Re: [PATCH v2] fstests: btrfs: Add regression test to check if btrfs can handle high devid

[Filipe Manana <fdmanana@gmail.com>]

On Thu, Oct 3, 2019 at 8:55 AM Qu Wenruo <wqu@suse.com> wrote:
>
> Add a regression test to check if btrfs can handle high devid.
>
> The test will add and remove devices to a btrfs fs, so that the devid
> will increase to uncommon but still valid values.
>
> The regression is introduced by kernel commit ab4ba2e13346 ("btrfs:
> tree-checker: Verify dev item").
> The fix is titled "btrfs: tree-checker: Fix wrong check on max devid".
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Thanks! It's looking much better, the comments really help.

> ---
> Changelog:
> v2:
> - Small comment refinement
> - Add more comment explaining some details, including:
>   * Why node size affects the runtime
>   * How the triggering threshold is calculated
>   * Why the intermediate number 64 is used as iteration number
> ---
>  tests/btrfs/194     | 86 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/194.out |  2 ++
>  tests/btrfs/group   |  1 +
>  3 files changed, 89 insertions(+)
>  create mode 100755 tests/btrfs/194
>  create mode 100644 tests/btrfs/194.out
>
> diff --git a/tests/btrfs/194 b/tests/btrfs/194
> new file mode 100755
> index 00000000..b7249f0d
> --- /dev/null
> +++ b/tests/btrfs/194
> @@ -0,0 +1,86 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
> +#
> +# FS QA Test 194
> +#
> +# Test if btrfs can handle large device ids.
> +#
> +# The regression is introduced by kernel commit ab4ba2e13346 ("btrfs:
> +# tree-checker: Verify dev item").
> +# The fix is titled: "btrfs: tree-checker: Fix wrong check on max devid"
> +#
> +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
> +
> +# real QA test starts here
> +
> +# Modify as appropriate.
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch_dev_pool 2
> +_scratch_dev_pool_get 2
> +
> +# Here we use 4k node size to reduce runtime (explained near _scratch_mkfs call)
> +# To use the minimal node size (4k) we need 4K page size.
> +if [ $(get_page_size) != 4096 ]; then
> +       _notrun "This test need 4k page size"
> +fi
> +
> +device_1=$(echo $SCRATCH_DEV_POOL | awk '{print $1}')
> +device_2=$(echo $SCRATCH_DEV_POOL | awk '{print $2}')
> +
> +echo device_1=$device_1 device_2=$device_2 >> $seqres.full
> +
> +# The wrong check limit is based on the max item size (BTRFS_MAX_DEVS() macro),
> +# and max item size is based on node size, so smaller node size will result
> +# much shorter runtime. So here we use minimal node size (4K) to reduce runtime.
> +_scratch_mkfs -n 4k >> $seqres.full
> +_scratch_mount
> +
> +# For 4k nodesize, the wrong limit is calculated by:
> +# ((4096 - 101 - 25 - 80) / 32) + 1
> +#    |      |    |    |     |- sizeof(btrfs_stripe)
> +#    |      |    |    |- sizeof(btrfs_chunk)
> +#    |      |    |- sizeof(btrfs_item)
> +#    |      |- sizeof(btrfs_header)
> +#    |- node size
> +# Which is 122.
> +#
> +# The old limit is wrong because it doesn't take devid holes into consideration.
> +# We can have large devid, but still have only 1 device.
> +#
> +# Add and remove device in a loop, each iteration will increase devid by 2.
> +# So by 64 iterations, we will definitely hit that 122 limit.
> +for (( i = 0; i < 64; i++ )); do
> +       $BTRFS_UTIL_PROG device add -f $device_2 $SCRATCH_MNT
> +       $BTRFS_UTIL_PROG device del $device_1 $SCRATCH_MNT
> +       $BTRFS_UTIL_PROG device add -f $device_1 $SCRATCH_MNT
> +       $BTRFS_UTIL_PROG device del $device_2 $SCRATCH_MNT
> +done
> +_scratch_dev_pool_put
> +
> +echo "Silence is golden"
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/btrfs/194.out b/tests/btrfs/194.out
> new file mode 100644
> index 00000000..7bfd50ff
> --- /dev/null
> +++ b/tests/btrfs/194.out
> @@ -0,0 +1,2 @@
> +QA output created by 194
> +Silence is golden
> diff --git a/tests/btrfs/group b/tests/btrfs/group
> index b92cb12c..d8aafe20 100644
> --- a/tests/btrfs/group
> +++ b/tests/btrfs/group
> @@ -196,3 +196,4 @@
>  191 auto quick send dedupe
>  192 auto replay snapshot stress
>  193 auto quick qgroup enospc limit
> +194 auto volume
> --
> 2.22.0
>


-- 
Filipe David Manana,

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