On 7/11/23 03:01, 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 flag such that block drivers
> can request pipelining of writes for sequential write required zones.
>
> An example of a storage controller standard that requires write
> serialization is AHCI (Advanced Host Controller Interface). Submitting
> commands to AHCI controllers happens by writing a bit pattern into a
> register. Each set bit corresponds to an active command. This mechanism
> does not preserve command ordering information.
>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
> include/linux/blkdev.h | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ed44a997f629..805012c5a6ab 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -534,6 +534,8 @@ 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 */
> +/* Writes for sequential write required zones may be pipelined. */
> +#define QUEUE_FLAG_PIPELINE_ZONED_WRITES 8
I am not a big fan of this name as "pipeline" does not necessarily imply "high
queue depth write". What about simply calling this
QUEUE_FLAG_NO_ZONE_WRITE_LOCK, indicating that there is no need to write-lock
zones ?
> #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 */
> @@ -596,6 +598,11 @@ 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_pipeline_zoned_writes(struct request_queue *q)
> +{
> + return test_bit(QUEUE_FLAG_PIPELINE_ZONED_WRITES, &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
