+ * AIL traversal cursor.
+ *
+ * Rather than using a generation number for detecting changes in the ail, use
+ * a cursor that is protected by the ail lock. The aild cursor exists in the
+ * struct xfs_ail, but other traversals can declare it on the stack and link it
+ * to the ail list.
+ *
+ * When an object is deleted from or moved int the AIL, the cursor list is
+ * searched to see if the object is a designated cursor item. If it is, it is
+ * deleted from the cursor so that the next time the cursor is used traversal
+ * will return to the start.
+ *
+ * This means a traversal colliding with a removal will cause a restart of the
+ * list scan, rather than any insertion or deletion anywhere in the list. The
+ * low bit of the item pointer is set if the cursor has been invalidated so
+ * that we can tell the difference between invalidation and reaching the end
+ * of the list to trigger traversal restarts.
+ */
+struct xfs_ail_cursor {
+ struct xfs_ail_cursor *next;
+ struct xfs_log_item *item;
+};
+
+/*
+ * Private AIL structures.
+ *
+ * Eventually we need to drive the locking in here as well.
+ */
+struct xfs_ail {
+ struct xfs_mount *xa_mount;
+ struct list_head xa_ail;
+ uint xa_gen;
+ struct task_struct *xa_task;
+ xfs_lsn_t xa_target;
+ struct xfs_ail_cursor xa_cursors;
+ spinlock_t xa_lock;
+};
+
+/*