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SubjectRe: [PATCH v5 1/2] mm: introduce helper to check slub_debug_enabled
On Mon, Jul 05, 2021 at 04:20AM +0100, Matthew Wilcox wrote:
> On Mon, Jul 05, 2021 at 10:40:57AM +0800, yee.lee@mediatek.com wrote:
> > From: Marco Elver <elver@google.com>
> >
> > Introduce a helper to check slub_debug_enabled, so that we can confine
> > the use of #ifdef to the definition of the slub_debug_enabled_unlikely()
> > helper.
>
> We don't usually embed '_unlikely' in function names; we
> just do:
>
> static inline bool slub_debug_enabled(void)
> {
> return static_branch_unlikely(&slub_debug_enabled);
> }

The names are identical, this obviously won't work:

In file included from mm/slub.c:21:
mm/slab.h:219:20: error: ‘slub_debug_enabled’ redeclared as different kind of symbol
219 | static inline bool slub_debug_enabled(void)

But it seems that someone had the same idea, and this merge window got a
__slub_debug_enabled() with 792702911f58.

Yee, can you replace this patch with the below:

From: Marco Elver <elver@google.com>
Date: Wed, 30 Jun 2021 20:56:57 +0200
Subject: [PATCH] mm: move helper to check slub_debug_enabled

Move the helper to check slub_debug_enabled, so that we can confine
the use of #ifdef outside slub.c as well.

Signed-off-by: Marco Elver <elver@google.com>
---
v6:
* Move helper instead of introducing a new one.
---
mm/slab.h | 15 +++++++++++----
mm/slub.c | 14 --------------
2 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/mm/slab.h b/mm/slab.h
index 67e06637ff2e..f997fd5e42c8 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -216,10 +216,18 @@ DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
#endif
extern void print_tracking(struct kmem_cache *s, void *object);
long validate_slab_cache(struct kmem_cache *s);
+static inline bool __slub_debug_enabled(void)
+{
+ return static_branch_unlikely(&slub_debug_enabled);
+}
#else
static inline void print_tracking(struct kmem_cache *s, void *object)
{
}
+static inline bool __slub_debug_enabled(void)
+{
+ return false;
+}
#endif

/*
@@ -229,11 +237,10 @@ static inline void print_tracking(struct kmem_cache *s, void *object)
*/
static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
{
-#ifdef CONFIG_SLUB_DEBUG
- VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS));
- if (static_branch_unlikely(&slub_debug_enabled))
+ if (IS_ENABLED(CONFIG_SLUB_DEBUG))
+ VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS));
+ if (__slub_debug_enabled())
return s->flags & flags;
-#endif
return false;
}

diff --git a/mm/slub.c b/mm/slub.c
index 2ee43ff667a5..090fa14628f9 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -119,25 +119,11 @@
*/

#ifdef CONFIG_SLUB_DEBUG
-
#ifdef CONFIG_SLUB_DEBUG_ON
DEFINE_STATIC_KEY_TRUE(slub_debug_enabled);
#else
DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
#endif
-
-static inline bool __slub_debug_enabled(void)
-{
- return static_branch_unlikely(&slub_debug_enabled);
-}
-
-#else /* CONFIG_SLUB_DEBUG */
-
-static inline bool __slub_debug_enabled(void)
-{
- return false;
-}
-
#endif /* CONFIG_SLUB_DEBUG */

static inline bool kmem_cache_debug(struct kmem_cache *s)
--
2.32.0.93.g670b81a890-goog
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