heal: Fix healing empty directories (#7154)

This commit fixes the computation of Before/After healing state
for empty directories.

Issues before the commit:
- Before state doesn't reflect the real status (no StatVol() called)
- For any MakeVol() error, healObjectDir is exited directly, which is
  wrong.

cmd/xl-v1-healing.go

@@ -515,44 +515,55 @@ func (xl xlObjects) healObjectDir(ctx context.Context, bucket, object string, dr
 		ObjectSize:   0,
 	}
 
+	hr.Before.Drives = make([]madmin.HealDriveInfo, len(storageDisks))
+	hr.After.Drives = make([]madmin.HealDriveInfo, len(storageDisks))
+
+	var wg sync.WaitGroup
+
 	// Prepare object creation in all disks
-	for _, disk := range storageDisks {
-		if disk == nil {
-			hr.Before.Drives = append(hr.Before.Drives, madmin.HealDriveInfo{
-				UUID:  "",
-				State: madmin.DriveStateOffline,
-			})
-			hr.After.Drives = append(hr.After.Drives, madmin.HealDriveInfo{
-				UUID:  "",
-				State: madmin.DriveStateMissing,
-			})
-			continue
-		}
+	for i, d := range storageDisks {
+		wg.Add(1)
+		go func(idx int, disk StorageAPI) {
+			defer wg.Done()
+			if disk == nil {
+				hr.Before.Drives[idx] = madmin.HealDriveInfo{State: madmin.DriveStateOffline}
+				hr.After.Drives[idx] = madmin.HealDriveInfo{State: madmin.DriveStateOffline}
+				return
+			}
 
-		drive := disk.String()
-		hr.Before.Drives = append(hr.Before.Drives, madmin.HealDriveInfo{
-			UUID:     "",
-			Endpoint: drive,
-			State:    madmin.DriveStateMissing,
-		})
-		hr.After.Drives = append(hr.After.Drives, madmin.HealDriveInfo{
-			UUID:     "",
-			Endpoint: drive,
-			State:    madmin.DriveStateMissing,
-		})
+			drive := disk.String()
+			hr.Before.Drives[idx] = madmin.HealDriveInfo{UUID: "", Endpoint: drive, State: madmin.DriveStateOffline}
+			hr.After.Drives[idx] = madmin.HealDriveInfo{UUID: "", Endpoint: drive, State: madmin.DriveStateOffline}
+
+			_, statErr := disk.StatVol(pathJoin(bucket, object))
+			switch statErr {
+			case nil:
+				hr.Before.Drives[idx].State = madmin.DriveStateOk
+				hr.After.Drives[idx].State = madmin.DriveStateOk
+				// Object is fine in this disk, nothing to be done anymore, exiting
+				return
+			case errVolumeNotFound:
+				hr.Before.Drives[idx].State = madmin.DriveStateMissing
+				hr.After.Drives[idx].State = madmin.DriveStateMissing
+			default:
+				logger.LogIf(ctx, err)
+				return
+			}
 
-		if !dryRun {
-			if err := disk.MakeVol(pathJoin(bucket, object)); err != nil && err != errVolumeExists {
-				return hr, toObjectErr(err, bucket, object)
+			if dryRun {
+				return
 			}
 
-			for i, v := range hr.Before.Drives {
-				if v.Endpoint == drive {
-					hr.After.Drives[i].State = madmin.DriveStateOk
-				}
+			if err := disk.MakeVol(pathJoin(bucket, object)); err == nil || err == errVolumeExists {
+				hr.After.Drives[idx].State = madmin.DriveStateOk
+			} else {
+				logger.LogIf(ctx, err)
+				hr.After.Drives[idx].State = madmin.DriveStateOffline
 			}
-		}
+		}(i, d)
 	}
+
+	wg.Wait()
 	return hr, nil
 }