affs: free affs_sb_info with kfree_rcu()

one of the flags in it is used by ->d_hash()/->d_compare()

Reviewed-by: Christian Brauner <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/affs/affs.h

···
 	int work_queued;		/* non-zero delayed work is queued */
 	struct delayed_work sb_work;	/* superblock flush delayed work */
 	spinlock_t work_lock;		/* protects sb_work and work_queued */
+	struct rcu_head rcu;
 };
 
 #define AFFS_MOUNT_SF_INTL		0x0001 /* International filesystem. */

fs/affs/super.c

···
 		affs_brelse(sbi->s_root_bh);
 		kfree(sbi->s_prefix);
 		mutex_destroy(&sbi->s_bmlock);
-		kfree(sbi);
+		kfree_rcu(sbi, rcu);
 	}
 }