Source and target are in sync when we leave the mirror_run loop, they should remain so until bdrv_swap. Before block_job_defer_to_main_loop was introduced, it has been easy to prove that. Now that tricky things can happen after mirror_run returns and before mirror_exit runs, for example, ioeventfd handlers being called, or a device model timer callback submitting more I/O.
So, skip the block_job_defer_to_main_loop if we're already in the main context. This is a necessary special casing until BlockBackend really honors bdrv_lock. If we're not in the main context, we rely on the notifying mechanism to do the right thing. Signed-off-by: Fam Zheng <f...@redhat.com> --- block/mirror.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 58f391a..24cf687 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -57,6 +57,8 @@ typedef struct MirrorBlockJob { int in_flight; int sectors_in_flight; int ret; + /* True if the source is locked by us */ + bool need_unlock; } MirrorBlockJob; typedef struct MirrorOp { @@ -358,6 +360,9 @@ static void mirror_exit(BlockJob *job, void *opaque) if (replace_aio_context) { aio_context_release(replace_aio_context); } + if (s->need_unlock) { + bdrv_unlock(s->common.bs); + } g_free(s->replaces); bdrv_unref(s->target); block_job_completed(&s->common, data->ret); @@ -521,7 +526,8 @@ static void coroutine_fn mirror_run(void *opaque) * mirror_populate runs. */ trace_mirror_before_drain(s, cnt); - bdrv_drain(bs); + bdrv_lock(bs); + s->need_unlock = true; cnt = bdrv_get_dirty_count(s->dirty_bitmap); } @@ -543,6 +549,10 @@ static void coroutine_fn mirror_run(void *opaque) s->common.cancelled = false; break; } + if (s->need_unlock) { + bdrv_unlock(bs); + s->need_unlock = false; + } last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); } @@ -565,7 +575,11 @@ immediate_exit: data = g_malloc(sizeof(*data)); data->ret = ret; - block_job_defer_to_main_loop(&s->common, mirror_exit, data); + if (bs->aio_context == qemu_get_aio_context()) { + mirror_exit(&s->common, data); + } else { + block_job_defer_to_main_loop(&s->common, mirror_exit, data); + } } static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp) -- 2.4.1