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Subject[PATCH] mm: detect numbers of vmstat keys/values mismatch
Date
There were mismatches between number of vmstat keys and number of
vmstat values. They were fixed recently by:
commit 58bc4c34d249 ("mm/vmstat.c: skip NR_TLB_REMOTE_FLUSH* properly")
commit 28e2c4bb99aa ("mm/vmstat.c: fix outdated vmstat_text")

Add a BUILD_BUG_ON to detect such mismatch and hopefully prevent
it from happening again.

Signed-off-by: Yu Zhao <yuzhao@google.com>
---
include/linux/vmstat.h | 4 ++++
mm/vmstat.c | 18 ++++++++----------
2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index f25cef84b41d..33fdd37124cb 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -78,6 +78,10 @@ extern void vm_events_fold_cpu(int cpu);

#else

+struct vm_event_state {
+ unsigned long event[0];
+};
+
/* Disable counters */
static inline void count_vm_event(enum vm_event_item item)
{
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 7878da76abf2..7ebf871b4cc9 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1647,23 +1647,21 @@ enum writeback_stat_item {
NR_VM_WRITEBACK_STAT_ITEMS,
};

+#define NR_VM_STAT_ITEMS (NR_VM_ZONE_STAT_ITEMS + NR_VM_NUMA_STAT_ITEMS + \
+ NR_VM_NODE_STAT_ITEMS + NR_VM_WRITEBACK_STAT_ITEMS + \
+ ARRAY_SIZE(((struct vm_event_state *)0)->event))
+
static void *vmstat_start(struct seq_file *m, loff_t *pos)
{
+ int i;
unsigned long *v;
- int i, stat_items_size;
+
+ BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) != NR_VM_STAT_ITEMS);

if (*pos >= ARRAY_SIZE(vmstat_text))
return NULL;
- stat_items_size = NR_VM_ZONE_STAT_ITEMS * sizeof(unsigned long) +
- NR_VM_NUMA_STAT_ITEMS * sizeof(unsigned long) +
- NR_VM_NODE_STAT_ITEMS * sizeof(unsigned long) +
- NR_VM_WRITEBACK_STAT_ITEMS * sizeof(unsigned long);
-
-#ifdef CONFIG_VM_EVENT_COUNTERS
- stat_items_size += sizeof(struct vm_event_state);
-#endif

- v = kmalloc(stat_items_size, GFP_KERNEL);
+ v = kmalloc_array(NR_VM_STAT_ITEMS, sizeof(unsigned long), GFP_KERNEL);
m->private = v;
if (!v)
return ERR_PTR(-ENOMEM);
--
2.19.1.331.ge82ca0e54c-goog
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