X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=mm%2Fzsmalloc.c;h=fc083996e40a6a1c7fb4116b1aecd3f40fab32c7;hb=fe16f4b53f5a0ce564299f402079ab73c9cb8697;hp=9f15bdd9163c2360edf2e070023b6099b683a85c;hpb=819db468b26797d9f53d547dd2a9fe94859a16e0;p=firefly-linux-kernel-4.4.55.git

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 9f15bdd9163c..fc083996e40a 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -309,7 +309,12 @@ static void free_handle(struct zs_pool *pool, unsigned long handle)
 
 static void record_obj(unsigned long handle, unsigned long obj)
 {
-	*(unsigned long *)handle = obj;
+	/*
+	 * lsb of @obj represents handle lock while other bits
+	 * represent object value the handle is pointing so
+	 * updating shouldn't do store tearing.
+	 */
+	WRITE_ONCE(*(unsigned long *)handle, obj);
 }
 
 /* zpool driver */
@@ -1635,6 +1640,13 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
 		free_obj = obj_malloc(d_page, class, handle);
 		zs_object_copy(free_obj, used_obj, class);
 		index++;
+		/*
+		 * record_obj updates handle's value to free_obj and it will
+		 * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
+		 * breaks synchronization using pin_tag(e,g, zs_free) so
+		 * let's keep the lock bit.
+		 */
+		free_obj |= BIT(HANDLE_PIN_BIT);
 		record_obj(handle, free_obj);
 		unpin_tag(handle);
 		obj_free(pool, class, used_obj);