Date:   Tue, 11 Jan 2022 09:40:20 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     Wei Yang <richard.weiyang@gmail.com>
Cc:     hannes@cmpxchg.org, vdavydov.dev@gmail.com,
        akpm@linux-foundation.org, shakeelb@google.com, guro@fb.com,
        vbabka@suse.cz, willy@infradead.org, songmuchun@bytedance.com,
        shy828301@gmail.com, surenb@google.com,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 1/4] mm/memcg: use NUMA_NO_NODE to indicate allocation
 from unspecified node
Message-ID: <Yd1CdJA5NelzoK1D@dhcp22.suse.cz>
References: <20220111010302.8864-1-richard.weiyang@gmail.com>
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On Tue 11-01-22 01:02:59, Wei Yang wrote:
> Instead of use "-1", let's use NUMA_NO_NODE for consistency.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

I am not really sure this is worth it. After the merge window I plan to
post http://lkml.kernel.org/r/20211214100732.26335-1-mhocko@kernel.org.
With that in place we can drop the check and a node rewrite so the net
result will be a less and more straightforward code. If you agree I can
add this with your s-o-b into my series:

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 781605e92015..ed19a21ee14e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5044,18 +5044,8 @@ struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
 static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 {
 	struct mem_cgroup_per_node *pn;
-	int tmp = node;
-	/*
-	 * This routine is called against possible nodes.
-	 * But it's BUG to call kmalloc() against offline node.
-	 *
-	 * TODO: this routine can waste much memory for nodes which will
-	 *       never be onlined. It's better to use memory hotplug callback
-	 *       function.
-	 */
-	if (!node_state(node, N_NORMAL_MEMORY))
-		tmp = -1;
-	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
+
+	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, node);
 	if (!pn)
 		return 1;
 
-- 
Michal Hocko
SUSE Labs