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AHgh+RqUhEpdAiDG+vVwlohs+DpZ84r8OQkP02QboRDc0GvbpJJGbhUOWrdJidqJOwzAw2l0fQGXGv3xYAUXunc=@vger.kernel.org X-Gm-Message-State: AOJu0Yw19DJRgTrhSPry7+fvOM9UWu2WNvqAnAEGtpQLYHV2qXPxsEfr D+dmZWFiJSwr3sH3GGhEU6CIscEGvyH5oO4ROBxuad2K6+UjUIrxBXp4q7XDjHnLqD5Hu1JixFu oG0l1ZlpmwQDsgAt1s8G/dcK6bZmkTHhkLJgqitZU X-Gm-Gg: AfdE7ckdIe9TXq0N19dbEa5yU3cwsieOl/wmd6rE9b0ITni4nA/b1T1zKYpBew+4nXi FhJ/hQwcXMsedzxgxNv0yMLttAeBIVAWCKkIOElLx1Am14V+H1uHSbO3xn/2q1UH6xFdZhFjsJv v2DnTcNs/Hw0bufWh69ci/kz+wa68deoeN9mUkTBNdxgnC7SuJ+eK0CtT4ctGdbSE6v8fA11Kc3 RrmG0oh4+3KF4DmXbC/0GrY79vTfHMNTCAAa03EABMGPtPBdBBxlUZcuK9I X-Received: by 2002:ac8:57cb:0:b0:50e:5eba:cadd with SMTP id d75a77b69052e-51f7d272648mr4128911cf.2.1784165278136; Wed, 15 Jul 2026 18:27:58 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260715-b4-objext_split-v1-0-9a49c4ccf4c3@kernel.org> <20260715-b4-objext_split-v1-5-9a49c4ccf4c3@kernel.org> In-Reply-To: <20260715-b4-objext_split-v1-5-9a49c4ccf4c3@kernel.org> From: Suren Baghdasaryan Date: Wed, 15 Jul 2026 18:27:47 -0700 X-Gm-Features: AUfX_mw0hxBE87l_puhHNr7S0k7RJO-VLoBt5DLKGkywTu7tTOxb6OYu6XzRYSU Message-ID: Subject: Re: [PATCH RFC 05/12] mm/slab: abstract slabobj_ext.objcg access To: "Vlastimil Babka (SUSE)" Cc: Harry Yoo , Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Jul 15, 2026 at 3:11=E2=80=AFAM Vlastimil Babka (SUSE) wrote: > > In preparation for changes to the structure, abstract access to the > objcg field with a slab_obj_ext_objcgp() function. > Rename the field to _objcg to make an unexpected direct access a compile > error. > > No functional change intended. > > Signed-off-by: Vlastimil Babka (SUSE) > --- > mm/kfence/core.c | 2 +- > mm/memcontrol.c | 23 +++++++++++++++-------- > mm/slab.h | 9 ++++++++- > mm/slub.c | 2 +- > 4 files changed, 25 insertions(+), 11 deletions(-) > > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index 6577bd76954e..717e8baf7e5d 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -1249,7 +1249,7 @@ void __kfence_free(void *addr) > struct kfence_metadata *meta =3D addr_to_metadata((unsigned long)= addr); > > #ifdef CONFIG_MEMCG > - KFENCE_WARN_ON(meta->obj_exts.objcg); > + KFENCE_WARN_ON(*slab_obj_ext_objcgp(&meta->obj_exts)); > #endif > /* > * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer fr= eeing > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 4e427286a88a..6303a2b1a9d0 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2865,6 +2865,7 @@ struct mem_cgroup *mem_cgroup_from_obj_slab(struct = slab *slab, void *p) > */ > unsigned long obj_exts; > struct slabobj_ext *obj_ext; > + struct obj_cgroup *objcg; > > obj_exts =3D slab_obj_exts(slab); > if (!obj_exts) > @@ -2872,9 +2873,8 @@ struct mem_cgroup *mem_cgroup_from_obj_slab(struct = slab *slab, void *p) > > get_slab_obj_exts(obj_exts); > obj_ext =3D slab_obj_ext(slab->slab_cache, slab, obj_exts, p); > - if (obj_ext->objcg) { > - struct obj_cgroup *objcg =3D obj_ext->objcg; > - > + objcg =3D *slab_obj_ext_objcgp(obj_ext); > + if (objcg) { > put_slab_obj_exts(obj_exts); > return obj_cgroup_memcg(objcg); > } > @@ -3577,6 +3577,7 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cache= *s, struct list_lru *lru, > unsigned long obj_exts; > struct slabobj_ext *obj_ext; > struct obj_stock_pcp *stock; > + struct obj_cgroup **objcgp; > > slab =3D virt_to_slab(p[i]); > > @@ -3612,10 +3613,15 @@ bool __memcg_slab_post_alloc_hook(struct kmem_cac= he *s, struct list_lru *lru, > unlock_stock(stock); > > obj_exts =3D slab_obj_exts(slab); > + > get_slab_obj_exts(obj_exts); > + > obj_ext =3D slab_obj_ext(s, slab, obj_exts, p[i]); > + objcgp =3D slab_obj_ext_objcgp(obj_ext); > + > obj_cgroup_get(objcg); > - obj_ext->objcg =3D objcg; > + *objcgp =3D objcg; > + > put_slab_obj_exts(obj_exts); > } > > @@ -3628,16 +3634,17 @@ void __memcg_slab_free_hook(struct kmem_cache *s,= struct slab *slab, > size_t obj_size =3D obj_full_size(s); > > for (int i =3D 0; i < objects; i++) { > - struct obj_cgroup *objcg; > + struct obj_cgroup **objcgp, *objcg; > struct slabobj_ext *obj_ext; > struct obj_stock_pcp *stock; > > obj_ext =3D slab_obj_ext(s, slab, obj_exts, p[i]); > - objcg =3D obj_ext->objcg; > - if (!objcg) > + objcgp =3D slab_obj_ext_objcgp(obj_ext); > + if (!*objcgp) > continue; > > - obj_ext->objcg =3D NULL; > + objcg =3D *objcgp; > + *objcgp =3D NULL; > > stock =3D trylock_stock(); > __refill_obj_stock(objcg, stock, obj_size, true); > diff --git a/mm/slab.h b/mm/slab.h > index 36d067d6e7c0..789bd292075f 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -555,7 +555,7 @@ static inline bool need_kmalloc_no_objext(void) > */ > struct slabobj_ext { > #ifdef CONFIG_MEMCG > - struct obj_cgroup *objcg; > + struct obj_cgroup *_objcg; > #endif > #ifdef CONFIG_MEM_ALLOC_PROFILING > union codetag_ref ref; > @@ -661,6 +661,13 @@ slab_obj_ext(struct kmem_cache *s, struct slab *slab= , unsigned long obj_exts, > return kasan_reset_tag(obj_ext); > } > > +#ifdef CONFIG_MEMCG > +static inline struct obj_cgroup **slab_obj_ext_objcgp(struct slabobj_ext= *obj_ext) I understand why you need to return obj_cgroup** but maybe instead we can have a separate setter function and just return a pointer here? That would also help catch cases when someone wants to set obj_ext._objcg that was optimized away (for that the setter would need an additional parameter to identify whether we allocated optimized objext vector). > +{ > + return &obj_ext->_objcg; > +} > +#endif > + > int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, > gfp_t gfp, unsigned int alloc_flags); > > diff --git a/mm/slub.c b/mm/slub.c > index 5e3f53bcd0d3..48e10198a3ce 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2523,7 +2523,7 @@ bool memcg_slab_post_charge(void *p, gfp_t flags) > if (obj_exts) { > get_slab_obj_exts(obj_exts); > obj_ext =3D slab_obj_ext(s, slab, obj_exts, p); > - if (unlikely(obj_ext->objcg)) { > + if (unlikely(*slab_obj_ext_objcgp(obj_ext))) { > put_slab_obj_exts(obj_exts); > return true; > } > > -- > 2.55.0 >