linux-kernel - [patch -mm 1/2] mm/compaction: split freepages without holding the zone lock fix

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Date:	Tue, 21 Jun 2016 14:47:54 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
cc:	Mel Gorman <mgorman@...hsingularity.net>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [patch -mm 1/2] mm/compaction: split freepages without holding the
 zone lock fix

If __isolate_free_page() fails, avoid adding to freelist so we don't call
map_pages() with it.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 Fix for mm-compaction-split-freepages-without-holding-the-zone-lock.patch in
 -mm.

 mm/compaction.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -494,24 +494,21 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
 
 		/* Found a free page, will break it into order-0 pages */
 		order = page_order(page);
-		isolated = __isolate_free_page(page, page_order(page));
+		isolated = __isolate_free_page(page, order);
+		if (!isolated)
+			goto isolate_fail;
 		set_page_private(page, order);
 		total_isolated += isolated;
 		list_add_tail(&page->lru, freelist);
-
-		/* If a page was split, advance to the end of it */
-		if (isolated) {
-			cc->nr_freepages += isolated;
-			if (!strict &&
-				cc->nr_migratepages <= cc->nr_freepages) {
-				blockpfn += isolated;
-				break;
-			}
-
-			blockpfn += isolated - 1;
-			cursor += isolated - 1;
-			continue;
+		cc->nr_freepages += isolated;
+		if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
+			blockpfn += isolated;
+			break;
 		}
+		/* Advance to end of split page */
+		blockpfn += isolated - 1;
+		cursor += isolated - 1;
+		continue;
 
 isolate_fail:
 		if (strict)
@@ -622,7 +619,7 @@ isolate_freepages_range(struct compact_control *cc,
 		 */
 	}
 
-	/* split_free_page does not map the pages */
+	/* __isolate_free_page() does not map the pages */
 	map_pages(&freelist);
 
 	if (pfn < end_pfn) {
@@ -1124,7 +1121,7 @@ static void isolate_freepages(struct compact_control *cc)
 		}
 	}
 
-	/* split_free_page does not map the pages */
+	/* __isolate_free_page() does not map the pages */
 	map_pages(freelist);
 
 	/*