migration/ram: Merge save_zero_page functions

We don't need to do this in two pieces. One single function makes it
easier to grasp, specially since it removes the indirection on the
return value handling.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184604.32364-7-farosas@suse.de>

migration/ram.c

@@ -1137,32 +1137,6 @@ void ram_release_page(const char *rbname, uint64_t offset)
     ram_discard_range(rbname, offset, TARGET_PAGE_SIZE);
 }
 
-/**
- * save_zero_page_to_file: send the zero page to the file
- *
- * Returns the size of data written to the file, 0 means the page is not
- * a zero page
- *
- * @pss: current PSS channel
- * @block: block that contains the page we want to send
- * @offset: offset inside the block for the page
- */
-static int save_zero_page_to_file(PageSearchStatus *pss, RAMBlock *block,
-                                  ram_addr_t offset)
-{
-    uint8_t *p = block->host + offset;
-    QEMUFile *file = pss->pss_channel;
-    int len = 0;
-
-    if (buffer_is_zero(p, TARGET_PAGE_SIZE)) {
-        len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_ZERO);
-        qemu_put_byte(file, 0);
-        len += 1;
-        ram_release_page(block->idstr, offset);
-    }
-    return len;
-}
-
 /**
  * save_zero_page: send the zero page to the stream
  *
@@ -1176,12 +1150,19 @@ static int save_zero_page_to_file(PageSearchStatus *pss, RAMBlock *block,
 static int save_zero_page(RAMState *rs, PageSearchStatus *pss, RAMBlock *block,
                           ram_addr_t offset)
 {
-    int len = save_zero_page_to_file(pss, block, offset);
+    uint8_t *p = block->host + offset;
+    QEMUFile *file = pss->pss_channel;
+    int len = 0;
 
-    if (!len) {
-        return -1;
+    if (!buffer_is_zero(p, TARGET_PAGE_SIZE)) {
+        return 0;
     }
 
+    len += save_page_header(pss, file, block, offset | RAM_SAVE_FLAG_ZERO);
+    qemu_put_byte(file, 0);
+    len += 1;
+    ram_release_page(block->idstr, offset);
+
     stat64_add(&mig_stats.zero_pages, 1);
     ram_transferred_add(len);
 
@@ -1195,7 +1176,7 @@ static int save_zero_page(RAMState *rs, PageSearchStatus *pss, RAMBlock *block,
         XBZRLE_cache_unlock();
     }
 
-    return 1;
+    return len;
 }
 
 /*
@@ -2152,9 +2133,8 @@ static int ram_save_target_page_legacy(RAMState *rs, PageSearchStatus *pss)
         return 1;
     }
 
-    res = save_zero_page(rs, pss, block, offset);
-    if (res > 0) {
-        return res;
+    if (save_zero_page(rs, pss, block, offset)) {
+        return 1;
     }
 
     /*