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

Benjamin Marzinski
2025-03-19T19:50:45Z

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