Re: [PATCH 2/2] iomap: remove the atomic write length check in iomap_dio_bio_iter_one()

[John Garry <john.garry@linux.dev>]

On 11/9/26 22:46, Tal Zussman wrote:
>>> What specifically would you want to see tested? I can do an atomic write with
>>> a partially unmapped buffer, with and without stable writes, and check that it
>>> fails and that nothing is written.
>> Just something similar to the blktests case which you added.
>>
> Sounds good, I'll add it to the queue.

Thanks

> 
>> BTW, have you tested this partially-unmapped case for CoW-based atomics
>> on xfs? You can just do that by setting atomic_wr=0
>>
> Yeah, I just tested it. It behaves as expected: returns -EFAULT with the file
> unchanged, both with and without bouncing.
> 
> The single-bio check depends on REQ_ATOMIC, which only the HW atomic path sets,
> so it doesn't apply to CoW writes, both before and after this series.
> 
> In terms of consistency, the unmapped buffer returns -EINVAL on the non-bounce
> HW path (from bio_iov_iter_get_pages()) but -EFAULT for all other paths. That
> should probably be made consistent across HW and SW and bounce vs. non-bounce,
> but that's a separate change.

Yeah, we should fail for the same reason on HW- and CoW-based atomics. I 
would like if any such rules could be documented and we ensure that both 
HW- and CoW-based atomics always fail for non-adherence to the rules.

cheers