block/017 fails because systemd tries to read it

[gurugio]

Hi,

block/017 always fails on my test machine.

gkim@ib1:~/pb-ltp/blktests$ sudo ./check block/017
block/017 (do I/O and check the inflight counter)            [failed]
    runtime  58.937s  ...  58.952s
    --- tests/block/017.out	2018-10-26 00:39:35.516915128 +0200
    +++ /home/gkim/pb-ltp/blktests/results/nodev/block/017.out.bad	2019-04-02 11:08:55.659410586 +0200
    @@ -7,8 +7,8 @@
     sysfs inflight writes 1
     sysfs stat 2
     diskstats 2
    -sysfs inflight reads 0
    +sysfs inflight reads 1
     sysfs inflight writes 0
    -sysfs stat 0
    ...
    (Run 'diff -u tests/block/017.out /home/gkim/pb-ltp/blktests/results/nodev/block/017.out.bad' to see the entire diff)

I found out that systemd-udevd read it when /dev/nullb0 is created and it increased read-inflight count. Do you have any idea to solve it?

gkim@ib1:~/pb-ltp/blktests$ sudo modprobe null_blk queue_mode=2 irqmode=2 completion_nsec=5000000000
[sudo] password for gkim: 
gkim@ib1:~/pb-ltp/blktests$ ls /sys/block/nullb0/inflight 
/sys/block/nullb0/inflight
gkim@ib1:~/pb-ltp/blktests$ cat /sys/block/nullb0/inflight 
       1        0
gkim@ib1:~/pb-ltp/blktests$ sudo fuser /dev/nullb0
/dev/nullb0:         31484
gkim@ib1:~/pb-ltp/blktests$ ps 31484
  PID TTY      STAT   TIME COMMAND
31484 ?        D      0:00 /lib/systemd/systemd-udevd
gkim@ib1:~/pb-ltp/blktests$ cat /sys/block/nullb0/inflight 
       1        0

I tried following patch but it did not work.

gkim@ib1:~/pb-ltp/blktests$ git diff
diff --git a/tests/block/017 b/tests/block/017
index e4a9259..faab514 100755
--- a/tests/block/017
+++ b/tests/block/017
@@ -32,6 +32,8 @@ test() {
                return 1
        fi
 
+       udevadm settle
+       
        dd if=/dev/nullb0 of=/dev/null bs=4096 iflag=direct count=1 status=none &
        sleep 0.1
        show_inflight