[SCSI] iscsi: lower queue depth

From Wang Zhenyu:

High queue depth was a problem for some targets so make queue_depth adjustable

From Mike Christie

Make default queue_depth a little lower

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Alex Aizman <itn780@yahoo.com>
Signed-off-by: Dmitry Yusupov <dmitry_yus@yahoo.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

2 files changed, 17 insertions, 6 deletions

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 83e2f8c8e496..5b14c404069f 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -2402,6 +2402,15 @@ fault:
 }
 
 static int
+iscsi_change_queue_depth(struct scsi_device *sdev, int depth)
+{
+        if (depth > ISCSI_MAX_CMD_PER_LUN)
+                depth = ISCSI_MAX_CMD_PER_LUN;
+        scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
+        return sdev->queue_depth;
+}
+
+static int
 iscsi_pool_init(struct iscsi_queue *q, int max, void ***items, int item_size)
 {
         int i;
@@ -3260,13 +3269,14 @@ iscsi_r2tpool_free(struct iscsi_session *session)
 static struct scsi_host_template iscsi_sht = {
         .name                   = "iSCSI Initiator over TCP/IP, v."
                                   ISCSI_VERSION_STR,
-        .queuecommand           = iscsi_queuecommand,
+        .queuecommand           = iscsi_queuecommand,
+        .change_queue_depth     = iscsi_change_queue_depth,
         .can_queue              = ISCSI_XMIT_CMDS_MAX - 1,
         .sg_tablesize           = ISCSI_SG_TABLESIZE,
-        .cmd_per_lun            = ISCSI_CMD_PER_LUN,
-        .eh_abort_handler       = iscsi_eh_abort,
-        .eh_host_reset_handler  = iscsi_eh_host_reset,
-        .use_clustering         = DISABLE_CLUSTERING,
+        .cmd_per_lun            = ISCSI_DEF_CMD_PER_LUN,
+        .eh_abort_handler       = iscsi_eh_abort,
+        .eh_host_reset_handler  = iscsi_eh_host_reset,
+        .use_clustering         = DISABLE_CLUSTERING,
         .proc_name              = "iscsi_tcp",
         .this_id                = -1,
 };
diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index d23ae68fae0d..855f2dfd18af 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -71,7 +71,8 @@
 #define ISCSI_MGMT_CMDS_MAX             32      /* must be power of 2 */
 #define ISCSI_MGMT_ITT_OFFSET           0xa00
 #define ISCSI_SG_TABLESIZE              SG_ALL
-#define ISCSI_CMD_PER_LUN               128
+#define ISCSI_DEF_CMD_PER_LUN           32
+#define ISCSI_MAX_CMD_PER_LUN           128
 #define ISCSI_TCP_MAX_CMD_LEN           16
 
 #define ITT_MASK                        (0xfff)