linux-kernel - Re: aio poll and a new in-kernel poll API V13

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Message-ID: <20180526070937.GA4188@ZenIV.linux.org.uk>
Date:   Sat, 26 May 2018 08:09:37 +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 V13

On Sat, May 26, 2018 at 01:11:11AM +0100, Al Viro wrote:
> On Wed, May 23, 2018 at 09:19:49PM +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.
> > 
> > This series sits on top of the aio-fsync series that also includes
> > support for io_pgetevents.
> 
> OK, I can live with that, except for one problem - the first patch shouldn't
> be sitting on top of arseloads of next window fodder.
> 
> Please, rebase the rest of the series on top of merge of vfs.git#fixes
> (4faa99965e02) with your aio-fsync.4 and tell me what to pull.

UGH

You've based it on vfs.git#hch.aio (== your aio-fsync.4) + baf10564fbb6
(== vfs.git#fixes^), *and* started with cherry-pick of vfs.git#fixes
on top of that, followed by your series.

That makes no sense whatsoever.  Please, take your aio-fsync.4, merge
vfs.git#fixes (== 4faa99965e02, "fix io_destroy()/aio_complete() race",
same change as your 4e79230e5254) into it and rebase the rest of your
branch on top of that (from "uapi: turn __poll_t sparse checkin
on by default" to "random: convert to ->poll_mask").  BTW, you probably
want s/checkin/checks/ in the first one of those...