From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933217AbXCRWkT (ORCPT ); Sun, 18 Mar 2007 18:40:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933233AbXCRWkS (ORCPT ); Sun, 18 Mar 2007 18:40:18 -0400 Received: from noname.neutralserver.com ([70.84.186.210]:51456 "EHLO noname.neutralserver.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S933217AbXCRWkR (ORCPT ); Sun, 18 Mar 2007 18:40:17 -0400 Date: Mon, 19 Mar 2007 00:40:10 +0200 From: Dan Aloni To: David Miller Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH] tcp_sendpage(): fix broken page iteration Message-ID: <20070318224009.GA15407@localdomain> References: <20070318124346.GA6396@localdomain> <20070318.144927.78708843.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070318.144927.78708843.davem@davemloft.net> User-Agent: Mutt/1.5.13 (2006-08-11) X-PopBeforeSMTPSenders: da-x@monatomic.org X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - noname.neutralserver.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - monatomic.org X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 18, 2007 at 02:49:27PM -0700, David Miller wrote: > From: Dan Aloni > Date: Sun, 18 Mar 2007 14:43:46 +0200 > > > do_tcp_sendpages() should not iterate 'pages' as an array since > > it is not an array of 'struct page *', but a pointer to a single > > entity of 'struct page *' passed on the stack as a parameter to > > tcp_send_page() (hence it would crash if poffset + psize > PAGE_SIZE, > > because pages[1] and beyond most probably not constitutes a valid > > 'struct page *'). > > do_tcp_sendpages() should never get passed poffset+psize>PAGE_SIZE, > that would be a bug. Oh, then the name of that function was quite misleading... Anyway, I thought it would make a valid case for a situation where you have a kmalloc'ed buffer that happens to cross a page boundery and you want to call ->sendpage() to send it over using network DMA. As I see it, with this constraint you either call sendpage twice or you use kernel_sendmsg(), I am not sure which would me more efficient - I guess it depends on psize. I wish there was a better interface than sendpage that would have factored it in... Thanks anyway for the heads up. -- Dan Aloni XIV LTD, http://www.xivstorage.com da-x (at) monatomic.org, dan (at) xiv.co.il