Re: [PATCH 0/3] remove rw_page() from brd, pmem and btt

[Minchan Kim]

On Thu, Aug 03, 2017 at 10:05:44AM +0200, Christoph Hellwig wrote:
> FYI, for the read side we should use the on-stack bio unconditionally,
> as it will always be a win (or not show up at all).

Think about readahead. Unconditional on-stack bio to read around pages
with faulted address will cause latency peek. So, I want to use that
synchronous IO only if device says "Hey, I'm a synchronous".