Hi Jens, > 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. I like that approach, however I'm wondering if this able to be used by libraries as it requires coordination of fd values within the whole process. I don't think this would be a reason to block that feature, but it might be good to be added to the manpages. As future addition I'd like to get support for something similar but for io_uring fixed file slots. That could also be used by libraries using a private ring fd. metze
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