Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756185AbZDPVqR (ORCPT ); Thu, 16 Apr 2009 17:46:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754175AbZDPVp7 (ORCPT ); Thu, 16 Apr 2009 17:45:59 -0400 Received: from mail.fieldses.org ([141.211.133.115]:52914 "EHLO pickle.fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754134AbZDPVp6 (ORCPT ); Thu, 16 Apr 2009 17:45:58 -0400 Date: Thu, 16 Apr 2009 17:45:45 -0400 To: David Woodhouse Cc: "hooanon05@yahoo.co.jp" , Al Viro , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" Subject: Re: Q: NFSD readdir in linux-2.6.28 Message-ID: <20090416214545.GA2237@fieldses.org> References: <8036.1237474444@jrobl> <1237475837.16359.106.camel@macbook.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1237475837.16359.106.camel@macbook.infradead.org> User-Agent: Mutt/1.5.18 (2008-05-17) From: "J. Bruce Fields" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1621 Lines: 38 On Thu, Mar 19, 2009 at 03:17:17PM +0000, David Woodhouse wrote: > On Thu, 2009-03-19 at 14:54 +0000, hooanon05@yahoo.co.jp wrote: > > > > Hello David and Al, > > I have a question about NFSD readdir. > > > > By the commit 14f7dd632011bb89c035722edd6ea0d90ca6b078 > > "[PATCH] Copy XFS readdir hack into nfsd code", nfsd_buffered_filldir() > > was introduced and nfs3svc_encode_entry_plus() (the 'func' parameter) is > > not called from vfs_readdir(). > > > > In 2.6.27, when nfs3svc_encode_entry_plus() calls lookup_one_len(), the > > i_mutex lock was acquired by vfs_readdir() and it was not a problem. > > > > After the commit (above), nfsd_readdir/nfsd_buffered_readdir/vfs_readdir > > calls nfsd_buffered_filldir(), and nfs3svc_encode_entry_plus() is called > > later. > > In this sequence, lookup_one_len() is called without i_mutex held. > > > > Isn't it a problem? > > Yes, well spotted. It didn't matter when the buffered readdir() was > purely internal to XFS, because it didn't matter there that we called > ->lookup() without i_mutex set. But now we're exposing arbitrary file > systems to it, we need to make sure we follow the locking rules. > > I _think_ it's sufficient to make the affected callers of > lookup_one_len() lock the parent's i_mutex for themselves before calling > it. I'll take a closer look... Yipes--is this problem still here? --b. -- 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/