[Resend PATCH 2/6] mm/memcg: remove useless check on page->mem_cgroup

[Alex Shi]

If we disabled memcg by cgroup_disable=memory, the swap charges are
still called. Let's return from the funcs earlier and keep WARN_ON
monitor.

Signed-off-by: Alex Shi <alex....@linux.alibaba.com>
Reviewed-by: Roman Gushchin <g...@fb.com>
Acked-by: Michal Hocko <mho...@suse.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Michal Hocko <mho...@kernel.org>
Cc: Vladimir Davydov <vdavydov....@gmail.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: cgro...@vger.kernel.org
Cc: linux...@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/memcontrol.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 299382fc55a9..419cf565f40b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t 
entry)
        VM_BUG_ON_PAGE(PageLRU(page), page);
        VM_BUG_ON_PAGE(page_count(page), page);
 
+       if (mem_cgroup_disabled())
+               return;
+
        if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return;
 
@@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, 
swp_entry_t entry)
        struct mem_cgroup *memcg;
        unsigned short oldid;
 
+       if (mem_cgroup_disabled())
+               return 0;
+
        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return 0;
 
-- 
1.8.3.1