migration: Make postcopy_requests atomic

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

migration/migration.c

@@ -1152,7 +1152,8 @@ static void populate_ram_info(MigrationInfo *info, MigrationState *s)
         stat64_get(&ram_counters.dirty_sync_count);
     info->ram->dirty_sync_missed_zero_copy =
         stat64_get(&ram_counters.dirty_sync_missed_zero_copy);
-    info->ram->postcopy_requests = ram_counters.postcopy_requests;
+    info->ram->postcopy_requests =
+        stat64_get(&ram_counters.postcopy_requests);
     info->ram->page_size = page_size;
     info->ram->multifd_bytes = stat64_get(&ram_counters.multifd_bytes);
     info->ram->pages_per_second = s->pages_per_second;

migration/ram.c

@@ -2169,7 +2169,7 @@ int ram_save_queue_pages(const char *rbname, ram_addr_t start, ram_addr_t len)
     RAMBlock *ramblock;
     RAMState *rs = ram_state;
 
-    ram_counters.postcopy_requests++;
+    stat64_add(&ram_counters.postcopy_requests, 1);
     RCU_READ_LOCK_GUARD();
 
     if (!rbname) {

migration/ram.h

@@ -49,7 +49,7 @@ typedef struct {
     Stat64 multifd_bytes;
     Stat64 normal;
     Stat64 postcopy_bytes;
-    int64_t postcopy_requests;
+    Stat64 postcopy_requests;
     Stat64 precopy_bytes;
     int64_t remaining;
     Stat64 transferred;