[PATCH 13/14] IB/srp: Make transport layer retry count configurable

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

From: Vu Pham <vuhuong-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>

Allow the InfiniBand RC retry count to be configured by the user
as an option in the target login string. The transport layer
timeout in nanoseconds is computed as follows from the retry count:

rc_timeout = rc_retry_count * 4 * 4096 * (1 << qp->timeout)

The default value for tl_retry_count is changed from 7 into 2.
Hence with a qp->timedout value of 19 this patch reduces the
default transport layer timeout from about 60s to about 17s. The
purpose of this patch is to reduce the time needed for SCSI error
handling significantly and at the same time to avoid activating
the SCSI error handler on an IB path with a regular BER or due to
brief IB network congestion.

[bvanassche: Rewrote patch description]
Signed-off-by: Vu Pham <vu-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>
Cc: Roland Dreier <roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org>
Cc: David Dillow <dillowda-1Heg1YXhbW8@public.gmane.org>
Cc: Vu Pham <vu-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Cc: Sebastian Riemer <sebastian.riemer-EIkl63zCoXaH+58JC4qpiA@public.gmane.org>
---
 drivers/infiniband/ulp/srp/ib_srp.c |   24 +++++++++++++++++++++++-
 drivers/infiniband/ulp/srp/ib_srp.h |    1 +
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 49d8464..44ee93a 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -453,7 +453,7 @@ static int srp_send_req(struct srp_target_port *target)
 	req->param.responder_resources	      = 4;
 	req->param.remote_cm_response_timeout = 20;
 	req->param.local_cm_response_timeout  = 20;
-	req->param.retry_count 		      = 7;
+	req->param.retry_count                = target->tl_retry_count;
 	req->param.rnr_retry_count 	      = 7;
 	req->param.max_cm_retries 	      = 15;
 
@@ -2016,6 +2016,14 @@ static ssize_t show_comp_vector(struct device *dev,
 	return sprintf(buf, "%d\n", target->comp_vector);
 }
 
+static ssize_t show_tl_retry_count(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct srp_target_port *target = host_to_target(class_to_shost(dev));
+
+	return sprintf(buf, "%d\n", target->tl_retry_count);
+}
+
 static ssize_t show_cmd_sg_entries(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
@@ -2043,6 +2051,7 @@ static DEVICE_ATTR(zero_req_lim,    S_IRUGO, show_zero_req_lim,	   NULL);
 static DEVICE_ATTR(local_ib_port,   S_IRUGO, show_local_ib_port,   NULL);
 static DEVICE_ATTR(local_ib_device, S_IRUGO, show_local_ib_device, NULL);
 static DEVICE_ATTR(comp_vector,     S_IRUGO, show_comp_vector,     NULL);
+static DEVICE_ATTR(tl_retry_count,  S_IRUGO, show_tl_retry_count,  NULL);
 static DEVICE_ATTR(cmd_sg_entries,  S_IRUGO, show_cmd_sg_entries,  NULL);
 static DEVICE_ATTR(allow_ext_sg,    S_IRUGO, show_allow_ext_sg,    NULL);
 
@@ -2058,6 +2067,7 @@ static struct device_attribute *srp_host_attrs[] = {
 	&dev_attr_local_ib_port,
 	&dev_attr_local_ib_device,
 	&dev_attr_comp_vector,
+	&dev_attr_tl_retry_count,
 	&dev_attr_cmd_sg_entries,
 	&dev_attr_allow_ext_sg,
 	NULL
@@ -2153,6 +2163,7 @@ enum {
 	SRP_OPT_ALLOW_EXT_SG	= 1 << 10,
 	SRP_OPT_SG_TABLESIZE	= 1 << 11,
 	SRP_OPT_COMP_VECTOR	= 1 << 12,
+	SRP_OPT_TL_RETRY_COUNT	= 1 << 13,
 	SRP_OPT_ALL		= (SRP_OPT_ID_EXT	|
 				   SRP_OPT_IOC_GUID	|
 				   SRP_OPT_DGID		|
@@ -2174,6 +2185,7 @@ static const match_table_t srp_opt_tokens = {
 	{ SRP_OPT_ALLOW_EXT_SG,		"allow_ext_sg=%u"	},
 	{ SRP_OPT_SG_TABLESIZE,		"sg_tablesize=%u"	},
 	{ SRP_OPT_COMP_VECTOR,		"comp_vector=%u"	},
+	{ SRP_OPT_TL_RETRY_COUNT,	"tl_retry_count=%u"	},
 	{ SRP_OPT_ERR,			NULL 			}
 };
 
@@ -2337,6 +2349,15 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 			target->comp_vector = token;
 			break;
 
+		case SRP_OPT_TL_RETRY_COUNT:
+			if (match_int(args, &token) || token < 2 || token > 7) {
+				pr_warn("bad tl_retry_count parameter '%s' (must be a number between 2 and 7)\n",
+					p);
+				goto out;
+			}
+			target->tl_retry_count = token;
+			break;
+
 		default:
 			pr_warn("unknown parameter or missing value '%s' in target creation request\n",
 				p);
@@ -2391,6 +2412,7 @@ static ssize_t srp_create_target(struct device *dev,
 	target->cmd_sg_cnt	= cmd_sg_entries;
 	target->sg_tablesize	= indirect_sg_entries ? : cmd_sg_entries;
 	target->allow_ext_sg	= allow_ext_sg;
+	target->tl_retry_count	= 2;
 
 	ret = srp_parse_options(buf, target);
 	if (ret)
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index cbc0b14..446b045 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -157,6 +157,7 @@ struct srp_target_port {
 	unsigned int		scsi_id;
 	unsigned int		sg_tablesize;
 	int			comp_vector;
+	int			tl_retry_count;
 
 	struct ib_sa_path_rec	path;
 	__be16			orig_dgid[8];
-- 
1.7.10.4

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