linux-kernel - Re: [PATCH V6 8/9] mm/slab: move [__]ksize and slab

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Message-ID: <2cdff2ed-a45d-47e9-94ef-f8ecd178bbae@suse.cz>
Date: Tue, 13 Jan 2026 13:44:45 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Harry Yoo <harry.yoo@...cle.com>, akpm@...ux-foundation.org
Cc: andreyknvl@...il.com, cl@...two.org, dvyukov@...gle.com,
 glider@...gle.com, hannes@...xchg.org, linux-mm@...ck.org,
 mhocko@...nel.org, muchun.song@...ux.dev, rientjes@...gle.com,
 roman.gushchin@...ux.dev, ryabinin.a.a@...il.com, shakeel.butt@...ux.dev,
 surenb@...gle.com, vincenzo.frascino@....com, yeoreum.yun@....com,
 tytso@....edu, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, hao.li@...ux.dev
Subject: Re: [PATCH V6 8/9] mm/slab: move [__]ksize and slab_ksize() to
 mm/slub.c

On 1/13/26 7:18 AM, Harry Yoo wrote:
> To access SLUB's internal implementation details beyond cache flags in
> ksize(), move __ksize(), ksize(), and slab_ksize() to mm/slub.c.
> 
> Signed-off-by: Harry Yoo <harry.yoo@...cle.com>
> ---
>  mm/slab.h        | 25 --------------
>  mm/slab_common.c | 61 ----------------------------------
>  mm/slub.c        | 86 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 86 insertions(+), 86 deletions(-)
> 
> diff --git a/mm/slab.h b/mm/slab.h
> index 5176c762ec7c..957586d68b3c 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -665,31 +665,6 @@ void kvfree_rcu_cb(struct rcu_head *head);
>  
>  size_t __ksize(const void *objp);
>  
> -static inline size_t slab_ksize(const struct kmem_cache *s)
> -{
> -#ifdef CONFIG_SLUB_DEBUG
> -	/*
> -	 * Debugging requires use of the padding between object
> -	 * and whatever may come after it.
> -	 */
> -	if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
> -		return s->object_size;
> -#endif
> -	if (s->flags & SLAB_KASAN)
> -		return s->object_size;
> -	/*
> -	 * If we have the need to store the freelist pointer
> -	 * back there or track user information then we can
> -	 * only use the space before that information.
> -	 */
> -	if (s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_STORE_USER))
> -		return s->inuse;
> -	/*
> -	 * Else we can use all the padding etc for the allocation
> -	 */
> -	return s->size;
> -}
> -
>  static inline unsigned int large_kmalloc_order(const struct page *page)
>  {
>  	return page[1].flags.f & 0xff;
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index c4cf9ed2ec92..aed91fd6fd10 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -983,43 +983,6 @@ void __init create_kmalloc_caches(void)
>  						       0, SLAB_NO_MERGE, NULL);
>  }
>  
> -/**
> - * __ksize -- Report full size of underlying allocation
> - * @object: pointer to the object
> - *
> - * This should only be used internally to query the true size of allocations.
> - * It is not meant to be a way to discover the usable size of an allocation
> - * after the fact. Instead, use kmalloc_size_roundup(). Using memory beyond
> - * the originally requested allocation size may trigger KASAN, UBSAN_BOUNDS,
> - * and/or FORTIFY_SOURCE.
> - *
> - * Return: size of the actual memory used by @object in bytes
> - */
> -size_t __ksize(const void *object)

Think it could be also static and not in slab.h? I'll make that change
locally.