Re: [v3.7 Regression] [SCSI] sd: Implement support for WRITE SAME

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Dec 14 2012 at  3:30pm -0500,
Joseph Salisbury <joseph.salisbury@canonical.com> wrote:

> Hi Martin,
> 
> A bug was opened against the Ubuntu kernel[0].  After a kernel
> bisect, it was found that reverting the following commit resolved
> this bug:
> 
> commit 5db44863b6ebbb400c5e61d56ebe8f21ef48b1bd
> Author: Martin K. Petersen <martin.petersen@oracle.com>
> Date:   Tue Sep 18 12:19:32 2012 -0400
> [SCSI] sd: Implement support for WRITE SAME
> 
> The regression was introduced as of v3.7-rc7.
> 
> The bug can be reproduced with the following commands, which will
> operate on a virtual scsi_debug device, so they won't change any
> data on the test system. However, this will completely crash the
> system:
> 
> sudo modprobe scsi_debug
> sudo luksformat -t ext4 /dev/sdb <- Or whatever device gets assigned
> after inserting scsi_debug.
> sudo cryptsetup luksOpen /dev/sdb treasure
> 
> Everything works fine up to here, but the following will cause the crash:
> 
> sudo mount /dev/mapper/treasure /mnt
> 
> The bug can be reproduced on bare metal, in a VM and on i386 or amd64.
> 
> I see that you are the author of this patch, so I wanted to run this
> by you.  I was thinking of requesting a revert for v3.7, but I
> wanted to get your feedback first.
> 
> 
> Thanks,
> 
> Joe
> 
> 
> [0] https://bugs.launchpad.net/bugs/1089818

The WRITE SAME change was introduced long before v3.7-rc7.  I think your
bisect is somehow wrong.

Milan Broz recently pointed out issues he found with luks when using a
late 3.7-rc (rc7 afaik).  Linus fixed that issue with this commit (which
landed in the final v3.7):
http://git.kernel.org/linus/684c9aaebbb0ea3a9954

That may not be _the_ problem though.  But have you tried the final
v3.7?

Mike