Re: [dm-devel] [PATCH v3 06/26] block: Add bio_end_sector()

[Kent Overstreet <koverstreet google com>]

On Tue, Oct 02, 2012 at 02:10:01PM -0400, Vivek Goyal wrote:
> On Mon, Sep 24, 2012 at 03:34:46PM -0700, Kent Overstreet wrote:
> 
> [..]
> > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > index 4e32be1..d985e90 100644
> > --- a/include/linux/bio.h
> > +++ b/include/linux/bio.h
> > @@ -67,6 +67,7 @@
> >  #define bio_offset(bio)		bio_iovec((bio))->bv_offset
> >  #define bio_segments(bio)	((bio)->bi_vcnt - (bio)->bi_idx)
> >  #define bio_sectors(bio)	((bio)->bi_size >> 9)
> > +#define bio_end_sector(bio)	((bio)->bi_sector + bio_sectors(bio))
> 
> May be it is just me. But bio_end_sector() kind of sounds that it will
> calculate to the last sector of bio. So I thought of it more as
> bio_last_sector() and not the sector which is next to the last sector.
> 
> Will it make sense to introduce bio_last_sector() and use +1 everywhere.
> Or may be we need a better name. Can't think of one though.

Ugh, that sounds like it'd be just begging for fencepost errors. I've
never ran into a situation where I needed bio->bi_sector +
bio_sectors(bio) - 1, either.

I kind of see your point... it seems like there should be a name for
this concept (same as a pointer to the end of an array), but I can't
think of one.