linux-kernel - [PATCH 3.16 106/114] mm/balloon_compaction: fix deflation when compaction is disabled

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Date:	Mon, 13 Jun 2016 19:36:37 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Konstantin Khlebnikov" <k.khlebnikov@...sung.com>,
	"Matt Mullins" <mmullins@...x.us>,
	"jian wang" <wangjian@...edance.com>,
	"Jiri Kosina" <jkosina@...e.cz>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 106/114] mm/balloon_compaction: fix deflation when
 compaction is disabled

3.16.36-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Konstantin Khlebnikov <k.khlebnikov@...sung.com>

commit 4d88e6f7d5ffc84e6094a47925870f4a130555c2 upstream.

If CONFIG_BALLOON_COMPACTION=n balloon_page_insert() does not link pages
with balloon and doesn't set PagePrivate flag, as a result
balloon_page_dequeue() cannot get any pages because it thinks that all
of them are isolated.  Without balloon compaction nobody can isolate
ballooned pages.  It's safe to remove this check.

Fixes: d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management").
Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@...sung.com>
Reported-by: Matt Mullins <mmullins@...x.us>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: jian wang <wangjian@...edance.com>
---
 mm/balloon_compaction.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -94,11 +94,13 @@ struct page *balloon_page_dequeue(struct
 		 * to be released by the balloon driver.
 		 */
 		if (trylock_page(page)) {
+#ifdef CONFIG_BALLOON_COMPACTION
 			if (!PagePrivate(page)) {
 				/* raced with isolation */
 				unlock_page(page);
 				continue;
 			}
+#endif
 			balloon_page_delete(page);
 			unlock_page(page);
 			dequeued_page = true;