tree 5b3a5b0830778f0bffaa97eee715f7a99ac3f01b
parent fbe363c476afe8ec992d3baf682670a4bd1b6ce6
author Roger Pau Monne <roger.pau@citrix.com> 1376304823 +0200
committer Jens Axboe <axboe@kernel.dk> 1383927027 -0700

xen-blkfront: improve aproximation of required grants per request

Improve the calculation of required grants to process a request by
using nr_phys_segments instead of always assuming a request is going
to use all posible segments.

nr_phys_segments contains the number of scatter-gather DMA addr+len
pairs, which is basically what we put at every granted page.
for_each_sg iterates over the DMA addr+len pairs and uses a grant
page for each of them.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>