IB/srp: Make login failures easier to debug

If login fails because memory region allocation failed it can be
hard to figure out what happened. Make it easier to figure out
why login failed by logging a message if ib_alloc_mr() fails.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/srp/ib_srp.c

@@ -389,6 +389,9 @@ static struct srp_fr_pool *srp_create_fr_pool(struct ib_device *device,
 				 max_page_list_len);
 		if (IS_ERR(mr)) {
 			ret = PTR_ERR(mr);
+			if (ret == -ENOMEM)
+				pr_info("%s: ib_alloc_mr() failed. Try to reduce max_cmd_per_lun, max_sect or ch_count\n",
+					dev_name(&device->dev));
 			goto destroy_pool;
 		}
 		d->mr = mr;