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Date: Wed, 21 Jun 2006 20:56:19 -0700
From: Andrew Morton <akpm@osdl.org>
To: Alasdair G Kergon <agk@redhat.com>
Cc: linux-kernel@vger.kernel.org, mbroz@redhat.com
Subject: Re: [PATCH 02/15] dm linear: support ioctls
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On Wed, 21 Jun 2006 20:33:08 +0100
Alasdair G Kergon <agk@redhat.com> wrote:

> From: Milan Broz <mbroz@redhat.com>
> 
> When an ioctl is performed on a device with a linear target, simply
> pass it on to the underlying block device.
> 
> Note that the ioctl will pass through the filtering in blkdev_ioctl()
> twice.
>  
> Signed-off-by: Milan Broz <mbroz@redhat.com>
> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
> 
> Index: linux-2.6.17/drivers/md/dm-linear.c
> ===================================================================
> --- linux-2.6.17.orig/drivers/md/dm-linear.c	2006-06-21 17:45:16.000000000 +0100
> +++ linux-2.6.17/drivers/md/dm-linear.c	2006-06-21 18:32:07.000000000 +0100
> @@ -96,14 +96,25 @@ static int linear_status(struct dm_targe
>  	return 0;
>  }
>  
> +static int linear_ioctl(struct dm_target *ti, struct inode *inode,
> +			struct file *filp, unsigned int cmd,
> +			unsigned long arg)
> +{
> +	struct linear_c *lc = (struct linear_c *) ti->private;
> +	struct block_device *bdev = lc->dev->bdev;
> +
> +	return blkdev_ioctl(bdev->bd_inode, filp, cmd, arg);
> +}

but, but..  the blockdev's driver may have decided to use a different ioctl
handler.

We should go through file_operations.ioctl/unlocked_ioctl.