io-wq: wait for worker startup when forking a new one

We need to have our worker count updated before continuing, to avoid
cases where we repeatedly think we need a new worker, but a fork is
already in progress.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 44e20248805ac9c7365ba6099f65d1ff597e0d81..965022fe9961c9c9a660d2694e563dcc297a5c6b 100644 (file)
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -56,6 +56,7 @@ struct io_worker {
        const struct cred *saved_creds;
 
        struct completion ref_done;
+       struct completion started;
 
        struct rcu_head rcu;
 };
@@ -267,6 +268,7 @@ static void io_worker_start(struct io_worker *worker)
 {
        worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
        io_wqe_inc_running(worker);
+       complete(&worker->started);
 }
 
 /*
@@ -644,6 +646,7 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
        worker->wqe = wqe;
        spin_lock_init(&worker->lock);
        init_completion(&worker->ref_done);
+       init_completion(&worker->started);
 
        refcount_inc(&wq->refs);
 
@@ -656,6 +659,7 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
                kfree(worker);
                return false;
        }
+       wait_for_completion(&worker->started);
        return true;
 }