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Date: Thu, 2 Aug 2018 00:54:12 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: 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
Message-ID: <20180801235412.GT30522@ZenIV.linux.org.uk>
References: <20180730071544.23998-1-hch@lst.de>
 <20180730071544.23998-4-hch@lst.de>
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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?