On 26/04/17 01:37 AM, Roger Pau Monné wrote:
On Tue, Apr 25, 2017 at 12:21:02PM -0600, Logan Gunthorpe wrote:
Straightforward conversion to the new helper, except due to the lack of error path, we have to use SG_MAP_MUST_NOT_FAIL which may BUG_ON in certain cases in the future.
Signed-off-by: Logan Gunthorpe logang@deltatee.com Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Juergen Gross jgross@suse.com Cc: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Cc: "Roger Pau Monné" roger.pau@citrix.com
drivers/block/xen-blkfront.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 3945963..ed62175 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -816,8 +816,9 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri BUG_ON(sg->offset + sg->length > PAGE_SIZE);
if (setup.need_copy) {
setup.bvec_off = sg->offset;setup.bvec_data = kmap_atomic(sg_page(sg));
setup.bvec_off = 0;setup.bvec_data = sg_map(sg, 0, SG_KMAP_ATOMIC |SG_MAP_MUST_NOT_FAIL);I assume that sg_map already adds sg->offset to the address?
Correct.
Also wondering whether we can get rid of bvec_off and just increment bvec_data, adding Julien who IIRC added this code.
bvec_off is used to keep track of the offset within the current mapping so it's not a great idea given that you'd want to kunmap_atomic the original address and not something with an offset. It would be nice if this could be converted to use the sg_miter interface but that's a much more invasive change that would require someone who knows this code and can properly test it. I'd be very grateful if someone actually took that on.
Logan