mm: numa: defer TLB flush for THP migration as long as possible

THP migration can fail for a variety of reasons.  Avoid flushing the TLB
to deal with THP migration races until the copy is ready to start.

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, 3 insertions, 0 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index cfb419085261..e9b710201335 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1759,6 +1759,9 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
                 goto out_fail;
         }
 
+        if (mm_tlb_flush_pending(mm))
+                flush_tlb_range(vma, mmun_start, mmun_end);
+
         /* Prepare a page as a migration target */
         __set_page_locked(new_page);
         SetPageSwapBacked(new_page);