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

[Zhang Yi]

On 2021/7/4 22:04, Theodore Ts'o wrote:
> On Sat, Jul 03, 2021 at 12:55:09PM +0800, Zhang Yi wrote:
>> Yeah, it sounds good to me. Do you want me to send the fix patch, or you
>> modify your commit 8f9e16badb8fd in another email directly?
> 
> I've gone ahead and made the changes; what do you think?
> 
> I like how it also removes 40 lines of code.  :-)
> 

Thanks for the fix, this patch looks good to me besides one error
handling below.

> 
>>From ef3130d1b0b8ca769252d6a722a2e59a00141383 Mon Sep 17 00:00:00 2001
> From: Theodore Ts'o <tytso at mit.edu>
> Date: Fri, 2 Jul 2021 18:05:03 -0400
> Subject: [PATCH] ext4: inline jbd2_journal_[un]register_shrinker()
> 
> The function jbd2_journal_unregister_shrinker() was getting called
> twice when the file system was getting unmounted.  On Power and ARM
> platforms this was causing kernel crash when unmounting the file
> system, when a percpu_counter was destroyed twice.
> 
> Fix this by removing jbd2_journal_[un]register_shrinker() functions,
> and inlining the shrinker setup and teardown into
> journal_init_common() and jbd2_journal_destroy().  This means that
> ext4 and ocfs2 now no longer need to know about registering and
> unregistering jbd2's shrinker.
> 
> Also, while we're at it, rename the percpu counter from
> j_jh_shrink_count to j_checkpoint_jh_count, since this makes it
> clearer what this counter is intended to track.
> 
> Fixes: 4ba3fcdde7e3 ("jbd2,ext4: add a shrinker to release checkpointed buffers")
> Reported-by: Sachin Sant <sachinp at linux.vnet.ibm.com>
> Reported-by: Jon Hunter <jonathanh at nvidia.com>
> Signed-off-by: Theodore Ts'o <tytso at mit.edu>
> ---
>  fs/ext4/super.c      |   8 ---
>  fs/jbd2/checkpoint.c |   4 +-
>  fs/jbd2/journal.c    | 148 +++++++++++++++++--------------------------
>  include/linux/jbd2.h |   6 +-
>  4 files changed, 63 insertions(+), 103 deletions(-)
> 
[..]
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 152880c298ca..8a9c94dd3599 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
[..]
>  /*
>   * Management for journal control blocks: functions to create and
>   * destroy journal_t structures, and to initialise and read existing
> @@ -1361,6 +1403,19 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  	journal->j_sb_buffer = bh;
>  	journal->j_superblock = (journal_superblock_t *)bh->b_data;
>  
> +	journal->j_shrink_transaction = NULL;
> +	journal->j_shrinker.scan_objects = jbd2_journal_shrink_scan;
> +	journal->j_shrinker.count_objects = jbd2_journal_shrink_count;
> +	journal->j_shrinker.seeks = DEFAULT_SEEKS;
> +	journal->j_shrinker.batch = journal->j_max_transaction_buffers;
> +
> +	if (percpu_counter_init(&journal->j_checkpoint_jh_count, 0, GFP_KERNEL))
> +		goto err_cleanup;
> +
> +	if (register_shrinker(&journal->j_shrinker)) {
> +		percpu_counter_destroy(&journal->j_checkpoint_jh_count);
> +		goto err_cleanup;
> +	}

Need to release j_sb_buffer in above two error path.

Thanks,
Yi.