logfs: fix a leak in get_sb

a) switch ->put_device() to logfs_super *
b) actually call it on early failures in logfs_get_sb_device()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index 223b673..92ca6fb 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -298,9 +298,9 @@
 	return sync_request(page, bdev, WRITE);
 }
 
-static void bdev_put_device(struct super_block *sb)
+static void bdev_put_device(struct logfs_super *s)
 {
-	close_bdev_exclusive(logfs_super(sb)->s_bdev, FMODE_READ|FMODE_WRITE);
+	close_bdev_exclusive(s->s_bdev, FMODE_READ|FMODE_WRITE);
 }
 
 static int bdev_can_write_buf(struct super_block *sb, u64 ofs)