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Date:   Wed, 4 Mar 2020 11:03:41 -0800
From:   Josh Triplett <josh@joshtriplett.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     io-uring@vger.kernel.org, jlayton@kernel.org
Subject: Re: [PATCHSET v2 0/6] Support selectable file descriptors
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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@joshtriplett.org>

Thanks for picking this up and running with it!