[PATCH] mm: migration page refcounting fix

Migration code currently does not take a reference to target page
properly, so between unlocking the pte and trying to take a new
reference to the page with isolate_lru_page, anything could happen to
it.

Fix this by holding the pte lock until we get a chance to elevate the
refcount.

Other small cleanups while we're here.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/mm/swap.c b/mm/swap.c
index cbb48e721ab..bc2442a7b0e 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -174,6 +174,32 @@ void lru_add_drain(void)
 	put_cpu();
 }
 
+#ifdef CONFIG_NUMA
+static void lru_add_drain_per_cpu(void *dummy)
+{
+	lru_add_drain();
+}
+
+/*
+ * Returns 0 for success
+ */
+int lru_add_drain_all(void)
+{
+	return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
+}
+
+#else
+
+/*
+ * Returns 0 for success
+ */
+int lru_add_drain_all(void)
+{
+	lru_add_drain();
+	return 0;
+}
+#endif
+
 /*
  * This path almost never happens for VM activity - pages are normally
  * freed via pagevecs.  But it gets used by networking.