linux-kernel - [PATCH -next] mm/memcg: fix a -Wparentheses compilation warning

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Date:   Wed, 31 Jul 2019 09:45:53 -0400
From:   Qian Cai <cai@....pw>
To:     akpm@...ux-foundation.org
Cc:     miles.chen@...iatek.com, mhocko@...e.com, hannes@...xchg.org,
        vdavydov.dev@...il.com, cgroups@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH -next] mm/memcg: fix a -Wparentheses compilation warning

The linux-next commit ("mm/memcontrol.c: fix use after free in
mem_cgroup_iter()") [1] introduced a compilation warning,

mm/memcontrol.c:1160:17: warning: using the result of an assignment as a
condition without parentheses [-Wparentheses]
        } while (memcg = parent_mem_cgroup(memcg));
                 ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
mm/memcontrol.c:1160:17: note: place parentheses around the assignment
to silence this warning
        } while (memcg = parent_mem_cgroup(memcg));
                       ^
                 (                               )
mm/memcontrol.c:1160:17: note: use '==' to turn this assignment into an
equality comparison
        } while (memcg = parent_mem_cgroup(memcg));
                       ^
                       ==

Fix it by adding a pair of parentheses.

[1] https://lore.kernel.org/linux-mm/20190730015729.4406-1-miles.chen@mediatek.com/

Signed-off-by: Qian Cai <cai@....pw>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 694b6f8776dc..4f66a8305ae0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1157,7 +1157,7 @@ static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg)
 	do {
 		__invalidate_reclaim_iterators(memcg, dead_memcg);
 		last = memcg;
-	} while (memcg = parent_mem_cgroup(memcg));
+	} while ((memcg = parent_mem_cgroup(memcg)));
 
 	/*
 	 * When cgruop1 non-hierarchy mode is used,
-- 
1.8.3.1