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Date:   Wed, 7 Aug 2019 00:57:08 +0100
From:   Alessio Balsini <balsini@android.com>
To:     Joel Fernandes <joelaf@google.com>
Cc:     "open list:BLOCK LAYER" <linux-block@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>, dvander@gmail.com,
        Yifan Hong <elsk@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Cc: Android Kernel" <kernel-team@android.com>
Subject: Re: [PATCH] loop: Add LOOP_SET_DIRECT_IO in compat ioctl
Message-ID: <20190806235708.GA10161@google.com>
References: <20190806220524.251404-1-balsini@android.com>
 <CAJWu+oq9JLnbGdqy+362JZUzjv6PvuRTNwiarTQiEfizsY32hQ@mail.gmail.com>
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Hi Joel,

I was considering the rationale for this patch totally strightforward:
it enables Direct I/O ioctl to 32 bit processes running on 64 bit
systems for compatibility reasons, as for all the other lo_compat_ioctl
commands.
Also the reason why someone would decide to use Direct I/O with loop
devices is well known, that is why the feature exists :) So I thought
this was another redundant information to put in the commit message and
decided to omit it.

If you still think that I should update the commit message with this
information, I will do so.

Thanks again,
Alessio

On Tue, Aug 06, 2019 at 06:25:42PM -0400, 'Joel Fernandes' via kernel-team wrote:
> Hi Alessio,
> 
> On Tue, Aug 6, 2019 at 6:05 PM Alessio Balsini <balsini@android.com> wrote:
> >
> > Export LOOP_SET_DIRECT_IO as additional lo_compat_ioctl.
> > The input argument for this ioctl is a single long, in the end converted
> > to a 1-bit boolean. Compatibility is then preserved.
> >
> > Cc: Jens Axboe <axboe@kernel.dk>
> > Signed-off-by: Alessio Balsini <balsini@android.com>
> 
> This looks Ok to me, but I believe the commit message should also
> explain what was this patch "fixing", how was this lack of an "export"
> noticed, why does it matter, etc as well.
> 
> thanks,
> 
>  - Joel
> 
> 
> > ---
> >  drivers/block/loop.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> > index 3036883fc9f8..a7461f482467 100644
> > --- a/drivers/block/loop.c
> > +++ b/drivers/block/loop.c
> > @@ -1755,6 +1755,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
> >         case LOOP_SET_FD:
> >         case LOOP_CHANGE_FD:
> >         case LOOP_SET_BLOCK_SIZE:
> > +       case LOOP_SET_DIRECT_IO:
> >                 err = lo_ioctl(bdev, mode, cmd, arg);
> >                 break;
> >         default:
> > --
> > 2.22.0.770.g0f2c4a37fd-goog
> >
> > --
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> >
> 
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