[PATCH 02/19] kernel: add bl_list

Dave Chinner
2010-10-16T08:21:18Z

From: Nick Piggin <npiggin@suse.de>

Introduce a type of hlist that can support the use of the lowest bit
in the hlist_head. This will be subsequently used to implement
per-bucket bit spinlock for inode hashes.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
include/linux/list_bl.h | 145 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/poison.h | 2 +
2 files changed, 147 insertions(+), 0 deletions(-)
create mode 100644 include/linux/list_bl.h

diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
new file mode 100644
index 0000000..0d791ff
--- /dev/null
+++ b/include/linux/list_bl.h
@@ -0,0 +1,145 @@
+#ifndef _LINUX_LIST_BL_H
+#define _LINUX_LIST_BL_H
+
+#include <linux/list.h>
+#include <linux/bit_spinlock.h>
+
+/*
+ * Special version of lists, where head of the list has a bit spinlock
+ * in the lowest bit. This is useful for scalable hash tables without
+ * increasing memory footprint overhead.
+ *
+ * For modification operations, the 0 bit of hlist_bl_head->first
+ * pointer must be set.
+ */
+
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+#define LIST_BL_LOCKMASK 1UL
+#else
+#define LIST_BL_LOCKMASK 0UL
+#endif
+
+#ifdef CONFIG_DEBUG_LIST
+#define LIST_BL_BUG_ON(x) BUG_ON(x)
+#else
+#define LIST_BL_BUG_ON(x)
+#endif
+
+
+struct hlist_bl_head {
+ struct hlist_bl_node *first;
+};
+
+struct hlist_bl_node {
+ struct hlist_bl_node *next, **pprev;
+};
+#define INIT_HLIST_BL_HEAD(ptr) \
+ ((ptr)->first = NULL)
+
+static inline void init_hlist_bl_node(struct hlist_bl_node *h)
+{
+ h->next = NULL;
+ h->pprev = NULL;
+}
+
+#define hlist_bl_entry(ptr, type, member) container_of(ptr, type, member)
+
+static inline int hlist_bl_unhashed(const struct hlist_bl_node *h)
+{
+ return !h->pprev;
+}
+
+static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h)
+{
+ return (struct hlist_bl_node *)
+ ((unsigned long)h->first & ~LIST_BL_LOCKMASK);
+}
+
+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(!bit_spin_is_locked(0, (unsigned long *)&h->first));
+ h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
+}
+
+static inline int hlist_bl_empty(const struct hlist_bl_head *h)
+{
+ return !((unsigned long)h->first & ~LIST_BL_LOCKMASK);
+}
+
+static inline void hlist_bl_add_head(struct hlist_bl_node *n,
+ struct hlist_bl_head *h)
+{
+ struct hlist_bl_node *first = hlist_bl_first(h);
+
+ n->next = first;
+ if (first)
+ first->pprev = &n->next;
+ n->pprev = &h->first;
+ hlist_bl_set_first(h, n);
+}
+
+static inline void __hlist_bl_del(struct hlist_bl_node *n)
+{
+ struct hlist_bl_node *next = n->next;
+ struct hlist_bl_node **pprev = n->pprev;
+
+ LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
+
+ /* pprev may be `first`, so be careful not to lose the lock bit */
+ *pprev = (struct hlist_bl_node *)
+ ((unsigned long)next |
+ ((unsigned long)*pprev & LIST_BL_LOCKMASK));
+ if (next)
+ next->pprev = pprev;
+}
+
+static inline void hlist_bl_del(struct hlist_bl_node *n)
+{
+ __hlist_bl_del(n);
+ n->next = BL_LIST_POISON1;
+ n->pprev = BL_LIST_POISON2;
+}
+
+static inline void hlist_bl_del_init(struct hlist_bl_node *n)
+{
+ if (!hlist_bl_unhashed(n)) {
+ __hlist_bl_del(n);
+ init_hlist_bl_node(n);
+ }
+}
+
+/**
+ * hlist_bl_for_each_entry - iterate over list of given type
+ * @tpos: the type * to use as a loop cursor.
+ * @pos: the &struct hlist_node to use as a loop cursor.
+ * @head: the head for your list.
+ * @member: the name of the hlist_node within the struct.
+ *
+ */
+#define hlist_bl_for_each_entry(tpos, pos, head, member) \
+ for (pos = hlist_bl_first(head); \
+ pos && \
+ ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
+ pos = pos->next)
+
+#endif
+
+/**
+ * hlist_bl_lock - lock a hash list
+ * @h: hash list head to lock
+ */
+static inline void hlist_bl_lock(struct hlist_bl_head *h)
+{
+ bit_spin_lock(0, (unsigned long *)h);
+}
+
+/**
+ * hlist_bl_unlock - unlock a hash list
+ * @h: hash list head to unlock
+ */
+static inline void hlist_bl_unlock(struct hlist_bl_head *h)
+{
+ __bit_spin_unlock(0, (unsigned long *)h);
+}
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 2110a81..d367d39 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -22,6 +22,8 @@
#define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
#define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)

+#define BL_LIST_POISON1 ((void *) 0x00300300 + POISON_POINTER_DELTA)
+#define BL_LIST_POISON2 ((void *) 0x00400400 + POISON_POINTER_DELTA)
/********** include/linux/timer.h **********/
/*
* Magic number "tsta" to indicate a static timer initializer
--
1.7.1