[PATCH v5 2/3] scsi: core: Support disabling fair tag sharing

Bart Van Assche
2023-11-14T18:04:59Z

Allow SCSI drivers to disable the block layer fair tag sharing algorithm.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Yu Kuai <yukuai1@huaweicloud.com>
Cc: Ed Tsai <ed.tsai@mediatek.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/hosts.c | 1 +
drivers/scsi/scsi_lib.c | 2 ++
include/scsi/scsi_host.h | 6 ++++++
3 files changed, 9 insertions(+)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index d7f51b84f3c7..872f87001374 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -442,6 +442,7 @@ struct Scsi_Host *scsi_host_alloc(const struct scsi_host_template *sht, int priv
shost->no_write_same = sht->no_write_same;
shost->host_tagset = sht->host_tagset;
shost->queuecommand_may_block = sht->queuecommand_may_block;
+ shost->disable_fair_tag_sharing = sht->disable_fair_tag_sharing;

if (shost_eh_deadline == -1 || !sht->eh_host_reset_handler)
shost->eh_deadline = -1;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index cf3864f72093..291fbfacf542 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1984,6 +1984,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
if (shost->queuecommand_may_block)
tag_set->flags |= BLK_MQ_F_BLOCKING;
+ if (shost->disable_fair_tag_sharing)
+ tag_set->flags |= BLK_MQ_F_DISABLE_FAIR_TAG_SHARING;
tag_set->driver_data = shost;
if (shost->host_tagset)
tag_set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 3b907fc2ef08..04238ae9e22c 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -464,6 +464,9 @@ struct scsi_host_template {
/* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
unsigned queuecommand_may_block:1;

+ /* See also BLK_MQ_F_DISABLE_FAIR_TAG_SHARING. */
+ unsigned disable_fair_tag_sharing:1;
+
/*
* Countdown for host blocking with no commands outstanding.
*/
@@ -662,6 +665,9 @@ struct Scsi_Host {
/* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
unsigned queuecommand_may_block:1;

+ /* See also BLK_MQ_F_DISABLE_FAIR_TAG_SHARING. */
+ unsigned disable_fair_tag_sharing:1;
+
/* Host responded with short (<36 bytes) INQUIRY result */
unsigned short_inquiry:1;