[PATCH v4 3/6] mm: Add build time sanity check for struct page size

[Baoquan He]

Size of struct page might be larger than 64 bytes if debug options
enabled, or fields added for debugging intentionally. Yet an upper
limit need be added at build time to trigger an alert in case the
size is too big to boot up system, warning people to check if it's
be done on purpose in advance.

Here 1/4 of PAGE_SIZE is chosen since system must have been insane
with this value. For those systems with PAGE_SIZE larger than 4KB,
1KB is simply taken.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 mm/page_alloc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3eb01dedfb50..eddf96c137f2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -67,6 +67,7 @@
 #include <linux/lockdep.h>
 #include <linux/nmi.h>
 #include <linux/psi.h>
+#include <linux/sizes.h>
 
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
@@ -7170,6 +7171,7 @@ void __init free_area_init_nodes(unsigned long *max_zone_pfn)
 	unsigned long start_pfn, end_pfn;
 	int i, nid;
 
+	BUILD_BUG_ON(sizeof(struct page) > min_t(size_t, SZ_1K, PAGE_SIZE/4));
 	/* Record where the zone boundaries are */
 	memset(arch_zone_lowest_possible_pfn, 0,
 				sizeof(arch_zone_lowest_possible_pfn));
-- 
2.17.2