[RFC 05/10] io_uring/rsrc: introduce buf registration structure

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

In preparation to following changes, instead of passing an iovec for
buffer registration introduce a new structure. It'll be moved to uapi
later, but for now it's initialised early from a user provided iovec.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/rsrc.c | 47 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 15 deletions(-)

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 8d0f2ee24e0c..8af371ba6c06 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -27,8 +27,13 @@ struct io_rsrc_update {
 	u32				offset;
 };
 
+struct io_uring_regbuf_desc {
+	__u64 uaddr;
+	__u64 size;
+};
+
 static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
-						   struct iovec *iov);
+						   struct io_uring_regbuf_desc *desc);
 
 static int hpage_acct_ref(struct io_ring_ctx *ctx, struct page *hpage,
 			  bool *acct_new)
@@ -81,6 +86,15 @@ static bool hpage_acct_unref(struct io_ring_ctx *ctx, struct page *hpage)
 
 #define IO_CACHED_BVECS_SEGS	32
 
+static void io_iov_to_regbuf_desc(const struct iovec *iov,
+				  struct io_uring_regbuf_desc *desc)
+{
+	*desc = (struct io_uring_regbuf_desc) {
+		.uaddr = (u64)(uintptr_t)iov->iov_base,
+		.size = iov->iov_len,
+	};
+}
+
 int __io_account_mem(struct user_struct *user, unsigned long nr_pages)
 {
 	unsigned long page_limit, cur_pages, new_pages;
@@ -381,6 +395,7 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
 		return -EINVAL;
 
 	for (done = 0; done < nr_args; done++) {
+		struct io_uring_regbuf_desc desc;
 		struct io_rsrc_node *node;
 		u64 tag = 0;
 
@@ -394,7 +409,9 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
 			err = -EFAULT;
 			break;
 		}
-		node = io_sqe_buffer_register(ctx, iov);
+
+		io_iov_to_regbuf_desc(iov, &desc);
+		node = io_sqe_buffer_register(ctx, &desc);
 		if (IS_ERR(node)) {
 			err = PTR_ERR(node);
 			break;
@@ -853,26 +870,26 @@ bool io_check_coalesce_buffer(struct page **page_array, int nr_pages,
 }
 
 static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
-						   struct iovec *iov)
+						   struct io_uring_regbuf_desc *desc)
 {
+	unsigned long uaddr = (unsigned long)desc->uaddr;
+	size_t size = desc->size;
 	struct io_mapped_ubuf *imu = NULL;
 	struct page **pages = NULL;
 	struct io_rsrc_node *node;
 	unsigned long off;
-	size_t size;
 	int ret, nr_pages, i;
 	struct io_imu_folio_data data;
 	bool coalesced = false;
 
-	if (!iov->iov_base) {
-		if (iov->iov_len)
+	if (!uaddr) {
+		if (size)
 			return ERR_PTR(-EFAULT);
 		/* remove the buffer without installing a new one */
 		return NULL;
 	}
 
-	ret = io_validate_user_buf_range((unsigned long)iov->iov_base,
-					 iov->iov_len);
+	ret = io_validate_user_buf_range(uaddr, size);
 	if (ret)
 		return ERR_PTR(ret);
 
@@ -881,8 +898,7 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
 		return ERR_PTR(-ENOMEM);
 
 	ret = -ENOMEM;
-	pages = io_pin_pages((unsigned long) iov->iov_base, iov->iov_len,
-				&nr_pages);
+	pages = io_pin_pages(uaddr, size, &nr_pages);
 	if (IS_ERR(pages)) {
 		ret = PTR_ERR(pages);
 		pages = NULL;
@@ -904,10 +920,9 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
 	if (ret)
 		goto done;
 
-	size = iov->iov_len;
 	/* store original address for later verification */
-	imu->ubuf = (unsigned long) iov->iov_base;
-	imu->len = iov->iov_len;
+	imu->ubuf = uaddr;
+	imu->len = size;
 	imu->folio_shift = PAGE_SHIFT;
 	imu->release = io_release_ubuf;
 	imu->priv = imu;
@@ -917,7 +932,7 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
 		imu->folio_shift = data.folio_shift;
 	refcount_set(&imu->refs, 1);
 
-	off = (unsigned long)iov->iov_base & ~PAGE_MASK;
+	off = uaddr & ~PAGE_MASK;
 	if (coalesced)
 		off += data.first_folio_page_idx << PAGE_SHIFT;
 
@@ -969,6 +984,7 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 		memset(iov, 0, sizeof(*iov));
 
 	for (i = 0; i < nr_args; i++) {
+		struct io_uring_regbuf_desc desc;
 		struct io_rsrc_node *node;
 		u64 tag = 0;
 
@@ -992,7 +1008,8 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 			}
 		}
 
-		node = io_sqe_buffer_register(ctx, iov);
+		io_iov_to_regbuf_desc(iov, &desc);
+		node = io_sqe_buffer_register(ctx, &desc);
 		if (IS_ERR(node)) {
 			ret = PTR_ERR(node);
 			break;
-- 
2.54.0