[PATCH] mm/vmscan: pass NULL to trace vmscan node reclaim

[Ben Dooks <ben.dooks@codethink.co.uk>]

The tracepoint for node relcaims takes a `struct mem_cgroup *`
as the third argument, so pass NULL instead of 0 to fix warning
about using an integer as a pointer.

Fixes the following warnings:

mm/vmscan.c:6753:66: warning: Using plain integer as NULL pointer
mm/vmscan.c:6757:58: warning: Using plain integer as NULL pointer
mm/vmscan.c:7818:60: warning: Using plain integer as NULL pointer

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 mm/vmscan.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 67231d3189ef..a7699f2112d3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -6750,11 +6750,11 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 		return 1;
 
 	set_task_reclaim_state(current, &sc.reclaim_state);
-	trace_mm_vmscan_direct_reclaim_begin(sc.gfp_mask, order, 0);
+	trace_mm_vmscan_direct_reclaim_begin(sc.gfp_mask, order, NULL);
 
 	nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
 
-	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed, 0);
+	trace_mm_vmscan_direct_reclaim_end(nr_reclaimed, NULL);
 	set_task_reclaim_state(current, NULL);
 
 	return nr_reclaimed;
@@ -7815,7 +7815,7 @@ static unsigned long __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask,
 	delayacct_freepages_end();
 	psi_memstall_leave(&pflags);
 
-	trace_mm_vmscan_node_reclaim_end(sc->nr_reclaimed, 0);
+	trace_mm_vmscan_node_reclaim_end(sc->nr_reclaimed, NULL);
 
 	return sc->nr_reclaimed;
 }
-- 
2.37.2.352.g3c44437643