On 11/22/22 06:30, Feng Tang wrote: > 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@xxxxxxxxx> 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. You could try mm/slab.h instead, below the slub_def.h includes there. is_kmalloc_cache(s) shouldn't have random consumers in the kernel anyway. It's fine if kasan includes it, as it's intertwined with slab a lot anyway. > 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 :) Can't agree more :) >> 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? The overhead of function call between compilation units (sans LTO) is not worth it. > 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 > */