+
+/*
+ * Copy up to size bytes between arg_buf and req based on the data direction
+ * described by the req. If an entire req's data cannot be transfered the
+ * req's is updated such that it's current index and bv offsets correctly
+ * reference any residual data which could not be copied. The return value
+ * is the number of bytes successfully copied to arg_buf.
+ */
+static int
+dmu_req_copy(void *arg_buf, int size, int *offset, struct request *req)
+{
+ struct bio_vec *bv;
+ struct req_iterator iter;
+ char *bv_buf;
+ int tocpy;
+
+ *offset = 0;
+ rq_for_each_segment(bv, req, iter) {
+
+ /* Fully consumed the passed arg_buf */
+ ASSERT3S(*offset, <=, size);
+ if (size == *offset)
+ break;
+
+ /* Skip fully consumed bv's */
+ if (bv->bv_len == 0)
+ continue;
+
+ tocpy = MIN(bv->bv_len, size - *offset);
+ ASSERT3S(tocpy, >=, 0);
+
+ bv_buf = page_address(bv->bv_page) + bv->bv_offset;
+ ASSERT3P(bv_buf, !=, NULL);
+
+ if (rq_data_dir(req) == WRITE)
+ memcpy(arg_buf + *offset, bv_buf, tocpy);
+ else
+ memcpy(bv_buf, arg_buf + *offset, tocpy);
+
+ *offset += tocpy;
+ bv->bv_offset += tocpy;
+ bv->bv_len -= tocpy;
+ }
+
+ return 0;
+}
+
+int
+dmu_read_req(objset_t *os, uint64_t object, struct request *req)
+{
+ uint64_t size = blk_rq_bytes(req);
+ uint64_t offset = blk_rq_pos(req) << 9;
+ dmu_buf_t **dbp;
+ int numbufs, i, err;
+
+ /*
+ * NB: we could do this block-at-a-time, but it's nice
+ * to be reading in parallel.
+ */
+ err = dmu_buf_hold_array(os, object, offset, size, TRUE, FTAG,
+ &numbufs, &dbp);
+ if (err)
+ return (err);
+
+ for (i = 0; i < numbufs; i++) {
+ int tocpy, didcpy, bufoff;
+ dmu_buf_t *db = dbp[i];
+
+ bufoff = offset - db->db_offset;
+ ASSERT3S(bufoff, >=, 0);
+
+ tocpy = (int)MIN(db->db_size - bufoff, size);
+ if (tocpy == 0)
+ break;
+
+ err = dmu_req_copy(db->db_data + bufoff, tocpy, &didcpy, req);
+
+ if (didcpy < tocpy)
+ err = EIO;
+
+ if (err)
+ break;
+
+ size -= tocpy;
+ offset += didcpy;
+ err = 0;
+ }
+ dmu_buf_rele_array(dbp, numbufs, FTAG);
+
+ return (err);
+}
+
+int
+dmu_write_req(objset_t *os, uint64_t object, struct request *req, dmu_tx_t *tx)
+{
+ uint64_t size = blk_rq_bytes(req);
+ uint64_t offset = blk_rq_pos(req) << 9;
+ dmu_buf_t **dbp;
+ int numbufs;
+ int err = 0;
+ int i;
+
+ if (size == 0)
+ return (0);
+
+ err = dmu_buf_hold_array(os, object, offset, size, FALSE, FTAG,
+ &numbufs, &dbp);
+ if (err)
+ return (err);
+
+ for (i = 0; i < numbufs; i++) {
+ int tocpy, didcpy, bufoff;
+ dmu_buf_t *db = dbp[i];
+
+ bufoff = offset - db->db_offset;
+ ASSERT3S(bufoff, >=, 0);
+
+ tocpy = (int)MIN(db->db_size - bufoff, size);
+ if (tocpy == 0)
+ break;
+
+ ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
+
+ if (tocpy == db->db_size)
+ dmu_buf_will_fill(db, tx);
+ else
+ dmu_buf_will_dirty(db, tx);
+
+ err = dmu_req_copy(db->db_data + bufoff, tocpy, &didcpy, req);
+
+ if (tocpy == db->db_size)
+ dmu_buf_fill_done(db, tx);
+
+ if (didcpy < tocpy)
+ err = EIO;
+
+ if (err)
+ break;
+
+ size -= tocpy;
+ offset += didcpy;
+ err = 0;
+ }
+
+ dmu_buf_rele_array(dbp, numbufs, FTAG);
+ return (err);
+}
+