On Thu, Aug 31, 2017 at 05:37:06PM +0300, Amir Goldstein wrote: > > index bcb2f860e508..3c0cbb98581e 100644 > > --- a/fs/xfs/xfs_log.c > > +++ b/fs/xfs/xfs_log.c > > @@ -2922,6 +2922,8 @@ xlog_state_done_syncing( > > iclog->ic_state = XLOG_STATE_DONE_SYNC; > > } > > > > + log->l_mp->m_flushseq++; > > I recon this should use WRITE_ONCE or smp_wmb() > and then also increment m_flush_submitted_seq *before* > issueing flush It's under l_icloglock, so we shouldn't need a WRITE_ONCE. If we did we'd need an atomic_t. > If state machine does not allow more than a single flush > to be in flight (?) then the 2 seq counters could be reduced > to single seq counter with (m_flushseq % 2) == 1 for submitted > and (m_flushseq % 2) == 0 for completed and the test in fsync > would be (flushseq % 2) == (READ_ONCE(mp->m_flushseq) % 2) The state machine allows multiple flushes to in flight.