The cpuset file is a legacy attribute that is bound primarily to cpuset
v1 hierarchy (equivalent information is available in /proc/$pid/cgroup path
on the unified hierarchy in conjunction with respective
cgroup.controllers showing where cpuset controller is enabled).

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@suse.com>
---
 init/Kconfig              |  5 +++--
 kernel/cgroup/cpuset-v1.c | 41 +++++++++++++++++++++++++++++++++++
 kernel/cgroup/cpuset.c    | 45 ---------------------------------------
 3 files changed, 44 insertions(+), 47 deletions(-)

v3 changes:
- move dependency on internal cgroup-internal.h to v1-only too
  Reported-by: kernel test robot <lkp@intel.com>
  Link: https://lore.kernel.org/oe-kbuild-all/202501180315.KcDn5BG5-lkp@intel.com/

v2 changes:
- explicitly say what's part of CPUSETS_V1
- commit message wrt effective paths

diff --git a/init/Kconfig b/init/Kconfig
index a20e6efd3f0fb..2f3121c49ed23 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1182,7 +1182,8 @@ config CPUSETS_V1
 	help
 	  Legacy cgroup v1 cpusets controller which has been deprecated by
 	  cgroup v2 implementation. The v1 is there for legacy applications
-	  which haven't migrated to the new cgroup v2 interface yet. If you
+	  which haven't migrated to the new cgroup v2 interface yet. Legacy
+	  interface includes cpuset filesystem and /proc/<pid>/cpuset. If you
 	  do not have any such application then you are completely fine leaving
 	  this option disabled.
 
@@ -1190,7 +1191,7 @@ 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..81b5e2a50d587 100644
--- a/kernel/cgroup/cpuset-v1.c
+++ b/kernel/cgroup/cpuset-v1.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include "cgroup-internal.h"
 #include "cpuset-internal.h"
 
 /*
@@ -373,6 +374,46 @@ 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..5a637292faa20 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -21,7 +21,6 @@
  *  License.  See the file COPYING in the main directory of the Linux
  *  distribution for more details.
  */
-#include "cgroup-internal.h"
 #include "cpuset-internal.h"
 
 #include <linux/init.h>
@@ -4244,50 +4243,6 @@ 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

On Mon, Jan 20, 2025 at 03:57:49PM +0100, Michal Koutný wrote:
> The cpuset file is a legacy attribute that is bound primarily to cpuset
> v1 hierarchy (equivalent information is available in /proc/$pid/cgroup path
> on the unified hierarchy in conjunction with respective
> cgroup.controllers showing where cpuset controller is enabled).
> 
> 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@suse.com>

Applied to cgroup/for-6.15.

Thanks.

-- 
tejun

On 1/20/25 9:57 AM, Michal Koutný wrote:
> The cpuset file is a legacy attribute that is bound primarily to cpuset
> v1 hierarchy (equivalent information is available in /proc/$pid/cgroup path
> on the unified hierarchy in conjunction with respective
> cgroup.controllers showing where cpuset controller is enabled).
>
> 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@suse.com>
> ---
>   init/Kconfig              |  5 +++--
>   kernel/cgroup/cpuset-v1.c | 41 +++++++++++++++++++++++++++++++++++
>   kernel/cgroup/cpuset.c    | 45 ---------------------------------------
>   3 files changed, 44 insertions(+), 47 deletions(-)
>
> v3 changes:
> - move dependency on internal cgroup-internal.h to v1-only too
>    Reported-by: kernel test robot <lkp@intel.com>
>    Link: https://lore.kernel.org/oe-kbuild-all/202501180315.KcDn5BG5-lkp@intel.com/
>
> v2 changes:
> - explicitly say what's part of CPUSETS_V1
> - commit message wrt effective paths
Acked-by: Waiman Long <longman@redhat.com>

>
> diff --git a/init/Kconfig b/init/Kconfig
> index a20e6efd3f0fb..2f3121c49ed23 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1182,7 +1182,8 @@ config CPUSETS_V1
>   	help
>   	  Legacy cgroup v1 cpusets controller which has been deprecated by
>   	  cgroup v2 implementation. The v1 is there for legacy applications
> -	  which haven't migrated to the new cgroup v2 interface yet. If you
> +	  which haven't migrated to the new cgroup v2 interface yet. Legacy
> +	  interface includes cpuset filesystem and /proc/<pid>/cpuset. If you
>   	  do not have any such application then you are completely fine leaving
>   	  this option disabled.
>   
> @@ -1190,7 +1191,7 @@ 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..81b5e2a50d587 100644
> --- a/kernel/cgroup/cpuset-v1.c
> +++ b/kernel/cgroup/cpuset-v1.c
> @@ -1,5 +1,6 @@
>   // SPDX-License-Identifier: GPL-2.0-or-later
>   
> +#include "cgroup-internal.h"
>   #include "cpuset-internal.h"
>   
>   /*
> @@ -373,6 +374,46 @@ 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..5a637292faa20 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -21,7 +21,6 @@
>    *  License.  See the file COPYING in the main directory of the Linux
>    *  distribution for more details.
>    */
> -#include "cgroup-internal.h"
>   #include "cpuset-internal.h"
>   
>   #include <linux/init.h>
> @@ -4244,50 +4243,6 @@ 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)
>   {