6:19 a.m.
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(a)deltatee.com>
> Cc: Boris Ostrovsky <boris.ostrovsky(a)oracle.com>
> Cc: Juergen Gross <jgross(a)suse.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com>
> Cc: "Roger Pau Monné" <roger.pau(a)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