[Qemu-devel] [PATCH] block-migration: fix pending() return value

[Vladimir Sementsov-Ogievskiy <vsementsov@parallels.com>]

Because of wrong return value of .save_live_pending() in
block-migration, migration finishes before the whole disk
is transferred. Such situation occures when the migration
process is fast enouth, for example when source and dest
are on the same host.

If in the bulk phase we return something < max_size, we will skip
transferring the tail of the device. Currently we have "set pending to
BLOCK_SIZE if it is zero" for bulk phase, but there no guarantee, that
it will be < max_size.

True approach is to return, for example, max_size+1 when we are in the
bulk phase.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@parallels.com>
---
 block-migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 73cdd07..bf78bd8 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -756,8 +756,8 @@ static uint64_t block_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
                        block_mig_state.read_done * BLOCK_SIZE;
 
     /* Report at least one block pending during bulk phase */
-    if (pending == 0 && !block_mig_state.bulk_completed) {
-        pending = BLOCK_SIZE;
+    if (pending <= max_size && !block_mig_state.bulk_completed) {
+        pending = max_size + BLOCK_SIZE;
     }
     blk_mig_unlock();
     qemu_mutex_unlock_iothread();
-- 
1.9.1