On Thu, Oct 24, 2019 at 05:57:32PM +0100, David Howells wrote: > pipe: Add fsync() support > > The keyrings testsuite needs the ability to wait for all the outstanding > notifications in the queue to have been processed so that it can then go > through them to find out whether the notifications it expected have been > emitted. > > Implement fsync() support for pipes to provide this. The tailmost buffer > at the point of calling is marked and fsync adds itself to the list of > waiters, noting the tail position to be waited for and marking the buffer > as no longer mergeable. Then when the buffer is consumed, if the flag is > set, any matching waiters are woken up. I am _really_ worried about overloading fsync for this behavior. fsync hasn't done anything for 50 years, and suddenly adding any action is not helpful. If you can't use FIONREAD please add a new ioctls instead, and document it properly.
