On Thu, May 09, 2019 at 07:24:12PM +0800, Ming Lei wrote: > I'd suggest to fix block layer instead of working around the issue here, > then any driver may benefit from the fix.
That is my plan, and I started on it. But the fix isn't trivial, and will probably take a while and be invasive. > Especially checking bio->bi_vcnt is just a hack, and drivers should > never use .bi_vcnt. That is why it is explicitly commented as a hack. But a good enough one to still speed up typical 4K I/Os - one a bio has been cloned chances are very high we don't care about the fast path any more.
