Re: [PATCH v2] fs: replace the ki_complete two integer arguments with a single argument

[Jeff Moyer <jmoyer@redhat.com>]

Jens Axboe <axboe@kernel.dk> writes:

> On 10/21/21 12:05 PM, Jeff Moyer wrote:
>> 
>>>> I'll follow up if there are issues.
>> 
>> s390 (big endian, 64 bit) is failing libaio test 21:
>> 
>> # harness/cases/21.p
>> Expected -EAGAIN, got 4294967285
>> 
>> If I print out both res and res2 using %lx, you'll see what happened:
>> 
>> Expected -EAGAIN, got fffffff5,ffffffff
>> 
>> The sign extension is being split up.
>
> Funky, does it work if you apply this on top?
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 3674abc43788..c56437908339 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1442,8 +1442,8 @@ static void aio_complete_rw(struct kiocb *kiocb, u64 res)
>  	 * 32-bits of value at most for either value, bundle these up and
>  	 * pass them in one u64 value.
>  	 */
> -	iocb->ki_res.res = lower_32_bits(res);
> -	iocb->ki_res.res2 = upper_32_bits(res);
> +	iocb->ki_res.res = (long) (res & 0xffffffff);
> +	iocb->ki_res.res2 = (long) (res >> 32);
>  	iocb_put(iocb);
>  }

I think you'll also need to clamp any ki_complete() call sites to 32
bits (cast to int, or what have you).  Otherwise that sign extension
will spill over into res2.

fwiw, I tested with this:

	iocb->ki_res.res = (long)(int)lower_32_bits(res);
	iocb->ki_res.res2 = (long)(int)upper_32_bits(res);

Coupled with the call site changes, that made things work for me.

-Jeff