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/list_bl.h b/include/linux/list_bl.h
index 9ee97e7..b2adbb4 100644
--- a/include/linux/list_bl.h
+++ b/include/linux/list_bl.h
@@ -16,7 +16,7 @@
* some fast and compact auxiliary data.
*/
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+#if defined(CONFIG_SMP)
#define LIST_BL_LOCKMASK 1UL
#else
#define LIST_BL_LOCKMASK 0UL
@@ -62,7 +62,8 @@
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);
h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
}
