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

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 4/4] Adds ioctl interface support for ext4 project
From: Jan Kara <jack@xxxxxxx>
Date: Wed, 24 Sep 2014 19:01:05 +0200
Cc: Jan Kara <jack@xxxxxxx>, Li Xi <pkuelelixi@xxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-api@xxxxxxxxxxxxxxx, tytso@xxxxxxx, adilger@xxxxxxxxx, viro@xxxxxxxxxxxxxxxxxx, dmonakhov@xxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140924162634.GA16886@xxxxxxxxxxxxx>
References: <1411567470-31799-1-git-send-email-lixi@xxxxxxx> <1411567470-31799-5-git-send-email-lixi@xxxxxxx> <20140924162507.GC27000@xxxxxxxxxxxxx> <20140924162634.GA16886@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed 24-09-14 09:26:34, Christoph Hellwig wrote:
> 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.
  Do you mean full get/setfsxattr API? That basically contains project ID,
flags (those that are currently get/set with FS_IOC_GETFLAGS/SETFLAGS), and
extent size hint right? That seems workable and it would also make setting
of PROJINHERIT flag fs agnostic. Only we would have to create some generic
flags namespace and merge into that ext4 flags and have a translation
function for the old ext4 flags. Also I'm afraid we may quickly run out of
32 available flags in xflags so we'd need to extend that. But all this
seems to be doable.
Jan Kara <jack@xxxxxxx>

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