tree 0ab3e5ae91e803ae00cc8a9e19701ee9cc63e49f
parent 67a991a89e5b28dabf8372017b2b33e67585e6c4
author Eric W. Biederman <ebiederm@xmission.com> 1268016576 -0800
committer Eric W. Biederman <ebiederm@aristanetworks.com> 1312829436 -0500

ns proc: Add support for the mount namespace

setns support for the mount namespace is a little tricky as an
arbitrary decision must be made about what to set fs->root and
fs->pwd to, as there is no expectation of a relationship between
the two mount namespaces.  Therefore I arbitrarily find the root
mount point, and follow every mount on top of it to find the top
of the mount stack.  Then I set fs->root and fs->pwd to that
location.  The topmost root of the mount stack seems like a
reasonable place to be.

Bind mount support for the mount namespace inodes has the
possibility of creating circular dependencies between mount
namespaces.  Circular dependencies can result in loops that
prevent mount namespaces from every being freed.  I avoid
creating those circular dependencies by adding a sequence number
to the mount namespace and require all bind mounts be of a
younger mount namespace into an older mount namespace.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>