[PATCH] Snoop SET FEATURES - WRITE CACHE ENABLE/DISABLE command(v5)

This patch makes libata snoop 'SET FEATURES - WRITE CACHE
ENABLE/DISABLE' command, executing requisite revalidation processes
to update cached data.

Signed-off-by: Forrest Zhao <forrest.zhao@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

5 files changed, 44 insertions, 0 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 51b3a0ddb238..ddaad1a4f1f1 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -5194,6 +5194,7 @@ static void ata_host_init(struct ata_port *ap, struct Scsi_Host *host,
 
         INIT_WORK(&ap->port_task, NULL, NULL);
         INIT_WORK(&ap->hotplug_task, ata_scsi_hotplug, ap);
+        INIT_WORK(&ap->scsi_rescan_task, ata_scsi_dev_rescan, ap);
         INIT_LIST_HEAD(&ap->eh_done_q);
         init_waitqueue_head(&ap->eh_wait_q);
 
diff --git a/drivers/scsi/libata-eh.c b/drivers/scsi/libata-eh.c
index 6285257a890d..f82799e22588 100644
--- a/drivers/scsi/libata-eh.c
+++ b/drivers/scsi/libata-eh.c
@@ -1554,6 +1554,9 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
                         if (rc)
                                 break;
 
+                        /* schedule the scsi_rescan_device() here */
+                        queue_work(ata_aux_wq, &(ap->scsi_rescan_task));
+
                         ehc->i.action &= ~ATA_EH_REVALIDATE;
                 } else if (dev->class == ATA_DEV_UNKNOWN &&
                            ehc->tries[dev->devno] &&
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 5f90d8e33546..45a49be65042 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -1306,6 +1306,17 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
         u8 *cdb = cmd->cmnd;
         int need_sense = (qc->err_mask != 0);
 
+        /* We snoop the SET_FEATURES - Write Cache ON/OFF command, and
+         * schedule EH_REVALIDATE operation to update the IDENTIFY DEVICE
+         * cache
+         */
+        if (!need_sense && (qc->tf.command == ATA_CMD_SET_FEATURES) &&
+            ((qc->tf.feature == SETFEATURES_WC_ON) ||
+             (qc->tf.feature == SETFEATURES_WC_OFF))) {
+                qc->ap->eh_info.action |= ATA_EH_REVALIDATE;
+                ata_port_schedule_eh(qc->ap);
+        }
+
         /* For ATA pass thru (SAT) commands, generate a sense block if
          * user mandated it or if there's an error.  Note that if we
          * generate because the user forced us to, a check condition
@@ -2992,3 +3003,28 @@ static int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel,
 
         return rc;
 }
+
+/**
+ *      ata_scsi_dev_rescan - initiate scsi_rescan_device()
+ *      @data: Pointer to ATA port to perform scsi_rescan_device()
+ *
+ *      After ATA pass thru (SAT) commands are executed successfully,
+ *      libata need to propagate the changes to SCSI layer.
+ *
+ *      LOCKING:
+ *      Kernel thread context (may sleep).
+ */
+void ata_scsi_dev_rescan(void *data)
+{
+        struct ata_port *ap = data;
+        struct ata_device *dev;
+        unsigned int i;
+
+        for (i = 0; i < ATA_MAX_DEVICES; i++) {
+                dev = &ap->device[i];
+
+                if (ata_dev_enabled(dev))
+                        scsi_rescan_device(&(dev->sdev->sdev_gendev));
+        }
+}
+
diff --git a/drivers/scsi/libata.h b/drivers/scsi/libata.h
index 1dd496f1f7ac..bdd488897096 100644
--- a/drivers/scsi/libata.h
+++ b/drivers/scsi/libata.h
@@ -104,6 +104,7 @@ extern void ata_scsi_rbuf_fill(struct ata_scsi_args *args,
                         unsigned int (*actor) (struct ata_scsi_args *args,
                                            u8 *rbuf, unsigned int buflen));
 extern void ata_schedule_scsi_eh(struct Scsi_Host *shost);
+extern void ata_scsi_dev_rescan(void *data);
 
 /* libata-eh.c */
 extern enum scsi_eh_timer_return ata_scsi_timed_out(struct scsi_cmnd *cmd);
diff --git a/include/linux/ata.h b/include/linux/ata.h
index c494e1c0531e..3671af869696 100644
--- a/include/linux/ata.h
+++ b/include/linux/ata.h
@@ -181,6 +181,9 @@ enum {
         XFER_PIO_0              = 0x08,
         XFER_PIO_SLOW           = 0x00,
 
+        SETFEATURES_WC_ON       = 0x02, /* Enable write cache */
+        SETFEATURES_WC_OFF      = 0x82, /* Disable write cache */
+
         /* ATAPI stuff */
         ATAPI_PKT_DMA           = (1 << 0),
         ATAPI_DMADIR            = (1 << 2),     /* ATAPI data dir: