Re: [PATCH 1/7] shared subtree

From: Miklos Szeredi
Date: Sat Jul 30 2005 - 00:42:05 EST

> > static struct vfsmount *propagation_next(struct vfsmount *p,
> > struct vfsmount *base)
> > {
> > /* first iterate over the slaves */
> > if (!list_empty(&p->mnt_slave_list))
> > return first_slave(p);
> I think this code should be
> if (!list_empty(&p->mnt_slave))
> return next_slave(p);
> Right? I think I get the idea.

This is a depth-first search, so first_slave() is right.

Here's a less buggy (and even more simplified) version of the
function. Note: it must be called with 'origin' either on a slave
list or at the root pnode. That's because the function checks if the
all vfsmounts in a pnode have been traversed by looking at the
emptiness of mnt_slave. So if origin was in a slave pnode, but is not
the actual slave link, the algorithm will go off the starting pnode
and up to it's master.

So here's a preparation function that finds the right place to start
the propagation.

static struct vfsmount *propagation_first(struct vfsmount *p)
struct vfsmount *q = p;

while (list_empty(&q->mnt_slave)) {
q = next_shared(q);
if (q == p)
return q;

static struct vfsmount *propagation_next(struct vfsmount *p,
struct vfsmount *origin)
/* are there any slaves of this mount? */
if (!list_empty(&p->mnt_slave_list))
return first_slave(p);

while (1) {
/* if p->mnt_share is empty, this is a no-op */
p = next_shared(p);

/* finished traversing? */
if (p == origin)

/* more vfsmounts belong to the pnode? */
if (list_empty(&p->mnt_slave))
return p;

/* more slaves? */
if (p-> != &p->mnt_master->mnt_slave_list)
return next_slave(p);

/* back at master */
p = p->mnt_master;

return NULL;

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