io_uring: introduce type alias for io_tw_state

In preparation for changing how io_tw_state is passed, introduce a type
alias io_tw_token_t for struct io_tw_state *. This allows for changing
the representation in one place, without having to update the many
functions that just forward their struct io_tw_state * argument.

Also add a comment to struct io_tw_state to explain its purpose.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Link: https://lore.kernel.org/r/20250217022511.1150145-1-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/io_uring_types.h

@@ -436,8 +436,15 @@ struct io_ring_ctx {
 	struct io_mapped_region		param_region;
 };
 
+/*
+ * Token indicating function is called in task work context:
+ * ctx->uring_lock is held and any completions generated will be flushed.
+ * ONLY core io_uring.c should instantiate this struct.
+ */
 struct io_tw_state {
 };
+/* Alias to use in code that doesn't instantiate struct io_tw_state */
+typedef struct io_tw_state *io_tw_token_t;
 
 enum {
 	REQ_F_FIXED_FILE_BIT	= IOSQE_FIXED_FILE_BIT,
@@ -563,7 +570,7 @@ enum {
 	REQ_F_HAS_METADATA	= IO_REQ_FLAG(REQ_F_HAS_METADATA_BIT),
 };
 
-typedef void (*io_req_tw_func_t)(struct io_kiocb *req, struct io_tw_state *ts);
+typedef void (*io_req_tw_func_t)(struct io_kiocb *req, io_tw_token_t tw);
 
 struct io_task_work {
 	struct llist_node		node;

io_uring/futex.c

@@ -44,30 +44,30 @@ void io_futex_cache_free(struct io_ring_ctx *ctx)
 	io_alloc_cache_free(&ctx->futex_cache, kfree);
 }
 
-static void __io_futex_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void __io_futex_complete(struct io_kiocb *req, io_tw_token_t tw)
 {
 	req->async_data = NULL;
 	hlist_del_init(&req->hash_node);
-	io_req_task_complete(req, ts);
+	io_req_task_complete(req, tw);
 }
 
-static void io_futex_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_futex_complete(struct io_kiocb *req, io_tw_token_t tw)
 {
 	struct io_futex_data *ifd = req->async_data;
 	struct io_ring_ctx *ctx = req->ctx;
 
-	io_tw_lock(ctx, ts);
+	io_tw_lock(ctx, tw);
 	if (!io_alloc_cache_put(&ctx->futex_cache, ifd))
 		kfree(ifd);
-	__io_futex_complete(req, ts);
+	__io_futex_complete(req, tw);
 }
 
-static void io_futexv_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_futexv_complete(struct io_kiocb *req, io_tw_token_t tw)
 {
 	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
 	struct futex_vector *futexv = req->async_data;
 
-	io_tw_lock(req->ctx, ts);
+	io_tw_lock(req->ctx, tw);
 
 	if (!iof->futexv_unqueued) {
 		int res;
@@ -79,7 +79,7 @@ static void io_futexv_complete(struct io_kiocb *req, struct io_tw_state *ts)
 
 	kfree(req->async_data);
 	req->flags &= ~REQ_F_ASYNC_DATA;
-	__io_futex_complete(req, ts);
+	__io_futex_complete(req, tw);
 }
 
 static bool io_futexv_claim(struct io_futex *iof)

io_uring/io_uring.c

@@ -543,7 +543,7 @@ static void io_queue_iowq(struct io_kiocb *req)
 		io_queue_linked_timeout(link);
 }
 
-static void io_req_queue_iowq_tw(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_req_queue_iowq_tw(struct io_kiocb *req, io_tw_token_t tw)
 {
 	io_queue_iowq(req);
 }
@@ -1022,7 +1022,7 @@ static inline struct io_kiocb *io_req_find_next(struct io_kiocb *req)
 	return nxt;
 }
 
-static void ctx_flush_and_put(struct io_ring_ctx *ctx, struct io_tw_state *ts)
+static void ctx_flush_and_put(struct io_ring_ctx *ctx, io_tw_token_t tw)
 {
 	if (!ctx)
 		return;
@@ -1277,7 +1277,7 @@ static bool io_run_local_work_continue(struct io_ring_ctx *ctx, int events,
 }
 
 static int __io_run_local_work_loop(struct llist_node **node,
-				    struct io_tw_state *ts,
+				    io_tw_token_t tw,
 				    int events)
 {
 	int ret = 0;
@@ -1288,7 +1288,7 @@ static int __io_run_local_work_loop(struct llist_node **node,
 						    io_task_work.node);
 		INDIRECT_CALL_2(req->io_task_work.func,
 				io_poll_task_func, io_req_rw_complete,
-				req, ts);
+				req, tw);
 		*node = next;
 		if (++ret >= events)
 			break;
@@ -1297,7 +1297,7 @@ static int __io_run_local_work_loop(struct llist_node **node,
 	return ret;
 }
 
-static int __io_run_local_work(struct io_ring_ctx *ctx, struct io_tw_state *ts,
+static int __io_run_local_work(struct io_ring_ctx *ctx, io_tw_token_t tw,
 			       int min_events, int max_events)
 {
 	struct llist_node *node;
@@ -1310,7 +1310,7 @@ static int __io_run_local_work(struct io_ring_ctx *ctx, struct io_tw_state *ts,
 		atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
 again:
 	min_events -= ret;
-	ret = __io_run_local_work_loop(&ctx->retry_llist.first, ts, max_events);
+	ret = __io_run_local_work_loop(&ctx->retry_llist.first, tw, max_events);
 	if (ctx->retry_llist.first)
 		goto retry_done;
 
@@ -1319,7 +1319,7 @@ static int __io_run_local_work(struct io_ring_ctx *ctx, struct io_tw_state *ts,
 	 * running the pending items.
 	 */
 	node = llist_reverse_order(llist_del_all(&ctx->work_llist));
-	ret += __io_run_local_work_loop(&node, ts, max_events - ret);
+	ret += __io_run_local_work_loop(&node, tw, max_events - ret);
 	ctx->retry_llist.first = node;
 	loops++;
 
@@ -1357,15 +1357,15 @@ static int io_run_local_work(struct io_ring_ctx *ctx, int min_events,
 	return ret;
 }
 
-static void io_req_task_cancel(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_req_task_cancel(struct io_kiocb *req, io_tw_token_t tw)
 {
-	io_tw_lock(req->ctx, ts);
+	io_tw_lock(req->ctx, tw);
 	io_req_defer_failed(req, req->cqe.res);
 }
 
-void io_req_task_submit(struct io_kiocb *req, struct io_tw_state *ts)
+void io_req_task_submit(struct io_kiocb *req, io_tw_token_t tw)
 {
-	io_tw_lock(req->ctx, ts);
+	io_tw_lock(req->ctx, tw);
 	if (unlikely(io_should_terminate_tw()))
 		io_req_defer_failed(req, -EFAULT);
 	else if (req->flags & REQ_F_FORCE_ASYNC)
@@ -1583,7 +1583,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
 	return 0;
 }
 
-void io_req_task_complete(struct io_kiocb *req, struct io_tw_state *ts)
+void io_req_task_complete(struct io_kiocb *req, io_tw_token_t tw)
 {
 	io_req_complete_defer(req);
 }
@@ -1763,9 +1763,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 	return ret;
 }
 
-int io_poll_issue(struct io_kiocb *req, struct io_tw_state *ts)
+int io_poll_issue(struct io_kiocb *req, io_tw_token_t tw)
 {
-	io_tw_lock(req->ctx, ts);
+	io_tw_lock(req->ctx, tw);
 	return io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_MULTISHOT|
 				 IO_URING_F_COMPLETE_DEFER);
 }

io_uring/io_uring.h

@@ -90,9 +90,9 @@ void io_req_task_work_add_remote(struct io_kiocb *req, struct io_ring_ctx *ctx,
 				 unsigned flags);
 bool io_alloc_async_data(struct io_kiocb *req);
 void io_req_task_queue(struct io_kiocb *req);
-void io_req_task_complete(struct io_kiocb *req, struct io_tw_state *ts);
+void io_req_task_complete(struct io_kiocb *req, io_tw_token_t tw);
 void io_req_task_queue_fail(struct io_kiocb *req, int ret);
-void io_req_task_submit(struct io_kiocb *req, struct io_tw_state *ts);
+void io_req_task_submit(struct io_kiocb *req, io_tw_token_t tw);
 struct llist_node *io_handle_tw_list(struct llist_node *node, unsigned int *count, unsigned int max_entries);
 struct llist_node *tctx_task_work_run(struct io_uring_task *tctx, unsigned int max_entries, unsigned int *count);
 void tctx_task_work(struct callback_head *cb);
@@ -104,7 +104,7 @@ int io_ring_add_registered_file(struct io_uring_task *tctx, struct file *file,
 				     int start, int end);
 void io_req_queue_iowq(struct io_kiocb *req);
 
-int io_poll_issue(struct io_kiocb *req, struct io_tw_state *ts);
+int io_poll_issue(struct io_kiocb *req, io_tw_token_t tw);
 int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr);
 int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin);
 void __io_submit_flush_completions(struct io_ring_ctx *ctx);
@@ -376,7 +376,7 @@ 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, struct io_tw_state *ts)
+static inline void io_tw_lock(struct io_ring_ctx *ctx, io_tw_token_t tw)
 {
 	lockdep_assert_held(&ctx->uring_lock);
 }

io_uring/msg_ring.c

@@ -71,7 +71,7 @@ static inline bool io_msg_need_remote(struct io_ring_ctx *target_ctx)
 	return target_ctx->task_complete;
 }
 
-static void io_msg_tw_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_msg_tw_complete(struct io_kiocb *req, io_tw_token_t tw)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 

io_uring/notif.c

@@ -11,7 +11,7 @@
 
 static const struct ubuf_info_ops io_ubuf_ops;
 
-static void io_notif_tw_complete(struct io_kiocb *notif, struct io_tw_state *ts)
+static void io_notif_tw_complete(struct io_kiocb *notif, io_tw_token_t tw)
 {
 	struct io_notif_data *nd = io_notif_to_data(notif);
 
@@ -29,7 +29,7 @@ static void io_notif_tw_complete(struct io_kiocb *notif, struct io_tw_state *ts)
 		}
 
 		nd = nd->next;
-		io_req_task_complete(notif, ts);
+		io_req_task_complete(notif, tw);
 	} while (nd);
 }
 

io_uring/poll.c

@@ -220,7 +220,7 @@ static inline void io_poll_execute(struct io_kiocb *req, int res)
  * req->cqe.res. IOU_POLL_REMOVE_POLL_USE_RES indicates to remove multishot
  * poll and that the result is stored in req->cqe.
  */
-static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
+static int io_poll_check_events(struct io_kiocb *req, io_tw_token_t tw)
 {
 	int v;
 
@@ -288,7 +288,7 @@ static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
 				return IOU_POLL_REMOVE_POLL_USE_RES;
 			}
 		} else {
-			int ret = io_poll_issue(req, ts);
+			int ret = io_poll_issue(req, tw);
 			if (ret == IOU_STOP_MULTISHOT)
 				return IOU_POLL_REMOVE_POLL_USE_RES;
 			else if (ret == IOU_REQUEUE)
@@ -311,11 +311,11 @@ static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
 	return IOU_POLL_NO_ACTION;
 }
 
-void io_poll_task_func(struct io_kiocb *req, struct io_tw_state *ts)
+void io_poll_task_func(struct io_kiocb *req, io_tw_token_t tw)
 {
 	int ret;
 
-	ret = io_poll_check_events(req, ts);
+	ret = io_poll_check_events(req, tw);
 	if (ret == IOU_POLL_NO_ACTION) {
 		io_kbuf_recycle(req, 0);
 		return;
@@ -335,22 +335,22 @@ void io_poll_task_func(struct io_kiocb *req, struct io_tw_state *ts)
 			poll = io_kiocb_to_cmd(req, struct io_poll);
 			req->cqe.res = mangle_poll(req->cqe.res & poll->events);
 		} else if (ret == IOU_POLL_REISSUE) {
-			io_req_task_submit(req, ts);
+			io_req_task_submit(req, tw);
 			return;
 		} else if (ret != IOU_POLL_REMOVE_POLL_USE_RES) {
 			req->cqe.res = ret;
 			req_set_fail(req);
 		}
 
 		io_req_set_res(req, req->cqe.res, 0);
-		io_req_task_complete(req, ts);
+		io_req_task_complete(req, tw);
 	} else {
-		io_tw_lock(req->ctx, ts);
+		io_tw_lock(req->ctx, tw);
 
 		if (ret == IOU_POLL_REMOVE_POLL_USE_RES)
-			io_req_task_complete(req, ts);
+			io_req_task_complete(req, tw);
 		else if (ret == IOU_POLL_DONE || ret == IOU_POLL_REISSUE)
-			io_req_task_submit(req, ts);
+			io_req_task_submit(req, tw);
 		else
 			io_req_defer_failed(req, ret);
 	}

io_uring/poll.h

@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <linux/io_uring_types.h>
+
 #define IO_POLL_ALLOC_CACHE_MAX 32
 
 enum {
@@ -43,4 +45,4 @@ int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags);
 bool io_poll_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx,
 			bool cancel_all);
 
-void io_poll_task_func(struct io_kiocb *req, struct io_tw_state *ts);
+void io_poll_task_func(struct io_kiocb *req, io_tw_token_t tw);

io_uring/rw.c

@@ -511,7 +511,7 @@ static inline int io_fixup_rw_res(struct io_kiocb *req, long res)
 	return res;
 }
 
-void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts)
+void io_req_rw_complete(struct io_kiocb *req, io_tw_token_t tw)
 {
 	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 	struct kiocb *kiocb = &rw->kiocb;
@@ -528,7 +528,7 @@ void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts)
 		req->cqe.flags |= io_put_kbuf(req, req->cqe.res, 0);
 
 	io_req_rw_cleanup(req, 0);
-	io_req_task_complete(req, ts);
+	io_req_task_complete(req, tw);
 }
 
 static void io_complete_rw(struct kiocb *kiocb, long res)

io_uring/rw.h

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <linux/io_uring_types.h>
 #include <linux/pagemap.h>
 
 struct io_meta_state {
@@ -39,7 +40,7 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags);
 int io_write(struct io_kiocb *req, unsigned int issue_flags);
 void io_readv_writev_cleanup(struct io_kiocb *req);
 void io_rw_fail(struct io_kiocb *req);
-void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts);
+void io_req_rw_complete(struct io_kiocb *req, io_tw_token_t tw);
 int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags);
 void io_rw_cache_free(const void *entry);