[Bug 6943] linux-kernel-header: O_NOATIME needed for lvm

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Mon Feb 28 03:30:52 UTC 2005

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------- Additional Comments From debzilla at ubuntu.com  2005-02-28 03:30 UTC -------
Message-ID: <87hdjxv1r3.fsf at informatik.uni-tuebingen.de>
Date: Mon, 28 Feb 2005 03:48:00 +0100
From: Goswin von Brederlow <brederlo at informatik.uni-tuebingen.de>
To: GOTO Masanori <gotom at debian.or.jp>
Cc: 297010 at bugs.debian.org, Bastian Blank <waldi at debian.org>
Subject: Re: Bug#297010: linux-kernel-header: O_NOATIME needed for lvm

GOTO Masanori <gotom at debian.or.jp> writes:

> At Sat, 26 Feb 2005 14:40:33 +0100,
> Goswin Brederlow wrote:
>> Package: linux-kernel-headers
>> Version: 2.5.999-test7-bk-17
>> Severity: critical
>> File: linux-kernel-header
>> Justification: breaks the whole system
>> Hi,
>> when one tries to run pvmove or lvsnapshot on / the lvm will deadlock
>> itself due to atime updates on /dev/ being blocked while the LVM is
>> locked. Sine any read/write access to / will be blocked the system
>> breaks.
>> To prevent this lvm uses O_NOATIME where available, which is still not
>> the case in current linux-kernel-headers.
> I couldn't understand why this problem is occured.  O_NOATIME was
> introduced in 2.6.7.  Is the root of problem to upgrading lvm package?
> Bastian's patch adds only O_NOATIME flag - this means that lvm can fix
> using O_NOATIME in your new package.  In other words, lvm is
> "severity: critical", but glibc is not.  lvm is kernel related
> package, so depending on libc6 header sometimes causes problems.

The docs (man 2 open) document O_NOATIME but the headers are lacking
behind in carrying the implementation. So you got stuck with it as
primary package. Notice that lvm2 is secondary. If lvm adds a
workaround the priority drops but you are still missing documented
behaviour, behaviour the sarge kernel (2.6.8) has.

Bastian's patch is just a workaround around the bug not its solution.

> So I recommend that lvm should use O_NOATIME definition in your
> package for a while.

The while is getting realy long, I mentioned this issue several month
ago already and it is still not fixed.

> Regards,
> -- gotom


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