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Date:   Wed, 3 Jul 2019 02:00:55 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Christoph Hellwig <hch@lst.de>, Matias Bjorling <mb@lightnvm.io>,
        linux-block@vger.kernel.org
Subject: Re: remove bi_phys_segments and related cleanups
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On Tue, Jul 02, 2019 at 12:37:59PM -0600, Jens Axboe wrote:
> > I couldn't get that to boot in my test systems even with mainline,
> > but that seems to be do to systemd waiting for some crap not supported
> > in the config.
> > 
> > But with my usual test config I've just completed a test run with
> > KASAN enabled on a VWC=1 driver with no issues, so this keeps puzzling
> > me.
> 
> Let me know what you want me to try. I can't reproduce it in qemu, but
> it's 100% on my laptop. My qemu drives also have VWC=1, so it's not
> (just) that.

I seriously have no idea unfortunately.  It works fine for me both
on qemu and on a real WD SN720 drive on my laptop.  Just for curiosity
you could try to pad the bio structure and see if bloating it to the
old size makes any difference.

The other things that comes to mind is that when Johannes removed
BIO_SEG_VALID there also were some unexplainable side effects,
I'll look into seeing if there was any similarity.