Request callbacks can do pretty much anything, including operations that will yield from the coroutine (such as draining the backend). In that case, a decreased in_flight would be visible to other code and could lead to a drain completing while the callback hasn't actually completed yet.
Signed-off-by: Kevin Wolf <kw...@redhat.com> Reviewed-by: Fam Zheng <f...@redhat.com> Reviewed-by: Max Reitz <mre...@redhat.com> --- block/block-backend.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/block-backend.c b/block/block-backend.c index 63eb2d10cd..5e5e60ff8d 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1340,8 +1340,8 @@ static const AIOCBInfo blk_aio_em_aiocb_info = { static void blk_aio_complete(BlkAioEmAIOCB *acb) { if (acb->has_returned) { - blk_dec_in_flight(acb->rwco.blk); acb->common.cb(acb->common.opaque, acb->rwco.ret); + blk_dec_in_flight(acb->rwco.blk); qemu_aio_unref(acb); } } -- 2.13.6