Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758616AbYJHCwW (ORCPT ); Tue, 7 Oct 2008 22:52:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756190AbYJHCwN (ORCPT ); Tue, 7 Oct 2008 22:52:13 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:38435 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756071AbYJHCwM (ORCPT ); Tue, 7 Oct 2008 22:52:12 -0400 Date: Tue, 7 Oct 2008 20:52:09 -0600 From: Matthew Wilcox To: Nick Piggin Cc: Peter Zijlstra , torvalds@linux-foundation.org, Andrew Morton , Andi Kleen , Hisashi Hifumi , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Aneesh Kumar K.V" , "Theodore Ts'o" Subject: Re: [RESEND] [PATCH] VFS: make file->f_pos access atomic on 32bit arch Message-ID: <20081008025209.GO25780@parisc-linux.org> References: <6.0.0.20.2.20081007140438.0580f110@172.19.0.2> <20081007105056.16d9e785.akpm@linux-foundation.org> <1223405963.26330.83.camel@lappy.programming.kicks-ass.net> <200810081335.44576.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200810081335.44576.nickpiggin@yahoo.com.au> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1269 Lines: 26 On Wed, Oct 08, 2008 at 01:35:44PM +1100, Nick Piggin wrote: > Right you are. That's the fundamental question. The actual details of > the fix and how likely the race is don't really matter until we > answer the first question (except to say that the "fix" is never going > to be free). > > We've lasted this long with the current semantics. So the natural > reaction to anything that strengthens the semantics now is "why?". If > we do that then we can basically never return to the weaker semantics. > So there had better be a really good reason. And it's worth saying that letter-of-the-standard arguments aren't necessarily enough. Linux does not honour the POSIX guarantee that writes are atomic (if they cross page boundaries, it's not certain). This seems like even more of a corner case to me. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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/