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

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Message-ID: <949b90ed-e0f0-07d7-4d21-e30ec0958a7c@suse.cz>
Date:   Thu, 18 Jun 2020 10:37:07 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     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>
Cc:     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>,
        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 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>
---
 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