linux-kernel - Re: [RFC PATCH v3 5/7] slub: Introduce freeze

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Date:   Mon, 30 Oct 2023 19:11:02 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     chengming.zhou@...ux.dev, cl@...ux.com, penberg@...nel.org
Cc:     rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
        42.hyeyoo@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [RFC PATCH v3 5/7] slub: Introduce freeze_slab()

On 10/24/23 11:33, chengming.zhou@...ux.dev wrote:
> From: Chengming Zhou <zhouchengming@...edance.com>
> 
> We will have unfrozen slabs out of the node partial list later, so we
> need a freeze_slab() function to freeze the partial slab and get its
> freelist.
> 
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

As you noted, we'll need slab_update_freelist().
Otherwise,

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/slub.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 7d0234bffad3..5b428648021f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3079,6 +3079,33 @@ static inline void *get_freelist(struct kmem_cache *s, struct slab *slab)
>  	return freelist;
>  }
>  
> +/*
> + * Freeze the partial slab and return the pointer to the freelist.
> + */
> +static inline void *freeze_slab(struct kmem_cache *s, struct slab *slab)
> +{
> +	struct slab new;
> +	unsigned long counters;
> +	void *freelist;
> +
> +	do {
> +		freelist = slab->freelist;
> +		counters = slab->counters;
> +
> +		new.counters = counters;
> +		VM_BUG_ON(new.frozen);
> +
> +		new.inuse = slab->objects;
> +		new.frozen = 1;
> +
> +	} while (!__slab_update_freelist(s, slab,
> +		freelist, counters,
> +		NULL, new.counters,
> +		"freeze_slab"));
> +
> +	return freelist;
> +}
> +
>  /*
>   * Slow path. The lockless freelist is empty or we need to perform
>   * debugging duties.