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Message-ID: <1454886441.2329.27.camel@HansenPartnership.com>
Date: Sun, 07 Feb 2016 15:07:21 -0800
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>
Cc: "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
linux-block@...r.kernel.org,
linux-scsi <linux-scsi@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: complete boot failure in 4.5-rc1 caused by nvme: make SG_IO
support optional
On Sun, 2016-02-07 at 15:28 -0700, Jens Axboe wrote:
> On 02/07/2016 09:04 AM, James Bottomley wrote:
> > On Sun, 2016-02-07 at 10:22 +0100, Christoph Hellwig wrote:
> > > Keith said it should be on by default, and I promised him to
> > > change
> > > it once we run into problems, which I guess this counts as.
> > >
> > > But just curious: what distro are you using? Upstream systemd
> > > explicitly rejected using scsi_id for NVMe here:
> > >
> > > https://github.com/systemd/systemd/issues/1453
> > >
> > > and all my test systems don't do this either.
> >
> > This was SUSE (in my case, openSUSE Leap). I just checked the
> > source
> > package; they patch the by-id rules back in for NVME:
> >
> > # PATCH-FIX-SUSE 1101-rules-persistent-device-names-for-NVMe
> > -devices.patch (bsc#944132)
> > Patch1101: 1101-rules-persistent-device-names-for-NVMe
> > -devices.patch
> >
> > The bugzilla is giving access denied for bug id 944132, so it's
> > likely
> > some proprietary vendor problem. The patch has no preamble, so
> > it's
> > hard to tell what they were thinking.
>
> I run root-on-nvme on my laptop, and I haven't observed any problems.
Me too apparently. It looks like this problem may be SUSE specific
unless another distro has enabled this. I can see why they would: you
do need persistent names for devices, even NVMe ones.
> Generally I hate for options to default y unless absolutely
> necessary, it's a sure fire way to feature creep your kernel without
> noticing. I don't think getting all hot about this issue is fair, if
> the only known case is suse.
Well, OK, I'm annoyed because it was a systemd system which means
debugging boot failures are excruciatingly difficult so it took me a
week and a half to find out what the problem was. Perhaps I was a bit
rash to label this as an easily foreseen problem.
I opened a bug against SUSE to tell them to turn it on:
https://bugzilla.opensuse.org/show_bug.cgi?id=965497
The second problem is that there's currently no way to transition to
using the serial attribute the way the udev 60-persistent-storage.rules
are written, so if distros have some by-id hack, it will have to be
maintained for a while. I annotated the already closed bug on this in
systemd with the rules that work for me.
> If anything, let's make the description better. It's trying to be
> funny, it'd be better if it was descriptive and covered this case as
> well.
The problem with this is that when moving to new kernels, distro
maintainers don't read the new option help texts, they just take the
defaults. However, I checked the only other distribution I use
(debian) and they don't have a nvme persistent ID hack, so if someone
checked ubuntu and Red Hat, I think all the majors are now covered and
perhaps there's no need to do anything more.
James
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