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Date:   Sun, 6 Nov 2022 21:56:00 +0100
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Subject: Re: [PATCH 8/8] mm/slub, percpu: correct the calculation of early
 percpu allocation size
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To:     Baoquan He <bhe@redhat.com>, linux-kernel@vger.kernel.org
Cc:     Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>
References: <20221024081435.204970-1-bhe@redhat.com>
 <20221024081435.204970-9-bhe@redhat.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20221024081435.204970-9-bhe@redhat.com>
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Precedence: bulk

On 10/24/22 10:14, 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@redhat.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
>  mm/slub.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

As only slub is touched and there's no prerequsities in the previous
patches, I took this to the slab tree, branch
slab/for-6.2/cleanups

Thanks!

> 
> 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