Re: [PATCH v3] btrfs: Test proper interaction between skip_balance and paused balance

Anand Jain
2021-11-10T10:04:18Z

On 8/11/21 10:29 pm, Nikolay Borisov wrote:
> Ensure a device can be added to a filesystem that has a paused balance
> operation and has been mounted with the 'skip_balance' mount option
>
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>
> V3:
> * Added swapon to the list of exclusive ops
> * Use _spare_dev_get
> * Test balance resume via progs while balance is paused. I hit an assertion failure
> outside of xfstest while doing this sequence of steps so let's add it to
> ensure that's not regressed.
>
> tests/btrfs/049 | 92 +++++++++++++++++++++++++++++++++++++++++++++
> tests/btrfs/049.out | 1 +
> 2 files changed, 93 insertions(+)
> create mode 100755 tests/btrfs/049
>
> diff --git a/tests/btrfs/049 b/tests/btrfs/049
> new file mode 100755
> index 000000000000..d01ef05e5ead
> --- /dev/null
> +++ b/tests/btrfs/049
> @@ -0,0 +1,92 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2021 SUSE Linux Products GmbH. All Rights Reserved.
> +#
> +# FS QA Test 049
> +#
> +# Ensure that it's possible to add a device when we have a paused balance
> +# and the filesystem is mounted with skip_balance. The issue is fixed by a patch

> +# titled "btrfs: allow device add if balance is paused"

It is a new feature, not a bug fix? The kernel patch won't backport to
the stable kernels. Then on older kernels, this test has to exit with
_notrun().
Is there any way to achieve this? There isn't any sysfs interface that
will help and, so far we haven't used the kernel version to achieve
something like this.

> +#
> +. ./common/preamble
> +_begin_fstest quick balance auto
> +
> +# real QA test starts here
> +
> +_supported_fs btrfs
> +_require_scratch_swapfile
> +_require_scratch_dev_pool 3
> +
> +_scratch_dev_pool_get 2
> +_spare_dev_get
> +
> +swapfile="$SCRATCH_MNT/swap"
> +_scratch_pool_mkfs >/dev/null
> +_scratch_mount
> +_format_swapfile "$swapfile" $(($(get_page_size) * 10))
> +
> +check_exclusive_ops()
> +{
> + $BTRFS_UTIL_PROG device remove 2 $SCRATCH_MNT &>/dev/null
> + [ $? -ne 0 ] || _fail "Successfully removed device"
> + $BTRFS_UTIL_PROG filesystem resize -5m $SCRATCH_MNT &> /dev/null
> + [ $? -ne 0 ] || _fail "Successfully resized filesystem"
> + $BTRFS_UTIL_PROG replace start -B 2 $SPARE_DEV $SCRATCH_MNT &> /dev/null
> + [ $? -ne 0 ] || _fail "Successfully replaced device"
> + swapon "$swapfile" &> /dev/null
> + [ $? -ne 0 ] || _fail "Successfully enabled a swap file"
> +}
> +
> +uuid=$(findmnt -n -o UUID $SCRATCH_MNT)
> +
> +# Create some files on the so that balance doesn't complete instantly
> +args=`_scale_fsstress_args -z \
> + -f write=10 -f creat=10 \
> + -n 1000 -p 2 -d $SCRATCH_MNT/stress_dir`
> +echo "Run fsstress $args" >>$seqres.full
> +$FSSTRESS_PROG $args >/dev/null 2>&1
> +
> +# Start and pause balance to ensure it will be restored on remount
> +echo "Start balance" >>$seqres.full
> +_run_btrfs_balance_start --bg "$SCRATCH_MNT"
> +$BTRFS_UTIL_PROG balance pause "$SCRATCH_MNT"
> +$BTRFS_UTIL_PROG balance status "$SCRATCH_MNT" | grep -q paused
> +[ $? -eq 0 ] || _fail "Balance not paused"
> +
> +# Exclusive ops should be blocked on manual pause of balance
> +check_exclusive_ops
> +
> +# Balance is now placed in paused state during mount
> +_scratch_cycle_mount "skip_balance"
> +
> +# Exclusive ops should be blocked on balance pause due to 'skip_balance'
> +check_exclusive_ops
> +
> +# Device add is the only allowed operation
> +$BTRFS_UTIL_PROG device add -K -f $SPARE_DEV "$SCRATCH_MNT"
> +
> +# Exclusive ops should still be blocked on account that balance is still paused
> +check_exclusive_ops
> +
> +# Should be possible to resume balance after device add
> +$BTRFS_UTIL_PROG balance resume "$SCRATCH_MNT" &>/dev/null
> +[ $? -eq 0 ] || _fail "Couldn't resume balance after device add"
> +
> +# Add more files so that new balance won't fish immediately
> +$FSSTRESS_PROG $args >/dev/null 2>&1
> +
> +# Now pause->resume balance. This ensures balance paused is properly set in
> +# the kernel and won't trigger an assertion failure.
> +echo "Start balance" >>$seqres.full
> +_run_btrfs_balance_start --bg "$SCRATCH_MNT"
> +$BTRFS_UTIL_PROG balance pause "$SCRATCH_MNT"
> +$BTRFS_UTIL_PROG balance status "$SCRATCH_MNT" | grep -q paused
> +[ $? -eq 0 ] || _fail "Balance not paused"
> +$BTRFS_UTIL_PROG balance resume "$SCRATCH_MNT" &>/dev/null
> +[ $? -eq 0 ] || _fail "Balance can't be resumed via IOCTL"
> +
> +_spare_dev_put
> +_scratch_dev_pool_put
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/btrfs/049.out b/tests/btrfs/049.out
> index cb0061b33ff0..c69568ad9323 100644
> --- a/tests/btrfs/049.out
> +++ b/tests/btrfs/049.out
> @@ -1 +1,2 @@
> QA output created by 049
> +Silence is golden
> --
> 2.17.1
>