Since btrfs does not do recursive atomic snapshots (which I am ok with), I am doing this myself. A handful of suggestions/problems came up. 1. Maybe btrfsprogs could gain an option to do recursive non-atomic snapshots at the userspace level, simply invoking low-level atomic snapshots one by one? For the following, the kernel is 3.4.4 with the too-overloaded "0.19" version of btrfsprogs. 2. Subvolume directories are somewhat special, as you may know. Only `btrfs sub create/snap` creates them, and they cannot be rmdird. # btrfs sub list . ID 256 top level 5 path HEAD [...] ID 450 top level 5 path HEAD/woven ID 451 top level 5 path HEAD/leet Attempting to snapshot a directory with further subvolumes in it has the strange effect that directories get created, and do so with the wrong inode info: # ls -l HEAD total 4 drwxr-xr-x 1 root root 18 Aug 18 01:04 . dr-xr-xr-x 1 root root 218 Aug 23 00:25 .. drwxr-xr-x 1 root root 66 Aug 17 23:04 leet drwxrwx--- 1 root root 100 Aug 18 00:53 woven # btrfs sub snap HEAD today Create a snapshot of 'HEAD' in './today' # ls -l today total 4 drwxr-xr-x 1 root root 18 Aug 18 01:04 . dr-xr-xr-x 1 root root 228 Aug 23 00:25 .. drwxr-xr-x 1 root root 0 Aug 23 00:25 leet drwxr-xr-x 1 root root 0 Aug 23 00:25 woven 3. The creation of these non-special directories in today/ is undesired, because now I need to rmdir them first before creating the subsnapshots. # btrfs sub snap HEAD today Create a snapshot of 'HEAD' in './today' # btrfs sub snap HEAD/leet today/ Create a snapshot of 'HEAD/leet' in 'today//leet' ERROR: cannot snapshot 'HEAD/leet' - File exists 4. Because today/leet already exists as a non-subvolume root, btrfsprogs defaults to creating another directory inside it (unexpected, but ok). However, while doing so, it runs into some unexplainable ENOTTY: # btrfs sub snap HEAD today Create a snapshot of 'HEAD' in './today' # btrfs sub snap HEAD/leet today/leet Create a snapshot of 'HEAD/leet' in 'today/leet/leet' ERROR: cannot snapshot 'HEAD/leet' - Inappropriate ioctl for device (^failure where success would have been expected) Successes: # rmdir today/leet/ # mkdir today/leet # btrfs sub snap HEAD/leet today/leet Create a snapshot of 'HEAD/leet' in 'today/leet/leet' So today/leet as created by `sub snap HEAD` is also some weird object. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
