From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1E817CDB47F for ; Thu, 25 Jun 2026 05:40:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BD5A86B0088; Thu, 25 Jun 2026 01:40:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B86A56B008A; Thu, 25 Jun 2026 01:40:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A9CE86B0092; Thu, 25 Jun 2026 01:40:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 83B146B0088 for ; Thu, 25 Jun 2026 01:40:37 -0400 (EDT) Received: from smtpin27.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 0D3F61405AE for ; Thu, 25 Jun 2026 05:40:37 +0000 (UTC) X-FDA: 84917335314.27.0D8815F Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) by imf10.hostedemail.com (Postfix) with ESMTP id BD784C0007 for ; Thu, 25 Jun 2026 05:40:33 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=r4w4yPjo; spf=pass (imf10.hostedemail.com: domain of hui.zhu@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=hui.zhu@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782366035; b=7NR3k5OCYjmCHA/NxGtPdZiJR+NKWH8sa5PnafBuKNi3w7BLZw7IFtZAoCZ+8fNQt4uGgo UxXTIxgwedf9fc91kHf02mfp9cn8giMp1l63CbpF2qWF8hABzWbwm+ppQy8MrcGnzNFnvw PM41zn8zTG1lm13EwYj1rXrcxrxDC5c= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782366035; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references:dkim-signature; bh=NkjLU/0Y0qQUoUyC3qszvMPUKNHSpAOvXGQbghzmUII=; b=bu+pzs6uN6Lq5WZy30Il7Uk0cYZSnYbzWJuIhOf4Jvs+F8ljtJD39nQUeDLx6BY2iZZnws TWpvwRa86aZWuh3zIrIMtsdQb7BG/7yl+kitISiMLVoLMS5X5n5gJR4UX9jcEcwmg4FLMQ Vw0LCAuArLZuA1UFzNOcOOTNb8CkGYU= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=r4w4yPjo; spf=pass (imf10.hostedemail.com: domain of hui.zhu@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=hui.zhu@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782366030; 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=NkjLU/0Y0qQUoUyC3qszvMPUKNHSpAOvXGQbghzmUII=; b=r4w4yPjoXtja9+iHejy8uZx7iZPZEbTrog6OMqItNVZiuU4ijvWWg/M8jGyqbC56pHNAZd s/6So9b1bqjGyc+bdrMg09BjoDXGGG+GoWJx2oR7Ldv4wlPJbyW3iFuuTsmqGCwozOVMcN 42RBO01L3OC/ZF+ycXkaZPmpyBkhrug= 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 v4] mm: assert exclusive nid/zonenum bits at the page/folio access sites Date: Thu, 25 Jun 2026 13:39:58 +0800 Message-ID: <20260625053958.918738-1-hui.zhu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 5bq1w643apyjt6nwdb6asoy3khm44prx X-Rspam-User: X-Rspamd-Queue-Id: BD784C0007 X-Rspamd-Server: rspam02 X-HE-Tag: 1782366033-121921 X-HE-Meta: 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 GOhLX7vR gbY2bSkilaUUKo9GgMnqvGZaVev+bIRLjeX7wwOTVDnFufzb14KUDZE6AfvNWbg2skUgtjJ5Eizj7tRegivUmHUfxUnrNI1kBfUORrS0WBKSwq0Ro2nqzinvVzD5uhkl11JDwRySCcnPguuPK+fxXVDz4vVmqP1xjgj/H/+eEhw9CTMfrWSOJLT/mThWsNT7OKP7pJiPGd+cssPbAv2R4VGRquQOqS24wPhiE/CTZW6SlAdt3WE6AyqZ1UQ== 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. On CONFIG_NUMA=n, NODES_MASK is 0 and the old memdesc_nid() body folded to a constant, so page->flags/folio->flags was never actually read. ASSERT_EXCLUSIVE_BITS() is a real runtime check that can't be folded away, so doing it unconditionally would add a pointless read of page->flags/folio->flags and a check that can never fire. Keep page_to_nid()/folio_nid() as plain "return 0" static inline stubs under CONFIG_NUMA=n instead. Signed-off-by: Hui Zhu --- Changelog: v4: According to the comments of Andrew and Sashiko, set page_to_nid()/folio_nid() as static inline stubs returning 0 under CONFIG_NUMA=n. 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 | 9 +++++++++ include/linux/mmzone.h | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 485df9c2dbdd..56b39194605a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2294,15 +2294,24 @@ static inline int memdesc_nid(memdesc_flags_t mdf) } #endif +#ifdef CONFIG_NUMA 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); } +#else +#define page_to_nid(page) (0) +#define folio_nid(folio) (0) +#endif #ifdef CONFIG_NUMA_BALANCING /* page access time bits needs to hold at least 4 seconds */ 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