man/io_uring_enter.2: add notes about direct open/accept
Add a few lines describing openat/openat2/accept bypassing normal file
tables and installing files right into the fixed file table.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cf33283b0f2e795ac7f9b6e2eabc70a4f71863c0.1630443189.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/man/io_uring_enter.2 b/man/io_uring_enter.2
index 9ccedef..e1ae707 100644
--- a/man/io_uring_enter.2
+++ b/man/io_uring_enter.2
@@ -511,6 +511,22 @@
.BR accept4(2)
for the general description of the related system call. Available since 5.5.
+If the
+.I file_index
+field is set to a positive number, the file won't be installed into the
+normal file table as usual but will be placed into the fixed file table at index
+.I file_index - 1.
+In this case, instead of returning a file descriptor, the result will contain
+either 0 on success or an error. If there is already a file registered at this
+index, the request will fail with
+.B -EBADF.
+Only io_uring has access to such files and no other syscall can use them. See
+.B IOSQE_FIXED_FILE
+and
+.B IORING_REGISTER_FILES.
+
+Available since 5.15.
+
.TP
.B IORING_OP_ASYNC_CANCEL
Attempt to cancel an already issued request.
@@ -634,6 +650,22 @@
.BR openat(2)
for the general description of the related system call. Available since 5.6.
+If the
+.I file_index
+field is set to a positive number, the file won't be installed into the
+normal file table as usual but will be placed into the fixed file table at index
+.I file_index - 1.
+In this case, instead of returning a file descriptor, the result will contain
+either 0 on success or an error. If there is already a file registered at this
+index, the request will fail with
+.B -EBADF.
+Only io_uring has access to such files and no other syscall can use them. See
+.B IOSQE_FIXED_FILE
+and
+.B IORING_REGISTER_FILES.
+
+Available since 5.15.
+
.TP
.B IORING_OP_OPENAT2
Issue the equivalent of a
@@ -654,6 +686,22 @@
.BR openat2(2)
for the general description of the related system call. Available since 5.6.
+If the
+.I file_index
+field is set to a positive number, the file won't be installed into the
+normal file table as usual but will be placed into the fixed file table at index
+.I file_index - 1.
+In this case, instead of returning a file descriptor, the result will contain
+either 0 on success or an error. If there is already a file registered at this
+index, the request will fail with
+.B -EBADF.
+Only io_uring has access to such files and no other syscall can use them. See
+.B IOSQE_FIXED_FILE
+and
+.B IORING_REGISTER_FILES.
+
+Available since 5.15.
+
.TP
.B IORING_OP_CLOSE
Issue the equivalent of a
