Ocfs2 devel - Apr 2016 - ocfs2: disk timeout, autoumount the volume to avoid host reboot

Hi, Guanghui,

That will be an good new feature to OCFS2.

There is one scenarios that one host have several LUNs connected with different
storage servers, may be iSCSI, and FC SAN.
One of the volumes(LUNs) disconnected from server, the host will be fence and
restart itself for heartbeat timeout.
Same time, the services running depend on the other good volumes(LUNs) will be
interrupted and cannot be accessed continuously for the host, which is been
restarted.

If OCFS2 had this feature, the services depending on other good status
volumes(LUNs) will be running continue, and the host will not be fence, and not
restart itself.
Only this services which depend on the abnormal volume(LUN) run timeout.

I think it is a good idea and feature for OCFS2.

Thank you.
Guozhonghua



Message: 2
Date: Wed, 20 Apr 2016 07:27:48 +0000
From: Zhangguanghui <zhang.guanghui at h3c.com>
Subject: [Ocfs2-devel] ocfs2: disk timeout, autoumount the volume to
        avoid calling emergency_restart
To: "ocfs2-devel-bounces at oss.oracle.com"
        <ocfs2-devel-bounces at oss.oracle.com>,   "ocfs2-devel at
oss.oracle.com"
        <ocfs2-devel at oss.oracle.com>
Message-ID:
        <E3535A62B291B54FBD1D003696CCB5375E19CDC7 at
H3CMLB14-EX.srv.huawei-3com.com>

Content-Type: text/plain; charset="utf-8"
Hi everyone


In ocfs2, when one storage volume can't access, all nodes which have mounted
the volume will fence self

due to write timeout or io error. So I make a useful attempt to add autoumount
option.

in the case, I know that for some reason umount may be hung.Based on the
analysis process of ocfs2 umount,

it's possible to complete all locks and wake up block events before
umounting the volume.

the way is to work well by forever experimenting and devising tests.the patch
may be release in the recent times.

Is the patch risky and reasonable? what do you think ? Thanks

Best regards
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