On Sun 18-09-16 13:29:43, Piotr Kwapulinski wrote:
> The MPOL_F_STATIC_NODES and MPOL_F_RELATIVE_NODES flags are irrelevant
> when setting them for MPOL_LOCAL NUMA memory policy via set_mempolicy.
> Return the "invalid argument" from set_mempolicy whenever
> any of these flags is passed along with MPOL_LOCAL.
man 2 set_mempolicy doesn't list this as invalid option. Maybe this is a
documentation bug but is it possible that somebody will see this as an
unexpected error?
> It is consistent with MPOL_PREFERRED passed with empty nodemask.
> It also slightly shortens the execution time in paths where these flags
> are used e.g. when trying to rebind the NUMA nodes for changes in
> cgroups cpuset mems (mpol_rebind_preferred()) or when just printing
> the mempolicy structure (/proc/PID/numa_maps).
I am not sure I understand this argument. What does this patch actually
fix? If this is about the execution time then why not just bail out
early when MPOL_LOCAL && (MPOL_F_STATIC_NODES || MPOL_F_RELATIVE_NODES)
> Isolated tests done.
>
> Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@xxxxxxxxx>
> ---
> mm/mempolicy.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 2da72a5..27b07d1 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -276,7 +276,9 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags,
> return ERR_PTR(-EINVAL);
> }
> } else if (mode == MPOL_LOCAL) {
> - if (!nodes_empty(*nodes))
> + if (!nodes_empty(*nodes) ||
> + (flags & MPOL_F_STATIC_NODES) ||
> + (flags & MPOL_F_RELATIVE_NODES))
> return ERR_PTR(-EINVAL);
> mode = MPOL_PREFERRED;
> } else if (nodes_empty(*nodes))
> --
> 2.9.2
--
Michal Hocko
SUSE Labs
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