master: fix negative active volumes (#7440)

* fix negative active volumes

* address comments

* simplify

weed/topology/disk.go

@@ -176,6 +176,19 @@ func (d *Disk) doAddOrUpdateVolume(v storage.VolumeInfo) (isNew, isChanged bool)
 			d.UpAdjustDiskUsageDelta(types.ToDiskType(v.DiskType), deltaDiskUsage)
 		}
 		isChanged = d.volumes[v.Id].ReadOnly != v.ReadOnly
+		if isChanged {
+			// Adjust active volume count when ReadOnly status changes
+			// Use a separate delta object to avoid affecting other metric adjustments
+			readOnlyDelta := &DiskUsageCounts{}
+			if v.ReadOnly {
+				// Changed from writable to read-only
+				readOnlyDelta.activeVolumeCount = -1
+			} else {
+				// Changed from read-only to writable
+				readOnlyDelta.activeVolumeCount = 1
+			}
+			d.UpAdjustDiskUsageDelta(types.ToDiskType(v.DiskType), readOnlyDelta)
+		}
 		d.volumes[v.Id] = v
 	}
 	return