From nobody Thu Nov 5 05:11:27 2026 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=115.124.30.113 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793847410; b=T4faOrDL7WXPiV9T2qf98870zk96RTqgDCT1dTnEwpNGklMVgrujjq+4luMUUVhlAPnT 94cZTSji0cg2ofPJPAemKi29art7KwHXMQjG/Bn6DwtQmrNxZXeYVWI104X3vo1SSPeh5 0eOaaNnG2ua3DPCvFNGmSaWiCRQq3qb3AJ8MxiiC9fg3PIhPvJ5lPsw4Rm6nElmHTt2XP v6rNGziZDzu5nLEZI0SXGVAGOmk17nlXRVOHVYbNwj5BuUJ4krdszlKEXXV12M27rAb6k R11lo08LKll/qALlq8+TGddtgu/oL1ovDmbe4yZ/jLiKERsSD40Dty2vxfYCH5OSEiw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793847410; h=DMARC-Filter:DKIM-Signature:X-Alimail-AntiSpam:Received:From:To:Cc: Subject:Date:Message-ID:X-Mailer:MIME-Version: Content-Transfer-Encoding; bh=e7HItsBXSCgxUc39U3iHUfM+8l/Wb7Jodni6FIfl/KA=; b=eG3yDyV3LEktgJIYuPN1Zrfz+C59XRXzXYQJpGGaKUw5No/Nw0V92vth3ovNsdQhHg+5 fVikTHFlLHMjEGLm6CeORJL2JXPbdxbDUu2lLj0CEUZ05ArFI5q617f8xtMUdFWZRpxe8 MQZMSbaQ5IECWysVxf2AWJV+A1IXTTSNTYnIEdn9wsw18ahWXpPTbvJHiPdxpfsp5CAgP i2/JWeOWgUH5BdjvUAUlK7z+gxc4LgV6AiCnAUsTIPFDdIFyHBG2yXR+I7FG2YOLYbJxL 9Owspgb1UfBXFdIydaQpgyzoFfJ7QiFi3hT8n1rEM3yG5X9qep/tFsUu28xvZuPBtQA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=sJhi3beE; arc=none smtp.remote-ip=115.124.30.113 Received: from out30-113.freemail.mail.aliyun.com (out30-113.freemail.mail.aliyun.com [115.124.30.113]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39AA6606A31B for ; Thu, 5 Nov 2026 02:56:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 39AA6606A31B Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=sJhi3beE DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1793847399; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=e7HItsBXSCgxUc39U3iHUfM+8l/Wb7Jodni6FIfl/KA=; b=sJhi3beEBbsEJE9qy/YnTi+EiZCxX2WyfElrwLg3DzOlo6HeMMD+4xHjp/9asCxLslZKpJjLzOYWqgDBRMgPucqE5hrjxSaqp2FmPEJF5IFz8xpAPr/P26XflXQ+NWCmqCCT0HiFytm2GRM8aEWMmqa0HJQ9By1AuYRN2rkcUNY= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037033178;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=15;SR=0;TI=SMTPD_---0XE7G6W0_1793847397; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XE7G6W0_1793847397 cluster:ay36) by smtp.aliyun-inc.com; Thu, 05 Nov 2026 10:56:38 +0800 From: Baolin Wang To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org Cc: riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, qi.zheng@linux.dev, pfalcato@suse.de, ayushr@modal.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm: synchronize with PTE table reclaim for all folio sizes Date: Thu, 5 Nov 2026 10:56:28 +0800 Message-ID: X-Mailer: git-send-email 2.43.5 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Similar to commit 243cf1f67b36 ("mm: memory: fix truncation removing mapped folios"), the '!pmd_present()' check in page_vma_mapped_walk() can also race with concurrent page table reclamation via zap_empty_pte_table(). page_vma_mapped_walk() is used by many functions including try_to_unmap(), try_to_migrate(), folio_mkclean(), pfn_mkclean_range(), remove_migration_pt= es(), page_mapped_in_vma(), and mapping_wrprotect_range(). Except for try_to_unma= p() and try_to_migrate(), the other callers do not perform post-walk accounting checks, so the race has no observable impact on them. For migration, the race can cause unnecessary retries. For reclaim via try_to_unmap(), the race can cause failure to reclaim a folio that is in fact already unmapped (as shown below), which may lead to unexpected OOM or increased refaults. CPU 0 (reclaim) CPU 1 (MADV_DONTNEED) Acked-by: Qi Zheng Reviewed-by: Lance Yang Suggested-by: David Hildenbrand (Arm) -------------------------------- -------------------------------- folio_lock(F) try_to_unmap(F, TTU_SYNC) zap_pte_range(full PMD range) spin_lock(ptl) clear PTEs zap_empty_pte_table() spin_trylock(pml) pmd_clear() spin_unlock(pml) page_vma_mapped_walk() observe !pmd_present(pmde) nr_pages < HPAGE_PMD_NR skip synchronization return false try_to_unmap() returns folio_mapped(F) =3D=3D true nr_unmap_fail +=3D folio_nr_pages(F) tlb_flush_mmu_tlbonly() tlb_flush_rmaps() remove F's rmaps spin_unlock(ptl) Commit 243cf1f67b36 ("mm: memory: fix truncation removing mapped folios") has already moved the PMD clear operation (via zap_empty_pte_table()) to after tlb_flush_rmaps(). Similarly, page_vma_mapped_walk() also needs to use sync_with_folio_pmd_zap() to synchronize and avoid memory ordering issues on weakly ordered CPUs. Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_D= ONTNEED)") Cc: stable@vger.kernel.org Suggested-by: David Hildenbrand (Arm) Signed-off-by: Baolin Wang --- mm/page_vma_mapped.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index e6b6170c2f4f..8797467b6f0c 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -293,10 +293,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk = *pvmw) spin_unlock(pvmw->ptl); pvmw->ptl =3D NULL; } else if (!pmd_present(pmde)) { - if ((pvmw->flags & PVMW_SYNC) && - thp_vma_suitable_order(vma, pvmw->address, - PMD_ORDER) && - (pvmw->nr_pages >=3D HPAGE_PMD_NR)) + if (pvmw->flags & PVMW_SYNC) sync_with_folio_pmd_zap(mm, pvmw->pmd); =20 goto next_pmd; --=20 2.47.3