[RFC] ext3 multi-mount protection

Is there any ext3/ext4 interest in a mechanism for protecting ext3/ext4
filesystems from being mounted concurrently by multiple nodes on a SAN
at the same time?

We often run the ext3 server filesystems in an HA configuration so that
there are two servers on a FC switch that can access the same shared
disk.  Sadly, HA software is far from reliable and this can sometimes
lead to both servers trying to access the same device at one time.
This is true if you are using ext3 for HA NFS serving, or other non-HA
setups where the same disks are accessible by multiple nodes (regardless
of whether they are _supposed_ to touch those disks or not), because the
ext3 journal recovery can corrupt the filesystem even if mounted read-only,
or if some clueless sysadmin tries to mount or use "those unused disks".

We've developed a small patch for ext3 to prevent the filesystem from
being mounted concurrently on two nodes.  Is there general interest in
this becoming part of ext3/ext4?

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.



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