io_uring: add allow_overflow to io_post_aux_cqe

Some use cases of io_post_aux_cqe would not want to overflow as is, but
might want to change the flags/result. For example multishot receive
requires in order CQE, and so if there is an overflow it would need to
stop receiving until the overflow is taken care of.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220630091231.1456789-8-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -736,7 +736,8 @@ struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx)
 }
 
 static bool io_fill_cqe_aux(struct io_ring_ctx *ctx,
-			    u64 user_data, s32 res, u32 cflags)
+			    u64 user_data, s32 res, u32 cflags,
+			    bool allow_overflow)
 {
 	struct io_uring_cqe *cqe;
 
@@ -760,16 +761,21 @@ static bool io_fill_cqe_aux(struct io_ring_ctx *ctx,
 		}
 		return true;
 	}
-	return io_cqring_event_overflow(ctx, user_data, res, cflags, 0, 0);
+
+	if (allow_overflow)
+		return io_cqring_event_overflow(ctx, user_data, res, cflags, 0, 0);
+
+	return false;
 }
 
 bool io_post_aux_cqe(struct io_ring_ctx *ctx,
-		     u64 user_data, s32 res, u32 cflags)
+		     u64 user_data, s32 res, u32 cflags,
+		     bool allow_overflow)
 {
 	bool filled;
 
 	io_cq_lock(ctx);
-	filled = io_fill_cqe_aux(ctx, user_data, res, cflags);
+	filled = io_fill_cqe_aux(ctx, user_data, res, cflags, allow_overflow);
 	io_cq_unlock_post(ctx);
 	return filled;
 }

io_uring/io_uring.h

@@ -31,7 +31,8 @@ void io_req_complete_failed(struct io_kiocb *req, s32 res);
 void __io_req_complete(struct io_kiocb *req, unsigned issue_flags);
 void io_req_complete_post(struct io_kiocb *req);
 void __io_req_complete_post(struct io_kiocb *req);
-bool io_post_aux_cqe(struct io_ring_ctx *ctx, u64 user_data, s32 res, u32 cflags);
+bool io_post_aux_cqe(struct io_ring_ctx *ctx, u64 user_data, s32 res, u32 cflags,
+		     bool allow_overflow);
 void __io_commit_cqring_flush(struct io_ring_ctx *ctx);
 
 struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages);

io_uring/msg_ring.c

@@ -31,7 +31,7 @@ static int io_msg_ring_data(struct io_kiocb *req)
 	if (msg->src_fd || msg->dst_fd || msg->flags)
 		return -EINVAL;
 
-	if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0))
+	if (io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
 		return 0;
 
 	return -EOVERFLOW;
@@ -113,7 +113,7 @@ static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
 	 * completes with -EOVERFLOW, then the sender must ensure that a
 	 * later IORING_OP_MSG_RING delivers the message.
 	 */
-	if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0))
+	if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0, true))
 		ret = -EOVERFLOW;
 out_unlock:
 	io_double_unlock_ctx(ctx, target_ctx, issue_flags);

io_uring/net.c

@@ -658,7 +658,7 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags)
 
 	if (ret < 0)
 		return ret;
-	if (io_post_aux_cqe(ctx, req->cqe.user_data, ret, IORING_CQE_F_MORE))
+	if (io_post_aux_cqe(ctx, req->cqe.user_data, ret, IORING_CQE_F_MORE, true))
 		goto retry;
 	return -ECANCELED;
 }

io_uring/poll.c

@@ -243,7 +243,7 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
 						    req->apoll_events);
 
 			if (!io_post_aux_cqe(ctx, req->cqe.user_data,
-					     mask, IORING_CQE_F_MORE))
+					     mask, IORING_CQE_F_MORE, true))
 				return -ECANCELED;
 		} else {
 			ret = io_poll_issue(req, locked);

io_uring/rsrc.c

@@ -175,10 +175,10 @@ static void __io_rsrc_put_work(struct io_rsrc_node *ref_node)
 		if (prsrc->tag) {
 			if (ctx->flags & IORING_SETUP_IOPOLL) {
 				mutex_lock(&ctx->uring_lock);
-				io_post_aux_cqe(ctx, prsrc->tag, 0, 0);
+				io_post_aux_cqe(ctx, prsrc->tag, 0, 0, true);
 				mutex_unlock(&ctx->uring_lock);
 			} else {
-				io_post_aux_cqe(ctx, prsrc->tag, 0, 0);
+				io_post_aux_cqe(ctx, prsrc->tag, 0, 0, true);
 			}
 		}