Re: [PATCH v2 04/16] mm/slab: introduce slab_alloc_context

[Hao Li]

On Wed, Jun 10, 2026 at 05:40:06PM +0200, Vlastimil Babka (SUSE) wrote:
> Similarly to page allocator's struct alloc_context, introduce a helper
> struct to hold a part of the allocation arguments. This will allow
> reducing the number of parameters in many functions of the
> implementation, and extend them easily if needed.
> 
> For now, make it hold the caller address and the originally requested
> allocation size.
> 
> Convert alloc_single_from_new_slab(), __slab_alloc_node() and
> ___slab_alloc(). No functional change intended.
> 
> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>
> ---
>  mm/slub.c | 46 +++++++++++++++++++++++++++++++++-------------
>  1 file changed, 33 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 7b48c0d38404..a3cac7281cc6 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -213,6 +213,12 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
>  static DEFINE_STATIC_KEY_FALSE(strict_numa);
>  #endif
>  
> +/* Structure holding extra parameters for slab allocations */
> +struct slab_alloc_context {
> +	unsigned long caller_addr;
> +	unsigned long orig_size;
> +};
> +
>  /* Structure holding parameters for get_from_partial() call chain */
>  struct partial_context {
>  	gfp_t flags;
> @@ -3687,7 +3693,8 @@ static inline void init_slab_obj_iter(struct kmem_cache *s, struct slab *slab,
>   * and put the slab to the partial (or full) list.
>   */
>  static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
> -					int orig_size, bool allow_spin)
> +					struct slab_alloc_context *ac,
> +					bool allow_spin)
>  {
>  	struct kmem_cache_node *n;
>  	struct slab_obj_iter iter;
> @@ -3705,7 +3712,7 @@ static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
>  	/* alloc_debug_processing() always expects a valid freepointer */
>  	set_freepointer(s, object, slab->freelist);
>  
> -	if (!alloc_debug_processing(s, slab, object, orig_size)) {
> +	if (!alloc_debug_processing(s, slab, object, ac->orig_size)) {
>  		/*
>  		 * It's not really expected that this would fail on a
>  		 * freshly allocated slab, but a concurrent memory
> @@ -4443,7 +4450,7 @@ static unsigned int alloc_from_new_slab(struct kmem_cache *s, struct slab *slab,
>   * slab.
>   */
>  static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
> -			   unsigned long addr, unsigned int orig_size)
> +			   struct slab_alloc_context *ac)
>  {
>  	bool allow_spin = gfpflags_allow_spinning(gfpflags);
>  	void *object;
> @@ -4476,7 +4483,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  			pc.flags = GFP_NOWAIT | __GFP_THISNODE;
>  	}
>  
> -	pc.orig_size = orig_size;
> +	pc.orig_size = ac->orig_size;
>  	object = get_from_partial(s, node, &pc);
>  	if (object)
>  		goto success;
> @@ -4496,7 +4503,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  	stat(s, ALLOC_SLAB);
>  
>  	if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
> -		object = alloc_single_from_new_slab(s, slab, orig_size, allow_spin);
> +		object = alloc_single_from_new_slab(s, slab, ac, allow_spin);
>  
>  		if (likely(object))
>  			goto success;
> @@ -4514,13 +4521,13 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  
>  success:
>  	if (kmem_cache_debug_flags(s, SLAB_STORE_USER))
> -		set_track(s, object, TRACK_ALLOC, addr, gfpflags);
> +		set_track(s, object, TRACK_ALLOC, ac->caller_addr, gfpflags);
>  
>  	return object;
>  }
>  
>  static void *__slab_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node,
> -			       unsigned long addr, size_t orig_size)
> +			       struct slab_alloc_context *ac)
>  {
>  	void *object;
>  
> @@ -4545,7 +4552,7 @@ static void *__slab_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node,
>  	}
>  #endif
>  
> -	object = ___slab_alloc(s, gfpflags, node, addr, orig_size);
> +	object = ___slab_alloc(s, gfpflags, node, ac);
>  
>  	return object;
>  }
> @@ -4923,8 +4930,13 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list
>  
>  	object = alloc_from_pcs(s, gfpflags, node);
>  
> -	if (unlikely(!object))
> -		object = __slab_alloc_node(s, gfpflags, node, addr, orig_size);
> +	if (unlikely(!object)) {
> +		struct slab_alloc_context ac = {
> +			.caller_addr = addr,
> +			.orig_size = orig_size,
> +		};
> +		object = __slab_alloc_node(s, gfpflags, node, &ac);
> +	}
>  
>  	maybe_wipe_obj_freeptr(s, object);
>  
> @@ -5389,13 +5401,18 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in
>  	if (ret)
>  		goto success;
>  
> +	struct slab_alloc_context ac = {
> +		.caller_addr = _RET_IP_,
> +		.orig_size = orig_size,
> +	};

It might be better to move this to the beginning of the function, to avoid
patch09 jump to `success` before ac is initialized.

> +
>  	/*
>  	 * Do not call slab_alloc_node(), since trylock mode isn't
>  	 * compatible with slab_pre_alloc_hook/should_failslab and
>  	 * kfence_alloc. Hence call __slab_alloc_node() (at most twice)
>  	 * and slab_post_alloc_hook() directly.
>  	 */
> -	ret = __slab_alloc_node(s, alloc_gfp, node, _RET_IP_, orig_size);
> +	ret = __slab_alloc_node(s, alloc_gfp, node, &ac);
>  
>  	/*
>  	 * It's possible we failed due to trylock as we preempted someone with
> @@ -7237,10 +7254,13 @@ static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
>  	int i;
>  
>  	if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
> +		struct slab_alloc_context ac = {
> +			.caller_addr = _RET_IP_,
> +			.orig_size = s->object_size,
> +		};
>  		for (i = 0; i < size; i++) {
>  
> -			p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE, _RET_IP_,
> -					     s->object_size);
> +			p[i] = ___slab_alloc(s, flags, NUMA_NO_NODE, &ac);
>  			if (unlikely(!p[i]))
>  				goto error;
>  
> 
> -- 
> 2.54.0
>