Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751355AbaDQX2Y (ORCPT ); Thu, 17 Apr 2014 19:28:24 -0400 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:52797 "EHLO lgemrelse7q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750736AbaDQX2W (ORCPT ); Thu, 17 Apr 2014 19:28:22 -0400 X-Original-SENDERIP: 10.177.220.169 X-Original-MAILFROM: minchan@kernel.org Date: Fri, 18 Apr 2014 08:29:10 +0900 From: Minchan Kim To: Vlastimil Babka Cc: Andrew Morton , Joonsoo Kim , Bartlomiej Zolnierkiewicz , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mel Gorman , Yong-Taek Lee , KOSAKI Motohiro , Marek Szyprowski , Hugh Dickins , Rik van Riel , Michal Nazarewicz Subject: Re: [PATCH 1/2] mm/page_alloc: prevent MIGRATE_RESERVE pages from being misplaced Message-ID: <20140417232910.GB7178@bbox> References: <533D8015.1000106@suse.cz> <1396539618-31362-1-git-send-email-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1396539618-31362-1-git-send-email-vbabka@suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 03, 2014 at 05:40:17PM +0200, Vlastimil Babka wrote: > For the MIGRATE_RESERVE pages, it is important they do not get misplaced > on free_list of other migratetype, otherwise the whole MIGRATE_RESERVE > pageblock might be changed to other migratetype in try_to_steal_freepages(). > > Currently, it is however possible for this to happen when MIGRATE_RESERVE > page is allocated on pcplist through rmqueue_bulk() as a fallback for other > desired migratetype, and then later freed back through free_pcppages_bulk() > without being actually used. This happens because free_pcppages_bulk() uses > get_freepage_migratetype() to choose the free_list, and rmqueue_bulk() calls > set_freepage_migratetype() with the *desired* migratetype and not the page's > original MIGRATE_RESERVE migratetype. > > This patch fixes the problem by moving the call to set_freepage_migratetype() > from rmqueue_bulk() down to __rmqueue_smallest() and __rmqueue_fallback() where > the actual page's migratetype (e.g. from which free_list the page is taken > from) is used. Note that this migratetype might be different from the > pageblock's migratetype due to freepage stealing decisions. This is OK, as page > stealing never uses MIGRATE_RESERVE as a fallback, and also takes care to leave > all MIGRATE_CMA pages on the correct freelist. > > Therefore, as an additional benefit, the call to get_pageblock_migratetype() > from rmqueue_bulk() when CMA is enabled, can be removed completely. This relies > on the fact that MIGRATE_CMA pageblocks are created only during system init, > and the above. The related is_migrate_isolate() check is also unnecessary, as > memory isolation has other ways to move pages between freelists, and drain > pcp lists containing pages that should be isolated. > The buffered_rmqueue() can also benefit from calling get_freepage_migratetype() > instead of get_pageblock_migratetype(). Nice description. > > A separate patch will add VM_BUG_ON checks for the invariant that for > MIGRATE_RESERVE and MIGRATE_CMA pageblocks, freepage_migratetype must equal to > pageblock_migratetype so that these pages always go to the correct free_list. > > Reported-by: Yong-Taek Lee > Reported-by: Bartlomiej Zolnierkiewicz > Suggested-by: Joonsoo Kim > Suggested-by: Mel Gorman > Cc: Minchan Kim > Cc: KOSAKI Motohiro > Cc: Marek Szyprowski > Cc: Hugh Dickins > Cc: Rik van Riel > Cc: Michal Nazarewicz > Signed-off-by: Vlastimil Babka Acked-by: Minchan Kim -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/