[ofa-general] [PATCH 2/3] IB/srp: allow user to control host queue length

[David Dillow]

It can be useful for tuning and balancing for the user to restrict the
maximum number of commands that can be queued for a particular SRP
target, similar to the tuning parameter "max_cmds_per_lun" allows per
device on this target.

This patch adds "queue_len" to allow that flexibility.

Signed-off-by: David Dillow <dillowda at ornl.gov>
---
 ib_srp.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 17ad144..9cb77e6 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1612,6 +1612,7 @@ enum {
 	SRP_OPT_MAX_CMD_PER_LUN	= 1 << 6,
 	SRP_OPT_IO_CLASS	= 1 << 7,
 	SRP_OPT_INITIATOR_EXT	= 1 << 8,
+	SRP_OPT_QUEUE_LEN	= 1 << 9,
 	SRP_OPT_ALL		= (SRP_OPT_ID_EXT	|
 				   SRP_OPT_IOC_GUID	|
 				   SRP_OPT_DGID		|
@@ -1629,6 +1630,7 @@ static match_table_t srp_opt_tokens = {
 	{ SRP_OPT_MAX_CMD_PER_LUN,	"max_cmd_per_lun=%d" 	},
 	{ SRP_OPT_IO_CLASS,		"io_class=%x"		},
 	{ SRP_OPT_INITIATOR_EXT,	"initiator_ext=%s"	},
+	{ SRP_OPT_QUEUE_LEN,		"queue_len=%d"		},
 	{ SRP_OPT_ERR,			NULL 			}
 };
 
@@ -1756,6 +1758,14 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 			kfree(p);
 			break;
 
+		case SRP_OPT_QUEUE_LEN:
+			if (match_int(args, &token)) {
+				printk(KERN_WARNING PFX "bad queue_len parameter '%s'\n", p);
+				goto out;
+			}
+			target->scsi_host->can_queue = min(token, SRP_SQ_SIZE);
+			break;
+
 		default:
 			printk(KERN_WARNING PFX "unknown parameter or missing value "
 			       "'%s' in target creation request\n", p);