From mboxrd@z Thu Jan 1 00:00:00 1970 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 3D01239E9AC for ; Mon, 6 Jul 2026 15:44:56 +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=1783352698; cv=none; b=Riw3SKDUtGASPpTqeJh4Z5fdeIr6tjNINXkN2SdH1MimOD26Q1f3R/ijm8FAGx5OVNbpD4dyTWT+8NMmwpAZxDGg7pOPTd9RT5fIAFlLWDLXsQjPd4bTHnD/RWtKvf4Pmh2G+I4AsFs534PxN0X4A6utzGoqWxT/J7V9rs+sImg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783352698; c=relaxed/simple; bh=VTDU9uHVEExUSUT63GZ613KKDdeEO+fQjsjgAeem8B0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TSxtTNxgceUHEL89i4FloxjcZiHhuU+vrSIv6pcpg0vyVUImqxpe4OrCYjFlm3c7A7DGaMpInAu5H9mc57wpDVtaEg3G84e+sqlml8F8D/JLd4SWZJV01q1ANjX0zqIdEEVYfYW1pbh3PGy54nZixYohw8pTNQXcnoBmQqSEIlQ= 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=ODO2CMJ7; 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="ODO2CMJ7" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783352696; 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=vuuBIdIeisRjmlr2FFD7LVa5vjdcMT2dmalgoXzIXs0=; b=ODO2CMJ7OebCMq0zteZI2xEGFtgfJtL+vDcqN/QD8JaDJdsRRZsLlWzYlef5GqZ333ma6a oVsHD3aA0Q8zziXTPlkjALC0KHFQBKEKyKbTyKJI746uJLht3KksGnpIvqY7jbYyQZ0HgZ cgCkJWiHAaxUbkYJ46P/K9Y/pvoZMk8= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-526-RqYnpzjwPraF3_-W_NKuoA-1; Mon, 06 Jul 2026 11:44:51 -0400 X-MC-Unique: RqYnpzjwPraF3_-W_NKuoA-1 X-Mimecast-MFC-AGG-ID: RqYnpzjwPraF3_-W_NKuoA_1783352688 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 109601955F18; Mon, 6 Jul 2026 15:44:48 +0000 (UTC) Received: from p1.redhat.com (unknown [10.22.58.4]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id A66ED195604B; Mon, 6 Jul 2026 15:44:39 +0000 (UTC) From: Nico Pache To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Nico Pache , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan Subject: [PATCH 4/8] mm/khugepaged: fix outdated comments Date: Mon, 6 Jul 2026 09:44:51 -0600 Message-ID: <20260706154500.39178-5-npache@redhat.com> In-Reply-To: <20260706154500.39178-1-npache@redhat.com> References: <20260706154500.39178-1-npache@redhat.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 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). Assisted-by: Cursor(claude-sonnet-4):4.6 Signed-off-by: Nico Pache --- mm/khugepaged.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 7047253a6fb6..676f75773a6c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -619,7 +619,7 @@ void __khugepaged_exit(struct mm_struct *mm) /* * 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. */ @@ -792,7 +792,7 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, /* * We can do it before folio_isolate_lru because the - * folio can't be freed from under us. NOTE: PG_lock + * folio can't be freed from under us. NOTE: folio lock * is needed to serialize against split_huge_page * when invoked from the VM. */ @@ -819,7 +819,7 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, } /* - * 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)) { @@ -1104,7 +1104,7 @@ static enum scan_result hugepage_vma_revalidate(struct mm_struct *mm, unsigned l 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 * vmas. @@ -1162,7 +1162,7 @@ static enum scan_result check_pmd_still_valid(struct mm_struct *mm, /* * 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 @@ -1354,8 +1354,8 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long s 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. @@ -1767,12 +1767,9 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, /* * 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 case is ephemeral and + * we could always retry collapse later. Anyway the same + * check will be done again later the risk seems low. */ if (folio_expected_ref_count(folio) != folio_ref_count(folio)) { result = SCAN_PAGE_COUNT; -- 2.54.0