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, 22 insertions, 12 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 298731b8e951..7af64f3846a6 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2017,6 +2017,8 @@ repeat:
         clear_bit(MD_CHANGE_PENDING, &mddev->flags);
         spin_unlock_irq(&mddev->write_lock);
         wake_up(&mddev->sb_wait);
+        if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
+                sysfs_notify(&mddev->kobj, NULL, "sync_completed");
 
 }
 
@@ -3486,12 +3488,15 @@ sync_completed_show(mddev_t *mddev, char *page)
 {
         unsigned long max_sectors, resync;
 
+        if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
+                return sprintf(page, "none\n");
+
         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
                 max_sectors = mddev->resync_max_sectors;
         else
                 max_sectors = mddev->dev_sectors;
 
-        resync = (mddev->curr_resync - atomic_read(&mddev->recovery_active));
+        resync = mddev->curr_resync_completed;
         return sprintf(page, "%lu / %lu\n", resync, max_sectors);
 }
 
@@ -6338,18 +6343,12 @@ void md_do_sync(mddev_t *mddev)
                 sector_t sectors;
 
                 skipped = 0;
-                if (j >= mddev->resync_max) {
-                        sysfs_notify(&mddev->kobj, NULL, "sync_completed");
-                        wait_event(mddev->recovery_wait,
-                                   mddev->resync_max > j
-                                   || kthread_should_stop());
-                }
-                if (kthread_should_stop())
-                        goto interrupted;
 
-                if (mddev->curr_resync > mddev->curr_resync_completed &&
-                    (mddev->curr_resync - mddev->curr_resync_completed)
-                    > (max_sectors >> 4)) {
+                if ((mddev->curr_resync > mddev->curr_resync_completed &&
+                     (mddev->curr_resync - mddev->curr_resync_completed)
+                    > (max_sectors >> 4)) ||
+                    j >= mddev->resync_max
+                        ) {
                         /* time to update curr_resync_completed */
                         blk_unplug(mddev->queue);
                         wait_event(mddev->recovery_wait,
@@ -6357,7 +6356,17 @@ void md_do_sync(mddev_t *mddev)
                         mddev->curr_resync_completed =
                                 mddev->curr_resync;
                         set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+                        sysfs_notify(&mddev->kobj, NULL, "sync_completed");
                 }
+
+                if (j >= mddev->resync_max)
+                        wait_event(mddev->recovery_wait,
+                                   mddev->resync_max > j
+                                   || kthread_should_stop());
+
+                if (kthread_should_stop())
+                        goto interrupted;
+
                 sectors = mddev->pers->sync_request(mddev, j, &skipped,
                                                   currspeed < speed_min(mddev));
                 if (sectors == 0) {
@@ -6465,6 +6474,7 @@ void md_do_sync(mddev_t *mddev)
 
  skip:
         mddev->curr_resync = 0;
+        mddev->curr_resync_completed = 0;
         mddev->resync_min = 0;
         mddev->resync_max = MaxSector;
         sysfs_notify(&mddev->kobj, NULL, "sync_completed");