1 files changed, 44 insertions, 11 deletions

diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
index 98317fdc33b5..f114d388570a 100644
--- a/fs/xfs/xfs_trans_priv.h
+++ b/fs/xfs/xfs_trans_priv.h
@@ -44,20 +44,33 @@ xfs_log_busy_slot_t		*xfs_trans_add_busy(xfs_trans_t *tp,
                                                     xfs_extlen_t idx);
 
 /*
- * From xfs_trans_ail.c
+ * 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.
  */
-void                    xfs_trans_update_ail(struct xfs_mount *mp,
-                                     struct xfs_log_item *lip, xfs_lsn_t lsn)
-                                     __releases(mp->m_ail_lock);
-void                    xfs_trans_delete_ail(struct xfs_mount *mp,
-                                     struct xfs_log_item *lip)
-                                     __releases(mp->m_ail_lock);
-struct xfs_log_item     *xfs_trans_first_ail(struct xfs_mount *, int *);
-struct xfs_log_item     *xfs_trans_next_ail(struct xfs_mount *,
-                                     struct xfs_log_item *, int *, int *);
+struct xfs_ail_cursor {
+        struct xfs_ail_cursor   *next;
+        struct xfs_log_item     *item;
+};
 
 /*
- * AIL push thread support
+ * Private AIL structures.
+ *
+ * Eventually we need to drive the locking in here as well.
  */
 struct xfs_ail {
         struct xfs_mount        *xa_mount;
@@ -65,8 +78,28 @@ struct xfs_ail {
         uint                    xa_gen;
         struct task_struct      *xa_task;
         xfs_lsn_t               xa_target;
+        struct xfs_ail_cursor   xa_cursors;
 };
 
+/*
+ * From xfs_trans_ail.c
+ */
+void                    xfs_trans_update_ail(struct xfs_mount *mp,
+                                     struct xfs_log_item *lip, xfs_lsn_t lsn)
+                                     __releases(mp->m_ail_lock);
+void                    xfs_trans_delete_ail(struct xfs_mount *mp,
+                                     struct xfs_log_item *lip)
+                                     __releases(mp->m_ail_lock);
+struct xfs_log_item     *xfs_trans_first_ail(struct xfs_mount *mp,
+                                        struct xfs_ail_cursor *cur);
+struct xfs_log_item     *xfs_trans_next_ail(struct xfs_mount *mp,
+                                        struct xfs_ail_cursor *cur);
+
+void xfs_trans_ail_cursor_init(struct xfs_ail *ailp,
+                                        struct xfs_ail_cursor *cur);
+void xfs_trans_ail_cursor_done(struct xfs_ail *ailp,
+                                        struct xfs_ail_cursor *cur);
+
 long    xfsaild_push(struct xfs_ail *, xfs_lsn_t *);
 void    xfsaild_wakeup(struct xfs_ail *, xfs_lsn_t);
 int     xfsaild_start(struct xfs_ail *);