[PATCH 6/6] io_uring: allow specific fd for IORING_OP_ACCEPT

[Jens Axboe <axboe@xxxxxxxxx>]

sqe->len can be set to a specific fd we want to use for accept4(), so
it uses that one instead of just assigning a free unused one.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 fs/io_uring.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a1fc0d2acf91..11bd143847ad 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -354,6 +354,7 @@ struct io_accept {
 	struct sockaddr __user		*addr;
 	int __user			*addr_len;
 	int				flags;
+	int				open_fd;
 };
 
 struct io_sync {
@@ -3943,12 +3944,15 @@ static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL|IORING_SETUP_SQPOLL)))
 		return -EINVAL;
-	if (sqe->ioprio || sqe->len || sqe->buf_index)
+	if (sqe->ioprio || sqe->buf_index)
 		return -EINVAL;
 
 	accept->addr = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	accept->addr_len = u64_to_user_ptr(READ_ONCE(sqe->addr2));
 	accept->flags = READ_ONCE(sqe->accept_flags);
+	accept->open_fd = READ_ONCE(sqe->len);
+	if (!accept->open_fd)
+		accept->open_fd = -1;
 	return 0;
 #else
 	return -EOPNOTSUPP;
@@ -3964,7 +3968,8 @@ static int __io_accept(struct io_kiocb *req, bool force_nonblock)
 
 	file_flags = force_nonblock ? O_NONBLOCK : 0;
 	ret = __sys_accept4_file(req->file, file_flags, accept->addr,
-					accept->addr_len, accept->flags);
+					accept->addr_len, accept->flags,
+					accept->open_fd);
 	if (ret == -EAGAIN && force_nonblock)
 		return -EAGAIN;
 	if (ret == -ERESTARTSYS)
-- 
2.25.1