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. > 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; > }