1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_LIST_BL_H
3#define _LINUX_LIST_BL_H
4
5#include <linux/list.h>
6#include <linux/bit_spinlock.h>
7
8/*
9 * Special version of lists, where head of the list has a lock in the lowest
10 * bit. This is useful for scalable hash tables without increasing memory
11 * footprint overhead.
12 *
13 * For modification operations, the 0 bit of hlist_bl_head->first
14 * pointer must be set.
15 *
16 * With some small modifications, this can easily be adapted to store several
17 * arbitrary bits (not just a single lock bit), if the need arises to store
18 * some fast and compact auxiliary data.
19 */
20
21#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
22#define LIST_BL_LOCKMASK 1UL
23#else
24#define LIST_BL_LOCKMASK 0UL
25#endif
26
27#ifdef CONFIG_DEBUG_LIST
28#define LIST_BL_BUG_ON(x) BUG_ON(x)
29#else
30#define LIST_BL_BUG_ON(x)
31#endif
32
33
34struct hlist_bl_head {
35 struct hlist_bl_node *first;
36};
37
38struct hlist_bl_node {
39 struct hlist_bl_node *next, **pprev;
40};
41#define INIT_HLIST_BL_HEAD(ptr) \
42 ((ptr)->first = NULL)
43
44static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h)
45{
46 h->next = NULL;
47 h->pprev = NULL;
48}
49
50#define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member)
51
52static inline bool hlist_bl_unhashed(const struct hlist_bl_node *h)
53{
54 return !h->pprev;
55}
56
57static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h)
58{
59 return (struct hlist_bl_node *)
60 ((unsigned long)h->first & ~LIST_BL_LOCKMASK);
61}
62
63static inline void hlist_bl_set_first(struct hlist_bl_head *h,
64 struct hlist_bl_node *n)
65{
66 LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
67 LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
68 LIST_BL_LOCKMASK);
69 h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
70}
71
72static inline bool hlist_bl_empty(const struct hlist_bl_head *h)
73{
74 return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK);
75}
76
77static inline void hlist_bl_add_head(struct hlist_bl_node *n,
78 struct hlist_bl_head *h)
79{
80 struct hlist_bl_node *first = hlist_bl_first(h);
81
82 n->next = first;
83 if (first)
84 first->pprev = &n->next;
85 n->pprev = &h->first;
86 hlist_bl_set_first(h, n);
87}
88
89static inline void __hlist_bl_del(struct hlist_bl_node *n)
90{
91 struct hlist_bl_node *next = n->next;
92 struct hlist_bl_node **pprev = n->pprev;
93
94 LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
95
96 /* pprev may be `first`, so be careful not to lose the lock bit */
97 WRITE_ONCE(*pprev,
98 (struct hlist_bl_node *)
99 ((unsigned long)next |
100 ((unsigned long)*pprev & LIST_BL_LOCKMASK)));
101 if (next)
102 next->pprev = pprev;
103}
104
105static inline void hlist_bl_del(struct hlist_bl_node *n)
106{
107 __hlist_bl_del(n);
108 n->next = LIST_POISON1;
109 n->pprev = LIST_POISON2;
110}
111
112static inline void hlist_bl_del_init(struct hlist_bl_node *n)
113{
114 if (!hlist_bl_unhashed(n)) {
115 __hlist_bl_del(n);
116 INIT_HLIST_BL_NODE(n);
117 }
118}
119
120static inline void hlist_bl_lock(struct hlist_bl_head *b)
121{
122 bit_spin_lock(0, (unsigned long *)b);
123}
124
125static inline void hlist_bl_unlock(struct hlist_bl_head *b)
126{
127 __bit_spin_unlock(0, (unsigned long *)b);
128}
129
130static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
131{
132 return bit_spin_is_locked(0, (unsigned long *)b);
133}
134
135/**
136 * hlist_bl_for_each_entry - iterate over list of given type
137 * @tpos: the type * to use as a loop cursor.
138 * @pos: the &struct hlist_node to use as a loop cursor.
139 * @head: the head for your list.
140 * @member: the name of the hlist_node within the struct.
141 *
142 */
143#define hlist_bl_for_each_entry(tpos, pos, head, member) \
144 for (pos = hlist_bl_first(head); \
145 pos && \
146 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
147 pos = pos->next)
148
149/**
150 * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry
151 * @tpos: the type * to use as a loop cursor.
152 * @pos: the &struct hlist_node to use as a loop cursor.
153 * @n: another &struct hlist_node to use as temporary storage
154 * @head: the head for your list.
155 * @member: the name of the hlist_node within the struct.
156 */
157#define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member) \
158 for (pos = hlist_bl_first(head); \
159 pos && ({ n = pos->next; 1; }) && \
160 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \
161 pos = n)
162
163#endif
164