XArray: Add wrappers for nested spinlocks

Some users need to take an xarray lock while holding another xarray lock.
Reported-by: Doug Gilbert <dgilbert@interlog.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

include/linux/xarray.h

@@ -508,6 +508,14 @@ static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
 				spin_lock_irqsave(&(xa)->xa_lock, flags)
 #define xa_unlock_irqrestore(xa, flags) \
 				spin_unlock_irqrestore(&(xa)->xa_lock, flags)
+#define xa_lock_nested(xa, subclass) \
+				spin_lock_nested(&(xa)->xa_lock, subclass)
+#define xa_lock_bh_nested(xa, subclass) \
+				spin_lock_bh_nested(&(xa)->xa_lock, subclass)
+#define xa_lock_irq_nested(xa, subclass) \
+				spin_lock_irq_nested(&(xa)->xa_lock, subclass)
+#define xa_lock_irqsave_nested(xa, flags, subclass) \
+		spin_lock_irqsave_nested(&(xa)->xa_lock, flags, subclass)
 
 /*
  * Versions of the normal API which require the caller to hold the