Re: strange zfs size allocation data

[Greg Troxel <gdt%lexort.com@localhost>]

Martin Husemann <martin%duskware.de@localhost> writes:

> On Sun, Jul 07, 2024 at 11:32:54PM -0400, Mouse wrote:
>> Is bup zfs-specific?  Because, if you're not doing something
>> filesystem-specific, I actually think you will have trouble even
>> _defining_ what "100% right" is for this test, since everything about
>> sparseness, right down to whether it's even a thing, is
>> filesystem-dependent.
>
> Indeed. Try running the test on a tmpfs or msdofs for example and you
> should see the test reliably fail.

It does fail on tmpfs.  I see this as a bug; it means that files written
sparsely might not fit, when I'd expect them to.  I can certainly
understand that the person who wrote tmpfs didn't get to this, but given
the long history of sparse support in the standard filesystem, I sort it
weakly into bug vs feature-I'd-expect-but-is-missing.

As for msdosfs, I am not surprised; that's a foreign fs with its own
format and semantics -- and one that is viewed as old and primitive.