Wednesday Oct 08, 2008

Not able to mount from Fedora Core 9

Helen Chao, a colleague who had never really used Linux, asked me to help configure a kernel. I asked why and she said she needed to test RDMA over NFSv4. It turns out that the stock 2.6.25 kernel with Fedora Core 9 already had the support in it. We followed the directions at the nfs-rdma.txt and were not able to get it running.

Helen (a great test engineer) proceeded to investigate from there and couldn't get a simple loopback or NFS mount to succeed.

So I exported the root to all hosts and went to work debugging this issue. A 'rpcinfo -p' on the server showed the expected registered services. The same call from a client failed, but a ping worked:

[th199096@jhereg ~]> rpcinfo -p pnfs-9-30
\^C
[th199096@jhereg ~]> rpcinfo -p pnfs-9-30
\^C
[th199096@jhereg ~]> sudo mount -o vers=3 pnfs-9-30:/ /mnt
\^C
[th199096@jhereg ~]> sudo mount -o vers=3 pnfs-9-30:/ /mnt
nfs mount: pnfs-9-30: : RPC: Rpcbind failure - RPC: Timed out
nfs mount: retrying: /mnt
nfs mount: pnfs-9-30: : RPC: Rpcbind failure - RPC: Timed out
\^C
[th199096@jhereg ~]> ping pnfs-9-30
pnfs-9-30 is alive

I thought that perhaps it was a firewall issue and disabled IPTABLES.

No luck and I knew the mount should succeed - I tried it with my home Core 8 box and an OpenSolaris server. It worked, but then again, that Linux box has been configured for ages. Long story short, I asked Chuck Lever for help.

His only suggestion was to turn off selinux or as he puts it:

Also disable selinux, just so your systems behave like normal Unix.

So I followed the directions I found here: How to Disable SELinux and now the mount works:

# mount -o vers=3 pnfs-9-30:/ /mnt
nfs mount: pnfs-9-30: : RPC: Rpcbind failure - RPC: Timed out
nfs mount: retrying: /mnt
nfs mount: pnfs-9-30: : RPC: Rpcbind failure - RPC: Timed out
nfs mount: pnfs-9-30: : RPC: Rpcbind failure - RPC: Timed out
nfs mount: /mnt: mounted OK
# 

Most of the help I found with google on the RPC messages wasn't informative. Either the suggestion was to turn off IPTABLES or there was no reply.


Originally posted on Kool Aid Served Daily
Copyright (C) 2008, Kool Aid Served Daily

Wednesday Oct 01, 2008

One code review out, another to come shortly

I just put a code review request out for 6751438 mirror mounted mountpoints panic when umounted on nfs-discuss (see [nfs-discuss] Code reviewers wanted for 6751438 mirror mounted mountpoints panic when umounted ).

The hardest part was finding time to test. This resulted from a fix made a couple of months ago. And at that time, both unit and mini-PIT testing showed no panics. And now the mirrormount test suite inside mini-PIT could reliably trigger a panic. Luckily, I understand what the bug is and the panics have stopped.

I'm also about to ask for a code review for 6738223 Can not share a single IP address, which is quite simple to fix and we probably never would have fixed it except for:

  1. I saw someone copying it over to the CIFS code.
  2. We've had a couple of people ask about it on nfs-discuss at OpenSolaris.

The basic issue is that you can not share to a single IP without explicitly mentioning a netmask. I go on about it in these old blog entries: [Open]Solaris and sharing subnets and single machines and Checking a host entry - some code analysis.

The fix is easier than the testing, but I'll do that in the morning after a fresh build and ask for the code review later in the day.


Originally posted on Kool Aid Served Daily
Copyright (C) 2008, Kool Aid Served Daily
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