umount -f implementation
Nathanael Hoyle
nhoyle at hoyletech.com
Mon Jun 29 00:44:54 UTC 2009
Rick Macklem wrote:
> I just noticed that when I do the following:
> - start a large write to an NFS mounted fs
> - network partition the server (unplug a net cable)
> - do a "umount -f <mntpoint>" on the machine
>
> that it gets stuck trying to write dirty blocks to the server.
>
> I had, in the past, assumed that a "umount -f" of an NFS mount would be
> used to get rid of an NFS mount on an unresponsive server and that loss
> of "writes in progress" would be expected to happen.
>
> Does that sound correct? (In other words, an I seeing a bug or a
> feature?)
>
> Thanks in advance for any info, rick
> ps: I have a simple "fix" if this is a bug, but I wanted to check before
> submitting a patch.
I think the answer is probably "it's a feature, not a bug", but that
depends on your NFS mount options which you didn't give. I'd suggest
you read up on NFS soft versus hard mounts. I think you're seeing the
latter and expecting the former behavior.
The first hit I found Googling seems pretty decent, though taken from
Linux docs should still apply:
http://tldp.org/HOWTO/NFS-HOWTO/client.html
Under section 4.3.1 "Soft vs. Hard Mounting" there's a basic description.
Best of luck,
-Nathanael
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