Hi Ian,
On Tue, 30 Sep 2003, Ian Kent wrote:
> On Mon, 29 Sep 2003, Ion Badulescu wrote:
> > The daemon version doesn't matter, any daemon will do. All you need is to
> > kill -9 automountd while something is mounted, and then unmount everything
> > by hand without removing the mountpoint directories.
> >
>
> Yes, your'e exactly right. That's expected behaviour as the directory
> dentries still exist and there is no daemon to remove them.
Hmm. Expected behaviour, you say? Maybe, maybe not, it's hard to tell
what's to be expected here, since the autofs umount semantics are so
different from a regular filesystems.
Normally a filesystem is allowed to be unmounted if it is not busy, right?
But with autofs it's different, it should be unmounted only if it is
completely empty, with no entries at all -- and I'm not convinced the VFS
layer is up to the task of dealing with this requirement. Alternatively
the autofs code should be prepared to clean up after itself, but that
might not be possible in all circumstances.
> Hence the message. Seeing this message has always been a signal to me
> that the daemon has a bug.
Oh, you're absolutely right here (although we're talking about different
daemons, I'm using--and expanding, and debugging--amd's autofs support).
:-) Nonetheless, it's a bug in the kernel code that should be remedied.
> I have been thinking that implementing a umount_begin routine in the
> super_operations for autofs4 would remedy the problem. I believe that,
> correct me if I'm wrong, the umount must be done with a force option in
> this case, so the umount_begin would be called.
No, you're right, you need MNT_FORCE for umount_begin to be called.
That, however, would be a reasonable solution if the filesystem also
prevented its own unmounting when it is not empty (by having each entry
hold a reference to the vfsmount in its private data, perhaps, I'm not
sure). Then, inside umount_begin, and only if the filesystem is catatonic,
it would garbage-collect any entries not mounted upon and not busy. That
should work, I think...
Thanks,
Ion
--
It is better to keep your mouth shut and be thought a fool,
than to open it and remove all doubt.
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