Re: umount -f implementation

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