Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751915AbXBVVaW (ORCPT ); Thu, 22 Feb 2007 16:30:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751916AbXBVVaV (ORCPT ); Thu, 22 Feb 2007 16:30:21 -0500 Received: from mail-gw3.sa.ew.hu ([212.108.200.82]:57385 "EHLO mail-gw3.sa.ew.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751915AbXBVVaU (ORCPT ); Thu, 22 Feb 2007 16:30:20 -0500 To: trond.myklebust@fys.uio.no CC: miklos@szeredi.hu, staubach@redhat.com, akpm@linux-foundation.org, hugh@veritas.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org In-reply-to: <1172178253.6382.12.camel@heimdal.trondhjem.org> (message from Trond Myklebust on Thu, 22 Feb 2007 16:04:13 -0500) Subject: Re: [PATCH] update ctime and mtime for mmaped write References: <20070221202615.a0a167f4.akpm@linux-foundation.org> <45DDD55F.4060106@redhat.com> <45DDF9C1.4090003@redhat.com> <1172178253.6382.12.camel@heimdal.trondhjem.org> Message-Id: From: Miklos Szeredi Date: Thu, 22 Feb 2007 22:28:59 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1439 Lines: 36 > > > This still does not address the situation where a file is 'permanently' > > > mmap'd, does it? > > > > So? If application doesn't do msync, then the file times won't be > > updated. That's allowed by the standard, and so portable applications > > will have to call msync. > > It is allowed, but it is clearly not useful behaviour. Nowhere is it set > in stone that we should be implementing just the minimum allowed. You're right. In theory, at least. But in practice I don't think this matters. Show me an application that writes to a shared mapping then doesn't call either msync or munmap and doesn't even exit. If there were lot of these apps, then this bug would have been fixed lots of years earlier. In fact there are _very_ few apps writing to shared mappings at all. Applications should be encouraged to call msync(MS_ASYNC) because: - it's very fast (basically a no-op) on recent linux kernels - it's the only portable way to guarantee, that the data you written will _ever_ hit the disk. There's really no downside to using msync(MS_ASYNC) in your application, so making an effort to support applications that don't do this is stupid, IMO. Thanks, Miklos - 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/