linux-kernel - Re: [PATCH 4.4 4.9 4.14] loop: Add LOOP_SET_DIRECT

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Date:   Wed, 23 Oct 2019 18:22:44 +0100
From:   Alessio Balsini <balsini@...roid.com>
To:     gregkh@...uxfoundation.org
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.4 4.9 4.14] loop: Add LOOP_SET_DIRECT_IO to compat ioctl

Ops, please forgive the wrong in-reply-to messge id :)

Cheers,
Alessio

On Wed, Oct 23, 2019 at 06:17:36PM +0100, Alessio Balsini wrote:
> [ Upstream commit fdbe4eeeb1aac219b14f10c0ed31ae5d1123e9b8 ]
> 
> Enabling Direct I/O with loop devices helps reducing memory usage by
> avoiding double caching.  32 bit applications running on 64 bits systems
> are currently not able to request direct I/O because is missing from the
> lo_compat_ioctl.
> 
> This patch fixes the compatibility issue mentioned above by exporting
> LOOP_SET_DIRECT_IO as additional lo_compat_ioctl() entry.
> The input argument for this ioctl is a single long converted to a 1-bit
> boolean, so compatibility is preserved.
> 
> Cc: Jens Axboe <axboe@...nel.dk>
> Signed-off-by: Alessio Balsini <balsini@...roid.com>
> Signed-off-by: Jens Axboe <axboe@...nel.dk>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/block/loop.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index da3902ac16c86..8aadd4d0c3a88 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -1557,6 +1557,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
>  		arg = (unsigned long) compat_ptr(arg);
>  	case LOOP_SET_FD:
>  	case LOOP_CHANGE_FD:
> +	case LOOP_SET_DIRECT_IO:
>  		err = lo_ioctl(bdev, mode, cmd, arg);
>  		break;
>  	default:
> -- 
> 2.23.0.866.gb869b98d4c-goog
> 
> -- 
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