mem_cgroup_end_move() checks if the passed memcg is NULL, along with a
lengthy comment to explain why this seemingly non-sensical situation
is even possible.
Check in cancel_attach() itself whether can_attach() set up the move
context or not, it's a lot more obvious from there. Then remove the
check and comment in mem_cgroup_end_move().
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
mm/memcontrol.c | 13 ++++---------
1 file changed, 4 insertions(+), 9 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ff125d2a427..c1fe774d712a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1452,14 +1452,8 @@ static void mem_cgroup_start_move(struct mem_cgroup *memcg)
static void mem_cgroup_end_move(struct mem_cgroup *memcg)
{
- /*
- * Now, mem_cgroup_clear_mc() may call this function with NULL.
- * We check NULL in callee rather than caller.
- */
- if (memcg) {
- atomic_dec(&memcg_moving);
- atomic_dec(&memcg->moving_account);
- }
+ atomic_dec(&memcg_moving);
+ atomic_dec(&memcg->moving_account);
}
/*
@@ -5383,7 +5377,8 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
static void mem_cgroup_cancel_attach(struct cgroup_subsys_state *css,
struct cgroup_taskset *tset)
{
- mem_cgroup_clear_mc();
+ if (mc.to)
+ mem_cgroup_clear_mc();
}
static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
--
2.1.2
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