linux-kernel - Re: [PATCH] loop: Add LOOP_SET_FD_WITH

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Message-ID: <20200331074828.GA24372@lst.de>
Date:   Tue, 31 Mar 2020 09:48:28 +0200
From:   Christoph Hellwig <hch@....de>
To:     Martijn Coenen <maco@...roid.com>
Cc:     Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@....de>,
        Bart Van Assche <bvanassche@....org>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        linux-block <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@...roid.com
Subject: Re: [PATCH] loop: Add LOOP_SET_FD_WITH_OFFSET ioctl.

On Mon, Mar 30, 2020 at 10:06:41AM +0200, Martijn Coenen wrote:
> Hi Ming,
> 
> On Mon, Mar 30, 2020 at 3:00 AM Ming Lei <ming.lei@...hat.com> wrote:
> > The new ioctl LOOP_SET_FD_WITH_OFFSET looks not generic enough, could
> > you consider to add one ioctl LOOP_SET_FD_AND_STATUS to cover both
> > SET_FD and SET_STATUS so that using two ioctl() to setup loop can become
> > deprecated finally?
> 
> I originally started out doing that. However, it is a significantly
> larger refactoring of the loop driver, and it makes things like error
> handling more complex. I thought configuring loop with an offset is
> the most common case. But if there's a preference to do an ioctl that
> takes the full status, I can work on that.

I think the full blown set fd an status would seem a lot more useful,
or even better a LOOP_CTL_ADD variant that sets up everything important
on the character device so that we avoid the half set up block devices
entirely.