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

[Joseph Salisbury]

On 12/14/2012 04:11 PM, Mike Snitzer wrote:
> On Fri, Dec 14 2012 at  3:30pm -0500,
> Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx> 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@xxxxxxxxxx>
> > 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.
From Linus' tree:
git describe --contains 5db4486
v3.7-rc7~19^2

Reverting commit 5db4486 solves the bug previously mentioned.

> 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?

Yes, v3.7 without reverting 5db4486 exhibits the bug.

> Mike
I'll research further and provide additional data.
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