On Fri, Feb 16, 2024 at 6:39 PM Vlastimil Babka <vbabka@xxxxxxx> wrote: > > On 2/12/24 22:39, Suren Baghdasaryan wrote: > > objext objects are created with __GFP_NO_OBJ_EXT flag and therefore have > > no corresponding objext themselves (otherwise we would get an infinite > > recursion). When freeing these objects their codetag will be empty and > > when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled this will lead to false > > warnings. Introduce CODETAG_EMPTY special codetag value to mark > > allocations which intentionally lack codetag to avoid these warnings. > > Set objext codetags to CODETAG_EMPTY before freeing to indicate that > > the codetag is expected to be empty. > > > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> > > --- > > include/linux/alloc_tag.h | 26 ++++++++++++++++++++++++++ > > mm/slab.h | 25 +++++++++++++++++++++++++ > > mm/slab_common.c | 1 + > > mm/slub.c | 8 ++++++++ > > 4 files changed, 60 insertions(+) > > > > diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h > > index 0a5973c4ad77..1f3207097b03 100644 > > ... > > > index c4bd0d5348cb..cf332a839bf4 100644 > > --- a/mm/slab.h > > +++ b/mm/slab.h > > @@ -567,6 +567,31 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab) > > int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > > gfp_t gfp, bool new_slab); > > > > + > > +#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG > > + > > +static inline void mark_objexts_empty(struct slabobj_ext *obj_exts) > > +{ > > + struct slabobj_ext *slab_exts; > > + struct slab *obj_exts_slab; > > + > > + obj_exts_slab = virt_to_slab(obj_exts); > > + slab_exts = slab_obj_exts(obj_exts_slab); > > + if (slab_exts) { > > + unsigned int offs = obj_to_index(obj_exts_slab->slab_cache, > > + obj_exts_slab, obj_exts); > > + /* codetag should be NULL */ > > + WARN_ON(slab_exts[offs].ref.ct); > > + set_codetag_empty(&slab_exts[offs].ref); > > + } > > +} > > + > > +#else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */ > > + > > +static inline void mark_objexts_empty(struct slabobj_ext *obj_exts) {} > > + > > +#endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */ > > + > > I assume with alloc_slab_obj_exts() moved to slub.c, mark_objexts_empty() > could move there too. No, I think mark_objexts_empty() belongs here. This patch introduced the function and uses it. Makes sense to me to keep it all together. > > > static inline bool need_slab_obj_ext(void) > > { > > #ifdef CONFIG_MEM_ALLOC_PROFILING > > diff --git a/mm/slab_common.c b/mm/slab_common.c > > index 21b0b9e9cd9e..d5f75d04ced2 100644 > > --- a/mm/slab_common.c > > +++ b/mm/slab_common.c > > @@ -242,6 +242,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > > * assign slabobj_exts in parallel. In this case the existing > > * objcg vector should be reused. > > */ > > + mark_objexts_empty(vec); > > kfree(vec); > > return 0; > > } > > diff --git a/mm/slub.c b/mm/slub.c > > index 4d480784942e..1136ff18b4fe 100644 > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -1890,6 +1890,14 @@ static inline void free_slab_obj_exts(struct slab *slab) > > if (!obj_exts) > > return; > > > > + /* > > + * obj_exts was created with __GFP_NO_OBJ_EXT flag, therefore its > > + * corresponding extension will be NULL. alloc_tag_sub() will throw a > > + * warning if slab has extensions but the extension of an object is > > + * NULL, therefore replace NULL with CODETAG_EMPTY to indicate that > > + * the extension for obj_exts is expected to be NULL. > > + */ > > + mark_objexts_empty(obj_exts); > > kfree(obj_exts); > > slab->obj_exts = 0; > > } >