Re: BUG at scsi_lib.c:1108 [Was: mmotm 2009-11-24-16-47 uploaded]

[Neil Brown]

On Wed, 25 Nov 2009 21:22:57 +0100
Jiri Slaby <jirislaby@xxxxxxxxx> wrote:

> It doesn't make sense at all. How can empty merge cause a regression?
> And md/for-next doesn't produce the BUG.

I've hit that situation before.  Two separate changes in separate
branches conspire to cause a problem.

md/for-next contains code to handle barriers properly for all levels,
not just RAID1.
It is possible I got this wrong in some way, and some new sanity check
in a separate branch is firing, or it is possible some other bug in
barrier handling has been added and now that MD sends barriers, it is
being triggered.

What I did to find the actual offending patches is to got to one of the
heads just before the merge, and cherry-pick all the patches from the
other branch, and then bisect that.

NeilBrown
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