Merge patch series "scsi: target: Allow userspace to config cmd submission"

Mike Christie <michael.christie@oracle.com> says:

The following patches were made over Linus's tree but apply over
Martin's branches. They allow userspace to configure how fabric
drivers submit cmds to backend drivers.

Right now loop and vhost use a worker thread, and the other drivers
submit from the contexts they receive/process the cmd from. For
multiple LUN cases where the target can queue more cmds than the
backend can handle then deferring to a worker thread is safest because
the backend driver can block when doing things like waiting for a free
request/tag. Deferring also helps when the target has to handle
transport level requests from the recv context.

For cases where the backend devices can queue everything the target
sends, then there is no need to defer to a workqueue and you can see a
perf boost of up to 26% for small IO workloads. For a nvme device and
vhost-scsi I can see with 4K IOs:

fio jobs        1       2       4       8       10
--------------------------------------------------
workqueue
submit        94K     190K    394K    770K    890K

direct
submit       128K     252K    488K    950K    -

Link: https://lore.kernel.org/r/1b1f7a5c-0988-45f9-b103-dfed2c0405b1@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

4 files changed, 6 insertions, 9 deletions

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index b516c2893420..1d25e64b068a 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -1234,12 +1234,6 @@ attach_cmd:
 	spin_lock_bh(&conn->cmd_lock);
 	list_add_tail(&cmd->i_conn_node, &conn->conn_cmd_list);
 	spin_unlock_bh(&conn->cmd_lock);
-	/*
-	 * Check if we need to delay processing because of ALUA
-	 * Active/NonOptimized primary access state..
-	 */
-	core_alua_check_nonop_delay(&cmd->se_cmd);
-
 	return 0;
 }
 EXPORT_SYMBOL(iscsit_setup_scsi_cmd);
diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configfs.c
index 1cff6052e820..88db94f382bb 100644
--- a/drivers/target/iscsi/iscsi_target_configfs.c
+++ b/drivers/target/iscsi/iscsi_target_configfs.c
@@ -1589,5 +1589,8 @@ const struct target_core_fabric_ops iscsi_ops = {
 	.tfc_tpg_nacl_auth_attrs	= lio_target_nacl_auth_attrs,
 	.tfc_tpg_nacl_param_attrs	= lio_target_nacl_param_attrs,
 
-	.write_pending_must_be_called	= true,
+	.write_pending_must_be_called	= 1,
+
+	.default_submit_type		= TARGET_DIRECT_SUBMIT,
+	.direct_submit_supp		= 1,
 };
diff --git a/drivers/target/iscsi/iscsi_target_erl1.c b/drivers/target/iscsi/iscsi_target_erl1.c
index f460a66c0e7c..679720021183 100644
--- a/drivers/target/iscsi/iscsi_target_erl1.c
+++ b/drivers/target/iscsi/iscsi_target_erl1.c
@@ -948,7 +948,7 @@ int iscsit_execute_cmd(struct iscsit_cmd *cmd, int ooo)
 
 			iscsit_set_unsolicited_dataout(cmd);
 		}
-		return transport_handle_cdb_direct(&cmd->se_cmd);
+		return target_submit(&cmd->se_cmd);
 
 	case ISCSI_OP_NOOP_OUT:
 	case ISCSI_OP_TEXT:
diff --git a/drivers/target/iscsi/iscsi_target_tmr.c b/drivers/target/iscsi/iscsi_target_tmr.c
index afc801f255f5..9c4aa01b6351 100644
--- a/drivers/target/iscsi/iscsi_target_tmr.c
+++ b/drivers/target/iscsi/iscsi_target_tmr.c
@@ -318,7 +318,7 @@ static int iscsit_task_reassign_complete_read(
 		pr_debug("READ ITT: 0x%08x: t_state: %d never sent to"
 			" transport\n", cmd->init_task_tag,
 			cmd->se_cmd.t_state);
-		transport_handle_cdb_direct(se_cmd);
+		target_submit(se_cmd);
 		return 0;
 	}