[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>

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);
 

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] &&

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));
+	}
+}
+

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);

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: