On Thu, 2024-08-22 at 21:12 -0700, Christoph Hellwig wrote: > On Thu, Aug 22, 2024 at 05:01:22PM -0700, Darrick J. Wong wrote: > > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > > > This patch introduces two more new ioctls to manage atomic updates to > > file contents -- XFS_IOC_START_COMMIT and XFS_IOC_COMMIT_RANGE. The > > commit mechanism here is exactly the same as what XFS_IOC_EXCHANGE_RANGE > > does, but with the additional requirement that file2 cannot have changed > > since some sampling point. The start-commit ioctl performs the sampling > > of file attributes. > > The code itself looks simply enough now, but how do we guarantee > that ctime actually works as a full change count and not just by > chance here? > With current mainline kernels it won't, but the updated multigrain timestamp series is in linux-next and is slated to go into v6.12. At that point it should be fine for this purpose. -- Jeff Layton <jlayton@xxxxxxxxxx>
