migration: rename rate limiting fields in QEMUFile

This renames the following QEMUFile fields

 * bytes_xfer -> rate_limit_used
 * xfer_limit -> rate_limit_max

The intent is to make it clear that 'bytes_xfer' is specifically related
to rate limiting of data and applies to data queued, which need not have
been transferred on the wire yet if a flush hasn't taken place.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/qemu-file.c

@@ -39,8 +39,16 @@ struct QEMUFile {
     const QEMUFileHooks *hooks;
     void *opaque;
 
-    int64_t bytes_xfer;
-    int64_t xfer_limit;
+    /*
+     * Maximum amount of data in bytes to transfer during one
+     * rate limiting time window
+     */
+    int64_t rate_limit_max;
+    /*
+     * Total amount of data in bytes queued for transfer
+     * during this rate limiting time window
+     */
+    int64_t rate_limit_used;
 
     int64_t pos; /* start of buffer when writing, end of buffer
                     when reading */
@@ -304,7 +312,7 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
         int ret = f->hooks->save_page(f, f->opaque, block_offset,
                                       offset, size, bytes_sent);
         if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
-            f->bytes_xfer += size;
+            f->rate_limit_used += size;
         }
 
         if (ret != RAM_SAVE_CONTROL_DELAYED &&
@@ -457,7 +465,7 @@ void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, size_t size,
         return;
     }
 
-    f->bytes_xfer += size;
+    f->rate_limit_used += size;
     add_to_iovec(f, buf, size, may_free);
 }
 
@@ -475,7 +483,7 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, size_t size)
             l = size;
         }
         memcpy(f->buf + f->buf_index, buf, l);
-        f->bytes_xfer += l;
+        f->rate_limit_used += l;
         add_buf_to_iovec(f, l);
         if (qemu_file_get_error(f)) {
             break;
@@ -492,7 +500,7 @@ void qemu_put_byte(QEMUFile *f, int v)
     }
 
     f->buf[f->buf_index] = v;
-    f->bytes_xfer++;
+    f->rate_limit_used++;
     add_buf_to_iovec(f, 1);
 }
 
@@ -674,30 +682,30 @@ int qemu_file_rate_limit(QEMUFile *f)
     if (qemu_file_get_error(f)) {
         return 1;
     }
-    if (f->xfer_limit > 0 && f->bytes_xfer > f->xfer_limit) {
+    if (f->rate_limit_max > 0 && f->rate_limit_used > f->rate_limit_max) {
         return 1;
     }
     return 0;
 }
 
 int64_t qemu_file_get_rate_limit(QEMUFile *f)
 {
-    return f->xfer_limit;
+    return f->rate_limit_max;
 }
 
 void qemu_file_set_rate_limit(QEMUFile *f, int64_t limit)
 {
-    f->xfer_limit = limit;
+    f->rate_limit_max = limit;
 }
 
 void qemu_file_reset_rate_limit(QEMUFile *f)
 {
-    f->bytes_xfer = 0;
+    f->rate_limit_used = 0;
 }
 
 void qemu_file_update_transfer(QEMUFile *f, int64_t len)
 {
-    f->bytes_xfer += len;
+    f->rate_limit_used += len;
 }
 
 void qemu_put_be16(QEMUFile *f, unsigned int v)