migration/block: fix pending() return value

Because of wrong return value of .save_live_pending() in
migration/block.c, migration finishes before the whole disk is
transferred. Such situation occurs when the migration process is fast
enough, 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>
Message-id: 1419933856-4018-2-git-send-email-vsementsov@parallels.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 04636dc410b163c2243e66c3813dd4900a50a4ed)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block-migration.c b/block-migration.c
index 74d9eb125c7585bf10eae7060e98567d942323b6..2e92605adc75fd163ccba5bcdd26ad42793558dd 100644 (file)
--- a/block-migration.c
+++ b/block-migration.c
@@ -765,8 +765,8 @@ 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();