[SCSI] block: fix the partial mappings with struct rq_map_data

This fixes bio_copy_user_iov to properly handle the partial mappings
with struct rq_map_data (which only sg uses for now but st and osst
will shortly). It adds the offset member to struct rq_map_data and
changes blk_rq_map_user to update it so that bio_copy_user_iov can add
an appropriate page frame via bio_add_pc_page().

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/block/blk-map.c b/block/blk-map.c
index 2990447f45e9..c7e55b23a2bc 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -150,6 +150,9 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
                         bio = rq->bio;
                 bytes_read += ret;
                 ubuf += ret;
+
+                if (map_data)
+                        map_data->offset += ret;
         }
 
         if (!bio_flagged(bio, BIO_USER_MAPPED))