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From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>, Avi Kivity <avi@scylladb.com>,
	linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] aio: implement IOCB_CMD_POLL
Date: Thu, 2 Aug 2018 11:00:52 +0200	[thread overview]
Message-ID: <20180802090052.GB13473@lst.de> (raw)
In-Reply-To: <20180801235412.GT30522@ZenIV.linux.org.uk>

On Thu, Aug 02, 2018 at 12:54:12AM +0100, Al Viro wrote:
> On Mon, Jul 30, 2018 at 09:15:43AM +0200, Christoph Hellwig wrote:
> 
> > +	apt.error = -EINVAL; /* same as no support for IOCB_CMD_POLL */
> 
> > +	mask = vfs_poll(req->file, &apt.pt) & req->events;
> > +	if (mask || apt.error) {
> > +		bool removed = false;
> > +
> > +		/* we did not manage to set up a waitqueue, done */
> > +		if (unlikely(!req->head))
> > +			goto out_fput;
> 
> > +out_fput:
> > +	fput(req->file);
> > +	return apt.error;
> 
> Ugh...  So anything that simply returns a constant value, without
> even bothering to do poll_wait() (on the theory that no matter how
> much you wait, nothing will change) is going to git -EINVAL?
> What am I missing here?

I can change it to return that constant value, but is it really going
to be useful to keep resubmitting an iocb for something that we can't
actually poll?  I don't think we help the application with that at all.

  reply	other threads:[~2018-08-02 10:46 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-30  7:15 aio poll and a new in-kernel poll API V21 (aka 2.0) Christoph Hellwig
2018-07-30  7:15 ` [PATCH 1/4] timerfd: add support for keyed wakeups Christoph Hellwig
2018-07-30  7:15 ` [PATCH 2/4] aio: add a iocb refcount Christoph Hellwig
2018-08-01 23:19   ` Al Viro
2018-08-02  8:59     ` Christoph Hellwig
2018-07-30  7:15 ` [PATCH 3/4] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-08-01 23:54   ` Al Viro
2018-08-02  9:00     ` Christoph Hellwig [this message]
2018-08-02  0:21   ` Al Viro
2018-08-02  9:22     ` Christoph Hellwig
2018-08-02 16:00       ` Al Viro
2018-08-02 16:08         ` Christoph Hellwig
2018-08-02 16:08           ` Al Viro
2018-08-02 16:16             ` Christoph Hellwig
2018-08-02 21:48               ` Al Viro
2018-07-30  7:15 ` [PATCH 4/4] aio: allow direct aio poll comletions for keyed wakeups Christoph Hellwig
  -- strict thread matches above, loose matches on Subject: below --
2018-08-06  8:30 aio poll V22 (aka 2.0) Christoph Hellwig
2018-08-06  8:30 ` [PATCH 3/4] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-07-26  8:28 aio poll and a new in-kernel poll API V20 (aka 2.0) Christoph Hellwig
2018-07-26  8:29 ` [PATCH 3/4] aio: implement IOCB_CMD_POLL Christoph Hellwig

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