When mirror should complete, the source and target are in sync. But we call bdrv_swap() only a while later in the main loop bh. If the guest writes something before that, target will not get the new data.
Block "device IO" before bdrv_drain and unblock it after bdrw_swap(). Reported-by: Wen Congyang <we...@cn.fujitsu.com> Signed-off-by: Fam Zheng <f...@redhat.com> --- block/mirror.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/block/mirror.c b/block/mirror.c index 58f391a..f400456 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -320,6 +320,8 @@ static void mirror_drain(MirrorBlockJob *s) typedef struct { int ret; + /* Use to pause device IO during mirror exit */ + Error *blocker; } MirrorExitData; static void mirror_exit(BlockJob *job, void *opaque) @@ -328,6 +330,8 @@ static void mirror_exit(BlockJob *job, void *opaque) MirrorExitData *data = opaque; AioContext *replace_aio_context = NULL; + bdrv_op_unblock(s->common.bs, BLOCK_OP_TYPE_DEVICE_IO, data->blocker); + error_free(data->blocker); if (s->to_replace) { replace_aio_context = bdrv_get_aio_context(s->to_replace); aio_context_acquire(replace_aio_context); @@ -376,6 +380,8 @@ static void coroutine_fn mirror_run(void *opaque) checking for a NULL string */ int ret = 0; int n; + data = g_malloc0(sizeof(*data)); + error_setg(&data->blocker, "mirror job exiting"); if (block_job_is_cancelled(&s->common)) { goto immediate_exit; @@ -521,6 +527,7 @@ static void coroutine_fn mirror_run(void *opaque) * mirror_populate runs. */ trace_mirror_before_drain(s, cnt); + bdrv_op_block(bs, BLOCK_OP_TYPE_DEVICE_IO, data->blocker); bdrv_drain(bs); cnt = bdrv_get_dirty_count(s->dirty_bitmap); } @@ -543,6 +550,7 @@ static void coroutine_fn mirror_run(void *opaque) s->common.cancelled = false; break; } + bdrv_op_unblock(bs, BLOCK_OP_TYPE_DEVICE_IO, data->blocker); last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); } @@ -563,7 +571,6 @@ immediate_exit: bdrv_release_dirty_bitmap(bs, s->dirty_bitmap); bdrv_iostatus_disable(s->target); - data = g_malloc(sizeof(*data)); data->ret = ret; block_job_defer_to_main_loop(&s->common, mirror_exit, data); } -- 2.4.1