Re: [PATCH v2] jbd2: allocate lock_class_key for jbd2_handle dynamically

Jan Kara
2025-10-23T07:59:22Z

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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=6e493c165d26d6fcbf72
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Tested-by: syzbot+6e493c165d26d6fcbf72@syzkaller.appspotmail.com

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

Reviewed-by: Jan Kara <jack@suse.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@suse.com>
SUSE Labs, CR