linux-kernel - Re: [PATCH 1/2] Allow a kthread to declare that it calls task_work

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Date:   Sun, 3 Dec 2023 19:13:56 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     NeilBrown <neilb@...e.de>, Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org
Subject: Re: [PATCH 1/2] Allow a kthread to declare that it calls
 task_work_run()

On 12/3/23 6:36 PM, NeilBrown wrote:
> diff --git a/fs/namespace.c b/fs/namespace.c
> index e157efc54023..46d640b70ca9 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1328,7 +1328,7 @@ static void mntput_no_expire(struct mount *mnt)
>  
>  	if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
>  		struct task_struct *task = current;
> -		if (likely(!(task->flags & PF_KTHREAD))) {
> +		if (likely((task->flags & PF_RUNS_TASK_WORK))) {

Extraneous parens here.

> diff --git a/kernel/task_work.c b/kernel/task_work.c
> index 95a7e1b7f1da..aec19876e121 100644
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -183,3 +183,4 @@ void task_work_run(void)
>  		} while (work);
>  	}
>  }
> +EXPORT_SYMBOL(task_work_run);

If we're exporting this, then I think that function needs a big
disclaimer on exactly when it is safe to call it. And it most certainly
needs to be a _GPL export.

-- 
Jens Axboe