| Message ID | 20210121154526.1852176-6-bfoster@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | xfs: rework log quiesce to cover the log | expand |
On 1/21/21 8:45 AM, Brian Foster wrote: > Now that log covering occurs on quiesce, we'd like to reuse the > underlying superblock sync for final superblock updates. This > includes things like lazy superblock counter updates, log feature > incompat bits in the future, etc. One quirk to this approach is that > once the log is in the IDLE (i.e. already covered) state, any > subsequent log write resets the state back to NEED. This means that > a final superblock sync to an already covered log requires two more > sb syncs to return the log back to IDLE again. > > For example, if a lazy superblock enabled filesystem is mount cycled > without any modifications, the unmount path syncs the superblock > once and writes an unmount record. With the desired log quiesce > covering behavior, we sync the superblock three times at unmount > time: once for the lazy superblock counter update and twice more to > cover the log. By contrast, if the log is active or only partially > covered at unmount time, a final superblock sync would doubly serve > as the one or two remaining syncs required to cover the log. > > This duplicate covering sequence is unnecessary because the > filesystem remains consistent if a crash occurs at any point. The > superblock will either be recovered in the event of a crash or > written back before the log is quiesced and potentially cleaned with > an unmount record. > > Update the log covering state machine to remain in the IDLE state if > additional covering checkpoints pass through the log. This > facilitates final superblock updates (such as lazy superblock > counters) via a single sb sync without losing covered status. This > provides some consistency with the active and partially covered > cases and also avoids harmless, but spurious checkpoints when > quiescing the log. > > Signed-off-by: Brian Foster <bfoster@redhat.com> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Ok, makes sense Reviewed-by: Allison Henderson <allison.henderson@oracle.com> > --- > fs/xfs/xfs_log.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > index 7c31b046e790..6db65a4513a6 100644 > --- a/fs/xfs/xfs_log.c > +++ b/fs/xfs/xfs_log.c > @@ -2597,12 +2597,15 @@ xlog_covered_state( > int iclogs_changed) > { > /* > - * We usually go to NEED. But we go to NEED2 if the changed indicates we > - * are done writing the dummy record. If we are done with the second > - * dummy recored (DONE2), then we go to IDLE. > + * We go to NEED for any non-covering writes. We go to NEED2 if we just > + * wrote the first covering record (DONE). We go to IDLE if we just > + * wrote the second covering record (DONE2) and remain in IDLE until a > + * non-covering write occurs. > */ > switch (prev_state) { > case XLOG_STATE_COVER_IDLE: > + if (iclogs_changed == 1) > + return XLOG_STATE_COVER_IDLE; > case XLOG_STATE_COVER_NEED: > case XLOG_STATE_COVER_NEED2: > break; >
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 7c31b046e790..6db65a4513a6 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -2597,12 +2597,15 @@ xlog_covered_state( int iclogs_changed) { /* - * We usually go to NEED. But we go to NEED2 if the changed indicates we - * are done writing the dummy record. If we are done with the second - * dummy recored (DONE2), then we go to IDLE. + * We go to NEED for any non-covering writes. We go to NEED2 if we just + * wrote the first covering record (DONE). We go to IDLE if we just + * wrote the second covering record (DONE2) and remain in IDLE until a + * non-covering write occurs. */ switch (prev_state) { case XLOG_STATE_COVER_IDLE: + if (iclogs_changed == 1) + return XLOG_STATE_COVER_IDLE; case XLOG_STATE_COVER_NEED: case XLOG_STATE_COVER_NEED2: break;