[PATCH 1/8] mm: vmscan: Block kswapd if it is encountering pages under writeback -fix

[Mel Gorman]

The patch "mm: vmscan: Block kswapd if it is encountering pages
under writeback" stalls in congestion_wait it encounters a page under
writeback that is marked for immediate reclaim. Initially this was a
wait_on_page_writeback() but after the switch to congestion_wait(),
there is no guarantee the page has completed writeback and it can
be placed on a list for freeing.

This is a fix for
mm-vmscan-block-kswapd-if-it-is-encountering-pages-under-writeback.patch

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
 mm/vmscan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index b1b38ad..4a43c28 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -766,8 +766,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			if (current_is_kswapd() &&
 			    PageReclaim(page) &&
 			    zone_is_reclaim_writeback(zone)) {
+				unlock_page(page);
 				congestion_wait(BLK_RW_ASYNC, HZ/10);
 				zone_clear_flag(zone, ZONE_WRITEBACK);
+				goto keep;
 
 			/* Case 2 above */
 			} else if (global_reclaim(sc) ||
-- 
1.8.1.4

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