Date: Tue, 29 Jan 2002 22:20:20 -0500 From: Brent Verner <brent@rcfile.org> To: freebsd-hackers@freebsd.org Subject: multiple mounts of single device Message-ID: <20020130032020.GA5077@rcfile.org>
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Hi,
I've been searching for info regarding mounting the same device
to multiple locations in the filesystem, i.e...
# mount /dev/ad0s1e /usr
# mount -r /dev/ad0s1e /var/jail/AAAA/usr
# mount -r /dev/ad0s1e /var/jail/BBBB/usr
[Warning: I /know/ I know next-to-nothing about filesystems... but]
I recall seeing some traffic (IIRC, from early 2001) about this
ability being in -current, but looking at
HEAD:/usr/sys/ufs/ffs/ffs_vfsops.c, I still see around line 571
that EBUSY is still being returned if the device is already mounted.
Not being familiar with the fbsd code... Am I even in the correct
ballpark? Or is this functionality already present in -current?
If it is already in -current, where would I start digging around
if I felt like (breaking a perfectly good 4.5 install and) trying
to integrate the -current code into 4.5?
I'd especially appreciate any two minute (or less) response to
any of the following questions -- I'm perfectly comfortable being
told "go away and read," if I have some idea of what to read.
0) Is this multiple mount point functionality even necessary,
or is there a better/existing mechanism to achieve the
same goal (aside from local nfs mount).
1) What is the danger of not failing with EBUSY if the device
is already mounted?
2) Would supporting multiple mounts require modifying any code
outside the filesystem (/usr/sys/src/ufs/ffs)? If so, how
much and where?
thanks.
brent
--
"Develop your talent, man, and leave the world something. Records are
really gifts from people. To think that an artist would love you enough
to share his music with anyone is a beautiful thing." -- Duane Allman
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