From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Aloni Subject: Re: [PATCH] tcp_sendpage(): fix broken page iteration Date: Mon, 19 Mar 2007 00:40:10 +0200 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 Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: David Miller Return-path: 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 Content-Disposition: inline In-Reply-To: <20070318.144927.78708843.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.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