[RFC 15/16] io_uring: allow creating mem region at setup

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

This patch gives users a way to create a memory region at ring setup
instead of requiring a registration call. First, it can be much more
convenient when the region is used for wait parameters and hence
requires IORING_SETUP_R_DISABLED. I'll also need it in the next patch
for placing SCQ into it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring.h |  7 ++++++-
 io_uring/io_uring.c           | 26 ++++++++++++++++++++++++++
 io_uring/io_uring.h           |  1 +
 io_uring/register.c           |  2 ++
 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 04797a9b76bc..2da052bd4138 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -599,11 +599,16 @@ struct io_uring_params {
 	__u32 sq_thread_idle;
 	__u32 features;
 	__u32 wq_fd;
-	__u32 resv[3];
+	__u32 resv;
+	__u64 params_ext; /* pointer to struct io_uring_params_ext */
 	struct io_sqring_offsets sq_off;
 	struct io_cqring_offsets cq_off;
 };
 
+struct io_uring_params_ext {
+	__u64 mem_region; /* pointer to struct io_uring_mem_region_reg */
+};
+
 /*
  * io_uring_params->features flags
  */
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index ff52d9f110ce..908c432aaaaa 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3574,8 +3574,13 @@ int io_uring_fill_params(struct io_uring_params *p)
 static int io_prepare_config(struct io_ctx_config *config)
 {
 	struct io_uring_params *p = &config->p;
+	struct io_uring_params_ext __user *ext_user;
 	int ret;
 
+	ext_user = u64_to_user_ptr(config->p.params_ext);
+	if (ext_user && copy_from_user(&config->ext, ext_user, sizeof(config->ext)))
+		return -EFAULT;
+
 	ret = io_uring_sanitise_params(p);
 	if (ret)
 		return ret;
@@ -3592,6 +3597,22 @@ static int io_prepare_config(struct io_ctx_config *config)
 	return 0;
 }
 
+static int io_ctx_init_mem_region(struct io_ring_ctx *ctx,
+				  struct io_ctx_config *config)
+{
+	struct io_uring_params_ext *e = &config->ext;
+	struct io_uring_mem_region_reg __user *mr_user;
+	struct io_uring_mem_region_reg mr;
+
+	mr_user = u64_to_user_ptr(e->mem_region);
+	if (!mr_user)
+		return 0;
+
+	if (copy_from_user(&mr, mr_user, sizeof(mr)))
+		return -EFAULT;
+	return io_create_mem_region(ctx, &mr);
+}
+
 static __cold int io_uring_create(struct io_ctx_config *config)
 {
 	struct io_uring_params *p = &config->p;
@@ -3661,10 +3682,15 @@ static __cold int io_uring_create(struct io_ctx_config *config)
 	mmgrab(current->mm);
 	ctx->mm_account = current->mm;
 
+	ret = io_ctx_init_mem_region(ctx, config);
+	if (ret)
+		goto err;
+
 	ret = io_allocate_scq_urings(ctx, config);
 	if (ret)
 		goto err;
 
+
 	ret = io_sq_offload_create(ctx, p);
 	if (ret)
 		goto err;
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 20f6ca4696c1..c883017b11d3 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -30,6 +30,7 @@ struct io_scq_dim {
 
 struct io_ctx_config {
 	struct io_uring_params p;
+	struct io_uring_params_ext ext;
 	struct io_scq_dim dims;
 	struct io_uring_params __user *uptr;
 };
diff --git a/io_uring/register.c b/io_uring/register.c
index 425529a30dd9..4affabc416aa 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -414,6 +414,8 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 		return -EFAULT;
 	if (p.flags & ~RESIZE_FLAGS)
 		return -EINVAL;
+	if (p.params_ext)
+		return -EINVAL;
 
 	/* properties that are always inherited */
 	p.flags |= (ctx->flags & COPY_FLAGS);
-- 
2.49.0