bcache: Make gc wakeup sane, remove set_task_state()

commit be628be09563f8f6e81929efbd7cf3f45c344416 upstream.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Coly Li <colyli@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index 5c391fa..9b80417 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -260,8 +260,7 @@
 
 static inline void wake_up_gc(struct cache_set *c)
 {
-	if (c->gc_thread)
-		wake_up_process(c->gc_thread);
+	wake_up(&c->gc_wait);
 }
 
 #define MAP_DONE	0