[PATCH v2 4/8] migration: introduce save_zero_page_to_file

[guangrong.xiao@gmail.com]

From: Xiao Guangrong <xiaoguangrong@tencent.com>

It will be used by the compression threads

Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com>
---
 migration/ram.c | 40 ++++++++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 10 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index e68b0e6dec..ce6e69b649 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1696,27 +1696,47 @@ static void migration_bitmap_sync(RAMState *rs)
 /**
  * save_zero_page: send the zero page to the stream
  *
- * Returns the number of pages written.
+ * Returns the size of data written to the file, 0 means the page is not
+ * a zero page
  *
  * @rs: current RAM state
+ * @file: the file where the data is saved
  * @block: block that contains the page we want to send
  * @offset: offset inside the block for the page
  */
-static int save_zero_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
+static int save_zero_page_to_file(RAMState *rs, QEMUFile *file,
+                                  RAMBlock *block, ram_addr_t offset)
 {
     uint8_t *p = block->host + offset;
-    int pages = -1;
+    int len = 0;
 
     if (is_zero_range(p, TARGET_PAGE_SIZE)) {
-        ram_counters.duplicate++;
-        ram_counters.transferred +=
-            save_page_header(rs, rs->f, block, offset | RAM_SAVE_FLAG_ZERO);
-        qemu_put_byte(rs->f, 0);
-        ram_counters.transferred += 1;
-        pages = 1;
+        len += save_page_header(rs, file, block, offset | RAM_SAVE_FLAG_ZERO);
+        qemu_put_byte(file, 0);
+        len += 1;
     }
+    return len;
+}
 
-    return pages;
+/**
+ * save_zero_page: send the zero page to the stream
+ *
+ * Returns the number of pages written.
+ *
+ * @rs: current RAM state
+ * @block: block that contains the page we want to send
+ * @offset: offset inside the block for the page
+ */
+static int save_zero_page(RAMState *rs, RAMBlock *block, ram_addr_t offset)
+{
+    int len = save_zero_page_to_file(rs, rs->f, block, offset);
+
+    if (len) {
+        ram_counters.duplicate++;
+        ram_counters.transferred += len;
+        return 1;
+    }
+    return -1;
 }
 
 static void ram_release_pages(const char *rbname, uint64_t offset, int pages)
-- 
2.14.4