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Thu, 11 Jan 2024 23:43:15 -0800 (PST) MIME-Version: 1.0 References: <1eeadcc6-8c6a-4ba6-ab2f-1ec3b5d4730e@moroto.mountain> In-Reply-To: <1eeadcc6-8c6a-4ba6-ab2f-1ec3b5d4730e@moroto.mountain> From: Yu Zhao Date: Fri, 12 Jan 2024 00:42:37 -0700 Message-ID: Subject: Re: [bug report] mm/mglru: fix underprotected page cache To: Dan Carpenter Cc: linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: mugkkmheeqyawdwy8x17neyinsxq4oie X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: BFB71C0008 X-Rspam-User: X-HE-Tag: 1705045396-962825 X-HE-Meta: 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 EyrNlPs6 c9+vD/09dKXZPZVwxtGIOPCPkGXxsJxJLNaqUJi5RePWuauYzd/E5bd6xItZh0Qb7gaYHyIQFzpKs/MD1l36AYjU5M+76U1QPFtl9ECbTulrKnZktjLYWX6nVkNqrK01Hpo6uliJUAso6L4wYi/4P0vsSqW94bUTVmY4GoauXD6EhiUykyb9OATTZqTuSWsUykE9YTikmrJDfJH1pddqsHrNXQihSEADU+bBmd+JuAWMBfX1+fQEkMwAgZBetIdTFLm3DMgbKbX8VE62xWW343Peuzw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.080691, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jan 12, 2024 at 12:13=E2=80=AFAM Dan Carpenter wrote: > > Hello Yu Zhao, > > The patch 081488051d28: "mm/mglru: fix underprotected page cache" > from Dec 7, 2023 (linux-next), leads to the following Smatch static > checker warning: > > mm/workingset.c:318 lru_gen_refault() > warn: always true condition '(refs >=3D ((((1))) << (__builtin_ch= oose_expr((4 =3D=3D 4), (((2) < (64 - 26 - 3 - 3 - 0 - 10 - 0 - (8 + 14))) = ?(2):(64 - 26 - 3 - 3 - 0 - 10 - 0 - (8 + 14))), ))) - 1) =3D> (s32min-s32m= ax >=3D 0)' > > mm/workingset.c > 308 atomic_long_add(delta, &lrugen->refaulted[hist][type][tie= r]); > 309 mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type,= delta); > 310 > 311 /* > 312 * Count the following two cases as stalls: > 313 * 1. For pages accessed through page tables, hotter page= s pushed out > 314 * hot pages which refaulted immediately. > 315 * 2. For pages accessed multiple times through file desc= riptors, > 316 * they would have been protected by sort_folio(). > 317 */ > --> 318 if (lru_gen_in_fault() || refs >=3D BIT(LRU_REFS_WIDTH) -= 1) { > ^^^^^^^^^^^^^^^^^^^^^^^ > In my x86 allmodconfig this is zero and refs is always >=3D 0. This coul= d > be intentional, but I thought it was worth checking. Appreciate the manual work! This indeed is intentional if LRU_REFS_WIDTH is 0. What would be the best way to suppress this warning?