Messages in this thread | | | Date | Fri, 14 Jan 2005 00:19:20 +0000 | From | Al Viro <> | Subject | Re: [RFC] shared subtrees |
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On Thu, Jan 13, 2005 at 06:30:50PM -0500, Mike Waychison wrote: > > 1) each p-node corresponds to a group of 1 or more vfsmounts. > > 2) there is at most 1 p-node containing a given vfsmount. > > 3) each p-node owns a possibly empty set of p-nodes and vfsmounts > > 4) no p-node or vfsmount can be owned by more than one p-node > > 5) only vfsmounts that are not contained in any p-nodes might be owned. > > 6) no p-node can own (directly or via intermediates) itself (i.e. the > > graph of p-node ownership is a forest). > > > > These guys define propagation: > > a) if vfsmounts A and B are contained in the same p-node, events > > propagate from A to B > > b) if vfsmount A is contained in p-node p, vfsmount B is contained > > in p-node q and p owns q, events propagate from A to B > > c) if vfsmount A is contained in p-node p and vfsmount B is owned > > by p, events propagate from A to B > > How is (c) different from (a)? Is there a distinction between > 'containing' and 'owning' here?
Yes. See (3) and (1) above. Consider the following: p = {A, B} p owns C Then we have propagation between A and B _and_ from either to C.
> > * we can mark a subtree slave. That removes all vfsmounts in > > the subtree from their p-nodes and makes them owned by said p-nodes. > > p-nodes that became empty will disappear and everything they used to > > own will be repossessed by their owners (if any). > > Would this be better read as "That removes each vfsmount A in the > subtree from its respective p-node p and makes it contained by a new > p-node p' (containing only A), and p' becomes 'owned' by p." ?
No. "Belongs to a single-element p-node" != "doesn't belong to any p-node". The former means "share on copy" (and might have slaves). The latter is noone's master. Again, see the propagation rules and behaviour on clone/rbind.
> > * if V is contained in some p-node p, A is placed into the same > > p-node. That may require merging one of the p-nodes we'd just created > > with p (that will be the counterpart of the p-node containing the mountpoint). > > * if V is owned by some p-node p, then A (or p-node containing A) > > becomes owned by p. > > I don't follow this. I still don't see the distinction between being > owned and being contained. Also, for statements like 'A belongs to B', > which is it?
"V owned by p" == "V is a slave of (equivelent) members of p" "p contains V" == "V is one of the members of p, whatever happens to it will happen to all of them".
"element belongs to set" means what it usually means ;-) (again, p-nodes are sets of vfsmounts). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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