dm: do not forward ioctls from logical volumes to the underlying device

A logical volume can map to just part of underlying physical volume.
In this case, it must be treated like a partition.

Based on a patch from Alasdair G Kergon.

Cc: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static int __init dm_multipath_init(void)
{
	int r;

	/* allocate a slab for the dm_ios */
	_mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
	if (!_mpio_cache)
		return -ENOMEM;

	r = dm_register_target(&multipath_target);
	if (r < 0) {
		DMERR("register failed %d", r);
		kmem_cache_destroy(_mpio_cache);
		return -EINVAL;
	}

	kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
	if (!kmultipathd) {
		DMERR("failed to create workqueue kmpathd");
		dm_unregister_target(&multipath_target);
		kmem_cache_destroy(_mpio_cache);
		return -ENOMEM;
	}

	/*
	 * A separate workqueue is used to handle the device handlers
	 * to avoid overloading existing workqueue. Overloading the
	 * old workqueue would also create a bottleneck in the
	 * path of the storage hardware device activation.
	 */
	kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
						  WQ_MEM_RECLAIM);
	if (!kmpath_handlerd) {
		DMERR("failed to create workqueue kmpath_handlerd");
		destroy_workqueue(kmultipathd);
		dm_unregister_target(&multipath_target);
		kmem_cache_destroy(_mpio_cache);
		return -ENOMEM;
	}

	DMINFO("version %u.%u.%u loaded",
	       multipath_target.version[0], multipath_target.version[1],
	       multipath_target.version[2]);

	return r;
}

static int __init dm_multipath_init(void)
{
	int r;

	/* allocate a slab for the dm_ios */
	_mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
	if (!_mpio_cache)
		return -ENOMEM;

	r = dm_register_target(&multipath_target);
	if (r < 0) {
		DMERR("register failed %d", r);
		kmem_cache_destroy(_mpio_cache);
		return -EINVAL;
	}

	kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
	if (!kmultipathd) {
		DMERR("failed to create workqueue kmpathd");
		dm_unregister_target(&multipath_target);
		kmem_cache_destroy(_mpio_cache);
		return -ENOMEM;
	}

	/*
	 * A separate workqueue is used to handle the device handlers
	 * to avoid overloading existing workqueue. Overloading the
	 * old workqueue would also create a bottleneck in the
	 * path of the storage hardware device activation.
	 */
	kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
						  WQ_MEM_RECLAIM);
	if (!kmpath_handlerd) {
		DMERR("failed to create workqueue kmpath_handlerd");
		destroy_workqueue(kmultipathd);
		dm_unregister_target(&multipath_target);
		kmem_cache_destroy(_mpio_cache);
		return -ENOMEM;
	}

	DMINFO("version %u.%u.%u loaded",
	       multipath_target.version[0], multipath_target.version[1],
	       multipath_target.version[2]);

	return r;
}
