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Nick Piggin4e35e602011-01-07 17:50:03 +11001#ifndef _LINUX_LIST_BL_H
2#define _LINUX_LIST_BL_H
3
4#include <linux/list.h>
Christoph Hellwig1879fd62011-04-25 14:01:36 -04005#include <linux/bit_spinlock.h>
Nick Piggin4e35e602011-01-07 17:50:03 +11006
7/*
8 * Special version of lists, where head of the list has a lock in the lowest
9 * bit. This is useful for scalable hash tables without increasing memory
10 * footprint overhead.
11 *
12 * For modification operations, the 0 bit of hlist_bl_head->first
13 * pointer must be set.
14 *
15 * With some small modifications, this can easily be adapted to store several
16 * arbitrary bits (not just a single lock bit), if the need arises to store
17 * some fast and compact auxiliary data.
18 */
19
Russell King32385c72011-01-14 13:12:45 +000020#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
Nick Piggin4e35e602011-01-07 17:50:03 +110021#define LIST_BL_LOCKMASK 1UL
22#else
23#define LIST_BL_LOCKMASK 0UL
24#endif
25
26#ifdef CONFIG_DEBUG_LIST
27#define LIST_BL_BUG_ON(x) BUG_ON(x)
28#else
29#define LIST_BL_BUG_ON(x)
30#endif
31
32
33struct hlist_bl_head {
34 struct hlist_bl_node *first;
35};
36
37struct hlist_bl_node {
38 struct hlist_bl_node *next, **pprev;
39};
40#define INIT_HLIST_BL_HEAD(ptr) \
41 ((ptr)->first = NULL)
42
43static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h)
44{
45 h->next = NULL;
46 h->pprev = NULL;
47}
48
49#define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member)
50
51static inline int hlist_bl_unhashed(const struct hlist_bl_node *h)
52{
53 return !h->pprev;
54}
55
56static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h)
57{
58 return (struct hlist_bl_node *)
59 ((unsigned long)h->first & ~LIST_BL_LOCKMASK);
60}
61
62static inline void hlist_bl_set_first(struct hlist_bl_head *h,
63 struct hlist_bl_node *n)
64{
65 LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
Nick Piggin2c675592011-01-14 02:36:43 +000066 LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
67 LIST_BL_LOCKMASK);
Nick Piggin4e35e602011-01-07 17:50:03 +110068 h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
69}
70
71static inline int hlist_bl_empty(const struct hlist_bl_head *h)
72{
73 return !((unsigned long)h->first & ~LIST_BL_LOCKMASK);
74}
75
76static inline void hlist_bl_add_head(struct hlist_bl_node *n,
77 struct hlist_bl_head *h)
78{
79 struct hlist_bl_node *first = hlist_bl_first(h);
80
81 n->next = first;
82 if (first)
83 first->pprev = &n->next;
84 n->pprev = &h->first;
85 hlist_bl_set_first(h, n);
86}
87
88static inline void __hlist_bl_del(struct hlist_bl_node *n)
89{
90 struct hlist_bl_node *next = n->next;
91 struct hlist_bl_node **pprev = n->pprev;
92
93 LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
94
95 /* pprev may be `first`, so be careful not to lose the lock bit */
96 *pprev = (struct hlist_bl_node *)
97 ((unsigned long)next |
98 ((unsigned long)*pprev & LIST_BL_LOCKMASK));
99 if (next)
100 next->pprev = pprev;
101}
102
103static inline void hlist_bl_del(struct hlist_bl_node *n)
104{
105 __hlist_bl_del(n);
106 n->next = LIST_POISON1;
107 n->pprev = LIST_POISON2;
108}
109
110static inline void hlist_bl_del_init(struct hlist_bl_node *n)
111{
112 if (!hlist_bl_unhashed(n)) {
113 __hlist_bl_del(n);
114 INIT_HLIST_BL_NODE(n);
115 }
116}
117
Christoph Hellwig1879fd62011-04-25 14:01:36 -0400118static inline void hlist_bl_lock(struct hlist_bl_head *b)
119{
120 bit_spin_lock(0, (unsigned long *)b);
121}
122
123static inline void hlist_bl_unlock(struct hlist_bl_head *b)
124{
125 __bit_spin_unlock(0, (unsigned long *)b);
126}
127
Nick Piggin4e35e602011-01-07 17:50:03 +1100128/**
129 * hlist_bl_for_each_entry - iterate over list of given type
130 * @tpos: the type * to use as a loop cursor.
131 * @pos: the &struct hlist_node to use as a loop cursor.
132 * @head: the head for your list.
133 * @member: the name of the hlist_node within the struct.
134 *
135 */
136#define hlist_bl_for_each_entry(tpos, pos, head, member) \
137 for (pos = hlist_bl_first(head); \
138 pos && \
139 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
140 pos = pos->next)
141
142/**
143 * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry
144 * @tpos: the type * to use as a loop cursor.
145 * @pos: the &struct hlist_node to use as a loop cursor.
146 * @n: another &struct hlist_node to use as temporary storage
147 * @head: the head for your list.
148 * @member: the name of the hlist_node within the struct.
149 */
150#define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member) \
151 for (pos = hlist_bl_first(head); \
152 pos && ({ n = pos->next; 1; }) && \
153 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
154 pos = n)
155
156#endif