From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH] [8/18] BKL-removal: Remove BKL from remote_llseek Date: Sun, 27 Jan 2008 21:13:45 -0800 Message-ID: <20080127211345.6e73fa0b.akpm@linux-foundation.org> References: <20080127317.043953000@suse.de> <200801280358.14024.ak@suse.de> <1201493589.8132.7.camel@heimdal.trondhjem.org> <200801280538.25345.ak@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Trond Myklebust , Steve French , swhiteho@redhat.com, sfrench@samba.org, vandrove@vc.cvut.cz, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Andi Kleen Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:35119 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750750AbYA1FQE (ORCPT ); Mon, 28 Jan 2008 00:16:04 -0500 In-Reply-To: <200801280538.25345.ak@suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 28 Jan 2008 05:38:25 +0100 Andi Kleen wrote: > On Monday 28 January 2008 05:13:09 Trond Myklebust wrote: > > > > On Mon, 2008-01-28 at 03:58 +0100, Andi Kleen wrote: > > > The problem is that it's not a race in who gets to do its thing first, but a > > > parallel reader can actually see a corrupted value from the two independent > > > words on 32bit (e.g. during a 4GB). And this could actually completely corrupt > > > f_pos when it happens with two racing relative seeks or read/write()s > > > > > > I would consider that a bug. > > > > I disagree. The corruption occurs because this isn't a situation that is > > allowed by either POSIX or SUSv2/v3. Exactly what spec are you referring > > to here? > > No specific spec, just general quality of implementation. I completely agree. If one thread writes A and another writes B then the kernel should record either A or B, not ((A & 0xffffffff00000000) | (B & 0xffffffff))