Libguestfs - Apr 2022 - xfs protofiles for libguestfs

Hi all,

I hope I am in the right place, I found this email by following the
link in the project README.  We are collecting use cases for xfs dev
projects, one of which would be enhancing xfs protofiles, which is a
type of script that facilitates filesystem generation.  I am not very
familiar with libguestfs, but a coworker suggested that this might be
of interest to your project.  More specifically, the task would be to
add attributes to the files generated by the protofile script.  Does
this sound like something that might be of use to libguestfs?  I did
take a quick glance through the libguestfs code, and didnt notice any
current usage of xfs protofiles, but I thought it was worth asking if protofiles
might become of interest if we did add this feature.  Thanks!

Allison

On Sat, Apr 02, 2022 at 08:18:52AM -0700, Alli wrote:
> Hi all,
> I hope I am in the right place, I found this email by following the
> link in the project README.  We are collecting use cases for xfs dev
> projects, one of which would be enhancing xfs protofiles, which is a
> type of script that facilitates filesystem generation.  I am not
> very familiar with libguestfs, but a coworker suggested that this
> might be of interest to your project.  More specifically, the task
> would be to add attributes to the files generated by the protofile
> script.  Does this sound like something that might be of use to
> libguestfs?  I did take a quick glance through the libguestfs code,
> and didnt notice any current usage of xfs protofiles, but I thought
> it was worth asking if protofiles might become of interest if we did
> add this feature.  Thanks!
Hello Allison,

I have to admit I'm not sure what any of this means.  Also the
information about protofiles is a bit thin.  There is some information
in the mkfs.xfs(8) man page, but even that is a bit unclear.

Is it like the (very useful) "-d" option of mke2fs?

Libguestfs does not currently provide a binding around mkfs.xfs.
Instead we rely on generic mkfs support and that only encodes a few
baseline mkfs features like blocksize:

https://github.com/libguestfs/libguestfs/blob/3115726aca7d898be3b1191d32290ca78edf6ebc/generator/actions_core.ml#L5967
https://github.com/libguestfs/libguestfs/blob/3115726aca7d898be3b1191d32290ca78edf6ebc/daemon/mkfs.c#L43

This is unusual.  We do support other mkfs-like tools more directly, eg mke2fs:

https://github.com/libguestfs/libguestfs/blob/3115726aca7d898be3b1191d32290ca78edf6ebc/generator/actions_core.ml#L7675
https://github.com/libguestfs/libguestfs/blob/3115726aca7d898be3b1191d32290ca78edf6ebc/daemon/ext2.c#L913

And we also currently have support for other xfs_* tools like
xfs_info, xfs_growfs.  Just not (yet) any support for mkfs.xfs.

I've copied Eric Sandeen in on this email as he usually knows a lot
more than I do.

Rich.

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