kernel/linux.git/include/uapi/linux/io_uring.h, branch v5.5.13

io_uring: enable option to only trigger eventfd for async completions

2020-02-11T12:37:28+00:00

[ Upstream commit f2842ab5b72d7ee5f7f8385c2d4f32c133f5837b ] If an application is using eventfd notifications with poll to know when new SQEs can be issued, it's expecting the following read/writes to complete inline. And with that, it knows that there are events available, and don't want spurious wakeups on the eventfd for those requests. This adds IORING_REGISTER_EVENTFD_ASYNC, which works just like IORING_REGISTER_EVENTFD, except it only triggers notifications for events that happen from async completions (IRQ, or io-wq worker completions). Any completions inline from the submission itself will not trigger notifications. Suggested-by: Mark Papadakis Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

io_uring: fix compat for IORING_REGISTER_FILES_UPDATE

2020-01-21T00:00:44+00:00

fds field of struct io_uring_files_update is problematic with regards to compat user space, as pointer size is different in 32-bit, 32-on-64-bit, and 64-bit user space. In order to avoid custom handling of compat in the syscall implementation, make fds __u64 and use u64_to_user_ptr in order to retrieve it. Also, align the field naturally and check that no garbage is passed there. Fixes: c3a31e605620c279 ("io_uring: add support for IORING_REGISTER_FILES_UPDATE") Signed-off-by: Eugene Syromiatnikov Signed-off-by: Jens Axboe

io_uring: ensure we return -EINVAL on unknown opcode

2019-12-11T23:02:32+00:00

If we submit an unknown opcode and have fd == -1, io_op_needs_file() will return true as we default to needing a file. Then when we go and assign the file, we find the 'fd' invalid and return -EBADF. We really should be returning -EINVAL for that case, as we normally do for unsupported opcodes. Change io_op_needs_file() to have the following return values: 0 - does not need a file 1 - does need a file < 0 - error value and use this to pass back the right value for this invalid case. Signed-off-by: Jens Axboe

io_uring: allow unbreakable links

2019-12-10T23:33:06+00:00

Some commands will invariably end in a failure in the sense that the completion result will be less than zero. One such example is timeouts that don't have a completion count set, they will always complete with -ETIME unless cancelled. For linked commands, we sever links and fail the rest of the chain if the result is less than zero. Since we have commands where we know that will happen, add IOSQE_IO_HARDLINK as a stronger link that doesn't sever regardless of the completion result. Note that the link will still sever if we fail submitting the parent request, hard links are only resilient in the presence of completion results for requests that did submit correctly. Cc: stable@vger.kernel.org # v5.4 Reviewed-by: Pavel Begunkov Reported-by: 李通洲 Signed-off-by: Jens Axboe

io_uring: mark us with IORING_FEAT_SUBMIT_STABLE

2019-12-03T14:04:32+00:00

If this flag is set, applications can be certain that any data for async offload has been consumed when the kernel has consumed the SQE. Signed-off-by: Jens Axboe

io_uring: add support for IORING_OP_CONNECT

2019-11-26T02:56:11+00:00

This allows an application to call connect() in an async fashion. Like other opcodes, we first try a non-blocking connect, then punt to async context if we have to. Note that we can still return -EINPROGRESS, and in that case the caller should use IORING_OP_POLL_ADD to do an async wait for completion of the connect request (just like for regular connect(2), except we can do it async here too). Signed-off-by: Jens Axboe

io_uring: add support for backlogged CQ ring

2019-11-09T18:45:29+00:00

Currently we drop completion events, if the CQ ring is full. That's fine for requests with bounded completion times, but it may make it harder or impossible to use io_uring with networked IO where request completion times are generally unbounded. Or with POLL, for example, which is also unbounded. After this patch, we never overflow the ring, we simply store requests in a backlog for later flushing. This flushing is done automatically by the kernel. To prevent the backlog from growing indefinitely, if the backlog is non-empty, we apply back pressure on IO submissions. Any attempt to submit new IO with a non-empty backlog will get an -EBUSY return from the kernel. This is a signal to the application that it has backlogged CQ events, and that it must reap those before being allowed to submit more IO. Note that if we do return -EBUSY, we will have filled whatever backlogged events into the CQ ring first, if there's room. This means the application can safely reap events WITHOUT entering the kernel and waiting for them, they are already available in the CQ ring. Signed-off-by: Jens Axboe

io_uring: add support for linked SQE timeouts

2019-11-08T02:12:40+00:00

While we have support for generic timeouts, we don't have a way to tie a timeout to a specific SQE. The generic timeouts simply trigger wakeups on the CQ ring. This adds support for IORING_OP_LINK_TIMEOUT. This command is only valid as a link to a previous command. The timeout specific can be either relative or absolute, following the same rules as IORING_OP_TIMEOUT. If the timeout triggers before the dependent command completes, it will attempt to cancel that command. Likewise, if the dependent command completes before the timeout triggers, it will cancel the timeout. Signed-off-by: Jens Axboe

io_uring: support for generic async request cancel

2019-11-01T14:35:31+00:00

This adds support for IORING_OP_ASYNC_CANCEL, which will attempt to cancel requests that have been punted to async context and are now in-flight. This works for regular read/write requests to files, as long as they haven't been started yet. For socket based IO (or things like accept4(2)), we can cancel work that is already running as well. To cancel a request, the sqe must have ->addr set to the user_data of the request it wishes to cancel. If the request is cancelled successfully, the original request is completed with -ECANCELED and the cancel request is completed with a result of 0. If the request was already running, the original may or may not complete in error. The cancel request will complete with -EALREADY for that case. And finally, if the request to cancel wasn't found, the cancel request is completed with -ENOENT. Signed-off-by: Jens Axboe

io_uring: add support for IORING_OP_ACCEPT

2019-10-29T18:43:06+00:00

This allows an application to call accept4() in an async fashion. Like other opcodes, we first try a non-blocking accept, then punt to async context if we have to. Signed-off-by: Jens Axboe