[PATCH 3.8 094/166] mm: numa: defer TLB flush for THP migration as long as possible

[Kamal Mostafa]

3.8.13.16 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mel Gorman <mgorman at suse.de>

commit b0943d61b8fa420180f92f64ef67662b4f6cc493 upstream.

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 at suse.de>
Reviewed-by: Rik van Riel <riel at redhat.com>
Cc: Alex Thorlton <athorlton at sgi.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 mm/huge_memory.c | 7 -------
 mm/migrate.c     | 3 +++
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b43f35a..21ca328 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1379,13 +1379,6 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	}
 
 	/*
-	 * The page_table_lock above provides a memory barrier
-	 * with change_protection_range.
-	 */
-	if (mm_tlb_flush_pending(mm))
-		flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
-
-	/*
 	 * Migrate the THP to the requested node, returns with page unlocked
 	 * and pmd_numa cleared.
 	 */
diff --git a/mm/migrate.c b/mm/migrate.c
index 8e117b7..8edfa00 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1715,6 +1715,9 @@ 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);
-- 
1.8.3.2