For many reasons, forcibly unmounting a soft NFS mount could hang forever.
Here are the fixes:
- Introduce decents timeouts in operation that awaited NFS server reply.
- On timeout, fails operations on soft mounts with EIO.
- Introduce NFSMNT_DISMNTFORCE to let the filesystem know that a
force unmount is ongoing. This causes timeouts to be reduced and
prevents the NFS client to attempt reconnecting to the NFS server.
Also fix a race condition where some asynchronous I/O could reference
destroyed mount structures. We fix this by awaiting asynchronous I/O
to drain before proceeding.
Reviewed by Chuck Silvers.
conditional content depending on if the NFS client is wanted or
not. The server can now be made an independent module not depending
on the nfs client.
Tested with rump_nfs (standalone client), rump_nfsd (standalone
nfsd) and a qemu installation with both the client and the server.
