move d_rcu from overlapping d_child to overlapping d_alias

commit 946e51f2bf37f1656916eb75bd0742ba33983c28 upstream.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.2:
 - Apply name changes in all the different places we use d_alias and d_child
 - Move the WARN_ON() in __d_free() to d_free() as we don't have dentry_free()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[lizf: Backported to 3.4:
 - adjust context
 - need one more name change in debugfs]
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index b1cdb0a..54effed 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -100,7 +100,7 @@
 	p = prev;
 	spin_lock(&p->d_lock);
 again:
-	next = p->d_u.d_child.next;
+	next = p->d_child.next;
 start:
 	if (next == &root->d_subdirs) {
 		spin_unlock(&p->d_lock);
@@ -109,7 +109,7 @@
 		return NULL;
 	}
 
-	q = list_entry(next, struct dentry, d_u.d_child);
+	q = list_entry(next, struct dentry, d_child);
 
 	spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
 	/* Negative dentry - try next */
@@ -166,13 +166,13 @@
 				goto relock;
 			}
 			spin_unlock(&p->d_lock);
-			next = p->d_u.d_child.next;
+			next = p->d_child.next;
 			p = parent;
 			if (next != &parent->d_subdirs)
 				break;
 		}
 	}
-	ret = list_entry(next, struct dentry, d_u.d_child);
+	ret = list_entry(next, struct dentry, d_child);
 
 	spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
 	/* Negative dentry - try next */
@@ -457,7 +457,7 @@
 	spin_lock(&sbi->lookup_lock);
 	spin_lock(&expired->d_parent->d_lock);
 	spin_lock_nested(&expired->d_lock, DENTRY_D_LOCK_NESTED);
-	list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
+	list_move(&expired->d_parent->d_subdirs, &expired->d_child);
 	spin_unlock(&expired->d_lock);
 	spin_unlock(&expired->d_parent->d_lock);
 	spin_unlock(&sbi->lookup_lock);
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 8c4292f..4117604 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -651,7 +651,7 @@
 	/* only consider parents below dentrys in the root */
 	if (IS_ROOT(parent->d_parent))
 		return;
-	d_child = &dentry->d_u.d_child;
+	d_child = &dentry->d_child;
 	/* Set parent managed if it's becoming empty */
 	if (d_child->next == &parent->d_subdirs &&
 	    d_child->prev == &parent->d_subdirs)