Re: [PATCH v2 1/3] fs: add infrastructure for multigrain inode i_m/ctime

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2023-04-25 at 08:40 +1000, NeilBrown wrote:
> On Tue, 25 Apr 2023, Jeff Layton wrote:
> > On Tue, 2023-04-25 at 07:47 +1000, NeilBrown wrote:
> > > On Tue, 25 Apr 2023, Jeff Layton wrote:
> > > > +	/*
> > > > +	 * Warn if someone sets SB_MULTIGRAIN_TS, but doesn't turn down the ts
> > > > +	 * granularity.
> > > > +	 */
> > > > +	return (sb->s_flags & SB_MULTIGRAIN_TS) &&
> > > > +		!WARN_ON_ONCE(sb->s_time_gran == 1);
> > > 
> > >  Maybe 
> > > 		!WARN_ON_ONCE(sb->s_time_gran & SB_MULTIGRAIN_TS);
> > >  ??
> > > 
> > 
> > I'm not sure I understand what you mean here.
> 
> That's fair, as what I wrote didn't make any sense.
> I meant to write:
> 
>  		!WARN_ON_ONCE(sb->s_time_gran & I_CTIME_QUERIED);
> 
> to make it explicit that s_time_gran must leave space for
> I_CTIME_QUERIED to be set (as you write below).  Specifically that
> s_time_gran mustn't be odd. 
>   

Erm...it may be an unpopular opinion, but I find that more confusing
than just ensuring that the s_time_gran > 1. I keep wondering if we
might want to carve out other low-order bits too for some later purpose,
at which point trying to check this using flags wouldn't work right. I
think I might just stick with what I have here, at least for now.

-- 
Jeff Layton <jlayton@kernel.org>