Chuck Lever writes via Kernel.org Bugzilla:

(In reply to Bugspray Bot from comment #1)

Jeff Layton [off-list ref] writes:

On Tue, 2024-12-03 at 02:30 +0000, Li Lingfeng via Bugspray Bot wrote:

quoted

Li Lingfeng writes via Kernel.org Bugzilla:

We deployed the client and server on the same machine for some testing,

which

quoted

caused some processes to trigger hungtask.

Thanks for the report.

Note that this is really an unsupported configuration. It's very
difficult to prevent a situation where the server needs memory in order
to handle an RPC from the local client, and then tries to write back
dirty NFS client pages in order to get it. Instant deadlock.

That kind of configuration is fine for basic functionality testing, but
once you start getting into memory pressure, it can fall over pretty
quickly.

Historically, yes, this configuration is officially unsupported. We treat this configuration as best effort only because it is not possible to close all possible writeback deadlocks, as you said above.

However, Neil has mentioned that it is an important usage scenario for one or more of SuSE's customers. And, it is quite broadly deployed for automated testing.

This particular bug appears to be locking related, not writeback related. IMO, deeper investigation is warranted.

View: https://bugzilla.kernel.org/show_bug.cgi?id=219550#c2
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