On Fri 19-06-20 09:24:08, Ben Widawsky wrote:
> MPOL_LOCAL is a bit weird because it is simply a different name for an
> existing behavior (preferred policy with no node mask). It has been this
> way since it was added here:
> commit 479e2802d09f ("mm: mempolicy: Make MPOL_LOCAL a real policy")
>
> It is so similar to MPOL_PREFERRED in fact that when the policy is
> created in mpol_new, the mode is set as PREFERRED, and an internal state
> representing LOCAL doesn't exist.
>
> To prevent future explorers from scratching their head as to why
> MPOL_LOCAL isn't defined in the mpol_ops table, add a small comment
> explaining the situations.
Agreed. MPOL_LOCAL can be really confusing for whoever looks at the code
the first time.
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/mempolicy.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 381320671677..36ee3267c25f 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -427,6 +427,7 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
> .create = mpol_new_bind,
> .rebind = mpol_rebind_nodemask,
> },
> + /* MPOL_LOCAL is converted to MPOL_PREFERRED on policy creation */
I would just add. See mpol_new()
> };
>
> static int migrate_page_add(struct page *page, struct list_head *pagelist,
> --
> 2.27.0
>
--
Michal Hocko
SUSE Labs
