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Message-Id: <20070915023953.d364349d.akpm@linux-foundation.org>
Date: Sat, 15 Sep 2007 02:39:53 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Maurice Volaski <mvolaski@...om.yu.edu>
Cc: linux-lvm@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: Can LVM block I/O and hang a system?
On Wed, 12 Sep 2007 03:09:14 -0400 Maurice Volaski <mvolaski@...om.yu.edu> wrote:
> A working system begins hanging and it seems to be stuck on I/O
> processes that use ext3 partitions that are running on top of LVM.
> The system is AMD 64-bit running Gentoo. Kernel is Gentoo 2.6.22-r3
> and LVM lvm2-2.02.27. Here is the disk setup:
>
> Boot disk, attached to motherboard via SATA
> 1) some partitions accessed via ext3 -> hardware partition.
> 2) some partitions accessed via ext3 -> drbd, which is version 8.0.5,
> -> hardware partition.
>
> External SATA-SCSI RAID, attached to via an LSI Logic card,
> 3) one partition accessed via ext3 -> drbd -> hardware partition.
> 4) some partitions accessed via ext3 -> LVM -> drbd -> hardware partition.
>
> On repeated reboots, #1) boots fine, and I can fsck #2) no problem. I
> can also fsck #3, but the fsck processes on #4, which all are trying
> to recover the journals, just seem to not do anything. There is no
> evidence of I/O and there are no errors reported anywhere. The frozen
> fsck processes cannot even be killed and the system ignores the
> shutdown command.
>
> That the hanging fsck processes are all occurring on just the LVM
> partitions seems to imply that LVM is responsible.
>
> drbd had been unattached to its peer during this time, and when I
> reattached it, it had no trouble syncing to the peer. That system,
> which should basically be identical, however, has no trouble running
> running fsck everywhere. I'm not sure, though, if that lets LVM off
> the hook.
Next time it hangs, please do
dmesg -c
echo t > /proc/sysrq-trigger
dmesg -s 1000000 > foo
and send foo.
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