[dm-devel] Fix "dm kcopyd: Fix bug causing workqueue stalls" causes dead lock

[Guruswamy Basavaiah]

Hello,
We use 4.4.184 in our builds and the patch fails to apply.
Is it possible to give a patch for 4.4.x branch ?

patching Logs.
patching file drivers/md/dm-snap.c
Hunk #1 succeeded at 19 (offset 1 line).
Hunk #2 succeeded at 105 (offset -1 lines).
Hunk #3 succeeded at 157 (offset -4 lines).
Hunk #4 succeeded at 1206 (offset -120 lines).
Hunk #5 FAILED at 1508.
Hunk #6 succeeded at 1412 (offset -124 lines).
Hunk #7 succeeded at 1425 (offset -124 lines).
Hunk #8 FAILED at 1925.
Hunk #9 succeeded at 1866 with fuzz 2 (offset -255 lines).
Hunk #10 succeeded at 2202 (offset -294 lines).
Hunk #11 succeeded at 2332 (offset -294 lines).
2 out of 11 hunks FAILED -- saving rejects to file drivers/md/dm-snap.c.rej

Guru

On Thu, 10 Oct 2019 at 01:33, Guruswamy Basavaiah <guru2018 at gmail.com> wrote:
>
> Hello Mike,
>  I will get the testing result before end of Thursday.
> Guru
>
> On Wed, 9 Oct 2019 at 21:34, Mike Snitzer <snitzer at redhat.com> wrote:
> >
> > On Wed, Oct 09 2019 at 11:44am -0400,
> > Nikos Tsironis <ntsironis at arrikto.com> wrote:
> >
> > > On 10/9/19 5:13 PM, Mike Snitzer wrote:> On Tue, Oct 01 2019 at  8:43am -0400,
> > > > Nikos Tsironis <ntsironis at arrikto.com> wrote:
> > > >
> > > >> On 10/1/19 3:27 PM, Guruswamy Basavaiah wrote:
> > > >>> Hello Nikos,
> > > >>>  Yes, issue is consistently reproducible with us, in a particular
> > > >>> set-up and test case.
> > > >>>  I will get the access to set-up next week, will try to test and let
> > > >>> you know the results before end of next week.
> > > >>>
> > > >>
> > > >> That sounds great!
> > > >>
> > > >> Thanks a lot,
> > > >> Nikos
> > > >
> > > > Hi Guru,
> > > >
> > > > Any chance you could try this fix that I've staged to send to Linus?
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.4&id=633b1613b2a49304743c18314bb6e6465c21fd8a
> > > >
> > > > Shiort of that, Nikos: do you happen to have a test scenario that teases
> > > > out this deadlock?
> > > >
> > >
> > > Hi Mike,
> > >
> > > Yes,
> > >
> > > I created a 50G LV and took a snapshot of the same size:
> > >
> > >   lvcreate -n data-lv -L50G testvg
> > >   lvcreate -n snap-lv -L50G -s testvg/data-lv
> > >
> > > Then I ran the following fio job:
> > >
> > > [global]
> > > randrepeat=1
> > > ioengine=libaio
> > > bs=1M
> > > size=6G
> > > offset_increment=6G
> > > numjobs=8
> > > direct=1
> > > iodepth=32
> > > group_reporting
> > > filename=/dev/testvg/data-lv
> > >
> > > [test]
> > > rw=write
> > > timeout=180
> > >
> > > , concurrently with the following script:
> > >
> > > lvcreate -n dummy-lv -L1G testvg
> > >
> > > while true
> > > do
> > >  lvcreate -n dummy-snap -L1M -s testvg/dummy-lv
> > >  lvremove -f testvg/dummy-snap
> > > done
> > >
> > > This reproduced the deadlock for me. I also ran 'echo 30 >
> > > /proc/sys/kernel/hung_task_timeout_secs', to reduce the hung task
> > > timeout.
> > >
> > > Nikos.
> >
> > Very nice, well done.  Curious if you've tested with the fix I've staged
> > (see above)?  If so, does it resolve the deadlock?  If you've had
> > success I'd be happy to update the tags in the commit header to include
> > your Tested-by before sending it to Linus.  Also, any review of the
> > patch that you can do would be appreciated and with your formal
> > Reviewed-by reply would be welcomed and folded in too.
> >
> > Mike
>
>
>
> --
> Guruswamy Basavaiah



-- 
Guruswamy Basavaiah