linux-ext4 - Re: [PATCH v2 2/2] ext4: set 256 blocks in a block group then apply io pressure

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Message-ID: <20220708152014.bifm4u2wmdwj3mnf@zlang-mailbox>
Date:   Fri, 8 Jul 2022 23:20:14 +0800
From:   Zorro Lang <zlang@...hat.com>
To:     Sun Ke <sunke32@...wei.com>
Cc:     fstests@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH v2 2/2] ext4: set 256 blocks in a block group then apply
 io pressure

On Fri, Jul 08, 2022 at 07:21:55PM +0800, Sun Ke wrote:
> Set 256 blocks in a block group, then inject I/O pressure, it will
> trigger off kernel BUG in ext4_mb_mark_diskspace_used.
> 
> Regression test for commit a08f789d2ab5 ext4: fix bug_on
> ext4_mb_use_inode_pa.
> 
> Signed-off-by: Sun Ke <sunke32@...wei.com>
> ---
>  tests/ext4/058     | 33 +++++++++++++++++++++++++++++++++
>  tests/ext4/058.out |  2 ++
>  2 files changed, 35 insertions(+)
>  create mode 100755 tests/ext4/058
>  create mode 100644 tests/ext4/058.out
> 
> diff --git a/tests/ext4/058 b/tests/ext4/058
> new file mode 100755
> index 00000000..b718c1ac
> --- /dev/null
> +++ b/tests/ext4/058
> @@ -0,0 +1,33 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2022 HUAWEI.  All Rights Reserved.
> +#
> +# FS QA Test 058
> +#
> +# Set 256 blocks in a block group, then inject I/O pressure,
> +# it will trigger off kernel BUG in ext4_mb_mark_diskspace_used
> +#
> +# Regression test for commit
> +# a08f789d2ab5 ext4: fix bug_on ext4_mb_use_inode_pa 
> +#
> +. ./common/preamble
> +_begin_fstest auto

quick ?

> +
> +# real QA test starts here
> +
> +_supported_fs ext4
> +_fixed_by_kernel_commit a08f789d2ab5 \
> +	"ext4: fix bug_on ext4_mb_use_inode_pa"
> +_require_scratch
> +
> +# set 256 blocks in a block group
> +_scratch_mkfs -g 256 >>$seqres.full 2>&1 || _fail "mkfs failed"
> +_scratch_mount
> +
> +$FSSTRESS_PROG -d $SCRATCH_MNT/stress -n 1000 >> $seqres.full

Use "2>&1", if you'd like to avoid some fsstress error output break golden image.

BTW, just for make, are you sure this can reproduce that bug? Due to that fix
commit said:
...
    we can easily reproduce this problem with the following commands:
            `fallocate -l100M disk`
            `mkfs.ext4 -b 1024 -g 256 disk`
            `mount disk /mnt`
            `fsstress -d /mnt -l 0 -n 1000 -p 1`
...

It uses "-l 0" to loop run fsstress until hit the bug. You removed the '-l 0',
so are you sure one round `fsstress -n 1000` is enough to reproduce this bug
stably?

Thanks,
Zorro

> +
> +echo "Silence is golden"
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/ext4/058.out b/tests/ext4/058.out
> new file mode 100644
> index 00000000..fb5ca60b
> --- /dev/null
> +++ b/tests/ext4/058.out
> @@ -0,0 +1,2 @@
> +QA output created by 058
> +Silence is golden
> -- 
> 2.13.6
>