Re: iSCSI regression with linux 3.9 and 4.0

[Christian Hesse <list@eworm.de>]

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Ewan Milne <emilne@redhat.com> on Fri, 2015/03/20 11:04:
> On Fri, 2015-03-20 at 15:31 +0100, Christian Hesse wrote:
> > Ewan Milne <emilne@redhat.com> on Fri, 2015/03/20 09:51:
> > > On Fri, 2015-03-20 at 13:57 +0100, Christian Hesse wrote:
> > > > Hello everybody!
> > > > 
> > > > I reported this issue at LKML [0] but received no answer. Hopefully
> > > > linux-scsi is a better place...
> > > > 
> > > > Beginning with linux 3.19 I see an iSCSI regressen. This works
> > > > perfectly with linux 3.18.x (tested with 3.18.6) and before. Effected
> > > > kernels I tested are 3.19.0, 3.19.2 and 4.0rc4.r199.gb314aca.
> > > > 
> > > > The logs tell the story:
> > > > 
> > > > [snip log]
> > > > 
> > > > [0] https://lkml.org/lkml/2015/2/19/91
> > > 
> > > Sense key 0x5 ASC/ASCQ 0x24 0x00 is ILLEGAL REQUEST, INVALID FIELD IN
> > > CDB.  The CDB was 2A 00 34 5B 07 FF 00 2F 88 00, which is a WRITE_10
> > > to LBA 878381055 with a length of 12168 blocks (a little less than 6MB).
> > > It looks like this is within the reported capacity of the device, and
> > > there are no other bits set in the CDB.
> > > 
> > > Looks like you could get this error if RWWP (reject without write
> > > protection) is set in the control mode page.  I don't see any messages
> > > about the protection type, though.  What does sysfs report?
> > 
> > Is that what you are interested in?
> > 
> > # cat protection_mode protection_type 
> > none
> > 0
> > 
> > In case it matters: The iSCSI device is LUKS encrypted, that is why device
> > mapper shows up.
> > 
> > I removed the discard option from filesystem's default mount option, but
> > that brings no difference except the message is not printed.
> 
> It is most likely the device that is returning the error, there is a
> place in the iSCSI Initiator that generates an ILLEGAL REQUEST sense,
> but it is not the same ASC/ASCQ.
> 
> There was this change:
> 
> commit bcdb247c6b6a1f3e72b9b787b73f47dd509d17ec
> Author: Martin K. Petersen <martin.petersen@oracle.com>
> Date:   Tue Jun 3 18:45:51 2014 -0400
> 
>     sd: Limit transfer length
>     
>     Until now the per-command transfer length has exclusively been gated by
>     the max_sectors parameter in the scsi_host template. Given that the size
>     of this parameter has been bumped to an unsigned int we have to be
>     careful not to exceed the target device's capabilities.
>     
>     If the if the device specifies a Maximum Transfer Length in the Block
>     Limits VPD we'll use that value. Otherwise we'll use 0xffffffff for
>     devices that have use_16_for_rw set and 0xffff for the rest. We then
>     combine the chosen disk limit with max_sectors in the host template. The
>     smaller of the two will be used to set the max_hw_sectors queue limit.
>     
>     Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
>     Reviewed-by: Ewan D. Milne <emilne@redhat.com>
>     Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> What is the value of max_sectors_kb and queue_max_sectors_kb in sysfs
> for the device?  Is it different than what is reported on 3.18?

I found 'max_sectors_kb' which is inside in directory called 'queue'. Is that
the value you asked for?

for 4.0 git:

# cat max_sectors_kb
32767

for 3.18.6:

# cat max_sectors_kb
512

> Does your target support the Block Limits VPD (page B0)?  (i.e. can
> you run "sg_inq /dev/sda -p bl" from the sg3_utils package?)

This does not differ for different kernels. I think this is expected.

# sg_inq /dev/sdb -p bl
VPD INQUIRY: Block limits page (SBC)
  Maximum compare and write length: 1 blocks
  Optimal transfer length granularity: 1 blocks
  Maximum transfer length: 4294967295 blocks
  Optimal transfer length: 4294967295 blocks
  Maximum prefetch, xdread, xdwrite transfer length: 0 blocks
  Maximum unmap LBA count: 8388607
  Maximum unmap block descriptor count: 1
  Optimal unmap granularity: 16383
  Unmap granularity alignment valid: 0
  Unmap granularity alignment: 0
  Maximum write same length: 0xffffffff blocks
  Maximum atomic transfer length: 0
  Atomic alignment: 0
  Atomic transfer length granularity: 0
-- 
main(a){char*c=/*    Schoene Gruesse                         */"B?IJj;MEH"
"CX:;",b;for(a/*    Chris           get my mail address:    */=0;b=c[a++];)
putchar(b-1/(/*               gcc -o sig sig.c && ./sig    */b/42*2-3)*42);}

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