Description of problem:
G-S-M seems to compute total disc space by adding up space available to a select list of entries under the "File Systems" tab, even though several of these may be on the same device (on a default install, /tmp, /var/tmp and /home seem to be getting their own mtab entries). So for example, on my tablet witha 32 GB SSD, the overview claims 78 GiB is available.

Conversely, nautilus seems to report free space correctly.

Output of df --total:


$ df --total
Filesystem           1K-blocks      Used Available Use% Mounted on
rootfs                27925684   7316676  20325396  27% /
udev                    508804         0    508804   0% /dev
tmpfs                   511312       448    510864   1% /dev/shm
tmpfs                   511312       700    510612   1% /run
/dev/sda3             27925684   7316676  20325396  27% /
tmpfs                   511312         0    511312   0% /sys/fs/cgroup
tmpfs                   511312         0    511312   0% /media
/dev/sda1               495844     40275    429969   9% /boot
/dev/sda3             27925684   7316676  20325396  27% /tmp
/dev/sda3             27925684   7316676  20325396  27% /var/tmp
/dev/sda3             27925684   7316676  20325396  27% /home
total                142678316  36624803 104609853  26%


Output of mount:


$ mount
/proc on /proc type proc (rw,relatime)
/sys on /sys type sysfs (rw,relatime,seclabel)
udev on /dev type devtmpfs (rw,nosuid,relatime,seclabel,size=508804k,nr_inodes=127201,mode=755)
devpts on /dev/pts type devpts (rw,relatime,seclabel,gid=5,mode=620,ptmxmode=000)
tmpfs on /dev/shm type tmpfs (rw,relatime,seclabel)
tmpfs on /run type tmpfs (rw,nosuid,nodev,noexec,relatime,seclabel,mode=755)
/dev/sda3 on / type ext4 (rw,noatime,seclabel,barrier=1,data=ordered,discard)
selinuxfs on /selinux type selinuxfs (rw,relatime)
tmpfs on /sys/fs/cgroup type tmpfs (rw,nosuid,nodev,noexec,relatime,seclabel,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/ns type cgroup (rw,nosuid,nodev,noexec,relatime,ns)
cgroup on /sys/fs/cgroup/cpu type cgroup (rw,nosuid,nodev,noexec,relatime,cpu)
cgroup on /sys/fs/cgroup/cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/net_cls type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
systemd-1 on /sys/kernel/debug type autofs (rw,relatime,fd=27,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
systemd-1 on /dev/hugepages type autofs (rw,relatime,fd=28,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=29,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
systemd-1 on /dev/mqueue type autofs (rw,relatime,fd=30,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
systemd-1 on /sys/kernel/security type autofs (rw,relatime,fd=31,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
tmpfs on /media type tmpfs (rw,nosuid,nodev,noexec,relatime,rootcontext=system_u:object_r:mnt_t:s0,seclabel,mode=755)
/dev/sda1 on /boot type ext4 (rw,noatime,seclabel,barrier=1,data=ordered,discard)
/dev/sda3 on /tmp type ext4 (rw,noatime,seclabel,barrier=1,data=ordered,discard)
/dev/sda3 on /var/tmp type ext4 (rw,noatime,seclabel,barrier=1,data=ordered,discard)
/dev/sda3 on /home type ext4 (rw,noatime,seclabel,barrier=1,data=ordered,discard)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
gvfs-fuse-daemon on /home/james/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,relatime,user_id=500,group_id=500)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,seclabel)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,relatime)
mqueue on /dev/mqueue type mqueue (rw,relatime,seclabel)
securityfs on /sys/kernel/security type securityfs (rw,relatime)



Screenshots attached.

Version-Release number of selected component (if applicable):
gnome-system-monitor-3.0.0-1.fc15.i686gnome-system-monitor-3.0.0-1.fc15.i686

Expected results:
G-S-M computes available space on a per-volume rather than per-mount-point basis.