+
+void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
+ unsigned int start, unsigned int nbytes, int out)
+{
+ struct scatter_walk walk;
+ unsigned int offset = 0;
+
+ if (!nbytes)
+ return;
+
+ for (;;) {
+ scatterwalk_start(&walk, sg);
+
+ if (start < offset + sg->length)
+ break;
+
+ offset += sg->length;
+ sg = scatterwalk_sg_next(sg);
+ }
+
+ scatterwalk_advance(&walk, start - offset);
+ scatterwalk_copychunks(buf, &walk, nbytes, out);
+ scatterwalk_done(&walk, out, 0);
+}
+EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);