[PATCH 4/4] io_uring/rw: pre-mapped rw attributes

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

Instead of copy_from_user()'ing request attributes, allow it to be
grabbwd from a registered pre-registered parameter region like we do
with registered wait arguments.

Suggested-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 include/uapi/linux/io_uring.h |  4 +++-
 io_uring/rw.c                 | 19 ++++++++++++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 38f0d6b10eaf..ec6e6fd37d1c 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -112,7 +112,9 @@ struct io_uring_sqe {
 };
 
 /* sqe->attr_type_mask flags */
-#define IORING_RW_ATTR_FLAG_PI	(1U << 0)
+#define IORING_RW_ATTR_FLAG_PI		(1UL << 0)
+#define IORING_RW_ATTR_REGISTERED	(1UL << 63)
+
 /* PI attribute information */
 struct io_uring_attr_pi {
 		__u16	flags;
diff --git a/io_uring/rw.c b/io_uring/rw.c
index dc1acaf95db1..b1db4595788b 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -271,10 +271,17 @@ static int io_prep_rw_pi(struct io_kiocb *req, struct io_rw *rw, int ddir,
 	size_t pi_len;
 	int ret;
 
-	if (copy_from_user(&__pi_attr, u64_to_user_ptr(attr_ptr),
-	    sizeof(pi_attr)))
-		return -EFAULT;
-	pi_attr = &__pi_attr;
+	if (attr_type_mask & IORING_RW_ATTR_REGISTERED) {
+		pi_attr = io_args_get_ptr(&req->ctx->sqe_args, attr_ptr,
+					  sizeof(pi_attr));
+		if (IS_ERR(pi_attr))
+			return PTR_ERR(pi_attr);
+	} else {
+		if (copy_from_user(&__pi_attr, u64_to_user_ptr(attr_ptr),
+		    sizeof(pi_attr)))
+			return -EFAULT;
+		pi_attr = &__pi_attr;
+	}
 
 	if (pi_attr->rsvd)
 		return -EINVAL;
@@ -294,6 +301,8 @@ static int io_prep_rw_pi(struct io_kiocb *req, struct io_rw *rw, int ddir,
 	return ret;
 }
 
+#define IO_RW_ATTR_ALLOWED_MASK (IORING_RW_ATTR_FLAG_PI | IORING_RW_ATTR_REGISTERED)
+
 static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		      int ddir, bool do_import)
 {
@@ -332,7 +341,7 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 		u64 attr_ptr;
 
 		/* only PI attribute is supported currently */
-		if (attr_type_mask != IORING_RW_ATTR_FLAG_PI)
+		if (attr_type_mask & IO_RW_ATTR_ALLOWED_MASK)
 			return -EINVAL;
 
 		attr_ptr = READ_ONCE(sqe->attr_ptr);
-- 
2.47.1