linux-kernel - Re: aio poll and a new in-kernel poll API V12

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Message-ID: <20180522220748.GF30522@ZenIV.linux.org.uk>
Date:   Tue, 22 May 2018 23:07:48 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Avi Kivity <avi@...lladb.com>, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: aio poll and a new in-kernel poll API V12

On Tue, May 22, 2018 at 01:30:37PM +0200, Christoph Hellwig wrote:
> Hi all,
> 
> this series adds support for the IOCB_CMD_POLL operation to poll for the
> readyness of file descriptors using the aio subsystem.  The API is based
> on patches that existed in RHAS2.1 and RHEL3, which means it already is
> supported by libaio.  To implement the poll support efficiently new
> methods to poll are introduced in struct file_operations:  get_poll_head
> and poll_mask.  The first one returns a wait_queue_head to wait on
> (lifetime is bound by the file), and the second does a non-blocking
> check for the POLL* events.  This allows aio poll to work without
> any additional context switches, unlike epoll.

I can live with that, modulo bug in #8 (see reply to that one).  There's
some nitpicking, but that can be dealt with in followups.