[patch 1/4] mm: memcontrol: uncharge pages on swapout

[Johannes Weiner <hannes@cmpxchg.org>]

mem_cgroup_swapout() is called with exclusive access to the page at
the end of the page's lifetime.  Instead of clearing the PCG_MEMSW
flag and deferring the uncharge, just do it right away.  This allows
follow-up patches to simplify the uncharge code.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/memcontrol.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bea3fddb3372..7709f17347f3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5799,6 +5799,7 @@ static void __init enable_swap_cgroup(void)
  */
 void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 {
+	struct mem_cgroup *memcg;
 	struct page_cgroup *pc;
 	unsigned short oldid;
 
@@ -5815,13 +5816,21 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 		return;
 
 	VM_BUG_ON_PAGE(!(pc->flags & PCG_MEMSW), page);
+	memcg = pc->mem_cgroup;
 
-	oldid = swap_cgroup_record(entry, mem_cgroup_id(pc->mem_cgroup));
+	oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
 	VM_BUG_ON_PAGE(oldid, page);
+	mem_cgroup_swap_statistics(memcg, true);
 
-	pc->flags &= ~PCG_MEMSW;
-	css_get(&pc->mem_cgroup->css);
-	mem_cgroup_swap_statistics(pc->mem_cgroup, true);
+	pc->flags = 0;
+
+	if (!mem_cgroup_is_root(memcg))
+		page_counter_uncharge(&memcg->memory, 1);
+
+	local_irq_disable();
+	mem_cgroup_charge_statistics(memcg, page, -1);
+	memcg_check_events(memcg, page);
+	local_irq_enable();
 }
 
 /**
-- 
2.1.2

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