io_uring: trace cqe overflows

Trace cqe overflows in io_uring. Print ocqe before the check, so if it is
NULL it indicates that it has been dropped.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220421091345.2115755-3-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2107,6 +2107,7 @@ static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
 	struct io_overflow_cqe *ocqe;
 
 	ocqe = kmalloc(sizeof(*ocqe), GFP_ATOMIC | __GFP_ACCOUNT);
+	trace_io_uring_cqe_overflow(ctx, user_data, res, cflags, ocqe);
 	if (!ocqe) {
 		/*
 		 * If we're in ring overflow flush mode, or in task cancel mode,