[v3,06/10] btrfs-progs: undelete-subvol: introduce link_subvol_to_lostfound

Commit Message

Lu Fengqi May 7, 2018, 3:10 a.m. UTC

The function will create lost+found directory, link the deleted
subvolume specified by the subvol_id to the directory, update the
information of root_item and cleanup the associated orphan item.

Signed-off-by: Lu Fengqi <[e-mail]>
Reviewed-by: Qu Wenruo <[e-mail]>
---
V3:
pass btrfs_fs_info instead of btrfs_root;
add Reviewed-by from Qu Wenruo.

 undelete-subvol.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

Patch

diff --git a/undelete-subvol.c b/undelete-subvol.c
index 6d3ef19977d6..9851998ec3df 100644
--- a/undelete-subvol.c
+++ b/undelete-subvol.c
@@ -79,3 +79,79 @@  out:
 	btrfs_release_path(&path);
 	return ret;
 }
+
+/*
+ * Recover a subvolume specified by subvol_id, and link it to the lost+found
+ * directory.
+ *
+ * @subvol_id: specify the subvolume which will be linked, and also be the part
+ * of the subvolume name.
+ *
+ * Return 0 if no error occurred.
+ */
+static int link_subvol_to_lostfound(struct btrfs_fs_info *fs_info,
+				    u64 subvol_id)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_root *fs_root = fs_info->fs_root;
+	char buf[BTRFS_NAME_LEN + 1] = {0}; /* 1 for snprintf null */
+	char *dir_name = "lost+found";
+	u64 lost_found_ino = 0;
+	u32 mode = 0700;
+	int ret;
+
+	/*
+	 * For link subvolume to lost+found,
+	 * 2 for parent(256)'s dir_index and dir_item
+	 * 2 for lost+found dir's inode_item and inode_ref
+	 * 2 for lost+found dir's dir_index and dir_item for the subvolume
+	 * 2 for the subvolume's root_ref and root_backref
+	 */
+	trans = btrfs_start_transaction(fs_root, 8);
+	if (IS_ERR(trans)) {
+		error("unable to start transaction");
+		ret = PTR_ERR(trans);
+		goto out;
+	}
+
+	/* Create lost+found directory */
+	ret = btrfs_mkdir(trans, fs_root, dir_name, strlen(dir_name),
+			  BTRFS_FIRST_FREE_OBJECTID, &lost_found_ino,
+			  mode);
+	if (ret < 0) {
+		error("failed to create '%s' dir: %d", dir_name, ret);
+		goto out;
+	}
+
+	/* Link the subvolume to lost+found directory */
+	snprintf(buf, BTRFS_NAME_LEN + 1, "sub%llu", subvol_id);
+	ret = btrfs_link_subvol(trans, fs_root, buf, subvol_id, lost_found_ino,
+				false);
+	if (ret) {
+		error("failed to link the subvol %llu: %d", subvol_id, ret);
+		goto out;
+	}
+
+	/* Clear root flags BTRFS_ROOT_SUBVOL_DEAD */
+	ret = recover_dead_root(trans, subvol_id);
+	if (ret)
+		goto out;
+
+	/* Delete the orphan item after undeletion is completed. */
+	ret = btrfs_del_orphan_item(trans, root, subvol_id);
+	if (ret) {
+		error("failed to delete the orphan_item for %llu: %d",
+				subvol_id, ret);
+		goto out;
+	}
+
+	ret = btrfs_commit_transaction(trans, fs_root);
+	if (ret) {
+		error("transaction commit failed: %d", ret);
+		goto out;
+	}
+
+out:
+	return ret;
+}