misc/74387: linprocfs can be mounted on top of itself many times

[J. Porter Clark]

>Number:         74387
>Category:       misc
>Synopsis:       linprocfs can be mounted on top of itself many times
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Nov 25 21:10:19 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator:     J. Porter Clark
>Release:        5.3-STABLE
>Organization:
NASA MSFC
>Environment:
FreeBSD auricle.charter.net 5.3-STABLE FreeBSD 5.3-STABLE #0: Wed Nov 24 16:07:39 CST 2004     jpc at auricle.charter.net:/usr/obj/usr/src/sys/AURICLE5  i386

>Description:
mount -a, when executed repeatedly, mounts a linprocfs filesystem listed in /etc/fstab multiple times.  This isn't like procfs.
Although I first noticed this problem on 5.3, it is present on 4.10.   
>How-To-Repeat:
With the standard line in /etc/fstab for linprocfs, run mount -a several times, then run mount.  You will see an output like this:
$ mount
/dev/ad0s3a on / (ufs, local)
devfs on /dev (devfs, local)
/dev/ad0s3e on /tmp (ufs, local, soft-updates)
/dev/ad0s3g on /usr (ufs, local, soft-updates)
/dev/ad0s3f on /var (ufs, local, soft-updates)
procfs on /proc (procfs, local)
linprocfs on /usr/compat/linux/proc (linprocfs, local)
linprocfs on /usr/compat/linux/proc (linprocfs, local)
linprocfs on /usr/compat/linux/proc (linprocfs, local)
linprocfs on /usr/compat/linux/proc (linprocfs, local)
linprocfs on /usr/compat/linux/proc (linprocfs, local)
linprocfs on /usr/compat/linux/proc (linprocfs, local)

Note that the extra mounts can be umounted, one at a time, similarly.
>Fix:
Unknown.
>Release-Note:
>Audit-Trail:
>Unformatted: