Cowboy issue with kernel 5.16

kuon · January 24, 2022, 2:54am

I have a strange (low level) issue with Cowboy since I upgraded to kernel 5.16.

sendfile not working on linux 5.16

opened 12:25AM - 16 Jan 22 UTC

After upgrading to linux 5.16, static files in my phoenix app stopped being serv…ed. When I try to `curl` a file, I got the following error `curl: (18) transfer closed with 203 bytes remaining to read`. After some investigation, I found with strace the following error `sendfile(19, 22, [0], 203) = -1 EINVAL (Invalid argument)` Disabling sendfile in my phoenix app, with `protocol_options: [sendfile: false]` did fix the issue. I am not 100% sure the kernel upgrade is the cause, because I upgraded my whole box (archlinux) and more that just the kernel was upgraded. I am still investigating and I will update this issue with additional finding. **UPDATE 1**: I downgraded to 5.15.12 and rebooted, and the issue is gone, so now I am quite positive it is caused by kernel 5.16. **UPDATE 2**: issue is still present with kernel 5.16.2.

I am cross posting here because it could be an important one, and I think it deserves some more visibility.

To summarize, phoenix app does not serve static file anymore with kernel 5.16, and I traced it back to cowboy.

kuon · January 31, 2022, 8:27am

After investigations it seems to be caused by ZFS. Some regression with kernel 5.16. So if you have this combo, do not update to 5.16 yet.