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

Tetsuo Handa
2025-10-31T11:28:54Z

Who can take this patch?

On 2025/10/23 16:59, Jan Kara wrote:
> 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
>>
>>