On Mon, Jun 17, 2024 at 3:04 AM Vlastimil Babka <vbabka@xxxxxxx> wrote:
>
> On 6/15/24 12:59 AM, Suren Baghdasaryan wrote:
> > slab_post_alloc_hook() uses prepare_slab_obj_exts_hook() to obtain
> > slabobj_ext object. Currently the only user of slabobj_ext object in
> > this path is memory allocation profiling, therefore when it's not enabled
> > this object is not needed. This also generates a warning when compiling
> > with CONFIG_MEM_ALLOC_PROFILING=n. Move the code under this configuration
> > to fix the warning. If more slabobj_ext users appear in the future, the
> > code will have to be changed back to call prepare_slab_obj_exts_hook().
> >
> > Fixes: 4b8736964640 ("mm/slab: add allocation accounting into slab allocation and free paths")
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Closes: https://lore.kernel.org/oe-kbuild-all/202406150444.F6neSaiy-lkp@xxxxxxxxx/
> > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
>
> But it seems to me we could remove the whole #ifdef if current->alloc_tag
> (which doesn't exist with !MEM_ALLOC_PROFILING) had an access helper, or
> there was a alloc_tag_add_current() variant?
Hmm. I'll check if current->alloc_tag is the only reason for this
ifdef. If so then you are correct and we can simplify this code.
>
> > ---
> > mm/slub.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 1373ac365a46..4927edec6a8c 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -3902,7 +3902,6 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> > unsigned int orig_size)
> > {
> > unsigned int zero_size = s->object_size;
> > - struct slabobj_ext *obj_exts;
> > bool kasan_init = init;
> > size_t i;
> > gfp_t init_flags = flags & gfp_allowed_mask;
> > @@ -3945,9 +3944,11 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> > kmemleak_alloc_recursive(p[i], s->object_size, 1,
> > s->flags, init_flags);
> > kmsan_slab_alloc(s, p[i], init_flags);
> > +#ifdef CONFIG_MEM_ALLOC_PROFILING
> > if (need_slab_obj_ext()) {
> > + struct slabobj_ext *obj_exts;
> > +
> > obj_exts = prepare_slab_obj_exts_hook(s, flags, p[i]);
> > -#ifdef CONFIG_MEM_ALLOC_PROFILING
> > /*
> > * Currently obj_exts is used only for allocation profiling.
> > * If other users appear then mem_alloc_profiling_enabled()
> > @@ -3955,8 +3956,8 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
> > */
> > if (likely(obj_exts))
> > alloc_tag_add(&obj_exts->ref, current->alloc_tag, s->size);
> > -#endif
> > }
> > +#endif
> > }
> >
> > return memcg_slab_post_alloc_hook(s, lru, flags, size, p);
> >
> > base-commit: c286c21ff94252f778515b21b6bebe749454a852
>
