io_uring: split out task work code into tw.c

Move the task work handling code out of io_uring.c into a new tw.c file.
This includes the local work, normal work, and fallback work handling
infrastructure.

The associated tw.h header contains io_should_terminate_tw() as a static
inline helper, along with the necessary function declarations.

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

1 files changed, 124 insertions, 0 deletions

diff --git a/io_uring/tw.h b/io_uring/tw.h
new file mode 100644
index 000000000000..8683efca58ef
--- /dev/null
+++ b/io_uring/tw.h
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef IOU_TW_H
+#define IOU_TW_H
+
+#include <linux/sched.h>
+#include <linux/percpu-refcount.h>
+#include <linux/io_uring_types.h>
+
+#define IO_LOCAL_TW_DEFAULT_MAX		20
+
+/*
+ * No waiters. It's larger than any valid value of the tw counter
+ * so that tests against ->cq_wait_nr would fail and skip wake_up().
+ */
+#define IO_CQ_WAKE_INIT		(-1U)
+/* Forced wake up if there is a waiter regardless of ->cq_wait_nr */
+#define IO_CQ_WAKE_FORCE	(IO_CQ_WAKE_INIT >> 1)
+
+/*
+ * Terminate the request if either of these conditions are true:
+ *
+ * 1) It's being executed by the original task, but that task is marked
+ *    with PF_EXITING as it's exiting.
+ * 2) PF_KTHREAD is set, in which case the invoker of the task_work is
+ *    our fallback task_work.
+ * 3) The ring has been closed and is going away.
+ */
+static inline bool io_should_terminate_tw(struct io_ring_ctx *ctx)
+{
+	return (current->flags & (PF_EXITING | PF_KTHREAD)) || percpu_ref_is_dying(&ctx->refs);
+}
+
+void io_req_task_work_add_remote(struct io_kiocb *req, unsigned flags);
+struct llist_node *io_handle_tw_list(struct llist_node *node, unsigned int *count, unsigned int max_entries);
+void tctx_task_work(struct callback_head *cb);
+int io_run_local_work(struct io_ring_ctx *ctx, int min_events, int max_events);
+int io_run_task_work_sig(struct io_ring_ctx *ctx);
+
+__cold void io_fallback_req_func(struct work_struct *work);
+__cold void io_move_task_work_from_local(struct io_ring_ctx *ctx);
+int io_run_local_work_locked(struct io_ring_ctx *ctx, int min_events);
+
+void io_req_local_work_add(struct io_kiocb *req, unsigned flags);
+void io_req_normal_work_add(struct io_kiocb *req);
+struct llist_node *tctx_task_work_run(struct io_uring_task *tctx, unsigned int max_entries, unsigned int *count);
+
+static inline void __io_req_task_work_add(struct io_kiocb *req, unsigned flags)
+{
+	if (req->ctx->flags & IORING_SETUP_DEFER_TASKRUN)
+		io_req_local_work_add(req, flags);
+	else
+		io_req_normal_work_add(req);
+}
+
+static inline void io_req_task_work_add(struct io_kiocb *req)
+{
+	__io_req_task_work_add(req, 0);
+}
+
+static inline int io_run_task_work(void)
+{
+	bool ret = false;
+
+	/*
+	 * Always check-and-clear the task_work notification signal. With how
+	 * signaling works for task_work, we can find it set with nothing to
+	 * run. We need to clear it for that case, like get_signal() does.
+	 */
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+		clear_notify_signal();
+	/*
+	 * PF_IO_WORKER never returns to userspace, so check here if we have
+	 * notify work that needs processing.
+	 */
+	if (current->flags & PF_IO_WORKER) {
+		if (test_thread_flag(TIF_NOTIFY_RESUME)) {
+			__set_current_state(TASK_RUNNING);
+			resume_user_mode_work(NULL);
+		}
+		if (current->io_uring) {
+			unsigned int count = 0;
+
+			__set_current_state(TASK_RUNNING);
+			tctx_task_work_run(current->io_uring, UINT_MAX, &count);
+			if (count)
+				ret = true;
+		}
+	}
+	if (task_work_pending(current)) {
+		__set_current_state(TASK_RUNNING);
+		task_work_run();
+		ret = true;
+	}
+
+	return ret;
+}
+
+static inline bool io_local_work_pending(struct io_ring_ctx *ctx)
+{
+	return !llist_empty(&ctx->work_llist) || !llist_empty(&ctx->retry_llist);
+}
+
+static inline bool io_task_work_pending(struct io_ring_ctx *ctx)
+{
+	return task_work_pending(current) || io_local_work_pending(ctx);
+}
+
+static inline void io_tw_lock(struct io_ring_ctx *ctx, io_tw_token_t tw)
+{
+	lockdep_assert_held(&ctx->uring_lock);
+}
+
+static inline bool io_allowed_defer_tw_run(struct io_ring_ctx *ctx)
+{
+	return likely(ctx->submitter_task == current);
+}
+
+static inline bool io_allowed_run_tw(struct io_ring_ctx *ctx)
+{
+	return likely(!(ctx->flags & IORING_SETUP_DEFER_TASKRUN) ||
+		      ctx->submitter_task == current);
+}
+
+#endif