linux-kernel - [PATCH RESEND] dm: support ioctls on mapped devices: fix with fake file

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Message-ID: <20060914205833.GH3928@agk.surrey.redhat.com>
Date:	Thu, 14 Sep 2006 21:58:34 +0100
From:	Alasdair G Kergon <agk@...hat.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	linux-kernel@...r.kernel.org, Christoph Hellwig <hch@...radead.org>
Subject: [PATCH RESEND] dm: support ioctls on mapped devices: fix with fake file

From: Milan Broz <mbroz@...hat.com>

The new ioctl code passes the wrong file pointer to the underlying device.
No file pointer is available so make a temporary fake one.


[Resending: ioctl_by_bdev() does set_fs(KERNEL_DS) so it's for ioctls
originating within the kernel and unsuitable here.  We are processing ioctls
that originated in userspace and mapping them to different devices.  Fixing
the existing callers that pass a NULL file struct and consolidating the
fake_file users are separate matters to solve in later patches.]


Signed-off-by: Milan Broz <mbroz@...hat.com>
Signed-off-by: Alasdair G Kergon <agk@...hat.com>

Index: linux-2.6.17/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.17.orig/drivers/md/dm-mpath.c	2006-06-23 19:17:27.000000000 +0100
+++ linux-2.6.17/drivers/md/dm-mpath.c	2006-06-23 19:17:40.000000000 +0100
@@ -1272,15 +1272,22 @@ static int multipath_ioctl(struct dm_tar
 	struct multipath *m = (struct multipath *) ti->private;
 	struct block_device *bdev = NULL;
 	unsigned long flags;
+	struct file fake_file = {};
+	struct dentry fake_dentry = {};
 	int r = 0;
 
+	fake_file.f_dentry = &fake_dentry;
+
 	spin_lock_irqsave(&m->lock, flags);
 
 	if (!m->current_pgpath)
 		__choose_pgpath(m);
 
-	if (m->current_pgpath)
+	if (m->current_pgpath) {
 		bdev = m->current_pgpath->path.dev->bdev;
+		fake_dentry.d_inode = bdev->bd_inode;
+		fake_file.f_mode = m->current_pgpath->path.dev->mode;
+	}
 
 	if (m->queue_io)
 		r = -EAGAIN;
@@ -1289,8 +1296,8 @@ static int multipath_ioctl(struct dm_tar
 
 	spin_unlock_irqrestore(&m->lock, flags);
 
-	return r ? : blkdev_driver_ioctl(bdev->bd_inode, filp, bdev->bd_disk,
-		     cmd, arg);
+	return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
+					 bdev->bd_disk, cmd, arg);
 }
 
 /*-----------------------------------------------------------------
Index: linux-2.6.17/drivers/md/dm-linear.c
===================================================================
--- linux-2.6.17.orig/drivers/md/dm-linear.c	2006-06-23 19:17:27.000000000 +0100
+++ linux-2.6.17/drivers/md/dm-linear.c	2006-06-23 19:17:40.000000000 +0100
@@ -104,8 +104,14 @@ static int linear_ioctl(struct dm_target
 {
 	struct linear_c *lc = (struct linear_c *) ti->private;
 	struct block_device *bdev = lc->dev->bdev;
+	struct file fake_file = {};
+	struct dentry fake_dentry = {};
 
-	return blkdev_driver_ioctl(bdev->bd_inode, filp, bdev->bd_disk, cmd, arg);
+	fake_file.f_mode = lc->dev->mode;
+	fake_file.f_dentry = &fake_dentry;
+	fake_dentry.d_inode = bdev->bd_inode;
+
+	return blkdev_driver_ioctl(bdev->bd_inode, &fake_file, bdev->bd_disk, cmd, arg);
 }
 
 static struct target_type linear_target = {

-
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