From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 30 Sep 2006 11:47:48 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH] Get rid of zone_table V2 In-Reply-To: <451A6034.20305@shadowen.org> Message-ID: References: <20060924030643.e57f700c.akpm@osdl.org> <20060927021934.9461b867.akpm@osdl.org> <451A6034.20305@shadowen.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andy Whitcroft Cc: Andrew Morton , linux-mm@kvack.org, Dave Hansen List-ID: There is still a problem after Andy's patch in connection with Optional ZONE DMA that I pointed out earlier. If we only have a single zone then ZONEID_PGSHIFT == 0. This is fine for the non NUMA case in which we have only a single zone and ZONEID_MASK == 0 too. page_zone_id() will always be 0. In the NUMA case we still have one zone per node. Thus we need to have a correct ZONEID_PGSHIFT in order to isolate the node number from page flags. Right now we take NODES_SHIFT bits starting from 0! I am not exactly sure how to fix that the right way given the complex nested macros. Andy may know. The following patch checks for that condition. We can only allow ZONEID_PGSHIFT to be zero if the ZONEID_MASK is also zero. (We cannot check that with an #if because ZONEID_SHIFT contains a "sizeof(...)" element) Signed-off-by: Christoph Lameter Index: linux-2.6.18-mm2/include/linux/mm.h =================================================================== --- linux-2.6.18-mm2.orig/include/linux/mm.h 2006-09-30 13:22:27.732989275 -0500 +++ linux-2.6.18-mm2/include/linux/mm.h 2006-09-30 13:23:06.604463587 -0500 @@ -447,6 +447,7 @@ static inline enum zone_type page_zonenu */ static inline int page_zone_id(struct page *page) { + BUG_ON(ZONEID_PGSHIFT == 0 && ZONEID_MASK); return (page->flags >> ZONEID_PGSHIFT) & ZONEID_MASK; } -- 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/ . Don't email: email@kvack.org