[PATCH 1/2] migration/multifd: clean pages after filling packet

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

This is a preparation for the next patch:

    not use multifd during postcopy.

Without enabling postcopy, everything looks good. While after enabling
postcopy, migration may fail even not use multifd during postcopy. The
reason is the pages is not properly cleared and *old* target page will
continue to be transferred.

After clean pages, migration succeeds.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 migration/ram.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 80dd2d55f9..7087bb73ed 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -929,10 +929,10 @@ static int multifd_send_pages(RAMState *rs)
         }
         qemu_mutex_unlock(&p->mutex);
     }
-    p->pages->used = 0;
+    assert(!p->pages->used);
+    assert(!p->pages->block);
 
     p->packet_num = multifd_send_state->packet_num++;
-    p->pages->block = NULL;
     multifd_send_state->pages = p->pages;
     p->pages = pages;
     transferred = ((uint64_t) pages->used) * TARGET_PAGE_SIZE + p->packet_len;
@@ -1114,6 +1114,8 @@ static void *multifd_send_thread(void *opaque)
             p->flags = 0;
             p->num_packets++;
             p->num_pages += used;
+            p->pages->used = 0;
+            p->pages->block = NULL;
             qemu_mutex_unlock(&p->mutex);
 
             trace_multifd_send(p->id, packet_num, used, flags,
-- 
2.17.1