linux-kernel - Re: Oops in d_instantiate (fs/cache.c)

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Date:	Mon, 12 Dec 2011 12:35:52 +0100
From:	Stijn Devriendt <highguy@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: Oops in d_instantiate (fs/cache.c)

On Sat, Dec 3, 2011 at 1:19 PM, Stijn Devriendt <highguy@...il.com> wrote:
> Hi all,
>
> I've had 2 occasions where udev crashed during bootup.
> The second time carried a kernel log where the following line
> "BUG_ON(!list_empty(&entry->d_alias))"
> in d_instantiate is triggered when udev is attempting to
> create a symlink in /dev (which is tmpfs/shmem).
>
> I've tried reproducing this by doing as udev does:
> - create temporary symlink
> - move temporary symlink into place
> in a tight loop (multiple processes) while multiple
> other processes were removing the symlink in a
> tight loop.
> A third script was flushing the dentry/inode cache
> every so often using drop_caches.
> All to no avail.
>
> I've been digging around in the kernel sources,
> but I'm not sure what the d_alias field means
> and what the actual case is the BUG_ON is
> meant to catch. I'd like to be able to find a way
> to reproduce this, because so far it's happened only
> twice in 2 weeks over multiple systems doing
> many reboots in a testing setup.
> Can someone explain this to me in short?
>
> Thanks,
> Stijn

Trying resend...

Stijn
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