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.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/uapi/linux/io_uring.h | 2 ++
io_uring/opdef.c | 9 +++++++++
io_uring/openclose.c | 37 +++++++++++++++++++++++++++++++++++
io_uring/openclose.h | 3 +++
4 files changed, 51 insertions(+)
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index f1c16f817742..af82aab9e632 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,
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 799db44283c7..6705634e5f52 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -469,6 +469,12 @@ const struct io_issue_def io_issue_defs[] = {
.prep = io_eopnotsupp_prep,
#endif
},
+ [IORING_OP_FIXED_FD_INSTALL] = {
+ .needs_file = 1,
+ .audit_skip = 1,
+ .prep = io_install_fixed_fd_prep,
+ .issue = io_install_fixed_fd,
+ },
};
const struct io_cold_def io_cold_defs[] = {
@@ -704,6 +710,9 @@ const struct io_cold_def io_cold_defs[] = {
[IORING_OP_FUTEX_WAITV] = {
.name = "FUTEX_WAITV",
},
+ [IORING_OP_FIXED_FD_INSTALL] = {
+ .name = "FIXED_FD_INSTALL",
+ },
};
const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/openclose.c b/io_uring/openclose.c
index fb73adb89067..5b8f79edef26 100644
--- a/io_uring/openclose.c
+++ b/io_uring/openclose.c
@@ -31,6 +31,11 @@ struct io_close {
u32 file_slot;
};
+struct io_fixed_install {
+ struct file *file;
+ int flags;
+};
+
static bool io_openat_force_async(struct io_open *open)
{
/*
@@ -254,3 +259,35 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
io_req_set_res(req, ret, 0);
return IOU_OK;
}
+
+int io_install_fixed_fd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+ struct io_fixed_install *ifi;
+
+ if (sqe->off || sqe->addr || sqe->len || sqe->buf_index ||
+ sqe->splice_fd_in || sqe->addr3)
+ return -EINVAL;
+
+ /* must be a fixed file */
+ if (!(req->flags & REQ_F_FIXED_FILE))
+ return -EBADF;
+
+ ifi = io_kiocb_to_cmd(req, struct io_fixed_install);
+
+ /* really just O_CLOEXEC or not */
+ ifi->flags = READ_ONCE(sqe->install_fd_flags);
+ return 0;
+}
+
+int io_install_fixed_fd(struct io_kiocb *req, unsigned int issue_flags)
+{
+ struct io_fixed_install *ifi;
+ int ret;
+
+ ifi = io_kiocb_to_cmd(req, struct io_fixed_install);
+ ret = receive_fd(req->file, ifi->flags);
+ if (ret < 0)
+ req_set_fail(req);
+ io_req_set_res(req, ret, 0);
+ return IOU_OK;
+}
diff --git a/io_uring/openclose.h b/io_uring/openclose.h
index 4b1c28d3a66c..8a93c98ad0ad 100644
--- a/io_uring/openclose.h
+++ b/io_uring/openclose.h
@@ -12,3 +12,6 @@ int io_openat2(struct io_kiocb *req, unsigned int issue_flags);
int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
int io_close(struct io_kiocb *req, unsigned int issue_flags);
+
+int io_install_fixed_fd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_install_fixed_fd(struct io_kiocb *req, unsigned int issue_flags);
--
2.42.0
--
Jens Axboe
