From: Baolin Wang Date: Tue, 24 Aug 2021 00:00:15 +0000 (+1000) Subject: mm: migrate: simplify the file-backed pages validation when migrating its mapping X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=2011cec36453f663b7935f8a2a671299defd6b7c;p=users%2Fjedix%2Flinux-maple.git mm: migrate: simplify the file-backed pages validation when migrating its mapping Patch series "Some cleanup for page migration", v3. This patchset does some cleanups and improvements for page migration. This patch (of 4): 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@linux.alibaba.com Link: https://lkml.kernel.org/r/df4c129fd8e86a95dbc55f4663d77441cc0d3bd1.1629447552.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Suggested-by: Matthew Wilcox Cc: Yang Shi Cc: Alistair Popple Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell --- diff --git a/mm/migrate.c b/mm/migrate.c index de46dc375ff9..f686e5de1f9b 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -404,12 +404,6 @@ int folio_migrate_mapping(struct address_space *mapping, 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;