virtio_balloon: separate vm events into a function

All the VM events related statistics have dependence on
'CONFIG_VM_EVENT_COUNTERS', separate these events into a function to
make code clean. Then we can remove 'CONFIG_VM_EVENT_COUNTERS' from
'update_balloon_stats'.
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Message-Id: <20240423034109.1552866-2-pizhenwei@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>

drivers/virtio/virtio_balloon.c

@@ -349,34 +349,49 @@ static inline void update_stat(struct virtio_balloon *vb, int idx,
 
 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 
-static unsigned int update_balloon_stats(struct virtio_balloon *vb)
+#ifdef CONFIG_VM_EVENT_COUNTERS
+/* Return the number of entries filled by vm events */
+static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
 {
 	unsigned long events[NR_VM_EVENT_ITEMS];
-	struct sysinfo i;
 	unsigned int idx = 0;
-	long available;
-	unsigned long caches;
 
 	all_vm_events(events);
-	si_meminfo(&i);
-
-	available = si_mem_available();
-	caches = global_node_page_state(NR_FILE_PAGES);
-
-#ifdef CONFIG_VM_EVENT_COUNTERS
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
-				pages_to_bytes(events[PSWPIN]));
+		    pages_to_bytes(events[PSWPIN]));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
-				pages_to_bytes(events[PSWPOUT]));
+		    pages_to_bytes(events[PSWPOUT]));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
+
 #ifdef CONFIG_HUGETLB_PAGE
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
 		    events[HTLB_BUDDY_PGALLOC]);
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
 		    events[HTLB_BUDDY_PGALLOC_FAIL]);
-#endif
-#endif
+#endif /* CONFIG_HUGETLB_PAGE */
+
+	return idx;
+}
+#else /* CONFIG_VM_EVENT_COUNTERS */
+static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
+{
+	return 0;
+}
+#endif /* CONFIG_VM_EVENT_COUNTERS */
+
+static unsigned int update_balloon_stats(struct virtio_balloon *vb)
+{
+	struct sysinfo i;
+	unsigned int idx;
+	long available;
+	unsigned long caches;
+
+	idx = update_balloon_vm_stats(vb);
+
+	si_meminfo(&i);
+	available = si_mem_available();
+	caches = global_node_page_state(NR_FILE_PAGES);
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 				pages_to_bytes(i.freeram));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,