Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752738AbaDALsU (ORCPT ); Tue, 1 Apr 2014 07:48:20 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:42524 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752547AbaDALR6 (ORCPT ); Tue, 1 Apr 2014 07:17:58 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Laura Abbott , Mel Gorman , Joonsoo Kim , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 3.11 086/144] mm/compaction: break out of loop on !PageBuddy in isolate_freepages_block Date: Tue, 1 Apr 2014 12:14:50 +0100 Message-Id: <1396350948-29910-87-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1396350948-29910-1-git-send-email-luis.henriques@canonical.com> References: <1396350948-29910-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11.10.7 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Laura Abbott commit 2af120bc040c5ebcda156df6be6a66610ab6957f upstream. We received several reports of bad page state when freeing CMA pages previously allocated with alloc_contig_range: BUG: Bad page state in process Binder_A pfn:63202 page:d21130b0 count:0 mapcount:1 mapping: (null) index:0x7dfbf page flags: 0x40080068(uptodate|lru|active|swapbacked) Based on the page state, it looks like the page was still in use. The page flags do not make sense for the use case though. Further debugging showed that despite alloc_contig_range returning success, at least one page in the range still remained in the buddy allocator. There is an issue with isolate_freepages_block. In strict mode (which CMA uses), if any pages in the range cannot be isolated, isolate_freepages_block should return failure 0. The current check keeps track of the total number of isolated pages and compares against the size of the range: if (strict && nr_strict_required > total_isolated) total_isolated = 0; After taking the zone lock, if one of the pages in the range is not in the buddy allocator, we continue through the loop and do not increment total_isolated. If in the last iteration of the loop we isolate more than one page (e.g. last page needed is a higher order page), the check for total_isolated may pass and we fail to detect that a page was skipped. The fix is to bail out if the loop immediately if we are in strict mode. There's no benfit to continuing anyway since we need all pages to be isolated. Additionally, drop the error checking based on nr_strict_required and just check the pfn ranges. This matches with what isolate_freepages_range does. Signed-off-by: Laura Abbott Acked-by: Minchan Kim Cc: Mel Gorman Acked-by: Vlastimil Babka Cc: Joonsoo Kim Acked-by: Bartlomiej Zolnierkiewicz Acked-by: Michal Nazarewicz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Luis Henriques --- mm/compaction.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 9a3e351..18a90b4 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -252,7 +252,6 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, { int nr_scanned = 0, total_isolated = 0; struct page *cursor, *valid_page = NULL; - unsigned long nr_strict_required = end_pfn - blockpfn; unsigned long flags; bool locked = false; @@ -265,11 +264,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, nr_scanned++; if (!pfn_valid_within(blockpfn)) - continue; + goto isolate_fail; + if (!valid_page) valid_page = page; if (!PageBuddy(page)) - continue; + goto isolate_fail; /* * The zone lock must be held to isolate freepages. @@ -290,12 +290,10 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, /* Recheck this is a buddy page under lock */ if (!PageBuddy(page)) - continue; + goto isolate_fail; /* Found a free page, break it into order-0 pages */ isolated = split_free_page(page); - if (!isolated && strict) - break; total_isolated += isolated; for (i = 0; i < isolated; i++) { list_add(&page->lru, freelist); @@ -306,7 +304,15 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, if (isolated) { blockpfn += isolated - 1; cursor += isolated - 1; + continue; } + +isolate_fail: + if (strict) + break; + else + continue; + } trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated); @@ -316,7 +322,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, * pages requested were isolated. If there were any failures, 0 is * returned and CMA will fail. */ - if (strict && nr_strict_required > total_isolated) + if (strict && blockpfn < end_pfn) total_isolated = 0; if (locked) -- 1.9.1 -- 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/