When (re)mounting a FS with 'acl' option, this is not showed up in /proc/mounts.
As ACL does not work when a FS is mounted without this option, this could be
worth to publish this information though /proc/mounts the same way as other
That's how it's expected to work. The kernel tracks _some_ of the flags in
/proc/mounts (specifically, those ones which are the same across all
filesystems); others are tracked in user space via /etc/mtab. The mount(8)
binary assembles both of these to provide mount information.
/dev/hda6 on / type ext3 (rw)
# mount -o remount,acl /
/dev/hda6 on / type ext3 (rw,acl)
# mount -o remount,noacl /
/dev/hda6 on / type ext3 (rw,noacl)
That has been the defined behaviour for ages; if you want to see all the
information, call mount(8) directly, don't just parse /proc/mounts.