[PATCH 4/4] multifd: reset next_packet_len after sending pages

[Elena Ufimtseva <elena.ufimtseva@oracle.com>]

Sometimes multifd sends just sync packet with no pages
(normal_num is 0). In this case the old value is being
preserved and being accounted for while only packet_len
is being transferred.
Reset it to 0 after sending and accounting for.

TODO: Fix the same packet ids in the stream.
with this patch, there is still an issue with the duplicated
packets ids being sent (with different number of pages/flags).
See in below multifd_send trace (before this change):
multifd_send 394.774 pid=55477 id=0x1 packet_num=0x6f0 normal=0x57 flags=0x1 next_packet_size=0x57000
multifd_send 181.244 pid=55477 id=0x1 packet_num=0x6f0 normal=0x0 flags=0x0 next_packet_size=0x57000

With this commit there are still duplicated packets, but since no pages
are being sent with sync flag set, next_packet_size is 0:
multifd_send 27.814 pid=18602 id=0x1 packet_num=0x574 normal=0x7b flags=0x1 next_packet_size=0x7b000
multifd_send 136054.792 pid=18602 id=0x1 packet_num=0x574 normal=0x0 flags=0x0 next_packet_size=0x0
If there is a suggestion how to fix this properly, I will be
glad to use it.

Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
---
 migration/multifd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/migration/multifd.c b/migration/multifd.c
index 3281397b18..8b4e26051b 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -730,6 +730,7 @@ static void *multifd_send_thread(void *opaque)
                        p->next_packet_size + p->packet_len);
             stat64_add(&mig_stats.transferred,
                        p->next_packet_size + p->packet_len);
+            p->next_packet_size = 0;
             qemu_mutex_lock(&p->mutex);
             p->pending_job--;
             qemu_mutex_unlock(&p->mutex);
-- 
2.34.1