On 8/12/23 06:35, Bart Van Assche wrote:
> Many but not all storage controllers require serialization of zoned writes.
> Introduce a new request queue limit member variable
> (driver_preserves_write_order) that allows block drivers to indicate that
> the order of write commands is preserved and hence that serialization of
> writes per zone is not required.
>
> Make disk_set_zoned() set 'use_zone_write_lock' only if the block device
> has zones and if the block driver does not preserve the order of write
> requests.
>
> Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
> block/blk-settings.c | 7 +++++++
> include/linux/blkdev.h | 10 ++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 0046b447268f..3a7748af1bef 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -56,6 +56,8 @@ void blk_set_default_limits(struct queue_limits *lim)
> lim->alignment_offset = 0;
> lim->io_opt = 0;
> lim->misaligned = 0;
> + lim->driver_preserves_write_order = false;
> + lim->use_zone_write_lock = false;
> lim->zoned = BLK_ZONED_NONE;
> lim->zone_write_granularity = 0;
> lim->dma_alignment = 511;
> @@ -685,6 +687,9 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
> b->max_secure_erase_sectors);
> t->zone_write_granularity = max(t->zone_write_granularity,
> b->zone_write_granularity);
> + /* Request-based stacking drivers do not reorder requests. */
> + t->driver_preserves_write_order = b->driver_preserves_write_order;
> + t->use_zone_write_lock = b->use_zone_write_lock;
I do not think this is correct as the last target of a multi target device will
dictate the result, regardless of the other targets. So this should be something
like:
t->driver_preserves_write_order = t->driver_preserves_write_order &&
b->driver_preserves_write_order;
t->use_zone_write_lock =
t->use_zone_write_lock || b->use_zone_write_lock;
However, given that driver_preserves_write_order is initialized as false, this
would always be false. Not sure how to handle that...
> t->zoned = max(t->zoned, b->zoned);
> return ret;
> }
> @@ -949,6 +954,8 @@ void disk_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
> }
>
> q->limits.zoned = model;
> + q->limits.use_zone_write_lock = model != BLK_ZONED_NONE &&
> + !q->limits.driver_preserves_write_order;
I think this needs a comment to explain the condition as it takes a while to
understand it.
> if (model != BLK_ZONED_NONE) {
> /*
> * Set the zone write granularity to the device logical block
You also should set use_zone_write_lock to false in disk_clear_zone_settings().
In patch 9, ufshcd_auto_hibern8_update() changes the value of
driver_preserves_write_order, which will change the value of use_zone_write_lock
only if disk_set_zoned() is called again after ufshcd_auto_hibern8_update(). Is
that the case ? Is the drive revalidated always after
ufshcd_auto_hibern8_update() is executed ?
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 2f5371b8482c..2c090a28ec78 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -316,6 +316,16 @@ struct queue_limits {
> unsigned char misaligned;
> unsigned char discard_misaligned;
> unsigned char raid_partial_stripes_expensive;
> + /*
> + * Whether or not the block driver preserves the order of write
> + * requests. Set by the block driver.
> + */
> + bool driver_preserves_write_order;
> + /*
> + * Whether or not zone write locking should be used. Set by
> + * disk_set_zoned().
> + */
> + bool use_zone_write_lock;
> enum blk_zoned_model zoned;
>
> /*
--
Damien Le Moal
Western Digital Research
