jffs2: Require jffs2_garbage_collect_trigger() to be called with lock held

We're about to call this from a bunch of places which already hold
c->erase_completion_lock, so add an assertion and change its existing
callers to do the same.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
index 3ff50da..55f1dde 100644
--- a/fs/jffs2/background.c
+++ b/fs/jffs2/background.c
@@ -23,10 +23,9 @@
 
 void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
 {
-	spin_lock(&c->erase_completion_lock);
+	assert_spin_locked(&c->erase_completion_lock);
 	if (c->gc_task && jffs2_thread_should_wake(c))
 		send_sig(SIGHUP, c->gc_task, 1);
-	spin_unlock(&c->erase_completion_lock);
 }
 
 /* This must only ever be called when no GC thread is currently running */