io-wq: remove nr_process accounting

We're now just using fork like we would from userspace, so there's no
need to try and impose extra restrictions or accounting on the user
side of things. That's already being done for us. That also means we
don't have to pass in the user_struct anymore, that's correctly inherited
through ->creds on fork.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io-wq.c

@@ -172,8 +172,6 @@ static void io_worker_exit(struct io_worker *worker)
 	worker->flags = 0;
 	if (flags & IO_WORKER_F_RUNNING)
 		atomic_dec(&acct->nr_running);
-	if (!(flags & IO_WORKER_F_BOUND))
-		atomic_dec(&wqe->wq->user->processes);
 	worker->flags = 0;
 	preempt_enable();
 
@@ -299,12 +297,10 @@ static void __io_worker_busy(struct io_wqe *wqe, struct io_worker *worker,
 			worker->flags |= IO_WORKER_F_BOUND;
 			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers--;
 			wqe->acct[IO_WQ_ACCT_BOUND].nr_workers++;
-			atomic_dec(&wqe->wq->user->processes);
 		} else {
 			worker->flags &= ~IO_WORKER_F_BOUND;
 			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers++;
 			wqe->acct[IO_WQ_ACCT_BOUND].nr_workers--;
-			atomic_inc(&wqe->wq->user->processes);
 		}
 		io_wqe_inc_running(worker);
 	 }
@@ -575,9 +571,6 @@ static int task_thread(void *data, int index)
 	acct->nr_workers++;
 	raw_spin_unlock_irq(&wqe->lock);
 
-	if (index == IO_WQ_ACCT_UNBOUND)
-		atomic_inc(&wq->user->processes);
-
 	io_wqe_worker(data);
 	do_exit(0);
 }
@@ -730,29 +723,6 @@ static int io_wq_manager(void *data)
 	do_exit(0);
 }
 
-static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
-			    struct io_wq_work *work)
-{
-	bool free_worker;
-
-	if (!(work->flags & IO_WQ_WORK_UNBOUND))
-		return true;
-	if (atomic_read(&acct->nr_running))
-		return true;
-
-	rcu_read_lock();
-	free_worker = !hlist_nulls_empty(&wqe->free_list);
-	rcu_read_unlock();
-	if (free_worker)
-		return true;
-
-	if (atomic_read(&wqe->wq->user->processes) >= acct->max_workers &&
-	    !(capable(CAP_SYS_RESOURCE) || capable(CAP_SYS_ADMIN)))
-		return false;
-
-	return true;
-}
-
 static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe)
 {
 	struct io_wq *wq = wqe->wq;
@@ -790,17 +760,6 @@ static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
 	int work_flags;
 	unsigned long flags;
 
-	/*
-	 * Do early check to see if we need a new unbound worker, and if we do,
-	 * if we're allowed to do so. This isn't 100% accurate as there's a
-	 * gap between this check and incrementing the value, but that's OK.
-	 * It's close enough to not be an issue, fork() has the same delay.
-	 */
-	if (unlikely(!io_wq_can_queue(wqe, acct, work))) {
-		io_run_cancel(work, wqe);
-		return;
-	}
-
 	work_flags = work->flags;
 	raw_spin_lock_irqsave(&wqe->lock, flags);
 	io_wqe_insert_work(wqe, work);
@@ -978,9 +937,6 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 	wq->free_work = data->free_work;
 	wq->do_work = data->do_work;
 
-	/* caller must already hold a reference to this */
-	wq->user = data->user;
-
 	ret = -ENOMEM;
 	for_each_node(node) {
 		struct io_wqe *wqe;
@@ -995,10 +951,8 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 		wqe->node = alloc_node;
 		wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
 		atomic_set(&wqe->acct[IO_WQ_ACCT_BOUND].nr_running, 0);
-		if (wq->user) {
-			wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
+		wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
 					task_rlimit(current, RLIMIT_NPROC);
-		}
 		atomic_set(&wqe->acct[IO_WQ_ACCT_UNBOUND].nr_running, 0);
 		wqe->wq = wq;
 		raw_spin_lock_init(&wqe->lock);

fs/io-wq.h

@@ -94,8 +94,6 @@ typedef struct io_wq_work *(free_work_fn)(struct io_wq_work *);
 typedef void (io_wq_work_fn)(struct io_wq_work *);
 
 struct io_wq_data {
-	struct user_struct *user;
-
 	io_wq_work_fn *do_work;
 	free_work_fn *free_work;
 };

fs/io_uring.c

@@ -7767,7 +7767,6 @@ static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx)
 	struct io_wq_data data;
 	unsigned int concurrency;
 
-	data.user = ctx->user;
 	data.free_work = io_free_work;
 	data.do_work = io_wq_submit_work;