FYI, we noticed the following commit (built with gcc-7):

commit: e50b1e327aeb4b224364aa6f85c1713ff8b3654b ("null_blk: remove legacy IO path")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: blktests
with following parameters:

	disk: 1HDD
	test: block-group2



on test machine: qemu-system-x86_64 -enable-kvm -cpu host -smp 2 -m 4G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):




Cloning into 'blktests'...
Note: checking out 'e9ffecc0ee82759cf8316e6a4b8cf80df0c27e0a'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b <new-branch-name>

HEAD is now at e9ffecc... Convert license headers to SPDX tags
make -C src all
make[1]: Entering directory '/lkp/benchmarks/blktests/blktests/src'
cc  -O2 -Wall -o loblksize loblksize.c
cc  -O2 -Wall -o loop_get_status_null loop_get_status_null.c
cc  -O2 -Wall -o openclose openclose.c
cc  -O2 -Wall -o sg/dxfer-from-dev sg/dxfer-from-dev.c
cc  -O2 -Wall -o sg/syzkaller1 sg/syzkaller1.c
cc  -O2 -Wall -o nbdsetsize nbdsetsize.c
g++  -O2 -std=c++11 -Wall -Wextra -Wno-sign-compare -Werror -o discontiguous-io discontiguous-io.cpp
make[1]: Leaving directory '/lkp/benchmarks/blktests/blktests/src'
2018-10-23 14:13:49 sed "s:^:block/:" /lkp/benchmarks/blktests/blktests/tests/block-group2 | grep -F -f merged_ignored_files
block/011 [ignored by lkp]
block/019 [ignored by lkp]
2018-10-23 14:13:49 sed "s:^:block/:" /lkp/benchmarks/blktests/blktests/tests/block-group2 | grep -v -F -f merged_ignored_files
2018-10-23 14:13:49 ./check block/009 block/010 block/012 block/013 block/014 block/015 block/016 block/017 block/018 block/020 block/021 block/022 block/023 block/024
block/009 (check page-cache coherency after BLKDISCARD)     
    runtime  ...
block/009 (check page-cache coherency after BLKDISCARD)      [passed]
    runtime  ...  0.925s
block/010 (run I/O on null_blk with shared and non-shared tags)
    runtime  ...
block/010 (run I/O on null_blk with shared and non-shared tags) [passed]
    runtime                    ...  469.856s
    Individual tags read iops  ...  272936
    Shared tags read iops      ...  303528
block/012 => vda (check that a read-only block device fails writes)
    runtime  ...
block/012 => vda (check that a read-only block device fails writes) [passed]
    runtime  ...  1.244s
block/013 => vda (try BLKRRPART on a mounted device)        
    runtime  ...
block/013 => vda (try BLKRRPART on a mounted device)         [passed]
    runtime  ...  696.818s
block/014 (run null-blk with blk-mq and timeout injection configured)
    runtime  ...
block/014 (run null-blk with blk-mq and timeout injection configured) [passed]
    runtime  ...  101.446s
block/015 (run null-blk on different schedulers with requeue injection configured)
    runtime  ...
block/015 (run null-blk on different schedulers with requeue injection configured) [passed]
    runtime  ...  11.414s
block/016 (send a signal to a process waiting on a frozen queue)
    runtime  ...
block/016 (send a signal to a process waiting on a frozen queue) [passed]
    runtime  ...  8.045s
block/017 (do I/O and check the inflight counter)           
    runtime  ...
block/017 (do I/O and check the inflight counter)            [failed]
    runtime  ...  1.661s
    --- tests/block/017.out	2018-10-23 14:13:47.496000000 +0000
    +++ /lkp/benchmarks/blktests/blktests/results/nodev/block/017.out.bad	2018-10-23 14:35:21.045000000 +0000
    @@ -1,17 +1,6 @@
     Running block/017
     queue mode 1
    -sysfs inflight reads 1
    -sysfs inflight writes 0
    -sysfs stat 1
    -diskstats 1
    -sysfs inflight reads 1
    ...
    (Run 'diff -u tests/block/017.out /lkp/benchmarks/blktests/blktests/results/nodev/block/017.out.bad' to see the entire diff)
block/018 (do I/O and check iostats times)                  
    runtime  ...
block/018 (do I/O and check iostats times)                   [failed]
    runtime  ...  5.078s
    --- tests/block/018.out	2018-10-23 14:13:47.496000000 +0000
    +++ /lkp/benchmarks/blktests/blktests/results/nodev/block/018.out.bad	2018-10-23 14:35:26.171000000 +0000
    @@ -1,13 +1,6 @@
     Running block/018
     queue mode 1
    -read 0 s
    -write 0 s
    -read 1 s
    -write 0 s
    -read 1 s
    ...
    (Run 'diff -u tests/block/018.out /lkp/benchmarks/blktests/blktests/results/nodev/block/018.out.bad' to see the entire diff)
block/020 (run null-blk on different schedulers with only one hardware tag)
    runtime  ...
block/020 (run null-blk on different schedulers with only one hardware tag) [passed]
    runtime  ...  31.216s
block/021 (read/write nr_requests on null-blk with different schedulers)
    runtime  ...
block/021 (read/write nr_requests on null-blk with different schedulers) [passed]
    runtime  ...  5.016s
block/022 (run null-blk with legacy blk path and timeout injection configured)
    runtime  ...
block/022 (run null-blk with legacy blk path and timeout injection configured) [failed]
    runtime  ...  0.012s
    --- tests/block/022.out	2018-10-23 14:13:47.496000000 +0000
    +++ /lkp/benchmarks/blktests/blktests/results/nodev/block/022.out.bad	2018-10-23 14:36:02.653000000 +0000
    @@ -1,2 +1,2 @@
     Running block/022
    -Test complete
    +modprobe: ERROR: could not insert 'null_blk': Invalid argument
block/023 (do I/O on all null_blk queue modes)              
    runtime  ...
block/023 (do I/O on all null_blk queue modes)               [failed]
    runtime  ...  0.243s
    --- tests/block/023.out	2018-10-23 14:13:47.496000000 +0000
    +++ /lkp/benchmarks/blktests/blktests/results/nodev/block/023.out.bad	2018-10-23 14:36:02.946000000 +0000
    @@ -1,5 +1,5 @@
     Running block/023
     Queue mode 0
    -Queue mode 1
    +modprobe: ERROR: could not insert 'null_blk': Invalid argument
     Queue mode 2
     Test complete
block/024 (do I/O faster than a jiffy and check iostats times)
    runtime  ...
block/024 (do I/O faster than a jiffy and check iostats times) [failed]
    runtime  ...  2.500s
    --- tests/block/024.out	2018-10-23 14:13:47.496000000 +0000
    +++ /lkp/benchmarks/blktests/blktests/results/nodev/block/024.out.bad	2018-10-23 14:36:05.496000000 +0000
    @@ -1,13 +1,6 @@
     Running block/024
     queue mode 1
    -read 0 s
    -write 0 s
    -read 1 s
    -write 0 s
    -read 1 s
    ...
    (Run 'diff -u tests/block/024.out /lkp/benchmarks/blktests/blktests/results/nodev/block/024.out.bad' to see the entire diff)



To reproduce:

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email



Thanks,
Rong Chen