[RFC PATCH v4 03/27] mm/page_alloc: add numa_zone_allowed() and wire it up

Gregory Price
2026-02-22T08:49:06Z

Various locations in mm/ open-code cpuset filtering with:

cpusets_enabled() && ALLOC_CPUSET && !__cpuset_zone_allowed()

This pattern does not account for N_MEMORY_PRIVATE nodes on systems
without cpusets, so private-node zones can leak into allocation
paths that should only see general-purpose memory.

Add numa_zone_allowed() which consolidates zone filtering. It checks
cpuset membership when cpusets are enabled, and otherwise gates
N_MEMORY_PRIVATE zones behind __GFP_PRIVATE globally.

Replace the open-coded patterns in mm/ with the new helper.

Signed-off-by: Gregory Price <gourry@gourry.net>
---
mm/compaction.c | 6 ++----
mm/hugetlb.c | 2 +-
mm/internal.h | 7 +++++++
mm/page_alloc.c | 31 ++++++++++++++++++++-----------
mm/slub.c | 3 ++-
5 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 1e8f8eca318c..6a65145b03d8 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2829,10 +2829,8 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
ac->highest_zoneidx, ac->nodemask) {
enum compact_result status;

- if (cpusets_enabled() &&
- (alloc_flags & ALLOC_CPUSET) &&
- !__cpuset_zone_allowed(zone, gfp_mask))
- continue;
+ if (!numa_zone_alloc_allowed(alloc_flags, zone, gfp_mask))
+ continue;

if (prio > MIN_COMPACT_PRIORITY
&& compaction_deferred(zone, order)) {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 51273baec9e5..f2b914ab5910 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1353,7 +1353,7 @@ static struct folio *dequeue_hugetlb_folio_nodemask(struct hstate *h, gfp_t gfp_
for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(gfp_mask), nmask) {
struct folio *folio;

- if (!cpuset_zone_allowed(zone, gfp_mask))
+ if (!numa_zone_alloc_allowed(ALLOC_CPUSET, zone, gfp_mask))
continue;
/*
* no need to ask again on the same node. Pool is node rather than
diff --git a/mm/internal.h b/mm/internal.h
index 23ee14790227..97023748e6a9 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1206,6 +1206,8 @@ extern int node_reclaim_mode;

extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
extern int find_next_best_node(int node, nodemask_t *used_node_mask);
+extern bool numa_zone_alloc_allowed(int alloc_flags, struct zone *zone,
+ gfp_t gfp_mask);
#else
#define node_reclaim_mode 0

@@ -1218,6 +1220,11 @@ static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
{
return NUMA_NO_NODE;
}
+static inline bool numa_zone_alloc_allowed(int alloc_flags, struct zone *zone,
+ gfp_t gfp_mask)
+{
+ return true;
+}
#endif

static inline bool node_reclaim_enabled(void)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2facee0805da..47f2619d3840 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3690,6 +3690,21 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <=
node_reclaim_distance;
}
+
+/* Returns true if allocation from this zone is permitted */
+bool numa_zone_alloc_allowed(int alloc_flags, struct zone *zone, gfp_t gfp_mask)
+{
+ /* Gate N_MEMORY_PRIVATE zones behind __GFP_PRIVATE */
+ if (!(gfp_mask & __GFP_PRIVATE) &&
+ node_state(zone_to_nid(zone), N_MEMORY_PRIVATE))
+ return false;
+
+ /* If cpusets is being used, check mems_allowed */
+ if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET))
+ return cpuset_zone_allowed(zone, gfp_mask);
+
+ return true;
+}
#else /* CONFIG_NUMA */
static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
{
@@ -3781,10 +3796,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
struct page *page;
unsigned long mark;

- if (cpusets_enabled() &&
- (alloc_flags & ALLOC_CPUSET) &&
- !__cpuset_zone_allowed(zone, gfp_mask))
- continue;
+ if (!numa_zone_alloc_allowed(alloc_flags, zone, gfp_mask))
+ continue;
/*
* When allocating a page cache page for writing, we
* want to get it from a node that is within its dirty
@@ -4585,10 +4598,8 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
unsigned long min_wmark = min_wmark_pages(zone);
bool wmark;

- if (cpusets_enabled() &&
- (alloc_flags & ALLOC_CPUSET) &&
- !__cpuset_zone_allowed(zone, gfp_mask))
- continue;
+ if (!numa_zone_alloc_allowed(alloc_flags, zone, gfp_mask))
+ continue;

available = reclaimable = zone_reclaimable_pages(zone);
available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
@@ -5084,10 +5095,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
for_next_zone_zonelist_nodemask(zone, z, ac.highest_zoneidx, ac.nodemask) {
unsigned long mark;

- if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) &&
- !__cpuset_zone_allowed(zone, gfp)) {
+ if (!numa_zone_alloc_allowed(alloc_flags, zone, gfp))
continue;
- }

if (nr_online_nodes > 1 && zone != zonelist_zone(ac.preferred_zoneref) &&
zone_to_nid(zone) != zonelist_node_idx(ac.preferred_zoneref)) {
diff --git a/mm/slub.c b/mm/slub.c
index 861592ac5425..e4bd6ede81d1 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3595,7 +3595,8 @@ static struct slab *get_any_partial(struct kmem_cache *s,

n = get_node(s, zone_to_nid(zone));

- if (n && cpuset_zone_allowed(zone, pc->flags) &&
+ if (n && numa_zone_alloc_allowed(ALLOC_CPUSET, zone,
+ pc->flags) &&
n->nr_partial > s->min_partial) {
slab = get_partial_node(s, n, pc);
if (slab) {
--
2.53.0