Re: [PATCH 03/31] fs: introduce new ->get_poll_head and ->poll_mask methods

On Sat, Jan 06, 2018 at 07:12:42PM +0000, Al Viro wrote:

On Thu, Jan 04, 2018 at 09:00:15AM +0100, Christoph Hellwig wrote:

quoted

->get_poll_head returns the waitqueue that the poll operation is going
to sleep on.  Note that this means we can only use a single waitqueue
for the poll, unlike some current drivers that use two waitqueues for
different events.  But now that we have keyed wakeups and heavily use
those for poll there aren't that many good reason left to keep the
multiple waitqueues, and if there are any ->poll is still around, the
driver just won't support aio poll.

*UGH*

Gotta love the optimism, but have you actually done the conversion?
I'm particularly suspicious about the locking rules here...

I've done just about everything but random drivers.  Which is the ones
where people care about performance and thus aio poll.  I suspect that
we will have various odd cruft drivers that will be left alone.

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