Re: [PATCH 6/9] iomap: Convert read_count to byte count

[Darrick J. Wong]

On Tue, Aug 25, 2020 at 10:09:02AM +1000, Dave Chinner wrote:
> On Mon, Aug 24, 2020 at 03:55:07PM +0100, Matthew Wilcox (Oracle) wrote:
> > Instead of counting bio segments, count the number of bytes submitted.
> > This insulates us from the block layer's definition of what a 'same page'
> > is, which is not necessarily clear once THPs are involved.
> 
> I'd like to see a comment on the definition of struct iomap_page to
> indicate that read_count (and write count) reflect the byte count of
> IO currently in flight on the page, not an IO count, because THP
> makes tracking this via bio state hard. Otherwise it is not at all
> obvious why it is done and why it is intentional...

Agreed. :)

--D

> Otherwise the code looks OK.
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@xxxxxxxxxxxxx