[PATCH] mm: vmscan: count only dirty pages as congested

[Jamie Liu <jamieliu@google.com>]

shrink_page_list() counts all pages with a mapping, including clean
pages, toward nr_congested if they're on a write-congested BDI.
shrink_inactive_list() then sets ZONE_CONGESTED if nr_dirty ==
nr_congested. Fix this apples-to-oranges comparison by only counting
pages for nr_congested if they count for nr_dirty.

Signed-off-by: Jamie Liu <jamieliu@google.com>
---
 mm/vmscan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index dcb4707..ad9cd9f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -875,7 +875,8 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 * end of the LRU a second time.
 		 */
 		mapping = page_mapping(page);
-		if ((mapping && bdi_write_congested(mapping->backing_dev_info)) ||
+		if (((dirty || writeback) && mapping &&
+		     bdi_write_congested(mapping->backing_dev_info)) ||
 		    (writeback && PageReclaim(page)))
 			nr_congested++;
 
-- 
2.1.0.rc2.206.gedb03e5

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