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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782355234; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=TFbcmBSmgNQkGD89iSSlaWPAe0b7053UYUJCgVQXiLk=; b=Qw4J2wefkNJOAExdPFGyxaTMgtXgBzTr722Flb8xhkSDGUJm7UvAmHafV2GjCODdKFuKFy 0cJILD3wBDJktkBnc5QJezEOZoulpRHoQ4MPI4xe6gSxhjK57+SlZ/Y2xEJOqtE9D5O7K/ Gw0MMj1jAUVTODaLDTMR1DPg0VYyre4= From: Hui Zhu To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hui Zhu Subject: [PATCH v3] mm: assert exclusive nid/zonenum bits at the page/folio access sites Date: Thu, 25 Jun 2026 10:40:19 +0800 Message-ID: <20260625024019.838786-1-hui.zhu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 441F7A0002 X-Rspam-User: X-Stat-Signature: 9kyqfe6z1ma4habwirmfr3chxczo5an7 X-HE-Tag: 1782355238-823399 X-HE-Meta: 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 CYD4OU65 lWlDLrLw/MTaZrRx9ufD6iZF6GFRua2vz7/FYog3KhFbNa08qZsWlISGizU5Z4wntd8BSsIPRCCkjgdtekK7oBYD8vNL6a421JGN7et4+kEgAteI1Ssj3BtirJUUahSxuvuhX+e4ZvF5UsBhP8sUkoq8SvatvuFetdDU9uZW43yln7YfnI8PtBPYh79Q/7QA5drSUMh8MfNLHnDhn1QziY07zf9C1B9dog7Cba0FuMaX9DAZ+Z0VQKzp6VA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Hui Zhu KCSAN reports a data race between page_to_nid()/folio_pgdat() reading page->flags and folio_trylock()/folio_lock() concurrently doing test_and_set_bit_lock(PG_locked, ...) on the same word, e.g.: BUG: KCSAN: data-race in __lruvec_stat_mod_folio / shmem_get_folio_gfp The node id and zone id occupy fixed bit-ranges of page->flags that are set once at page init and never modified afterwards, so they can never overlap with the low PG_locked/PG_waiters bits touched by the folio lock path. ASSERT_EXCLUSIVE_BITS(mdf.f, ...) inside memdesc_nid()/memdesc_zonenum() checks a by-value copy of the flags word, not the actual shared page->flags/folio->flags being modified concurrently, so it doesn't reliably assert anything about the real race. Move the assertion to page_to_nid(), folio_nid(), page_zonenum() and folio_zonenum(), where flags is dereferenced directly from the page/folio. Signed-off-by: Hui Zhu --- Changelog: v3: According to the comments of Andrew and Sashiko, move ASSERT_EXCLUSIVE_BITS out of memdesc_nid()/memdesc_zonenum() into the page/folio call sites. v2: According to the comments of David, remove useless comments and use ASSERT_EXCLUSIVE_BITS() in memdesc_nid() instead of data_race() in page_to_nid(). include/linux/mm.h | 4 ++++ include/linux/mmzone.h | 3 ++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 485df9c2dbdd..734e9de8f4ce 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2296,11 +2296,15 @@ static inline int memdesc_nid(memdesc_flags_t mdf) static inline int page_to_nid(const struct page *page) { + ASSERT_EXCLUSIVE_BITS(PF_POISONED_CHECK(page)->flags, + NODES_MASK << NODES_PGSHIFT); return memdesc_nid(PF_POISONED_CHECK(page)->flags); } static inline int folio_nid(const struct folio *folio) { + ASSERT_EXCLUSIVE_BITS(folio->flags, + NODES_MASK << NODES_PGSHIFT); return memdesc_nid(folio->flags); } diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index ca2712187147..56dffa966343 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1274,17 +1274,18 @@ static inline bool zone_is_empty(const struct zone *zone) static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags) { - ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT); return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK; } static inline enum zone_type page_zonenum(const struct page *page) { + ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT); return memdesc_zonenum(page->flags); } static inline enum zone_type folio_zonenum(const struct folio *folio) { + ASSERT_EXCLUSIVE_BITS(folio->flags, ZONES_MASK << ZONES_PGSHIFT); return memdesc_zonenum(folio->flags); } -- 2.43.0