Here is the userspace tooling support for utilising the new metadata_uuid field, enabling the change of fsid without having to rewrite every metadata block. This patchset consists of adding support for the new field to various tools and files (Patch 1). The actual implementation of the new -m|-M options (which are described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) which exercises the new options and verifies certain invariants hold (these are also described in Patch2). Patch 4 is more or less copy of the kernel conuterpart just reducing some duplication between btrfs_fs_info and btrfs_fs_devices structures.
The intended usecase of this feature is to give the sysadmin the ability to create copies of filesystesm, change their uuid quickly and mount them alongside the original filesystem for, say, forensic purposes. One thing which still hasn't been set in stone is whether the new options will remain as -m|-M or whether they should subsume the current -u|-U - from the point of view of users nothing should change. So this is something which I'd like to hear from the community. Of course the alternative of rewriting the metadata blocks will be assigne new options - perhaps -m|M ? I've tested this with multiple xfstest runs with the new tools installed as well as running btrfs-progs test and have observed no regressions. Nikolay Borisov (4): btrfs-progs: Add support for metadata_uuid field. btrfstune: Add support for changing the user uuid btrfs-progs: tests: Add tests for changing fsid feature btrfs-progs: Remove fsid/metdata_uuid fields from fs_info btrfstune.c | 174 ++++++++++++++++++++++++----- check/main.c | 2 +- chunk-recover.c | 17 ++- cmds-filesystem.c | 2 + cmds-inspect-dump-super.c | 22 +++- convert/common.c | 2 + ctree.c | 15 +-- ctree.h | 8 +- disk-io.c | 62 ++++++++-- image/main.c | 25 +++-- tests/misc-tests/033-metadata-uuid/test.sh | 137 +++++++++++++++++++++++ volumes.c | 37 ++++-- volumes.h | 1 + 13 files changed, 431 insertions(+), 73 deletions(-) create mode 100755 tests/misc-tests/033-metadata-uuid/test.sh -- 2.7.4
