[Qemu-devel] [PATCH] [qemu-devel] fix wrong order when doing live block migration setup

[chai wen]

If we want to track dirty blocks using dirty_maps on a BlockDriverState
when doing live block-migration, its correspoding 'BlkMigDevState' should be
add to block_mig_state.bmds_list firstly for subsequent processing.
Otherwise set_dirty_tracking will do nothing on an empty list than allocating
dirty_bitmaps for them.

And what's the worse, bdrv_get_dirty_count will access the
bmds->dirty_maps directly, there could be a segfault as the reasons
above.

Signed-off-by: chai wen <address@hidden>
---
 block-migration.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block-migration.c b/block-migration.c
index 56951e0..43203aa 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -626,6 +626,7 @@ static int block_save_setup(QEMUFile *f, void *opaque)
             block_mig_state.submitted, block_mig_state.transferred);
 
     qemu_mutex_lock_iothread();
+    init_blk_migration(f);
 
     /* start track dirty blocks */
     ret = set_dirty_tracking();
@@ -635,7 +636,6 @@ static int block_save_setup(QEMUFile *f, void *opaque)
         return ret;
     }
 
-    init_blk_migration(f);
 
     qemu_mutex_unlock_iothread();
 
-- 
1.7.1