Comment 10 for bug 444915

Sure. First, I disabled dk-disks to turn off all automount magic:

# killall devkit-disks-daemon
# chmod 0 /usr/lib/devicekit-disks/devkit-disks-daemon

Now, mount my removable USB HD:

# echo 3 >/proc/sys/vm/drop_caches
# mount /dev/sdb1 /mnt; time df -h
[...]
/dev/sdb1 233G 226G 7,5G 97% /mnt

real 1m16.649s
user 0m0.000s
sys 0m1.050s

It works fine with usefree:

# mount -o usefree /dev/sdb1 /mnt; time df -h
[...]
/dev/sdb1 233G 226G 7,5G 97% /mnt

real 0m0.005s
user 0m0.010s
sys 0m0.000s

And strace shows that it's statfs:

# mount /dev/sdb1 /mnt; strace -vtt df -h
[...]
12:15:12.103174 statfs("/home/martin/.gv
f_files=0, f_ffree=0, f_fsid={0, 0}, f_n
12:15:12.103312 statfs("/mnt",

... long pause here, with

root 21844 2.9 0.0 5536 940 pts/5 D+ 12:15 0:01 df -h

(deep kernel sleep)

and a minute later it finishes:

12:15:12.103312 statfs("/mnt", {f_type="MSDOS_SUPER_MAGIC", f_bsize=16384, f_blocks=15254800, f_bfree=486982, f_bavail=486982, f_files=0, f_ffree=0, f_fsid={2065, 0}, f_namelen=260, f_frsize=16384}) = 0
12:16:26.772458 write(1, "/dev/sdb1 233G 226G"..., 49/dev/sdb1 233G 226G 7,5G 97% /mnt