From nobody Sat Feb 7 23:12:39 2026 Received: from mail-wr1-f42.google.com (mail-wr1-f42.google.com [209.85.221.42]) (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 6AA5F2BEC3A for ; Wed, 8 Oct 2025 04:40:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.42 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759898425; cv=none; b=BpzQIMIppeVTYw8LSdtPUGb8Sd4hpszZkLzDbjiyTOJgk3/GVvI5jVwwFpe04AUdRmUt7HbnBszQTHGpozIxtlSemv4EFQ7bP+YLLtF3SU0ucaKrICT3p1RT+Lm0jkBpFsC+ZkBl7ploO+A+jSWo1CaATA1wfn/kU06fpP8sIEw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759898425; c=relaxed/simple; bh=qSNZNuXhi64kHU7q22LPeQqfDx8xX+FcK9o+ua0+r/E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uqNpjmIHp7SSb5Gu+C4uv3Pm1qQhtRb4HaCSul+7Jfk8Lvg1Saj1tr15n8HYILsaMi6qE02HnIlf2cHHk9FRjo1coqSVgptgiS+RvDqzdKPOggPOL1oTqwAZrGLPmboGsnw61cuUDLsf7ZFRMvAKXUqi7/3XQarfq6UZJiTmaG4= 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=209.85.221.42 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-wr1-f42.google.com with SMTP id ffacd0b85a97d-42420c7de22so3744187f8f.1 for ; Tue, 07 Oct 2025 21:40:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759898421; x=1760503221; 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=w4CdxE8CMoT0aWE1+y5A5fa72do+/1xnsq0UYyqE6iA=; b=R0ZWqBajM/aePmWNwb+6EgEI345TP6qp4FtI4KXh2H38TLYj13r3/UxV0H95qaYoAl IqplC86zMdAh2eiOsTdHHNAhzI/rmc4cjUcO3H7NSuKQUW9yzxlC/3jiIh+2RrJ7M1H1 BAf+LOMKXtW0zflHOtf5X8F6V79uS2UTej/QyU7yJiCGPM1ankm6VW+ycDeAC5vUgrHs nPaX4LWzFp6Hv+W/9eE6N1PPqP12P7XZr04TU1WyycfmWkDkqDnxQmbNoQwgDd4d3sR+ DnDPu52ic+veInMZ0OsawKJzWLX+3jEHSLN3MaQyhVFaYIznKHMJwiatcfIhZts1/WZq 34Hw== X-Forwarded-Encrypted: i=1; AJvYcCXEMMSiOFSLxDo7b55R+izm/hyyY0zFoZ4Tgrq/swDrBUsW6aTKjMMYqbiN7zMy+fXitmRfmFUhj6c66U4=@vger.kernel.org X-Gm-Message-State: AOJu0Yxv4Tg5USadS0YkeKMPyvqD+5AFH2LGSgET3nhPTgiMITZ38id/ /I4mGLAh4RtB8sYcVNXJ0F1q60aLp6uYzH+i6S/khr05DB8nW3Z2G6QY X-Gm-Gg: ASbGncv/7UlvA0Mdo64Mms7YYlGSuHOAChFDLCSK6+ZeCvunIr7exqjAsluFeT4G5Lc bY8g36in5RpXhwjYrFShxFv1WyG4sV3x2esQbFYG2zVSBjQ/Rf6AvErgP7j1zzCqz+Vy79vl5Wd B+2jzFQ6lw+4TGmjWj0VZKPz69eYBGypNJg3Jahj/7z1JuiyD1WxH86wAl5seSmFGWSD5k+CGad Bj4se/kwnuY8PI6oWaTNG5dSLWDw1Bs53eGRUxCHGfF1VRClxft3efpWVJvXBXYKHowr5UF4Fg+ 8FjeI8wPNOft5XWxIs93Gj0mxGYdXE3MV17bN+YAs7dM2BSGNeqX9aj2U2mDSsuiny2cnqaW/Ef B7wn0XNrG0bEFgK+TK4u6F3pl6QVU8BCs6UlxVck= X-Google-Smtp-Source: AGHT+IHch9/ftJLZar+bagytdzxWRTkDWRmOOzIGqnFNZ4Rsbi6RYB3Zvqgd5s1fv1Io5v5ehi2r0A== X-Received: by 2002:a05:6000:26c2:b0:3e7:5f26:f1e5 with SMTP id ffacd0b85a97d-4266e7beb57mr772457f8f.23.1759898421384; Tue, 07 Oct 2025 21:40:21 -0700 (PDT) Received: from localhost.localdomain ([2a09:0:1:2::30b2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4255d8a6c49sm28159164f8f.3.2025.10.07.21.40.13 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 07 Oct 2025 21:40:21 -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 v3 3/3] mm/khugepaged: merge PTE scanning logic into a new helper Date: Wed, 8 Oct 2025 12:37:48 +0800 Message-ID: <20251008043748.45554-4-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251008043748.45554-1-lance.yang@linux.dev> References: <20251008043748.45554-1-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(). While at it, we use vm_normal_folio() instead of vm_normal_page(). Suggested-by: David Hildenbrand Suggested-by: Dev Jain Signed-off-by: Lance Yang --- mm/khugepaged.c | 243 ++++++++++++++++++++++++++---------------------- 1 file changed, 130 insertions(+), 113 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index b5c0295c3414..7116caae1fa4 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 +539,139 @@ 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 + * @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 + * @cc: Collapse control settings + * + * 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 folio **foliop, int *none_or_zero, + int *unmapped, int *shared, int *scan_result, + struct collapse_control *cc) +{ + struct folio *folio =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; + } + + folio =3D vm_normal_folio(vma, addr, pte); + if (unlikely(!folio) || unlikely(folio_is_zone_device(folio))) { + *scan_result =3D SCAN_PAGE_NULL; + return PTE_CHECK_FAIL; + } + + 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, + &folio, &none_or_zero, NULL, &shared, + &result, cc); =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; @@ -1264,11 +1347,11 @@ 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 @@ -1287,81 +1370,15 @@ 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; - } =20 - ++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; - } + pte_check_res =3D thp_collapse_check_pte(pteval, vma, addr, + &folio, &none_or_zero, &unmapped, + &shared, &result, cc); =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); - - 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