Date: Tue, 14 Apr 2015 13:44:29 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: I_CLEAR bug while shrinking dcache
Message-ID: <20150414124428.GW889@ZenIV.linux.org.uk>
References: <20150414081254.GD14691@type.youpi.perso.aquilenet.fr>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20150414081254.GD14691@type.youpi.perso.aquilenet.fr>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1022
Lines: 25

On Tue, Apr 14, 2015 at 10:12:54AM +0200, Samuel Thibault wrote:

> So it seems that shrink_dentry_list was trying to kill an inode which
> already has I_CLEAR.  I'll be trying the attached patch in the next
> days.

That patch is just papering over the problem.  What you have is a dentry
with ->d_inode pointing to something with I_CLEAR set.

So either
	* dentry has already been through __dentry_kill()
	* or you have live dentry with ->d_inode somehow not contributing
to refcount of ->d_inode
	* or you have an inode with positive refcount and I_CLEAR set.

The first variant can happen, but in that case it should have had
DCACHE_DENTRY_KILLED set by said __dentry_kill() and skipped.  The other
two are clear inode refcounting bugs.

Do you have a reproducer for that?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/