[RFC] Filesystem with multiple mount-points

[Guennadi Liakhovetski]

Hi

Disclaimer: I am not a filesystem expert, so, what's below might be
absolute nonsense.

There are systems, where it is desirable to make some partitions,
possibly, including root, read-only, and some other, like, e.g., /var,
/home, /lib/modules read-writable. Those writable filesystems may be quite
small, so, putting them on separate partitions creates too much overhead
for filesystem metadata, journals... Making those directories soft-links
into one writable partition would work, but is not too nice.

So, how about adding a multiple mount-point option to some filesystem?
They would share metadata, journals, would be represented by several
directory-trees, and be mountable with, e.g.

mount -otree1 /dev/hda1 /var

or

mount /dev/hda1:1 /var

which, however, would be incompatible with older versions. /proc/mounts
would show something like

/dev/hda1:1 /var ...

df might just show tree1 - to maintain backwards compatibility. Later
mount and df could be tought to support this option natively.

Makes any sense at all?

Thanks
Guennadi
---
Guennadi Liakhovetski


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