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

Mel Gorman · torvalds · commit b0943d61b8fa · 2013-12-18T19:04:51.000-08:00
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 &lt;mgorman@suse.de&gt;
Reviewed-by: Rik van Riel &lt;riel@redhat.com&gt;
Cc: Alex Thorlton &lt;athorlton@sgi.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
@@ -1376,13 +1376,6 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		goto clear_pmdnuma;
 	}
 
-	/*
-	 * 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
@@ -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);

Original file line number	Diff line number	Diff line change
`@@ -1759,6 +1759,9 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,`
`1759`	`1759`	`goto out_fail;`
`1760`	`1760`	`}`
`1761`	`1761`
	`1762`	`+ if (mm_tlb_flush_pending(mm))`
	`1763`	`+ flush_tlb_range(vma, mmun_start, mmun_end);`
	`1764`	`+`
`1762`	`1765`	`/* Prepare a page as a migration target */`
`1763`	`1766`	`__set_page_locked(new_page);`
`1764`	`1767`	`SetPageSwapBacked(new_page);`