From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [PATCH] proc: revalidate dentry returned by proc_pid_follow_link Date: Fri, 6 Nov 2009 20:36:01 +0000 Message-ID: <20091106203601.GD27751@shareable.org> References: <1257513594-31071-1-git-send-email-jlayton@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, adobriyan@gmail.com, viro@ZenIV.linux.org.uk To: Jeff Layton Return-path: In-Reply-To: <1257513594-31071-1-git-send-email-jlayton@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Jeff Layton wrote: > The problem here is that this makes that code shortcut any lookup or > revalidation of the dentry. In general, this isn't a problem -- in most > cases the dentry is known to be good. It is a problem however for NFSv4. > If this symlink is followed on an open operation no actual open call > occurs and the open state isn't properly established. This causes > problems when we later try to use this file descriptor for actual > operations. As NFS uses open() as a kind of fcntl-lock barrier, I can see it's important to do _something_ on new opens, rather than just cloning most of the file descriptor. > This patch takes a minimalist approach to fixing this by making the > /proc/pid follow_link routine revalidate the dentry before returning it. What happens if the file descriptor you are re-opening is for a file which has been deleted. Does it still have a revalidatable dentry? -- Jamie