[Qemu-devel] [PATCH 1/2] migration/xbzrle: update cache and current_data in one place

[Wei Yang <richardw.yang@linux.intel.com>]

When we are not in the last_stage, we need to update the cache if page
is not the same.

Currently this procedure is scattered in two places and mixed with
encoding status check.

This patch extract this general step out to make the code a little bit
easy to read.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 migration/ram.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index e9b40d636d..878cd8de7a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1594,25 +1594,24 @@ static int save_xbzrle_page(RAMState *rs, uint8_t **current_data,
     encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
                                        TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
                                        TARGET_PAGE_SIZE);
+
+    /*
+     * we need to update the data in the cache, in order to get the same data
+     */
+    if (!last_stage && encoded_len != 0) {
+        memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
+        *current_data = prev_cached_page;
+    }
+
     if (encoded_len == 0) {
         trace_save_xbzrle_page_skipping();
         return 0;
     } else if (encoded_len == -1) {
         trace_save_xbzrle_page_overflow();
         xbzrle_counters.overflow++;
-        /* update data in the cache */
-        if (!last_stage) {
-            memcpy(prev_cached_page, *current_data, TARGET_PAGE_SIZE);
-            *current_data = prev_cached_page;
-        }
         return -1;
     }
 
-    /* we need to update the data in the cache, in order to get the same data */
-    if (!last_stage) {
-        memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
-    }
-
     /* Send XBZRLE based compressed page */
     bytes_xbzrle = save_page_header(rs, rs->f, block,
                                     offset | RAM_SAVE_FLAG_XBZRLE);
-- 
2.19.1