linux-ext4 - Re: Patch of adding utility to check the status of MMP

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Message-ID: <CAPTn0cDwGHcA7v2WtKFFEPcYh=uHpBu50YL31XAdEXCe1oLh7g@mail.gmail.com>
Date:	Wed, 13 Nov 2013 20:07:35 +0800
From:	Li Xi <pkuelelixi@...il.com>
To:	linux-ext4@...r.kernel.org
Cc:	Shuichi Ihara <sihara@....com>
Subject: Re: Patch of adding utility to check the status of MMP

Hi all,

MMP feature of ext4 really helps us a lot to avoid mounting file
system more than once, especailly when using ext4 as the basis of a
distributed file sytem, e.g. Lustre. However, lack of a userspace
utility to check the status of MMP makes it diffcult to utilize this
feature to make failover decisions. We tried to write a script to do
so by parsing the output of debugfs command. But this solution is not
very straight forward. In order to check the sequence and checksum
correctly, the script has to embed a lot of value definition, which
could be error prone.

Finally, we decided to add a new command in the e2fsprogs. With that
command, a server is able to check the current MMP state of a device
so that it can decide whether to take over the file system service
from aother server. I think the patch might helps other use cases too.

The attachment is the patch.

Thanks,
Li  Xi

Download attachment "mmpstatus.patch" of type "application/octet-stream" (14921 bytes)