From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id 975A16B019D for ; Fri, 14 Oct 2011 02:56:07 -0400 (EDT) Subject: Re: [PATCH] mm: add a "struct page_frag" type containing a page, offset and length From: Ian Campbell In-Reply-To: <20111013142201.355f9afc.akpm@linux-foundation.org> References: <20111013.163708.1319779926961023813.davem@davemloft.net> <20111013.165148.64222593458932960.davem@davemloft.net> <20111013142201.355f9afc.akpm@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1" Date: Fri, 14 Oct 2011 07:56:02 +0100 Message-ID: <1318575363.11016.8.camel@dagon.hellion.org.uk> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: David Miller , "rientjes@google.com" , "linux-kernel@vger.kernel.org" , "hch@infradead.org" , "jaxboe@fusionio.com" , "linux-mm@kvack.org" On Thu, 2011-10-13 at 22:22 +0100, Andrew Morton wrote: > Looks OK to me. I'm surprised we don't already have such a thing. > > Review comments: > > > > +struct page_frag { > > + struct page *page; > > +#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536) > > It does add risk that people will add compile warnings and bugs by > failing to consider or test the other case. > > We could reduce that risk by doing > > #if (PAGE_SIZE >= 65536) > > but then the 32-bit version would hardly ever be tested at all. Indeed. The first variant has the benefit that most 32-bit arches will test one case and most 64-bit ones the other. Perhaps the need to keep this struct small is not so acute as it is for the skb_frag_t I nicked it from and just using __u32 unconditionally is sufficient? > > > + __u32 page_offset; > > I suggest this be called simply "offset". ACK. Thanks, Ian. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org