+ /* Convenient aliases */
+ unsigned int grant_idx = setup->grant_idx;
+ struct blkif_request *ring_req = setup->ring_req;
+ struct blkfront_info *info = setup->info;
+ struct blk_shadow *shadow = &info->shadow[setup->id];
+
+ if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
+ (grant_idx % GRANTS_PER_INDIRECT_FRAME == 0)) {
+ if (setup->segments)
+ kunmap_atomic(setup->segments);
+
+ n = grant_idx / GRANTS_PER_INDIRECT_FRAME;
+ gnt_list_entry = get_indirect_grant(&setup->gref_head, info);
+ shadow->indirect_grants[n] = gnt_list_entry;
+ setup->segments = kmap_atomic(gnt_list_entry->page);
+ ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
+ }
+
+ gnt_list_entry = get_grant(&setup->gref_head, gfn, info);
+ ref = gnt_list_entry->gref;
+ shadow->grants_used[grant_idx] = gnt_list_entry;
+
+ if (setup->need_copy) {
+ void *shared_data;
+
+ shared_data = kmap_atomic(gnt_list_entry->page);
+ /*
+ * this does not wipe data stored outside the
+ * range sg->offset..sg->offset+sg->length.
+ * Therefore, blkback *could* see data from
+ * previous requests. This is OK as long as
+ * persistent grants are shared with just one
+ * domain. It may need refactoring if this
+ * changes
+ */
+ memcpy(shared_data + offset,
+ setup->bvec_data + setup->bvec_off,
+ len);
+
+ kunmap_atomic(shared_data);
+ setup->bvec_off += len;
+ }
+
+ fsect = offset >> 9;
+ lsect = fsect + (len >> 9) - 1;
+ if (ring_req->operation != BLKIF_OP_INDIRECT) {
+ ring_req->u.rw.seg[grant_idx] =
+ (struct blkif_request_segment) {
+ .gref = ref,
+ .first_sect = fsect,
+ .last_sect = lsect };
+ } else {
+ setup->segments[grant_idx % GRANTS_PER_INDIRECT_FRAME] =
+ (struct blkif_request_segment) {
+ .gref = ref,
+ .first_sect = fsect,
+ .last_sect = lsect };
+ }
+
+ (setup->grant_idx)++;
+}
+
+static int blkif_queue_rw_req(struct request *req)
+{
+ struct blkfront_info *info = req->rq_disk->private_data;
+ struct blkif_request *ring_req;
+ unsigned long id;
+ int i;
+ struct setup_rw_req setup = {
+ .grant_idx = 0,
+ .segments = NULL,
+ .info = info,
+ .need_copy = rq_data_dir(req) && info->feature_persistent,
+ };