btrfs-progs: check: introduce repair_extent_data_item()

The only thing repair_extent_data_item() does is that it adds backref of the
tree_block. Just like what original mode does:

It first searches the corresponding extent item.

1. If the extent item exists but backref is missing, add one backref to the
   extent.
2. Found nothing, just add an extent item and add one backref.

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/cmds-check.c b/cmds-check.c
index 595b663a..3e709b84 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -11767,6 +11767,120 @@ out:
 }
 
 /*
+ * If @err contains BACKREF_MISSING then add extent of the
+ * file_extent_data_item.
+ *
+ * Returns error bits after reapir.
+ */
+static int repair_extent_data_item(struct btrfs_trans_handle *trans,
+				   struct btrfs_root *root,
+				   struct btrfs_path *pathp,
+				   struct node_refs *nrefs,
+				   int err)
+{
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_key fi_key;
+	struct btrfs_key key;
+	struct btrfs_extent_item *ei;
+	struct btrfs_path path;
+	struct btrfs_root *extent_root = root->fs_info->extent_root;
+	struct extent_buffer *eb;
+	u64 size;
+	u64 disk_bytenr;
+	u64 num_bytes;
+	u64 parent;
+	u64 offset;
+	u64 extent_offset;
+	u64 file_offset;
+	int generation;
+	int slot;
+	int ret = 0;
+
+	eb = pathp->nodes[0];
+	slot = pathp->slots[0];
+	btrfs_item_key_to_cpu(eb, &fi_key, slot);
+	fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+
+	if (btrfs_file_extent_type(eb, fi) == BTRFS_FILE_EXTENT_INLINE ||
+	    btrfs_file_extent_disk_bytenr(eb, fi) == 0)
+		return err;
+
+	file_offset = fi_key.offset;
+	generation = btrfs_file_extent_generation(eb, fi);
+	disk_bytenr = btrfs_file_extent_disk_bytenr(eb, fi);
+	num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
+	extent_offset = btrfs_file_extent_offset(eb, fi);
+	offset = file_offset - extent_offset;
+
+	/* now repair only adds backref */
+	if ((err & BACKREF_MISSING) == 0)
+		return err;
+
+	/* search extent item */
+	key.objectid = disk_bytenr;
+	key.type = BTRFS_EXTENT_ITEM_KEY;
+	key.offset = num_bytes;
+
+	btrfs_init_path(&path);
+	ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
+	if (ret < 0) {
+		ret = -EIO;
+		goto out;
+	}
+
+	/* insert an extent item */
+	if (ret > 0) {
+		key.objectid = disk_bytenr;
+		key.type = BTRFS_EXTENT_ITEM_KEY;
+		key.offset = num_bytes;
+		size = sizeof(*ei);
+
+		btrfs_release_path(&path);
+		ret = btrfs_insert_empty_item(trans, extent_root, &path, &key,
+					      size);
+		if (ret)
+			goto out;
+		eb = path.nodes[0];
+		ei = btrfs_item_ptr(eb, path.slots[0], struct btrfs_extent_item);
+
+		btrfs_set_extent_refs(eb, ei, 0);
+		btrfs_set_extent_generation(eb, ei, generation);
+		btrfs_set_extent_flags(eb, ei, BTRFS_EXTENT_FLAG_DATA);
+
+		btrfs_mark_buffer_dirty(eb);
+		ret = btrfs_update_block_group(trans, extent_root, disk_bytenr,
+					       num_bytes, 1, 0);
+		btrfs_release_path(&path);
+	}
+
+	if (nrefs->full_backref[0])
+		parent = btrfs_header_bytenr(eb);
+	else
+		parent = 0;
+
+	ret = btrfs_inc_extent_ref(trans, root, disk_bytenr, num_bytes, parent,
+				   root->objectid,
+		   parent ? BTRFS_FIRST_FREE_OBJECTID : fi_key.objectid,
+				   offset);
+	if (ret) {
+		error(
+		"failed to increase extent data backref[%llu %llu] root %llu",
+		      disk_bytenr, num_bytes, root->objectid);
+		goto out;
+	} else {
+		printf("Add one extent data backref [%llu %llu]\n",
+		       disk_bytenr, num_bytes);
+	}
+
+	err &= ~BACKREF_MISSING;
+out:
+	if (ret)
+		error("can't repair root %llu extent data item[%llu %llu]",
+		      root->objectid, disk_bytenr, num_bytes);
+	return err;
+}
+
+/*
  * Check EXTENT_DATA item, mainly for its dbackref in extent tree
  *
  * Return >0 any error found and output error message
@@ -13003,6 +13117,9 @@ again:
 	switch (type) {
 	case BTRFS_EXTENT_DATA_KEY:
 		ret = check_extent_data_item(root, path, nrefs, account_bytes);
+		if (repair && ret)
+			ret = repair_extent_data_item(trans, root, path, nrefs,
+						      ret);
 		err |= ret;
 		break;
 	case BTRFS_BLOCK_GROUP_ITEM_KEY: