[powerpc][5.13.0-next-20210701] Kernel crash while running ltp(chdir01) tests

[Theodore Ts'o]

On Fri, Jul 02, 2021 at 05:38:10PM +0800, Guoqing Jiang wrote:
> 
> 
> I guess the problem is j_jh_shrink_count was destroyed in ext4_put_super _> 
> jbd2_journal_unregister_shrinker
> which is before the path ext4_put_super -> jbd2_journal_destroy ->
> jbd2_log_do_checkpoint to call
> percpu_counter_dec(&journal->j_jh_shrink_count).
> 
> And since jbd2_journal_unregister_shrinker is already called inside
> jbd2_journal_destroy, does it make sense
> to do this?
> 
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1176,7 +1176,6 @@ static void ext4_put_super(struct super_block *sb)
>         ext4_unregister_sysfs(sb);
> 
>         if (sbi->s_journal) {
> -               jbd2_journal_unregister_shrinker(sbi->s_journal);
>                 aborted = is_journal_aborted(sbi->s_journal);
>                 err = jbd2_journal_destroy(sbi->s_journal);
>                 sbi->s_journal = NULL;

Good catch.  There's another place where we call
jbd2_journal_unregister_shrinker(), in the failure path for
ext4_fill_super().

					- Ted

P.S.  Whatever outgoing mailer you are using, it's not preserving TAB
characters correctly.  You might want to look into that before trying
to submit a patch.