io_uring: mark known and harmless racy ctx->int_flags uses

There are a few of these, where flags are read outside of the
uring_lock, yet it's harmless to race on them.

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

Author: axboe

io_uring/io_uring.c

@@ -2242,7 +2242,7 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 	struct io_ring_ctx *ctx = file->private_data;
 	__poll_t mask = 0;
 
-	if (unlikely(!(ctx->int_flags & IO_RING_F_POLL_ACTIVATED)))
+	if (unlikely(!(data_race(ctx->int_flags) & IO_RING_F_POLL_ACTIVATED)))
 		io_activate_pollwq(ctx);
 	/*
 	 * provides mb() which pairs with barrier from wq_has_sleeper

io_uring/io_uring.h

@@ -470,11 +470,12 @@ static inline void io_req_complete_defer(struct io_kiocb *req)
 	wq_list_add_tail(&req->comp_list, &state->compl_reqs);
 }
 
+#define SHOULD_FLUSH_MASK	(IO_RING_F_OFF_TIMEOUT_USED | \
+				 IO_RING_F_HAS_EVFD | IO_RING_F_POLL_ACTIVATED)
+
 static inline void io_commit_cqring_flush(struct io_ring_ctx *ctx)
 {
-	if (unlikely(ctx->int_flags & (IO_RING_F_OFF_TIMEOUT_USED |
-				       IO_RING_F_HAS_EVFD |
-				       IO_RING_F_POLL_ACTIVATED)))
+	if (unlikely(data_race(ctx->int_flags) & SHOULD_FLUSH_MASK))
 		__io_commit_cqring_flush(ctx);
 }
 

io_uring/tw.c

@@ -222,7 +222,7 @@ void io_req_local_work_add(struct io_kiocb *req, unsigned flags)
 
 	if (!head) {
 		io_ctx_mark_taskrun(ctx);
-		if (ctx->int_flags & IO_RING_F_HAS_EVFD)
+		if (data_race(ctx->int_flags) & IO_RING_F_HAS_EVFD)
 			io_eventfd_signal(ctx, false);
 	}