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Thu, 12 Nov 2020 14:26:29 -0800 Received: from intmgw004.06.prn3.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Thu, 12 Nov 2020 14:26:27 -0800 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id C59CFA7D1CF; Thu, 12 Nov 2020 14:16:00 -0800 (PST) From: Roman Gushchin To: CC: Alexei Starovoitov , Daniel Borkmann , , Andrii Nakryiko , Shakeel Butt , , , , Roman Gushchin , Johannes Weiner , Michal Hocko , Andrew Morton , Stephen Rothwell Subject: [PATCH bpf-next v5 03/34] mm: introduce page memcg flags Date: Thu, 12 Nov 2020 14:15:12 -0800 Message-ID: <20201112221543.3621014-4-guro@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20201112221543.3621014-1-guro@fb.com> References: <20201112221543.3621014-1-guro@fb.com> X-FB-Internal: Safe Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-12_14:2020-11-12,2020-11-12 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 mlxlogscore=602 adultscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=1 impostorscore=0 malwarescore=0 phishscore=0 clxscore=1015 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011120127 X-FB-Internal: deliver X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The lowest bit in page->memcg_data is used to distinguish between struct memory_cgroup pointer and a pointer to a objcgs array. All checks and modifications of this bit are open-coded. Let's formalize it using page memcg flags, defined in enum page_memcg_data_flags. Additional flags might be added later. Link: https://lkml.kernel.org/r/20201027001657.3398190-4-guro@fb.com Signed-off-by: Roman Gushchin Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell --- include/linux/memcontrol.h | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index c7ac0a5b8989..99a4841d658b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -343,6 +343,15 @@ struct mem_cgroup { =20 extern struct mem_cgroup *root_mem_cgroup; =20 +enum page_memcg_data_flags { + /* page->memcg_data is a pointer to an objcgs vector */ + MEMCG_DATA_OBJCGS =3D (1UL << 0), + /* the next bit after the last actual flag */ + __NR_MEMCG_DATA_FLAGS =3D (1UL << 1), +}; + +#define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1) + /* * page_memcg - get the memory cgroup associated with a page * @page: a pointer to the page struct @@ -404,13 +413,7 @@ static inline struct mem_cgroup *page_memcg_check(stru= ct page *page) */ unsigned long memcg_data =3D READ_ONCE(page->memcg_data); =20 - /* - * The lowest bit set means that memcg isn't a valid - * memcg pointer, but a obj_cgroups pointer. - * In this case the page is shared and doesn't belong - * to any specific memory cgroup. - */ - if (memcg_data & 0x1UL) + if (memcg_data & MEMCG_DATA_OBJCGS) return NULL; =20 return (struct mem_cgroup *)memcg_data; @@ -429,7 +432,11 @@ static inline struct mem_cgroup *page_memcg_check(stru= ct page *page) */ static inline struct obj_cgroup **page_objcgs(struct page *page) { - return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL); + unsigned long memcg_data =3D READ_ONCE(page->memcg_data); + + VM_BUG_ON_PAGE(memcg_data && !(memcg_data & MEMCG_DATA_OBJCGS), page); + + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); } =20 /* @@ -444,10 +451,10 @@ static inline struct obj_cgroup **page_objcgs_check(s= truct page *page) { unsigned long memcg_data =3D READ_ONCE(page->memcg_data); =20 - if (memcg_data && (memcg_data & 0x1UL)) - return (struct obj_cgroup **)(memcg_data & ~0x1UL); + if (!memcg_data || !(memcg_data & MEMCG_DATA_OBJCGS)) + return NULL; =20 - return NULL; + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); } =20 /* @@ -460,7 +467,8 @@ static inline struct obj_cgroup **page_objcgs_check(str= uct page *page) static inline bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs) { - return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL); + return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | + MEMCG_DATA_OBJCGS); } #else static inline struct obj_cgroup **page_objcgs(struct page *page) --=20 2.26.2