From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f170.google.com (mail-pf1-f170.google.com [209.85.210.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 26A41383993 for ; Fri, 28 Aug 2026 18:37:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787942227; cv=none; b=iJY/OqyYqma4SMzY3qAmN1BP/AL/4t8sKVXQHp7TzG/X3SRKNqtkKLi/TV9ElOTbI/1NtrspFvcAsqaffKA9zChEXWKMtJ2Qz6OXwuvsi5fIfm4llxszlgtwTEmo3+Y5SnHwWJwm2RFbOVQvPX1N4jBRFl34PmjgoNbitXIxpl0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787942227; c=relaxed/simple; bh=I25lWYt6cViseaUZtP8CeKwfUIj5/ciNKEk4etFYL1w=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=fH92yCBLt5yM5nFGkcQVyohlKEfRSkj3sen3px4/wwBVlbIQaaBEJOqFn2iiRDcOq6Z5jsFaUB1z7aL2tpEqMlTVt2zQMJM6KBd5wKHzc/rvsPmbMQi08jOWi73v+lGLsaio7Iv7DKeUMg62Wzw4nMMtyd/zsHe4h/29FCqKHw8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=CZ00InjO; arc=none smtp.client-ip=209.85.210.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CZ00InjO" Received: by mail-pf1-f170.google.com with SMTP id d2e1a72fcca58-84f3ab8750cso1072064b3a.0 for ; Fri, 28 Aug 2026 11:37:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1787942223; x=1788547023; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=7mVEURHMP319Byv9p6qmQOcjq3woNvQVkr+r4ShGABI=; b=CZ00InjOHXHX/H8HcWuRUtfMdLDaC6jCwr9GCNYajPWW77vuhiTUse7xrlq4zJqtLB QFxZIEeW/DbD+olttDXAw276gLg4snaZYwZlYc1owsTp93eoN6QRnn4sjK4e9QSCzcsa SGsI2S0358nrAiDAGw+j2EQhKdzZOORh86tK08y57cmX65DMBh1IJ/7OIT5USaT2wTUs uYf1OOYlOMF9Uej0Di7MQfyQFsZwQvbsx2zUluBkhEHnAOjnHI/KRro1boSz7CW5gnNv 7hH6OppQmfWglAyuHVlcruCELwFfTIUw8myLyJsnG9cf6DXdOsnmGMw7ptg3aYNVmpRH XdvA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787942223; x=1788547023; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=7mVEURHMP319Byv9p6qmQOcjq3woNvQVkr+r4ShGABI=; b=l7rkA2V0uQKrB5Y+3nO08y/hGjEX7Xd1XLiv//HVNIhGcimZQoPBIlkmcauc3+Gg5U TgjEoUw3+skSiLOmERBQ5lWqxDsjR9oed8KWwq6Ql40+yjUyyeSYSUr7Pst/EwIEzAlV RA4YVCpOws+YG8iYDSBjuRzoXW1eaFlr0UQnOpl56bvDfTHpMLEKHaiOBBvyNEeEiwY/ IHytPg7E3IWjFMYmQSG5aqgGhUwFj/27hOddhkt86i6ULV3TRokTY5lA7k7YnKrJ/0Ze sKgjENVcnrJjDKfqxdY0njbhbA7G93JC14nvmeZoPlU1PI9wy+Asf8GaTr1XyLITARQ1 3UOA== X-Forwarded-Encrypted: i=1; AHgh+Rp0lScUembjdohgk8l4nSYvTgm+f+iqNdQxsjgvIS804rTpo4vx5ejPCACedNeNcqESk5q6PzftBvfMY4w=@vger.kernel.org X-Gm-Message-State: AFuF++m68kICtTCjv+slj7LsA60qkB0LstdgRR2obE6DMkqKDZ92MWGf v5h1tVLDsndhIawHc2O3YNrIvHJvQN9xSMGPRMDbXrPs0c7nzAmOSXMc X-Gm-Gg: AR+sD11LVv2ZsuKUVWz8xohn82Cu+bua2GHDf71y8YhlLrUWus/X9K7V7NJ6+4Tp7yB IdI4urZ++4XQpLm7VntqjjWI0rmt/OwYj76OuA++sNtRzw0Xt+XkpA9TxHf2HRwyLDeF6ZitNpk RQaGzHdnb65nGLF/CpnmaFJHOYhonigj4SLQPTI/Z0ONcT5wK+ytBzFUbnqVxzC+gWFIwGewpkB KLfBDt6Et1CfjCzEwxKia2GNqqDDtvqO2dKZ2dQ97ozXz1p3XcTpfkB3YtIX3Vv1PJb5vJOmJ9E 4y+xeZd9ZQ1kiPyh7RArjfm8iBSJoA3rHiPvz32LMfEvFsrEE9Xcrz7k0K6hY24NduFLpakX3Nx AFP1W/qSgxk4iExgFuJ/V/eLf0vR0h6RRxME5sRoXfmfh+vnU7fxn9ycxeekQlSidIjfJhiCJim k8iaPl/Os/liEuEk7YE8CUIyCjAKAgZ3RUwJLzTlSDygv9tDENXoZ0PXIxxtYuWjX2hyzWFnGIj 4Hw5r/AY1D6DjClL2HRGJEoZ7KR X-Received: by 2002:a05:6a00:2309:b0:857:7384:b5fc with SMTP id d2e1a72fcca58-8577384c2c3mr2082303b3a.24.1787942223100; Fri, 28 Aug 2026 11:37:03 -0700 (PDT) Received: from aig-kmd-01.. ([120.133.49.20]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-856a2ea6fa3sm844230b3a.37.2026.08.28.11.36.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Aug 2026 11:37:02 -0700 (PDT) From: Yin Tirui To: Andrew Morton , linux-mm@kvack.org Cc: David Hildenbrand , Lorenzo Stoakes , Dev Jain , Zi Yan , Baolin Wang , Barry Song , Lance Yang , Ryan Roberts , Nico Pache , Usama Arif , "Liam R . Howlett" , wangkefeng.wang@huawei.com, chenjun102@huawei.com, linux-kernel@vger.kernel.org, Yin Tirui Subject: [PATCH RFC 1/9] mm/huge_memory: read the huge PMD entry once when splitting it Date: Sat, 29 Aug 2026 02:33:11 +0800 Message-Id: <1b11fdaa4f5819959505ad72e3d70bad5fc1d343.1787941780.git.yintirui@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit __split_huge_pmd_locked() re-reads *pmd several times to classify the same entry. The PMD page table lock is held throughout, so read it once into old_pmd and classify from that. No functional change intended. Signed-off-by: Yin Tirui --- mm/huge_memory.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index afbb5974bd22..8feabdcf6307 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3143,10 +3143,11 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, unsigned long haddr, bool freeze) { struct mm_struct *mm = vma->vm_mm; + pmd_t old_pmd = *pmd; struct folio *folio; struct page *page; pgtable_t pgtable; - pmd_t old_pmd, _pmd; + pmd_t _pmd; bool soft_dirty, uffd_wp = false, young = false, write = false; bool anon_exclusive = false, dirty = false; unsigned long addr; @@ -3157,7 +3158,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, VM_BUG_ON_VMA(vma->vm_start > haddr, vma); VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); - VM_WARN_ON_ONCE(!pmd_is_valid_softleaf(*pmd) && !pmd_trans_huge(*pmd)); + VM_WARN_ON_ONCE(!pmd_is_valid_softleaf(old_pmd) && + !pmd_trans_huge(old_pmd)); count_vm_event(THP_SPLIT_PMD); @@ -3193,7 +3195,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, return; } - if (is_huge_zero_pmd(*pmd)) { + if (is_huge_zero_pmd(old_pmd)) { /* * FIXME: Do we want to invalidate secondary mmu by calling * mmu_notifier_arch_invalidate_secondary_tlbs() see comments below @@ -3206,10 +3208,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, return __split_huge_zero_page_pmd(vma, haddr, pmd); } - if (pmd_is_migration_entry(*pmd)) { + if (pmd_is_migration_entry(old_pmd)) { softleaf_t entry; - old_pmd = *pmd; entry = softleaf_from_pmd(old_pmd); page = softleaf_to_page(entry); folio = page_folio(page); @@ -3222,10 +3223,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, anon_exclusive = softleaf_is_migration_read_exclusive(entry); young = softleaf_is_migration_young(entry); dirty = softleaf_is_migration_dirty(entry); - } else if (pmd_is_device_private_entry(*pmd)) { + } else if (pmd_is_device_private_entry(old_pmd)) { softleaf_t entry; - old_pmd = *pmd; entry = softleaf_from_pmd(old_pmd); page = softleaf_to_page(entry); folio = page_folio(page); @@ -3417,7 +3417,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, } pte_unmap(pte); - if (!pmd_is_migration_entry(*pmd)) + if (!pmd_is_migration_entry(old_pmd)) folio_remove_rmap_pmd(folio, page, vma); if (freeze) put_page(page); -- 2.34.1