bin/102745: "mount -o snapshot" removes any existing "-o" option from the mount

[Lapo Luchini]

>Number:         102745
>Category:       bin
>Synopsis:       "mount -o snapshot" removes any existing "-o" option from the mount
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Sep 01 10:10:22 GMT 2006
>Closed-Date:
>Last-Modified:
>Originator:     Lapo Luchini
>Release:        FreeBSD 6.1-STABLE i386
>Organization:
>Environment:
System: FreeBSD cyberx.home.lapo.it 6.1-STABLE FreeBSD 6.1-STABLE #59: Thu Jun 8 22:17:18 CEST 2006 root at cyberx.home.lapo.it:/usr/obj/usr/src/sys/CYBERX i386

>Description:

(edited for shortness, showing only relevant lines)

% mount                           
/dev/ad0s1f on /usr (ufs, local, soft-updates, acls)
% mount -u -o snapshot /usr/snap /usr
% mount                           
/dev/ad0s1f on /usr (ufs, local, soft-updates)
# now most services don't work anymore as ACLs are missing!
# not very nice to silently discard options
% mount -u -o acls /usr
% mount                           
/dev/ad0s1f on /usr (ufs, local, soft-updates, acls)
% mount -u -o acls,snapshot /usr/snap2 /usr
% mount
/dev/ad0s1f on /usr (ufs, local, soft-updates, acls)
# ok, but not very easy to be used from a script
% mount -u -o current,snapshot /usr/snap3 /usr
mount: -o current: option not supported
% mount -u -o fstab,snapshot /usr/snap3 /usr
mount: -o fstab: option not supported

IMvHO a snapshot should mount the file system exactly as it was before
the snapshot or, at least, accept to be paired with "current" or "fstab"
in order to automatically select the "same" options that were used.

PS: I know I could solve the problems with ACLs using "tunefs -a /usr"
and not needing a mount option anymore, but the problem is a bit more
general than that (and I only have remote access to that server, so I
can't possibly umount /usr in order to tunefs...).
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: