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

[Heming Zhao]

Very weird problem. I added Junxiao & Mark in 'CC' field, but there is
only kept 'To' field. I tested to use CC to send mail for other mail address,
it worked well.

On Mon, Aug 08, 2022 at 05:07:14PM +0800, Heming Zhao via Ocfs2-devel 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.
> 
> Thanks,
> Heming
> 
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