linux-ext4 - Re: [PATCH v2] jbd2: allocate lock_class_key for jbd2

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Message-ID: <vgpy66rcs3mvitijmt2v2yfwuhkijh33z3s76ghlsqq6yjgmtw@prlpxdeoitif>
Date: Thu, 23 Oct 2025 09:59:12 +0200
From: Jan Kara <jack@...e.cz>
To: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc: Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>, 
	Andreas Dilger <adilger.kernel@...ger.ca>, Jan Kara <jack@...e.com>, 
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] jbd2: allocate lock_class_key for jbd2_handle
 dynamically

On Wed 22-10-25 20:11:37, Tetsuo Handa wrote:
> syzbot is reporting possibility of deadlock due to sharing lock_class_key
> for jbd2_handle across ext4 and ocfs2. But this is a false positive, for
> one disk partition can't have two filesystems at the same time.
> 
> Reported-by: syzbot+6e493c165d26d6fcbf72@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=6e493c165d26d6fcbf72
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> Tested-by: syzbot+6e493c165d26d6fcbf72@...kaller.appspotmail.com

Thanks! Tha patch looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/jbd2/journal.c    | 6 ++++--
>  include/linux/jbd2.h | 6 ++++++
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index d480b94117cd..f43474002f50 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1521,7 +1521,6 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  			struct block_device *fs_dev,
>  			unsigned long long start, int len, int blocksize)
>  {
> -	static struct lock_class_key jbd2_trans_commit_key;
>  	journal_t *journal;
>  	int err;
>  	int n;
> @@ -1530,6 +1529,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  	if (!journal)
>  		return ERR_PTR(-ENOMEM);
>  
> +	lockdep_register_key(&journal->jbd2_trans_commit_key);
>  	journal->j_blocksize = blocksize;
>  	journal->j_dev = bdev;
>  	journal->j_fs_dev = fs_dev;
> @@ -1560,7 +1560,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  	journal->j_max_batch_time = 15000; /* 15ms */
>  	atomic_set(&journal->j_reserved_credits, 0);
>  	lockdep_init_map(&journal->j_trans_commit_map, "jbd2_handle",
> -			 &jbd2_trans_commit_key, 0);
> +			 &journal->jbd2_trans_commit_key, 0);
>  
>  	/* The journal is marked for error until we succeed with recovery! */
>  	journal->j_flags = JBD2_ABORT;
> @@ -1611,6 +1611,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
>  	kfree(journal->j_wbuf);
>  	jbd2_journal_destroy_revoke(journal);
>  	journal_fail_superblock(journal);
> +	lockdep_unregister_key(&journal->jbd2_trans_commit_key);
>  	kfree(journal);
>  	return ERR_PTR(err);
>  }
> @@ -2187,6 +2188,7 @@ int jbd2_journal_destroy(journal_t *journal)
>  		jbd2_journal_destroy_revoke(journal);
>  	kfree(journal->j_fc_wbuf);
>  	kfree(journal->j_wbuf);
> +	lockdep_unregister_key(&journal->jbd2_trans_commit_key);
>  	kfree(journal);
>  
>  	return err;
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 43b9297fe8a7..f5eaf76198f3 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1253,6 +1253,12 @@ struct journal_s
>  	 */
>  	struct lockdep_map	j_trans_commit_map;
>  #endif
> +	/**
> +	 * @jbd2_trans_commit_key:
> +	 *
> +	 * "struct lock_class_key" for @j_trans_commit_map
> +	 */
> +	struct lock_class_key	jbd2_trans_commit_key;
>  
>  	/**
>  	 * @j_fc_cleanup_callback:
> -- 
> 2.47.3
> 
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR