[Jens Axboe <axboe@kernel.dk>]

Hi,

It can be useful to know if a given file/socket/pipe needed to go
through poll arming to successfully execute the request. For example, a
write to a pipe will normally succeed inline. Ditto for a send on a
socket. But if the socket or pipe is full, then io_uring must wait for a
POLLOUT trigger to execute the request. This can be useful backpressure
information for an application. On the read side, it'll tell the
application whether data was readily available or not, if POLLIN
triggering was needed to read/recv the data.

This patchset adds support for IORING_CQE_F_POLLED, which is set in
cqe->flags if a request needed to go through the poll machinery before
it could get successfully executed.

Patch 1 is just an unrelated cleanup I spotted while doing this work.
Patch 2 adds a request flag that gets set via poll wake, and patch 3
wires up using this flag to set IORING_CQE_F_POLLED.

liburing test cases here:

https://git.kernel.dk/cgit/liburing/log/?h=cqe-polled

and the patches here can also be found here:

https://git.kernel.dk/cgit/linux/log/?h=io_uring-send-full

 include/linux/io_uring_types.h |  3 +++
 include/uapi/linux/io_uring.h  |  6 ++++++
 io_uring/io_uring.c            | 14 ++++++--------
 io_uring/io_uring.h            |  2 ++
 io_uring/poll.c                |  1 +
 5 files changed, 18 insertions(+), 8 deletions(-)

-- 
Jens Axboe