[arch-projects] Mounting nodev fs with "none" as source.

[Gerardo Exequiel Pozzi]

Hello

I recently discovered an issue when _not_ using "none" as source of 
nodev filesystems. For example in our default fstab for /tmp as source 
is used "tmp". If you run "mount -a" under a directory with a "tmp" 
directory, /tmp will be mounted again as tmpfs with "fake source" as 
$PWD/tmp:

# mount | grep /tmp
tmp on /tmp type tmpfs (rw,relatime)
# pwd
/root
# mkdir tmp
# mount -a
# mount | grep /tmp
tmp on /tmp type tmpfs (rw,relatime)
/root/tmp on /tmp type tmpfs (rw,relatime)

But if using special keyword "none" as source this does not happen.

# mount | grep /tmp
none on /tmp type tmpfs (rw,relatime)
# pwd
/root
# mkdir none
# mount -a
# mount | grep /tmp
none on /tmp type tmpfs (rw,relatime)

In the past (when /etc/mtab was not linked to /proc/self/mounts) weird 
behaviours appears when using "none" as source, but now seems that works 
fine.
Other ways to workaround this is using the same path as source. I think 
we can also change source to "none" of /dev /run /proc /dev/shm and 
/dev/pts, looks like more correct. (or using the same path as source).

I tested using none in all nodev fs and shutdown is clean without 
errors. what do you think?

-- 
Gerardo Exequiel Pozzi
\cos^2\alpha + \sin^2\alpha = 1