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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/10/26 07:27, Wandun wrote: > > > On 11/9/26 21:51, David Hildenbrand (Arm) wrote: >> On 11/9/26 10:08, Wandun Chen wrote: >>> From: Wandun Chen >>> >>> try_to_migrate() clears PG_mlocked when unmapping the source folio. >>> For PTE-mapped large folios, remove_migration_pte() restores one PTE at >>> a time, but the rmap helpers only restore mlock for full-folio mappings. >>> This leaves the destination PTE-mapped large folio without PG_mlocked. >>> >>> Restore mlock once all PTEs of the destination folio are restored under >>> a single page table lock. >>> >>> Fixes: dc68badcede4 ("mm: mlock: update mlock_pte_range to handle large folio") >>> Signed-off-by: Wandun Chen >>> --- >>> mm/migrate.c | 10 +++++++++- >>> 1 file changed, 9 insertions(+), 1 deletion(-) >>> >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index 94033c222e04..140e291d4587 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -353,6 +353,7 @@ static bool remove_migration_pte(struct folio *folio, >>> { >>> struct rmap_walk_arg *rmap_walk_arg = arg; >>> DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION); >>> + unsigned long nr_ptes = 0; >>> >>> while (page_vma_mapped_walk(&pvmw)) { >>> rmap_t rmap_flags = RMAP_NONE; >>> @@ -446,9 +447,16 @@ static bool remove_migration_pte(struct folio *folio, >>> else >>> folio_add_file_rmap_pte(folio, new, vma); >>> set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); >>> + >>> + nr_ptes++; >>> } >>> - if (READ_ONCE(vma->vm_flags) & VM_LOCKED) >>> + if (READ_ONCE(vma->vm_flags) & VM_LOCKED) { >>> + if (folio_test_large(folio) && >>> + nr_ptes == folio_nr_pages(folio) && >>> + !(pvmw.flags & PVMW_PGTABLE_CROSSED)) >>> + mlock_vma_folio(folio, vma); >>> mlock_drain_local(); >>> + } >> >> I have the recollection that the next try_to_unmap() would fix that up? Or is >> that not the case? > > It is the case, try_to_unmap() can restore it. However, until reclaim scans > the folio, Mlocked in /proc/meminfo can remain undercounted, giving users > a misleading impression that less memory is locked. > > A similar fix was made in commit > ab521b4142aa ("mm/rmap: improve mlock tracking for large folios"). > > and handles cases where an entire folio is added in one rmap operation. > > However, when a PTE-mapped large folio is migrated, remove_migration_pte() > restores PTEs individually, passing nr_pages = 1 to the rmap helpers, > as a result, PG_mlocked is not set on the destination folio. > > This patch handles that case once the full mapping has been restored, > rather than waiting for try_to_unmap() to restore the mlock state. Please revise the patch description pointing all that out :) Note that ab521b4142aa wasn't a fix (no Fixes:) why should this one here be one? -- Cheers, David