Re: One more bio for for floppy users in 2.5.33..

[Jens Axboe <axboe@suse.de>]

On Thu, Sep 05 2002, Linus Torvalds wrote:
> > OK.  But still, I don't see why we need partial BIO completions.  If
> > we say that the basic unit of completion is a whole BIO, then readahead
> > can then manage latency via the outgoing bio size.
> 
> But that's horrible. The floppy driver can take huge bio's no problem, and 
> limiting bio sizes to track sizes would be a huge pain in the driver for 
> no good reason. In fact, it would be pretty much impossible, since the 
> tracks aren't even page-aligned.
> 
> So limiting bio's fundamentally _cannot_ do the right thing. While adding
> two lines of code _can_.

I agree that partial completions are the right thing to do here, and in
fact this is how the interface was originally remember?

However, I don't see how this is a two-liner change. Basically you are
changing bi_end_io() from a completion to partial completion invokation,
which requires changing (and complicating) all of them. Just adding
a sector count to bio_endio() does not enable that to partially complete
some pages. What am I missing?

Jens