add a version number to ram_list

This will be used to detect if last_block might have become invalid
across different calls to ram_save_live.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Umesh Deshpande <udeshpan@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

Reviewed-by: Orit Wasserman <owasserm@redhat.com>

exec.c

diff --git a/exec.c b/exec.c
index 1ee4fa6..8478bef 100644
--- a/exec.c
+++ b/exec.c
@@ -1056,6 +1056,8 @@
     }
     ram_list.mru_block = NULL;
 
+    ram_list.version++;
+
     ram_list.phys_dirty = g_realloc(ram_list.phys_dirty,
                                        last_ram_offset() >> TARGET_PAGE_BITS);
     memset(ram_list.phys_dirty + (new_block->offset >> TARGET_PAGE_BITS),
@@ -1084,6 +1086,7 @@
         if (addr == block->offset) {
             QTAILQ_REMOVE(&ram_list.blocks, block, next);
             ram_list.mru_block = NULL;
+            ram_list.version++;
             g_free(block);
             return;
         }
@@ -1098,6 +1101,7 @@
         if (addr == block->offset) {
             QTAILQ_REMOVE(&ram_list.blocks, block, next);
             ram_list.mru_block = NULL;
+            ram_list.version++;
             if (block->flags & RAM_PREALLOC_MASK) {
                 ;
             } else if (mem_path) {