On Monday 30 January 2017 17:17:03 Alan Stern wrote:
> 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.
I'm not original reporter of this problem.
Dainius, can you test 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 */
--
Pali Rohár
pali.rohar@xxxxxxxxx
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