On 8/1/23 07:14, Bart Van Assche wrote:
> Writes in sequential write required zones must happen at the write
> pointer. Even if the submitter of the write commands (e.g. a filesystem)
> submits writes for sequential write required zones in order, the block
> layer or the storage controller may reorder these write commands.
>
> The zone locking mechanism in the mq-deadline I/O scheduler serializes
> write commands for sequential zones. Some but not all storage controllers
> require this serialization. Introduce a new request queue flag to allow
> block drivers to indicate that they preserve the order of write commands
> and thus do not require serialization of writes per zone.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
> Cc: Ming Lei <ming.lei@xxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Looks OK.
Very minor nit below.
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
> ---
> include/linux/blkdev.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 2f5371b8482c..de5e05cc34fa 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -534,6 +534,11 @@ struct request_queue {
> #define QUEUE_FLAG_NONROT 6 /* non-rotational device (SSD) */
> #define QUEUE_FLAG_VIRT QUEUE_FLAG_NONROT /* paravirt device */
> #define QUEUE_FLAG_IO_STAT 7 /* do disk/partitions IO accounting */
> +/*
> + * Do not serialize sequential writes (REQ_OP_WRITE, REQ_OP_WRITE_ZEROES) sent
> + * to a sequential write required zone (BLK_ZONE_TYPE_SEQWRITE_REQ).
> + */
I would be very explicit here, for this to be clear to people who are not
familiar with zone device write operation handling. Something like:
/*
* The device supports not using the zone write locking mechanism to serialize
* write operations (REQ_OP_WRITE, REQ_OP_WRITE_ZEROES) issued to a sequential
* write required zone (BLK_ZONE_TYPE_SEQWRITE_REQ).
*/
> +#define QUEUE_FLAG_NO_ZONE_WRITE_LOCK 8
> #define QUEUE_FLAG_NOXMERGES 9 /* No extended merges */
> #define QUEUE_FLAG_ADD_RANDOM 10 /* Contributes to random pool */
> #define QUEUE_FLAG_SYNCHRONOUS 11 /* always completes in submit context */
> @@ -597,6 +602,11 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
> #define blk_queue_skip_tagset_quiesce(q) \
> test_bit(QUEUE_FLAG_SKIP_TAGSET_QUIESCE, &(q)->queue_flags)
>
> +static inline bool blk_queue_no_zone_write_lock(struct request_queue *q)
> +{
> + return test_bit(QUEUE_FLAG_NO_ZONE_WRITE_LOCK, &q->queue_flags);
> +}
> +
> extern void blk_set_pm_only(struct request_queue *q);
> extern void blk_clear_pm_only(struct request_queue *q);
>
--
Damien Le Moal
Western Digital Research
