diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 429c73c374b8..63708f77c8e0 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -94,6 +94,7 @@ struct backref_edge {
 
 #define LOWER	0
 #define UPPER	1
+#define RELOCATION_RESERVED_NODES	256
 
 struct backref_cache {
 	/* red black tree of all backref nodes in the cache */
@@ -176,6 +177,8 @@ struct reloc_control {
 	u64 merging_rsv_size;
 	/* size of relocated tree nodes */
 	u64 nodes_relocated;
+	/* reserved size for block group relocation*/
+	u64 reserved_bytes;
 
 	u64 search_start;
 	u64 extents_found;
@@ -184,7 +187,6 @@ struct reloc_control {
 	unsigned int create_reloc_tree:1;
 	unsigned int merge_reloc_tree:1;
 	unsigned int found_file_extent:1;
-	unsigned int commit_transaction:1;
 };
 
 /* stages of data relocation */
@@ -2590,28 +2592,36 @@ static int reserve_metadata_space(struct btrfs_trans_handle *trans,
 	struct btrfs_root *root = rc->extent_root;
 	u64 num_bytes;
 	int ret;
+	u64 tmp;
 
 	num_bytes = calcu_metadata_size(rc, node, 1) * 2;
 
 	trans->block_rsv = rc->block_rsv;
-	ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
-				  BTRFS_RESERVE_FLUSH_ALL);
+	rc->reserved_bytes += num_bytes;
+	ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
+				BTRFS_RESERVE_FLUSH_ALL);
 	if (ret) {
-		if (ret == -EAGAIN)
-			rc->commit_transaction = 1;
+		if (ret == -EAGAIN) {
+			tmp = rc->extent_root->nodesize *
+				RELOCATION_RESERVED_NODES;
+			while (tmp <= rc->reserved_bytes)
+				tmp <<= 1;
+			/*
+			 * only one thread can access block_rsv at this point,
+			 * so we don't need hold lock to protect block_rsv.
+			 * we expand more reservation size here to allow enough
+			 * space for relocation and we will return eailer in
+			 * enospc case.
+			 */
+			rc->block_rsv->size = tmp + rc->extent_root->nodesize *
+					      RELOCATION_RESERVED_NODES;
+		}
 		return ret;
 	}
 
 	return 0;
 }
 
-static void release_metadata_space(struct reloc_control *rc,
-				   struct backref_node *node)
-{
-	u64 num_bytes = calcu_metadata_size(rc, node, 0) * 2;
-	btrfs_block_rsv_release(rc->extent_root, rc->block_rsv, num_bytes);
-}
-
 /*
  * relocate a block tree, and then update pointers in upper level
  * blocks that reference the block to point to the new location.
@@ -2898,7 +2908,6 @@ static int relocate_tree_block(struct btrfs_trans_handle *trans,
 				struct btrfs_path *path)
 {
 	struct btrfs_root *root;
-	int release = 0;
 	int ret = 0;
 
 	if (!node)
@@ -2915,7 +2924,6 @@ static int relocate_tree_block(struct btrfs_trans_handle *trans,
 		ret = reserve_metadata_space(trans, rc, node);
 		if (ret)
 			goto out;
-		release = 1;
 	}
 
 	if (root) {
@@ -2940,11 +2948,8 @@ static int relocate_tree_block(struct btrfs_trans_handle *trans,
 		ret = do_relocation(trans, rc, node, key, path, 1);
 	}
 out:
-	if (ret || node->level == 0 || node->cowonly) {
-		if (release)
-			release_metadata_space(rc, node);
+	if (ret || node->level == 0 || node->cowonly)
 		remove_backref_node(&rc->backref_cache, node);
-	}
 	return ret;
 }
 
@@ -3867,29 +3872,20 @@ static noinline_for_stack
 int prepare_to_relocate(struct reloc_control *rc)
 {
 	struct btrfs_trans_handle *trans;
-	int ret;
 
 	rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root,
 					      BTRFS_BLOCK_RSV_TEMP);
 	if (!rc->block_rsv)
 		return -ENOMEM;
 
-	/*
-	 * reserve some space for creating reloc trees.
-	 * btrfs_init_reloc_root will use them when there
-	 * is no reservation in transaction handle.
-	 */
-	ret = btrfs_block_rsv_add(rc->extent_root, rc->block_rsv,
-				  rc->extent_root->nodesize * 256,
-				  BTRFS_RESERVE_FLUSH_ALL);
-	if (ret)
-		return ret;
-
 	memset(&rc->cluster, 0, sizeof(rc->cluster));
 	rc->search_start = rc->block_group->key.objectid;
 	rc->extents_found = 0;
 	rc->nodes_relocated = 0;
 	rc->merging_rsv_size = 0;
+	rc->reserved_bytes = 0;
+	rc->block_rsv->size = rc->extent_root->nodesize *
+			      RELOCATION_RESERVED_NODES;
 
 	rc->create_reloc_tree = 1;
 	set_reloc_control(rc);
@@ -3933,6 +3929,14 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
 	}
 
 	while (1) {
+		rc->reserved_bytes = 0;
+		ret = btrfs_block_rsv_refill(rc->extent_root,
+					rc->block_rsv, rc->block_rsv->size,
+					BTRFS_RESERVE_FLUSH_ALL);
+		if (ret) {
+			err = ret;
+			break;
+		}
 		progress++;
 		trans = btrfs_start_transaction(rc->extent_root, 0);
 		if (IS_ERR(trans)) {
@@ -4020,14 +4024,8 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
 			}
 		}
 
-		if (rc->commit_transaction) {
-			rc->commit_transaction = 0;
-			ret = btrfs_commit_transaction(trans, rc->extent_root);
-			BUG_ON(ret);
-		} else {
-			btrfs_end_transaction_throttle(trans, rc->extent_root);
-			btrfs_btree_balance_dirty(rc->extent_root);
-		}
+		btrfs_end_transaction_throttle(trans, rc->extent_root);
+		btrfs_btree_balance_dirty(rc->extent_root);
 		trans = NULL;
 
 		if (rc->stage == MOVE_DATA_EXTENTS &&