mount: "nofail" option does not seem to work as expected

[Patrick McLean <chutzpah@gentoo.org>]

First the "nofail" doesn't actually prevent "failure" when using "mount
-a". If any filesystem fails to mount with mount -a due to the device
not existing, even if "nofail" is specified in the mount, mount will
exit with a status of 32. I would expect that "nofail" would imply that
such failures would cause the exit status to be 0.

Also, it seems that the "nofail" mount option does not work at all when
using the tag-style partition identifiers rather than udev symlinks.

Using this line in fstab:
UUID=nonexist /mnt/nonexist1 ext4 nofail 0 1

Will produce an error message:
# mount -av
mount: can't find UUID=nonexist
#

Where this line:
/dev/disk/by-uuid/nonexist /mnt/nonexist ext4 nofail 0 1

Does not produce any error:
# mount -av
#