Some new bio merging behaviors in __bio_try_merge_page

[Christoph Hellwig]

On Thu, Apr 11, 2019 at 04:09:54PM +0800, Ming Lei wrote:
> I don't think it is a good behaviour to use bio->bi_max_vecs to limit
> max allowed page, you may see the idea from the naming simply...
> 
> If there were other such drivers, we may fix it easily, and the following
> patch should fix your issue:

Yep.  Consumers of the block layer really have no business at all
looking at bi_vcnt.