From: Konstantin Khlebnikov <[email protected]>
Subject: mm/balloon_compaction: fix deflation when compaction is disabled

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: d6d86c0a7f8ddc ("mm/balloon_compaction: redesign ballooned pages 
management").
Signed-off-by: Konstantin Khlebnikov <[email protected]>
Reported-by: Matt Mullins <[email protected]>
Cc: <[email protected]>    [3.17]
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/balloon_compaction.c |    2 ++
 1 file changed, 2 insertions(+)

diff -puN 
mm/balloon_compaction.c~mm-balloon_compaction-fix-deflation-when-compaction-is-disabled
 mm/balloon_compaction.c
--- 
a/mm/balloon_compaction.c~mm-balloon_compaction-fix-deflation-when-compaction-is-disabled
+++ a/mm/balloon_compaction.c
@@ -68,11 +68,13 @@ 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
                        spin_lock_irqsave(&b_dev_info->pages_lock, flags);
                        balloon_page_delete(page);
                        __count_vm_event(BALLOON_DEFLATE);
_
--
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