From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 66A78349CC4 for ; Tue, 25 Aug 2026 01:55:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787622935; cv=none; b=PPnk8+HzATg0tKLEeOFBtvo8XEjBypuiaU70JWiF52A3MbJWXAHgW8yFep1uuevv3fMBhgzoTjtTa+tUWih61NVmZi5q6CaIVUdM3AZWxOSBYe0wNrgWL91u0M5VyBlFyftabv8KymjAOyvPv7JoQf/Suv5mOvdHcCVfSA2PnnA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787622935; c=relaxed/simple; bh=69oSuBQDvamvPSRda2yVXilMLG0+kHNbbYAVybxZ2zc=; h=Date:To:From:Subject:Message-Id; b=fbtXUcXn94RTqWSMQwPGgXNj44BMosO1fk4sHTtrmRmFhDdmxG/buDQiKZT+VkA8FYji88d9i+JwnQInDQMxzvF/fsL2m7Gs4yufIhj+rKTUtaZ3JKGKBqGfmC/DgezpilCn8l64JrRCwBQOjmta9DyIJJ5VHwBZf4gyC/2mQUo= 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=LQD/oyo0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="LQD/oyo0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41A221F000E9; Tue, 25 Aug 2026 01:55:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1787622934; bh=Bow7HGSSge/AHGuLEvZdPAb3atMR1ApBqzAer08lSCY=; h=Date:To:From:Subject; b=LQD/oyo0EwgXrsD2dCr/3LZS64fXaxtv2BnMJwOmQYW5m45a8VBh6roQDEsUNVpnZ hOfz2YhyGjTZ9S3l6TatSKGHaPRsMyXh4re8wKizQE0UVXtFoWd/DbOEBDw2IpVwSY wSJQJ7G1wAwCH9HhtP6kCGukoKdFAp/UNTRpx3BE= Date: Mon, 24 Aug 2026 18:55:33 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,vbabka@kernel.org,usama.arif@linux.dev,surenb@google.com,ryan.roberts@arm.com,rppt@kernel.org,pfalcato@suse.de,mhocko@suse.com,ljs@kernel.org,liam@infradead.org,lance.yang@linux.dev,dev.jain@arm.com,david@kernel.org,corbet@lwn.net,baolin.wang@linux.alibaba.com,baohua@kernel.org,nico.pache@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-khugepaged-fix-outdated-comments.patch removed from -mm tree Message-Id: <20260825015534.41A221F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/khugepaged: fix outdated comments has been removed from the -mm tree. Its filename was mm-khugepaged-fix-outdated-comments.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: "Nico Pache (Red Hat)" Subject: mm/khugepaged: fix outdated comments Date: Tue, 11 Aug 2026 06:48:36 -0600 Fix comment in collapse_scan_pmd() that still described the old folio_mapcount() > folio_ref_count() check and a "512" false-positive scenario. The code now uses folio_expected_ref_count() != folio_ref_count() which doesn't suffer from the same limitation. Fix comment in collapse_huge_page() that referenced ptep_clear_flush, when the code actually uses pmdp_collapse_flush. Fix comment in __collapse_huge_page_swapin() that referenced the old function name khugepaged_scan_pmd, now collapse_scan_pmd. Also clean up some simple typos and stale terminology (mmap_sem -> mmap_lock, PG_lock -> folio lock, page -> folio, grammar). We also clarify a comment regarding where the max_ptes_none check is deferred to in mthp_collapse() from the original collapse_scan_pmd check. Update all comments that references a function to include parentheses. [nico.pache@linux.dev: fix outdated comments] Link: https://lore.kernel.org/1c96e2f3-802f-472b-81e6-4af17a721a3c@linux.dev Link: https://lore.kernel.org/20260811-khugepaged_pte_refactor-v4-4-ddac39d61c4a@linux.dev Signed-off-by: Nico Pache (Red Hat) Acked-by: Usama Arif Assisted-by: Cursor(claude-sonnet-4):4.6 Acked-by: David Hildenbrand (Arm) Reviewed-by: Zi Yan Acked-by: Pedro Falcato Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Lance Yang Cc: Baolin Wang Cc: Barry Song Cc: Dev Jain Cc: Jonathan Corbet Cc: Liam R. Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/khugepaged.c | 44 +++++++++++++++++++++----------------------- 1 file changed, 21 insertions(+), 23 deletions(-) --- a/mm/khugepaged.c~mm-khugepaged-fix-outdated-comments +++ a/mm/khugepaged.c @@ -620,7 +620,7 @@ void __khugepaged_exit(struct mm_struct /* * This is required to serialize against * collapse_test_exit() (which is guaranteed to run - * under mmap sem read mode). Stop here (after we return all + * under mmap_lock read mode). Stop here (after we return all * pagetables will be destroyed) until khugepaged has finished * working on the pagetables under the mmap_lock. */ @@ -782,8 +782,8 @@ static enum scan_result __collapse_huge_ /* * We can do it before folio_isolate_lru because the - * folio can't be freed from under us. NOTE: PG_lock - * is needed to serialize against split_huge_page + * folio can't be freed from under us. NOTE: folio lock + * is needed to serialize against split_huge_page() * when invoked from the VM. */ if (!folio_trylock(folio)) { @@ -809,7 +809,7 @@ static enum scan_result __collapse_huge_ } /* - * Isolate the page to avoid collapsing an hugepage + * Isolate the folio to avoid collapsing a hugepage * currently in use by the VM. */ if (!folio_isolate_lru(folio)) { @@ -921,7 +921,7 @@ static void __collapse_huge_page_copy_fa * Re-establish the PMD to point to the original page table * entry. Restoring PMD needs to be done prior to releasing * pages. Since pages are still isolated and locked here, - * acquiring anon_vma_lock_write is unnecessary. + * acquiring anon_vma_lock_write() is unnecessary. */ pmd_ptl = pmd_lock(vma->vm_mm, pmd); pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); @@ -1095,9 +1095,9 @@ static enum scan_result hugepage_vma_rev return SCAN_VMA_CHECK; /* * Anon VMA expected, the address may be unmapped then - * remapped to file after khugepaged reaquired the mmap_lock. + * remapped to file after khugepaged reacquired the mmap_lock. * - * thp_vma_allowable_orders may return true for qualified file + * thp_vma_allowable_orders() may return true for qualified file * vmas. */ if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap))) @@ -1153,7 +1153,7 @@ static enum scan_result check_pmd_still_ /* * Bring missing pages in from swap, to complete THP collapse. - * Only done if khugepaged_scan_pmd believes it is worthwhile. + * Only done if collapse_scan_pmd() believes it is worthwhile. * * For mTHP orders the function bails on the first swap entry, because * faulting pages back in during collapse could re-populate PTEs that @@ -1221,7 +1221,7 @@ static enum scan_result __collapse_huge_ pte = NULL; /* - * do_swap_page returns VM_FAULT_RETRY with released mmap_lock. + * do_swap_page() returns VM_FAULT_RETRY with released mmap_lock. * Note we treat VM_FAULT_RETRY as VM_FAULT_ERROR here because * we do not retry here and swap entry will remain in pagetable * resulting in later failure. @@ -1285,7 +1285,7 @@ static enum scan_result alloc_charge_fol } /* - * collapse_huge_page expects the mmap_lock to be unlocked before entering and + * collapse_huge_page() expects the mmap_lock to be unlocked before entering and * will always return with the lock unlocked, to avoid holding the mmap_lock * while allocating a THP, as that could trigger direct reclaim/compaction. * Note that the VMA must be rechecked after grabbing the mmap_lock again. @@ -1332,7 +1332,7 @@ static enum scan_result collapse_huge_pa if (unmapped) { /* - * __collapse_huge_page_swapin will return with mmap_lock + * __collapse_huge_page_swapin() will return with mmap_lock * released when it fails. So we jump out_nolock directly in * that case. Continuing to collapse causes inconsistency. */ @@ -1345,8 +1345,8 @@ static enum scan_result collapse_huge_pa mmap_read_unlock(mm); /* * Prevent all access to pagetables with the exception of - * gup_fast later handled by the ptep_clear_flush and the VM - * handled by the anon_vma lock + PG_lock. + * gup_fast later handled by the pmdp_collapse_flush() and the VM + * handled by the anon_vma lock + folio lock. * * UFFDIO_MOVE is prevented to race as well thanks to the * mmap_lock. @@ -1403,9 +1403,9 @@ static enum scan_result collapse_huge_pa spin_lock(pmd_ptl); VM_WARN_ON_ONCE(!pmd_none(*pmd)); /* - * We can only use set_pmd_at when establishing + * We can only use set_pmd_at() when establishing * hugepmds and never for establishing regular pmds that - * points to regular pagetables. Use pmd_populate for that + * points to regular pagetables. Use pmd_populate() for that */ pmd_populate(mm, pmd, pmd_pgtable(_pmd)); spin_unlock(pmd_ptl); @@ -1637,7 +1637,8 @@ static enum scan_result collapse_scan_pm /* * If PMD is the only enabled order, enforce max_ptes_none, otherwise - * scan all pages to populate the bitmap for mTHP collapse. + * scan all pages to populate the bitmap for mTHP collapse. The bitmap + * is then checked again in mthp_collapse() for each attempted order. */ if (enabled_orders != BIT(HPAGE_PMD_ORDER)) max_ptes_none = KHUGEPAGED_MAX_PTES_LIMIT; @@ -1758,12 +1759,9 @@ static enum scan_result collapse_scan_pm /* * Check if the page has any GUP (or other external) pins. * - * Here the check may be racy: - * it may see folio_mapcount() > folio_ref_count(). - * But such case is ephemeral we could always retry collapse - * later. However it may report false positive if the page - * has excessive GUP pins (i.e. 512). Anyway the same check - * will be done again later the risk seems low. + * Here the check is racy, but such cases are ephemeral and + * we can always retry collapse later. Anyway the same + * check will be done again later, so the risk seems to be low. */ if (folio_expected_ref_count(folio) != folio_ref_count(folio)) { result = SCAN_PAGE_COUNT; @@ -1784,7 +1782,7 @@ static enum scan_result collapse_scan_pm out_unmap: pte_unmap_unlock(pte, ptl); if (result == SCAN_SUCCEED) { - /* collapse_huge_page expects the lock to be dropped before calling */ + /* collapse_huge_page() expects the lock to be dropped before calling */ mmap_read_unlock(mm); result = mthp_collapse(mm, start_addr, referenced, unmapped, cc, enabled_orders); _ Patches currently in -mm which might be from nico.pache@linux.dev are