Re: [PATCH v9 13/15] xfs: add xfs_compute_atomic_write_unit_max()

[John Garry]

On 01/05/2025 05:30, Darrick J. Wong wrote:
> On Wed, Apr 30, 2025 at 08:52:00AM +0100, John Garry wrote:
> > On 25/04/2025 17:45, John Garry wrote:
> > > +static inline xfs_extlen_t xfs_calc_perag_awu_max(struct xfs_mount *mp)
> > > +{
> > > +	if (mp->m_ddev_targp->bt_bdev_awu_min > 0)
> > > +		return max_pow_of_two_factor(mp->m_sb.sb_agblocks);
> > > +	return mp->m_ag_max_usable;
> > I think that this should be rounddown_pow_of_two(mp->m_ag_max_usable)
> >
> > ditto for rt
> >
> > I will fix (unless disagree).
> I don't think this needs fixing.  If there's no hardware support on the
> device, then we can do any size of atomic write that we want.

Check man pages for statx:

stx_atomic_write_unit_min
stx_atomic_write_unit_max
              ... These values are each guaranteed to be
              a power-of-2.

Same is enforced for size for RWF_ATOMIC.