[patch 03/86] mm/vmstat: add helpers to get vmstat item names for each enum type

[Andrew Morton <akpm@linux-foundation.org>]

From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Subject: mm/vmstat: add helpers to get vmstat item names for each enum type

Statistics in vmstat is combined from counters with different structure,
but names for them are merged into one array.

This patch adds trivial helpers to get name for each item:

const char *zone_stat_name(enum zone_stat_item item);
const char *numa_stat_name(enum numa_stat_item item);
const char *node_stat_name(enum node_stat_item item);
const char *writeback_stat_name(enum writeback_stat_item item);
const char *vm_event_name(enum vm_event_item item);

Names for enum writeback_stat_item are folded in the middle of vmstat_text
so this patch moves declaration into header to calculate offset of
following items.

Also this patch reuses piece of node stat names for lru list names:

const char *lru_list_name(enum lru_list lru);

This returns common lru list names: "inactive_anon", "active_anon",
"inactive_file", "active_file", "unevictable".

[khlebnikov@yandex-team.ru: do not use size of vmstat_text as count of /proc/vmstat items]
  Link: http://lkml.kernel.org/r/157152151769.4139.15423465513138349343.stgit@buzz
  Link: https://lore.kernel.org/linux-mm/cd1c42ae-281f-c8a8-70ac-1d01d417b2e1@infradead.org/T/#u
Link: http://lkml.kernel.org/r/157113012325.453.562783073839432766.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: YueHaibing <yuehaibing@huawei.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/base/node.c    |    9 ++----
 include/linux/vmstat.h |   50 ++++++++++++++++++++++++++++++++++++++
 mm/vmstat.c            |   51 +++++++++++++++------------------------
 3 files changed, 73 insertions(+), 37 deletions(-)

--- a/drivers/base/node.c~mm-vmstat-add-helpers-to-get-vmstat-item-names-for-each-enum-type
+++ a/drivers/base/node.c
@@ -496,20 +496,17 @@ static ssize_t node_read_vmstat(struct d
 	int n = 0;
 
 	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
-		n += sprintf(buf+n, "%s %lu\n", vmstat_text[i],
+		n += sprintf(buf+n, "%s %lu\n", zone_stat_name(i),
 			     sum_zone_node_page_state(nid, i));
 
 #ifdef CONFIG_NUMA
 	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
-		n += sprintf(buf+n, "%s %lu\n",
-			     vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
+		n += sprintf(buf+n, "%s %lu\n", numa_stat_name(i),
 			     sum_zone_numa_state(nid, i));
 #endif
 
 	for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
-		n += sprintf(buf+n, "%s %lu\n",
-			     vmstat_text[i + NR_VM_ZONE_STAT_ITEMS +
-			     NR_VM_NUMA_STAT_ITEMS],
+		n += sprintf(buf+n, "%s %lu\n", node_stat_name(i),
 			     node_page_state(pgdat, i));
 
 	return n;
--- a/include/linux/vmstat.h~mm-vmstat-add-helpers-to-get-vmstat-item-names-for-each-enum-type
+++ a/include/linux/vmstat.h
@@ -31,6 +31,12 @@ struct reclaim_stat {
 	unsigned nr_unmap_fail;
 };
 
+enum writeback_stat_item {
+	NR_DIRTY_THRESHOLD,
+	NR_DIRTY_BG_THRESHOLD,
+	NR_VM_WRITEBACK_STAT_ITEMS,
+};
+
 #ifdef CONFIG_VM_EVENT_COUNTERS
 /*
  * Light weight per cpu counter implementation.
@@ -381,4 +387,48 @@ static inline void __mod_zone_freepage_s
 
 extern const char * const vmstat_text[];
 
+static inline const char *zone_stat_name(enum zone_stat_item item)
+{
+	return vmstat_text[item];
+}
+
+#ifdef CONFIG_NUMA
+static inline const char *numa_stat_name(enum numa_stat_item item)
+{
+	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+			   item];
+}
+#endif /* CONFIG_NUMA */
+
+static inline const char *node_stat_name(enum node_stat_item item)
+{
+	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+			   NR_VM_NUMA_STAT_ITEMS +
+			   item];
+}
+
+static inline const char *lru_list_name(enum lru_list lru)
+{
+	return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
+}
+
+static inline const char *writeback_stat_name(enum writeback_stat_item item)
+{
+	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+			   NR_VM_NUMA_STAT_ITEMS +
+			   NR_VM_NODE_STAT_ITEMS +
+			   item];
+}
+
+#ifdef CONFIG_VM_EVENT_COUNTERS
+static inline const char *vm_event_name(enum vm_event_item item)
+{
+	return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
+			   NR_VM_NUMA_STAT_ITEMS +
+			   NR_VM_NODE_STAT_ITEMS +
+			   NR_VM_WRITEBACK_STAT_ITEMS +
+			   item];
+}
+#endif /* CONFIG_VM_EVENT_COUNTERS */
+
 #endif /* _LINUX_VMSTAT_H */
--- a/mm/vmstat.c~mm-vmstat-add-helpers-to-get-vmstat-item-names-for-each-enum-type
+++ a/mm/vmstat.c
@@ -1134,7 +1134,7 @@ const char * const vmstat_text[] = {
 	"numa_other",
 #endif
 
-	/* Node-based counters */
+	/* enum node_stat_item counters */
 	"nr_inactive_anon",
 	"nr_active_anon",
 	"nr_inactive_file",
@@ -1564,10 +1564,8 @@ static void zoneinfo_show_print(struct s
 	if (is_zone_first_populated(pgdat, zone)) {
 		seq_printf(m, "\n  per-node stats");
 		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
-			seq_printf(m, "\n      %-12s %lu",
-				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS +
-				NR_VM_NUMA_STAT_ITEMS],
-				node_page_state(pgdat, i));
+			seq_printf(m, "\n      %-12s %lu", node_stat_name(i),
+				   node_page_state(pgdat, i));
 		}
 	}
 	seq_printf(m,
@@ -1600,14 +1598,13 @@ static void zoneinfo_show_print(struct s
 	}
 
 	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
-		seq_printf(m, "\n      %-12s %lu", vmstat_text[i],
-				zone_page_state(zone, i));
+		seq_printf(m, "\n      %-12s %lu", zone_stat_name(i),
+			   zone_page_state(zone, i));
 
 #ifdef CONFIG_NUMA
 	for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
-		seq_printf(m, "\n      %-12s %lu",
-				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
-				zone_numa_state_snapshot(zone, i));
+		seq_printf(m, "\n      %-12s %lu", numa_stat_name(i),
+			   zone_numa_state_snapshot(zone, i));
 #endif
 
 	seq_printf(m, "\n  pagesets");
@@ -1658,31 +1655,23 @@ static const struct seq_operations zonei
 	.show	= zoneinfo_show,
 };
 
-enum writeback_stat_item {
-	NR_DIRTY_THRESHOLD,
-	NR_DIRTY_BG_THRESHOLD,
-	NR_VM_WRITEBACK_STAT_ITEMS,
-};
+#define NR_VMSTAT_ITEMS (NR_VM_ZONE_STAT_ITEMS + \
+			 NR_VM_NUMA_STAT_ITEMS + \
+			 NR_VM_NODE_STAT_ITEMS + \
+			 NR_VM_WRITEBACK_STAT_ITEMS + \
+			 (IS_ENABLED(CONFIG_VM_EVENT_COUNTERS) ? \
+			  NR_VM_EVENT_ITEMS : 0))
 
 static void *vmstat_start(struct seq_file *m, loff_t *pos)
 {
 	unsigned long *v;
-	int i, stat_items_size;
+	int i;
 
-	if (*pos >= ARRAY_SIZE(vmstat_text))
+	if (*pos >= NR_VMSTAT_ITEMS)
 		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
 
-	BUILD_BUG_ON(stat_items_size !=
-		     ARRAY_SIZE(vmstat_text) * sizeof(unsigned long));
-	v = kmalloc(stat_items_size, GFP_KERNEL);
+	BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) < NR_VMSTAT_ITEMS);
+	v = kmalloc_array(NR_VMSTAT_ITEMS, sizeof(unsigned long), GFP_KERNEL);
 	m->private = v;
 	if (!v)
 		return ERR_PTR(-ENOMEM);
@@ -1715,7 +1704,7 @@ static void *vmstat_start(struct seq_fil
 static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
 {
 	(*pos)++;
-	if (*pos >= ARRAY_SIZE(vmstat_text))
+	if (*pos >= NR_VMSTAT_ITEMS)
 		return NULL;
 	return (unsigned long *)m->private + *pos;
 }
@@ -1781,7 +1770,7 @@ int vmstat_refresh(struct ctl_table *tab
 		val = atomic_long_read(&vm_zone_stat[i]);
 		if (val < 0) {
 			pr_warn("%s: %s %ld\n",
-				__func__, vmstat_text[i], val);
+				__func__, zone_stat_name(i), val);
 			err = -EINVAL;
 		}
 	}
@@ -1790,7 +1779,7 @@ int vmstat_refresh(struct ctl_table *tab
 		val = atomic_long_read(&vm_numa_stat[i]);
 		if (val < 0) {
 			pr_warn("%s: %s %ld\n",
-				__func__, vmstat_text[i + NR_VM_ZONE_STAT_ITEMS], val);
+				__func__, numa_stat_name(i), val);
 			err = -EINVAL;
 		}
 	}
_