On Sun, 29 Jan 2017, Pali Rohár wrote:
> On Wednesday 11 January 2017 16:23:29 Alan Stern wrote:
> > On Tue, 10 Jan 2017, James Bottomley wrote:
> > > On Tue, 2017-01-10 at 16:00 -0500, Alan Stern wrote:
> > > > In theory, I suppose we could change the kernel so that it would
> > > > default to READ CAPACITY(16) for devices that report a SCSI level
> > > > >= 3, or something along those lines. In general we hesitate to
> > > > make changes of this sort, because they almost always end up
> > > > breaking _some_ devices -- and if that happens then the change
> > > > is reverted, with no exceptions. Linus has a very strict rule
> > > > about not breaking working systems.
> > >
> > > You shouldn't have to change anything: it already does (otherwise
> > > how else would we detect physical exponent for proper SCSI
> > > devices) see sd.c:sd_try_rc16_first(). It always returns false
> > > for USB because you set sdev->try_rc_10_first
> >
> > In fact, this approach probably won't work. See Bugzilla entries
> > #43265 and #43391. The devices in those reports claimed to be ANSI
> > level 4, but they failed anyway.
>
> Seems those devices return capacity 0x7F000000000001 or 0xFF000000000001
> Maybe there is some error pattern?
As far as I can tell, they both reported 0xFF000000000001. That's a
pattern -- unless somebody really does have a storage device that
large (18 exabytes). For the time being, perhaps we can ignore this
possibility.
> > If you guys want to try the quirk flag, you can apply the patch
> > below. Then set the usb-storage module parameter quirks=vvvv:pppp:k
> > where vvvv and pppp are the Vendor and Product ID codes for your
> > device (as 4 hex digits).
> >
> > In the long run, however, this is not a viable approach. We'd be
> > better off with an explicit blacklist.
>
> Ok, so what are next steps? I think that explicit blacklist would be
> needed if "bad" devices is less.
>
> How many bug reports were there?
I don't know.
Anyway, please try out the patch below. I don't know if it will be
acceptable to the SCSI maintainers, but we should at least make sure it
fixes your problem before submitting it.
Alan Stern
Index: usb-4.x/drivers/scsi/sd.c
===================================================================
--- usb-4.x.orig/drivers/scsi/sd.c
+++ usb-4.x/drivers/scsi/sd.c
@@ -2157,6 +2157,13 @@ static int read_capacity_16(struct scsi_
return -ENODEV;
}
+ /* Some buggy devices report an impossibly large size */
+ if (lba >= (1ULL << 54)) {
+ sd_printk(KERN_WARNING, sdkp, "Read Capacity(16) returned excessively large value: %llu", lba);
+ sdkp->capacity = 0;
+ return -EINVAL;
+ }
+
if ((sizeof(sdkp->capacity) == 4) && (lba >= 0xffffffffULL)) {
sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
"kernel compiled with support for large block "
Index: usb-4.x/drivers/usb/storage/scsiglue.c
===================================================================
--- usb-4.x.orig/drivers/usb/storage/scsiglue.c
+++ usb-4.x/drivers/usb/storage/scsiglue.c
@@ -247,8 +247,11 @@ static int slave_configure(struct scsi_d
* Tell the SCSI layer to try READ_CAPACITY_10 first.
* However some USB 3.0 drive enclosures return capacity
* modulo 2TB. Those must use READ_CAPACITY_16
+ *
+ * Assume SPC3 or later devices can handle READ_CAPACITY_16.
*/
- if (!(us->fflags & US_FL_NEEDS_CAP16))
+ if (sdev->scsi_level <= SCSI_SPC_2 &&
+ !(us->fflags & US_FL_NEEDS_CAP16))
sdev->try_rc_10_first = 1;
/* assume SPC3 or latter devices support sense size > 18 */
--
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