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Fri, 12 Jan 2024 00:29:04 -0800 (PST) Received: from localhost ([102.140.209.237]) by smtp.gmail.com with ESMTPSA id v10-20020a5d610a000000b0033719111458sm3196086wrt.36.2024.01.12.00.29.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jan 2024 00:29:04 -0800 (PST) Date: Fri, 12 Jan 2024 11:29:00 +0300 From: Dan Carpenter To: Yu Zhao Cc: linux-mm@kvack.org Subject: Re: [bug report] mm/mglru: fix underprotected page cache Message-ID: <97228a10-45af-4db5-844b-241b7158f09c@moroto.mountain> References: <1eeadcc6-8c6a-4ba6-ab2f-1ec3b5d4730e@moroto.mountain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B0C5480011 X-Stat-Signature: u8jb37nfmrs3b4ksq7fm6is5w9xjpzfp X-HE-Tag: 1705048145-158781 X-HE-Meta: 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 l2FDZxkO MfpBfwyM+o6OFeH2i+6ttTOMWun4GFSE6mq+DMnE3X9mJG5ZNaxSjdo02n0kX0+5Azi1nE5jXe1VpAOYbxCfmXsDM45NwgC3OIG0HNonr1doL2nUtJyVG39QykkczGidXflnWTIaJDn9ViaklmI+4ijQNox956hUJ/LFyBwyNJBDRZbmj8N5EwHU9KVAVDaGvofmI57thbrBphsmcqgA9JFDalzvRPAJXHStSJbhxYpJHGQASvmKT5kHvjpCRivHhOTOSTU83EyY5kQm773OzUEIScer47n/nekRPTIQ4p57cCPAnXC4W1KC+JwyJGxb9x0YSC6zDOj4x+LQqTxL64NkfeOTCIXsFrulz2NGG03itie0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.019763, 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 12:42:37AM -0700, Yu Zhao wrote: > On Fri, Jan 12, 2024 at 12:13 AM 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 >= ((((1))) << (__builtin_choose_expr((4 == 4), (((2) < (64 - 26 - 3 - 3 - 0 - 10 - 0 - (8 + 14))) ?(2):(64 - 26 - 3 - 3 - 0 - 10 - 0 - (8 + 14))), ))) - 1) => (s32min-s32max >= 0)' > > > > mm/workingset.c > > 308 atomic_long_add(delta, &lrugen->refaulted[hist][type][tier]); > > 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 pages pushed out > > 314 * hot pages which refaulted immediately. > > 315 * 2. For pages accessed multiple times through file descriptors, > > 316 * they would have been protected by sort_folio(). > > 317 */ > > --> 318 if (lru_gen_in_fault() || refs >= BIT(LRU_REFS_WIDTH) - 1) { > > ^^^^^^^^^^^^^^^^^^^^^^^ > > In my x86 allmodconfig this is zero and refs is always >= 0. This could > > 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? No need. These warnings are a one time thing. Ignore the false positives. If people are curious in the future they can find this conversation on lore. regards, dan carpenter