On Wed 17-03-21 11:40:01, Feng Tang wrote:
> From: Dave Hansen <dave.han...@linux.intel.com>
>
> Create a helper function (mpol_new_preferred_many()) which is usable
> both by the old, single-node MPOL_PREFERRED and the new
> MPOL_PREFERRED_MANY.
>
> Enforce the old single-node MPOL_PREFERRED behavior in the "new"
> version of mpol_new_preferred() which calls mpol_new_preferred_many().
>
> v3:
> * fix a stack overflow caused by emty nodemask (Feng)
>
> Link: https://lore.kernel.org/r/20200630212517.308045-5-ben.widaw...@intel.com
> Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
> Signed-off-by: Ben Widawsky <ben.widaw...@intel.com>
> Signed-off-by: Feng Tang <feng.t...@intel.com>
> ---
> mm/mempolicy.c | 21 +++++++++++++++++++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 1228d8e..6fb2cab 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -203,17 +203,34 @@ static int mpol_new_interleave(struct mempolicy *pol,
> const nodemask_t *nodes)
> return 0;
> }
>
> -static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
> +static int mpol_new_preferred_many(struct mempolicy *pol,
> + const nodemask_t *nodes)
> {
> if (!nodes)
> pol->flags |= MPOL_F_LOCAL; /* local allocation */
Now you have confused me. I thought that MPOL_PREFERRED_MANY for NULL
nodemask will be disallowed as it is effectively MPOL_PREFERRED aka
MPOL_F_LOCAL. Or do I misread the code?
> else if (nodes_empty(*nodes))
> return -EINVAL; /* no allowed nodes */
> else
> - pol->v.preferred_nodes = nodemask_of_node(first_node(*nodes));
> + pol->v.preferred_nodes = *nodes;
> return 0;
> }
>
> +static int mpol_new_preferred(struct mempolicy *pol, const nodemask_t *nodes)
> +{
> + if (nodes) {
> + /* MPOL_PREFERRED can only take a single node: */
> + nodemask_t tmp;
> +
> + if (nodes_empty(*nodes))
> + return -EINVAL;
> +
> + tmp = nodemask_of_node(first_node(*nodes));
> + return mpol_new_preferred_many(pol, &tmp);
> + }
> +
> + return mpol_new_preferred_many(pol, NULL);
> +}
> +
> static int mpol_new_bind(struct mempolicy *pol, const nodemask_t *nodes)
> {
> if (nodes_empty(*nodes))
> --
> 2.7.4
--
Michal Hocko
SUSE Labs
