Re: Increase in XFS journal flushes with (direct_write;fdatasync)+

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2026-05-08 at 10:43 +0200, Christoph Hellwig wrote:
> On Fri, May 08, 2026 at 10:29:38AM +0200, Pankaj Raghav wrote:
> >                 } else {
> > -                       if (inode_maybe_inc_iversion(inode, !!dirty))
> > +                       /*
> > +                        * Don't force iversion increment for pure lazytime
> > +                        * updates (when dirty is set to I_DIRTY_TIME only).
> > +                        */
> > +                       if (inode_maybe_inc_iversion(inode,
> > +                                                    dirty != I_DIRTY_TIME))
> >                                 dirty |= I_DIRTY_SYNC;
> >                 }
> >         }
> > 
> > If you are tests are passing, then I can send a fix as a separate patch.
> 
> The comment needs to explain the why and not the how.   AFAICS the
> why is that lazytime is not propagated to the disk at this mount,
> so incrementing i_version should not happen, but I'm adding Jeff
> for insights.
> 
> 

That looks correct to me. I think the logic here is:

If we're going to disk anyway, then we might as well force an i_version
update. In the case where we're not (dirty == I_DIRTY_TIME), then we
only want to do an i_version update if someone has queried it. If an
i_version update does occur, then we need to go to disk by setting
I_DIRTY_SYNC.
-- 
Jeff Layton <jlayton@kernel.org>