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Message-ID: <Y3xeYF5NipSbBFSZ@feng-clx>
Date: Tue, 22 Nov 2022 13:30:19 +0800
From: Feng Tang <feng.tang@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>,
"Pekka Enberg" <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
"Joonsoo Kim" <iamjoonsoo.kim@....com>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Hyeonggon Yoo <42.hyeyoo@...il.com>,
Andrey Konovalov <andreyknvl@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
Alexander Potapenko <glider@...gle.com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
<linux-mm@...ck.org>, <kasan-dev@...glegroups.com>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next 1/2] mm/slab: add is_kmalloc_cache() helper macro
On Mon, Nov 21, 2022 at 12:19:38PM -0800, Andrew Morton wrote:
> On Mon, 21 Nov 2022 21:50:23 +0800 Feng Tang <feng.tang@...el.com> wrote:
>
> > +#ifndef CONFIG_SLOB
> > +#define is_kmalloc_cache(s) ((s)->flags & SLAB_KMALLOC)
> > +#else
> > +#define is_kmalloc_cache(s) (false)
> > +#endif
>
> Could be implemented as a static inline C function, yes?
Right, I also did try inline function first, and met compilation error:
"
./include/linux/slab.h: In function ‘is_kmalloc_cache’:
./include/linux/slab.h:159:18: error: invalid use of undefined type ‘struct kmem_cache’
159 | return (s->flags & SLAB_KMALLOC);
| ^~
"
The reason is 'struct kmem_cache' definition for slab/slub/slob sit
separately in slab_def.h, slub_def.h and mm/slab.h, and they are not
included in this 'include/linux/slab.h'. So I chose the macro way.
Btw, I've worked on some patches related with sl[auo]b recently, and
really felt the pain when dealing with 3 allocators, on both reading
code and writing patches. And I really like the idea of fading away
SLOB as the first step :)
> If so, that's always best. For (silly) example, consider the behaviour
> of
>
> x = is_kmalloc_cache(s++);
>
> with and without CONFIG_SLOB.
Another solution I can think of is putting the implementation into
slab_common.c, like the below?
Thanks,
Feng
---
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 067f0e80be9e..e4fcdbfb3477 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -149,6 +149,17 @@
struct list_lru;
struct mem_cgroup;
+
+#ifndef CONFIG_SLOB
+extern bool is_kmalloc_cache(struct kmem_cache *s);
+#else
+static inline bool is_kmalloc_cache(struct kmem_cache *s)
+{
+ return false;
+}
+#endif
+
/*
* struct kmem_cache related prototypes
*/
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a5480d67f391..860e804b7c0a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -77,6 +77,13 @@ __setup_param("slub_merge", slub_merge, setup_slab_merge, 0);
__setup("slab_nomerge", setup_slab_nomerge);
__setup("slab_merge", setup_slab_merge);
+#ifndef CONFIG_SLOB
+bool is_kmalloc_cache(struct kmem_cache *s)
+{
+ return (s->flags & SLAB_KMALLOC);
+}
+#endif
+
/*
* Determine the size of a slab object
*/
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