list.h: new helper - hlist_add_fake()

Make node look as if it was on hlist, with hlist_del()
working correctly.  Usable without any locking...

Convert a couple of places where we want to do that to
inode->i_hash.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/hfsplus/inode.c

@@ -211,7 +211,7 @@ static struct dentry *hfsplus_file_lookup(struct inode *dir, struct dentry *dent
 	 * appear hashed, but do not put on any lists.  hlist_del()
 	 * will work fine and require no locking.
 	 */
-	inode->i_hash.pprev = &inode->i_hash.next;
+	hlist_add_fake(&inode->i_hash);
 
 	mark_inode_dirty(inode);
 out:

fs/jfs/jfs_imap.c

@@ -497,7 +497,7 @@ struct inode *diReadSpecial(struct super_block *sb, ino_t inum, int secondary)
 	 * appear hashed, but do not put on any lists.  hlist_del()
 	 * will work fine and require no locking.
 	 */
-	ip->i_hash.pprev = &ip->i_hash.next;
+	hlist_add_fake(&ip->i_hash);
 
 	return (ip);
 }

include/linux/list.h

@@ -636,6 +636,12 @@ static inline void hlist_add_after(struct hlist_node *n,
 		next->next->pprev  = &next->next;
 }
 
+/* after that we'll appear to be on some hlist and hlist_del will work */
+static inline void hlist_add_fake(struct hlist_node *n)
+{
+	n->pprev = &n->next;
+}
+
 /*
  * Move a list from one list head to another. Fixup the pprev
  * reference of the first entry if it exists.