linux-kernel - [PATCH 2/2] cgroup: get the wrong css for css_alloc() during cgroup_init

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Message-Id: <20211127145919.31159-2-richard.weiyang@gmail.com>
Date:   Sat, 27 Nov 2021 14:59:19 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     tj@...nel.org, lizefan.x@...edance.com, hannes@...xchg.org
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wei Yang <richard.weiyang@...il.com>
Subject: [PATCH 2/2] cgroup: get the wrong css for css_alloc() during cgroup_init_subsys()

css_alloc() needs the parent css, while cgroup_css() gets current
cgropu's css. So we are getting the wrong css during
cgroup_init_subsys().

Fortunately, cgrp_dfl_root.cgrp's css is not set yet, so the value we
pass to css_alloc() doesn't harm to the system.

Let's pass NULL directly during init, since we know there is no parent
yet.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
---
 kernel/cgroup/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index dffef5836ff7..452a723d4a36 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -5709,7 +5709,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
 
 	/* Create the root cgroup state for this subsystem */
 	ss->root = &cgrp_dfl_root;
-	css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
+	css = ss->css_alloc(NULL);
 	/* We don't handle early failures gracefully */
 	BUG_ON(IS_ERR(css));
 	init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
-- 
2.33.1