adfs: delayed freeing of sbi

makes ->d_hash() and ->d_compare() safety in RCU mode independent
from vfsmount_lock.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/adfs/adfs.h b/fs/adfs/adfs.h
index 585adaf..c770337 100644
--- a/fs/adfs/adfs.h
+++ b/fs/adfs/adfs.h
@@ -43,9 +43,12 @@
  * ADFS file system superblock data in memory
  */
 struct adfs_sb_info {
-	struct adfs_discmap *s_map;	/* bh list containing map		 */
-	struct adfs_dir_ops *s_dir;	/* directory operations			 */
-
+	union { struct {
+		struct adfs_discmap *s_map;	/* bh list containing map	 */
+		struct adfs_dir_ops *s_dir;	/* directory operations		 */
+		};
+		struct rcu_head rcu;		/* used only at shutdown time	 */
+	};
 	kuid_t		s_uid;		/* owner uid				 */
 	kgid_t		s_gid;		/* owner gid				 */
 	umode_t		s_owner_mask;	/* ADFS owner perm -> unix perm		 */