[PATCH 1/1] scsi: retrieve cache mode using ATA_16 if normal routine fails

[Amit Sahrawat <amit.sahrawat83@gmail.com>]

It has been observed that a number of USB HDD's do not respond correctly
to SCSI mode sense command(retrieve caching pages) which results in their
Write Cache being discarded by queue requests i.e., WCE if left set to
'0'(disabled).
This results in a number of Filesystem corruptions, when the device
is unplugged abruptly.

So, in order to identify the devices correctly - give it
a last try using ATA_16 after failure from normal routine.

Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

---
 drivers/ata/libata-scsi.c |   51 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/scsi/sd.c         |   17 +++++++++++++++
 include/linux/libata.h    |    3 ++
 3 files changed, 71 insertions(+), 0 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 508a60b..d5b00e6 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -562,6 +562,57 @@ error:
 }
 
 /**
+ *      ata_get_cachestatus - Handler for to get WriteCache Status
+ *                      using ATA_16 scsi command
+ *      @scsidev: Device to which we are issuing command
+ *
+ *      LOCKING:
+ *      Defined by the SCSI layer.  We don't really care.
+ *
+ *      RETURNS:
+ *      '0' for Write Cache Disabled and on any error.
+ *      '1' for Write Cache enabled
+ */
+int ata_get_cachestatus(struct scsi_device *scsidev)
+{
+	int rc = 0;
+	u8 scsi_cmd[MAX_COMMAND_SIZE] = {0};
+	u8 *sensebuf = NULL, *argbuf = NULL;
+	enum dma_data_direction data_dir;
+
+	sensebuf = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
+	if (!sensebuf)
+		return rc;
+
+	argbuf = kmalloc(ATA_SECT_SIZE, GFP_KERNEL);
+	if (argbuf == NULL)
+		goto error;
+
+	scsi_cmd[0] = ATA_16;
+	scsi_cmd[1]  = (4 << 1); /* PIO Data-in */
+	scsi_cmd[2]  = 0x0e;     /* no off.line or cc, read from dev,
+				block count in sector count field */
+	data_dir = DMA_FROM_DEVICE;
+	scsi_cmd[14] = ATA_IDENTIFY_DEV;
+
+	if (!scsi_execute(scsidev, scsi_cmd, data_dir, argbuf, ATA_SECT_SIZE,
+				sensebuf, (10*HZ), 5, 0, NULL)) {
+		/*
+		 * '6th' Bit in Word 85 Corresponds to Write Cache
+		 * being Enabled/disabled, Word 85 represnets the
+		 * features supported
+		 */
+		if (le16_to_cpu(((unsigned short *)argbuf)[85]) & 0x20)
+			rc = 1;
+	}
+
+error:
+	kfree(sensebuf);
+	kfree(argbuf);
+	return rc;
+}
+
+/**
  *	ata_task_ioctl - Handler for HDIO_DRIVE_TASK ioctl
  *	@scsidev: Device to which we are issuing command
  *	@arg: User provided data for issuing command
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index c691fb5..a6b887d 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -50,6 +50,11 @@
 #include <linux/string_helpers.h>
 #include <linux/async.h>
 #include <linux/slab.h>
+
+#ifdef CONFIG_ATA
+#include <linux/libata.h>
+#endif
+
 #include <linux/pm_runtime.h>
 #include <asm/uaccess.h>
 #include <asm/unaligned.h>
@@ -2129,7 +2134,11 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 		if (modepage == 0x3F) {
 			sd_printk(KERN_ERR, sdkp, "No Caching mode page "
 				  "present\n");
+#ifdef CONFIG_ATA
+			goto WCE_USING_ATA;
+#else
 			goto defaults;
+#endif
 		} else if ((buffer[offset] & 0x3f) != modepage) {
 			sd_printk(KERN_ERR, sdkp, "Got wrong page\n");
 			goto defaults;
@@ -2149,6 +2158,14 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer)
 				  "Uses READ/WRITE(6), disabling FUA\n");
 			sdkp->DPOFUA = 0;
 		}
+#ifdef CONFIG_ATA
+WCE_USING_ATA:
+		if (!sdp->removable && !sdkp->WCE) {
+			sd_printk(KERN_NOTICE, sdkp, "Try to check write cache "
+				"enable/disable using ATA command\n");
+			sdkp->WCE = ata_get_cachestatus(sdp);
+		}
+#endif
 
 		if (sdkp->first_scan || old_wce != sdkp->WCE ||
 		    old_rcd != sdkp->RCD || old_dpofua != sdkp->DPOFUA)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index cafc09a..33fc73f 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -84,6 +84,8 @@
 	}							\
 })
 
+#define ATA_IDENTIFY_DEV	0xEC
+
 /* NEW: debug levels */
 #define HAVE_LIBATA_MSG 1
 
@@ -990,6 +992,7 @@ extern void ata_host_init(struct ata_host *, struct device *,
 			  unsigned long, struct ata_port_operations *);
 extern int ata_scsi_detect(struct scsi_host_template *sht);
 extern int ata_scsi_ioctl(struct scsi_device *dev, int cmd, void __user *arg);
+extern int ata_get_cachestatus(struct scsi_device *scsidev);
 extern int ata_scsi_queuecmd(struct Scsi_Host *h, struct scsi_cmnd *cmd);
 extern int ata_sas_scsi_ioctl(struct ata_port *ap, struct scsi_device *dev,
 			    int cmd, void __user *arg);
-- 
1.7.2.3