[Ocfs2-devel] [PATCH 4/4] ocfs2: introduce ext4 MMP feature

[Joseph Qi]

On 8/8/22 5:07 PM, Heming Zhao wrote:
> On Mon, Aug 08, 2022 at 04:19:22PM +0800, Joseph Qi wrote:
>>
>>
>> On 7/30/22 9:14 AM, Heming Zhao wrote:
>>> MMP (multiple mount protection) gives filesystem ability to prevent
>>> from being mounted multiple times.
>>>
>>> For avoiding data corruption when non-clustered and/or clustered mount
>>> are happening at same time, this commit introduced MMP feature. MMP
>>> idea is from ext4 MMP (fs/ext4/mmp.c) code. For ocfs2 is a clustered
>>> fs and also for compatible with existing slotmap feature, I did some
>>> optimization and modification when porting from ext4 to ocfs2.
>>>
>>> For optimization:
>>> mmp has a kthread kmmpd-<dev>, which is only created in non-clustered
>>> mode.
>>>
>>> We set a rule:
>>> If last mount didn't do unmount, (eg: crash), the next mount MUST be
>>> same mount type.
>>>
>>> At last, this commit also fix commit c80af0c250c8 ("Revert "ocfs2:
>>> mount shared volume without ha stack") mentioned issue.
>>
>> I suggest we re-split this series (especially patch 3 and 4), but not
>> revive a buggy commit first and then another commit fixing it BTW.
>>
> 
> No problem. I remembered this fixing style, and won't make this kind of
> mistake again.
> 
> Do we need to wait for Mark's further comment?
> It looks Mark didn't like non-clustered mount at his first reply, but he
> showed another idea for non-clustered mount on the second reply. And I
> am sure what's his meaning/attitude for non-clustered mount.
> 

Yes, let's take Mark's input first for the next version.

Thanks,
Joseph