qemu_file: Use a stat64 for qemu_file_transferred

This way we can read it from any thread.
I checked that it gives the same value as the current one.  We never
use two qemu_files at the same time.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231025091117.6342-3-quintela@redhat.com>

migration/migration-stats.h

@@ -81,6 +81,10 @@ typedef struct {
      * Number of bytes sent during precopy stage.
      */
     Stat64 precopy_bytes;
+    /*
+     * Number of bytes transferred with QEMUFile.
+     */
+    Stat64 qemu_file_transferred;
     /*
      * Amount of transferred data at the start of current cycle.
      */

migration/qemu-file.c

@@ -283,6 +283,7 @@ void qemu_fflush(QEMUFile *f)
         } else {
             uint64_t size = iov_size(f->iov, f->iovcnt);
             f->total_transferred += size;
+            stat64_add(&mig_stats.qemu_file_transferred, size);
         }
 
         qemu_iovec_release_ram(f);
@@ -623,7 +624,7 @@ int coroutine_mixed_fn qemu_get_byte(QEMUFile *f)
 
 uint64_t qemu_file_transferred_noflush(QEMUFile *f)
 {
-    uint64_t ret = f->total_transferred;
+    uint64_t ret = stat64_get(&mig_stats.qemu_file_transferred);
     int i;
 
     g_assert(qemu_file_is_writable(f));
@@ -639,7 +640,7 @@ uint64_t qemu_file_transferred(QEMUFile *f)
 {
     g_assert(qemu_file_is_writable(f));
     qemu_fflush(f);
-    return f->total_transferred;
+    return stat64_get(&mig_stats.qemu_file_transferred);
 }
 
 void qemu_put_be16(QEMUFile *f, unsigned int v)