io_uring/rsrc: remove node assignment helpers

There are two helpers here, one assigns and increments the node ref
count, and the other is simply a wrapper around that for the buffer node
handling.

The buffer node assignment benefits from checking and setting
REQ_F_BUF_NODE together, otherwise stalls have been observed on setting
that flag later in the process. Hence re-do it so that it's set when
checked, and cleared in case of (unlikely) failure. With that, the
buffer node helper can go, and then drop the generic
io_req_assign_rsrc_node() helper as well as there's only a single user
of it left at that point.

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

io_uring/io_uring.c

@@ -1912,7 +1912,8 @@ inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
 	io_ring_submit_lock(ctx, issue_flags);
 	node = io_rsrc_node_lookup(&ctx->file_table.data, fd);
 	if (node) {
-		io_req_assign_rsrc_node(&req->file_node, node);
+		node->refs++;
+		req->file_node = node;
 		req->flags |= io_slot_flags(node);
 		file = io_slot_file(node);
 	}

io_uring/rsrc.c

@@ -1110,13 +1110,19 @@ inline struct io_rsrc_node *io_find_buf_node(struct io_kiocb *req,
 
 	if (req->flags & REQ_F_BUF_NODE)
 		return req->buf_node;
+	req->flags |= REQ_F_BUF_NODE;
 
 	io_ring_submit_lock(ctx, issue_flags);
 	node = io_rsrc_node_lookup(&ctx->buf_table, req->buf_index);
-	if (node)
-		io_req_assign_buf_node(req, node);
+	if (node) {
+		node->refs++;
+		req->buf_node = node;
+		io_ring_submit_unlock(ctx, issue_flags);
+		return node;
+	}
+	req->flags &= ~REQ_F_BUF_NODE;
 	io_ring_submit_unlock(ctx, issue_flags);
-	return node;
+	return NULL;
 }
 
 int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,

io_uring/rsrc.h

@@ -127,20 +127,6 @@ static inline void io_req_put_rsrc_nodes(struct io_kiocb *req)
 	}
 }
 
-static inline void io_req_assign_rsrc_node(struct io_rsrc_node **dst_node,
-					   struct io_rsrc_node *node)
-{
-	node->refs++;
-	*dst_node = node;
-}
-
-static inline void io_req_assign_buf_node(struct io_kiocb *req,
-					  struct io_rsrc_node *node)
-{
-	io_req_assign_rsrc_node(&req->buf_node, node);
-	req->flags |= REQ_F_BUF_NODE;
-}
-
 int io_files_update(struct io_kiocb *req, unsigned int issue_flags);
 int io_files_update_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);