linux-kernel - [PATCH] mm: Strictly check vmstat

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Message-ID: <20250529110541.2960330-1-kirill.shutemov@linux.intel.com>
Date: Thu, 29 May 2025 14:05:41 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>
Cc: lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	vbabka@...e.cz,
	rppt@...nel.org,
	surenb@...gle.com,
	mhocko@...e.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>
Subject: [PATCH] mm: Strictly check vmstat_text array size

The /proc/vmstat displays counters from various sources. It is easy to
forget to add or remove a label when a new counter is added or removed.

There is a BUILD_BUG_ON() function that catches missing labels. However,
for some reason, it ignores extra labels.

Let's make the check strict. This would help to catch issues when
a counter is removed.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@...il.com>
---
 mm/vmstat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index ae9882063d89..0903adace423 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1867,7 +1867,7 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
 	if (*pos >= NR_VMSTAT_ITEMS)
 		return NULL;
 
-	BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) < NR_VMSTAT_ITEMS);
+	BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) != NR_VMSTAT_ITEMS);
 	fold_vm_numa_events();
 	v = kmalloc_array(NR_VMSTAT_ITEMS, sizeof(unsigned long), GFP_KERNEL);
 	m->private = v;
-- 
2.47.2