totemknet: retry knet_handle_new without privileged operations if it …

[ddstreet]

…fails

knet_handle_new can fail with ENAMETOOLONG if its privileged operations
fail, which can happen if we're running as a user process or in an
unprivileged container. Instead of failing to start, let's retry
without the privileged operations, which may result in a reduction in
performance, but at least it doesn't completely prevent us from starting.

Signed-off-by: Dan Streetman ddstreet@canonical.com

[knet-ci-bot]

Can one of the admins verify this patch?

[jfriesse]

@ddstreet Thank you for the PR. It is generally good but after brief talk with knet maintainer there was a bit worry about automatic fallback because of possible performance problems.

Would you mind to improve patch so it is using new key in cmap (something like system.allow_unpriviledged_knet_handle_fallback, ... you got the idea) which would be by default false/no but one can set it to yes (similarly as (for example) system.move_to_root_cgroup - you can just copy/paste the code) to get automatic fallback?

[jfriesse]

@knet-ci-bot ok to test

[ddstreet]

@ddstreet Thank you for the PR. It is generally good but after brief talk with knet maintainer there was a bit worry about automatic fallback because of possible performance problems.

Would you mind to improve patch so it is using new key in cmap (something like system.allow_unpriviledged_knet_handle_fallback, ... you got the idea) which would be by default false/no but one can set it to yes (similarly as (for example) system.move_to_root_cgroup - you can just copy/paste the code) to get automatic fallback?

I updated the commit, hopefully I got the cmap key addition correct; it did seem to test correctly for me.

I named it 'allow_knet_handle_fallback' as it's very easy to accidentally misspell 'unprivileged' so might cause confusion if it's in the param name.

Let me know if I can adjust anything else. Thanks!

[jfriesse]

@ddstreet Thank you for the update. I really like the name of the key, big thanks for the man page update (this is easily forgotten), loading of key is also correct. In general it looks really nice and I was unable find anything wrong during testing, so ACK and merged as a 4f171ea.

Regards,
Honza