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

Hyeonggon Yoo
2022-10-24T15:39:13Z

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@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(-)
>
> 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

Looks good to me.

Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>

Thanks!

> --
> 2.34.1
>

--
Thanks,
Hyeonggon