linux-kernel - Re: [PATCH mm-unstable RFC 5/5] cgroup: remove cgroup_rstat_flush

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Message-ID: <CALvZod79Au=Fw9MTW7fP0P7KwQQ_NUiKgRHsNUFnv9v61pKnZA@mail.gmail.com>
Date:   Thu, 20 Apr 2023 12:40:24 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Yosry Ahmed <yosryahmed@...gle.com>, Tejun Heo <tj@...nel.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH mm-unstable RFC 5/5] cgroup: remove cgroup_rstat_flush_atomic()

+Tejun


On Mon, Apr 3, 2023 at 3:03 PM Yosry Ahmed <yosryahmed@...gle.com> wrote:
>
> Previous patches removed the only caller of cgroup_rstat_flush_atomic().
> Remove the function and simplify the code.


I would say let cgroup maintainers decide this and this patch can be
decoupled from the series.

>
> Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
> ---
>  include/linux/cgroup.h |  1 -
>  kernel/cgroup/rstat.c  | 26 +++++---------------------
>  2 files changed, 5 insertions(+), 22 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 885f5395fcd04..567c547cf371f 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -692,7 +692,6 @@ static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
>   */
>  void cgroup_rstat_updated(struct cgroup *cgrp, int cpu);
>  void cgroup_rstat_flush(struct cgroup *cgrp);
> -void cgroup_rstat_flush_atomic(struct cgroup *cgrp);
>  void cgroup_rstat_flush_hold(struct cgroup *cgrp);
>  void cgroup_rstat_flush_release(void);
>
> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
> index d3252b0416b69..f9ad33f117c82 100644
> --- a/kernel/cgroup/rstat.c
> +++ b/kernel/cgroup/rstat.c
> @@ -171,7 +171,7 @@ __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
>  __diag_pop();
>
>  /* see cgroup_rstat_flush() */
> -static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
> +static void cgroup_rstat_flush_locked(struct cgroup *cgrp)
>         __releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
>  {
>         int cpu;
> @@ -207,9 +207,8 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
>                 }
>                 raw_spin_unlock_irqrestore(cpu_lock, flags);
>
> -               /* if @may_sleep, play nice and yield if necessary */
> -               if (may_sleep && (need_resched() ||
> -                                 spin_needbreak(&cgroup_rstat_lock))) {
> +               /* play nice and yield if necessary */
> +               if (need_resched() || spin_needbreak(&cgroup_rstat_lock)) {
>                         spin_unlock_irq(&cgroup_rstat_lock);
>                         if (!cond_resched())
>                                 cpu_relax();
> @@ -236,25 +235,10 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
>         might_sleep();
>
>         spin_lock_irq(&cgroup_rstat_lock);
> -       cgroup_rstat_flush_locked(cgrp, true);
> +       cgroup_rstat_flush_locked(cgrp);
>         spin_unlock_irq(&cgroup_rstat_lock);
>  }
>
> -/**
> - * cgroup_rstat_flush_atomic- atomic version of cgroup_rstat_flush()
> - * @cgrp: target cgroup
> - *
> - * This function can be called from any context.
> - */
> -void cgroup_rstat_flush_atomic(struct cgroup *cgrp)
> -{
> -       unsigned long flags;
> -
> -       spin_lock_irqsave(&cgroup_rstat_lock, flags);
> -       cgroup_rstat_flush_locked(cgrp, false);
> -       spin_unlock_irqrestore(&cgroup_rstat_lock, flags);
> -}
> -
>  /**
>   * cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold
>   * @cgrp: target cgroup
> @@ -269,7 +253,7 @@ void cgroup_rstat_flush_hold(struct cgroup *cgrp)
>  {
>         might_sleep();
>         spin_lock_irq(&cgroup_rstat_lock);
> -       cgroup_rstat_flush_locked(cgrp, true);
> +       cgroup_rstat_flush_locked(cgrp);
>  }
>
>  /**
> --
> 2.40.0.348.gf938b09366-goog
>