Re: [PATCH 2/3] mm, slab: use an enum to define SLAB_ cache creation flags

[Roman Gushchin]

On Tue, Feb 20, 2024 at 05:58:26PM +0100, Vlastimil Babka wrote:
> The values of SLAB_ cache creation flagsare defined by hand, which is
> tedious and error-prone. Use an enum to assign the bit number and a
> __SF_BIT() macro to #define the final flags.
> 
> This renumbers the flag values, which is OK as they are only used
> internally.
> 
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
>  include/linux/slab.h | 81 ++++++++++++++++++++++++++++++++++++++--------------
>  mm/slub.c            |  6 ++--
>  2 files changed, 63 insertions(+), 24 deletions(-)
> 
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 6252f44115c2..f893a132dd5a 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -21,29 +21,68 @@
>  #include <linux/cleanup.h>
>  #include <linux/hash.h>
>  
> +enum _slab_flag_bits {
> +	_SLAB_CONSISTENCY_CHECKS,
> +	_SLAB_RED_ZONE,
> +	_SLAB_POISON,
> +	_SLAB_KMALLOC,
> +	_SLAB_HWCACHE_ALIGN,
> +	_SLAB_CACHE_DMA,
> +	_SLAB_CACHE_DMA32,
> +	_SLAB_STORE_USER,
> +	_SLAB_PANIC,
> +	_SLAB_TYPESAFE_BY_RCU,
> +	_SLAB_TRACE,
> +#ifdef CONFIG_DEBUG_OBJECTS
> +	_SLAB_DEBUG_OBJECTS,
> +#endif
> +	_SLAB_NOLEAKTRACE,
> +	_SLAB_NO_MERGE,
> +#ifdef CONFIG_FAILSLAB
> +	_SLAB_FAILSLAB,
> +#endif
> +#ifdef CONFIG_MEMCG_KMEM
> +	_SLAB_ACCOUNT,
> +#endif
> +#ifdef CONFIG_KASAN_GENERIC
> +	_SLAB_KASAN,
> +#endif
> +	_SLAB_NO_USER_FLAGS,
> +#ifdef CONFIG_KFENCE
> +	_SLAB_SKIP_KFENCE,
> +#endif
> +#ifndef CONFIG_SLUB_TINY
> +	_SLAB_RECLAIM_ACCOUNT,
> +#endif
> +	_SLAB_OBJECT_POISON,
> +	_SLAB_CMPXCHG_DOUBLE,
> +	_SLAB_FLAGS_LAST_BIT
> +};
> +
> +#define __SF_BIT(nr)	((slab_flags_t __force)(1U << (nr)))

I'd rename it to (__)SLAB_FLAG_BIT(), as SF is a bit cryptic, but not a strong
preference. Otherwise looks really good to me, nice cleanup.

Reviewed-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>

Thanks!