Re: [PATCH 3/8] xfs: ensure log tail is always up to date

[Dave Chinner <david@fromorbit.com>]

On Sun, Jul 10, 2022 at 11:07:56PM -0700, Christoph Hellwig wrote:
> On Fri, Jul 08, 2022 at 11:55:53AM +1000, Dave Chinner wrote:
> >  	lockdep_assert_held(&log->l_icloglock);
> > @@ -544,7 +543,7 @@ xlog_state_release_iclog(
> >  	if ((iclog->ic_state == XLOG_STATE_WANT_SYNC ||
> >  	     (iclog->ic_flags & XLOG_ICL_NEED_FUA)) &&
> >  	    !iclog->ic_header.h_tail_lsn) {
> > -		tail_lsn = xlog_assign_tail_lsn(log->l_mp);
> > +		xfs_lsn_t tail_lsn = atomic64_read(&log->l_tail_lsn);
> >  		iclog->ic_header.h_tail_lsn = cpu_to_be64(tail_lsn);
> 
> Nit: I'd just do this as:
> 
> 		iclog->ic_header.h_tail_lsn =
> 			cpu_to_be64(atomic64_read(&log->l_tail_lsn));
> 
> > +/*
> > + * Callers should pass the the original tail lsn so that we can detect if the
> > + * tail has moved as a result of the operation that was performed. If the caller
> > + * needs to force a tail LSN update, it should pass NULLCOMMITLSN to bypass the
> > + * "did the tail LSN change?" checks.
> > + */
> 
> Should we also document the old_lsn == 0 case here?

I can, it's just the "tail did not change" value....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com