mm/hugetlb: check bootmem pages for zone intersections

Bootmem hugetlb pages are allocated using memblock, which isn't (and
mostly can't be) aware of zones.

So, they may end up crossing zone boundaries.  This would create
confusion, a hugetlb page that is part of multiple zones is bad.  Worse,
HVO might then end up stealthily re-assigning pages to a different zone
when a hugetlb page is freed, since the tail page structures beyond the
first vmemmap page would inherit the zone of the first page structures.

While the chance of this happening is low, you can definitely create a
configuration where this happens (especially using ZONE_MOVABLE).

To avoid this issue, check if bootmem hugetlb pages intersect with
multiple zones during the gather phase, and discard them, handing them to
the page allocator, if they do.  Record the number of invalid bootmem
pages per node and subtract them from the number of available pages at the
end, making it easier to do these checks in multiple places later on.

Link: https://lkml.kernel.org/r/20250228182928.2645936-14-fvdl@google.com
Signed-off-by: Frank van der Linden <fvdl@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 419b7db220d2..3eec528afe43 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2287,6 +2287,31 @@ void set_zone_contiguous(struct zone *zone)
 	zone->contiguous = true;
 }
 
+/*
+ * Check if a PFN range intersects multiple zones on one or more
+ * NUMA nodes. Specify the @nid argument if it is known that this
+ * PFN range is on one node, NUMA_NO_NODE otherwise.
+ */
+bool pfn_range_intersects_zones(int nid, unsigned long start_pfn,
+			   unsigned long nr_pages)
+{
+	struct zone *zone, *izone = NULL;
+
+	for_each_zone(zone) {
+		if (nid != NUMA_NO_NODE && zone_to_nid(zone) != nid)
+			continue;
+
+		if (zone_intersects(zone, start_pfn, nr_pages)) {
+			if (izone != NULL)
+				return true;
+			izone = zone;
+		}
+
+	}
+
+	return false;
+}
+
 static void __init mem_init_print_info(void);
 void __init page_alloc_init_late(void)
 {