btrfs-progs: extent-tree: Introduce function to find the first overlapping extent

Introduce a new function, btrfs_search_overlap_extent() to find the first
overlapping extent.

It's useful for later btrfs-convert rework.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/extent-tree.c b/extent-tree.c
index 4a41717e..6ccd4245 100644
--- a/extent-tree.c
+++ b/extent-tree.c
@@ -3909,6 +3909,69 @@ int btrfs_fix_block_accounting(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
+static void __get_extent_size(struct btrfs_root *root, struct btrfs_path *path,
+			      u64 *start, u64 *len)
+{
+	struct btrfs_key key;
+
+	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+	BUG_ON(!(key.type == BTRFS_EXTENT_ITEM_KEY ||
+		 key.type == BTRFS_METADATA_ITEM_KEY));
+	*start = key.objectid;
+	if (key.type == BTRFS_EXTENT_ITEM_KEY)
+		*len = key.offset;
+	else
+		*len = root->nodesize;
+}
+
+/*
+ * Find first overlap extent for range [bytenr, bytenr + len)
+ * Return 0 for found and point path to it.
+ * Return >0 for not found.
+ * Return <0 for err
+ */
+int btrfs_search_overlap_extent(struct btrfs_root *root,
+				struct btrfs_path *path, u64 bytenr, u64 len)
+{
+	struct btrfs_key key;
+	u64 cur_start;
+	u64 cur_len;
+	int ret;
+
+	key.objectid = bytenr;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = (u64)-1;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		return ret;
+	BUG_ON(ret == 0);
+
+	ret = btrfs_previous_extent_item(root, path, 0);
+	if (ret < 0)
+		return ret;
+	/* no previous, check next extent */
+	if (ret > 0)
+		goto next;
+	__get_extent_size(root, path, &cur_start, &cur_len);
+	/* Tail overlap */
+	if (cur_start + cur_len > bytenr)
+		return 1;
+
+next:
+	ret = btrfs_next_extent_item(root, path, bytenr + len);
+	if (ret < 0)
+		return ret;
+	/* No next, prev already checked, no overlap */
+	if (ret > 0)
+		return 0;
+	__get_extent_size(root, path, &cur_start, &cur_len);
+	/* head overlap*/
+	if (cur_start < bytenr + len)
+		return 1;
+	return 0;
+}
+
 /*
  * Record a file extent. Do all the required works, such as inserting
  * file extent item, inserting extent item and backref item into extent