fs: hlist UP debug fixup
Po-Yu Chuang <ratbert.chuang@gmail.com> noticed that hlist_bl_set_first could
crash on a UP system when LIST_BL_LOCKMASK is 0, because
LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));
always evaulates to true.
Fix the expression, and also avoid a dependency between bit spinlock
implementation and list bl code (list code shouldn't know anything
except that bit 0 is set when adding and removing elements). Eventually
if a good use case comes up, we might use this list to store 1 or more
arbitrary bits of data, so it really shouldn't be tied to locking either,
but for now they are helpful for debugging.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h
index b872b49..cf1244f 100644
--- a/include/linux/rculist_bl.h
+++ b/include/linux/rculist_bl.h
@@ -11,7 +11,8 @@
struct hlist_bl_node *n)
{
LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
- LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));
+ LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
+ LIST_BL_LOCKMASK);
rcu_assign_pointer(h->first,
(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
}