[PATCH] scsi: introduce a quirk for false cache reporting

From: Oliver Neukum <oneukum@suse.com>
To: linux-scsi@vger.kernel.org, linux-usb@vger.kernel.org,
	usb-storage@lists.one-eyed-alien.net, gregKH@linuxfoundation.org
Cc: Oliver Neukum <oneukum@suse.com>
Subject: [PATCH] scsi: introduce a quirk for false cache reporting
Date: Mon, 12 Sep 2016 15:19:41 +0200	[thread overview]
Message-ID: <1473686381-17259-1-git-send-email-oneukum@suse.com> (raw)

Some SATA to USB bridges fail to cooperate with some
drives resulting in no cache being present being reported
to the host. That causes the host to skip sending
a command to synchronize caches. That causes data loss
when the drive is powered down.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
---
 Documentation/kernel-parameters.txt | 2 ++
 drivers/usb/storage/scsiglue.c      | 8 ++++++++
 drivers/usb/storage/unusual_devs.h  | 7 +++++++
 drivers/usb/storage/usb.c           | 6 +++++-
 include/linux/usb_usual.h           | 2 ++
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c9..c8c682e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -4182,6 +4182,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				u = IGNORE_UAS (don't bind to the uas driver);
 				w = NO_WP_DETECT (don't test whether the
 					medium is write-protected).
+				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
+					even if the device claims no cache)
 			Example: quirks=0419:aaf5:rl,0421:0433:rc
 
 	user_debug=	[KNL,ARM]
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 33eb923..8cd2926 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -296,6 +296,14 @@ static int slave_configure(struct scsi_device *sdev)
 		if (us->fflags & US_FL_BROKEN_FUA)
 			sdev->broken_fua = 1;
 
+		/* Some even totally fail to indicate a cache */
+		if (us->fflags & US_FL_ALWAYS_SYNC) {
+			/* don't read caching information */
+			sdev->skip_ms_page_8 = 1;
+			sdev->skip_ms_page_3f = 1;
+			/* assume sync is needed */
+			sdev->wce_default_on = 1;
+		}
 	} else {
 
 		/*
diff --git a/drivers/usb/storage/unusual_devs.h b/drivers/usb/storage/unusual_devs.h
index aa35392..af3c7ee 100644
--- a/drivers/usb/storage/unusual_devs.h
+++ b/drivers/usb/storage/unusual_devs.h
@@ -338,6 +338,13 @@ UNUSUAL_DEV(  0x046b, 0xff40, 0x0100, 0x0100,
 		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
 		US_FL_NO_WP_DETECT),
 
+/* Reported by Egbert Eich <eich@suse.com> */
+UNUSUAL_DEV(  0x0480, 0xd010, 0x0100, 0x9999,
+		"Toshiba",
+		"External USB 3.0",
+		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
+		US_FL_ALWAYS_SYNC),
+
 /* Patch submitted by Philipp Friedrich <philipp@void.at> */
 UNUSUAL_DEV(  0x0482, 0x0100, 0x0100, 0x0100,
 		"Kyocera",
diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index ef2d8cd..19255f1 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -498,7 +498,8 @@ void usb_stor_adjust_quirks(struct usb_device *udev, unsigned long *fflags)
 			US_FL_NO_READ_DISC_INFO | US_FL_NO_READ_CAPACITY_16 |
 			US_FL_INITIAL_READ10 | US_FL_WRITE_CACHE |
 			US_FL_NO_ATA_1X | US_FL_NO_REPORT_OPCODES |
-			US_FL_MAX_SECTORS_240 | US_FL_NO_REPORT_LUNS);
+			US_FL_MAX_SECTORS_240 | US_FL_NO_REPORT_LUNS |
+			US_FL_ALWAYS_SYNC);
 
 	p = quirks;
 	while (*p) {
@@ -581,6 +582,9 @@ void usb_stor_adjust_quirks(struct usb_device *udev, unsigned long *fflags)
 		case 'w':
 			f |= US_FL_NO_WP_DETECT;
 			break;
+		case 'y':
+			f |= US_FL_ALWAYS_SYNC;
+			break;
 		/* Ignore unrecognized flag characters */
 		}
 	}
diff --git a/include/linux/usb_usual.h b/include/linux/usb_usual.h
index 245f57d..0aae1b2 100644
--- a/include/linux/usb_usual.h
+++ b/include/linux/usb_usual.h
@@ -81,6 +81,8 @@
 		/* Sets max_sectors to 240 */			\
 	US_FLAG(NO_REPORT_LUNS,	0x10000000)			\
 		/* Cannot handle REPORT_LUNS */			\
+	US_FLAG(ALWAYS_SYNC, 0x20000000)			\
+		/* lies about caching, so always sync */	\
 
 #define US_FLAG(name, value)	US_FL_##name = value ,
 enum { US_DO_ALL_FLAGS };
-- 
2.1.4

