linux-kernel - Re: [PATCH 12/41] mm: add per-VMA lock and helper functions to control it

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Message-ID: <Y8a5lRr+qNVwau5G@dhcp22.suse.cz>
Date:   Tue, 17 Jan 2023 16:07:01 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, michel@...pinasse.org,
        jglisse@...gle.com, vbabka@...e.cz, hannes@...xchg.org,
        mgorman@...hsingularity.net, dave@...olabs.net,
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        ldufour@...ux.ibm.com, laurent.dufour@...ibm.com,
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        hughd@...gle.com, bigeasy@...utronix.de, kent.overstreet@...ux.dev,
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        arjunroy@...gle.com, soheil@...gle.com, hughlynch@...gle.com,
        leewalsh@...gle.com, posk@...gle.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
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Subject: Re: [PATCH 12/41] mm: add per-VMA lock and helper functions to
 control it

On Mon 09-01-23 12:53:07, Suren Baghdasaryan wrote:
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 5986817f393c..c026d75108b3 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -474,6 +474,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
>  		 */
>  		*new = data_race(*orig);
>  		INIT_LIST_HEAD(&new->anon_vma_chain);
> +		vma_init_lock(new);
>  		dup_anon_vma_name(orig, new);
>  	}
>  	return new;
> @@ -1145,6 +1146,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
>  	seqcount_init(&mm->write_protect_seq);
>  	mmap_init_lock(mm);
>  	INIT_LIST_HEAD(&mm->mmlist);
> +#ifdef CONFIG_PER_VMA_LOCK
> +	WRITE_ONCE(mm->mm_lock_seq, 0);
> +#endif

The mm shouldn't be visible so why WRITE_ONCE?

-- 
Michal Hocko
SUSE Labs