To: ebiederm@xmission.com (Eric W. Biederman)
CC: miklos@szeredi.hu, jlayton@redhat.com, linux-fsdevel@vger.kernel.org,
       linux-kernel@vger.kernel.org, jamie@shareable.org, pavel@ucw.cz,
       viro@ZenIV.linux.org.uk, duaneg@dghda.com
In-reply-to: <m1tyw8nwgk.fsf@fess.ebiederm.org>
Subject: Re: [PATCH 2/2] vfs: force reval on dentry of bind mounted files on FS_REVAL_DOT filesystems
References: <1259783983-26884-1-git-send-email-jlayton@redhat.com>
	<1259783983-26884-3-git-send-email-jlayton@redhat.com>
	<E1NG9OV-0002g5-3D@pomaz-ex.szeredi.hu> <m1tyw8nwgk.fsf@fess.ebiederm.org>
Message-Id: <E1NG9iu-0002jR-1r@pomaz-ex.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Thu, 03 Dec 2009 12:19:48 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 880
Lines: 20

On Thu, 03 Dec 2009, Eric W. Biederman wrote:
> > The only worry I have is that this adds an extra branch in a very hot
> > codepath (do_lookup).  An error can't be returned, as you note, and
> > for bind mounted directories d_invalidate() will not succeed: the
> > directory is busy, it's referenced by the mount. 
> 
> Not true.  d_mountpoint is false, so d_invalidate can succeed.

Have a look at the code.  d_invalidate() doesn't check for a
mountpoint, it checks the refcount.  It needs to keep the directory
dentry hashed if it's in any way reachable other than from the cache
(file descriptor, cwd, mount, etc).

Thanks,
Miklos
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