[RFC 6/6] io_uring/zcrx: add dynamic area creation

[Pavel Begunkov <asml.silence@gmail.com>]

It's not always possible for the user to predict during registration how
much memory zcrx will need to sustain the traffic. Allow to dynamically
add more areas with a new ctrl code ZCRX_CTRL_ADD_AREA.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring/zcrx.h |  7 ++++++
 io_uring/zcrx.c                    | 39 +++++++++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring/zcrx.h b/include/uapi/linux/io_uring/zcrx.h
index 5ce02c7a6096..de696eb10db4 100644
--- a/include/uapi/linux/io_uring/zcrx.h
+++ b/include/uapi/linux/io_uring/zcrx.h
@@ -88,6 +88,7 @@ struct io_uring_zcrx_ifq_reg {
 enum zcrx_ctrl_op {
 	ZCRX_CTRL_FLUSH_RQ,
 	ZCRX_CTRL_EXPORT,
+	ZCRX_CTRL_ADD_AREA,
 
 	__ZCRX_CTRL_LAST,
 };
@@ -101,6 +102,11 @@ struct zcrx_ctrl_export {
 	__u32 		__resv1[11];
 };
 
+struct zcrx_ctrl_add_area {
+	__u64		area_ptr; /* pointer to struct io_uring_zcrx_area_reg */
+	__u64		__resv[5];
+};
+
 struct zcrx_ctrl {
 	__u32	zcrx_id;
 	__u32	op; /* see enum zcrx_ctrl_op */
@@ -109,6 +115,7 @@ struct zcrx_ctrl {
 	union {
 		struct zcrx_ctrl_export		zc_export;
 		struct zcrx_ctrl_flush_rq	zc_flush;
+		struct zcrx_ctrl_add_area	zc_area;
 	};
 };
 
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 5fb81bb6f819..4bcf68b8d682 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -481,7 +481,7 @@ static int __zcrx_create_area(struct io_zcrx_ifq *ifq,
 			return -EINVAL;
 		buf_size_shift = ilog2(rx_buf_len);
 	}
-	if (WARN_ON_ONCE(ifq->niov_shift))
+	if (ifq->niov_shift && ifq->niov_shift != buf_size_shift)
 		return -EINVAL;
 	if (!ifq->dev && buf_size_shift != PAGE_SHIFT)
 		return -EOPNOTSUPP;
@@ -967,6 +967,8 @@ int io_register_zcrx(struct io_ring_ctx *ctx,
 			goto err;
 	}
 
+	WARN_ON_ONCE(!ifq->niov_shift);
+
 	reg.zcrx_id = id;
 
 	scoped_guard(mutex, &ctx->mmap_lock) {
@@ -1325,6 +1327,39 @@ static int zcrx_flush_rq(struct io_ring_ctx *ctx, struct io_zcrx_ifq *zcrx,
 	return 0;
 }
 
+static int zcrx_ctrl_add_area(struct io_ring_ctx *ctx, struct io_zcrx_ifq *ifq,
+			      struct zcrx_ctrl *ctrl)
+{
+	struct zcrx_ctrl_add_area *ctrl_add = &ctrl->zc_area;
+	struct io_uring_zcrx_area_reg __user *area_uptr;
+	struct io_uring_zcrx_area_reg area_reg;
+	struct io_zcrx_area *area;
+	int ret;
+
+	area_uptr = u64_to_user_ptr(ctrl_add->area_ptr);
+
+	if (!mem_is_zero(&ctrl_add->__resv, sizeof(ctrl_add->__resv)))
+		return -EINVAL;
+	if (copy_from_user(&area_reg, area_uptr, sizeof(area_reg)))
+		return -EFAULT;
+
+	ret = __zcrx_create_area(ifq, &area_reg, &area, 0);
+	if (ret)
+		return ret;
+
+	if (copy_to_user(area_uptr, &area_reg, sizeof(area_reg))) {
+		io_zcrx_free_area(ifq, area);
+		return -EFAULT;
+	}
+
+	ret = io_zcrx_append_area(ifq, area);
+	if (ret) {
+		io_zcrx_free_area(ifq, area);
+		return ret;
+	}
+	return 0;
+}
+
 int io_zcrx_ctrl(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
 {
 	struct zcrx_ctrl ctrl;
@@ -1348,6 +1383,8 @@ int io_zcrx_ctrl(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
 		return zcrx_flush_rq(ctx, zcrx, &ctrl);
 	case ZCRX_CTRL_EXPORT:
 		return zcrx_export(ctx, zcrx, &ctrl, arg);
+	case ZCRX_CTRL_ADD_AREA:
+		return zcrx_ctrl_add_area(ctx, zcrx, &ctrl);
 	}
 
 	return -EOPNOTSUPP;
-- 
2.53.0