Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269882AbUJHBSo (ORCPT ); Thu, 7 Oct 2004 21:18:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267953AbUJGWz2 (ORCPT ); Thu, 7 Oct 2004 18:55:28 -0400 Received: from mailhost.tue.nl ([131.155.2.7]:10763 "EHLO mailhost.tue.nl") by vger.kernel.org with ESMTP id S269875AbUJGWeg (ORCPT ); Thu, 7 Oct 2004 18:34:36 -0400 Date: Fri, 8 Oct 2004 00:34:34 +0200 From: Andries Brouwer To: Chris Wedgwood Cc: Andries Brouwer , Alan Cox , Linux Kernel Mailing List Subject: Re: mmap specification - was: ... select specification Message-ID: <20041007223434.GB7047@pclin040.win.tue.nl> References: <4164EBF1.3000802@nortelnetworks.com> <001601c4ac72$19932760$161b14ac@boromir> <001c01c4ac76$fb9fd190$161b14ac@boromir> <1097156727.31753.44.camel@localhost.localdomain> <001f01c4ac8b$35849710$161b14ac@boromir> <1097160628.31614.68.camel@localhost.localdomain> <20041007215834.GA7047@pclin040.win.tue.nl> <20041007221745.GA16597@taniwha.stupidest.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041007221745.GA16597@taniwha.stupidest.org> User-Agent: Mutt/1.4.1i X-Spam-DCC: : Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1254 Lines: 30 On Thu, Oct 07, 2004 at 03:17:45PM -0700, Chris Wedgwood wrote: > On Thu, Oct 07, 2004 at 11:58:34PM +0200, Andries Brouwer wrote: > > > [I read this as follows: If you mmap a file with MAP_SHARED and > > modify the memory at an address so far beyond EOF that it is not in > > a page containing stuff from the file, then you get a SIGBUS. -- > > Linux does this. Also, that if you modify the memory at an address > > beyond EOF, then the file is not modified. -- Again Linux does > > this.] > > consider mmaping a 1-byte file ... you can modify bytes 0..4095. > bytes 1..4095 shouldn't be recorded to disk ideally > > at one point one fs did actually store this data and it caused cpp > problems (it would expect to see zeroes and where it didn't it got > upset) Is this an answer? Or an anecdote? [You seem to say anecdotically that at one point in time Linux mmap was not POSIX compliant, and problems arose. Alan on the other hand seems to say that POSIX comes with ridiculous requirements.] Andries - 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/