linux-kernel - Re: [PATCH v4] eventfd: convert to f_op->read

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Message-ID: <20200504123913.GA14334@infradead.org>
Date:   Mon, 4 May 2020 05:39:13 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] eventfd: convert to f_op->read_iter()

On Fri, May 01, 2020 at 01:11:09PM -0600, Jens Axboe wrote:
> eventfd is using ->read() as it's file_operations read handler, but
> this prevents passing in information about whether a given IO operation
> is blocking or not. We can only use the file flags for that. To support
> async (-EAGAIN/poll based) retries for io_uring, we need ->read_iter()
> support. Convert eventfd to using ->read_iter().
> 
> With ->read_iter(), we can support IOCB_NOWAIT. Ensure the fd setup
> is done such that we set file->f_mode with FMODE_NOWAIT.

Can you add a anon_inode_getfd_mode that passes extra flags for f_mode
instead of opencoding it?  Especially as I expect more users that might
want to handle IOCB_NOWAIT.