Re: [PATCH 01/16] xfs: fix chown leaking delalloc quota blocks when fssetxattr fails

[Christoph Hellwig <hch@infradead.org>]

On Tue, Feb 02, 2021 at 09:47:26AM -0800, Darrick J. Wong wrote:
> > > +	prevdq->q_blk.reserved -= ip->i_delayed_blks;
> > > +	xfs_dqunlock(prevdq);
> > > +
> > 
> > What's the reason for not using xfs_trans_reserve_quota_bydquots(NULL,
> > ...) here like the original code?
> 
> xfs_trans_reserve_quota_bydquots() makes the caller pass in user, group,
> and project dquots.  It's not difficult to add more code to declare and
> route parameters, but that just felt overdone.
> 
> Given that this is the only place in the codebase where we want to
> change the incore quota reservation on a single dquot, I also didn't
> think it was worth making a whole new function.
> 
> FWIW I don't really mind doing it, it just seemed like more work.
> Alternately I suppose I could expose xfs_trans_dqresv.

xfs_trans_dqresv sounds way better than
xfs_trans_reserve_quota_bydquots. But I'm also perfectly fine with
the current open coded version.  If we insist on layering my preference
would be a new custom helper just for this case instead of going through
much more heavyweight functions.