Re: [PATCH V1 1/2] mm/slab: factor out slab_args_unmergeable()

[Vlastimil Babka <vbabka@suse.cz>]

On 1/27/26 11:31, Harry Yoo wrote:
> slab_mergeable() determines whether a slab cache can be merged, but it
> should not be used when the cache is not fully created yet.
> 
> Extract the pre-cache-creation mergeability checks into
> slab_args_unmergeable(), which evaluates kmem_cache_args, slab flags,
> and slab_nomerge to determine if a cache will be mergeable before it is
> created.
> 
> Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
> ---
>  mm/slab_common.c | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 2e80d323f550..904414c3ebb8 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -174,24 +174,32 @@ int slab_unmergeable(struct kmem_cache *s)
>  	return 0;
>  }
>  
> -static struct kmem_cache *find_mergeable(unsigned int size, slab_flags_t flags,
> -		const char *name, struct kmem_cache_args *args)
> +static bool slab_args_unmergeable(struct kmem_cache_args *args,
> +				  slab_flags_t flags)
>  {
> -	struct kmem_cache *s;
> -	unsigned int align;
> -
>  	if (slab_nomerge)
> -		return NULL;
> +		return true;

I think this still logically belongs to find_mergeable() and not here, so
moved there. Agreed?

>  	if (args->ctor)
> -		return NULL;
> +		return true;
>  
>  	if (IS_ENABLED(CONFIG_HARDENED_USERCOPY) && args->usersize)
> -		return NULL;
> -
> -	flags = kmem_cache_flags(flags, name);
> +		return true;
>  
>  	if (flags & SLAB_NEVER_MERGE)
> +		return true;
> +
> +	return false;
> +}
> +
> +static struct kmem_cache *find_mergeable(unsigned int size, slab_flags_t flags,
> +		const char *name, struct kmem_cache_args *args)
> +{
> +	struct kmem_cache *s;
> +	unsigned int align;
> +
> +	flags = kmem_cache_flags(flags, name);
> +	if (slab_args_unmergeable(args, flags))
>  		return NULL;
>  
>  	size = ALIGN(size, sizeof(void *));