io_uring: modularize io_sqe_buffers_register

Move allocation of buffer management structures, and validation of
buffers into separate routines.
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -8579,13 +8579,8 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
 	return ret;
 }
 
-static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
-				   unsigned int nr_args)
+static int io_buffers_map_alloc(struct io_ring_ctx *ctx, unsigned int nr_args)
 {
-	int i, ret;
-	struct iovec iov;
-	struct page *last_hpage = NULL;
-
 	if (ctx->user_bufs)
 		return -EBUSY;
 	if (!nr_args || nr_args > UIO_MAXIOV)
@@ -8596,6 +8591,37 @@ static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 	if (!ctx->user_bufs)
 		return -ENOMEM;
 
+	return 0;
+}
+
+static int io_buffer_validate(struct iovec *iov)
+{
+	/*
+	 * Don't impose further limits on the size and buffer
+	 * constraints here, we'll -EINVAL later when IO is
+	 * submitted if they are wrong.
+	 */
+	if (!iov->iov_base || !iov->iov_len)
+		return -EFAULT;
+
+	/* arbitrary limit, but we need something */
+	if (iov->iov_len > SZ_1G)
+		return -EFAULT;
+
+	return 0;
+}
+
+static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
+				   unsigned int nr_args)
+{
+	int i, ret;
+	struct iovec iov;
+	struct page *last_hpage = NULL;
+
+	ret = io_buffers_map_alloc(ctx, nr_args);
+	if (ret)
+		return ret;
+
 	for (i = 0; i < nr_args; i++) {
 		struct io_mapped_ubuf *imu = &ctx->user_bufs[i];
 
@@ -8603,17 +8629,8 @@ static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 		if (ret)
 			break;
 
-		/*
-		 * Don't impose further limits on the size and buffer
-		 * constraints here, we'll -EINVAL later when IO is
-		 * submitted if they are wrong.
-		 */
-		ret = -EFAULT;
-		if (!iov.iov_base || !iov.iov_len)
-			break;
-
-		/* arbitrary limit, but we need something */
-		if (iov.iov_len > SZ_1G)
+		ret = io_buffer_validate(&iov);
+		if (ret)
 			break;
 
 		ret = io_sqe_buffer_register(ctx, &iov, imu, &last_hpage);