linux-kernel - [Q] missing ->d_delete() in shrink_dcache_for

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Date:	Tue, 31 Oct 2006 16:24:36 +0300
From:	Vasily Averin <vvs@...ru>
To:	devel@...nvz.org, David Howells <dhowells@...hat.com>
CC:	Neil Brown <neilb@...e.de>, Jan Blunck <jblunck@...e.de>,
	Olaf Hering <olh@...e.de>, Balbir Singh <balbir@...ibm.com>,
	Kirill Korotaev <dev@...nvz.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>
Subject: [Q] missing ->d_delete() in shrink_dcache_for_umount()?

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@...b144ecSF1rYskg3q-SeR2vf88zg
> # ChangeSet
> #   2006/06/22 15:05:57-07:00 neilb@...e.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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