Re: [RFC] shared subtrees

[J. Bruce Fields]

On Mon, Jan 17, 2005 at 03:11:18PM -0500, Mike Waychison wrote:
> I don't think that solves the problem.  B should receive copies (with
> shared semantics if called for) of all mountpoints C1,..,Cn that are
> children of A if A->A.  This is regardless of whether or not propagation
> occurs before or after the attach.

Consider this situation:
# #make new vfsmounts at /foo and /bar:
# mount --bind /foo /foo
# mount --bind /bar /bar
# # mount /bar under /foo, *then* put /bar and /mnt2 in the same p-node:
# mount --bind /bar /foo/mnt1
# mount --make-shared /foo
# mount --bind /foo /mnt2
# find # and I think this is what you'll get:
.
./foo
./bar
./bar/file_in_bar
./foo/mnt1
./foo/mnt1/file_in_bar
./mnt2/
./mnt2/mnt1/

Since /mnt2 and /foo are in the same p-node, any mounts we may make
under them later will be shared.  But the mount under under /foo/mnt1 is
*not* automatically propagated to /mnt2/mnt1, and /mnt1 is still in its
own little p-node (so mounts under it won't be replicated).

At least, I think I have that right.

In any case, setting up propagation between two vfsmounts needn't force
propagation of preexisting mounts, it need only affect mounts made later.

--b.
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