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

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Date:   Thu, 18 Jun 2020 12:54:53 -0700
From:   Roman Gushchin <guro@...com>
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>, Kees Cook <keescook@...omium.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Vijayanand Jitta <vjitta@...eaurora.org>
Subject: Re: [PATCH 7/9] mm, slub: introduce kmem_cache_debug_flags()

On Thu, Jun 18, 2020 at 10:37:07AM +0200, Vlastimil Babka wrote:
> On 6/10/20 6:31 PM, 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>
> 
> Please add this fixup per reviews.
> ----8<----
> From 25793252a31a36f8d1d4ccf0f27ed3e43fba54d8 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@...e.cz>
> Date: Thu, 18 Jun 2020 10:34:53 +0200
> Subject: [PATCH] mm, slub: introduce kmem_cache_debug_flags()-fix
> 
> Change return from int to bool, per Kees.
> Add VM_WARN_ON_ONCE() for invalid flags, per Roman.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Roman Gushchin <guro@...com>

Thanks!

> ---
>  mm/slub.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index c8e8b4ae2451..59d19c64069e 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -127,16 +127,17 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
>   * 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)
> +static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
>  {
> +	VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS));
>  #ifdef CONFIG_SLUB_DEBUG
>  	if (static_branch_unlikely(&slub_debug_enabled))
>  		return s->flags & flags;
>  #endif
> -	return 0;
> +	return false;
>  }
>  
> -static inline int kmem_cache_debug(struct kmem_cache *s)
> +static inline bool kmem_cache_debug(struct kmem_cache *s)
>  {
>  	return kmem_cache_debug_flags(s, SLAB_DEBUG_FLAGS);
>  }
> -- 
> 2.27.0
> 
>