[PATCH] dm: support ioctls on mapped devices: fix with fake file

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

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@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index dcfbf830964c..fb9582ae6b2d 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1273,15 +1273,22 @@ static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
         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;
@@ -1290,8 +1297,8 @@ static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
 
         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);
 }
 
 /*-----------------------------------------------------------------