diff --git a/include/kerncompat.h b/include/kerncompat.h
index 4ba6b3dc..18b474f6 100644
--- a/include/kerncompat.h
+++ b/include/kerncompat.h
@@ -684,6 +684,11 @@ static inline bool refcount_dec_and_test(refcount_t *ref)
 	return ref->refs == 0;
 }
 
+static inline int refcount_read(const refcount_t *ref)
+{
+	return ref->refs;
+}
+
 typedef u32 blk_status_t;
 typedef u32 blk_opf_t;
 typedef int atomic_t;
@@ -813,6 +818,8 @@ static inline void lockdep_assert_held_read(struct rw_semaphore *sem)
 {
 }
 
+#define lockdep_assert_held(sem)
+
 static inline bool cond_resched_lock(spinlock_t *lock)
 {
 	return false;
diff --git a/kernel-shared/delayed-ref.c b/kernel-shared/delayed-ref.c
index a6b92ecf..9b24001a 100644
--- a/kernel-shared/delayed-ref.c
+++ b/kernel-shared/delayed-ref.c
@@ -22,6 +22,10 @@
 #include "kernel-shared/transaction.h"
 #include "kernel-shared/messages.h"
 
+struct kmem_cache *btrfs_delayed_ref_head_cachep;
+struct kmem_cache *btrfs_delayed_tree_ref_cachep;
+struct kmem_cache *btrfs_delayed_data_ref_cachep;
+struct kmem_cache *btrfs_delayed_extent_op_cachep;
 /*
  * delayed back reference update tracking.  For subvolume trees
  * we queue up extent allocations and backref maintenance for
@@ -51,6 +55,34 @@ static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref1,
 	return 0;
 }
 
+/*
+ * compare two delayed data backrefs with same bytenr and type
+ */
+static int comp_data_refs(struct btrfs_delayed_data_ref *ref1,
+			  struct btrfs_delayed_data_ref *ref2)
+{
+	if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
+		if (ref1->root < ref2->root)
+			return -1;
+		if (ref1->root > ref2->root)
+			return 1;
+		if (ref1->objectid < ref2->objectid)
+			return -1;
+		if (ref1->objectid > ref2->objectid)
+			return 1;
+		if (ref1->offset < ref2->offset)
+			return -1;
+		if (ref1->offset > ref2->offset)
+			return 1;
+	} else {
+		if (ref1->parent < ref2->parent)
+			return -1;
+		if (ref1->parent > ref2->parent)
+			return 1;
+	}
+	return 0;
+}
+
 static int comp_refs(struct btrfs_delayed_ref_node *ref1,
 		     struct btrfs_delayed_ref_node *ref2,
 		     bool check_seq)
@@ -66,8 +98,8 @@ static int comp_refs(struct btrfs_delayed_ref_node *ref1,
 		ret = comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref1),
 				     btrfs_delayed_node_to_tree_ref(ref2));
 	else
-		BUG();
-
+		ret = comp_data_refs(btrfs_delayed_node_to_data_ref(ref1),
+				     btrfs_delayed_node_to_data_ref(ref2));
 	if (ret)
 		return ret;
 	if (check_seq) {
@@ -299,7 +331,7 @@ again:
 				href_node);
 	}
 
-	head->processing = 1;
+	head->processing = true;
 	WARN_ON(delayed_refs->num_heads_ready == 0);
 	delayed_refs->num_heads_ready--;
 	delayed_refs->run_delayed_start = head->bytenr +
@@ -307,6 +339,20 @@ again:
 	return head;
 }
 
+void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
+			   struct btrfs_delayed_ref_head *head)
+{
+	lockdep_assert_held(&delayed_refs->lock);
+	lockdep_assert_held(&head->lock);
+
+	rb_erase(&head->href_node, &delayed_refs->href_root);
+	RB_CLEAR_NODE(&head->href_node);
+	atomic_dec(&delayed_refs->num_entries);
+	delayed_refs->num_heads--;
+	if (!head->processing)
+		delayed_refs->num_heads_ready--;
+}
+
 /*
  * Helper to insert the ref_node to the tail or merge with tail.
  *
@@ -431,7 +477,7 @@ static void init_delayed_ref_head(struct btrfs_delayed_ref_head *head_ref,
 				  bool is_system)
 {
 	int count_mod = 1;
-	int must_insert_reserved = 0;
+	bool must_insert_reserved = false;
 
 	/* If reserved is provided, it must be a data extent. */
 	BUG_ON(!is_data && reserved);
@@ -456,11 +502,11 @@ static void init_delayed_ref_head(struct btrfs_delayed_ref_head *head_ref,
 	 * BTRFS_ADD_DELAYED_REF because other special casing is not required.
 	 */
 	if (action == BTRFS_ADD_DELAYED_EXTENT)
-		must_insert_reserved = 1;
+		must_insert_reserved = true;
 	else
-		must_insert_reserved = 0;
+		must_insert_reserved = false;
 
-	head_ref->refs = 1;
+	refcount_set(&head_ref->refs, 1);
 	head_ref->bytenr = bytenr;
 	head_ref->num_bytes = num_bytes;
 	head_ref->ref_mod = count_mod;
@@ -470,7 +516,7 @@ static void init_delayed_ref_head(struct btrfs_delayed_ref_head *head_ref,
 	head_ref->ref_tree = RB_ROOT;
 	INIT_LIST_HEAD(&head_ref->ref_add_list);
 	RB_CLEAR_NODE(&head_ref->href_node);
-	head_ref->processing = 0;
+	head_ref->processing = false;
 	head_ref->total_ref_mod = count_mod;
 }
 
@@ -546,7 +592,7 @@ static void init_delayed_ref_common(struct btrfs_fs_info *fs_info,
 	if (action == BTRFS_ADD_DELAYED_EXTENT)
 		action = BTRFS_ADD_DELAYED_REF;
 
-	ref->refs = 1;
+	refcount_set(&ref->refs, 1);
 	ref->bytenr = bytenr;
 	ref->num_bytes = num_bytes;
 	ref->ref_mod = 1;
@@ -642,3 +688,47 @@ void btrfs_destroy_delayed_refs(struct btrfs_trans_handle *trans)
 		ASSERT(cleanup_ref_head(trans, fs_info, head) == 0);
 	}
 }
+
+void __cold btrfs_delayed_ref_exit(void)
+{
+	kmem_cache_destroy(btrfs_delayed_ref_head_cachep);
+	kmem_cache_destroy(btrfs_delayed_tree_ref_cachep);
+	kmem_cache_destroy(btrfs_delayed_data_ref_cachep);
+	kmem_cache_destroy(btrfs_delayed_extent_op_cachep);
+}
+
+int __init btrfs_delayed_ref_init(void)
+{
+	btrfs_delayed_ref_head_cachep = kmem_cache_create(
+				"btrfs_delayed_ref_head",
+				sizeof(struct btrfs_delayed_ref_head), 0,
+				SLAB_MEM_SPREAD, NULL);
+	if (!btrfs_delayed_ref_head_cachep)
+		goto fail;
+
+	btrfs_delayed_tree_ref_cachep = kmem_cache_create(
+				"btrfs_delayed_tree_ref",
+				sizeof(struct btrfs_delayed_tree_ref), 0,
+				SLAB_MEM_SPREAD, NULL);
+	if (!btrfs_delayed_tree_ref_cachep)
+		goto fail;
+
+	btrfs_delayed_data_ref_cachep = kmem_cache_create(
+				"btrfs_delayed_data_ref",
+				sizeof(struct btrfs_delayed_data_ref), 0,
+				SLAB_MEM_SPREAD, NULL);
+	if (!btrfs_delayed_data_ref_cachep)
+		goto fail;
+
+	btrfs_delayed_extent_op_cachep = kmem_cache_create(
+				"btrfs_delayed_extent_op",
+				sizeof(struct btrfs_delayed_extent_op), 0,
+				SLAB_MEM_SPREAD, NULL);
+	if (!btrfs_delayed_extent_op_cachep)
+		goto fail;
+
+	return 0;
+fail:
+	btrfs_delayed_ref_exit();
+	return -ENOMEM;
+}
diff --git a/kernel-shared/delayed-ref.h b/kernel-shared/delayed-ref.h
index 14e78704..6f817b1f 100644
--- a/kernel-shared/delayed-ref.h
+++ b/kernel-shared/delayed-ref.h
@@ -22,6 +22,8 @@
 
 #include "kerncompat.h"
 
+struct btrfs_block_rsv;
+
 /* these are the possible values of struct btrfs_delayed_ref_node->action */
 #define BTRFS_ADD_DELAYED_REF    1 /* add one backref to the tree */
 #define BTRFS_DROP_DELAYED_REF   2 /* delete one backref from the tree */
@@ -47,7 +49,7 @@ struct btrfs_delayed_ref_node {
 	u64 seq;
 
 	/* ref count on this data structure */
-	u64 refs;
+	refcount_t refs;
 
 	/*
 	 * how many refs is this entry adding or deleting.  For
@@ -85,14 +87,26 @@ struct btrfs_delayed_extent_op {
 struct btrfs_delayed_ref_head {
 	u64 bytenr;
 	u64 num_bytes;
-	u64 refs;
+	/*
+	 * For insertion into struct btrfs_delayed_ref_root::href_root.
+	 * Keep it in the same cache line as 'bytenr' for more efficient
+	 * searches in the rbtree.
+	 */
+	struct rb_node href_node;
+	/*
+	 * the mutex is held while running the refs, and it is also
+	 * held when checking the sum of reference modifications.
+	 */
+	struct mutex mutex;
 
+	refcount_t refs;
+
+	/* Protects 'ref_tree' and 'ref_add_list'. */
+	spinlock_t lock;
 	struct rb_root ref_tree;
 	/* accumulate add BTRFS_ADD_DELAYED_REF nodes to this ref_add_list. */
 	struct list_head ref_add_list;
 
-	struct rb_node href_node;
-
 	struct btrfs_delayed_extent_op *extent_op;
 
 	/*
@@ -122,10 +136,10 @@ struct btrfs_delayed_ref_head {
 	 * we need to update the in ram accounting to properly reflect
 	 * the free has happened.
 	 */
-	unsigned int must_insert_reserved:1;
-	unsigned int is_data:1;
-	unsigned int is_system:1;
-	unsigned int processing:1;
+	bool must_insert_reserved;
+	bool is_data;
+	bool is_system;
+	bool processing;
 };
 
 struct btrfs_delayed_tree_ref {
@@ -135,6 +149,19 @@ struct btrfs_delayed_tree_ref {
 	int level;
 };
 
+struct btrfs_delayed_data_ref {
+	struct btrfs_delayed_ref_node node;
+	u64 root;
+	u64 parent;
+	u64 objectid;
+	u64 offset;
+};
+
+enum btrfs_delayed_ref_flags {
+	/* Indicate that we are flushing delayed refs for the commit */
+	BTRFS_DELAYED_REFS_FLUSHING,
+};
+
 struct btrfs_delayed_ref_root {
 	/* head ref rbtree */
 	struct rb_root href_root;
@@ -142,22 +169,158 @@ struct btrfs_delayed_ref_root {
 	/* dirty extent records */
 	struct rb_root dirty_extent_root;
 
+	/* this spin lock protects the rbtree and the entries inside */
+	spinlock_t lock;
+
+	/* how many delayed ref updates we've queued, used by the
+	 * throttling code
+	 */
+	atomic_t num_entries;
+
 	/* total number of head nodes in tree */
 	unsigned long num_heads;
 
 	/* total number of head nodes ready for processing */
 	unsigned long num_heads_ready;
 
-	/*
-	 * set when the tree is flushing before a transaction commit,
-	 * used by the throttling code to decide if new updates need
-	 * to be run right away
-	 */
-	int flushing;
+	u64 pending_csums;
+
+	unsigned long flags;
 
 	u64 run_delayed_start;
+
+	/*
+	 * To make qgroup to skip given root.
+	 * This is for snapshot, as btrfs_qgroup_inherit() will manually
+	 * 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;
 };
 
+enum btrfs_ref_type {
+	BTRFS_REF_NOT_SET,
+	BTRFS_REF_DATA,
+	BTRFS_REF_METADATA,
+	BTRFS_REF_LAST,
+};
+
+struct btrfs_data_ref {
+	/* For EXTENT_DATA_REF */
+
+	/* Original root this data extent belongs to */
+	u64 owning_root;
+
+	/* Inode which refers to this data extent */
+	u64 ino;
+
+	/*
+	 * file_offset - extent_offset
+	 *
+	 * file_offset is the key.offset of the EXTENT_DATA key.
+	 * extent_offset is btrfs_file_extent_offset() of the EXTENT_DATA data.
+	 */
+	u64 offset;
+};
+
+struct btrfs_tree_ref {
+	/*
+	 * Level of this tree block
+	 *
+	 * Shared for skinny (TREE_BLOCK_REF) and normal tree ref.
+	 */
+	int level;
+
+	/*
+	 * Root which owns this tree block.
+	 *
+	 * For TREE_BLOCK_REF (skinny metadata, either inline or keyed)
+	 */
+	u64 owning_root;
+
+	/* For non-skinny metadata, no special member needed */
+};
+
+struct btrfs_ref {
+	enum btrfs_ref_type type;
+	int action;
+
+	/*
+	 * Whether this extent should go through qgroup record.
+	 *
+	 * Normally false, but for certain cases like delayed subtree scan,
+	 * setting this flag can hugely reduce qgroup overhead.
+	 */
+	bool skip_qgroup;
+
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+	/* Through which root is this modification. */
+	u64 real_root;
+#endif
+	u64 bytenr;
+	u64 len;
+
+	/* Bytenr of the parent tree block */
+	u64 parent;
+	union {
+		struct btrfs_data_ref data_ref;
+		struct btrfs_tree_ref tree_ref;
+	};
+};
+
+extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
+extern struct kmem_cache *btrfs_delayed_tree_ref_cachep;
+extern struct kmem_cache *btrfs_delayed_data_ref_cachep;
+extern struct kmem_cache *btrfs_delayed_extent_op_cachep;
+
+int __init btrfs_delayed_ref_init(void);
+void __cold btrfs_delayed_ref_exit(void);
+
+static inline void btrfs_init_generic_ref(struct btrfs_ref *generic_ref,
+				int action, u64 bytenr, u64 len, u64 parent)
+{
+	generic_ref->action = action;
+	generic_ref->bytenr = bytenr;
+	generic_ref->len = len;
+	generic_ref->parent = parent;
+}
+
+static inline void btrfs_init_tree_ref(struct btrfs_ref *generic_ref,
+				int level, u64 root, u64 mod_root, bool skip_qgroup)
+{
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+	/* If @real_root not set, use @root as fallback */
+	generic_ref->real_root = mod_root ?: root;
+#endif
+	generic_ref->tree_ref.level = level;
+	generic_ref->tree_ref.owning_root = root;
+	generic_ref->type = BTRFS_REF_METADATA;
+	if (skip_qgroup || !(is_fstree(root) &&
+			     (!mod_root || is_fstree(mod_root))))
+		generic_ref->skip_qgroup = true;
+	else
+		generic_ref->skip_qgroup = false;
+
+}
+
+static inline void btrfs_init_data_ref(struct btrfs_ref *generic_ref,
+				u64 ref_root, u64 ino, u64 offset, u64 mod_root,
+				bool skip_qgroup)
+{
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+	/* If @real_root not set, use @root as fallback */
+	generic_ref->real_root = mod_root ?: ref_root;
+#endif
+	generic_ref->data_ref.owning_root = ref_root;
+	generic_ref->data_ref.ino = ino;
+	generic_ref->data_ref.offset = offset;
+	generic_ref->type = BTRFS_REF_DATA;
+	if (skip_qgroup || !(is_fstree(ref_root) &&
+			     (!mod_root || is_fstree(mod_root))))
+		generic_ref->skip_qgroup = true;
+	else
+		generic_ref->skip_qgroup = false;
+}
 
 static inline struct btrfs_delayed_extent_op *
 btrfs_alloc_delayed_extent_op(void)
@@ -169,22 +332,22 @@ static inline void
 btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
 {
 	if (op)
-		kfree(op);
+		kmem_cache_free(btrfs_delayed_extent_op_cachep, op);
 }
 
 static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
 {
-	WARN_ON(ref->refs == 0);
-	if (--ref->refs == 0) {
+	WARN_ON(refcount_read(&ref->refs) == 0);
+	if (refcount_dec_and_test(&ref->refs)) {
 		WARN_ON(ref->in_tree);
 		switch (ref->type) {
 		case BTRFS_TREE_BLOCK_REF_KEY:
 		case BTRFS_SHARED_BLOCK_REF_KEY:
-			kfree(ref);
+			kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
 			break;
 		case BTRFS_EXTENT_DATA_REF_KEY:
 		case BTRFS_SHARED_DATA_REF_KEY:
-			kfree(ref);
+			kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
 			break;
 		default:
 			BUG();
@@ -192,10 +355,20 @@ static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
 	}
 }
 
+static inline u64 btrfs_ref_head_to_space_flags(
+				struct btrfs_delayed_ref_head *head_ref)
+{
+	if (head_ref->is_data)
+		return BTRFS_BLOCK_GROUP_DATA;
+	else if (head_ref->is_system)
+		return BTRFS_BLOCK_GROUP_SYSTEM;
+	return BTRFS_BLOCK_GROUP_METADATA;
+}
+
 static inline void btrfs_put_delayed_ref_head(struct btrfs_delayed_ref_head *head)
 {
-	if (--head->refs == 0)
-		kfree(head);
+	if (refcount_dec_and_test(&head->refs))
+		kmem_cache_free(btrfs_delayed_ref_head_cachep, head);
 }
 
 int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
@@ -204,13 +377,40 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
 			       u64 ref_root, int level, int action,
 			       struct btrfs_delayed_extent_op *extent_op,
 			       int *old_ref_mod, int *new_ref_mod);
+int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
+			       struct btrfs_ref *generic_ref,
+			       u64 reserved);
+int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
+				u64 bytenr, u64 num_bytes,
+				struct btrfs_delayed_extent_op *extent_op);
 void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
 			      struct btrfs_delayed_ref_root *delayed_refs,
 			      struct btrfs_delayed_ref_head *head);
 
+struct btrfs_delayed_ref_head *
+btrfs_find_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
+			    u64 bytenr);
+int btrfs_delayed_ref_lock(struct btrfs_delayed_ref_root *delayed_refs,
+			   struct btrfs_delayed_ref_head *head);
+static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
+{
+	mutex_unlock(&head->mutex);
+}
+void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
+			   struct btrfs_delayed_ref_head *head);
+
 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, u64 seq);
+
+void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr);
+void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans);
+void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
+				       struct btrfs_block_rsv *src,
+				       u64 num_bytes);
+bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info);
+
 /*
  * helper functions to cast a node into its container
  */
@@ -220,6 +420,12 @@ btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
 	return container_of(node, struct btrfs_delayed_tree_ref, node);
 }
 
+static inline struct btrfs_delayed_data_ref *
+btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
+{
+	return container_of(node, struct btrfs_delayed_data_ref, node);
+}
+
 int cleanup_ref_head(struct btrfs_trans_handle *trans,
 		     struct btrfs_fs_info *fs_info,
 		     struct btrfs_delayed_ref_head *head);
diff --git a/kernel-shared/extent-tree.c b/kernel-shared/extent-tree.c
index f447498a..988bceed 100644
--- a/kernel-shared/extent-tree.c
+++ b/kernel-shared/extent-tree.c
@@ -3790,7 +3790,7 @@ int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, unsigned long nr)
 	struct btrfs_delayed_ref_head *locked_ref = NULL;
 	struct btrfs_delayed_extent_op *extent_op;
 	int ret;
-	int must_insert_reserved = 0;
+	bool must_insert_reserved = false;
 
 	delayed_refs = &trans->delayed_refs;
 	while (1) {
@@ -3854,7 +3854,7 @@ int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, unsigned long nr)
 		 * lock.
 		 */
 		must_insert_reserved = locked_ref->must_insert_reserved;
-		locked_ref->must_insert_reserved = 0;
+		locked_ref->must_insert_reserved = false;
 
 		extent_op = locked_ref->extent_op;
 		locked_ref->extent_op = NULL;