io_uring: simplify io_get_sqring

 * used, it's important that those reads are done through READ_ONCE() to

 * prevent a re-load down the line.

 */

static bool io_get_sqring(struct io_ring_ctx *ctx, struct io_kiocb *req,

			  const struct io_uring_sqe **sqe_ptr)

static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)

{

	u32 *sq_array = ctx->sq_array;

	unsigned head;

	 *    though the application is the one updating it.

	 */

	head = READ_ONCE(sq_array[ctx->cached_sq_head & ctx->sq_mask]);

	if (likely(head < ctx->sq_entries)) {

		/*

		 * All io need record the previous position, if LINK vs DARIN,

		 * it can be used to mark the position of the first IO in the

		 * link list.

		 */

		req->sequence = ctx->cached_sq_head;

		*sqe_ptr = &ctx->sq_sqes[head];

		req->opcode = READ_ONCE((*sqe_ptr)->opcode);

		req->user_data = READ_ONCE((*sqe_ptr)->user_data);

		ctx->cached_sq_head++;

		return true;

	}

	if (likely(head < ctx->sq_entries))

		return &ctx->sq_sqes[head];

	/* drop invalid entries */

	ctx->cached_sq_head++;

	ctx->cached_sq_dropped++;

	WRITE_ONCE(ctx->rings->sq_dropped, ctx->cached_sq_dropped);

	return false;

	return NULL;

}

static inline void io_consume_sqe(struct io_ring_ctx *ctx)

{

	ctx->cached_sq_head++;

}

static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,

				submitted = -EAGAIN;

			break;

		}

		if (!io_get_sqring(ctx, req, &sqe)) {

		sqe = io_get_sqe(ctx);

		if (!sqe) {

			__io_req_do_free(req);

			io_consume_sqe(ctx);

			break;

		}

		/*

		 * All io need record the previous position, if LINK vs DARIN,

		 * it can be used to mark the position of the first IO in the

		 * link list.

		 */

		req->sequence = ctx->cached_sq_head;

		req->opcode = READ_ONCE(sqe->opcode);

		req->user_data = READ_ONCE(sqe->user_data);

		io_consume_sqe(ctx);

		/* will complete beyond this point, count as submitted */

		submitted++;