On Wed 13-09-17 17:59:27, Sherry Yang wrote:
> Restore asynchronous mmput, allowing mmput_async to be called
> from an atomic context in Android binder shrinker callback.
>
> mmput_async was initially introduced in ec8d7c14e
> ("mm, oom_reaper: do not mmput synchronously from the
> oom reaper context"), and was removed in 212925802
> ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
>
> Signed-off-by: Sherry Yang <[email protected]>
I would just fold this into https://lkml.org/lkml/2017/9/8/785. The
patch is simple enough to take this in one go and it will be clear who
and why needs to restore the api.
No objections otherwise.
Acked-by: Michal Hocko <[email protected]>
> ---
> include/linux/sched/mm.h | 6 ++++++
> kernel/fork.c | 18 ++++++++++++++++++
> 2 files changed, 24 insertions(+)
>
> diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> index 3a19c253bdb1..ae53e413fb13 100644
> --- a/include/linux/sched/mm.h
> +++ b/include/linux/sched/mm.h
> @@ -84,6 +84,12 @@ static inline bool mmget_not_zero(struct mm_struct *mm)
>
> /* mmput gets rid of the mappings and all user-space */
> extern void mmput(struct mm_struct *);
> +#ifdef CONFIG_MMU
> +/* same as above but performs the slow path from the async context. Can
> + * be called from the atomic context as well
> + */
> +void mmput_async(struct mm_struct *);
> +#endif
>
> /* Grab a reference to a task's mm, if it is not already going away */
> extern struct mm_struct *get_task_mm(struct task_struct *task);
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 10646182440f..e702cb9ffbd8 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -946,6 +946,24 @@ void mmput(struct mm_struct *mm)
> }
> EXPORT_SYMBOL_GPL(mmput);
>
> +#ifdef CONFIG_MMU
> +static void mmput_async_fn(struct work_struct *work)
> +{
> + struct mm_struct *mm = container_of(work, struct mm_struct,
> + async_put_work);
> +
> + __mmput(mm);
> +}
> +
> +void mmput_async(struct mm_struct *mm)
> +{
> + if (atomic_dec_and_test(&mm->mm_users)) {
> + INIT_WORK(&mm->async_put_work, mmput_async_fn);
> + schedule_work(&mm->async_put_work);
> + }
> +}
> +#endif
> +
> /**
> * set_mm_exe_file - change a reference to the mm's executable file
> *
> --
> 2.11.0 (Apple Git-81)
>
--
Michal Hocko
SUSE Labs
