linux-kernel - Re: [PATCH 8/8] mm/slub, percpu: correct the calculation of early percpu allocation size

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Date:   Mon, 24 Oct 2022 10:03:33 -0700
From:   Dennis Zhou <dennis@...nel.org>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: Re: [PATCH 8/8] mm/slub, percpu: correct the calculation of early
 percpu allocation size

On Mon, Oct 24, 2022 at 04:14:35PM +0800, Baoquan He wrote:
> SLUB allocator relies on percpu allocator to initialize its ->cpu_slab
> during early boot. For that, the dynamic chunk of percpu which serves
> the early allocation need be large enough to satisfy the kmalloc
> creation.
> 
> However, the current BUILD_BUG_ON() in alloc_kmem_cache_cpus() doesn't
> consider the kmalloc array with NR_KMALLOC_TYPES length. Fix that
> with correct calculation.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Roman Gushchin <roman.gushchin@...ux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@...il.com>
> ---
>  mm/slub.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 157527d7101b..8ac3bb9a122a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -4017,7 +4017,8 @@ init_kmem_cache_node(struct kmem_cache_node *n)
>  static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
>  {
>  	BUILD_BUG_ON(PERCPU_DYNAMIC_EARLY_SIZE <
> -			KMALLOC_SHIFT_HIGH * sizeof(struct kmem_cache_cpu));
> +			NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH *
> +			sizeof(struct kmem_cache_cpu));
>  
>  	/*
>  	 * Must align to double word boundary for the double cmpxchg
> -- 
> 2.34.1
> 

Acked-by: Dennis Zhou <dennis@...nel.org>

Thanks,
Dennis