On Wed, Jan 17, 2018 at 05:15:33PM +1100, Dave Chinner wrote: > IOWs, you're chasing a goal (100% reproducable filesystem images) > that simply cannot be acheived via writing files through a > kernel-based filesystem.... That said, we do have a mechanism for populating XFS filesystems from userspace in a manner that we may be able to make deterministic enough for reproducable image file creation: the mkfs.xfs protofile infrastructure. That runs from mkfs in userspace, and creates the directory structure and files specified in the protofile. There's nothing that runs concurrently with this, it will always run the creation operations in the same order, and I think we could extend it to specify a global timestamp for all inodes and solve that problem too. The protofile infrastructure uses the kernel allocation code which we already know is deterministic (i.e. gives the same allocation results for the same operations if the initial state is the same) and so we can probably get very close to 100% reproducable filesystem image through this mechanism. It's need some work and extensions to provide everything that is needed in a reliable manner, and a bunch of regression tests added to fstests to make sure it works and keeps working. If you want to stick with XFS as the base filesystem for your images, this may be the best way to proceed.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
