static void do_io()

in drivers/ubd_kern.c [1477:1547]

• 62 lines of code
• 16 McCabe index (conditional complexity)

static void do_io(struct io_thread_req *req, struct io_desc *desc)
{
	char *buf = NULL;
	unsigned long len;
	int n, nsectors, start, end, bit;
	__u64 off;

	/* FLUSH is really a special case, we cannot "case" it with others */

	if (req_op(req->req) == REQ_OP_FLUSH) {
		/* fds[0] is always either the rw image or our cow file */
		req->error = map_error(-os_sync_file(req->fds[0]));
		return;
	}

	nsectors = desc->length / req->sectorsize;
	start = 0;
	do {
		bit = ubd_test_bit(start, (unsigned char *) &desc->sector_mask);
		end = start;
		while((end < nsectors) &&
		      (ubd_test_bit(end, (unsigned char *) &desc->sector_mask) == bit))
			end++;

		off = req->offset + req->offsets[bit] +
			start * req->sectorsize;
		len = (end - start) * req->sectorsize;
		if (desc->buffer != NULL)
			buf = &desc->buffer[start * req->sectorsize];

		switch (req_op(req->req)) {
		case REQ_OP_READ:
			n = 0;
			do {
				buf = &buf[n];
				len -= n;
				n = os_pread_file(req->fds[bit], buf, len, off);
				if (n < 0) {
					req->error = map_error(-n);
					return;
				}
			} while((n < len) && (n != 0));
			if (n < len) memset(&buf[n], 0, len - n);
			break;
		case REQ_OP_WRITE:
			n = os_pwrite_file(req->fds[bit], buf, len, off);
			if(n != len){
				req->error = map_error(-n);
				return;
			}
			break;
		case REQ_OP_DISCARD:
		case REQ_OP_WRITE_ZEROES:
			n = os_falloc_punch(req->fds[bit], off, len);
			if (n) {
				req->error = map_error(-n);
				return;
			}
			break;
		default:
			WARN_ON_ONCE(1);
			req->error = BLK_STS_NOTSUPP;
			return;
		}

		start = end;
	} while(start < nsectors);

	req->offset += len;
	req->error = update_bitmap(req, desc);
}