[3.11.y.z extended stable] Patch "mm: numa: defer TLB flush for THP migration as long as possible" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From e7df708659b6254627ab26004fd2dc6a0191072b Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman at suse.de>
Date: Tue, 7 Jan 2014 14:00:48 +0000
Subject: mm: numa: defer TLB flush for THP migration as long as possible

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: Luis Henriques <luis.henriques 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 37a8cd8..31950d6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1372,13 +1372,6 @@ 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 c033a04..5130147 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1702,6 +1702,9 @@ 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