[SCSI] hpsa: allow user to disable accelerated i/o path

Allow SSD Smart Path for a controller to be disabled by
the user, regardless of settings in controller firmware
or array configuration.

To disable:     echo 0 > /sys/class/scsi_host/host<id>/acciopath_status
To re-enable:   echo 1 > /sys/class/scsi_host/host<id>/acciopath_status
To check state: cat /sys/class/scsi_host/host<id>/acciopath_status

Signed-off-by: Scott Teel <scott.teel@hp.com>
Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

3 files changed, 61 insertions, 1 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-scsi_host b/Documentation/ABI/testing/sysfs-class-scsi_host
index 29a4f892e433..0eb255e7db12 100644
--- a/Documentation/ABI/testing/sysfs-class-scsi_host
+++ b/Documentation/ABI/testing/sysfs-class-scsi_host
@@ -11,3 +11,19 @@ Description:
                 guaranteed.  The 'isci_id' attribute unambiguously identifies
                 the controller index: '0' for the first controller,
                 '1' for the second.
+
+What:           /sys/class/scsi_host/hostX/acciopath_status
+Date:           November 2013
+Contact:        Stephen M. Cameron <scameron@beardog.cce.hp.com>
+Description:    This file contains the current status of the "SSD Smart Path"
+                feature of HP Smart Array RAID controllers using the hpsa
+                driver.  SSD Smart Path, when enabled permits the driver to
+                send i/o requests directly to physical devices that are part
+                of a logical drive, bypassing the controllers firmware RAID
+                stack for a performance advantage when possible.  A value of
+                '1' indicates the feature is enabled, and the controller may
+                use the direct i/o path to physical devices.  A value of zero
+                means the feature is disabled and the controller may not use
+                the direct i/o path to physical devices.  This setting is
+                controller wide, affecting all configured logical drives on the
+                controller.  This file is readable and writable.
diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index 7cd28714d8dd..a599a7b51a92 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -287,6 +287,30 @@ static int check_for_busy(struct ctlr_info *h, struct CommandList *c)
         return 1;
 }
 
+static ssize_t host_store_hp_ssd_smart_path_status(struct device *dev,
+                                         struct device_attribute *attr,
+                                         const char *buf, size_t count)
+{
+        int status, len;
+        struct ctlr_info *h;
+        struct Scsi_Host *shost = class_to_shost(dev);
+        char tmpbuf[10];
+
+        if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
+                return -EACCES;
+        len = count > sizeof(tmpbuf) - 1 ? sizeof(tmpbuf) - 1 : count;
+        strncpy(tmpbuf, buf, len);
+        tmpbuf[len] = '\0';
+        if (sscanf(tmpbuf, "%d", &status) != 1)
+                return -EINVAL;
+        h = shost_to_hba(shost);
+        h->acciopath_status = !!status;
+        dev_warn(&h->pdev->dev,
+                "hpsa: HP SSD Smart Path %s via sysfs update.\n",
+                h->acciopath_status ? "enabled" : "disabled");
+        return count;
+}
+
 static ssize_t host_store_rescan(struct device *dev,
                                  struct device_attribute *attr,
                                  const char *buf, size_t count)
@@ -334,6 +358,17 @@ static ssize_t host_show_transport_mode(struct device *dev,
                         "performant" : "simple");
 }
 
+static ssize_t host_show_hp_ssd_smart_path_status(struct device *dev,
+        struct device_attribute *attr, char *buf)
+{
+        struct ctlr_info *h;
+        struct Scsi_Host *shost = class_to_shost(dev);
+
+        h = shost_to_hba(shost);
+        return snprintf(buf, 30, "HP SSD Smart Path %s\n",
+                (h->acciopath_status == 1) ?  "enabled" : "disabled");
+}
+
 /* List of controllers which cannot be hard reset on kexec with reset_devices */
 static u32 unresettable_controller[] = {
         0x324a103C, /* Smart Array P712m */
@@ -546,6 +581,9 @@ static DEVICE_ATTR(unique_id, S_IRUGO, unique_id_show, NULL);
 static DEVICE_ATTR(rescan, S_IWUSR, NULL, host_store_rescan);
 static DEVICE_ATTR(hp_ssd_smart_path_enabled, S_IRUGO,
                         host_show_hp_ssd_smart_path_enabled, NULL);
+static DEVICE_ATTR(hp_ssd_smart_path_status, S_IWUSR|S_IRUGO|S_IROTH,
+                host_show_hp_ssd_smart_path_status,
+                host_store_hp_ssd_smart_path_status);
 static DEVICE_ATTR(firmware_revision, S_IRUGO,
         host_show_firmware_revision, NULL);
 static DEVICE_ATTR(commands_outstanding, S_IRUGO,
@@ -569,6 +607,7 @@ static struct device_attribute *hpsa_shost_attrs[] = {
         &dev_attr_commands_outstanding,
         &dev_attr_transport_mode,
         &dev_attr_resettable,
+        &dev_attr_hp_ssd_smart_path_status,
         NULL,
 };
 
@@ -3341,7 +3380,8 @@ static int hpsa_scsi_queue_command_lck(struct scsi_cmnd *cmd,
          * Retries always go down the normal I/O path.
          */
         if (likely(cmd->retries == 0 &&
-                cmd->request->cmd_type == REQ_TYPE_FS)) {
+                cmd->request->cmd_type == REQ_TYPE_FS &&
+                h->acciopath_status)) {
                 if (dev->offload_enabled) {
                         rc = hpsa_scsi_ioaccel_raid_map(h, c);
                         if (rc == 0)
@@ -6326,6 +6366,9 @@ reinit_after_soft_reset:
                 goto reinit_after_soft_reset;
         }
 
+        /* Enable Accelerated IO path at driver layer */
+        h->acciopath_status = 1;
+
         /* Turn the interrupts on so we can service requests */
         h->access.set_intr_mask(h, HPSA_INTR_ON);
 
diff --git a/drivers/scsi/hpsa.h b/drivers/scsi/hpsa.h
index 45bb1ea6835e..1d3340dbe310 100644
--- a/drivers/scsi/hpsa.h
+++ b/drivers/scsi/hpsa.h
@@ -181,6 +181,7 @@ struct ctlr_info {
 #define HPSATMF_LOG_QRY_TSET    (1 << 24)
 #define HPSATMF_LOG_QRY_ASYNC   (1 << 25)
         u32 events;
+        int     acciopath_status;
 };
 #define HPSA_ABORT_MSG 0
 #define HPSA_DEVICE_RESET_MSG 1