Re: [PATCH 4/4] Adds ioctl interface support for ext4 project

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Wed, Sep 24, 2014 at 06:25:07PM +0200, Jan Kara wrote:
> On Wed 24-09-14 22:04:30, Li Xi wrote:
> > This patch adds ioctl interface for setting/getting project of ext4.
>   The patch looks good to me. I was just wondering whether it won't be
> useful to add an ioctl() which isn't ext4 specific. We could just extend
> ->setattr() to allow setting of project ID (most filesystems would just
> return -EOPNOTSUPP but ext4 and xfs could do the right thing) and then call
> ->setattr from the generic ioctl. That way userspace won't have to care
> about filesystem type when setting project ID... What do others think?

Absolutely.  In general I also wonder why this patch doesn't implement
the full XFS API.  Maybe there is a reason it was considered and
rejected, but it would be helpful to document why.