linux-kernel - Re: [PATCH 09/12] mm, slub: split out allocations from pre/post hooks

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Message-ID: <Y4NB5i4WBvLr1GGZ@hyeyoo>
Date:   Sun, 27 Nov 2022 19:54:30 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, patches@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/12] mm, slub: split out allocations from pre/post hooks

On Mon, Nov 21, 2022 at 06:11:59PM +0100, Vlastimil Babka wrote:
> In the following patch we want to introduce CONFIG_SLUB_TINY allocation
> paths that don't use the percpu slab. To prepare, refactor the
> allocation functions:
> 
> Split out __slab_alloc_node() from slab_alloc_node() where the former
> does the actual allocation and the latter calls the pre/post hooks.
> 
> Analogically, split out __kmem_cache_alloc_bulk() from
> kmem_cache_alloc_bulk().
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/slub.c | 127 +++++++++++++++++++++++++++++++++---------------------
>  1 file changed, 77 insertions(+), 50 deletions(-)

[...]

> +
> +/* Note that interrupts must be enabled when calling this function. */
> +int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
> +			  void **p)
> +{
> +	int i;
> +	struct obj_cgroup *objcg = NULL;
> +
> +	/* memcg and kmem_cache debug support */
> +	s = slab_pre_alloc_hook(s, NULL, &objcg, size, flags);
> +	if (unlikely(!s))
> +		return false;
> +
> +	i = __kmem_cache_alloc_bulk(s, flags, size, p, objcg);
> +
> +	/*
> +	 * memcg and kmem_cache debug support and memory initialization.
> +	 * Done outside of the IRQ disabled fastpath loop.
> +	 */
> +	if (i != 0)
> +		slab_post_alloc_hook(s, objcg, flags, size, p,
> +				slab_want_init_on_alloc(flags, s));

This patch looks mostly good but wondering what happens if someone calls it with size == 0
so it does not call slab_post_alloc_hook()?

> +	return i;
>  }
>  EXPORT_SYMBOL(kmem_cache_alloc_bulk);
>  
> -- 
> 2.38.1
> 

-- 
Thanks,
Hyeonggon