[Bug 219652] READ CAPACITY(16) not used on large USB-attached drive in recent kernels

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=219652

--- Comment #6 from michael.christie@oracle.com ---
On 1/1/25 6:57 PM, bugzilla-daemon@kernel.org wrote:
> * When booting into kernel 6.12.7, the external drive capacity
>   is mis-reported.  Booting /back/ into 6.6.68, the capacity
>   continues to be mis-reported.  One must now yank the USB
>   cable (or power-cycle) to get the correct size detection again.

That part is really strange. I wonder if the new code is not
resetting the device and the old code was somehow.
> 
> Here is a diff of the dmesg output when plugging in the drive.
> From (-) is kernel 6.1.122
> To   (+) is kernel 6.12.7:
>  scsi host12: usb-storage 1-13:1.0
>  scsi 12:0:0:0: Direct-Access     TOSHIBA  DT01ACA300       3.00 PQ: 0 ANSI:
>  4
>  sd 12:0:0:0: Attached scsi generic sg1 type 0
> -sd 12:0:0:0: [sdb] Very big device. Trying to use READ CAPACITY(16).
> -sd 12:0:0:0: [sdb] 5860533167 512-byte logical blocks: (3.00 TB/2.73 TiB)
> +sd 12:0:0:0: [sdb] 4294967295 512-byte logical blocks: (2.20 TB/2.00 TiB)
>  sd 12:0:0:0: [sdb] Write Protect is off
>  sd 12:0:0:0: [sdb] Mode Sense: 23 00 00 00
>  sd 12:0:0:0: [sdb] No Caching mode page found
>  sd 12:0:0:0: [sdb] Assuming drive cache: write through
> -sd 12:0:0:0: [sdb] Very big device. Trying to use READ CAPACITY(16).
> - sdb: sdb1
>  sd 12:0:0:0: [sdb] Attached SCSI disk
> 
> I am attaching a diff of the usbmon output for the earlier kernel (good) and
> current kernel (bad),

Just to start can you tell me what the device is returning?

We hit that "Very big device" code path if the device returns a size
of 0xffffffff or larger so with the old code we at some point returned
a large size. With the new code the device returns only 0xfffffffe
(4294967294) (read_capacity_10 does a lba that we got from the device + 1
so you see 4294967295 in the log message) so we never hit that very
bit device code path and try READ CAPACITY(16).

I might have changed some behavior during the retries that causes us
to not get the right size now.  However, I couldn't fully understand
the output of the usbmon traces. Can you tell me when we do the READ
CAPACITY (10) what the device is returning? Is it returning a sense
error like UNIT_ATTENTION a couple times and when it returns success
what's in the data buffer?

-- 
You may reply to this email to add a comment.

You are receiving this mail because:
You are the assignee for the bug.