From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Subject: mm: migrate: simplify the file-backed pages validation when migrating its mapping There is no need to validate the file-backed page's refcount before trying to freeze the page's expected refcount, instead we can rely on the folio_ref_freeze() to validate if the page has the expected refcount before migrating its mapping. Moreover we are always under the page lock when migrating the page mapping, which means nowhere else can remove it from the page cache, so we can remove the xas_load() validation under the i_pages lock. Link: https://lkml.kernel.org/r/cover.1629447552.git.baolin.wang@xxxxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/df4c129fd8e86a95dbc55f4663d77441cc0d3bd1.1629447552.git.baolin.wang@xxxxxxxxxxxxxxxxx Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Cc: Alistair Popple <apopple@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/migrate.c | 6 ------ 1 file changed, 6 deletions(-) --- a/mm/migrate.c~mm-migrate-simplify-the-file-backed-pages-validation-when-migrating-its-mapping +++ a/mm/migrate.c @@ -404,12 +404,6 @@ int folio_migrate_mapping(struct address newzone = folio_zone(newfolio); xas_lock_irq(&xas); - if (folio_ref_count(folio) != expected_count || - xas_load(&xas) != folio) { - xas_unlock_irq(&xas); - return -EAGAIN; - } - if (!folio_ref_freeze(folio, expected_count)) { xas_unlock_irq(&xas); return -EAGAIN; _
