[PATCH v4 2/5] scsi: core: Support setting BLK_MQ_F_BLOCKING

Bart Van Assche
2023-05-29T20:26:52Z

Prepare for adding code in ufshcd_queuecommand() that may sleep. This
patch is similar to a patch posted last year by Mike Christie. See also
https://lore.kernel.org/all/20220308003957.123312-2-michael.christie@oracle.com/

Cc: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/hosts.c | 1 +
drivers/scsi/scsi_lib.c | 11 ++++-------
include/scsi/scsi_host.h | 6 ++++++
3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index f0bc8bbb3938..198edf03f929 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -441,6 +441,7 @@ struct Scsi_Host *scsi_host_alloc(const struct scsi_host_template *sht, int priv
shost->cmd_per_lun = sht->cmd_per_lun;
shost->no_write_same = sht->no_write_same;
shost->host_tagset = sht->host_tagset;
+ shost->queuecommand_may_block = sht->queuecommand_may_block;

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 5f29faa0560f..e0b5d35e7949 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1981,6 +1981,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
tag_set->flags |=
BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);
+ if (shost->queuecommand_may_block)
+ tag_set->flags |= BLK_MQ_F_BLOCKING;
tag_set->driver_data = shost;
if (shost->host_tagset)
tag_set->flags |= BLK_MQ_F_TAG_HCTX_SHARED;
@@ -2969,13 +2971,8 @@ scsi_host_block(struct Scsi_Host *shost)
}
}

- /*
- * SCSI never enables blk-mq's BLK_MQ_F_BLOCKING flag so
- * calling synchronize_rcu() once is enough.
- */
- WARN_ON_ONCE(shost->tag_set.flags & BLK_MQ_F_BLOCKING);
-
- synchronize_rcu();
+ /* Wait for ongoing scsi_queue_rq() calls to finish. */
+ blk_mq_wait_quiesce_done(&shost->tag_set);

return 0;
}
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 0f29799efa02..70b7475dcf56 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -458,6 +458,9 @@ struct scsi_host_template {
/* True if the host uses host-wide tagspace */
unsigned host_tagset:1;

+ /* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
+ unsigned queuecommand_may_block:1;
+
/*
* Countdown for host blocking with no commands outstanding.
*/
@@ -653,6 +656,9 @@ struct Scsi_Host {
/* True if the host uses host-wide tagspace */
unsigned host_tagset:1;

+ /* The queuecommand callback may block. See also BLK_MQ_F_BLOCKING. */
+ unsigned queuecommand_may_block:1;
+
/* Host responded with short (<36 bytes) INQUIRY result */
unsigned short_inquiry:1;