/*
	$1: 	dev_t
	$2: 	RWBS
	$3:     strlen($2)

	Track request order between block_io_start and block_rq_complete.
	Sequence starts at 1 so 0 means "never seen". On first valid
	completion, sync complete_seq to handle probe attachment races.
	block_rq_complete listed first to reduce missed completion window.
*/

BEGIN {
	@start_seq = (uint64)1;
	@complete_seq = (uint64)0;
	@out_of_order = (uint64)0;
	@start_order[0] = (uint64)0;
	delete(@start_order[0]);
	printf("BPFTRACE_READY\n");
}

tracepoint:block:block_rq_complete
/(int64)args.dev == $1 && !strncmp(args.rwbs, str($2), $3)/
{
	$expected = @start_order[args.sector];
	if ($expected > 0) {
		if (@complete_seq == 0) {
			@complete_seq = $expected;
		}
		if ($expected != @complete_seq) {
			printf("out_of_order: sector %llu started at seq %llu but completed at seq %llu\n",
				args.sector, $expected, @complete_seq);
			@out_of_order = @out_of_order + 1;
		}
		delete(@start_order[args.sector]);
		@complete_seq = @complete_seq + 1;
	}
}

tracepoint:block:block_io_start
/(int64)args.dev == $1 && !strncmp(args.rwbs, str($2), $3)/
{
	@start_order[args.sector] = @start_seq;
	@start_seq = @start_seq + 1;
}

END {
	printf("total_start: %llu total_complete: %llu out_of_order: %llu\n",
		@start_seq - 1, @complete_seq, @out_of_order);
	clear(@start_order);
	clear(@start_seq);
	clear(@complete_seq);
	clear(@out_of_order);
}