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From:   Mike Javorski <mike.javorski@gmail.com>
Date:   Sun, 8 Aug 2021 15:37:48 -0700
Message-ID: <CAOv1SKCmdtchm5Z2NU80o49tkrHpAkPFaHKj4-vLDN5bZNCz-Q@mail.gmail.com>
Subject: NFS server regression in kernel 5.13 (tested w/ 5.13.9)
To:     linux-nfs@vger.kernel.org
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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.

- mike