Re: [PATCH] ocfs2: update seq_file index in ocfs2_dlm_seq_next

[Joseph Qi <joseph.qi@linux.alibaba.com>]

On 11/11/24 3:04 PM, Wengang Wang wrote:
> 
> 
>> On Nov 10, 2024, at 5:38 PM, Joseph Qi <joseph.qi@linux.alibaba.com> wrote:
>>
>>
>>
>> On 11/9/24 3:28 AM, Wengang Wang wrote:
>>> The following INFO level message was seen:
>>>
>>> seq_file: buggy .next function ocfs2_dlm_seq_next [ocfs2] did not
>>> update position index
>>>
>>> Fix:
>>> Updata m->index to make seq_read_iter happy though the index its self makes
>>> no sense to ocfs2_dlm_seq_next.
>>>
>>> Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
>>> ---
>>> fs/ocfs2/dlmglue.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
>>> index 60df52e4c1f8..349d131369cf 100644
>>> --- a/fs/ocfs2/dlmglue.c
>>> +++ b/fs/ocfs2/dlmglue.c
>>> @@ -3120,6 +3120,7 @@ static void *ocfs2_dlm_seq_next(struct seq_file *m, void *v, loff_t *pos)
>>> }
>>> spin_unlock(&ocfs2_dlm_tracking_lock);
>>>
>>> + m->index++;
>>
>> We can directly use '(*pos)++' instead.
>>
> 
> The input/output "pos” indicates more an offset into the file. Actually the output for an item is not really 1 byte in length, so incrementing the offset by 1 sounds a bit strange to me. Instead If we increment the “index”, It would be easier to understand it as  for next item. Though updating “index” or updating “*pos” instead makes no difference to binary running, the code understanding is different.  I know other seq_operations.next functions are directly incrementing the “*pos”, I think updating “index” is better. Well, if you persist (*pos)++, I will also let it go.
> 
From seq_read_iter(), the input pos is equivalent to '&m->index'. So the
above two ways seems have no functional difference.
IMO, we'd better hide the m->index logic into seqfile and just use pos
instead like other .next implementations.

Thanks,
Joseph