Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932750AbaJGX0l (ORCPT ); Tue, 7 Oct 2014 19:26:41 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39740 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932310AbaJGXUK (ORCPT ); Tue, 7 Oct 2014 19:20:10 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Joonsoo Kim , Vlastimil Babka , Mel Gorman , Rik van Riel , Andrew Morton , Linus Torvalds Subject: [PATCH 3.14 25/37] mm/compaction: change the timing to check to drop the spinlock Date: Tue, 7 Oct 2014 16:19:42 -0700 Message-Id: <20141007231827.834414291@linuxfoundation.org> X-Mailer: git-send-email 2.1.2 In-Reply-To: <20141007231827.043235686@linuxfoundation.org> References: <20141007231827.043235686@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joonsoo Kim commit be1aa03b973c7dcdc576f3503f7a60429825c35d upstream. It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th pfn page. This may results in below situation while isolating migratepage. 1. try isolate 0x0 ~ 0x200 pfn pages. 2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop the spinlock. 3. Then, to complete isolating, retry to aquire the lock. I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking the criteria about dropping the lock. This has no harm 0x0 pfn, because, at this time, locked variable would be false. Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka Cc: Mel Gorman Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Mel Gorman Signed-off-by: Greg Kroah-Hartman --- mm/compaction.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/compaction.c +++ b/mm/compaction.c @@ -487,7 +487,7 @@ isolate_migratepages_range(struct zone * cond_resched(); for (; low_pfn < end_pfn; low_pfn++) { /* give a chance to irqs before checking need_resched() */ - if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) { + if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) { if (should_release_lock(&zone->lru_lock)) { spin_unlock_irqrestore(&zone->lru_lock, flags); locked = false; -- 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/