PCI: iova: lockdep false alarm fix

lockdep goes off on the iova copy_reserved_iova() because it and a function
it calls grabs locks in the from, and the to of the copy operation.

The function grab locks of the same lock classes triggering the warning.  The
first lock grabbed is for the constant reserved areas that is never accessed
after early boot.  Technically you could do without grabbing the locks for the
"from" structure its copying reserved areas from.

But dropping the from locks to me looks wrong, even though it would be ok.

The affected code only runs in early boot as its setting up the DMAR
engines.

This patch gives the reserved_ioval_list locks special lockdep classes.

Signed-off-by: Mark Gross <mgross@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pci/intel-iommu.c

@@ -1097,6 +1097,8 @@ static void iommu_free_domain(struct dmar_domain *domain)
 }
 
 static struct iova_domain reserved_iova_list;
+static struct lock_class_key reserved_alloc_key;
+static struct lock_class_key reserved_rbtree_key;
 
 static void dmar_init_reserved_ranges(void)
 {
@@ -1107,6 +1109,11 @@ static void dmar_init_reserved_ranges(void)
 
 	init_iova_domain(&reserved_iova_list, DMA_32BIT_PFN);
 
+	lockdep_set_class(&reserved_iova_list.iova_alloc_lock,
+		&reserved_alloc_key);
+	lockdep_set_class(&reserved_iova_list.iova_rbtree_lock,
+		&reserved_rbtree_key);
+
 	/* IOAPIC ranges shouldn't be accessed by DMA */
 	iova = reserve_iova(&reserved_iova_list, IOVA_PFN(IOAPIC_RANGE_START),
 		IOVA_PFN(IOAPIC_RANGE_END));