struct file: use anonymous union member for rcuhead and llist

Once upon a time we couldn't afford anon unions; these days minimal
gcc version had been raised enough to take care of that.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/file_table.c

@@ -45,7 +45,7 @@ static struct percpu_counter nr_files __cacheline_aligned_in_smp;
 
 static void file_free_rcu(struct rcu_head *head)
 {
-	struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
+	struct file *f = container_of(head, struct file, f_rcuhead);
 
 	put_cred(f->f_cred);
 	kmem_cache_free(filp_cachep, f);
@@ -56,7 +56,7 @@ static inline void file_free(struct file *f)
 	security_file_free(f);
 	if (!(f->f_mode & FMODE_NOACCOUNT))
 		percpu_counter_dec(&nr_files);
-	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
+	call_rcu(&f->f_rcuhead, file_free_rcu);
 }
 
 /*
@@ -142,7 +142,7 @@ static struct file *__alloc_file(int flags, const struct cred *cred)
 	f->f_cred = get_cred(cred);
 	error = security_file_alloc(f);
 	if (unlikely(error)) {
-		file_free_rcu(&f->f_u.fu_rcuhead);
+		file_free_rcu(&f->f_rcuhead);
 		return ERR_PTR(error);
 	}
 
@@ -341,13 +341,13 @@ static void delayed_fput(struct work_struct *unused)
 	struct llist_node *node = llist_del_all(&delayed_fput_list);
 	struct file *f, *t;
 
-	llist_for_each_entry_safe(f, t, node, f_u.fu_llist)
+	llist_for_each_entry_safe(f, t, node, f_llist)
 		__fput(f);
 }
 
 static void ____fput(struct callback_head *work)
 {
-	__fput(container_of(work, struct file, f_u.fu_rcuhead));
+	__fput(container_of(work, struct file, f_rcuhead));
 }
 
 /*
@@ -374,8 +374,8 @@ void fput(struct file *file)
 		struct task_struct *task = current;
 
 		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
-			init_task_work(&file->f_u.fu_rcuhead, ____fput);
-			if (!task_work_add(task, &file->f_u.fu_rcuhead, TWA_RESUME))
+			init_task_work(&file->f_rcuhead, ____fput);
+			if (!task_work_add(task, &file->f_rcuhead, TWA_RESUME))
 				return;
 			/*
 			 * After this task has run exit_task_work(),
@@ -384,7 +384,7 @@ void fput(struct file *file)
 			 */
 		}
 
-		if (llist_add(&file->f_u.fu_llist, &delayed_fput_list))
+		if (llist_add(&file->f_llist, &delayed_fput_list))
 			schedule_delayed_work(&delayed_fput_work, 1);
 	}
 }

include/linux/fs.h

@@ -924,9 +924,9 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
 
 struct file {
 	union {
-		struct llist_node	fu_llist;
-		struct rcu_head 	fu_rcuhead;
-	} f_u;
+		struct llist_node	f_llist;
+		struct rcu_head 	f_rcuhead;
+	};
 	struct path		f_path;
 	struct inode		*f_inode;	/* cached value */
 	const struct file_operations	*f_op;