From dc18b89ab113e9c6c7a529316ddf7029fb55132d Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 7 Dec 2023 20:06:02 -0700 Subject: io_uring/openclose: add support for IORING_OP_FIXED_FD_INSTALL io_uring can currently open/close regular files or fixed/direct descriptors. Or you can instantiate a fixed descriptor from a regular one, and then close the regular descriptor. But you currently can't turn a purely fixed/direct descriptor into a regular file descriptor. IORING_OP_FIXED_FD_INSTALL adds support for installing a direct descriptor into the normal file table, just like receiving a file descriptor or opening a new file would do. This is all nicely abstracted into receive_fd(), and hence adding support for this is truly trivial. Since direct descriptors are only usable within io_uring itself, it can be useful to turn them into real file descriptors if they ever need to be accessed via normal syscalls. This can either be a transitory thing, or just a permanent transition for a given direct descriptor. By default, new fds are installed with O_CLOEXEC set. The application can disable O_CLOEXEC by setting IORING_FIXED_FD_NO_CLOEXEC in the sqe->install_fd_flags member. Suggested-by: Christian Brauner Reviewed-by: Christian Brauner Signed-off-by: Jens Axboe --- include/uapi/linux/io_uring.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/uapi/linux/io_uring.h') diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index f1c16f817742..db4b913e6b39 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -71,6 +71,7 @@ struct io_uring_sqe { __u32 uring_cmd_flags; __u32 waitid_flags; __u32 futex_flags; + __u32 install_fd_flags; }; __u64 user_data; /* data to be passed back at completion time */ /* pack this to avoid bogus arm OABI complaints */ @@ -253,6 +254,7 @@ enum io_uring_op { IORING_OP_FUTEX_WAIT, IORING_OP_FUTEX_WAKE, IORING_OP_FUTEX_WAITV, + IORING_OP_FIXED_FD_INSTALL, /* this goes last, obviously */ IORING_OP_LAST, @@ -386,6 +388,13 @@ enum { /* Pass through the flags from sqe->file_index to cqe->flags */ #define IORING_MSG_RING_FLAGS_PASS (1U << 1) +/* + * IORING_OP_FIXED_FD_INSTALL flags (sqe->install_fd_flags) + * + * IORING_FIXED_FD_NO_CLOEXEC Don't mark the fd as O_CLOEXEC + */ +#define IORING_FIXED_FD_NO_CLOEXEC (1U << 0) + /* * IO completion data structure (Completion Queue Entry) */ -- cgit v1.2.3