Re: [Ocfs2-devel] [PATCH 4/4] ocfs2: introduce ext4 MMP feature - Joseph Qi via Ocfs2-devel

From: Joseph Qi via Ocfs2-devel <ocfs2-devel@oss.oracle.com>
To: Heming Zhao <heming.zhao@suse.com>, ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH 4/4] ocfs2: introduce ext4 MMP feature
Date: Mon, 8 Aug 2022 16:19:22 +0800	[thread overview]
Message-ID: <e90f3f19-f790-8018-ddb4-0bb405d45ad6@linux.alibaba.com> (raw)
In-Reply-To: <20220730011411.11214-5-heming.zhao@suse.com>

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.

Thanks,
Joseph

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