Re: [PATCH 01/18] kernel: add bl_list

Dave Chinner
2010-10-08T10:33:57Z

On Fri, Oct 08, 2010 at 10:18:40AM +0200, Andi Kleen wrote:
> Dave Chinner <david@fromorbit.com> writes:
>
> > +static inline void __hlist_bl_del(struct hlist_bl_node *n)
> > +{
> > + struct hlist_bl_node *next = n->next;
> > + struct hlist_bl_node **pprev = n->pprev;
> > +
> > + LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
> > +
> > + /* pprev may be `first`, so be careful not to lose the lock bit */
> > + *pprev = (struct hlist_bl_node *)
> > + ((unsigned long)next |
> > + ((unsigned long)*pprev & LIST_BL_LOCKMASK));
> > + if (next)
> > + next->pprev = pprev;
> > +}
>
> Should this set n->pprev to NULL so that unhashed returns true
> afterwards?

No, I think the callers set that appropriately.

> > +
> > +static inline void hlist_bl_del(struct hlist_bl_node *n)
> > +{
> > + __hlist_bl_del(n);
> > + n->next = BL_LIST_POISON1;
> > + n->pprev = BL_LIST_POISON2;
> > +}
>
> Ok so unhashed only works once. Seems unsymmetric.

Exactly the same behaviour as hlist_del(). If you want
hlist_bl_unhashed() to work, you need to call hlist_bl_del_init().

/me makes a note to check all the inode hash code uses hlist_bl_del_init()
as there are unhashed checks in many places.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com