--- zzzz-none-000/linux-3.10.107/fs/btrfs/delayed-ref.h	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/fs/btrfs/delayed-ref.h	2021-02-04 17:41:59.000000000 +0000
@@ -24,9 +24,25 @@
 #define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
 #define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */
 
+/*
+ * XXX: Qu: I really hate the design that ref_head and tree/data ref shares the
+ * same ref_node structure.
+ * Ref_head is in a higher logic level than tree/data ref, and duplicated
+ * bytenr/num_bytes in ref_node is really a waste or memory, they should be
+ * referred from ref_head.
+ * This gets more disgusting after we use list to store tree/data ref in
+ * ref_head. Must clean this mess up later.
+ */
 struct btrfs_delayed_ref_node {
+	/*
+	 * ref_head use rb tree, stored in ref_root->href.
+	 * indexed by bytenr
+	 */
 	struct rb_node rb_node;
 
+	/*data/tree ref use list, stored in ref_head->ref_list. */
+	struct list_head list;
+
 	/* the starting bytenr of the extent */
 	u64 bytenr;
 
@@ -81,9 +97,31 @@
 	 */
 	struct mutex mutex;
 
-	struct list_head cluster;
+	spinlock_t lock;
+	struct list_head ref_list;
+
+	struct rb_node href_node;
 
 	struct btrfs_delayed_extent_op *extent_op;
+
+	/*
+	 * This is used to track the final ref_mod from all the refs associated
+	 * with this head ref, this is not adjusted as delayed refs are run,
+	 * this is meant to track if we need to do the csum accounting or not.
+	 */
+	int total_ref_mod;
+
+	/*
+	 * For qgroup reserved space freeing.
+	 *
+	 * ref_root and reserved will be recorded after
+	 * BTRFS_ADD_DELAYED_EXTENT is called.
+	 * And will be used to free reserved qgroup space at
+	 * run_delayed_refs() time.
+	 */
+	u64 qgroup_ref_root;
+	u64 qgroup_reserved;
+
 	/*
 	 * when a new extent is allocated, it is just reserved in memory
 	 * The actual extent isn't inserted into the extent allocation tree
@@ -98,6 +136,7 @@
 	 */
 	unsigned int must_insert_reserved:1;
 	unsigned int is_data:1;
+	unsigned int processing:1;
 };
 
 struct btrfs_delayed_tree_ref {
@@ -116,7 +155,11 @@
 };
 
 struct btrfs_delayed_ref_root {
-	struct rb_root root;
+	/* head ref rbtree */
+	struct rb_root href_root;
+
+	/* dirty extent records */
+	struct rb_root dirty_extent_root;
 
 	/* this spin lock protects the rbtree and the entries inside */
 	spinlock_t lock;
@@ -124,7 +167,7 @@
 	/* how many delayed ref updates we've queued, used by the
 	 * throttling code
 	 */
-	unsigned long num_entries;
+	atomic_t num_entries;
 
 	/* total number of head nodes in tree */
 	unsigned long num_heads;
@@ -132,14 +175,7 @@
 	/* total number of head nodes ready for processing */
 	unsigned long num_heads_ready;
 
-	/*
-	 * bumped when someone is making progress on the delayed
-	 * refs, so that other procs know they are just adding to
-	 * contention intead of helping
-	 */
-	atomic_t procs_running_refs;
-	atomic_t ref_seq;
-	wait_queue_head_t wait;
+	u64 pending_csums;
 
 	/*
 	 * set when the tree is flushing before a transaction commit,
@@ -149,6 +185,14 @@
 	int flushing;
 
 	u64 run_delayed_start;
+
+	/*
+	 * To make qgroup to skip given root.
+	 * This is for snapshot, as btrfs_qgroup_inherit() will manully
+	 * modify counters for snapshot and its source, so we should skip
+	 * the snapshot in new_root/old_roots or it will get calculated twice
+	 */
+	u64 qgroup_to_skip;
 };
 
 extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
@@ -199,15 +243,16 @@
 			       struct btrfs_trans_handle *trans,
 			       u64 bytenr, u64 num_bytes, u64 parent,
 			       u64 ref_root, int level, int action,
-			       struct btrfs_delayed_extent_op *extent_op,
-			       int for_cow);
+			       struct btrfs_delayed_extent_op *extent_op);
 int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
 			       struct btrfs_trans_handle *trans,
 			       u64 bytenr, u64 num_bytes,
 			       u64 parent, u64 ref_root,
-			       u64 owner, u64 offset, int action,
-			       struct btrfs_delayed_extent_op *extent_op,
-			       int for_cow);
+			       u64 owner, u64 offset, u64 reserved, int action,
+			       struct btrfs_delayed_extent_op *extent_op);
+int btrfs_add_delayed_qgroup_reserve(struct btrfs_fs_info *fs_info,
+				     struct btrfs_trans_handle *trans,
+				     u64 ref_root, u64 bytenr, u64 num_bytes);
 int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
 				struct btrfs_trans_handle *trans,
 				u64 bytenr, u64 num_bytes,
@@ -226,34 +271,15 @@
 	mutex_unlock(&head->mutex);
 }
 
-int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
-			   struct list_head *cluster, u64 search_start);
-void btrfs_release_ref_cluster(struct list_head *cluster);
+
+struct btrfs_delayed_ref_head *
+btrfs_select_ref_head(struct btrfs_trans_handle *trans);
 
 int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
 			    struct btrfs_delayed_ref_root *delayed_refs,
 			    u64 seq);
 
 /*
- * delayed refs with a ref_seq > 0 must be held back during backref walking.
- * this only applies to items in one of the fs-trees. for_cow items never need
- * to be held back, so they won't get a ref_seq number.
- */
-static inline int need_ref_seq(int for_cow, u64 rootid)
-{
-	if (for_cow)
-		return 0;
-
-	if (rootid == BTRFS_FS_TREE_OBJECTID)
-		return 1;
-
-	if ((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)
-		return 1;
-
-	return 0;
-}
-
-/*
  * a node might live in a head or a regular ref, this lets you
  * test for the proper type to use.
  */