[Qemu-devel] [PATCH 22/43] migration/block: fix pending() return value

[Michael Roth]

From: Vladimir Sementsov-Ogievskiy <address@hidden>

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 <address@hidden>
Message-id: address@hidden
Signed-off-by: Stefan Hajnoczi <address@hidden>
(cherry picked from commit 04636dc410b163c2243e66c3813dd4900a50a4ed)
Signed-off-by: Michael Roth <address@hidden>
---
 block-migration.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 74d9eb1..2e92605 100644
--- 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();
-- 
1.9.1