Return-Path: Received: from smtp.ctxuk.citrix.com ([62.200.22.115]:28550 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754488Ab1GVOQH (ORCPT ); Fri, 22 Jul 2011 10:16:07 -0400 Subject: Re: [PATCH 08/13] net: convert drivers to paged frag API. From: Ian Campbell To: David Miller CC: "netdev@vger.kernel.org" , "linux-nfs@vger.kernel.org" , Chas Williams , In-Reply-To: <20110722.071217.607687554920673786.davem@davemloft.net> References: <1311340095.12772.57.camel@zakaz.uk.xensource.com> <1311340653-19336-8-git-send-email-ian.campbell@citrix.com> <20110722.071217.607687554920673786.davem@davemloft.net> Content-Type: text/plain; charset="UTF-8" Date: Fri, 22 Jul 2011 15:16:04 +0100 Message-ID: <1311344164.12772.78.camel@zakaz.uk.xensource.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Fri, 2011-07-22 at 15:12 +0100, David Miller wrote: > From: Ian Campbell > Date: Fri, 22 Jul 2011 14:17:28 +0100 > > > - put_dma(tx->index,eni_dev->dma,&j,(unsigned long) > > - skb_shinfo(skb)->frags[i].page + skb_shinfo(skb)->frags[i].page_offset, > > + put_dma(tx->index,eni_dev->dma,&j, > > + (unsigned long)skb_frag_address(&skb_shinfo(skb)->frags[i]), > > This is not an equivalent transformation. > > skb_frag_address() does a page_address() on the frag page, but that is > not what the code was doing here previously. > > It's possible the code was buggy, but you can't do a fix like that > amidst what is supposed to be a semantically NOP transformation. Ouch, you are absolutely right, I didn't spot that, sorry. The original code does look pretty bogus though, indexing off a struct page * like that -- CC'ing the ATM maintainer + list. Ian.