io_uring/cancel: de-unionize file and user_data in struct io_cancel_data

By having them share the same space in struct io_cancel_data, it ends up
disallowing IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_USERDATA from
working. Eg you cannot match on both a file and user_data for
cancelation purposes. This obviously isn't a common use case as nobody
has reported this, but it does result in -ENOENT potentially being
returned when trying to match on both, rather than actually doing what
the API says it would.

Fixes: 4bf9461 ("io_uring: allow IORING_OP_ASYNC_CANCEL with 'fd' key")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/cancel.h

@@ -6,10 +6,8 @@
 
 struct io_cancel_data {
 	struct io_ring_ctx *ctx;
-	union {
-		u64 data;
-		struct file *file;
-	};
+	u64 data;
+	struct file *file;
 	u8 opcode;
 	u32 flags;
 	int seq;