Unmounting by filesystem ID
Daniel C. Sobral
dcs at tcoip.com.br
Thu Jul 3 11:11:35 PDT 2003
Ian Dowse wrote:
> The patch below adds a new mount flag MNT_BYFSID that can be used
> to unmount a filesystem by specifying its filesystem ID instead of
> a path. The umount utility is changed to use this mechanism by
> default. This approach has a number of advantages:
>
> - It avoids any lookup operations that could potentially block
> forever, so filesystems such as NFS can be reliably unmounted
> even if the server is not responding but looking up the root node
> would require an RPC (maybe to an underlying filesystem).
> - The filesystem specification is unambiguous, so umount(8) can
> be sure that it is unmounting the correct filesystem (more
> work in umount(8) may be required here).
> - Detached filesystems can be unmounted. If a filesystem becomes
> detached from the filesystem hierarchy because the underlying
> filesystem got unmounted, it does not require a reboot to unmount
> it.
>
> Since unmounting by a path name is now only required for compatibility,
> in that case unmount() now just does a string comparison to find
> the correct filesystem. Also, this patch only affects unmounting;
> a similar approach could be applied to MNT_UPDATE mount operations.
>
> I would like to commit this during the next few days. Any comments
> or suggestions?
Just in the unlikely case no one has said this to your face yet, man,
you rule.
--
Daniel C. Sobral (8-DCS)
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E-mail: Daniel.Capo at tco.net.br
Daniel.Sobral at tcoip.com.br
dcs at tcoip.com.br
Outros:
dcs at newsguy.com
dcs at freebsd.org
capo at notorious.bsdconspiracy.net
One time the police stopped me for speeding. They said, "Don't you know the
speed limit is fifty-five miles an hour?" I said, "Yeah, I know, but I
wasn't
going to be out that long."
-- Steven Wright
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