diff mbox series

[v2,09/10] mm/thp: remap_page() is only needed on anonymous THP

Message ID f987bc44-f28e-688d-2424-b4722153ed8@google.com (mailing list archive)
State New
Headers show
Series mm/thp: fix THP splitting unmap BUGs and related (fwd) | expand

Commit Message

Hugh Dickins June 9, 2021, 4:27 a.m. UTC
THP splitting's unmap_page() only sets TTU_SPLIT_FREEZE when PageAnon,
and migration entries are only inserted when TTU_MIGRATION (unused here)
or TTU_SPLIT_FREEZE is set: so it's just a waste of time for remap_page()
to search for migration entries to remove when !PageAnon.

Fixes: baa355fd3314 ("thp: file pages support for split_huge_page()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
 mm/huge_memory.c | 5 +++++
 1 file changed, 5 insertions(+)
diff mbox series


diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 6d2a0119fc58..319a1a078451 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2355,6 +2355,7 @@  static void unmap_page(struct page *page)
 	VM_BUG_ON_PAGE(!PageHead(page), page);
+	/* If TTU_SPLIT_FREEZE is ever extended to file, update remap_page() */
 	if (PageAnon(page))
 		ttu_flags |= TTU_SPLIT_FREEZE;
@@ -2366,6 +2367,10 @@  static void unmap_page(struct page *page)
 static void remap_page(struct page *page, unsigned int nr)
 	int i;
+	/* If TTU_SPLIT_FREEZE is ever extended to file, remove this check */
+	if (!PageAnon(page))
+		return;
 	if (PageTransHuge(page)) {
 		remove_migration_ptes(page, page, true);
 	} else {