[PATCH 3.12 57/84] vmscan: fix increasing nr_isolated incurred by putback unevictable pages

From: Jiri Slaby
Date: Fri Oct 02 2015 - 09:26:00 EST


From: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit c54839a722a02818677bcabe57e957f0ce4f841d upstream.

reclaim_clean_pages_from_list() assumes that shrink_page_list() returns
number of pages removed from the candidate list. But shrink_page_list()
puts back mlocked pages without passing it to caller and without
counting as nr_reclaimed. This increases nr_isolated.

To fix this, this patch changes shrink_page_list() to pass unevictable
pages back to caller. Caller will take care those pages.

Minchan said:

It fixes two issues.

1. With unevictable page, cma_alloc will be successful.

Exactly speaking, cma_alloc of current kernel will fail due to
unevictable pages.

2. fix leaking of NR_ISOLATED counter of vmstat

With it, too_many_isolated works. Otherwise, it could make hang until
the process get SIGKILL.

Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
mm/vmscan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 04c33d5fb079..6dc33d9dc2cf 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1087,7 +1087,7 @@ cull_mlocked:
if (PageSwapCache(page))
try_to_free_swap(page);
unlock_page(page);
- putback_lru_page(page);
+ list_add(&page->lru, &ret_pages);
continue;

activate_locked:
--
2.6.0

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