From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 23CEB9478 for ; Mon, 15 Sep 2025 19:47:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757965657; cv=none; b=g0vA7uhAmwVDj5di7qtFgllrNmlFgqWgma/imWo5VJx10FVfe7fAF2CbVxulNZwH9m6iNoUxRFuFb+50+uLmBJDX57Q32AhJgTr1K+3khViDn8b0Zr/E8FmNAG2NOhIW77gCiEU4vWzgcA+ZU4mVv4SsxMVr6HM6sro6jUo267g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757965657; c=relaxed/simple; bh=beGQznMU+SaBBZJJi8HgYraxym/MT8mo1MUlGReYVMo=; h=Date:To:From:Subject:Message-Id; b=P1f6AtqD2ksvY4D3P7Ncxg8QsN07A6zomvrAddcslyOBEMjilw2yKoKihNOH4pZZ2fODdnOGKcFVg/zrwKX5wK2RhB7tILmC6WzXbY1Z9Wi/NsPfwfaJ2pymziWfU1ppd7eJnbJ4+wbbKies6aIeGufUETSj5GhUjf1cK9XWy2g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=0hz/oDVe; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="0hz/oDVe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 814B0C4CEF1; Mon, 15 Sep 2025 19:47:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757965656; bh=beGQznMU+SaBBZJJi8HgYraxym/MT8mo1MUlGReYVMo=; h=Date:To:From:Subject:From; b=0hz/oDVeqXt3yHUT25uEXnU3qhfpPD59pPzBRhJC6pRRcqSOfI9E4xeer4keknqdJ ACxIPElWDzrOTrCga4AeypiA08MwyeKmOzHVLrNSfmi9F6uNoTo0Ys/A1TerHZNbus csZ3R6YvWZQkXvtjbeM2v4ejd+GaZHEL+p/7Dkak= Date: Mon, 15 Sep 2025 12:47:35 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,ryan.roberts@arm.com,npache@redhat.com,lorenzo.stoakes@oracle.com,liam.howlett@oracle.com,dev.jain@arm.com,david@redhat.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,kas@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-khugepaged-do-not-fail-collapse_pte_mapped_thp-on-scan_pmd_null.patch added to mm-new branch Message-Id: <20250915194736.814B0C4CEF1@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/khugepaged: do not fail collapse_pte_mapped_thp() on SCAN_PMD_NULL has been added to the -mm mm-new branch. Its filename is mm-khugepaged-do-not-fail-collapse_pte_mapped_thp-on-scan_pmd_null.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-do-not-fail-collapse_pte_mapped_thp-on-scan_pmd_null.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Kiryl Shutsemau Subject: mm/khugepaged: do not fail collapse_pte_mapped_thp() on SCAN_PMD_NULL Date: Fri, 12 Sep 2025 17:58:11 +0100 MADV_COLLAPSE on a file mapping behaves inconsistently depending on if PMD page table is installed or not. Consider following example: p = mmap(NULL, 2UL << 20, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); err = madvise(p, 2UL << 20, MADV_COLLAPSE); fd is a populated tmpfs file. The result depends on the address that the kernel returns on mmap(). If it is located in an existing PMD table, the madvise() will succeed. However, if the table does not exist, it will fail with -EINVAL. This occurs because find_pmd_or_thp_or_none() returns SCAN_PMD_NULL when a page table is missing, which causes collapse_pte_mapped_thp() to fail. SCAN_PMD_NULL and SCAN_PMD_NONE should be treated the same in collapse_pte_mapped_thp(): install the PMD leaf entry and allocate page tables as needed. Link: https://lkml.kernel.org/r/xhan2av3fyl7qpsl4bhjtds2zeegrl57ehtc5grtkua3c3v3nz@vain5s6gpycl Fixes: 7d8faaf15545 ("mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse") Signed-off-by: Kiryl Shutsemau Acked-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Cc: Baolin Wang Cc: Barry Song Cc: Dev Jain Cc: Liam Howlett Cc: Mariano Pache Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/khugepaged.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) --- a/mm/khugepaged.c~mm-khugepaged-do-not-fail-collapse_pte_mapped_thp-on-scan_pmd_null +++ a/mm/khugepaged.c @@ -1476,6 +1476,28 @@ static int set_huge_pmd(struct vm_area_s return SCAN_SUCCEED; } +static int install_huge_pmd(struct vm_area_struct *vma, unsigned long haddr, + pmd_t *pmd, struct folio *folio) +{ + struct mm_struct *mm = vma->vm_mm; + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + + pgd = pgd_offset(mm, haddr); + p4d = p4d_alloc(mm, pgd, haddr); + if (!p4d) + return SCAN_FAIL; + pud = pud_alloc(mm, p4d, haddr); + if (!pud) + return SCAN_FAIL; + pmd = pmd_alloc(mm, pud, haddr); + if (!pmd) + return SCAN_FAIL; + + return set_huge_pmd(vma, haddr, pmd, folio, &folio->page); +} + /** * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at * address haddr. @@ -1544,6 +1566,7 @@ int collapse_pte_mapped_thp(struct mm_st switch (result) { case SCAN_SUCCEED: break; + case SCAN_PMD_NULL: case SCAN_PMD_NONE: /* * All pte entries have been removed and pmd cleared. @@ -1688,7 +1711,7 @@ int collapse_pte_mapped_thp(struct mm_st maybe_install_pmd: /* step 5: install pmd entry */ result = install_pmd - ? set_huge_pmd(vma, haddr, pmd, folio, &folio->page) + ? install_huge_pmd(vma, haddr, pmd, folio) : SCAN_SUCCEED; goto drop_folio; abort: _ Patches currently in -mm which might be from kas@kernel.org are mm-khugepaged-do-not-fail-collapse_pte_mapped_thp-on-scan_pmd_null.patch