linux-kernel - [PATCH] cgroup/cpuset: Move procfs cpuset attribute under cgroup-v1.c

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Message-ID: <20250116095656.643976-1-mkoutny@suse.com>
Date: Thu, 16 Jan 2025 10:56:56 +0100
From: Michal Koutný <mkoutny@...e.com>
To: linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Cc: Waiman Long <longman@...hat.com>,
	Tejun Heo <tj@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	Chen Ridong <chenridong@...wei.com>
Subject: [PATCH] cgroup/cpuset: Move procfs cpuset attribute under cgroup-v1.c

The cpuset file is a legacy attribute that is bound primarily to cpuset
v1 (and it'd be equal to effective /proc/$pid/cgroup path on the unified
hierarchy).

Followup to commit b0ced9d378d49 ("cgroup/cpuset: move v1 interfaces to
cpuset-v1.c") and hide CONFIG_PROC_PID_CPUSET under CONFIG_CPUSETS_V1.
Drop an obsolete comment too.

Signed-off-by: Michal Koutný <mkoutny@...e.com>
---
 init/Kconfig              |  2 +-
 kernel/cgroup/cpuset-v1.c | 40 +++++++++++++++++++++++++++++++++++
 kernel/cgroup/cpuset.c    | 44 ---------------------------------------
 3 files changed, 41 insertions(+), 45 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index a20e6efd3f0fb..2a1d5ef3fa48e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1190,7 +1190,7 @@ config CPUSETS_V1
 
 config PROC_PID_CPUSET
 	bool "Include legacy /proc/<pid>/cpuset file"
-	depends on CPUSETS
+	depends on CPUSETS_V1
 	default y
 
 config CGROUP_DEVICE
diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c
index 25c1d7b77e2f2..fff1a38f2725f 100644
--- a/kernel/cgroup/cpuset-v1.c
+++ b/kernel/cgroup/cpuset-v1.c
@@ -373,6 +373,46 @@ int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial)
 	return ret;
 }
 
+#ifdef CONFIG_PROC_PID_CPUSET
+/*
+ * proc_cpuset_show()
+ *  - Print tasks cpuset path into seq_file.
+ *  - Used for /proc/<pid>/cpuset.
+ */
+int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
+		     struct pid *pid, struct task_struct *tsk)
+{
+	char *buf;
+	struct cgroup_subsys_state *css;
+	int retval;
+
+	retval = -ENOMEM;
+	buf = kmalloc(PATH_MAX, GFP_KERNEL);
+	if (!buf)
+		goto out;
+
+	rcu_read_lock();
+	spin_lock_irq(&css_set_lock);
+	css = task_css(tsk, cpuset_cgrp_id);
+	retval = cgroup_path_ns_locked(css->cgroup, buf, PATH_MAX,
+				       current->nsproxy->cgroup_ns);
+	spin_unlock_irq(&css_set_lock);
+	rcu_read_unlock();
+
+	if (retval == -E2BIG)
+		retval = -ENAMETOOLONG;
+	if (retval < 0)
+		goto out_free;
+	seq_puts(m, buf);
+	seq_putc(m, '\n');
+	retval = 0;
+out_free:
+	kfree(buf);
+out:
+	return retval;
+}
+#endif /* CONFIG_PROC_PID_CPUSET */
+
 static u64 cpuset_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
 {
 	struct cpuset *cs = css_cs(css);
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 0f910c828973a..7d6e8db234290 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -4244,50 +4244,6 @@ void cpuset_print_current_mems_allowed(void)
 	rcu_read_unlock();
 }
 
-#ifdef CONFIG_PROC_PID_CPUSET
-/*
- * proc_cpuset_show()
- *  - Print tasks cpuset path into seq_file.
- *  - Used for /proc/<pid>/cpuset.
- *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
- *    doesn't really matter if tsk->cpuset changes after we read it,
- *    and we take cpuset_mutex, keeping cpuset_attach() from changing it
- *    anyway.
- */
-int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
-		     struct pid *pid, struct task_struct *tsk)
-{
-	char *buf;
-	struct cgroup_subsys_state *css;
-	int retval;
-
-	retval = -ENOMEM;
-	buf = kmalloc(PATH_MAX, GFP_KERNEL);
-	if (!buf)
-		goto out;
-
-	rcu_read_lock();
-	spin_lock_irq(&css_set_lock);
-	css = task_css(tsk, cpuset_cgrp_id);
-	retval = cgroup_path_ns_locked(css->cgroup, buf, PATH_MAX,
-				       current->nsproxy->cgroup_ns);
-	spin_unlock_irq(&css_set_lock);
-	rcu_read_unlock();
-
-	if (retval == -E2BIG)
-		retval = -ENAMETOOLONG;
-	if (retval < 0)
-		goto out_free;
-	seq_puts(m, buf);
-	seq_putc(m, '\n');
-	retval = 0;
-out_free:
-	kfree(buf);
-out:
-	return retval;
-}
-#endif /* CONFIG_PROC_PID_CPUSET */
-
 /* Display task mems_allowed in /proc/<pid>/status file. */
 void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
 {
-- 
2.47.1