Re: [Qemu-devel] [PATCH] block/gluster: defend on legacy ftruncate api use

[Eric Blake]

n 04/12/2018 08:31 AM, Niels de Vos wrote:
> This change looks good to me, but a commit message would have been
> helpful. I suggest something like this:
> 
>   Gluster 4.0 changed the signature of glfs_ftruncate(). The function
>   now has two additional arguments, namely prestat and poststat. These
>   provide not benefit for QEMU, so ignoring them and passing NULL makes
>   the gluster-block driver compile with the new Gluster version again.
> 
> And maybe add this too:
> 
>   Glusters libgfapi uses symbol versioning and provides backwards
>   compatible functions. Binaries compiled against previous versions of
>   Gluster keep on functioning with the new library.
> 

>> @@ -3856,6 +3857,9 @@ if test "$glusterfs" != "no" ; then
>>        glusterfs_fallocate="yes"
>>        glusterfs_zerofill="yes"
>>      fi
>> +    if ! $pkg_config --atleast-version=7.4 glusterfs-api; then
>> +      glusterfs_legacy_ftruncate="yes"

Also, version-based tests are lousy.  Feature-based tests (does a call
to glfs_ftruncate(0, 0) compile without error? then we are legacy) are
less brittle, especially when features can be backported across
versions.  So this should be reworked to a compile check, rather than a
version query.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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