Hello,
This series add support for the renameat2 system call RENAME_EXCHANGE flag (which allows to atomically replace two paths) to the vfat filesystem code.
There are many use cases for this, but we are particularly interested in making possible for vfat filesystems to be part of OSTree [0] deployments.
Currently OSTree relies on symbolic links to make the deployment updates an atomic transactional operation. But RENAME_EXCHANGE could be used [1] to achieve a similar level of robustness when using a vfat filesystem.
Patch #1 is just a preparatory patch to introduce the RENAME_EXCHANGE support in patch #2 and finally patch #3 adds some kselftests to test it.
This is my first contribution to the fs/* subsystem, so I'm marking this set as RFC, in case I got anything wrong with the patches. But they work correctly on my local testing.
[0]: https://github.com/ostreedev/ostree [1]: https://github.com/ostreedev/ostree/issues/1649
Javier Martinez Canillas (3): fat: add a vfat_rename2() and make existing .rename callback a helper fat: add renameat2 RENAME_EXCHANGE flag support selftests/filesystems: add a vfat RENAME_EXCHANGE test
MAINTAINERS | 1 + fs/fat/namei_vfat.c | 172 +++++++++++++++++- tools/testing/selftests/Makefile | 1 + .../selftests/filesystems/fat/Makefile | 7 + .../testing/selftests/filesystems/fat/config | 2 + .../filesystems/fat/rename_exchange.c | 37 ++++ .../filesystems/fat/run_fat_tests.sh | 80 ++++++++ 7 files changed, 293 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/filesystems/fat/Makefile create mode 100644 tools/testing/selftests/filesystems/fat/config create mode 100644 tools/testing/selftests/filesystems/fat/rename_exchange.c create mode 100755 tools/testing/selftests/filesystems/fat/run_fat_tests.sh