Re: NFS server regression in kernel 5.13 (tested w/ 5.13.9)

I appreciate that Chuck. It was not my intention to seek basic "user"
support, but as I don't know the intricacies of how nfs works in the
kernel, I don't know where to get the right information to share to
help with the diagnostic effort. I have read through the
troubleshooting recommendations on the linux-nfs wiki, but the issue
is beyond what is indicated there, and my setup has been running
without any NFS issues for years at this point, and I can demonstrate
the error merely by changing the booted kernel, so I feel confident
it's not a simple configuration error.

I have raised an issue on the ArchLinux bug tracker as well
(https://bugs.archlinux.org/task/71775). Given that the ArchLinux
version of the kernel has minimal delta from mainline, (I've checked
and no fs/rpc/nfs files are changed in 7 file delta vs mainline), it's
been my previous experience that they will refer me to the kernel
subsystem mailing list, but I will wait to hear back from them, and
see what they say.

- mike


- mike









On Sun, Aug 8, 2021 at 3:47 PM Chuck Lever III [off-list ref] wrote:

quoted

On Aug 8, 2021, at 6:37 PM, Mike Javorski [off-list ref] wrote:

I have been experiencing nfs file access hangs with multiple release
versions of the 5.13.x linux kernel. In each case, all file transfers
freeze for 5-10 seconds and then resume. This seems worse when reading
through many files sequentially.

My server:
- Archlinux w/ a distribution provided kernel package
- filesystems exported with "rw,sync,no_subtree_check,insecure" options

Client:
- Archlinux w/ latest distribution provided kernel (5.13.9-arch1-1 at writing)
- nfs mounted via /net autofs with "soft,nodev,nosuid" options
(ver=4.2 is indicated in mount)

I have tried the 5.13.x kernel several times since the first arch
release (most recently with 5.13.9-arch1-1), all with similar results.
Each time, I am forced to downgrade the linux package to a 5.12.x
kernel (5.12.15-arch1 as of writing) to clear up the transfer issues
and stabilize performance. No other changes are made between tests. I
have confirmed the freezing behavior using both ext4 and btrfs
filesystems exported from this server.

At this point I would appreciate some guidance in what to provide in
order to diagnose and resolve this issue. I don't have a lot of kernel
debugging experience, so instruction would be helpful.

Hi Mike-

Thanks for the report.

Since you are using a distribution kernel and don't have much
kernel debugging experience, we typically ask you to work with
your distributor first. linux-nfs@ is a developer's mailing
list, we're not really prepared to provide user support.

When you report the problem to Arch, you might want to have
a description of your workload (especially if you can
reproduce the problem often with a particular application
or user activity), and maybe be prepared to capture a network
trace of the failure using tcpdump.


--
Chuck Lever