linux-kernel - Re: [PATCH 7/9] mm, slub: introduce kmem_cache_debug

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Message-ID: <202006171055.64F6EB665@keescook>
Date:   Wed, 17 Jun 2020 10:56:42 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        vinmenon@...eaurora.org, Matthew Garrett <mjg59@...gle.com>,
        Roman Gushchin <guro@...com>, Jann Horn <jannh@...gle.com>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: Re: [PATCH 7/9] mm, slub: introduce kmem_cache_debug_flags()

On Wed, Jun 10, 2020 at 06:31:33PM +0200, Vlastimil Babka wrote:
> There are few places that call kmem_cache_debug(s) (which tests if any of debug
> flags are enabled for a cache) immediatelly followed by a test for a specific
> flag. The compiler can probably eliminate the extra check, but we can make the
> code nicer by introducing kmem_cache_debug_flags() that works like
> kmem_cache_debug() (including the static key check) but tests for specifig
> flag(s). The next patches will add more users.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/slub.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 24d3e5f832aa..c8e8b4ae2451 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -122,18 +122,28 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
>  #endif
>  #endif
>  
> -static inline int kmem_cache_debug(struct kmem_cache *s)
> +/*
> + * Returns true if any of the specified slub_debug flags is enabled for the
> + * cache. Use only for flags parsed by setup_slub_debug() as it also enables
> + * the static key.
> + */
> +static inline int kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)

This should return slab_flag_t, yes?

>  {
>  #ifdef CONFIG_SLUB_DEBUG
>  	if (static_branch_unlikely(&slub_debug_enabled))
> -		return s->flags & SLAB_DEBUG_FLAGS;
> +		return s->flags & flags;
>  #endif
>  	return 0;
>  }
>  
> +static inline int kmem_cache_debug(struct kmem_cache *s)

And this too, as long as we're making changes here.

-- 
Kees Cook