md: improve usefulness and accuracy of sysfs file md/sync_completed.

The sync_completed file reports how much of a resync (or recovery or
reshape) has been completed.
However due to the possibility of out-of-order completion of writes,
it is not certain to be accurate.

We have an internal value - mddev->curr_resync_completed - which is an
accurate value (though it might not always be quite so uptodate).

So:
 - make curr_resync_completed be uptodate a little more often,
   particularly when raid5 reshape updates status in the metadata
 - report curr_resync_completed in the sysfs file
 - allow poll/select to report all updates to md/sync_completed.

This makes sync_completed completed usable by any external metadata
handler that wants to record this status information in its metadata.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3bbc6d647044..76892ac72544 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3845,6 +3845,7 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
                 wait_event(conf->wait_for_overlap,
                            atomic_read(&conf->reshape_stripes)==0);
                 mddev->reshape_position = conf->reshape_progress;
+                mddev->curr_resync_completed = mddev->curr_resync;
                 conf->reshape_checkpoint = jiffies;
                 set_bit(MD_CHANGE_DEVS, &mddev->flags);
                 md_wakeup_thread(mddev->thread);
@@ -3854,6 +3855,7 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
                 conf->reshape_safe = mddev->reshape_position;
                 spin_unlock_irq(&conf->device_lock);
                 wake_up(&conf->wait_for_overlap);
+                sysfs_notify(&mddev->kobj, NULL, "sync_completed");
         }
 
         if (mddev->delta_disks < 0) {
@@ -3943,6 +3945,7 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
                 wait_event(conf->wait_for_overlap,
                            atomic_read(&conf->reshape_stripes) == 0);
                 mddev->reshape_position = conf->reshape_progress;
+                mddev->curr_resync_completed = mddev->curr_resync;
                 conf->reshape_checkpoint = jiffies;
                 set_bit(MD_CHANGE_DEVS, &mddev->flags);
                 md_wakeup_thread(mddev->thread);
@@ -3953,6 +3956,7 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
                 conf->reshape_safe = mddev->reshape_position;
                 spin_unlock_irq(&conf->device_lock);
                 wake_up(&conf->wait_for_overlap);
+                sysfs_notify(&mddev->kobj, NULL, "sync_completed");
         }
         return reshape_sectors;
 }