From nobody Mon Dec 8 04:13:43 2025 Received: from mail-wm1-f53.google.com (mail-wm1-f53.google.com [209.85.128.53]) (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 67B861C6B4 for ; Mon, 6 Oct 2025 14:46:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.53 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759761978; cv=none; b=s65rGO7+ZvkbWxw9nAKsQ+LW5XkHyFXZTKNBQp1er6IzRNCjZ24nKDNn774XvEdFHRw4A12VxqNbQBFEw0XpuAnk2enzfwqwK/JVYk/6QCsfScLurbTBhvDKLW2Mev39xOrFV27t1DO4RxiwdtF+RzWU6BgHWdsdslLzo5vMIws= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759761978; c=relaxed/simple; bh=J1a8h9/BCLeHn/rrIox4M4re1XCtlGmPzhSigCowvBw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=lGwC7BVRe5y/3rtRAh+s20enLTxTRwv57OXBDo6JqlK/vhYkl5YrJB4KMgbdF+h0h2WUv7hV56fkRYT+2PmPS21r09PpqI6VIZBX1baRYZ+IYwVYEcWHdTMSWAeGiJyGRp1YPvTgdG20wZpSrpKjM5GFdYuOjJFM+r6BmwLFvDM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.128.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wm1-f53.google.com with SMTP id 5b1f17b1804b1-46e3af7889fso31064505e9.2 for ; Mon, 06 Oct 2025 07:46:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759761974; x=1760366774; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=wuqcl+A9rzc72Ea/feTXtRnC4gt7duKqUHLzgITS2ys=; b=b5w7PDl3qSNz9VYQGzUUBKEeCZlzj6iI1eRF1ioctKnmsD0Zbsl/IB1UXKUSWcdAfV hwIdbeE3kPpb4fCuu5l2PAZxO1fZy9Xzl8y4Rknz1g6C1o4bYR1UlSnM53g28X6Kj72J mGheGCG0bZDF4xxeH3wujsnhaRvfMmuD988NSdMFXSawV3AlP1empY8Tvst54rnfRZlf uilRc2AqibG7I07Ug5cyM76scap74AIOouQli8VOfIYnMTLxIkBEnM6zz4i/E63FZmZf r1Ex8RHwvy5bi7VIyAVq0ElGbQfPnI3Si/YRR+4L0jAIICbqAqgKvOqSWV70i0wfANIa rUxA== X-Forwarded-Encrypted: i=1; AJvYcCUejI2YmV8MsWs6gOKZzpkrMkhe1cjNDUaF0bSz9n0rBPeYVcHQhzLmgD2Xc8ZYk/p5FEcGdLXRyiQUPoM=@vger.kernel.org X-Gm-Message-State: AOJu0YxcH0GjKsWfkzVnr65g3+9pJZ1wY1yoDtTIcVRlRqOyTdYNsPtS Utf6Hp3Eq42YCbT46Po7+z1TYUyDyLYJ2k+26Fb5JE1F7AMp0E74LhU6 X-Gm-Gg: ASbGnct5fs9h2L9tIh/1AUpDyYDVW3t0tA0t9mi9ZKbblzFIyx4+ce8s0bC+JHJKi9/ wcogjDXAGdTlbJWANoiRqPI16mtRHTH+J3kWpVqoXdsPaX3Hi6XarLph+yj1Chx1r/HUHaL7Y34 9YxZ+5wBud9Pj9hQNryrHHz1/jTFJV5q9Q9EJ8WcNNb0XXrhax2Ntp5c5OCun2aVeRhISCzXJcl EUrOlDQXTm4BHu26Jd6iysTEgN9epUo0s/mTek6Hq5dBUtNj1kEWY+I9zsIVWTYQPuTkmsaaY3L /12Vz2aUJxu2RbqWUbTY44yG5uNeb+mxOkT6J6YpsjJ1+ECRGxoBDd6VglHg1I9q9dcSQe8IxCx mT4ec+WZ9T/1j9CUvnHQ8U1fWUDChi4YqF4DWx5s= X-Google-Smtp-Source: AGHT+IHFHcUdMzS1csXhoGyXZeti7+KMioYMHOfR7zhdo2kycZLG0GjGV8+xFl9piJYAU+8ueDHsMg== X-Received: by 2002:a05:6000:2f83:b0:3da:e7d7:f1e0 with SMTP id ffacd0b85a97d-42567174959mr8714398f8f.27.1759761973329; Mon, 06 Oct 2025 07:46:13 -0700 (PDT) Received: from localhost.localdomain ([2a09:0:1:2::301b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4255d8ab8b0sm21242624f8f.18.2025.10.06.07.46.10 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 06 Oct 2025 07:46:13 -0700 (PDT) From: Lance Yang To: akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, ioworker0@gmail.com, richard.weiyang@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Lance Yang Subject: [PATCH mm-new v2 3/3] mm/khugepaged: merge PTE scanning logic into a new helper Date: Mon, 6 Oct 2025 22:43:38 +0800 Message-ID: <20251006144338.96519-4-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251006144338.96519-1-lance.yang@linux.dev> References: <20251006144338.96519-1-lance.yang@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Lance Yang As David suggested, the PTE scanning logic in hpage_collapse_scan_pmd() and __collapse_huge_page_isolate() was almost duplicated. This patch cleans things up by moving all the common PTE checking logic into a new shared helper, thp_collapse_check_pte(). Suggested-by: David Hildenbrand Suggested-by: Dev Jain Signed-off-by: Lance Yang --- mm/khugepaged.c | 244 ++++++++++++++++++++++++++---------------------- 1 file changed, 131 insertions(+), 113 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 87a8df90b3a6..96ea8d1b9fed 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -61,6 +61,12 @@ enum scan_result { SCAN_PAGE_FILLED, }; =20 +enum pte_check_result { + PTE_CHECK_SUCCEED, + PTE_CHECK_CONTINUE, + PTE_CHECK_FAIL, +}; + #define CREATE_TRACE_POINTS #include =20 @@ -533,62 +539,140 @@ static void release_pte_pages(pte_t *pte, pte_t *_pt= e, } } =20 +/* + * thp_collapse_check_pte - Check if a PTE is suitable for THP collapse + * @pte: The PTE to check + * @vma: The VMA the PTE belongs to + * @addr: The virtual address corresponding to this PTE + * @cc: Collapse control settings + * @foliop: On success, used to return a pointer to the folio + * Must be non-NULL + * @none_or_zero: Counter for none/zero PTEs. Must be non-NULL + * @unmapped: Counter for swap PTEs. Can be NULL if not scanning swaps + * @shared: Counter for shared pages. Must be non-NULL + * @scan_result: Used to return the failure reason (SCAN_*) on a + * PTE_CHECK_FAIL return. Must be non-NULL + * + * Returns: + * PTE_CHECK_SUCCEED - PTE is suitable, proceed with further checks + * PTE_CHECK_CONTINUE - Skip this PTE and continue scanning + * PTE_CHECK_FAIL - Abort collapse scan + */ +static inline int thp_collapse_check_pte(pte_t pte, struct vm_area_struct = *vma, + unsigned long addr, struct collapse_control *cc, + struct folio **foliop, int *none_or_zero, int *unmapped, + int *shared, int *scan_result) +{ + struct folio *folio =3D NULL; + struct page *page =3D NULL; + + if (pte_none(pte) || is_zero_pfn(pte_pfn(pte))) { + (*none_or_zero)++; + if (!userfaultfd_armed(vma) && + (!cc->is_khugepaged || + *none_or_zero <=3D khugepaged_max_ptes_none)) { + return PTE_CHECK_CONTINUE; + } else { + *scan_result =3D SCAN_EXCEED_NONE_PTE; + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); + return PTE_CHECK_FAIL; + } + } else if (!pte_present(pte)) { + if (!unmapped) { + *scan_result =3D SCAN_PTE_NON_PRESENT; + return PTE_CHECK_FAIL; + } + + if (non_swap_entry(pte_to_swp_entry(pte))) { + *scan_result =3D SCAN_PTE_NON_PRESENT; + return PTE_CHECK_FAIL; + } + + (*unmapped)++; + if (!cc->is_khugepaged || + *unmapped <=3D khugepaged_max_ptes_swap) { + /* + * Always be strict with uffd-wp enabled swap + * entries. Please see comment below for + * pte_uffd_wp(). + */ + if (pte_swp_uffd_wp(pte)) { + *scan_result =3D SCAN_PTE_UFFD_WP; + return PTE_CHECK_FAIL; + } + return PTE_CHECK_CONTINUE; + } else { + *scan_result =3D SCAN_EXCEED_SWAP_PTE; + count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); + return PTE_CHECK_FAIL; + } + } else if (pte_uffd_wp(pte)) { + /* + * Don't collapse the page if any of the small PTEs are + * armed with uffd write protection. Here we can also mark + * the new huge pmd as write protected if any of the small + * ones is marked but that could bring unknown userfault + * messages that falls outside of the registered range. + * So, just be simple. + */ + *scan_result =3D SCAN_PTE_UFFD_WP; + return PTE_CHECK_FAIL; + } + + page =3D vm_normal_page(vma, addr, pte); + if (unlikely(!page) || unlikely(is_zone_device_page(page))) { + *scan_result =3D SCAN_PAGE_NULL; + return PTE_CHECK_FAIL; + } + + folio =3D page_folio(page); + if (!folio_test_anon(folio)) { + VM_WARN_ON_FOLIO(true, folio); + *scan_result =3D SCAN_PAGE_ANON; + return PTE_CHECK_FAIL; + } + + /* + * We treat a single page as shared if any part of the THP + * is shared. + */ + if (folio_maybe_mapped_shared(folio)) { + (*shared)++; + if (cc->is_khugepaged && *shared > khugepaged_max_ptes_shared) { + *scan_result =3D SCAN_EXCEED_SHARED_PTE; + count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); + return PTE_CHECK_FAIL; + } + } + + *foliop =3D folio; + + return PTE_CHECK_SUCCEED; +} + static int __collapse_huge_page_isolate(struct vm_area_struct *vma, unsigned long start_addr, pte_t *pte, struct collapse_control *cc, struct list_head *compound_pagelist) { - struct page *page =3D NULL; struct folio *folio =3D NULL; unsigned long addr =3D start_addr; pte_t *_pte; int none_or_zero =3D 0, shared =3D 0, result =3D SCAN_FAIL, referenced = =3D 0; + int pte_check_res; =20 for (_pte =3D pte; _pte < pte + HPAGE_PMD_NR; _pte++, addr +=3D PAGE_SIZE) { pte_t pteval =3D ptep_get(_pte); - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { - ++none_or_zero; - if (!userfaultfd_armed(vma) && - (!cc->is_khugepaged || - none_or_zero <=3D khugepaged_max_ptes_none)) { - continue; - } else { - result =3D SCAN_EXCEED_NONE_PTE; - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); - goto out; - } - } else if (!pte_present(pteval)) { - result =3D SCAN_PTE_NON_PRESENT; - goto out; - } else if (pte_uffd_wp(pteval)) { - result =3D SCAN_PTE_UFFD_WP; - goto out; - } - page =3D vm_normal_page(vma, addr, pteval); - if (unlikely(!page) || unlikely(is_zone_device_page(page))) { - result =3D SCAN_PAGE_NULL; - goto out; - } =20 - folio =3D page_folio(page); - if (!folio_test_anon(folio)) { - VM_WARN_ON_FOLIO(true, folio); - result =3D SCAN_PAGE_ANON; - goto out; - } + pte_check_res =3D thp_collapse_check_pte(pteval, vma, addr, cc, + &folio, &none_or_zero, NULL, &shared, &result); =20 - /* See hpage_collapse_scan_pmd(). */ - if (folio_maybe_mapped_shared(folio)) { - ++shared; - if (cc->is_khugepaged && - shared > khugepaged_max_ptes_shared) { - result =3D SCAN_EXCEED_SHARED_PTE; - count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); - goto out; - } - } + if (pte_check_res =3D=3D PTE_CHECK_CONTINUE) + continue; + else if (pte_check_res =3D=3D PTE_CHECK_FAIL) + goto out; =20 if (folio_test_large(folio)) { struct folio *f; @@ -1259,11 +1343,11 @@ static int hpage_collapse_scan_pmd(struct mm_struct= *mm, pte_t *pte, *_pte; int result =3D SCAN_FAIL, referenced =3D 0; int none_or_zero =3D 0, shared =3D 0; - struct page *page =3D NULL; struct folio *folio =3D NULL; unsigned long addr; spinlock_t *ptl; int node =3D NUMA_NO_NODE, unmapped =3D 0; + int pte_check_res; =20 VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK); =20 @@ -1282,81 +1366,15 @@ static int hpage_collapse_scan_pmd(struct mm_struct= *mm, for (addr =3D start_addr, _pte =3D pte; _pte < pte + HPAGE_PMD_NR; _pte++, addr +=3D PAGE_SIZE) { pte_t pteval =3D ptep_get(_pte); - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { - ++none_or_zero; - if (!userfaultfd_armed(vma) && - (!cc->is_khugepaged || - none_or_zero <=3D khugepaged_max_ptes_none)) { - continue; - } else { - result =3D SCAN_EXCEED_NONE_PTE; - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); - goto out_unmap; - } - } else if (!pte_present(pteval)) { - if (non_swap_entry(pte_to_swp_entry(pteval))) { - result =3D SCAN_PTE_NON_PRESENT; - goto out_unmap; - } - - ++unmapped; - if (!cc->is_khugepaged || - unmapped <=3D khugepaged_max_ptes_swap) { - /* - * Always be strict with uffd-wp - * enabled swap entries. Please see - * comment below for pte_uffd_wp(). - */ - if (pte_swp_uffd_wp(pteval)) { - result =3D SCAN_PTE_UFFD_WP; - goto out_unmap; - } - continue; - } else { - result =3D SCAN_EXCEED_SWAP_PTE; - count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); - goto out_unmap; - } - } else if (pte_uffd_wp(pteval)) { - /* - * Don't collapse the page if any of the small - * PTEs are armed with uffd write protection. - * Here we can also mark the new huge pmd as - * write protected if any of the small ones is - * marked but that could bring unknown - * userfault messages that falls outside of - * the registered range. So, just be simple. - */ - result =3D SCAN_PTE_UFFD_WP; - goto out_unmap; - } =20 - page =3D vm_normal_page(vma, addr, pteval); - if (unlikely(!page) || unlikely(is_zone_device_page(page))) { - result =3D SCAN_PAGE_NULL; - goto out_unmap; - } - folio =3D page_folio(page); + pte_check_res =3D thp_collapse_check_pte(pteval, vma, addr, cc, + &folio, &none_or_zero, &unmapped, + &shared, &result); =20 - if (!folio_test_anon(folio)) { - VM_WARN_ON_FOLIO(true, folio); - result =3D SCAN_PAGE_ANON; + if (pte_check_res =3D=3D PTE_CHECK_CONTINUE) + continue; + else if (pte_check_res =3D=3D PTE_CHECK_FAIL) goto out_unmap; - } - - /* - * We treat a single page as shared if any part of the THP - * is shared. - */ - if (folio_maybe_mapped_shared(folio)) { - ++shared; - if (cc->is_khugepaged && - shared > khugepaged_max_ptes_shared) { - result =3D SCAN_EXCEED_SHARED_PTE; - count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); - goto out_unmap; - } - } =20 /* * Record which node the original page is from and save this --=20 2.49.0