io_uring: flush notifiers after sendzc

Allow to flush notifiers as a part of sendzc request by setting
IORING_SENDZC_FLUSH flag. When the sendzc request succeedes it will
flush the used [active] notifier.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e0b4d9a6797e2fd6092824fe42953db7a519bbc8.1657643355.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/uapi/linux/io_uring.h

@@ -275,10 +275,14 @@ enum io_uring_op {
  *
  * IORING_RECVSEND_FIXED_BUF	Use registered buffers, the index is stored in
  *				the buf_index field.
+ *
+ * IORING_RECVSEND_NOTIF_FLUSH	Flush a notification after a successful
+ *				successful. Only for zerocopy sends.
  */
 #define IORING_RECVSEND_POLL_FIRST	(1U << 0)
 #define IORING_RECV_MULTISHOT		(1U << 1)
 #define IORING_RECVSEND_FIXED_BUF	(1U << 2)
+#define IORING_RECVSEND_NOTIF_FLUSH	(1U << 3)
 
 /*
  * accept flags stored in sqe->ioprio

io_uring/io_uring.c

@@ -621,7 +621,7 @@ void __io_put_task(struct task_struct *task, int nr)
 	put_task_struct_many(task, nr);
 }
 
-static void io_task_refs_refill(struct io_uring_task *tctx)
+void io_task_refs_refill(struct io_uring_task *tctx)
 {
 	unsigned int refill = -tctx->cached_refs + IO_TCTX_REFS_CACHE_NR;
 
@@ -630,15 +630,6 @@ static void io_task_refs_refill(struct io_uring_task *tctx)
 	tctx->cached_refs += refill;
 }
 
-static inline void io_get_task_refs(int nr)
-{
-	struct io_uring_task *tctx = current->io_uring;
-
-	tctx->cached_refs -= nr;
-	if (unlikely(tctx->cached_refs < 0))
-		io_task_refs_refill(tctx);
-}
-
 static __cold void io_uring_drop_tctx_refs(struct task_struct *task)
 {
 	struct io_uring_task *tctx = task->io_uring;

io_uring/io_uring.h

@@ -74,6 +74,7 @@ void io_wq_submit_work(struct io_wq_work *work);
 void io_free_req(struct io_kiocb *req);
 void io_queue_next(struct io_kiocb *req);
 void __io_put_task(struct task_struct *task, int nr);
+void io_task_refs_refill(struct io_uring_task *tctx);
 
 bool io_match_task_safe(struct io_kiocb *head, struct task_struct *task,
 			bool cancel_all);
@@ -270,4 +271,13 @@ static inline void io_put_task(struct task_struct *task, int nr)
 		__io_put_task(task, nr);
 }
 
+static inline void io_get_task_refs(int nr)
+{
+	struct io_uring_task *tctx = current->io_uring;
+
+	tctx->cached_refs -= nr;
+	if (unlikely(tctx->cached_refs < 0))
+		io_task_refs_refill(tctx);
+}
+
 #endif

io_uring/net.c

@@ -856,7 +856,8 @@ int io_sendzc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	zc->flags = READ_ONCE(sqe->ioprio);
-	if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST | IORING_RECVSEND_FIXED_BUF))
+	if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST |
+			  IORING_RECVSEND_FIXED_BUF | IORING_RECVSEND_NOTIF_FLUSH))
 		return -EINVAL;
 	if (zc->flags & IORING_RECVSEND_FIXED_BUF) {
 		unsigned idx = READ_ONCE(sqe->buf_index);
@@ -958,6 +959,8 @@ int io_sendzc(struct io_kiocb *req, unsigned int issue_flags)
 		return ret == -ERESTARTSYS ? -EINTR : ret;
 	}
 
+	if (zc->flags & IORING_RECVSEND_NOTIF_FLUSH)
+		io_notif_slot_flush_submit(notif_slot, 0);
 	io_req_set_res(req, ret, 0);
 	return IOU_OK;
 }

io_uring/notif.c

@@ -133,7 +133,7 @@ struct io_notif *io_alloc_notif(struct io_ring_ctx *ctx,
 	return notif;
 }
 
-static void io_notif_slot_flush(struct io_notif_slot *slot)
+void io_notif_slot_flush(struct io_notif_slot *slot)
 	__must_hold(&ctx->uring_lock)
 {
 	struct io_notif *notif = slot->notif;

io_uring/notif.h

@@ -54,6 +54,7 @@ int io_notif_register(struct io_ring_ctx *ctx,
 int io_notif_unregister(struct io_ring_ctx *ctx);
 void io_notif_cache_purge(struct io_ring_ctx *ctx);
 
+void io_notif_slot_flush(struct io_notif_slot *slot);
 struct io_notif *io_alloc_notif(struct io_ring_ctx *ctx,
 				struct io_notif_slot *slot);
 
@@ -74,3 +75,13 @@ static inline struct io_notif_slot *io_get_notif_slot(struct io_ring_ctx *ctx,
 	idx = array_index_nospec(idx, ctx->nr_notif_slots);
 	return &ctx->notif_slots[idx];
 }
+
+static inline void io_notif_slot_flush_submit(struct io_notif_slot *slot,
+					      unsigned int issue_flags)
+{
+	if (!(issue_flags & IO_URING_F_UNLOCKED)) {
+		slot->notif->task = current;
+		io_get_task_refs(1);
+	}
+	io_notif_slot_flush(slot);
+}