[PATCH] io_uring: pass struct io_tw_state by value

[PATCH] io_uring: pass struct io_tw_state by value

[Caleb Sander Mateos]

8e5b3b89ecaf ("io_uring: remove struct io_tw_state::locked") removed the
only field of io_tw_state but kept it as a task work callback argument
to "forc[e] users not to invoke them carelessly out of a wrong context".
Passing the struct io_tw_state * argument adds a few instructions to all
callers that can't inline the functions and see the argument is unused.

So pass struct io_tw_state by value instead. Since it's a 0-sized value,
it can be passed without any instructions needed to initialize it.

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

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 include/linux/io_uring_types.h |  3 ++-
 io_uring/futex.c               |  6 +++---
 io_uring/io_uring.c            | 30 +++++++++++++++---------------
 io_uring/io_uring.h            |  8 ++++----
 io_uring/msg_ring.c            |  2 +-
 io_uring/notif.c               |  2 +-
 io_uring/poll.c                |  4 ++--
 io_uring/poll.h                |  2 +-
 io_uring/rw.c                  |  2 +-
 io_uring/rw.h                  |  2 +-
 io_uring/timeout.c             |  6 +++---
 io_uring/uring_cmd.c           |  2 +-
 io_uring/waitid.c              |  6 +++---
 13 files changed, 38 insertions(+), 37 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index e2fef264ff8b..4abd0299fdfb 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -434,10 +434,11 @@ struct io_ring_ctx {
 	struct io_mapped_region		ring_region;
 	/* used for optimised request parameter and wait argument passing  */
 	struct io_mapped_region		param_region;
 };
 
+/* Token passed to task work callbacks to indicate ctx->uring_lock is held */
 struct io_tw_state {
 };
 
 enum {
 	REQ_F_FIXED_FILE_BIT	= IOSQE_FIXED_FILE_BIT,
@@ -561,11 +562,11 @@ enum {
 	REQ_F_BUF_NODE		= IO_REQ_FLAG(REQ_F_BUF_NODE_BIT),
 	/* request has read/write metadata assigned */
 	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, struct io_tw_state ts);
 
 struct io_task_work {
 	struct llist_node		node;
 	io_req_tw_func_t		func;
 };
diff --git a/io_uring/futex.c b/io_uring/futex.c
index 54b9760f2aa6..d4f9591c821f 100644
--- a/io_uring/futex.c
+++ b/io_uring/futex.c
@@ -42,29 +42,29 @@ bool io_futex_cache_init(struct io_ring_ctx *ctx)
 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, struct io_tw_state ts)
 {
 	req->async_data = NULL;
 	hlist_del_init(&req->hash_node);
 	io_req_task_complete(req, ts);
 }
 
-static void io_futex_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_futex_complete(struct io_kiocb *req, struct io_tw_state ts)
 {
 	struct io_futex_data *ifd = req->async_data;
 	struct io_ring_ctx *ctx = req->ctx;
 
 	io_tw_lock(ctx, ts);
 	if (!io_alloc_cache_put(&ctx->futex_cache, ifd))
 		kfree(ifd);
 	__io_futex_complete(req, ts);
 }
 
-static void io_futexv_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_futexv_complete(struct io_kiocb *req, struct io_tw_state ts)
 {
 	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);
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index ec98a0ec6f34..578f894a3bdb 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -252,11 +252,11 @@ static __cold void io_fallback_req_func(struct work_struct *work)
 	struct io_tw_state ts = {};
 
 	percpu_ref_get(&ctx->refs);
 	mutex_lock(&ctx->uring_lock);
 	llist_for_each_entry_safe(req, tmp, node, io_task_work.node)
-		req->io_task_work.func(req, &ts);
+		req->io_task_work.func(req, ts);
 	io_submit_flush_completions(ctx);
 	mutex_unlock(&ctx->uring_lock);
 	percpu_ref_put(&ctx->refs);
 }
 
@@ -540,11 +540,11 @@ static void io_queue_iowq(struct io_kiocb *req)
 	io_wq_enqueue(tctx->io_wq, &req->work);
 	if (link)
 		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, struct io_tw_state ts)
 {
 	io_queue_iowq(req);
 }
 
 void io_req_queue_iowq(struct io_kiocb *req)
@@ -1019,11 +1019,11 @@ static inline struct io_kiocb *io_req_find_next(struct io_kiocb *req)
 	nxt = req->link;
 	req->link = NULL;
 	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, struct io_tw_state ts)
 {
 	if (!ctx)
 		return;
 	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
 		atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
@@ -1049,28 +1049,28 @@ struct llist_node *io_handle_tw_list(struct llist_node *node,
 		struct llist_node *next = node->next;
 		struct io_kiocb *req = container_of(node, struct io_kiocb,
 						    io_task_work.node);
 
 		if (req->ctx != ctx) {
-			ctx_flush_and_put(ctx, &ts);
+			ctx_flush_and_put(ctx, ts);
 			ctx = req->ctx;
 			mutex_lock(&ctx->uring_lock);
 			percpu_ref_get(&ctx->refs);
 		}
 		INDIRECT_CALL_2(req->io_task_work.func,
 				io_poll_task_func, io_req_rw_complete,
-				req, &ts);
+				req, ts);
 		node = next;
 		(*count)++;
 		if (unlikely(need_resched())) {
-			ctx_flush_and_put(ctx, &ts);
+			ctx_flush_and_put(ctx, ts);
 			ctx = NULL;
 			cond_resched();
 		}
 	} while (node && *count < max_entries);
 
-	ctx_flush_and_put(ctx, &ts);
+	ctx_flush_and_put(ctx, ts);
 	return node;
 }
 
 static __cold void __io_fallback_tw(struct llist_node *node, bool sync)
 {
@@ -1274,11 +1274,11 @@ static bool io_run_local_work_continue(struct io_ring_ctx *ctx, int events,
 		atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
 	return false;
 }
 
 static int __io_run_local_work_loop(struct llist_node **node,
-				    struct io_tw_state *ts,
+				    struct io_tw_state ts,
 				    int events)
 {
 	int ret = 0;
 
 	while (*node) {
@@ -1294,11 +1294,11 @@ 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, struct io_tw_state ts,
 			       int min_events, int max_events)
 {
 	struct llist_node *node;
 	unsigned int loops = 0;
 	int ret = 0;
@@ -1338,33 +1338,33 @@ static inline int io_run_local_work_locked(struct io_ring_ctx *ctx,
 {
 	struct io_tw_state ts = {};
 
 	if (!io_local_work_pending(ctx))
 		return 0;
-	return __io_run_local_work(ctx, &ts, min_events,
+	return __io_run_local_work(ctx, ts, min_events,
 					max(IO_LOCAL_TW_DEFAULT_MAX, min_events));
 }
 
 static int io_run_local_work(struct io_ring_ctx *ctx, int min_events,
 			     int max_events)
 {
 	struct io_tw_state ts = {};
 	int ret;
 
 	mutex_lock(&ctx->uring_lock);
-	ret = __io_run_local_work(ctx, &ts, min_events, max_events);
+	ret = __io_run_local_work(ctx, ts, min_events, max_events);
 	mutex_unlock(&ctx->uring_lock);
 	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, struct io_tw_state ts)
 {
 	io_tw_lock(req->ctx, ts);
 	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, struct io_tw_state ts)
 {
 	io_tw_lock(req->ctx, ts);
 	if (unlikely(io_should_terminate_tw()))
 		io_req_defer_failed(req, -EFAULT);
 	else if (req->flags & REQ_F_FORCE_ASYNC)
@@ -1580,11 +1580,11 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
 	} while (nr_events < 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, struct io_tw_state ts)
 {
 	io_req_complete_defer(req);
 }
 
 /*
@@ -1760,11 +1760,11 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 			io_iopoll_req_issued(req, 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, struct io_tw_state ts)
 {
 	io_tw_lock(req->ctx, ts);
 	return io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_MULTISHOT|
 				 IO_URING_F_COMPLETE_DEFER);
 }
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 85bc8f76ca19..230653b97d12 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -88,13 +88,13 @@ struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
 void __io_req_task_work_add(struct io_kiocb *req, unsigned flags);
 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, struct io_tw_state ts);
 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, struct io_tw_state ts);
 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);
 __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd);
 int io_uring_alloc_task_context(struct task_struct *task,
@@ -102,11 +102,11 @@ int io_uring_alloc_task_context(struct task_struct *task,
 
 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, struct io_tw_state ts);
 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);
 
 struct io_wq_work *io_wq_free_work(struct io_wq_work *work);
@@ -374,11 +374,11 @@ static inline bool io_local_work_pending(struct io_ring_ctx *ctx)
 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, struct io_tw_state ts)
 {
 	lockdep_assert_held(&ctx->uring_lock);
 }
 
 /*
diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index 7e6f68e911f1..aae1e7f84615 100644
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -69,11 +69,11 @@ void io_msg_ring_cleanup(struct io_kiocb *req)
 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, struct io_tw_state ts)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 
 	io_add_aux_cqe(ctx, req->cqe.user_data, req->cqe.res, req->cqe.flags);
 	if (spin_trylock(&ctx->msg_lock)) {
diff --git a/io_uring/notif.c b/io_uring/notif.c
index ee3a33510b3c..c3460b295dcc 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -9,11 +9,11 @@
 #include "notif.h"
 #include "rsrc.h"
 
 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, struct io_tw_state ts)
 {
 	struct io_notif_data *nd = io_notif_to_data(notif);
 
 	do {
 		notif = cmd_to_io_kiocb(nd);
diff --git a/io_uring/poll.c b/io_uring/poll.c
index bb1c0cd4f809..bc5e0125db3f 100644
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -218,11 +218,11 @@ static inline void io_poll_execute(struct io_kiocb *req, int res)
  * require, which is either spurious wakeup or multishot CQE is served.
  * IOU_POLL_DONE when it's done with the request, then the mask is stored in
  * 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, struct io_tw_state ts)
 {
 	int v;
 
 	if (unlikely(io_should_terminate_tw()))
 		return -ECANCELED;
@@ -309,11 +309,11 @@ static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
 
 	io_napi_add(req);
 	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, struct io_tw_state ts)
 {
 	int ret;
 
 	ret = io_poll_check_events(req, ts);
 	if (ret == IOU_POLL_NO_ACTION) {
diff --git a/io_uring/poll.h b/io_uring/poll.h
index 04ede93113dc..7825688aab3d 100644
--- a/io_uring/poll.h
+++ b/io_uring/poll.h
@@ -41,6 +41,6 @@ int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
 		   unsigned issue_flags);
 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, struct io_tw_state ts);
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 7aa1e4c9f64a..17f08b3b754f 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -509,11 +509,11 @@ static inline int io_fixup_rw_res(struct io_kiocb *req, long res)
 			res += io->bytes_done;
 	}
 	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, struct io_tw_state ts)
 {
 	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 	struct kiocb *kiocb = &rw->kiocb;
 
 	if ((kiocb->ki_flags & IOCB_DIO_CALLER_COMP) && kiocb->dio_complete) {
diff --git a/io_uring/rw.h b/io_uring/rw.h
index eaa59bd64870..e0c1d760cbc2 100644
--- a/io_uring/rw.h
+++ b/io_uring/rw.h
@@ -37,9 +37,9 @@ int io_prep_read(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_prep_write(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 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, struct io_tw_state ts);
 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);
diff --git a/io_uring/timeout.c b/io_uring/timeout.c
index 48fc8cf70784..31fadd3342a5 100644
--- a/io_uring/timeout.c
+++ b/io_uring/timeout.c
@@ -63,11 +63,11 @@ static inline bool io_timeout_finish(struct io_timeout *timeout,
 	return true;
 }
 
 static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer);
 
-static void io_timeout_complete(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_timeout_complete(struct io_kiocb *req, struct io_tw_state ts)
 {
 	struct io_timeout *timeout = io_kiocb_to_cmd(req, struct io_timeout);
 	struct io_timeout_data *data = req->async_data;
 	struct io_ring_ctx *ctx = req->ctx;
 
@@ -152,11 +152,11 @@ __cold void io_flush_timeouts(struct io_ring_ctx *ctx)
 	ctx->cq_last_tm_flush = seq;
 	raw_spin_unlock_irq(&ctx->timeout_lock);
 	io_flush_killed_timeouts(&list, 0);
 }
 
-static void io_req_tw_fail_links(struct io_kiocb *link, struct io_tw_state *ts)
+static void io_req_tw_fail_links(struct io_kiocb *link, struct io_tw_state ts)
 {
 	io_tw_lock(link->ctx, ts);
 	while (link) {
 		struct io_kiocb *nxt = link->link;
 		long res = -ECANCELED;
@@ -310,11 +310,11 @@ int io_timeout_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd)
 		return PTR_ERR(req);
 	io_req_task_queue_fail(req, -ECANCELED);
 	return 0;
 }
 
-static void io_req_task_link_timeout(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_req_task_link_timeout(struct io_kiocb *req, struct io_tw_state ts)
 {
 	struct io_timeout *timeout = io_kiocb_to_cmd(req, struct io_timeout);
 	struct io_kiocb *prev = timeout->prev;
 	int ret;
 
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 1f6a82128b47..0a6688b72041 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -103,11 +103,11 @@ void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
 		io_ring_submit_unlock(ctx, issue_flags);
 	}
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_mark_cancelable);
 
-static void io_uring_cmd_work(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_uring_cmd_work(struct io_kiocb *req, struct io_tw_state ts)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 	unsigned int flags = IO_URING_F_COMPLETE_DEFER;
 
 	if (io_should_terminate_tw())
diff --git a/io_uring/waitid.c b/io_uring/waitid.c
index 4fb465b48560..8b2f606b047b 100644
--- a/io_uring/waitid.c
+++ b/io_uring/waitid.c
@@ -14,11 +14,11 @@
 #include "io_uring.h"
 #include "cancel.h"
 #include "waitid.h"
 #include "../kernel/exit.h"
 
-static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts);
+static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state ts);
 
 #define IO_WAITID_CANCEL_FLAG	BIT(31)
 #define IO_WAITID_REF_MASK	GENMASK(30, 0)
 
 struct io_waitid {
@@ -129,11 +129,11 @@ static void io_waitid_complete(struct io_kiocb *req, int ret)
 
 	ret = io_waitid_finish(req, ret);
 	if (ret < 0)
 		req_set_fail(req);
 	io_req_set_res(req, ret, 0);
-	io_req_task_complete(req, &ts);
+	io_req_task_complete(req, ts);
 }
 
 static bool __io_waitid_cancel(struct io_kiocb *req)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
@@ -184,11 +184,11 @@ static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
 	io_req_task_work_add(req);
 	remove_wait_queue(iw->head, &iwa->wo.child_wait);
 	return true;
 }
 
-static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts)
+static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state ts)
 {
 	struct io_waitid_async *iwa = req->async_data;
 	struct io_ring_ctx *ctx = req->ctx;
 	int ret;
 
-- 
2.45.2

Re: [PATCH] io_uring: pass struct io_tw_state by value

[Pavel Begunkov]

On 2/11/25 21:45, Caleb Sander Mateos wrote:
...
> --- a/io_uring/waitid.c
> +++ b/io_uring/waitid.c
> @@ -14,11 +14,11 @@
>   #include "io_uring.h"
>   #include "cancel.h"
>   #include "waitid.h"
>   #include "../kernel/exit.h"
>   
> -static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts);
> +static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state ts);
>   
>   #define IO_WAITID_CANCEL_FLAG	BIT(31)
>   #define IO_WAITID_REF_MASK	GENMASK(30, 0)
>   
>   struct io_waitid {
> @@ -129,11 +129,11 @@ static void io_waitid_complete(struct io_kiocb *req, int ret)
>   
>   	ret = io_waitid_finish(req, ret);
>   	if (ret < 0)
>   		req_set_fail(req);
>   	io_req_set_res(req, ret, 0);
> -	io_req_task_complete(req, &ts);

This thing will need to be fixed first


> +	io_req_task_complete(req, ts);
>   }

-- 
Pavel Begunkov

Re: [PATCH] io_uring: pass struct io_tw_state by value

[Jens Axboe]

On 2/11/25 2:45 PM, Caleb Sander Mateos wrote:
> 8e5b3b89ecaf ("io_uring: remove struct io_tw_state::locked") removed the
> only field of io_tw_state but kept it as a task work callback argument
> to "forc[e] users not to invoke them carelessly out of a wrong context".
> Passing the struct io_tw_state * argument adds a few instructions to all
> callers that can't inline the functions and see the argument is unused.
> 
> So pass struct io_tw_state by value instead. Since it's a 0-sized value,
> it can be passed without any instructions needed to initialize it.
> 
> Also add a comment to struct io_tw_state to explain its purpose.

This is nice, reduces the code generated. It'll conflict with the
fix that Pavel posted, but I can just mangle this one once I get
the 6.15 branch rebased on top of -rc3. No need to send a v2.

-- 
Jens Axboe

Re: [PATCH] io_uring: pass struct io_tw_state by value

[Pavel Begunkov]

On 2/12/25 14:33, Jens Axboe wrote:
> On 2/11/25 2:45 PM, Caleb Sander Mateos wrote:
>> 8e5b3b89ecaf ("io_uring: remove struct io_tw_state::locked") removed the
>> only field of io_tw_state but kept it as a task work callback argument
>> to "forc[e] users not to invoke them carelessly out of a wrong context".
>> Passing the struct io_tw_state * argument adds a few instructions to all
>> callers that can't inline the functions and see the argument is unused.
>>
>> So pass struct io_tw_state by value instead. Since it's a 0-sized value,
>> it can be passed without any instructions needed to initialize it.
>>
>> Also add a comment to struct io_tw_state to explain its purpose.
> 
> This is nice, reduces the code generated. It'll conflict with the
> fix that Pavel posted, but I can just mangle this one once I get
> the 6.15 branch rebased on top of -rc3. No need to send a v2.

Hold on this one, we're better to adjust the patch, I'll
follow up later today.

-- 
Pavel Begunkov

Re: [PATCH] io_uring: pass struct io_tw_state by value

[Jens Axboe]

On 2/12/25 7:49 AM, Pavel Begunkov wrote:
> On 2/12/25 14:33, Jens Axboe wrote:
>> On 2/11/25 2:45 PM, Caleb Sander Mateos wrote:
>>> 8e5b3b89ecaf ("io_uring: remove struct io_tw_state::locked") removed the
>>> only field of io_tw_state but kept it as a task work callback argument
>>> to "forc[e] users not to invoke them carelessly out of a wrong context".
>>> Passing the struct io_tw_state * argument adds a few instructions to all
>>> callers that can't inline the functions and see the argument is unused.
>>>
>>> So pass struct io_tw_state by value instead. Since it's a 0-sized value,
>>> it can be passed without any instructions needed to initialize it.
>>>
>>> Also add a comment to struct io_tw_state to explain its purpose.
>>
>> This is nice, reduces the code generated. It'll conflict with the
>> fix that Pavel posted, but I can just mangle this one once I get
>> the 6.15 branch rebased on top of -rc3. No need to send a v2.
> 
> Hold on this one, we're better to adjust the patch, I'll
> follow up later today.

Sure no problem, it'll be early next week on the 6.15 front anyway,
nothing is being committed right now.


-- 
Jens Axboe

Re: [PATCH] io_uring: pass struct io_tw_state by value

[Pavel Begunkov]

On 2/11/25 21:45, Caleb Sander Mateos wrote:
> 8e5b3b89ecaf ("io_uring: remove struct io_tw_state::locked") removed the
> only field of io_tw_state but kept it as a task work callback argument
> to "forc[e] users not to invoke them carelessly out of a wrong context".

The other unnamed reason was to limit the mess from io_uring wide
changes while it might still be used later on. It's always a pain
for backporting, so if we're doing that we might as well make it
easily convertible for future plans. Let's do

typedef struct io_tw_state iou_state_t;

Might be useful for leaking it to cmds as well.

> Passing the struct io_tw_state * argument adds a few instructions to all
> callers that can't inline the functions and see the argument is unused.
> 
> So pass struct io_tw_state by value instead. Since it's a 0-sized value,
> it can be passed without any instructions needed to initialize it.
> 
> Also add a comment to struct io_tw_state to explain its purpose.
> 
> Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
> ---
>   include/linux/io_uring_types.h |  3 ++-
>   io_uring/futex.c               |  6 +++---
>   io_uring/io_uring.c            | 30 +++++++++++++++---------------
>   io_uring/io_uring.h            |  8 ++++----
>   io_uring/msg_ring.c            |  2 +-
>   io_uring/notif.c               |  2 +-
>   io_uring/poll.c                |  4 ++--
>   io_uring/poll.h                |  2 +-
>   io_uring/rw.c                  |  2 +-
>   io_uring/rw.h                  |  2 +-
>   io_uring/timeout.c             |  6 +++---
>   io_uring/uring_cmd.c           |  2 +-
>   io_uring/waitid.c              |  6 +++---
>   13 files changed, 38 insertions(+), 37 deletions(-)
> 
> diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
> index e2fef264ff8b..4abd0299fdfb 100644
> --- a/include/linux/io_uring_types.h
> +++ b/include/linux/io_uring_types.h
> @@ -434,10 +434,11 @@ struct io_ring_ctx {
>   	struct io_mapped_region		ring_region;
>   	/* used for optimised request parameter and wait argument passing  */
>   	struct io_mapped_region		param_region;
>   };
>   
> +/* Token passed to task work callbacks to indicate ctx->uring_lock is held */

It indicates the current context not locking specifically, which is
why the chunk from waitid as below is not correct:

mutex_lock(uring_lock);
struct io_tw_state dummy;
io_uring_core_helper(&dummy);
mutex_unlock(uring_lock);


Probably something like "Token passed around to indicate the current
io_uring execution context". And it doesn't need to be more specific
as long as type system works for us. It might be a good idea to add
a note in bold that nobody outside of core io_uring is allowed
creating it, though it'll be ignored anyway.

>   struct io_tw_state {
>   };


-- 
Pavel Begunkov