRITE_ZEROES_UNMAP;
>  }
>  
>  /*
> @@ -1848,8 +1849,10 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
>  		limits->discard_alignment = 0;
>  	}
>  
> -	if (!dm_table_supports_write_zeroes(t))
> +	if (!dm_table_supports_write_zeroes(t)) {
>  		limits->max_write_zeroes_sectors = 0;
> +		limits->features &= ~BLK_FEAT_WRITE_ZEROES_UNMAP;
> +	}
>  
>  	if (!dm_table_supports_secure_erase(t))
>  		limits->max_secure_erase_sectors = 0;
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 5ab7574c0c76..b59c3dbeaaf1 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1096,6 +1096,7 @@ void disable_write_zeroes(struct mapped_device *md)
>  
>  	/* device doesn't really support WRITE ZEROES, disable it */
>  	limits->max_write_zeroes_sectors = 0;
> +	limits->features &= ~BLK_FEAT_WRITE_ZEROES_UNMAP;
>  }
>  
>  static bool swap_bios_limit(struct dm_target *ti, struct bio *bio)
> -- 
> 2.46.1