On 2020/5/20 下午6:02, Qu Wenruo wrote:
> 
> 
> On 2020/5/20 下午5:29, Filipe Manana wrote:
>> On Wed, May 20, 2020 at 8:59 AM Qu Wenruo <wqu@suse.com> wrote:
>>>
>>> Test if canceling a running balance can cause later balance to dead
>>> loop.
>>>
>>> The ifx is titled "btrfs: relocation: Clear the DEAD_RELOC_TREE bit for
>>>  orphan roots to prevent runaway balance".
>>>
>>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>>> ---
>>> Changelog:
>>> v2:
>>> - Remove lsof debug output
>>> v3:
>>> - Remove ps debug output
>>> ---
>>>  tests/btrfs/213     | 64 +++++++++++++++++++++++++++++++++++++++++++++
>>>  tests/btrfs/213.out |  2 ++
>>>  tests/btrfs/group   |  1 +
>>>  3 files changed, 67 insertions(+)
>>>  create mode 100755 tests/btrfs/213
>>>  create mode 100644 tests/btrfs/213.out
>>>
>>> diff --git a/tests/btrfs/213 b/tests/btrfs/213
>>> new file mode 100755
>>> index 00000000..f56b0279
>>> --- /dev/null
>>> +++ b/tests/btrfs/213
>>> @@ -0,0 +1,64 @@
>>> +#! /bin/bash
>>> +# SPDX-License-Identifier: GPL-2.0
>>> +# Copyright (C) 2020 SUSE Linux Products GmbH. All Rights Reserved.
>>> +#
>>> +# FS QA Test 213
>>> +#
>>> +# Test if canceling a running balance can lead to dead looping balance
>>> +#
>>> +seq=`basename $0`
>>> +seqres=$RESULT_DIR/$seq
>>> +echo "QA output created by $seq"
>>> +
>>> +here=`pwd`
>>> +tmp=/tmp/$$
>>> +status=1       # failure is the default!
>>> +trap "_cleanup; exit \$status" 0 1 2 3 15
>>> +
>>> +_cleanup()
>>> +{
>>> +       cd /
>>> +       rm -f $tmp.*
>>> +}
>>> +
>>> +# get standard environment, filters and checks
>>> +. ./common/rc
>>> +. ./common/filter
>>> +
>>> +# remove previous $seqres.full before test
>>> +rm -f $seqres.full
>>> +
>>> +# Modify as appropriate.
>>> +_supported_fs btrfs
>>> +_supported_os Linux
>>> +_require_scratch
>>> +_require_command "$KILLALL_PROG" killall
>>> +
>>> +_scratch_mkfs >> $seqres.full
>>> +_scratch_mount
>>> +
>>> +runtime=4
>>> +
>>> +# Create enough IO so that we need around $runtime seconds to relocate it
>>> +dd if=/dev/zero bs=1M of="$SCRATCH_MNT/file" oflag=sync status=none \
>>> +       &> /dev/null &
>>> +dd_pid=$!
>>> +sleep $runtime
>>> +"$KILLALL_PROG" -q dd &> /dev/null
>>
>> Do we really need the killall program? There's only one dd process.
>>
>> We should also kill the dd process at _cleanup(), as killing the test
>> during the sleep above will result in the dd process not being killed.
> 
> The main problem here is, I can't find a good way to kill dd.
> plain 'kill $dd_pid' doesn't seem to kill it properly, as my debug
> lsof/ps still shows dd running and failed to unmount the fs.
> 
> 'kill -KILL $dd_pid' kills it well, but causes extra output for the
> terminated dd.
> 
> Only 'killall -q dd' works as expected.
> 
> Any good advice on this?

Oh, the fstests "kindly" overrides dd, "kill $dd_pid" only kills the
child bash running that dd function, not the real dd command.
I'll use xfs_io to ensure we get no extra wrapper.

Thanks,
Qu

> 
>>
>>> +wait $dd_pid
>>> +
>>> +# Now balance should take at least $runtime seconds, we can cancel it at
>>> +# $runtime/2 to ensure a success cancel.
>>> +$BTRFS_UTIL_PROG balance start -d --bg "$SCRATCH_MNT"
>>> +sleep $(($runtime / 2))
>>> +$BTRFS_UTIL_PROG balance cancel "$SCRATCH_MNT"
>>> +
>>> +# Now check if we can finish relocating metadata, which should finish very
>>> +# quickly
>>> +$BTRFS_UTIL_PROG balance start -m "$SCRATCH_MNT" >> $seqres.full
>>
>> Why redirect this one to $seqres.full and not the other balance? What
>> kind of useful information it provides?
> 
> Not really much, just an indicator to show that the balance finishes as
> expected.
> And we don't want to output it golden output, as mkfs change may create
> more metadata chunks and cause difference.
> 
> For other ones, like the one to be canceled, we don't really care that much.
> 
> Thanks,
> Qu
>>
>>> +
>>> +echo "Silence is golden"
>>> +
>>> +# success, all done
>>> +status=0
>>> +exit
>>> diff --git a/tests/btrfs/213.out b/tests/btrfs/213.out
>>> new file mode 100644
>>> index 00000000..bd8f2430
>>> --- /dev/null
>>> +++ b/tests/btrfs/213.out
>>> @@ -0,0 +1,2 @@
>>> +QA output created by 213
>>> +Silence is golden
>>> diff --git a/tests/btrfs/group b/tests/btrfs/group
>>> index 8d65bddd..fe4d5bb3 100644
>>> --- a/tests/btrfs/group
>>> +++ b/tests/btrfs/group
>>> @@ -215,3 +215,4 @@
>>>  210 auto quick qgroup snapshot
>>>  211 auto quick log prealloc
>>>  212 auto balance dangerous
>>> +213 auto fast balance dangerous
>>
>> fast -> quick
>>
>> Thanks.
>>
>>> --
>>> 2.26.2
>>>
>>
>>
>