Re: [PATCH 6/8] fs: convert process/thread iterators to for_each_*_rcu

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

Please cc everybody on every patch in the series :) it makes it incredible hard
for me to see context otherwise.

I can already see a comment I'd like to leave on another patch in the series but
it's a total pain for me go retrieve that to do it.

And I worry about acking one bit only to find out a horrible flaw in another
part :P

Can you please make sure to do that on any respin?...

On Fri, Sep 04, 2026 at 04:29:58PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
>
> Replace the manual rcu_read_lock()/rcu_read_unlock() pairs combined
> with for_each_process() and for_each_process_thread() loops in fs/
> with the for_each_*_rcu() macros.

Probably worth mentioning that they hold the RCU lock in a scoped guard over the
operation.

>
> No functional change.
>
> Signed-off-by: Ye Liu <liuye@kylinos.cn>

In general it looks reasonable to me, but I wonder if you're correctly including
linux/cleanup.h to have the scope guard available...

Anyway can check that on respin with the right cc ;)

> ---
>  fs/proc/base.c        | 4 +---
>  fs/resctrl/rdtgroup.c | 8 ++------
>  2 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 6a39de424f62..da36ba73dc17 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1160,8 +1160,7 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)

Side-note - I wonder if this really belongs in mm/oom_kill.c? Seems really odd
to have it here.

>  	if (mm) {
>  		struct task_struct *p;
>
> -		rcu_read_lock();
> -		for_each_process(p) {
> +		for_each_process_rcu(p) {
>  			if (same_thread_group(task, p))
>  				continue;
>
> @@ -1177,7 +1176,6 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
>  			}
>  			task_unlock(p);
>  		}
> -		rcu_read_unlock();
>  		mmdrop(mm);
>  	}
>  err_unlock:
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 5dcbb0a964e8..3f96d21b84ab 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -709,14 +709,12 @@ int rdtgroup_tasks_assigned(struct rdtgroup *r)
>
>  	lockdep_assert_held(&rdtgroup_mutex);
>
> -	rcu_read_lock();
> -	for_each_process_thread(p, t) {
> +	for_each_process_thread_rcu(p, t) {
>  		if (is_closid_match(t, r) || is_rmid_match(t, r)) {
>  			ret = 1;
>  			break;
>  		}
>  	}
> -	rcu_read_unlock();
>
>  	return ret;
>  }
> @@ -826,15 +824,13 @@ static void show_rdt_tasks(struct rdtgroup *r, struct seq_file *s)
>  	struct task_struct *p, *t;
>  	pid_t pid;
>
> -	rcu_read_lock();
> -	for_each_process_thread(p, t) {
> +	for_each_process_thread_rcu(p, t) {
>  		if (is_closid_match(t, r) || is_rmid_match(t, r)) {
>  			pid = task_pid_vnr(t);
>  			if (pid)
>  				seq_printf(s, "%d\n", pid);
>  		}
>  	}
> -	rcu_read_unlock();
>  }
>
>  static int rdtgroup_tasks_show(struct kernfs_open_file *of,
> --
> 2.25.1
>

--
Cheers, Lorenzo