Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/swap_cgroup.h>
3#include <linux/vmalloc.h>
4#include <linux/mm.h>
5
6#include <linux/swapops.h> /* depends on mm.h include */
7
8static DEFINE_MUTEX(swap_cgroup_mutex);
9
10/* Pack two cgroup id (short) of two entries in one swap_cgroup (atomic_t) */
11#define ID_PER_SC (sizeof(struct swap_cgroup) / sizeof(unsigned short))
12#define ID_SHIFT (BITS_PER_TYPE(unsigned short))
13#define ID_MASK (BIT(ID_SHIFT) - 1)
14struct swap_cgroup {
15 atomic_t ids;
16};
17
18struct swap_cgroup_ctrl {
19 struct swap_cgroup *map;
20};
21
22static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
23
24static unsigned short __swap_cgroup_id_lookup(struct swap_cgroup *map,
25 pgoff_t offset)
26{
27 unsigned int shift = (offset % ID_PER_SC) * ID_SHIFT;
28 unsigned int old_ids = atomic_read(&map[offset / ID_PER_SC].ids);
29
30 BUILD_BUG_ON(!is_power_of_2(ID_PER_SC));
31 BUILD_BUG_ON(sizeof(struct swap_cgroup) != sizeof(atomic_t));
32
33 return (old_ids >> shift) & ID_MASK;
34}
35
36static unsigned short __swap_cgroup_id_xchg(struct swap_cgroup *map,
37 pgoff_t offset,
38 unsigned short new_id)
39{
40 unsigned short old_id;
41 struct swap_cgroup *sc = &map[offset / ID_PER_SC];
42 unsigned int shift = (offset % ID_PER_SC) * ID_SHIFT;
43 unsigned int new_ids, old_ids = atomic_read(&sc->ids);
44
45 do {
46 old_id = (old_ids >> shift) & ID_MASK;
47 new_ids = (old_ids & ~(ID_MASK << shift));
48 new_ids |= ((unsigned int)new_id) << shift;
49 } while (!atomic_try_cmpxchg(&sc->ids, &old_ids, new_ids));
50
51 return old_id;
52}
53
54/**
55 * swap_cgroup_record - record mem_cgroup for a set of swap entries.
56 * These entries must belong to one single folio, and that folio
57 * must be being charged for swap space (swap out), and these
58 * entries must not have been charged
59 *
60 * @folio: the folio that the swap entry belongs to
61 * @id: mem_cgroup ID to be recorded
62 * @ent: the first swap entry to be recorded
63 */
64void swap_cgroup_record(struct folio *folio, unsigned short id,
65 swp_entry_t ent)
66{
67 unsigned int nr_ents = folio_nr_pages(folio);
68 struct swap_cgroup *map;
69 pgoff_t offset, end;
70 unsigned short old;
71
72 offset = swp_offset(ent);
73 end = offset + nr_ents;
74 map = swap_cgroup_ctrl[swp_type(ent)].map;
75
76 do {
77 old = __swap_cgroup_id_xchg(map, offset, id);
78 VM_BUG_ON(old);
79 } while (++offset != end);
80}
81
82/**
83 * swap_cgroup_clear - clear mem_cgroup for a set of swap entries.
84 * These entries must be being uncharged from swap. They either
85 * belongs to one single folio in the swap cache (swap in for
86 * cgroup v1), or no longer have any users (slot freeing).
87 *
88 * @ent: the first swap entry to be recorded into
89 * @nr_ents: number of swap entries to be recorded
90 *
91 * Returns the existing old value.
92 */
93unsigned short swap_cgroup_clear(swp_entry_t ent, unsigned int nr_ents)
94{
95 pgoff_t offset, end;
96 struct swap_cgroup *map;
97 unsigned short old, iter = 0;
98
99 offset = swp_offset(ent);
100 end = offset + nr_ents;
101 map = swap_cgroup_ctrl[swp_type(ent)].map;
102
103 do {
104 old = __swap_cgroup_id_xchg(map, offset, 0);
105 if (!iter)
106 iter = old;
107 VM_BUG_ON(iter != old);
108 } while (++offset != end);
109
110 return old;
111}
112
113/**
114 * lookup_swap_cgroup_id - lookup mem_cgroup id tied to swap entry
115 * @ent: swap entry to be looked up.
116 *
117 * Returns ID of mem_cgroup at success. 0 at failure. (0 is invalid ID)
118 */
119unsigned short lookup_swap_cgroup_id(swp_entry_t ent)
120{
121 struct swap_cgroup_ctrl *ctrl;
122
123 if (mem_cgroup_disabled())
124 return 0;
125
126 ctrl = &swap_cgroup_ctrl[swp_type(ent)];
127 return __swap_cgroup_id_lookup(ctrl->map, swp_offset(ent));
128}
129
130int swap_cgroup_swapon(int type, unsigned long max_pages)
131{
132 struct swap_cgroup *map;
133 struct swap_cgroup_ctrl *ctrl;
134
135 if (mem_cgroup_disabled())
136 return 0;
137
138 BUILD_BUG_ON(sizeof(unsigned short) * ID_PER_SC !=
139 sizeof(struct swap_cgroup));
140 map = vzalloc(DIV_ROUND_UP(max_pages, ID_PER_SC) *
141 sizeof(struct swap_cgroup));
142 if (!map)
143 goto nomem;
144
145 ctrl = &swap_cgroup_ctrl[type];
146 mutex_lock(&swap_cgroup_mutex);
147 ctrl->map = map;
148 mutex_unlock(&swap_cgroup_mutex);
149
150 return 0;
151nomem:
152 pr_info("couldn't allocate enough memory for swap_cgroup\n");
153 pr_info("swap_cgroup can be disabled by swapaccount=0 boot option\n");
154 return -ENOMEM;
155}
156
157void swap_cgroup_swapoff(int type)
158{
159 struct swap_cgroup *map;
160 struct swap_cgroup_ctrl *ctrl;
161
162 if (mem_cgroup_disabled())
163 return;
164
165 mutex_lock(&swap_cgroup_mutex);
166 ctrl = &swap_cgroup_ctrl[type];
167 map = ctrl->map;
168 ctrl->map = NULL;
169 mutex_unlock(&swap_cgroup_mutex);
170
171 vfree(map);
172}