IB/srp: Make transport layer retry count configurable

Allow the InfiniBand RC retry count to be configured by the user as an
option in the target login string.  Reducing this retry count allows to
reduce the path failover time.

Signed-off-by: Vu Pham <vu@mellanox.com>

[ bvanassche: Rewrote patch description / changed default retry count ]

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <roland@purestorage.com>

2 files changed, 24 insertions, 1 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index f93baf8254c4..11ebf3e7646a 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -390,7 +390,7 @@ 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;
 
@@ -1907,6 +1907,14 @@ 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)
 {
@@ -1934,6 +1942,7 @@ 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);
 
@@ -1949,6 +1958,7 @@ 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
@@ -2073,6 +2083,7 @@ 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         |
@@ -2094,6 +2105,7 @@ 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                    }
 };
 
@@ -2257,6 +2269,15 @@ 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);
@@ -2311,6 +2332,7 @@ 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  = 7;
 
         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 e641088c14dc..84d821b24ec7 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];