--- gnome-system-monitor-2.26.1/src/sysinfo.cpp	2009-04-16 11:44:31.402219136 +0100

+++ gnome-system-monitor-2.26.1-new/src/sysinfo.cpp	2009-04-16 11:46:28.735986864 +0100

@@ -126,6 +126,14 @@ namespace {

       this->free_space_bytes = 0;

       for (guint i = 0; i != mountlist.number; ++i) {

+        if ((string(entries[i].mountdir).compare("/") == 0) && \

+            (string(entries[i].type).compare("zfs") == 0)) {    

+      // Root filesystem is ZFS based: Calculate usage based on "/".

+      glibtop_fsusage usage;

+      glibtop_get_fsusage(&usage, "/");

+      this->free_space_bytes = usage.bavail * usage.block_size;       

+          break;

+        }

 	if (string(entries[i].devname).find("/dev/") != 0)

 	  continue;