From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932089AbWFUNtg (ORCPT ); Wed, 21 Jun 2006 09:49:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751559AbWFUNtg (ORCPT ); Wed, 21 Jun 2006 09:49:36 -0400 Received: from hera.kernel.org ([140.211.167.34]:32428 "EHLO hera.kernel.org") by vger.kernel.org with ESMTP id S1750768AbWFUNte (ORCPT ); Wed, 21 Jun 2006 09:49:34 -0400 Date: Wed, 21 Jun 2006 10:50:15 -0300 From: Marcelo Tosatti To: Willy Tarreau Cc: Grant Coady , linux-kernel@vger.kernel.org, Al Viro Subject: Re: Linux 2.4.33-rc1 Message-ID: <20060621135015.GA620@dmt> References: <20060618223736.GA4965@1wt.eu> <20060619040152.GB2678@1wt.eu> <20060619080651.GA3273@1wt.eu> <20060619220405.GA16251@dmt> <20060619230007.GA6471@1wt.eu> <20060619234506.GA2763@dmt> <20060620222357.GA11862@1wt.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060620222357.GA11862@1wt.eu> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Willy, On Wed, Jun 21, 2006 at 12:23:57AM +0200, Willy Tarreau wrote: > On Mon, Jun 19, 2006 at 08:45:06PM -0300, Marcelo Tosatti wrote: > > > > > > ---- from here ---- > > > > > > > > > > + inode = dentry->d_inode; > > > > + if (inode) > > > > + atomic_inc(&inode->i_count); > > > > error = vfs_unlink(nd.dentry->d_inode, dentry); > > > > exit2: > > > > dput(dentry); > > > > } > > > > up(&nd.dentry->d_inode->i_sem); > > > > + if (inode) > > > > + iput(inode); > > > > > > ---- to here ---- > > > > > > I believe that nd.dentry->d_inode cannot vanish because it is protected by the > > > down(->i_sem) before and the up(->i_sem) after. Am I right or am I missing > > > something important ? > > > > Indeed it can't, but dentry->d_inode will be set to NULL by > > nfs_unlink->nfs_safe_remove->d_delete. Thus the problem. > > What puzzles me is how are we supposed to up(&nd.dentry->d_inode->i_sem) if > dentry->d_inode can become NULL ? down(&nd.dentry->d_inode->i_sem); dentry = lookup_hash(&nd.last, nd.dentry); error = vfs_unlink(nd.dentry->d_inode, dentry); ^^^^^^^ It does vfs_unlink(parent, child). The child is killed. > simply by keeping a copy of it ? I thought > that the down() protected the whole thing, but may be that's stupid anyway. It does not protect from last reference going away, which is what happens when NFS d_delete's the dentry. dentry_iput() gets called, and maybe the last reference to "struct inode" might be gone too. > I've been running rc1 without this patch for a few hours and during kernel > compiles without a problem, so I'm not sure about what to think about the > other changes which were apparently harmless too :-/ Use NFS... :) > Well, if I resume it right, we only need to merge your patch and mine and > it *should* be OK. > > BTW, I've been reviewing the PaX patch and found *at least* one patch > that should be merged (fix for oops). I'll send it separately, and it's > queued in -upstream. Merged, thanks.