[SCSI] ibmvscsi: allow for dynamic adjustment of server request_limit

The request limit calculations used previously on the client failed to
mirror the state of the server.  Additionally, when a value < 3 was provided
there could be problems setting can_queue and handling abort and reset
commands.

Signed-off-by: "Robert Jennings" <rcj@linux.vnet.ibm.com>
Signed-off-by: Santiago Leon <santil@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

2 files changed, 40 insertions, 20 deletions

diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index fbc1d5c3b0a7..383f5948ba06 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -85,7 +85,7 @@
 static int max_id = 64;
 static int max_channel = 3;
 static int init_timeout = 5;
-static int max_requests = 50;
+static int max_requests = IBMVSCSI_MAX_REQUESTS_DEFAULT;
 
 #define IBMVSCSI_VERSION "1.5.8"
 
@@ -538,7 +538,8 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
         int request_status;
         int rc;
 
-        /* If we have exhausted our request limit, just fail this request.
+        /* If we have exhausted our request limit, just fail this request,
+         * unless it is for a reset or abort.
          * Note that there are rare cases involving driver generated requests 
          * (such as task management requests) that the mid layer may think we
          * can handle more requests (can_queue) when we actually can't
@@ -551,9 +552,30 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
                  */
                 if (request_status < -1)
                         goto send_error;
-                /* Otherwise, if we have run out of requests */
-                else if (request_status < 0)
-                        goto send_busy;
+                /* Otherwise, we may have run out of requests. */
+                /* Abort and reset calls should make it through.
+                 * Nothing except abort and reset should use the last two
+                 * slots unless we had two or less to begin with.
+                 */
+                else if (request_status < 2 &&
+                         evt_struct->iu.srp.cmd.opcode != SRP_TSK_MGMT) {
+                        /* In the case that we have less than two requests
+                         * available, check the server limit as a combination
+                         * of the request limit and the number of requests
+                         * in-flight (the size of the send list).  If the
+                         * server limit is greater than 2, return busy so
+                         * that the last two are reserved for reset and abort.
+                         */
+                        int server_limit = request_status;
+                        struct srp_event_struct *tmp_evt;
+
+                        list_for_each_entry(tmp_evt, &hostdata->sent, list) {
+                                server_limit++;
+                        }
+
+                        if (server_limit > 2)
+                                goto send_busy;
+                }
         }
 
         /* Copy the IU into the transfer area */
@@ -572,6 +594,7 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
 
                 printk(KERN_ERR "ibmvscsi: send error %d\n",
                        rc);
+                atomic_inc(&hostdata->request_limit);
                 goto send_error;
         }
 
@@ -581,7 +604,8 @@ static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
         unmap_cmd_data(&evt_struct->iu.srp.cmd, evt_struct, hostdata->dev);
 
         free_event_struct(&hostdata->pool, evt_struct);
-        return SCSI_MLQUEUE_HOST_BUSY;
+        atomic_inc(&hostdata->request_limit);
+        return SCSI_MLQUEUE_HOST_BUSY;
 
  send_error:
         unmap_cmd_data(&evt_struct->iu.srp.cmd, evt_struct, hostdata->dev);
@@ -831,23 +855,16 @@ static void login_rsp(struct srp_event_struct *evt_struct)
 
         printk(KERN_INFO "ibmvscsi: SRP_LOGIN succeeded\n");
 
-        if (evt_struct->xfer_iu->srp.login_rsp.req_lim_delta >
-            (max_requests - 2))
-                evt_struct->xfer_iu->srp.login_rsp.req_lim_delta =
-                    max_requests - 2;
+        if (evt_struct->xfer_iu->srp.login_rsp.req_lim_delta < 0)
+                printk(KERN_ERR "ibmvscsi: Invalid request_limit.\n");
 
-        /* Now we know what the real request-limit is */
+        /* Now we know what the real request-limit is.
+         * This value is set rather than added to request_limit because
+         * request_limit could have been set to -1 by this client.
+         */
         atomic_set(&hostdata->request_limit,
                    evt_struct->xfer_iu->srp.login_rsp.req_lim_delta);
 
-        hostdata->host->can_queue =
-            evt_struct->xfer_iu->srp.login_rsp.req_lim_delta - 2;
-
-        if (hostdata->host->can_queue < 1) {
-                printk(KERN_ERR "ibmvscsi: Invalid request_limit_delta\n");
-                return;
-        }
-
         /* If we had any pending I/Os, kick them */
         scsi_unblock_requests(hostdata->host);
 
@@ -1483,7 +1500,7 @@ static struct scsi_host_template driver_template = {
         .eh_abort_handler = ibmvscsi_eh_abort_handler,
         .eh_device_reset_handler = ibmvscsi_eh_device_reset_handler,
         .cmd_per_lun = 16,
-        .can_queue = 1,         /* Updated after SRP_LOGIN */
+        .can_queue = IBMVSCSI_MAX_REQUESTS_DEFAULT,
         .this_id = -1,
         .sg_tablesize = SG_ALL,
         .use_clustering = ENABLE_CLUSTERING,
@@ -1503,6 +1520,7 @@ static int ibmvscsi_probe(struct vio_dev *vdev, const struct vio_device_id *id)
 
         vdev->dev.driver_data = NULL;
 
+        driver_template.can_queue = max_requests;
         host = scsi_host_alloc(&driver_template, sizeof(*hostdata));
         if (!host) {
                 printk(KERN_ERR "ibmvscsi: couldn't allocate host data\n");
diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.h b/drivers/scsi/ibmvscsi/ibmvscsi.h
index 5c6d93582929..77cc1d40f5bb 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.h
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.h
@@ -44,6 +44,8 @@ struct Scsi_Host;
  */
 #define MAX_INDIRECT_BUFS 10
 
+#define IBMVSCSI_MAX_REQUESTS_DEFAULT 100
+
 /* ------------------------------------------------------------
  * Data Structures
  */