linux-kernel - [PATCH] sched/core: Fix wrong burst unit in cgroup2 cpu.max write

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Date:   Fri, 10 Sep 2021 12:25:09 -0400
From:   Kailun Qin <kailun.qin@...el.com>
To:     tj@...nel.org, bsegall@...gle.com, linux-kernel@...r.kernel.org
Cc:     cgroups@...r.kernel.org, changhuaixin@...ux.alibaba.com,
        mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, Kailun Qin <kailun.qin@...el.com>
Subject: [PATCH] sched/core: Fix wrong burst unit in cgroup2 cpu.max write

In cpu_max_write(), as the eventual tg_set_cfs_bandwidth() operates on
the burst in nsec which is input from tg_get_cfs_burst() in usec, it
should be converted into nsec accordingly.

If not, this may cause a write into cgroup2 cpu.max to unexpectedly
change an already set cpu.max.burst.

This patch addresses the above issue.

Signed-off-by: Kailun Qin <kailun.qin@...el.com>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c4462c454ab9..fc9fcc56149f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10711,7 +10711,7 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of,
 {
 	struct task_group *tg = css_tg(of_css(of));
 	u64 period = tg_get_cfs_period(tg);
-	u64 burst = tg_get_cfs_burst(tg);
+	u64 burst = (u64)tg_get_cfs_burst(tg) * NSEC_PER_USEC;
 	u64 quota;
 	int ret;
 
-- 
2.25.1