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

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Message-ID: <ZW04iGENbNm3A/Ki@casper.infradead.org>
Date:   Mon, 4 Dec 2023 02:25:12 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     NeilBrown <neilb@...e.de>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        Jens Axboe <axboe@...nel.dk>, 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>,
        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 Mon, Dec 04, 2023 at 12:36:41PM +1100, NeilBrown wrote:
> +++ 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))) {

You could lose one set of parens here ...

		if (likely(task->flags & PF_RUNS_TASK_WORK)) {

>  #define PF_RANDOMIZE		0x00400000	/* Randomize virtual address space */
> -#define PF__HOLE__00800000	0x00800000
> +#define PF_RUNS_TASK_WORK	0x00800000	/* Will call task_work_run() periodically */

And you could lose "Will" here:

#define PF_RUNS_TASK_WORK    0x00800000      /* Calls task_work_run() periodically */

> 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);

_GPL?