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Re: Perform mmap and poll on PUD character devices

> I do not understahd why it is desirable to involve additional context
> switches to and from userspace into this data path.

> Instead of writing a bunch of fairly dubious page mapping code [...]
> in the kernel to support user-space daemons handling various virtual
> disk formats, why not put the effort into just doing the various
> desired virtual disk formats in-kernel?

I can't speak for Roger, but it seems to me that an appropriate answer
would be "the same reasons you do _anything_ in userspace rather than
the kernel": better insulation of pieces of the system from one
another and ease of changing if you want to run something else instead
strike me as the biggest ones.

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