Re: Add a norecovery option to ext3/4?

Phillip Susi
2007-04-09T15:42:13Z

Samuel Thibault wrote:
> Hi,
>
> Distribution installers usually try to probe OSes for building a suited
> grub menu. Unfortunately, mounting an ext3 partition, even in read-only
> mode, does perform some operations on the filesystem (log recovery).
> This is not a good idea since it may silently garbage data. XFS has a
> norecovery option that allows to disable that, I'd say ext3/4 should
> have it too.

When the filesystem is told to mount the disk read only, that means it
should not write to it. The fact that ext3 goes ahead and does anyway
is a bug and should be fixed. There is no need for a norecovery option,
because read only is a sufficient directive to tell the filesystem not
to write to the disk.

As someone else pointed out, this behavior causes havoc if you hibernate
a system and then boot up another system which mounts the disk of the
hibernated system. Under all conditions it should be safe to mount a
disk read only, but here it is not because the journal playback trashes
the disk out from under the hibernated system.