fs: hlist UP debug fixup (2c675598) · Commits · 戴 / test

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>

include/linux/list_bl.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -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 @@ static inline void hlist_bl_set_first(struct hlist_bl_head *h,
		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);
		}

include/linux/rculist_bl.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -11,7 +11,8 @@ static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
		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));
		}

Admin message