mm: numa: avoid unnecessary disruption of NUMA hinting during migration

do_huge_pmd_numa_page() handles the case where there is parallel THP
migration.  However, by the time it is checked the NUMA hinting
information has already been disrupted.  This patch adds an earlier
check with some helpers.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index a987525810ae..cfb419085261 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1655,6 +1655,18 @@ int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
         return 1;
 }
 
+bool pmd_trans_migrating(pmd_t pmd)
+{
+        struct page *page = pmd_page(pmd);
+        return PageLocked(page);
+}
+
+void wait_migrate_huge_page(struct anon_vma *anon_vma, pmd_t *pmd)
+{
+        struct page *page = pmd_page(*pmd);
+        wait_on_page_locked(page);
+}
+
 /*
  * Attempt to migrate a misplaced page to the specified destination
  * node. Caller is expected to have an elevated reference count on