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

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

[Oliver Neukum]

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-IBi9RG/b67k@public.gmane.org>
---
 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-IBi9RG/b67k@public.gmane.org> */
+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-Tz8qtarvew8@public.gmane.org> */
 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

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

[Martin K. Petersen]

>>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:

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

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

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

[Oliver Neukum]

On Thu, 2016-08-18 at 22:19 -0400, Martin K. Petersen wrote:
> >>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:
> 
> Oliver> Some SATA to USB bridges fail to cooperate with some drives
> Oliver> resulting in no cache being present being reported to the
> Oliver> host. That causes the host to skip sending a command to
> Oliver> synchronize caches. That causes data loss when the drive is
> Oliver> powered down.
> 
> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
> 

Hi,

may I ask about the fate of this patch? Has it been lost?
Should I resubmit? Are any further changes necessary?

	Regards
		Oliver

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

[Martin K. Petersen]

>>>>> "Oliver" == Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> writes:

Oliver> On Thu, 2016-08-18 at 22:19 -0400, Martin K. Petersen wrote:
>> >>>>> "Oliver" == Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> writes:
>> 
Oliver> Some SATA to USB bridges fail to cooperate with some drives
Oliver> resulting in no cache being present being reported to the
Oliver> host. That causes the host to skip sending a command to
Oliver> synchronize caches. That causes data loss when the drive is
Oliver> powered down.
>> 
>> Reviewed-by: Martin K. Petersen <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
>> 

Oliver> may I ask about the fate of this patch? Has it been lost?
Oliver> Should I resubmit? Are any further changes necessary?

I'm OK with the change but it needs to go through the USB tree.

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

[Greg KH]

On Fri, Sep 09, 2016 at 07:26:17AM -0400, Martin K. Petersen wrote:
> >>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:
> 
> Oliver> On Thu, 2016-08-18 at 22:19 -0400, Martin K. Petersen wrote:
> >> >>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:
> >> 
> Oliver> Some SATA to USB bridges fail to cooperate with some drives
> Oliver> resulting in no cache being present being reported to the
> Oliver> host. That causes the host to skip sending a command to
> Oliver> synchronize caches. That causes data loss when the drive is
> Oliver> powered down.
> >> 
> >> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
> >> 
> 
> Oliver> may I ask about the fate of this patch? Has it been lost?
> Oliver> Should I resubmit? Are any further changes necessary?
> 
> I'm OK with the change but it needs to go through the USB tree.

Ugh, ok, this is gone from my queue, Oliver, can you resend it and I'll
queue it up?

thanks,

greg k-h

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

[Oliver Neukum]

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

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

[Alan Stern]

On Mon, 12 Sep 2016, Oliver Neukum wrote:

> 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>

Acked-by: Alan Stern <stern@rowland.harvard.edu>

> ---
>  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(-)

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

[Oliver Neukum]

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-IBi9RG/b67k@public.gmane.org>
Reviewed-by: Johannes Thumshirn <jthumshirn-l3A5Bk7waGM@public.gmane.org>
Tested-by: Egbert Eich <eich-IBi9RG/b67k@public.gmane.org>
---
 Documentation/kernel-parameters.txt | 2 ++
 drivers/scsi/sd.c                   | 6 +++---
 drivers/usb/storage/scsiglue.c      | 4 ++++
 drivers/usb/storage/unusual_devs.h  | 7 +++++++
 drivers/usb/storage/usb.c           | 6 +++++-
 include/linux/usb_usual.h           | 2 ++
 include/scsi/scsi_device.h          | 1 +
 7 files changed, 24 insertions(+), 4 deletions(-)

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/scsi/sd.c b/drivers/scsi/sd.c
index 60bff78..3e8a6f1 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -139,7 +139,7 @@ static void sd_set_flush_flag(struct scsi_disk *sdkp)
 {
 	bool wc = false, fua = false;
 
-	if (sdkp->WCE) {
+	if (sdkp->WCE || sdkp->device->always_sync) {
 		wc = true;
 		if (sdkp->DPOFUA)
 			fua = true;
@@ -3228,7 +3228,7 @@ static void sd_shutdown(struct device *dev)
 	if (pm_runtime_suspended(dev))
 		return;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present)  {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		sd_sync_cache(sdkp);
 	}
@@ -3247,7 +3247,7 @@ static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
 	if (!sdkp)	/* E.g.: runtime suspend following sd_remove() */
 		return 0;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present) {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		ret = sd_sync_cache(sdkp);
 		if (ret) {
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 33eb923..43e76ae 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -296,6 +296,10 @@ 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)
+			sdev->always_sync = 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-IBi9RG/b67k@public.gmane.org> */
+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-Tz8qtarvew8@public.gmane.org> */
 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 };
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index a6c346d..392d166 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -179,6 +179,7 @@ struct scsi_device {
 	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
 	unsigned is_visible:1;	/* is the device visible in sysfs */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
+	unsigned always_sync:1;		/* synchronize cache in every case*/
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
-- 
2.1.4

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

[Martin K. Petersen]

>>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:

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

Alan?

-- 
Martin K. Petersen	Oracle Linux Engineering

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

[Alan Stern]

On Mon, 8 Aug 2016, Martin K. Petersen wrote:

> >>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:
> 
> Oliver> Some SATA to USB bridges fail to cooperate with some drives
> Oliver> resulting in no cache being present being reported to the
> Oliver> host. That causes the host to skip sending a command to
> Oliver> synchronize caches. That causes data loss when the drive is
> Oliver> powered down.
> 
> Alan?

Oliver originally submitted this at least a month ago.  I don't see any 
changes since then, so:

Acked-by: Alan Stern <stern@rowland.harvard.edu>

Alan Stern

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

[Martin K. Petersen]

>>>>> "Oliver" == Oliver Neukum <oneukum@suse.com> writes:

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

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index a6c346d..392d166 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -179,6 +179,7 @@ struct scsi_device {
 	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
 	unsigned is_visible:1;	/* is the device visible in sysfs */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
+	unsigned always_sync:1;		/* synchronize cache in every case*/
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */

I must be missing something. How is always_sync different from just
setting wce_default_on?

-- 
Martin K. Petersen	Oracle Linux Engineering

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

[Oliver Neukum]

On Wed, 2016-08-10 at 22:40 -0400, Martin K. Petersen wrote:
> >>>>> "Oliver" == Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> writes:
> 
> Oliver> Some SATA to USB bridges fail to cooperate with some drives
> Oliver> resulting in no cache being present being reported to the
> Oliver> host. That causes the host to skip sending a command to
> Oliver> synchronize caches. That causes data loss when the drive is
> Oliver> powered down.
> 
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index a6c346d..392d166 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -179,6 +179,7 @@ struct scsi_device {
>  	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
>  	unsigned is_visible:1;	/* is the device visible in sysfs */
>  	unsigned wce_default_on:1;	/* Cache is ON by default */
> +	unsigned always_sync:1;		/* synchronize cache in every case*/
>  	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
>  	unsigned broken_fua:1;		/* Don't set FUA bit */
>  	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
> 
> I must be missing something. How is always_sync different from just
> setting wce_default_on?

Hi,

wce_default_on controls the default if the device provides no
indication. The problem here is that the indication the device
provides must be overridden, as they are false.

	Regards
		Oliver


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

[Martin K. Petersen]

>>>>> "Oliver" == Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> writes:

Oliver,

Oliver> wce_default_on controls the default if the device provides no
Oliver> indication. The problem here is that the indication the device
Oliver> provides must be overridden, as they are false.

Can't you just blacklist the mode select on the device in question?

Something like:

	if (us->fflags & US_FL_ALWAYS_SYNC) {
		sdev->skip_ms_page_3f = 1;
		sdev->skip_ms_page_8 = 1;
		sdev->wce_default_on = 1;
	}

?

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

[Oliver Neukum]

On Tue, 2016-08-16 at 00:44 -0400, Martin K. Petersen wrote:
> >>>>> "Oliver" == Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> writes:
> 
> Oliver,
> 
> Oliver> wce_default_on controls the default if the device provides no
> Oliver> indication. The problem here is that the indication the device
> Oliver> provides must be overridden, as they are false.
> 
> Can't you just blacklist the mode select on the device in question?
> 
> Something like:
> 
> 	if (us->fflags & US_FL_ALWAYS_SYNC) {
> 		sdev->skip_ms_page_3f = 1;
> 		sdev->skip_ms_page_8 = 1;
> 		sdev->wce_default_on = 1;
> 	}
> 
> ?

Hi,

this looks like a workable option. I am preparing a patch.

	Regards
		Oliver




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

[Oliver Neukum]

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>
---
 Documentation/kernel-parameters.txt | 2 ++
 drivers/scsi/sd.c                   | 6 +++---
 drivers/usb/storage/scsiglue.c      | 4 ++++
 drivers/usb/storage/unusual_devs.h  | 7 +++++++
 drivers/usb/storage/usb.c           | 6 +++++-
 include/linux/usb_usual.h           | 2 ++
 include/scsi/scsi_device.h          | 1 +
 7 files changed, 24 insertions(+), 4 deletions(-)

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/scsi/sd.c b/drivers/scsi/sd.c
index 60bff78..3e8a6f1 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -139,7 +139,7 @@ static void sd_set_flush_flag(struct scsi_disk *sdkp)
 {
 	bool wc = false, fua = false;
 
-	if (sdkp->WCE) {
+	if (sdkp->WCE || sdkp->device->always_sync) {
 		wc = true;
 		if (sdkp->DPOFUA)
 			fua = true;
@@ -3228,7 +3228,7 @@ static void sd_shutdown(struct device *dev)
 	if (pm_runtime_suspended(dev))
 		return;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present)  {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		sd_sync_cache(sdkp);
 	}
@@ -3247,7 +3247,7 @@ static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
 	if (!sdkp)	/* E.g.: runtime suspend following sd_remove() */
 		return 0;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present) {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		ret = sd_sync_cache(sdkp);
 		if (ret) {
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 33eb923..43e76ae 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -296,6 +296,10 @@ 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)
+			sdev->always_sync = 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 };
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index a6c346d..392d166 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -179,6 +179,7 @@ struct scsi_device {
 	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
 	unsigned is_visible:1;	/* is the device visible in sysfs */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
+	unsigned always_sync:1;		/* synchronize cache in every case*/
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
-- 
2.1.4

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

[Oliver Neukum]

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>
---
 Documentation/kernel-parameters.txt | 2 ++
 drivers/scsi/sd.c                   | 6 +++---
 drivers/usb/storage/scsiglue.c      | 4 ++++
 drivers/usb/storage/usb.c           | 6 +++++-
 include/linux/usb_usual.h           | 2 ++
 include/scsi/scsi_device.h          | 1 +
 6 files changed, 17 insertions(+), 4 deletions(-)

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/scsi/sd.c b/drivers/scsi/sd.c
index 60bff78..3e8a6f1 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -139,7 +139,7 @@ static void sd_set_flush_flag(struct scsi_disk *sdkp)
 {
 	bool wc = false, fua = false;
 
-	if (sdkp->WCE) {
+	if (sdkp->WCE || sdkp->device->always_sync) {
 		wc = true;
 		if (sdkp->DPOFUA)
 			fua = true;
@@ -3228,7 +3228,7 @@ static void sd_shutdown(struct device *dev)
 	if (pm_runtime_suspended(dev))
 		return;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present)  {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		sd_sync_cache(sdkp);
 	}
@@ -3247,7 +3247,7 @@ static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
 	if (!sdkp)	/* E.g.: runtime suspend following sd_remove() */
 		return 0;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present) {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		ret = sd_sync_cache(sdkp);
 		if (ret) {
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 33eb923..43e76ae 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -296,6 +296,10 @@ 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)
+			sdev->always_sync = 1;
+
 	} else {
 
 		/*
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 };
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index a6c346d..392d166 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -179,6 +179,7 @@ struct scsi_device {
 	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
 	unsigned is_visible:1;	/* is the device visible in sysfs */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
+	unsigned always_sync:1;		/* synchronize cache in every case*/
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
-- 
2.1.4

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

[Johannes Thumshirn]

On Tue, Jul 12, 2016 at 10:24:36AM +0200, Oliver Neukum wrote:
> 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-IBi9RG/b67k@public.gmane.org>

Reviewed-by: Johannes Thumshirn <jthumshirn-l3A5Bk7waGM@public.gmane.org>

-- 
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jthumshirn-l3A5Bk7waGM@public.gmane.org                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
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[PATCH] scsi: introduce a quirk for false cache reporting

[Oliver Neukum]

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>
---
 drivers/scsi/sd.c              | 6 +++---
 drivers/usb/storage/scsiglue.c | 4 ++++
 drivers/usb/storage/usb.c      | 6 +++++-
 include/linux/usb_usual.h      | 2 ++
 include/scsi/scsi_device.h     | 1 +
 5 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 60bff78..3e8a6f1 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -139,7 +139,7 @@ static void sd_set_flush_flag(struct scsi_disk *sdkp)
 {
 	bool wc = false, fua = false;
 
-	if (sdkp->WCE) {
+	if (sdkp->WCE || sdkp->device->always_sync) {
 		wc = true;
 		if (sdkp->DPOFUA)
 			fua = true;
@@ -3228,7 +3228,7 @@ static void sd_shutdown(struct device *dev)
 	if (pm_runtime_suspended(dev))
 		return;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present)  {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		sd_sync_cache(sdkp);
 	}
@@ -3247,7 +3247,7 @@ static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
 	if (!sdkp)	/* E.g.: runtime suspend following sd_remove() */
 		return 0;
 
-	if (sdkp->WCE && sdkp->media_present) {
+	if ((sdkp->WCE || sdkp->device->always_sync) && sdkp->media_present) {
 		sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
 		ret = sd_sync_cache(sdkp);
 		if (ret) {
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 33eb923..43e76ae 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -296,6 +296,10 @@ 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)
+			sdev->always_sync = 1;
+
 	} else {
 
 		/*
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 };
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index a6c346d..392d166 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -179,6 +179,7 @@ struct scsi_device {
 	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
 	unsigned is_visible:1;	/* is the device visible in sysfs */
 	unsigned wce_default_on:1;	/* Cache is ON by default */
+	unsigned always_sync:1;		/* synchronize cache in every case*/
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
-- 
2.1.4

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

[Alan Stern]

On Mon, 11 Jul 2016, Oliver Neukum wrote:

> 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.

> @@ -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 */
>  		}
>  	}

You need to update Documentation/kernel-parameters.txt too.

Alan Stern