maple_tree: Protect mas_prev_nentry() from dead nodes

Don't use the pivot array before checking if the node is dead.  This is
for safe use in rcu mode.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index b254b8169694cae5a13c424cb79010403f90f29d..b846d9ccfa9bafb222adef219f8ede7e6cad0467 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4860,6 +4860,11 @@ retry:
                goto retry;
        }
 
+       if (offset == mt_pivots[mt])
+               pivot = mas->max;
+       else
+               pivot = pivots[offset];
+
        while (offset && ((!mas_slot(mas, slots, offset) && pivot >= limit) ||
               !pivot))
                pivot = pivots[--offset];