From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754738Ab0CYO1T (ORCPT ); Thu, 25 Mar 2010 10:27:19 -0400 Received: from daytona.panasas.com ([67.152.220.89]:64607 "EHLO daytona.int.panasas.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752649Ab0CYO1R (ORCPT ); Thu, 25 Mar 2010 10:27:17 -0400 Message-ID: <4BAB72C1.6090002@panasas.com> Date: Thu, 25 Mar 2010 16:27:13 +0200 From: Boaz Harrosh User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3 MIME-Version: 1.0 To: Al Viro CC: Benny Halevy , linux-fsdevel , "J. Bruce Fields" , pNFS Mailing List , linux-kernel , Doug Nazar Subject: Re: [pnfs] [GIT BISECT] first bad commit: 1f36f774 Switch !O_CREAT case to use of do_last() References: <20100324185604.GT30031@ZenIV.linux.org.uk> <4BAB2F5A.30409@panasas.com> <20100325101231.GU30031@ZenIV.linux.org.uk> <20100325105406.GW30031@ZenIV.linux.org.uk> <4BAB51F5.609@panasas.com> <4BAB54B0.3080109@panasas.com> <20100325130610.GZ30031@ZenIV.linux.org.uk> <4BAB656E.8020204@panasas.com> <20100325133746.GA30031@ZenIV.linux.org.uk> <4BAB6911.5020009@panasas.com> <20100325140457.GB30031@ZenIV.linux.org.uk> In-Reply-To: <20100325140457.GB30031@ZenIV.linux.org.uk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 25 Mar 2010 14:27:16.0469 (UTC) FILETIME=[44DE4A50:01CACC27] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/25/2010 04:04 PM, Al Viro wrote: > On Thu, Mar 25, 2010 at 03:45:53PM +0200, Boaz Harrosh wrote: >>> Does open() of directory _without_ O_DIRECTORY work in e.g. vanilla 2.6.33? >>> It certainly does for local filesystems and it does for NFSv3; does it work >>> for NFSv4? >> >> In my tests. Every thing is the same safe the client with the above change. >> >> So I guess NFSv4 does something different when asked for directory lookup >> as opposed to files lookup. I guess there is something added/removed to >> the compound depending on that flag. But I wouldn't know, I am not familiar >> with this code. NFSv4 someone? > > OK, what happens if you do the following: > > mount the same fs from two clients > on one client: > mkdir /mnt/weird_name_69 > on another: > echo 'main() {open("/mnt/weird_name_69", 0);}' >/tmp/a.c > gcc /tmp/a.c > strace ./a.out > ls -l /mnt/weird_name_69 > strace ./a.out > > Will the first strace show EISDIR and the second succeed? > > From my reading of that code (2.6.33, before all that stuff got merged), > we have different behaviour depending on which codepath do we hit. > If we go through ->d_revalidate(), it sees that it's not S_ISREG() and > doesn't try to play with atomic open. If we go through ->lookup(), we > tell the server to open it, and when it tells us to bugger off (it's a > directory, NFSv4 doesn't support atomic open for those), -EISDIR is > passed to caller. Which leads to open() failing. > > It definitely looks like a bug. Masked by O_DIRECTORY in 2.6.33. Bug > in fs/namei.c patch has exposed that crap both for O_DIRECTORY and !O_DIRECTORY > cases. > > So immediate fix will need to be along the lines of "add LOOKUP_DIRECTORY > even on the last step if we have *want_dir" (and I'd probably get rid of > want_dir then and just abuse nd->flags), but there's a real NFS bug as > well. NFS bug, you mean by not being consistent when opening a directory from cache or when having to fetch it for the first time? I guess... But I still think it is a problem that the application, git in this case, did an open(,O_DIRECTORY...) and because of code reuse some low-level did not see that flag, relaying on the fact that in most systems they don't care. The nd->flags things looks like the right thing to me. And about the NFS thing, let misbehaving applications byte there own bullets. But a good app like git, does put an O_DIRECTORY on the directory open, and therefore will receive consistent results, right? Please push a fix, meanwhile I'm running with this one, but I will need it in linux-next later. Thanks for everything Boaz