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From: Hannes Reinecke <hare@suse.de>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: James Bottomley <james.bottomley@hansenpartnership.com>,
	Christoph Hellwig <hch@lst.de>,
	John Garry <john.garry@huawei.com>,
	linux-scsi@vger.kernel.org, Hannes Reinecke <hare@suse.de>
Subject: [PATCH 12/31] scsi: implement reserved command handling
Date: Mon, 22 Feb 2021 14:23:46 +0100
Message-ID: <20210222132405.91369-13-hare@suse.de> (raw)
In-Reply-To: <20210222132405.91369-1-hare@suse.de>

Quite some drivers are using management commands internally, which
typically use the same hardware tag pool (ie they are being allocated
from the same hardware resources) as the 'normal' I/O commands.
These commands are set aside before allocating the block-mq tag bitmap,
so they'll never show up as busy in the tag map.
The block-layer, OTOH, already has 'reserved_tags' to handle precisely
this situation.
So this patch adds a new field 'nr_reserved_cmds' to the SCSI host
template to instruct the block layer to set aside a tag space for these
management commands by using reserved tags.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/hosts.c     |  3 +++
 drivers/scsi/scsi_lib.c  | 10 +++++++++-
 include/scsi/scsi_host.h | 22 +++++++++++++++++++++-
 3 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 2f162603876f..661ed7696562 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -469,6 +469,9 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	if (sht->virt_boundary_mask)
 		shost->virt_boundary_mask = sht->virt_boundary_mask;
 
+	if (sht->nr_reserved_cmds)
+		shost->nr_reserved_cmds = sht->nr_reserved_cmds;
+
 	device_initialize(&shost->shost_gendev);
 	dev_set_name(&shost->shost_gendev, "host%d", shost->host_no);
 	shost->shost_gendev.bus = &scsi_bus_type;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 5cb464972682..90af1ab6f4f5 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1916,7 +1916,9 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 	else
 		tag_set->ops = &scsi_mq_ops_no_commit;
 	tag_set->nr_hw_queues = shost->nr_hw_queues ? : 1;
-	tag_set->queue_depth = shost->can_queue;
+	tag_set->queue_depth =
+		shost->can_queue + shost->nr_reserved_cmds;
+	tag_set->reserved_tags = shost->nr_reserved_cmds;
 	tag_set->cmd_size = cmd_size;
 	tag_set->numa_node = NUMA_NO_NODE;
 	tag_set->flags = BLK_MQ_F_SHOULD_MERGE;
@@ -1941,6 +1943,9 @@ void scsi_mq_destroy_tags(struct Scsi_Host *shost)
  * @op_flags: request allocation flags
  *
  * Allocates a SCSI command for internal LLDD use.
+ * If 'nr_reserved_commands' is spectified by the host the
+ * command will be allocated from the reserved tag pool;
+ * otherwise the normal tag pool will be used.
  */
 struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
 	enum dma_data_direction data_direction, int op_flags)
@@ -1950,6 +1955,9 @@ struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
 	blk_mq_req_flags_t flags = 0;
 	unsigned int op = REQ_INTERNAL | op_flags;
 
+	if (sdev->host->nr_reserved_cmds)
+		flags = BLK_MQ_REQ_RESERVED;
+
 	op |= (data_direction == DMA_TO_DEVICE) ?
 		REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN;
 	rq = blk_mq_alloc_request(sdev->request_queue, op, flags);
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index ecc2d9dcfdf3..e826658bcecf 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -348,10 +348,19 @@ struct scsi_host_template {
 	/*
 	 * This determines if we will use a non-interrupt driven
 	 * or an interrupt driven scheme.  It is set to the maximum number
-	 * of simultaneous commands a single hw queue in HBA will accept.
+	 * of simultaneous commands a single hw queue in HBA will accept
+	 * excluding internal commands.
 	 */
 	int can_queue;
 
+	/*
+	 * This determines how many commands the HBA will set aside
+	 * for internal commands. This number will be added to
+	 * @can_queue to calcumate the maximum number of simultaneous
+	 * commands sent to the host.
+	 */
+	int nr_reserved_cmds;
+
 	/*
 	 * In many instances, especially where disconnect / reconnect are
 	 * supported, our host also has an ID on the SCSI bus.  If this is
@@ -599,6 +608,11 @@ struct Scsi_Host {
 	unsigned short max_cmd_len;
 
 	int this_id;
+
+	/*
+	 * Number of commands this host can handle at the same time.
+	 * This excludes reserved commands as specified by nr_reserved_cmds.
+	 */
 	int can_queue;
 	short cmd_per_lun;
 	short unsigned int sg_tablesize;
@@ -616,6 +630,12 @@ struct Scsi_Host {
 	 * the total queue depth is can_queue.
 	 */
 	unsigned nr_hw_queues;
+
+	/*
+	 * Number of reserved commands to allocate, if any.
+	 */
+	unsigned nr_reserved_cmds;
+
 	unsigned active_mode:2;
 	unsigned unchecked_isa_dma:1;
 
-- 
2.29.2


  parent reply index

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-22 13:23 [PATCHv7 00/31] scsi: enable reserved commands for LLDDs Hannes Reinecke
2021-02-22 13:23 ` [PATCH 01/31] block: add flag for internal commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 02/31] scsi: add scsi_{get,put}_internal_cmd() helper Hannes Reinecke
2021-02-24 12:12   ` John Garry
2021-02-22 13:23 ` [PATCH 03/31] fnic: use internal commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 04/31] fnic: use scsi_host_busy_iter() to traverse commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 05/31] fnic: check for started requests in fnic_wq_copy_cleanup_handler() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 06/31] scsi: use real inquiry data when initialising devices Hannes Reinecke
2021-02-22 13:23 ` [PATCH 07/31] scsi: Use dummy inquiry data for the host device Hannes Reinecke
2021-02-22 13:23 ` [PATCH 08/31] scsi: revamp host device handling Hannes Reinecke
2021-02-24 13:12   ` John Garry
2021-02-24 14:24     ` Hannes Reinecke
2021-02-24 14:31       ` John Garry
2021-02-24 14:35         ` Hannes Reinecke
2021-02-22 13:23 ` [PATCH 09/31] snic: use reserved commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 10/31] snic: use tagset iter for traversing commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 11/31] snic: check for started requests in snic_hba_reset_cmpl_handler() Hannes Reinecke
2021-02-22 13:23 ` Hannes Reinecke [this message]
2021-02-22 13:23 ` [PATCH 13/31] hpsa: move hpsa_hba_inquiry after scsi_add_host() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 14/31] hpsa: use reserved commands Hannes Reinecke
2021-03-11 22:03   ` michael.christie
2021-05-03  9:36     ` Hannes Reinecke
2021-02-22 13:23 ` [PATCH 15/31] hpsa: use scsi_host_busy_iter() to traverse outstanding commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 16/31] hpsa: drop refcount field from CommandList Hannes Reinecke
2021-02-22 13:23 ` [PATCH 17/31] aacraid: move scsi_add_host() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 18/31] aacraid: store target id in host_scribble Hannes Reinecke
2021-02-22 13:23 ` [PATCH 19/31] aacraid: use scsi_get_internal_cmd() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 20/31] aacraid: use scsi_host_busy_iter() to traverse outstanding commands Hannes Reinecke
2021-02-22 13:23 ` [PATCH 21/31] mv_sas: kill mvsas_debug_issue_ssp_tmf() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 22/31] pm8001: kill pm8001_issue_ssp_tmf() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 23/31] pm8001: kill 'dev' argument from pm8001_exec_internal_task_abort() Hannes Reinecke
2021-02-22 13:23 ` [PATCH 24/31] pm8001: use libsas-provided domain devices for SATA Hannes Reinecke
2021-02-22 13:23 ` [PATCH 25/31] libsas: add SCSI target pointer to struct domain_device Hannes Reinecke
2021-02-22 13:24 ` [PATCH 26/31] scsi: libsas,hisi_sas,mvsas,pm8001: Allocate Scsi_cmd for slow task Hannes Reinecke
2021-03-09 11:22   ` luojiaxing
2021-03-09 14:05     ` John Garry
2021-03-11  8:51       ` luojiaxing
2021-02-22 13:24 ` [PATCH 27/31] libsas: add tag to struct sas_task Hannes Reinecke
2021-02-22 13:24 ` [PATCH 28/31] scsi: hisi_sas: Use libsas slow task SCSI command Hannes Reinecke
2021-02-22 13:24 ` [PATCH 29/31] hisi_sas: use task tag to reference the slot Hannes Reinecke
2021-03-10  1:54   ` luojiaxing
2021-02-22 13:24 ` [PATCH 30/31] mv_sas: use reserved tags and drop private tag allocation Hannes Reinecke
2021-02-22 13:24 ` [PATCH 31/31] pm8001: use block-layer tags for ccb allocation Hannes Reinecke
2021-02-23 12:31   ` John Garry
2021-02-23 10:16 ` [PATCHv7 00/31] scsi: enable reserved commands for LLDDs John Garry
2021-02-23 17:50   ` John Garry
2021-02-24  6:54     ` Hannes Reinecke
2021-02-24  8:55       ` John Garry
2021-03-06 15:11 ` Don.Brace
2021-03-16 17:57   ` Don.Brace
2021-03-29 21:47     ` Don.Brace
2021-03-11 23:53 ` michael.christie
2021-03-12 16:08   ` Hannes Reinecke
2021-03-17 17:09     ` John Garry

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