Message-ID: <45474E94.7030506@sw.ru>
Date: Tue, 31 Oct 2006 16:24:36 +0300
From: Vasily Averin <vvs@sw.ru>
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To: devel@openvz.org, David Howells <dhowells@redhat.com>
CC: Neil Brown <neilb@suse.de>, Jan Blunck <jblunck@suse.de>,
       Olaf Hering <olh@suse.de>, Balbir Singh <balbir@in.ibm.com>,
       Kirill Korotaev <dev@openvz.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
Subject: [Q] missing ->d_delete() in shrink_dcache_for_umount()?
References: <453F58FB.4050407@sw.ru>
In-Reply-To: <453F58FB.4050407@sw.ru>
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David,

Vasily Averin wrote:
> Hello folks,
> 
> I would like to ask you clarify me one question in the the following patch:
> http://linux.bkbits.net:8080/linux-2.6/gnupatch@449b144ecSF1rYskg3q-SeR2vf88zg
> # ChangeSet
> #   2006/06/22 15:05:57-07:00 neilb@suse.de
> #   [PATCH] Fix dcache race during umount
> 
> #   If prune_dcache finds a dentry that it cannot free, it leaves it where it
> #   is (at the tail of the list) and exits, on the assumption that some other
> #   thread will be removing that dentry soon.

It looks like I've noticed yet one suspicious place in your patch. As far as I
see you have removed dput(root) call in shrink_dcache_for_umount() function.
However I would note that dput contains ->d_delete() call that is missing in
your function:

if (dentry->d_op && dentry->d_op->d_delete) {
	if (dentry->d_op->d_delete(dentry))
		goto unhash_it;

I'm not sure but it seems to me some (probably out-of-tree) filesystems can do
something useful in this place.

Thank you,
	Vasily Averin
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