migration: make qemu_ftell() public and support writable files

Migration .save_live_iterate() functions return the number of bytes
transferred.  The easiest way of doing this is by calling qemu_ftell(f)
at the beginning and end of the function to calculate the difference.

Make qemu_ftell() public so that block-migration will be able to use it.
Also adjust the ftell calculation for writable files where buf_offset
does not include buf_size.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-id: 1360661835-28663-2-git-send-email-stefanha@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/savevm.c b/savevm.c
index 0b6724dddb..a8a53efc9b 100644
--- a/savevm.c
+++ b/savevm.c
@@ -673,9 +673,14 @@ int qemu_get_byte(QEMUFile *f)
     return result;
 }
 
-static int64_t qemu_ftell(QEMUFile *f)
+int64_t qemu_ftell(QEMUFile *f)
 {
-    return f->buf_offset - f->buf_size + f->buf_index;
+    /* buf_offset excludes buffer for writing but includes it for reading */
+    if (f->is_write) {
+        return f->buf_offset + f->buf_index;
+    } else {
+        return f->buf_offset - f->buf_size + f->buf_index;
+    }
 }
 
 int qemu_file_rate_limit(QEMUFile *f)