[SCSI] libsas: dynamic queue depth

The queue-depth for libsas-attached devices initializes to 32 and can
only be increased manually via sysfs to a max of 64, while mpt2sas
attached devices initialize to 254 and dynamically float via the
midlayer ->change_queue_depth interface.

No performance regression was observed with this change on the isci
driver.

Tested-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 18 insertions, 21 deletions

diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index 8f3c4cc1bfe4..ebd1417339e9 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -761,8 +761,7 @@ int sas_target_alloc(struct scsi_target *starget)
         return 0;
 }
 
-#define SAS_DEF_QD 32
-#define SAS_MAX_QD 64
+#define SAS_DEF_QD 256
 
 int sas_slave_configure(struct scsi_device *scsi_dev)
 {
@@ -805,31 +804,29 @@ void sas_slave_destroy(struct scsi_device *scsi_dev)
                 dev->sata_dev.ap->link.device[0].class = ATA_DEV_NONE;
 }
 
-int sas_change_queue_depth(struct scsi_device *scsi_dev, int new_depth,
-                           int reason)
+int sas_change_queue_depth(struct scsi_device *sdev, int depth, int reason)
 {
-        struct domain_device *dev = sdev_to_domain_dev(scsi_dev);
-        int res = min(new_depth, SAS_MAX_QD);
+        struct domain_device *dev = sdev_to_domain_dev(sdev);
 
         if (dev_is_sata(dev))
-                return __ata_change_queue_depth(dev->sata_dev.ap, scsi_dev,
-                                                new_depth, reason);
-
-        if (reason != SCSI_QDEPTH_DEFAULT)
+                return __ata_change_queue_depth(dev->sata_dev.ap, sdev, depth,
+                                                reason);
+
+        switch (reason) {
+        case SCSI_QDEPTH_DEFAULT:
+        case SCSI_QDEPTH_RAMP_UP:
+                if (!sdev->tagged_supported)
+                        depth = 1;
+                scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
+                break;
+        case SCSI_QDEPTH_QFULL:
+                scsi_track_queue_full(sdev, depth);
+                break;
+        default:
                 return -EOPNOTSUPP;
-
-        if (scsi_dev->tagged_supported)
-                scsi_adjust_queue_depth(scsi_dev, scsi_get_tag_type(scsi_dev),
-                                        res);
-        else {
-                sas_printk("device %llx LUN %x queue depth changed to 1\n",
-                           SAS_ADDR(dev->sas_addr),
-                           scsi_dev->lun);
-                scsi_adjust_queue_depth(scsi_dev, 0, 1);
-                res = 1;
         }
 
-        return res;
+        return depth;
 }
 
 int sas_change_queue_type(struct scsi_device *scsi_dev, int qt)