Port extent buffer to btrfs-progs

This patch ports extent buffer to btrfs-progs. extent_map.c contains a
simplified extent map tree and functions that manipulate/manage extent
buffer. extent state related codes are based on corresponding codes in
kernel module, codes that manage extent buffer are from disk-io.c.

1 files changed, 9 insertions, 0 deletions

diff --git a/extent-cache.c b/extent-cache.c
index cfc6b639..4e6d1b29 100644
--- a/extent-cache.c
+++ b/extent-cache.c
@@ -143,6 +143,15 @@ struct cache_extent *find_first_cache_extent(struct cache_tree *tree,
 	return entry;
 }
 
+struct cache_extent *prev_cache_extent(struct cache_extent *pe)
+{
+	struct rb_node *node = rb_prev(&pe->rb_node);
+
+	if (!node)
+		return NULL;
+	return rb_entry(node, struct cache_extent, rb_node);
+}
+
 struct cache_extent *next_cache_extent(struct cache_extent *pe)
 {
 	struct rb_node *node = rb_next(&pe->rb_node);