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From: "brookxu.cn" <brookxu.cn@gmail.com>
To: longman@redhat.com,
	lizefan.x@bytedance.com,
	tj@kernel.org,
	hannes@cmpxchg.org
Cc: linux-kernel@vger.kernel.org
Subject: [RFC PATCH] cpuset: remove /proc/PID/cpuset
Date: Fri,  2 Feb 2024 18:49:11 +0800
Message-Id: <20240202104911.125894-1-brookxu.cn@gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

From: Chunguang Xu <chunguang.xu@shopee.com>

Now we can get all cgroup paths from /proc/PID/cgroup for
a long time, so it maybe useless to keep /proc/PID/cpuset,
besides the path get from /proc/PID/cpuset is not consistent
with /proc/PID/cgroup in default hierarchy, so now we may
can safely remove /proc/PID/cpuset to avoid the mismatch.

root@test:~# cat /proc/1186/cgroup
0::/system.slice/lmeter.service

root@test:~# cat /proc/1186/cpuset
/system.slice

Signed-off-by: Chunguang Xu <chunguang.xu@shopee.com>
---
 arch/mips/configs/sb1250_swarm_defconfig |  1 -
 arch/sh/configs/sdk7786_defconfig        |  1 -
 arch/sh/configs/urquell_defconfig        |  1 -
 fs/proc/base.c                           |  6 ----
 kernel/cgroup/cpuset.c                   | 40 ------------------------
 5 files changed, 49 deletions(-)

diff --git a/arch/mips/configs/sb1250_swarm_defconfig b/arch/mips/configs/sb1250_swarm_defconfig
index ce855b644bb0..2fbea9c604df 100644
--- a/arch/mips/configs/sb1250_swarm_defconfig
+++ b/arch/mips/configs/sb1250_swarm_defconfig
@@ -3,7 +3,6 @@ CONFIG_HIGH_RES_TIMERS=y
 CONFIG_LOG_BUF_SHIFT=15
 CONFIG_CGROUPS=y
 CONFIG_CPUSETS=y
-# CONFIG_PROC_PID_CPUSET is not set
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_NAMESPACES=y
 CONFIG_RELAY=y
diff --git a/arch/sh/configs/sdk7786_defconfig b/arch/sh/configs/sdk7786_defconfig
index 7b427c17fbfe..6fe340d4860c 100644
--- a/arch/sh/configs/sdk7786_defconfig
+++ b/arch/sh/configs/sdk7786_defconfig
@@ -13,7 +13,6 @@ CONFIG_CGROUP_DEBUG=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CGROUP_DEVICE=y
 CONFIG_CPUSETS=y
-# CONFIG_PROC_PID_CPUSET is not set
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_MEMCG=y
 CONFIG_CGROUP_SCHED=y
diff --git a/arch/sh/configs/urquell_defconfig b/arch/sh/configs/urquell_defconfig
index 445bb451a5ec..c960221a0549 100644
--- a/arch/sh/configs/urquell_defconfig
+++ b/arch/sh/configs/urquell_defconfig
@@ -11,7 +11,6 @@ CONFIG_CGROUP_DEBUG=y
 CONFIG_CGROUP_FREEZER=y
 CONFIG_CGROUP_DEVICE=y
 CONFIG_CPUSETS=y
-# CONFIG_PROC_PID_CPUSET is not set
 CONFIG_CGROUP_CPUACCT=y
 CONFIG_CGROUP_MEMCG=y
 CONFIG_CGROUP_SCHED=y
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 98a031ac2648..8dcd23b9212a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3309,9 +3309,6 @@ static const struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_LATENCYTOP
 	REG("latency",  S_IRUGO, proc_lstats_operations),
 #endif
-#ifdef CONFIG_PROC_PID_CPUSET
-	ONE("cpuset",     S_IRUGO, proc_cpuset_show),
-#endif
 #ifdef CONFIG_CGROUPS
 	ONE("cgroup",  S_IRUGO, proc_cgroup_show),
 #endif
@@ -3658,9 +3655,6 @@ static const struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_LATENCYTOP
 	REG("latency",  S_IRUGO, proc_lstats_operations),
 #endif
-#ifdef CONFIG_PROC_PID_CPUSET
-	ONE("cpuset",    S_IRUGO, proc_cpuset_show),
-#endif
 #ifdef CONFIG_CGROUPS
 	ONE("cgroup",  S_IRUGO, proc_cgroup_show),
 #endif
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index ba36c073304a..908cd7e6efa8 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -5066,46 +5066,6 @@ void __cpuset_memory_pressure_bump(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;
-
-	css = task_get_css(tsk, cpuset_cgrp_id);
-	retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
-				current->nsproxy->cgroup_ns);
-	css_put(css);
-	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)
 {
-- 
2.25.1