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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Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan Subject: [PATCH 4/8] mm/khugepaged: fix outdated comments Date: Mon, 6 Jul 2026 09:44:51 -0600 Message-ID: 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> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: mQWb-vkEHiqLSTB7VaMEzjbVSLuiOxC-MUoBg4ROVdA_1783352688 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Stat-Signature: wzd631g5h9ja4ww6unad1sskagd55q9j X-Rspamd-Queue-Id: 017B2140004 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783352693-757287 X-HE-Meta: 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 MMaAFAo/ TWc8LXE5eeUot6d5yIq6Bc/dkaIc7OF3VXcJK1wd4RCoppb71lfd4KJwKo3yt6Qb0gGT3TEm8jttduw7UeemG+ZJn9A85rJ84Z6hX84OWQCN++UeMMdMWTr30lIs4YDuFGB+U/nYWhM8xpgH3Zdg6mz0LCN1xuDkh+psejvBH16/7y4YRMmQVkP9x3d6NeFJYkWgJEpnBFbBOsPQvIsgxClLY7VvQ48pSUgjV6Lhp+0bCJz88uOnaRChksMhA3vy5Eh9gfnknivhmTVPgyJg/FYFgC+U7gUMqMJXlhCIu5+Za4+lbSnA26kP0wrakjWeqraZTkim6v4i4VpqRtWA1Y5xEWg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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