Re: [PATCH 1/3] io_uring/rw: fix short rw error handling

[Jens Axboe <axboe@kernel.dk>]

On 9/19/22 2:17 PM, Avadhut Naik wrote:
> From: Pavel Begunkov <asml.silence@gmail.com>
> 
> We have a couple of problems, first reports of unexpected link breakage
> for reads when cqe->res indicates that the IO was done in full. The
> reason here is partial IO with retries.
> 
> TL;DR; we compare the result in __io_complete_rw_common() against
> req->cqe.res, but req->cqe.res doesn't store the full length but rather
> the length left to be done. So, when we pass the full corrected result
> via kiocb_done() -> __io_complete_rw_common(), it fails.
> 
> The second problem is that we don't try to correct res in
> io_complete_rw(), which, for instance, might be a problem for O_DIRECT
> but when a prefix of data was cached in the page cache. We also
> definitely don't want to pass a corrected result into io_rw_done().
> 
> The fix here is to leave __io_complete_rw_common() alone, always pass
> not corrected result into it and fix it up as the last step just before
> actually finishing the I/O.

I'm confused by this email, why is it being sent? And what are the 2-3/3
patches?

And while this one should certainly go to stable, also note that:

commit 62bb0647b14646fa6c9aa25ecdf67ad18f13523c
Author: Pavel Begunkov <asml.silence@gmail.com>
Date:   Tue Sep 13 13:21:23 2022 +0100

    io_uring/rw: fix error'ed retry return values

exists in Linus's tree and should go in alongside the parent as it
fixes the parameter type.

-- 
Jens Axboe