On Wed, Mar 04, 2020 at 11:00:10AM -0700, Jens Axboe wrote: > One of the fabled features with chains has long been the desire to > support things like: > > <open fileX><read from fileX><close fileX> > > in a single chain. This currently doesn't work, since the read/close > depends on what file descriptor we get on open. > > The original attempt at solving this provided a means to pass > descriptors between chains in a link, this version takes a different > route. Based on Josh's support for O_SPECIFIC_FD, we can instead control > what fd value we're going to get out of open (or accept). With that in > place, we don't need to do any magic to make this work. The above chain > then becomes: > > <open fileX with fd Y><read from fd Y><close fd Y> > > which is a lot more useful, and allows any sort of weird chains without > needing to nest "last open" file descriptors. > > Updated the test program to use this approach: > > https://git.kernel.dk/cgit/liburing/plain/test/orc.c?h=fd-select > > which forces the use of fd==89 for the open, and then uses that for the > read and close. > > Outside of this adaptation, fixed a few bugs and cleaned things up. I posted one comment about an issue in patch 6. Patches 2-5 look great; for those: Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Thanks for picking this up and running with it!
