[no subject]

From: Ram Pai
Date: Mon Jul 25 2005 - 18:25:43 EST

, miklos@xxxxxxxxxx, Janak Desai <janak@xxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH 0/7] shared subtree

Hi Andrew/Al Viro,

Enclosing a final set of well tested patches that implement
Al Viro's shared subtree proposal.

These patches provide the ability to mark a mount tree as
shared/private/slave/unclone, along with the ability to play with these
trees with operations like bind/rbind/move/pivot_root/namespace-clone

I believe this powerful feature can help build features like
per-user namespace. Couple of projects may benefit from
shared subtrees.
1) automounter for the ability to automount across namespaces.
2) SeLinux for implementing polyinstantiated trees.
3) MVFS for providing versioning file system.
4) FUSE for per-user namespaces?

Thanks to Avantika for developing about 100+ test cases that tests
various combintation of private/shared/slave/unclonable trees. All
these tests have passed. I feel pretty confident about the stability of
the code.

The patches have been broken into 7 units, for ease of review. I
realize that patch-3 'rbind.patch' is a bit heavier than all the other
patches. The reason being, most of the shared-subtree functionality
gets manifestated during bind/rbind operation.

Couple of work items to be done are:
1. modify the mount command to support this feature
eg: mount --make-shared /tmp
2. a tool that can help visualize the propogation tree, maybe
support in /proc?
3. some documentation on how to use all this functionality.

Please consider the patches for inclusion in your tree.

The footprint of this code is pretty small in the normal code path
where shared-subtree functionality is not used.

Any suggestions/comments to improve the code is welcome.

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