mm: strictly check vmstat_text array size

/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.

Link: https://lkml.kernel.org/r/20250529110541.2960330-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill A. Shuemov <kirill.shutemov@linux.intel.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 01d76216d65a2b7868d7fed619a8810335d1da29..41f6a64e5c39f57cf78ee1348d252b922e4bf31f 100644 (file)
--- 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;