On Wed, Mar 04, 2020 at 12:10:08PM -0700, Jens Axboe wrote: > On 3/4/20 12:03 PM, Josh Triplett wrote: > > 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! > > Thanks for doing the prep work! I think it turned out that much better > for it. > > Are you going to post your series for general review? I just stole > your 1 patch that was needed for me. Since your patch series depends on mine, please feel free to run with the series. Would you mind adding my patch 1 and 3 at the end of your series? You need patch 1 to make this more usable for userspace, and patch 3 would allow for an OP_PIPE which I'd love to have. Do you plan to submit this during the next merge window?
