On 24/03/2021 08:11, Christoph Hellwig wrote:
> On Wed, Mar 24, 2021 at 07:07:27AM +0000, Johannes Thumshirn wrote:
>>>> if (iov_iter_is_bvec(iter)) {
>>>> - if (WARN_ON_ONCE(bio_op(bio) == REQ_OP_ZONE_APPEND))
>>>> - return -EINVAL;
>>>> + if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
>>>> + struct request_queue *q = bio->bi_bdev->bd_disk->queue;
>>>> + unsigned int max_append =
>>>> + queue_max_zone_append_sectors(q) << 9;
>>>> +
>>>> + if (WARN_ON_ONCE(iter->count > max_append))
>>>> + return -EINVAL;
>>>> + }
>>>
>>> That is not correct. bio_iov_iter_get_pages just fills the bio as far
>>> as we can, and then returns 0 for the next call to continue. Basically
>>> what you want here is a partial version of bio_iov_bvec_set.
>>>
>>
>> Isn't that what I did? The above is checking if we have REQ_OP_ZONE_APPEND and
>> then returns EINVAL if iter->count is bigger than queue_max_zone_append_sectors().
>> If the check doesn't fail, its going to call bio_iov_bvec_set().
>
> And that is the problem. It should not fail, the payload is decoupled
> from the max_append size.
>
> Doing the proper thing is not too hard as described above - make sure
> the bi_iter points to only the chunk of iter passed in that fits, and
> only advance the passed in iter by that amount.
>
Ah got it now,
thanks
