On Thu, Oct 23, 2025 at 06:45:33PM +0200, Arsen Arsenović wrote: > "Richard W.M. Jones" <[email protected]> writes: > > > I was definitely expecting this one to fail with ENOTSUP or similar. > > That's with the file copy-allocated-destination-zero-synch.out on ZFS? > > Yes - my home directory is on ZoL, and so is ~/tmp.
It appears this is a limitation of OpenZFS: https://github.com/openzfs/zfs/blob/fc519b2c1108b52aaad63e356645f63c2c167f82/module/os/linux/zfs/zpl_file.c#L665 <quote> * The original mode=0 (allocate space) behavior can be reasonably emulated * by checking if enough space exists and creating a sparse file, as real * persistent space reservation is not possible due to COW, snapshots, etc. </quote> Looking at the code when mode == 0, I believe we hit the second case (line 707), which seems to sparsify the file and (if that succeeeds) returns no error :-( We should probably add a 'requires' to the test. I think it could still be a bug in libnbd that we don't fail if fallocate fails, but it wouldn't have helped here. Thanks, Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW _______________________________________________ Libguestfs mailing list -- [email protected] To unsubscribe send an email to [email protected]
