Merge branch 'topic/acpi' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi into spi-pxa2xx

1 files changed, 15 insertions, 3 deletions

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 9f15bdd9163c..2d7c4c11fc63 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -213,10 +213,10 @@ struct size_class {
 	int size;
 	unsigned int index;
 
-	/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
-	int pages_per_zspage;
 	struct zs_size_stat stats;
 
+	/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
+	int pages_per_zspage;
 	/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
 	bool huge;
 };
@@ -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);