Hi all, This series creates XFS_IOC_START_COMMIT and XFS_IOC_COMMIT_RANGE ioctls to perform the exchange only if the target file has not been changed since a given sampling point. This new functionality uses the mechanism underlying EXCHANGE_RANGE to stage and commit file updates such that reader programs will see either the old contents or the new contents in their entirety, with no chance of torn writes. A successful call completion guarantees that the new contents will be seen even if the system fails. The pair of ioctls allows userspace to perform what amounts to a compare and exchange operation on entire file contents. Note that there are ongoing arguments in the community about how best to implement some sort of file data write counter that nfsd could also use to signal invalidations to clients. Until such a thing is implemented, this patch will rely on ctime/mtime updates. If you're going to start using this code, I strongly recommend pulling from my git trees, which are linked below. This has been running on the djcloud for months with no problems. Enjoy! Comments and questions are, as always, welcome. --D kernel git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=atomic-file-commits xfsprogs git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=atomic-file-commits fstests git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=atomic-file-commits --- Commits in this patchset: * src/fiexchange.h: add the start-commit/commit-range ioctls * xfs/122: add tests for commitrange structures --- m4/package_xfslibs.m4 | 2 ++ src/fiexchange.h | 26 ++++++++++++++++++++++++++ src/global.h | 4 ++++ tests/xfs/122.out | 1 + 4 files changed, 33 insertions(+)
