Re: Issues with commit 34b48db6 ("block: remove artifical max_hw_sectors cap")

On Sun, Dec 21, 2014 at 02:44:20PM -0800, Kenneth R. Crudup wrote:

quoted

I had issues with my Samsung 4GB disk recently in Linus' master tree kernels,
and have bisected it to the above commit. When doing running bonnie++ (etc.
I get EIOs.

quoted

Is there a "quirks" available for this option so I may special-case this
particular disk?

On Tue, 23 Dec 2014, Christoph Hellwig wrote:

Looks like we need to quirk it.  Can you try to echo different limits
to the /sys/block/sdc/queue/max_hw_sectors_kb  file for the device to
find the limit for it?

Looks like it's 32767; making it an even 32K sectors starts the EIOs again.

To recap for the various lists:

  Vendor: Samsung  Model: D3 Station       Rev: 0202
  Type:   Direct-Access                    ANSI  SCSI revision: 06

It's the 4TB model:

/sys/block/sdc/size:7814037160
/sys/block/sdc/queue/max_hw_sectors_kb:61440

Works OK if I echo 32767 > /sys/block/sdc/queue/max_sectors_kb

Has anyone seen a disk out there that's got a (properly-supported)
"max_hw_sectors_kb" >= 32K? If not, maybe we should clamp that value to
prevent other misreporting(?) disks?

	-Kenny

-- 
Kenneth R. Crudup  Sr. SW Engineer, Scott County Consulting, Silicon Valley