[PATCH 2/2] mm/vmscan: shrink slab in node reclaim

[Yafang Shao <laoar.shao@gmail.com>]

In the node reclaim, may_shrinkslab is 0 by default,
hence shrink_slab will never be performed in it.
While shrik_slab should be performed if the relcaimable slab is over
min slab limit.

This issue is very easy to produce, first you continuously cat a random
non-exist file to produce more and more dentry, then you read big file
to produce page cache. And finally you will find that the denty will
never be shrunk.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 mm/vmscan.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d9c3e87..2c73223 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4141,6 +4141,8 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 		.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
 		.may_swap = 1,
 		.reclaim_idx = gfp_zone(gfp_mask),
+		.may_shrinkslab = node_page_state(pgdat, NR_SLAB_RECLAIMABLE) >
+				  pgdat->min_slab_pages,
 	};
 
 	trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
@@ -4158,15 +4160,13 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
 	reclaim_state.reclaimed_slab = 0;
 	p->reclaim_state = &reclaim_state;
 
-	if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) {
 		/*
 		 * Free memory by calling shrink node with increasing
 		 * priorities until we have enough memory freed.
 		 */
-		do {
-			shrink_node(pgdat, &sc);
-		} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
-	}
+	do {
+		shrink_node(pgdat, &sc);
+	} while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0);
 
 	p->reclaim_state = NULL;
 	current->flags &= ~PF_SWAPWRITE;
-- 
1.8.3.1