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Fri, 02 Oct 2020 10:26:07 -0700 Received: from intmgw001.06.prn3.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:11d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Fri, 2 Oct 2020 10:26:05 -0700 Received: by devvm1755.vll0.facebook.com (Postfix, from userid 111017) id BC3B7F1529F; Fri, 2 Oct 2020 10:26:00 -0700 (PDT) From: Roman Gushchin To: Andrew Morton CC: Shakeel Butt , Johannes Weiner , Michal Hocko , , , , Roman Gushchin Subject: [PATCH v5 2/4] mm: memcontrol/slab: use helpers to access slab page's memcg_data Date: Fri, 2 Oct 2020 10:25:57 -0700 Message-ID: <20201002172559.4000748-3-guro@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20201002172559.4000748-1-guro@fb.com> References: <20201002172559.4000748-1-guro@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-10-02_11:2020-10-02,2020-10-02 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 mlxlogscore=817 spamscore=0 mlxscore=0 clxscore=1015 bulkscore=0 suspectscore=2 phishscore=0 priorityscore=1501 impostorscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2010020129 X-FB-Internal: deliver X-Bogosity: Ham, tests=bogofilter, spamicity=0.045830, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: To gather all direct accesses to struct page's memcg_data field in one place, let's introduce 3 new helpers to use in the slab accounting code: struct obj_cgroup **page_objcgs(struct page *page); struct obj_cgroup **page_objcgs_check(struct page *page); bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs); They are similar to the corresponding API for generic pages, except that the setter can return false, indicating that the value has been already set from a different thread. Signed-off-by: Roman Gushchin Acked-by: Johannes Weiner --- include/linux/memcontrol.h | 64 ++++++++++++++++++++++++++++++++++++++ mm/memcontrol.c | 6 ++-- mm/slab.h | 35 +++++---------------- 3 files changed, 75 insertions(+), 30 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index f95c1433461c..c7ac0a5b8989 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -416,6 +416,70 @@ static inline struct mem_cgroup *page_memcg_check(st= ruct page *page) return (struct mem_cgroup *)memcg_data; } =20 +#ifdef CONFIG_MEMCG_KMEM +/* + * page_objcgs - get the object cgroups vector associated with a page + * @page: a pointer to the page struct + * + * Returns a pointer to the object cgroups vector associated with the pa= ge, + * or NULL. This function assumes that the page is known to have an + * associated object cgroups vector. It's not safe to call this function + * against pages, which might have an associated memory cgroup: e.g. + * kernel stack pages. + */ +static inline struct obj_cgroup **page_objcgs(struct page *page) +{ + return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL); +} + +/* + * page_objcgs_check - get the object cgroups vector associated with a p= age + * @page: a pointer to the page struct + * + * Returns a pointer to the object cgroups vector associated with the pa= ge, + * or NULL. This function is safe to use if the page can be directly ass= ociated + * with a memory cgroup. + */ +static inline struct obj_cgroup **page_objcgs_check(struct page *page) +{ + unsigned long memcg_data =3D READ_ONCE(page->memcg_data); + + if (memcg_data && (memcg_data & 0x1UL)) + return (struct obj_cgroup **)(memcg_data & ~0x1UL); + + return NULL; +} + +/* + * set_page_objcgs - associate a page with a object cgroups vector + * @page: a pointer to the page struct + * @objcgs: a pointer to the object cgroups vector + * + * Atomically associates a page with a vector of object cgroups. + */ +static inline bool set_page_objcgs(struct page *page, + struct obj_cgroup **objcgs) +{ + return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL); +} +#else +static inline struct obj_cgroup **page_objcgs(struct page *page) +{ + return NULL; +} + +static inline struct obj_cgroup **page_objcgs_check(struct page *page) +{ + return NULL; +} + +static inline bool set_page_objcgs(struct page *page, + struct obj_cgroup **objcgs) +{ + return true; +} +#endif + static __always_inline bool memcg_stat_item_in_bytes(int idx) { if (idx =3D=3D MEMCG_PERCPU_B) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c2e6c75ed988..a8eb20283dcd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2899,7 +2899,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page,= struct kmem_cache *s, if (!vec) return -ENOMEM; =20 - if (cmpxchg(&page->memcg_data, 0, (unsigned long)vec | 0x1UL)) + if (!set_page_objcgs(page, vec)) kfree(vec); else kmemleak_not_leak(vec); @@ -2933,12 +2933,12 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p) * Memcg membership data for each individual object is saved in * the page->obj_cgroups. */ - if (page_has_obj_cgroups(page)) { + if (page_objcgs_check(page)) { struct obj_cgroup *objcg; unsigned int off; =20 off =3D obj_to_index(page->slab_cache, page, p); - objcg =3D page_obj_cgroups(page)[off]; + objcg =3D page_objcgs(page)[off]; if (objcg) return obj_cgroup_memcg(objcg); =20 diff --git a/mm/slab.h b/mm/slab.h index 5ac89260f329..9b70d30d21c7 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -239,28 +239,12 @@ static inline bool kmem_cache_debug_flags(struct km= em_cache *s, slab_flags_t fla } =20 #ifdef CONFIG_MEMCG_KMEM -static inline struct obj_cgroup **page_obj_cgroups(struct page *page) -{ - /* - * Page's memory cgroup and obj_cgroups vector are sharing the same - * space. To distinguish between them in case we don't know for sure - * that the page is a slab page (e.g. page_cgroup_ino()), let's - * always set the lowest bit of obj_cgroups. - */ - return (struct obj_cgroup **)(page->memcg_data & ~0x1UL); -} - -static inline bool page_has_obj_cgroups(struct page *page) -{ - return page->memcg_data & 0x1UL; -} - int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s= , gfp_t gfp); =20 static inline void memcg_free_page_obj_cgroups(struct page *page) { - kfree(page_obj_cgroups(page)); + kfree(page_objcgs(page)); page->memcg_data =3D 0; } =20 @@ -322,7 +306,7 @@ static inline void memcg_slab_post_alloc_hook(struct = kmem_cache *s, if (likely(p[i])) { page =3D virt_to_head_page(p[i]); =20 - if (!page_has_obj_cgroups(page) && + if (!page_objcgs(page) && memcg_alloc_page_obj_cgroups(page, s, flags)) { obj_cgroup_uncharge(objcg, obj_full_size(s)); continue; @@ -330,7 +314,7 @@ static inline void memcg_slab_post_alloc_hook(struct = kmem_cache *s, =20 off =3D obj_to_index(s, page, p[i]); obj_cgroup_get(objcg); - page_obj_cgroups(page)[off] =3D objcg; + page_objcgs(page)[off] =3D objcg; mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s), obj_full_size(s)); } else { @@ -343,18 +327,20 @@ static inline void memcg_slab_post_alloc_hook(struc= t kmem_cache *s, static inline void memcg_slab_free_hook(struct kmem_cache *s, struct pag= e *page, void *p) { + struct obj_cgroup **objcgs; struct obj_cgroup *objcg; unsigned int off; =20 if (!memcg_kmem_enabled()) return; =20 - if (!page_has_obj_cgroups(page)) + objcgs =3D page_objcgs(page); + if (!objcgs) return; =20 off =3D obj_to_index(s, page, p); - objcg =3D page_obj_cgroups(page)[off]; - page_obj_cgroups(page)[off] =3D NULL; + objcg =3D objcgs[off]; + objcgs[off] =3D NULL; =20 if (!objcg) return; @@ -367,11 +353,6 @@ static inline void memcg_slab_free_hook(struct kmem_= cache *s, struct page *page, } =20 #else /* CONFIG_MEMCG_KMEM */ -static inline bool page_has_obj_cgroups(struct page *page) -{ - return false; -} - static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr) { return NULL; --=20 2.26.2