Correct handling of errors returned from io_uring_submit()

[iboukris]

Hi, this is a theoretical question to design the code properly.

What are the possible errors returned from io_uring_submit() and how to handle them? The example code either does not check the return value or expects all the enqueued SQE to be submitted, while the man page isn't too meticulous either and only says that it returns -errno on failure.

It looks like there are three kind of possible errors, when it returns less than the number of submitted SQE, when it returns -EAGAIN or -EINTR and when it returns any other error. Can any of these be a fatal error (like bad configuration or wrong code)? Otherwise, in case of an ephemeral error, is the only way to handle it is to try and call it again?

Assuming I only submit one SQE by one, can the io_uring_get_sqe() be undone in case io_uring_submit() returns an error, in order to clear up the ring for potentially more important operations for instance?

[P.S. not using SQPOLL]

Thanks!

[iboukris]

In a closer look, it seems the possible returned errors roughly correspond to the ones returned by the io_uring_enter (2) system call, which are documented in its man page, except perhaps for the ones related to IORING_ENTER_GETEVENTS. Any confirmation / clarifications would be great.