On Wed 26-05-21 13:01:42, Feng Tang wrote:
> Now the only remaining case of a real 'local' policy faked by
> 'prefer' policy plus MPOL_F_LOCAL bit is:
>
> A valid 'prefer' policy with a valid 'preferred' node is 'rebind'
> to a nodemask which doesn't contains the 'preferred' node, then it
> will handle allocation with 'local' policy.
>
> Add a new 'MPOL_F_LOCAL_TEMP' bit for this case, and kill the
> MPOL_F_LOCAL bit, which could simplify the code much.
As I've pointed out in the reply to the previous patch. It would have
been much better if most of the MPOL_F_LOCAL usage was gone by this
patch.
I also dislike a new MPOL_F_LOCAL_TEMP. This smells like sneaking the
hack back in after you have painstakingly removed it. So this looks like
a step backwards to me. I also do not understand why do we need the
rebind callback for local policy at all. There is no node mask for local
so what is going on here?
[...]
> +static void mpol_rebind_local(struct mempolicy *pol,
> + const nodemask_t *nodes)
> +{
> + if (unlikely(pol->flags & MPOL_F_STATIC_NODES)) {
> + int node = first_node(pol->w.user_nodemask);
> +
> + BUG_ON(!(pol->flags & MPOL_F_LOCAL_TEMP));
> +
> + if (node_isset(node, *nodes)) {
> + pol->v.preferred_node = node;
> + pol->mode = MPOL_PREFERRED;
> + pol->flags &= ~MPOL_F_LOCAL_TEMP;
> + }
> + }
> +}
> +
I have to confess I've got lost here. Could you explain why do you need
all this handling for a local policy?
> static void mpol_rebind_preferred(struct mempolicy *pol,
> const nodemask_t *nodes)
> {
> @@ -347,13 +363,19 @@ static void mpol_rebind_preferred(struct mempolicy *pol,
>
> if (node_isset(node, *nodes)) {
> pol->v.preferred_node = node;
> - pol->flags &= ~MPOL_F_LOCAL;
> - } else
> - pol->flags |= MPOL_F_LOCAL;
> + } else {
> + /*
> + * If there is no valid node, change the mode to
> + * MPOL_LOCAL, which will be restored back when
> + * next rebind() sees a valid node.
> + */
> + pol->mode = MPOL_LOCAL;
> + pol->flags |= MPOL_F_LOCAL_TEMP;
> + }
> } else if (pol->flags & MPOL_F_RELATIVE_NODES) {
> mpol_relative_nodemask(&tmp, &pol->w.user_nodemask, nodes);
> pol->v.preferred_node = first_node(tmp);
> - } else if (!(pol->flags & MPOL_F_LOCAL)) {
> + } else {
> pol->v.preferred_node = node_remap(pol->v.preferred_node,
> pol->w.cpuset_mems_allowed,
> *nodes);
> @@ -372,7 +394,7 @@ static void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
> {
> if (!pol)
> return;
> - if (!mpol_store_user_nodemask(pol) && !(pol->flags & MPOL_F_LOCAL) &&
> + if (!mpol_store_user_nodemask(pol) &&
> nodes_equal(pol->w.cpuset_mems_allowed, *newmask))
> return;
>
> @@ -425,7 +447,7 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
> },
> [MPOL_LOCAL] = {
> .create = mpol_new_local,
> - .rebind = mpol_rebind_default,
> + .rebind = mpol_rebind_local,
> },
> };
--
Michal Hocko
SUSE Labs
