On 3/4/20 12:56 PM, Josh Triplett wrote: > 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. Let me add patch 1 to the top of the stack, for the pipe part that probably should be taken in separately. But not a huge deal to me, as long as we can get it reviewed. I'll post the series broader soon. > Do you plan to submit this during the next merge window? Maybe? In terms of timing, I think we're well within the opportunity to do so, at least. -- Jens Axboe
