Re: [PATCH 2/2] sd: Try READ CAPACITY 16 first for SBC-2 devices

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2009-03-12 at 14:20 -0400, Matthew Wilcox wrote:
> From: Matthew Wilcox <matthew@wil.cx>
> 
> New features are being added to the READ CAPACITY 16 results, so we
> want to issue it in preference to READ CAPACITY 10.  Unfortunately, some
> devices misbehave when they see a READ CAPACITY 16, so we restrict this
> command to devices which claim conformance to SPC-3 (aka SBC-2), or claim
> they have features which are only reported in the READ CAPACITY 16 data.
> 
> The READ CAPACITY 16 command is optional, even for SBC-2 devices, so
> we fall back to READ CAPACITY 10 if READ CAPACITY 16 fails.

We're going to have to do something about the scary error messages on
SBC-2 supporting drives, this is what mine say (and this is after mkp's
chat reduction):

sd 1:0:1:0: [sdc] READ CAPACITY(16) failed
sd 1:0:1:0: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
sd 1:0:1:0: [sdc] Sense Key : Illegal Request [current] 
sd 1:0:1:0: [sdc] Add. Sense: Invalid command operation code
sd 1:0:1:0: [sdc] 71096640 512-byte hardware sectors: (36.4 GB/33.9 GiB)
sd 1:0:1:0: [sdc] Write Protect is off
sd 1:0:1:0: [sdc] Write cache: disabled, read cache: enabled, supports DPO and FUA
sd 1:0:1:0: [sdc] READ CAPACITY(16) failed
sd 1:0:1:0: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
sd 1:0:1:0: [sdc] Sense Key : Illegal Request [current] 
sd 1:0:1:0: [sdc] Add. Sense: Invalid command operation code
 sdc: sdc1 sdc2 sdc3
sd 1:0:1:0: [sdc] Attached SCSI disk

What they're saying is that they don't support READ CAPACITY(16) which
is perfectly legal for SBC-2 conforming devices which don't support
protection information ... like almost every modern disk in the field.

James