Re: [PATCH v2 1/1] iomap: propagate nowait to block layer

[Christoph Hellwig <hch@infradead.org>]

On Tue, Mar 04, 2025 at 08:35:52PM +0000, Pavel Begunkov wrote:
> Clarification: the mentioned work was reverted or pulled out _upstream_,
> it wasn't about back porting.

I don't think we ever tried synchronous reporting of wouldblock errors,
but maybe i'm just too old and confused by now.

> lines. And Christoph even of confirmed that the main check in the patch
> does what's intended,

I absolutely did not.

> Another option is to push all io_uring filesystem / iomap requests
> to the slow path (where blocking is possible) and have a meaningful
> perf regression for those who still use fs+io_uring direct IO. And
> I don't put any dramaticism into it, it's essentially what users
> who detect the problem already do, either that but from the user
> space or disabling io_uring all together.

If you don't want to do synchronous wouldblock errors that's your
only option.  I think it would suck badly, but it's certainly easier
to backport.