On Sun, Jan 25, 2026 at 11:28 PM Ming Lei <[email protected]> wrote:
>
...
> >
> > Fedora 43 default config with some debugging options enabled, but no
> > changes in schedulers.
> > Test VM storage is on a networked NAS over iSCSI - both boxes VM host and
> > NAS have two NICs,
> > I get the errors when I load the network. So I believe the requests really
> > complete out of
> > order due to the network in my case. All tests that have the bpftrace check
> > fail on occasion.
>
> Can you test the following patch and see if re-order still can happen?
>
>
> diff --git a/tools/testing/selftests/ublk/test_generic_01.sh
> b/tools/testing/selftests/ublk/test_generic_01.sh
> index 26cf3c7ceeb5..26d5e52ece29 100755
> --- a/tools/testing/selftests/ublk/test_generic_01.sh
> +++ b/tools/testing/selftests/ublk/test_generic_01.sh
> @@ -13,7 +13,7 @@ if ! _have_program fio; then
> exit "$UBLK_SKIP_CODE"
> fi
>
> -_prep_test "null" "sequential io order"
> +_prep_test "null" "ublk dispatch won't reorder IO"
>
> dev_id=$(_add_ublk_dev -t null)
> _check_add_dev $TID $?
> @@ -39,9 +39,13 @@ fio --name=write_seq \
> ERR_CODE=$?
> kill "$btrace_pid"
> wait
> -if grep -q "io_out_of_order" "$UBLK_TMP"; then
> - cat "$UBLK_TMP"
> +
> +# Check for out-of-order completions detected by bpftrace
> +if grep -q "^out_of_order:" "$UBLK_TMP"; then
> + echo "I/O reordering detected:"
> + grep "^out_of_order:" "$UBLK_TMP"
> ERR_CODE=255
> fi
> +
> _cleanup_test "null"
> _show_result $TID $ERR_CODE
> diff --git a/tools/testing/selftests/ublk/trace/seq_io.bt
> b/tools/testing/selftests/ublk/trace/seq_io.bt
> index b2f60a92b118..60ac40e66606 100644
> --- a/tools/testing/selftests/ublk/trace/seq_io.bt
> +++ b/tools/testing/selftests/ublk/trace/seq_io.bt
> @@ -2,23 +2,45 @@
> $1: dev_t
> $2: RWBS
> $3: strlen($2)
> +
> + Track request order between block_io_start and block_rq_complete.
> + For each request, record its start sequence number and verify
> + completions happen in the same order.
> */
> +
> BEGIN {
> - @last_rw[$1, str($2)] = (uint64)0;
> + @start_seq = (uint64)0;
> + @complete_seq = (uint64)0;
> + @out_of_order = (uint64)0;
> +}
> +
> +tracepoint:block:block_io_start
> +{
> + if ((int64)args.dev == $1 && !strncmp(args.rwbs, str($2), $3)) {
> + @start_order[args.sector] = @start_seq;
> + @start_seq = @start_seq + 1;
> + }
> }
> +
> tracepoint:block:block_rq_complete
> {
> - $dev = $1;
> if ((int64)args.dev == $1 && !strncmp(args.rwbs, str($2), $3)) {
> - $last = @last_rw[$dev, str($2)];
> - if ((uint64)args.sector != $last) {
> - printf("io_out_of_order: exp %llu actual %llu\n",
> - args.sector, $last);
> + $expected_order = @start_order[args.sector];
> + if ($expected_order != @complete_seq) {
> + printf("out_of_order: sector %llu started at seq %llu
> but completed at seq %llu\n",
> + args.sector, $expected_order, @complete_seq);
> + @out_of_order = @out_of_order + 1;
> }
> - @last_rw[$dev, str($2)] = (args.sector + args.nr_sector);
> + delete(@start_order[args.sector]);
> + @complete_seq = @complete_seq + 1;
> }
> }
>
> END {
> - clear(@last_rw);
> + printf("total_start: %llu total_complete: %llu out_of_order: %llu\n",
> + @start_seq, @complete_seq, @out_of_order);
> + clear(@start_order);
> + clear(@start_seq);
> + clear(@complete_seq);
> + clear(@out_of_order);
> }
Forget another change, please apply the following delta too:
@@ -28,8 +28,8 @@ if ! kill -0 "$btrace_pid" > /dev/null 2>&1; then
exit "$UBLK_SKIP_CODE"
fi
-# run fio over this ublk disk
-fio --name=write_seq \
+# run fio over this ublk disk (pinned to CPU 0)
+taskset -c 0 fio --name=write_seq \
Thanks,
