Why won't 8.2 umount -f?
rmacklem at uoguelph.ca
Tue Feb 14 03:13:31 UTC 2012
Doug Barton wrote:
> On 02/13/2012 18:23, Rick Macklem wrote:
> > Doug Barton wrote:
> >> Is there some magic I'm missing to convince an 8.2 system to umount
> >> -f?
> >> I had an NFS server crash, so I'm trying to get the mounts updated.
> >> All
> >> of the 7.x systems happily did 'umount -f', but the 8.x systems
> >> (mostly
> >> 8.2-pN) are just hanging forever.
> >> Is this a bug, or is it something I'm missing?
> > Well, I didn't realize that a 7.n system would "umount -f" an NFS
> > mount when the server was down and there were dirty blocks that
> > needed to be written back, but I don't know.
> I'm doubtful that any of those systems had dirty blocks.
> > (I seem to recall that
> > someone encouraged me to MFC one of my changes related to this back
> > to stable/7, but I'm not sure if it mattered?)
> Please don't unless you can verify that it doesn't make this situation
> worse. :)
sbruno did the MFC. I don't think the changes would make it worse.
> > I have pretty well fixed the new client w.r.t. this except for the
> > case where you do a "umount <path>" and that gets hung. Once a non
> > "-f"
> > umount gets hung, there is nothing you can do, because the mount
> > point is
> > locked up, so a subsequent "umount -f" can't get as far as
> > nfs_umount().
> I'm aware of this issue, and I did 'umount -f' first. But I wonder if
> this isn't something that should be fixed because I think most users
> would expect that 'umount -> umount -f' would be the natural
> progression, similar to 'kill -> kill -9'.
> > My guess is that the old (default for 8.n) client isn't fixed for
> > this. If you "grep MNTK_UNMOUNTF" in the sources, you'll see it
> > used some in the old/regular client, but not as much as the new one.
> > You also need a fairly recent (can't remember if that is in 8.2)
> > version of umount.c, since the code had a "sync();" at the beginning
> > of it that would hang before even getting to the umount(2) syscall.
I just looked and at least some of the fixes were MFC'd to stable/8 about
8months ago. So, they aren't in 8.2, but will be in 8.3.
> > Bottom line, I think the newnfs client (the default for 9.0) can
> > do this, but I'm doubtful the old/reguler one can. (I also wouldn't
> > be surprised if there is still a bug other than the above mentioned
> > one w.r.t. doing a "umount /mnt" and getting that hung before trying
> > "umount -f /mnt".
> Is the new client in 8-stable up to date relevant to 9.0, and/or is it
> considered safe to use in production?
It looks like stable/8 might be ok using either client. The newnfs in
stable/8 should be up to date w.r.t. bugfixes in the new/regular client
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