From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D140A2FB0B5 for ; Wed, 15 Oct 2025 01:48:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760492898; cv=none; b=U6jSP7jiwdn48WczgnJfL5kEIUExBWle1h8IaRN9Sq2VfXVNFiWgkirGFcfcz/5zOEXW9PhlHiU1/sjwQVD0mP6JeFAmgujsun5SWkvD/o8dkWrgGnS9e/BP1j3H3roHDepLFYHU9eY8dccghzG43nxBZHSI8a2fQQqf6DceJpo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760492898; c=relaxed/simple; bh=RjHUPwMWfdNexAovzhoKmoO8IIDB1TyCbeQ0c57MvUw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XcwpIBMhmJ5qlYdWr+kEf3kZKqWi24g4J+ogJRJZWa0piMCkBKt2mPbJVeQzhTZmkukbbv7hrcKlaWWgA5nfdmkZUIRE7+VvkKljOMNeDYdTGY8ip37LlaYONzzQ8koc/hqPx0hYigkNye+/88xEJuLD8JhSqWXOH07wHwmcuic= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ZggVZyWe; arc=none smtp.client-ip=91.218.175.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ZggVZyWe" Message-ID: <8e7c7078-7757-44d2-b44a-aa8cf17cabd0@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1760492893; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=u1M0LsUtUJWc3UcAMyUSgMgp//nDL5rn5P9GaTVaKto=; b=ZggVZyWexZbda70QG4IIWn47nc9R+H8nnh3pl/dtUdOmnMXcJlJa5d1sGUVxCWo4SFTwOC cNsAR4HQxB+pacY/fzRVxL97cFJKKRdRv86A+lFgbPGnjY3ERwnGa2tYv1ba9+/CAyr1ga yBTRltVwJqaq0dFG9v+YrdP4qIOVsfw= Date: Wed, 15 Oct 2025 09:48:05 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH mm-new v3 3/3] mm/khugepaged: merge PTE scanning logic into a new helper Content-Language: en-US To: Lorenzo Stoakes Cc: akpm@linux-foundation.org, david@redhat.com, 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 References: <20251008043748.45554-1-lance.yang@linux.dev> <20251008043748.45554-4-lance.yang@linux.dev> <04734f2d-ea1f-487c-b01c-c3d6e1b4a778@lucifer.local> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <04734f2d-ea1f-487c-b01c-c3d6e1b4a778@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2025/10/15 01:41, Lorenzo Stoakes wrote: > OK so this patch _is_ based on [0] already being applied then? > > I don't see any is_swap_pte() here so presumably so right? > > Can we just respin these series and put them together? Because now I've > reviewed a bunch of stuff in [0], which this series depends upon, and > you're saying we should now review on this instead of that and it's a bit > of a mess. > > Once review here is dealt with can you combine [0] into this series please? Got it, thanks! > > For [0] I would like you to reinstate the is_swap_pte() conditional as > (copiously :) discussed over there. > > [0}: https://lore.kernel.org/all/20251008032657.72406-1-lance.yang@linux.dev/ > > Thanks, Lorenzo > > On Wed, Oct 08, 2025 at 12:37:48PM +0800, Lance Yang wrote: >> 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, >> }; >> >> +enum pte_check_result { >> + PTE_CHECK_SUCCEED, >> + PTE_CHECK_CONTINUE, >> + PTE_CHECK_FAIL, >> +}; >> + >> #define CREATE_TRACE_POINTS >> #include >> >> @@ -533,62 +539,139 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte, >> } >> } >> >> +/* >> + * 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 = NULL; >> + >> + if (pte_none(pte) || is_zero_pfn(pte_pfn(pte))) { >> + (*none_or_zero)++; >> + if (!userfaultfd_armed(vma) && >> + (!cc->is_khugepaged || >> + *none_or_zero <= khugepaged_max_ptes_none)) { >> + return PTE_CHECK_CONTINUE; >> + } else { >> + *scan_result = 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 = SCAN_PTE_NON_PRESENT; >> + return PTE_CHECK_FAIL; >> + } >> + >> + if (non_swap_entry(pte_to_swp_entry(pte))) { >> + *scan_result = SCAN_PTE_NON_PRESENT; >> + return PTE_CHECK_FAIL; >> + } >> + >> + (*unmapped)++; >> + if (!cc->is_khugepaged || >> + *unmapped <= 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 = SCAN_PTE_UFFD_WP; >> + return PTE_CHECK_FAIL; >> + } >> + return PTE_CHECK_CONTINUE; >> + } else { >> + *scan_result = 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 = SCAN_PTE_UFFD_WP; >> + return PTE_CHECK_FAIL; >> + } >> + >> + folio = vm_normal_folio(vma, addr, pte); >> + if (unlikely(!folio) || unlikely(folio_is_zone_device(folio))) { >> + *scan_result = SCAN_PAGE_NULL; >> + return PTE_CHECK_FAIL; >> + } >> + >> + if (!folio_test_anon(folio)) { >> + VM_WARN_ON_FOLIO(true, folio); >> + *scan_result = 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 = SCAN_EXCEED_SHARED_PTE; >> + count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); >> + return PTE_CHECK_FAIL; >> + } >> + } >> + >> + *foliop = 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 = NULL; >> struct folio *folio = NULL; >> unsigned long addr = start_addr; >> pte_t *_pte; >> int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; >> + int pte_check_res; >> >> for (_pte = pte; _pte < pte + HPAGE_PMD_NR; >> _pte++, addr += PAGE_SIZE) { >> pte_t pteval = 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 <= khugepaged_max_ptes_none)) { >> - continue; >> - } else { >> - result = SCAN_EXCEED_NONE_PTE; >> - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); >> - goto out; >> - } >> - } else if (!pte_present(pteval)) { >> - result = SCAN_PTE_NON_PRESENT; >> - goto out; >> - } else if (pte_uffd_wp(pteval)) { >> - result = SCAN_PTE_UFFD_WP; >> - goto out; >> - } >> - page = vm_normal_page(vma, addr, pteval); >> - if (unlikely(!page) || unlikely(is_zone_device_page(page))) { >> - result = SCAN_PAGE_NULL; >> - goto out; >> - } >> >> - folio = page_folio(page); >> - if (!folio_test_anon(folio)) { >> - VM_WARN_ON_FOLIO(true, folio); >> - result = SCAN_PAGE_ANON; >> - goto out; >> - } >> + pte_check_res = thp_collapse_check_pte(pteval, vma, addr, >> + &folio, &none_or_zero, NULL, &shared, >> + &result, cc); >> >> - /* See hpage_collapse_scan_pmd(). */ >> - if (folio_maybe_mapped_shared(folio)) { >> - ++shared; >> - if (cc->is_khugepaged && >> - shared > khugepaged_max_ptes_shared) { >> - result = SCAN_EXCEED_SHARED_PTE; >> - count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); >> - goto out; >> - } >> - } >> + if (pte_check_res == PTE_CHECK_CONTINUE) >> + continue; >> + else if (pte_check_res == PTE_CHECK_FAIL) >> + goto out; >> >> 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 = SCAN_FAIL, referenced = 0; >> int none_or_zero = 0, shared = 0; >> - struct page *page = NULL; >> struct folio *folio = NULL; >> unsigned long addr; >> spinlock_t *ptl; >> int node = NUMA_NO_NODE, unmapped = 0; >> + int pte_check_res; >> >> VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK); >> >> @@ -1287,81 +1370,15 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, >> for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR; >> _pte++, addr += PAGE_SIZE) { >> pte_t pteval = 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 <= khugepaged_max_ptes_none)) { >> - continue; >> - } else { >> - result = 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 = SCAN_PTE_NON_PRESENT; >> - goto out_unmap; >> - } >> >> - ++unmapped; >> - if (!cc->is_khugepaged || >> - unmapped <= 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 = SCAN_PTE_UFFD_WP; >> - goto out_unmap; >> - } >> - continue; >> - } else { >> - result = 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 = SCAN_PTE_UFFD_WP; >> - goto out_unmap; >> - } >> + pte_check_res = thp_collapse_check_pte(pteval, vma, addr, >> + &folio, &none_or_zero, &unmapped, >> + &shared, &result, cc); >> >> - page = vm_normal_page(vma, addr, pteval); >> - if (unlikely(!page) || unlikely(is_zone_device_page(page))) { >> - result = SCAN_PAGE_NULL; >> - goto out_unmap; >> - } >> - folio = page_folio(page); >> - >> - if (!folio_test_anon(folio)) { >> - VM_WARN_ON_FOLIO(true, folio); >> - result = SCAN_PAGE_ANON; >> + if (pte_check_res == PTE_CHECK_CONTINUE) >> + continue; >> + else if (pte_check_res == 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 = SCAN_EXCEED_SHARED_PTE; >> - count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); >> - goto out_unmap; >> - } >> - } >> >> /* >> * Record which node the original page is from and save this >> -- >> 2.49.0 >>