Re: [PATCH v3] btrfs: Add a test for dead looping balance after balance cancel

[Filipe Manana <fdmanana@gmail.com>]

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.

> +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?

> +
> +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
>


-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”