b9445598d8
Instead of opening a file into a process's file table as usual and then registering the fd within io_uring, some users may want to skip the first step and place it directly into io_uring's fixed file table. This patch adds such a capability for IORING_OP_OPENAT and IORING_OP_OPENAT2. The behaviour is controlled by setting sqe->file_index, where 0 implies the old behaviour using normal file tables. If non-zero value is specified, then it will behave as described and place the file into a fixed file slot sqe->file_index - 1. A file table should be already created, the slot should be valid and empty, otherwise the operation will fail. Keep the error codes consistent with IORING_OP_FILES_UPDATE, ENXIO and EINVAL on inappropriate fixed tables, and return EBADF on collision with already registered file. Note: IOSQE_FIXED_FILE can't be used to switch between modes, because accept takes a file, and it already uses the flag with a different meaning. Suggested-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Link: https://lore.kernel.org/r/e9b33d1163286f51ea707f87d95bd596dada1e65.1629888991.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.