Re: [PATCH v2 1/3] xfs: use b_maps[] for discontiguous buffers

[Mark Tinguely <tinguely@xxxxxxx>]

On 11/30/12 10:09, Christoph Hellwig wrote:
> >   use_alloc_page:
> > -       start = BBTOB(bp->b_map.bm_bn)>>  PAGE_SHIFT;
> > -       end = (BBTOB(bp->b_map.bm_bn + bp->b_length) + PAGE_SIZE - 1)
> > +       start = BBTOB(bp->b_maps[0].bm_bn)>>  PAGE_SHIFT;
> > +       end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
> Btw, how is this logic supposed to work for discontiguous buffers?
>
> Each of them might straddle boundaries individually, so doing the
> start/end calculation for the number of pages isn't going to be correct.
eeek. yep, I will loop through and count the pages needed in each
segment.

--Mark.