--- zzzz-none-000/linux-3.10.107/fs/nilfs2/btree.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/fs/nilfs2/btree.c	2021-02-04 17:41:59.000000000 +0000
@@ -633,6 +633,44 @@
 	return 0;
 }
 
+/**
+ * nilfs_btree_get_next_key - get next valid key from btree path array
+ * @btree: bmap struct of btree
+ * @path: array of nilfs_btree_path struct
+ * @minlevel: start level
+ * @nextkey: place to store the next valid key
+ *
+ * Return Value: If a next key was found, 0 is returned. Otherwise,
+ * -ENOENT is returned.
+ */
+static int nilfs_btree_get_next_key(const struct nilfs_bmap *btree,
+				    const struct nilfs_btree_path *path,
+				    int minlevel, __u64 *nextkey)
+{
+	struct nilfs_btree_node *node;
+	int maxlevel = nilfs_btree_height(btree) - 1;
+	int index, next_adj, level;
+
+	/* Next index is already set to bp_index for leaf nodes. */
+	next_adj = 0;
+	for (level = minlevel; level <= maxlevel; level++) {
+		if (level == maxlevel)
+			node = nilfs_btree_get_root(btree);
+		else
+			node = nilfs_btree_get_nonroot_node(path, level);
+
+		index = path[level].bp_index + next_adj;
+		if (index < nilfs_btree_node_get_nchildren(node)) {
+			/* Next key is in this node */
+			*nextkey = nilfs_btree_node_get_key(node, index);
+			return 0;
+		}
+		/* For non-leaf nodes, next index is stored at bp_index + 1. */
+		next_adj = 1;
+	}
+	return -ENOENT;
+}
+
 static int nilfs_btree_lookup(const struct nilfs_bmap *btree,
 			      __u64 key, int level, __u64 *ptrp)
 {
@@ -881,8 +919,6 @@
 			      int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *right;
-	__u64 newkey;
-	__u64 newptr;
 	int nchildren, n, move, ncblk;
 
 	node = nilfs_btree_get_nonroot_node(path, level);
@@ -904,9 +940,6 @@
 	if (!buffer_dirty(path[level].bp_sib_bh))
 		mark_buffer_dirty(path[level].bp_sib_bh);
 
-	newkey = nilfs_btree_node_get_key(right, 0);
-	newptr = path[level].bp_newreq.bpr_ptr;
-
 	if (move) {
 		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
 		nilfs_btree_node_insert(right, path[level].bp_index,
@@ -1563,6 +1596,27 @@
 	return ret;
 }
 
+static int nilfs_btree_seek_key(const struct nilfs_bmap *btree, __u64 start,
+				__u64 *keyp)
+{
+	struct nilfs_btree_path *path;
+	const int minlevel = NILFS_BTREE_LEVEL_NODE_MIN;
+	int ret;
+
+	path = nilfs_btree_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, start, NULL, minlevel, 0);
+	if (!ret)
+		*keyp = start;
+	else if (ret == -ENOENT)
+		ret = nilfs_btree_get_next_key(btree, path, minlevel, keyp);
+
+	nilfs_btree_free_path(path);
+	return ret;
+}
+
 static int nilfs_btree_last_key(const struct nilfs_bmap *btree, __u64 *keyp)
 {
 	struct nilfs_btree_path *path;
@@ -1797,7 +1851,7 @@
 				   __u64 key, __u64 ptr,
 				   const __u64 *keys, const __u64 *ptrs, int n)
 {
-	struct buffer_head *bh;
+	struct buffer_head *bh = NULL;
 	union nilfs_bmap_ptr_req dreq, nreq, *di, *ni;
 	struct nilfs_bmap_stats stats;
 	int ret;
@@ -2298,7 +2352,9 @@
 	.bop_assign		=	nilfs_btree_assign,
 	.bop_mark		=	nilfs_btree_mark,
 
+	.bop_seek_key		=	nilfs_btree_seek_key,
 	.bop_last_key		=	nilfs_btree_last_key,
+
 	.bop_check_insert	=	NULL,
 	.bop_check_delete	=	nilfs_btree_check_delete,
 	.bop_gather_data	=	nilfs_btree_gather_data,
@@ -2318,7 +2374,9 @@
 	.bop_assign		=	nilfs_btree_assign_gc,
 	.bop_mark		=	NULL,
 
+	.bop_seek_key		=	NULL,
 	.bop_last_key		=	NULL,
+
 	.bop_check_insert	=	NULL,
 	.bop_check_delete	=	NULL,
 	.bop_gather_data	=	NULL,