From nobody Sun Feb 8 17:36:43 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 B30E43921DD for ; Thu, 22 Jan 2026 19:30:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769110254; cv=none; b=H9aWilTSwxxJI/7NtvTcG/Pbp4KopyFhuMF7TrtRYqhw3NJac1KJv8PbwOyMG0Hv9nGONw/xDmW3g9OZBHn9CnR8/6krfKY94oOUMeoMrG9RPiFlwqetV7IQpXPe7ojrCfVJ+OW7YZ7C6d7nk1X8fgq6Y/wgV1tLmFLMzF6ESUs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769110254; c=relaxed/simple; bh=59YpyF+2axU0IYL/DJ/AVGzLs+0M5DYDXfQU8pVL3E4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fLj6eqs3HdjMrFCffiAyCg/4PHfrrvSjjh5CKoVmkejsIClzC89Ps89qCvWr1X6Q0XfUo0hTWAf84S/NGyS4TQUPBvhTxgMmNMk1I0PTs5hbw+jLpA9kQGJHtdJVcTAktGHqQlLrlK9tw64WACKzx4erkGd20oG0+/AqHnD6g7E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=jUah1gam; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="jUah1gam" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1769110238; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=A+GEyTsIIxthANaYp7hDwgGrjrQoxw+PtebqYK78QEc=; b=jUah1gamugt2bUpdf71cNDdoutDLfZdJ1C+O8YsQSVdM7PCQxSpn9IGYoLDGOBCytBvx+P vFDOvnJVyr9cWqsz24VLdJh/HlHRTIltJQ57x7RmgwGXk5Qh6N8qrKkTHW7i48zg+I6GU+ vT4de+tgh9wXQNsoj6vtvwsSlXomjIE= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-580-5W3zx7phN0-Z3RZNZy6VYw-1; Thu, 22 Jan 2026 14:30:34 -0500 X-MC-Unique: 5W3zx7phN0-Z3RZNZy6VYw-1 X-Mimecast-MFC-AGG-ID: 5W3zx7phN0-Z3RZNZy6VYw_1769110233 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 72E5D18005BD; Thu, 22 Jan 2026 19:30:33 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.88.59]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D87431958DC3; Thu, 22 Jan 2026 19:30:23 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: npache@redhat.com, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, zokeefe@google.com, rientjes@google.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, David Hildenbrand Subject: [PATCH mm-unstable v14 03/16] introduce collapse_single_pmd to unify khugepaged and madvise_collapse Date: Thu, 22 Jan 2026 12:28:28 -0700 Message-ID: <20260122192841.128719-4-npache@redhat.com> In-Reply-To: <20260122192841.128719-1-npache@redhat.com> References: <20260122192841.128719-1-npache@redhat.com> 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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" The khugepaged daemon and madvise_collapse have two different implementations that do almost the same thing. Create collapse_single_pmd to increase code reuse and create an entry point to these two users. Refactor madvise_collapse and collapse_scan_mm_slot to use the new collapse_single_pmd function. This introduces a minor behavioral change that is most likely an undiscovered bug. The current implementation of khugepaged tests collapse_test_exit_or_disable before calling collapse_pte_mapped_thp, but we weren't doing it in the madvise_collapse case. By unifying these two callers madvise_collapse now also performs this check. We also modify the return value to be SCAN_ANY_PROCESS which properly indicates that this process is no longer valid to operate on. We also guard the khugepaged_pages_collapsed variable to ensure its only incremented for khugepaged. Reviewed-by: Wei Yang Reviewed-by: Lance Yang Reviewed-by: Lorenzo Stoakes Reviewed-by: Baolin Wang Reviewed-by: Zi Yan Acked-by: David Hildenbrand Signed-off-by: Nico Pache --- mm/khugepaged.c | 106 +++++++++++++++++++++++++++--------------------- 1 file changed, 60 insertions(+), 46 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index fefcbdca4510..59e5a5588d85 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2394,6 +2394,54 @@ static enum scan_result collapse_scan_file(struct mm= _struct *mm, unsigned long a return result; } =20 +/* + * Try to collapse a single PMD starting at a PMD aligned addr, and return + * the results. + */ +static enum scan_result collapse_single_pmd(unsigned long addr, + struct vm_area_struct *vma, bool *mmap_locked, + struct collapse_control *cc) +{ + struct mm_struct *mm =3D vma->vm_mm; + enum scan_result result; + struct file *file; + pgoff_t pgoff; + + if (vma_is_anonymous(vma)) { + result =3D collapse_scan_pmd(mm, vma, addr, mmap_locked, cc); + goto end; + } + + file =3D get_file(vma->vm_file); + pgoff =3D linear_page_index(vma, addr); + + mmap_read_unlock(mm); + *mmap_locked =3D false; + result =3D collapse_scan_file(mm, addr, file, pgoff, cc); + fput(file); + + if (result !=3D SCAN_PTE_MAPPED_HUGEPAGE) + goto end; + + mmap_read_lock(mm); + *mmap_locked =3D true; + if (collapse_test_exit_or_disable(mm)) { + mmap_read_unlock(mm); + *mmap_locked =3D false; + return SCAN_ANY_PROCESS; + } + result =3D try_collapse_pte_mapped_thp(mm, addr, !cc->is_khugepaged); + if (result =3D=3D SCAN_PMD_MAPPED) + result =3D SCAN_SUCCEED; + mmap_read_unlock(mm); + *mmap_locked =3D false; + +end: + if (cc->is_khugepaged && result =3D=3D SCAN_SUCCEED) + ++khugepaged_pages_collapsed; + return result; +} + static unsigned int collapse_scan_mm_slot(unsigned int pages, enum scan_re= sult *result, struct collapse_control *cc) __releases(&khugepaged_mm_lock) @@ -2466,34 +2514,9 @@ static unsigned int collapse_scan_mm_slot(unsigned i= nt pages, enum scan_result * VM_BUG_ON(khugepaged_scan.address < hstart || khugepaged_scan.address + HPAGE_PMD_SIZE > hend); - if (!vma_is_anonymous(vma)) { - struct file *file =3D get_file(vma->vm_file); - pgoff_t pgoff =3D linear_page_index(vma, - khugepaged_scan.address); - - mmap_read_unlock(mm); - mmap_locked =3D false; - *result =3D collapse_scan_file(mm, - khugepaged_scan.address, file, pgoff, cc); - fput(file); - if (*result =3D=3D SCAN_PTE_MAPPED_HUGEPAGE) { - mmap_read_lock(mm); - if (collapse_test_exit_or_disable(mm)) - goto breakouterloop; - *result =3D try_collapse_pte_mapped_thp(mm, - khugepaged_scan.address, false); - if (*result =3D=3D SCAN_PMD_MAPPED) - *result =3D SCAN_SUCCEED; - mmap_read_unlock(mm); - } - } else { - *result =3D collapse_scan_pmd(mm, vma, - khugepaged_scan.address, &mmap_locked, cc); - } - - if (*result =3D=3D SCAN_SUCCEED) - ++khugepaged_pages_collapsed; =20 + *result =3D collapse_single_pmd(khugepaged_scan.address, + vma, &mmap_locked, cc); /* move to next address */ khugepaged_scan.address +=3D HPAGE_PMD_SIZE; progress +=3D HPAGE_PMD_NR; @@ -2799,6 +2822,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsi= gned long start, cond_resched(); mmap_read_lock(mm); mmap_locked =3D true; + *lock_dropped =3D true; result =3D hugepage_vma_revalidate(mm, addr, false, &vma, cc); if (result !=3D SCAN_SUCCEED) { @@ -2809,17 +2833,17 @@ int madvise_collapse(struct vm_area_struct *vma, un= signed long start, hend =3D min(hend, vma->vm_end & HPAGE_PMD_MASK); } mmap_assert_locked(mm); - if (!vma_is_anonymous(vma)) { - struct file *file =3D get_file(vma->vm_file); - pgoff_t pgoff =3D linear_page_index(vma, addr); =20 - mmap_read_unlock(mm); - mmap_locked =3D false; + result =3D collapse_single_pmd(addr, vma, &mmap_locked, cc); + + if (!mmap_locked) *lock_dropped =3D true; - result =3D collapse_scan_file(mm, addr, file, pgoff, cc); =20 - if (result =3D=3D SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb && - mapping_can_writeback(file->f_mapping)) { + if (result =3D=3D SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb) { + struct file *file =3D get_file(vma->vm_file); + pgoff_t pgoff =3D linear_page_index(vma, addr); + + if (mapping_can_writeback(file->f_mapping)) { loff_t lstart =3D (loff_t)pgoff << PAGE_SHIFT; loff_t lend =3D lstart + HPAGE_PMD_SIZE - 1; =20 @@ -2829,26 +2853,16 @@ int madvise_collapse(struct vm_area_struct *vma, un= signed long start, goto retry; } fput(file); - } else { - result =3D collapse_scan_pmd(mm, vma, addr, &mmap_locked, cc); } - if (!mmap_locked) - *lock_dropped =3D true; =20 -handle_result: switch (result) { case SCAN_SUCCEED: case SCAN_PMD_MAPPED: ++thps; break; - case SCAN_PTE_MAPPED_HUGEPAGE: - BUG_ON(mmap_locked); - mmap_read_lock(mm); - result =3D try_collapse_pte_mapped_thp(mm, addr, true); - mmap_read_unlock(mm); - goto handle_result; /* Whitelisted set of results where continuing OK */ case SCAN_NO_PTE_TABLE: + case SCAN_PTE_MAPPED_HUGEPAGE: case SCAN_PTE_NON_PRESENT: case SCAN_PTE_UFFD_WP: case SCAN_LACK_REFERENCED_PAGE: --=20 2.52.0