Re: [PATCH 1/7] shared subtree

Miklos Szeredi
2005-07-28T09:58:55Z

> > This is an example, where having struct pnode just complicates things.
> > If there was no struct pnode, this function would be just one line:
> > setting the shared flag.
> So your comment is mostly about getting rid of pnode and distributing
> the pnode functionality in the vfsmount structure.

Yes, sorry if I didn't make it clear.

> I know you are thinking of just having the necessary propogation list in
> the vfsmount structure itself. Yes true with that implementation the
> complication is reduced in this part of the code, but really complicates
> the propogation traversal routines.

On the contrary, I think it will simplify the traversal routines.

Here's an iterator function I coded up. Not tested at all (may not
even compile):

struct vfsmount {
/* ... */

struct list_head mnt_share; /* circular list of shared mounts */
struct list_head mnt_slave_list; /* list of slave mounts */
struct list_head mnt_slave; /* slave list entry */
struct vfsmount *master; /* slave is on master->mnt_slave_list */
};

static inline struct vfsmount *next_shared(struct vfsmount *p)
{
return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
}

static inline struct vfsmount *first_slave(struct vfsmount *p)
{
return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);
}

static inline struct vfsmount *next_slave(struct vfsmount *p)
{
return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
}

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);

while (1) {
struct vfsmount *q;

/* more vfsmounts belong to the pnode? */
if (!list_empty(&p->mnt_share)) {
p = next_shared(p);
if (list_empty(&p->mnt_slave) && p != base)
return p;
}
if (p == base)
break;

BUG_ON(list_empty(&p->mnt_slave));

/* more slaves? */
q = next_slave(p);
if (p->master != q)
return q;

/* back at master */
p = q;
}

return NULL;
}