New utility(btrfsrevert) added to swap subvolumes. With this utility, a subvolume (Source Subvolume) takes place of another subvolume (Target Subvolume), and target subvolume goes under hidden directory(".old_trees") in filesystem root(fs tree, tree id=5), and its name is expanded with random UUID.
This utility cannot operate mounted filesystem. This is only for unmounted device. And this utility also cannot operate filesystem root. For now, if we want to swap filesystem root, we can use btrfsctl with Josef Bacik's patch. I wonder which is better, integrating 'root swap' ioctl or not supporting 'root swap' as for this utility... A patch follows this mail. man-page-like description and examples are as follows. NAME btrfsrevert - swap subvolumes. SYNOPSIS btrfsrevert -s source_subvolume -t target_subvolume device OPTIONS -s source subvolume Specify subvolume number which replace target subvolume. -t target subvolume Specify subvolume number which is replaced by source subvolume. device Specify target device which is not mounted. SAMPLES Consider two subvolumes 'target'(id=256) and 'source'(id=300) exist in filesystem root. / + +- 'target' (id=256) +- 'source' (id=300) In this case, following command swaps subvolume, # btrfsrevert -s 300 -t 256 /dev/hda1 like this. / + +- 'target' (id=300) | +- '.old_tree' +- 'target_[random uuid]' (id=256) A subvolume(id:256) is replaced with a subvolume(id:300), and replaced subvolume(id:256) goes to .old_trees directory. Regards, taruisi -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html