linux-kernel - Re: [PATCH] mm/slab: simplify SLAB

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Message-ID: <0fa27da8-d523-77f7-0473-bb317ec9d83e@gentwo.org>
Date: Fri, 17 Jan 2025 14:13:24 -0800 (PST)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Kevin Brodsky <kevin.brodsky@....com>
cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
    Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
    Joonsoo Kim <iamjoonsoo.kim@....com>, 
    Andrew Morton <akpm@...ux-foundation.org>, 
    Vlastimil Babka <vbabka@...e.cz>, 
    Roman Gushchin <roman.gushchin@...ux.dev>, 
    Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: Re: [PATCH] mm/slab: simplify SLAB_* flag handling

On Fri, 17 Jan 2025, Kevin Brodsky wrote:

> index a29457bef626..3b07cdaac3ae 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -305,18 +305,6 @@ struct kmem_cache *__kmem_cache_create_args(const char *name,
>  		goto out_unlock;
>  	}
>
> -	/* Refuse requests with allocator specific flags */
> -	if (flags & ~SLAB_FLAGS_PERMITTED) {
> -		err = -EINVAL;
> -		goto out_unlock;
> -	}

I think we should keep checking for invalid flags.
 -
> -	/*
> -	 * Some allocators will constraint the set of valid flags to a subset
> -	 * of all flags. We expect them to define CACHE_CREATE_MASK in this
> -	 * case, and we'll just provide them with a sanitized version of the
> -	 * passed flags.
> -	 */
>  	flags &= CACHE_CREATE_MASK;

This would silently clear some flags instead of creating an error.