btrfs-progs: Pull free space tree related code from kernel

To help implement free space tree checker in user space some kernel
function are necessary, namely iterating/deleting/adding freespace
items, some internal search functions. Functions to populate a block
group based on the extent tree. The code is largely copy/paste from
the kernel with locking eliminated (i.e free_space_lock). It supports
reading/writing of both bitmap and extent based FST trees.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 74 insertions, 0 deletions

diff --git a/ctree.c b/ctree.c
index d8a6883a..1afb94f0 100644
--- a/ctree.c
+++ b/ctree.c
@@ -1226,6 +1226,80 @@ again:
 }
 
 /*
+ * Helper to use instead of search slot if no exact match is needed but
+ * instead the next or previous item should be returned.
+ * When find_higher is true, the next higher item is returned, the next lower
+ * otherwise.
+ * When return_any and find_higher are both true, and no higher item is found,
+ * return the next lower instead.
+ * When return_any is true and find_higher is false, and no lower item is found,
+ * return the next higher instead.
+ * It returns 0 if any item is found, 1 if none is found (tree empty), and
+ * < 0 on error
+ */
+int btrfs_search_slot_for_read(struct btrfs_root *root,
+                               const struct btrfs_key *key,
+                               struct btrfs_path *p, int find_higher,
+                               int return_any)
+{
+        int ret;
+        struct extent_buffer *leaf;
+
+again:
+        ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
+        if (ret <= 0)
+                return ret;
+        /*
+	 * A return value of 1 means the path is at the position where the item
+	 * should be inserted. Normally this is the next bigger item, but in
+	 * case the previous item is the last in a leaf, path points to the
+	 * first free slot in the previous leaf, i.e. at an invalid item.
+         */
+        leaf = p->nodes[0];
+
+        if (find_higher) {
+                if (p->slots[0] >= btrfs_header_nritems(leaf)) {
+                        ret = btrfs_next_leaf(root, p);
+                        if (ret <= 0)
+                                return ret;
+                        if (!return_any)
+                                return 1;
+                        /*
+			 * No higher item found, return the next lower instead
+                         */
+                        return_any = 0;
+                        find_higher = 0;
+                        btrfs_release_path(p);
+                        goto again;
+                }
+        } else {
+                if (p->slots[0] == 0) {
+                        ret = btrfs_prev_leaf(root, p);
+                        if (ret < 0)
+                                return ret;
+                        if (!ret) {
+                                leaf = p->nodes[0];
+                                if (p->slots[0] == btrfs_header_nritems(leaf))
+                                        p->slots[0]--;
+                                return 0;
+                        }
+                        if (!return_any)
+                                return 1;
+                        /*
+			 * No lower item found, return the next higher instead
+                         */
+                        return_any = 0;
+                        find_higher = 1;
+                        btrfs_release_path(p);
+                        goto again;
+                } else {
+                        --p->slots[0];
+                }
+        }
+        return 0;
+}
+
+/*
  * adjust the pointers going up the tree, starting at level
  * making sure the right key of each node is points to 'key'.
  * This is used after shifting pointers to the left, so it stops