Re: [PATCH v16 07/26] block: Support block drivers that preserve the order of write requests

Damien Le Moal
2024-11-19T07:37:18Z

On 11/19/24 09:27, Bart Van Assche wrote:
> Many but not all storage controllers require serialization of zoned
> writes. Introduce a new request queue limit member variable related to
> write serialization. 'driver_preserves_write_order' allows block drivers
> to indicate that the order of write commands is preserved per hardware
> queue and hence that serialization of writes per zone is not required if
> all pending writes are submitted to the same hardware queue.
>
> Cc: Damien Le Moal <dlemoal@kernel.org>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Nitesh Shetty <nj.shetty@samsung.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> block/blk-settings.c | 2 ++
> include/linux/blkdev.h | 5 +++++
> 2 files changed, 7 insertions(+)
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index f1d4dfdc37a7..329d8b65a8d7 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -633,6 +633,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
> }
> t->max_secure_erase_sectors = min_not_zero(t->max_secure_erase_sectors,
> b->max_secure_erase_sectors);
> + t->driver_preserves_write_order = t->driver_preserves_write_order &&
> + b->driver_preserves_write_order;
> t->zone_write_granularity = max(t->zone_write_granularity,
> b->zone_write_granularity);
> if (!(t->features & BLK_FEAT_ZONED)) {
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index a1fd0ddce5cf..72be33d02d1f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -397,6 +397,11 @@ struct queue_limits {
>
> unsigned int max_open_zones;
> unsigned int max_active_zones;
> + /*
> + * Whether or not the block driver preserves the order of write
> + * requests. Set by the block driver.
> + */
> + bool driver_preserves_write_order;

Why not make this a q->features flag ?

>
> /*
> * Drivers that set dma_alignment to less than 511 must be prepared to

--
Damien Le Moal
Western Digital Research