Add an optional feature to open/accept directly into io_uring's fixed file table bypassing the normal file table. Same behaviour if as the snippet below, but in one operation: sqe = prep_[open,accept](...); cqe = submit_and_wait(sqe); // error handling io_uring_register_files_update(uring_idx, (fd = cqe->res)); // optionally close((fd = cqe->res)); The idea in pretty old, and was brough up and implemented a year ago by Josh Triplett, though haven't sought the light for some reasons. Tested on basic cases, will be sent out as liburing patches later. A copy paste from 2/2 describing user API and some notes: The behaviour is controlled by setting sqe->file_index, where 0 implies the old behaviour. 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. Note 1: we can't use IOSQE_FIXED_FILE to switch between modes, because accept takes a file, and it already uses the flag with a different meaning. Note 2: it's u16, where in theory the limit for fixed file tables might get increased in the future. If would ever happen so, we'll better workaround later, e.g. by making ioprio to represent upper bits 16 bits. The layout for open is tight already enough. since RFC: - added attribution - updated descriptions - rebased Pavel Begunkov (4): net: add accept helper not installing fd io_uring: openat directly into fixed fd table io_uring: hand code io_accept() fd installing io_uring: accept directly into fixed file table fs/io_uring.c | 114 +++++++++++++++++++++++++++++----- include/linux/socket.h | 3 + include/uapi/linux/io_uring.h | 2 + net/socket.c | 71 +++++++++++---------- 4 files changed, 139 insertions(+), 51 deletions(-) -- 2.32.0
