netdev - Re: [PATCH 6/6] fs: replace f_ops->get_poll_head with a static ->f_poll

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Message-ID: <20180629132924.GB28510@lst.de>
Date:   Fri, 29 Jun 2018 15:29:24 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>, LKP <lkp@...org>
Subject: Re: [PATCH 6/6] fs: replace f_ops->get_poll_head with a static
        ->f_poll_head pointer

On Thu, Jun 28, 2018 at 10:30:27PM +0100, Al Viro wrote:
> > Because I think that what it can do is simply to do the ->poll() calls
> > outside the iocb locks, and then just attach the poll table to the
> > kioctx afterwards.
> 
> I'd do a bit more - embed the first poll_table_entry into poll iocb itself,
> so that the instances that use only one queue wouldn't need any allocations
> at all.

No need for poll_table_entry, we just need a wait_queue_head.
poll_table_entry is an select.c internal (except for two nasty driver) -
neither epoll nor most in-kernel callers use it.