+static int __blk_rq_unmap_user(struct bio *bio)
+{
+ int ret = 0;
+
+ if (bio) {
+ if (bio_flagged(bio, BIO_USER_MAPPED))
+ bio_unmap_user(bio);
+ else
+ ret = bio_uncopy_user(bio);
+ }
+
+ return ret;
+}
+
+static int __blk_rq_map_user(request_queue_t *q, struct request *rq,
+ void __user *ubuf, unsigned int len)
+{
+ unsigned long uaddr;
+ struct bio *bio, *orig_bio;
+ int reading, ret;
+
+ reading = rq_data_dir(rq) == READ;
+
+ /*
+ * if alignment requirement is satisfied, map in user pages for
+ * direct dma. else, set up kernel bounce buffers
+ */
+ uaddr = (unsigned long) ubuf;
+ if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
+ bio = bio_map_user(q, NULL, uaddr, len, reading);
+ else
+ bio = bio_copy_user(q, uaddr, len, reading);
+
+ if (IS_ERR(bio)) {
+ return PTR_ERR(bio);
+ }
+
+ orig_bio = bio;
+ blk_queue_bounce(q, &bio);
+ /*
+ * We link the bounce buffer in and could have to traverse it
+ * later so we have to get a ref to prevent it from being freed
+ */
+ bio_get(bio);
+
+ /*
+ * for most (all? don't know of any) queues we could
+ * skip grabbing the queue lock here. only drivers with
+ * funky private ->back_merge_fn() function could be
+ * problematic.
+ */
+ spin_lock_irq(q->queue_lock);
+ if (!rq->bio)
+ blk_rq_bio_prep(q, rq, bio);
+ else if (!q->back_merge_fn(q, rq, bio)) {
+ ret = -EINVAL;
+ spin_unlock_irq(q->queue_lock);
+ goto unmap_bio;
+ } else {
+ rq->biotail->bi_next = bio;
+ rq->biotail = bio;
+
+ rq->nr_sectors += bio_sectors(bio);
+ rq->hard_nr_sectors = rq->nr_sectors;
+ rq->data_len += bio->bi_size;
+ }
+ spin_unlock_irq(q->queue_lock);
+
+ return bio->bi_size;
+
+unmap_bio:
+ /* if it was boucned we must call the end io function */
+ bio_endio(bio, bio->bi_size, 0);
+ __blk_rq_unmap_user(orig_bio);
+ bio_put(bio);
+ return ret;
+}
+