Re: [GEDI] [PATCH 07/17] gluster: Drop useless has_zero_init callback

[Eric Blake]

On 2/17/20 6:03 AM, Eric Blake wrote:

>  >
>  > Creation or truncation should behave just as on a file on a local
>  > filesystem. So maybe qemu_gluster_known_zeroes is not needed at all?
>
> Which version of gluster first required a regular filesystem backing for 
> all gluster files?  Does qemu support older versions (in which case, 
> what is the correct version-probing invocation to return 0 prior to that 
> point, and 1 after), or do all versions supported by qemu already 
> guarantee zero initialization on creation or widening truncation by 
> virtue of POSIX file semantics (in which case, patch 7 should instead 
> switch to using .bdrv_has_zero_init_1 for both functions)?  Per 
> configure, we probe for glusterfs_xlator_opt from gluster 4, which 
> implies the code still tries to be portable to even older gluster, but 
> I'm not sure if this squares with qemu-doc.texi which mentions our 
> minimum distro policy (for example, now that qemu requires python 3 
> consistent with our distro policy, that rules out several older systems 
> where older gluster was likely to be present).

For reference, I quickly found commit efc6c070ac as an example of 
bumping minimum versions (however, that commit is from 2018, so I'm sure 
there are even more recent examples, just not with the same keywords 
that I was searching for).

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org