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bh=ic9L3BJoSROKa6Eya4cGtNIhuOcX34TSYVnxCMS4B9o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Xr9h2++raMozjYdGXpFqN2gCSk96HdB3ot+KlijzrEGE42ZRLqDPiC+Pz1uTR8aka +DTFtoD1Hj0Oo3slfFTxuJzgkIb7voJ/yvJ88Bku6Yy9jMxdoSSIt1cmwKUAkTZ9IT z9niXhL88bcEoTgvlXWvrrm5ww7iGF+VauPtECwfKTcjdGn6dBwbIZvpBhjXTFKf23 1QCY77D4xbkGX305jAD//bJuZ+957FEQMXXHnCHfdJkhQPCNVAl5G8p4iJWGv0TQou GsBmGGPCIi8tQhlDHb9Vv0QN5hqJS/xL6xodafApcD5J95vcYXjtLwWNYcftKh4KVM 2lGi2pj8YVrvw== From: SJ Park To: Gregory Price Cc: SJ Park , linux-mm@kvack.org, damon@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, vbabka@kernel.org, jannh@google.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com Subject: Re: [PATCH 1/4] mm/damon: defensively skip zone device folios in damon_get_folio() Date: Tue, 28 Jul 2026 17:50:36 -0700 Message-ID: <20260729005036.98063-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260728194714.3713735-2-gourry@gourry.net> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 30EF840004 X-Stat-Signature: wzir8ggd6c9nmteku5m76rnzij4a3e7a X-Rspam-User: X-HE-Tag: 1785286251-663784 X-HE-Meta: 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 ZeGY0M4r v6H1lt/2P6KSAUaWfQj4+FnwEyxluJwhRMZBthJMwA62H5IR/xd2GFTIasnIL4EM7Sv2XxJX1BLACbReiEhRvBNYWoLHW48KCgy5RoixRTbIWfhlWLv1482QunQCtpTFVOgww+0C4HATbMy81PF6gm8IMueC9osxl7w84uSei5cANzxy28eVXhuWfc9qsNG9FORRngFMgm9AaDt6ZwpNsgeJ2WRT5oytKHTF9fpeaGC4tm7FR0mZMrxHK3haQ6sWjrHDx/0vfR7Pf4qOKnd9hYKQptZ46zwsEGJ+yv6OJ3N0Dnh51weDMiYEbuIoDjncDuEmOAzYM5s1i0ZW+sqtu45O2JFmtqGcNFdjG7QjCaSH17oEGB6+rEkBt5rIxgPR90pY3cQvTUxtQzMc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Gregory, On Tue, 28 Jul 2026 15:47:11 -0400 Gregory Price wrote: > All DAMON physical- and virtual-address operations obtain their folios > through damon_get_folio(). That helper already excludes ZONE_DEVICE > memory implicitly via pfn_to_online_page() and folio_test_lru(), but > this is inconsistent with other callers in mm/ which test explicitly. > > Add an explicit folio_is_zone_device() rejection in damon_get_folio() > so the guarantee lives in one place and covers every caller uniformly, > consistent with other mm walkers that reject zone device folios. Thank you for checking this and sharing this nice patch! However, I'm not very sure adding a call that not really required for only making it looks consistent with others is the right choice. I'm especially concerned if this will confuse future readers including myself. If this is a hardening purpose, we have CONFIG_DAMON_DEBUG_SANITY for the purpose. What about using it with a good comment explaining why we doing that? Thanks, SJ [...]