linux-kernel - Re: [PATCH 6/6] io_uring: allow NOP opcode in IOPOLL mode

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Date:   Fri, 22 Apr 2022 09:58:29 +0000
From:   Dylan Yudaken <dylany@...com>
To:     "axboe@...nel.dk" <axboe@...nel.dk>
CC:     Kernel Team <Kernel-team@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
        "asml.silence@...il.com" <asml.silence@...il.com>
Subject: Re: [PATCH 6/6] io_uring: allow NOP opcode in IOPOLL mode

On Thu, 2022-04-21 at 17:33 -0600, Jens Axboe wrote:
> On Thu, Apr 21, 2022 at 3:17 AM Dylan Yudaken <dylany@...com> wrote:
> > 
> > This is useful for tests so that IOPOLL can be tested without
> > requiring
> > files. NOP is acceptable in IOPOLL as it always completes
> > immediately.
> 
> This one actually breaks two liburing test cases (link and defer)
> that
> assume NOP on IOPOLL will return -EINVAL. Not a huge deal, but we do
> need to figure out how to make them reliably -EINVAL in a different
> way then.
> 
> Maybe add a nop_flags to the usual flags spot in the sqe, and define
> a flag that says NOP_IOPOLL or something. Require this flag set for
> allowing NOP on iopoll. That'd allow testing, but still retain the
> -EINVAL behavior if not set.
> 
> Alternatively, modify test cases...
> 
> I'll drop this one for now, just because it fails the regression
> tests.
> 

That's fine - sorry I didn't notice that. I think fixing the tests is
the better approach here. It should be easy to get an -EINVAL from it.