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1 | #include <linux/swap_cgroup.h> | |
2 | #include <linux/vmalloc.h> | |
3 | #include <linux/mm.h> | |
4 | ||
5 | #include <linux/swapops.h> /* depends on mm.h include */ | |
6 | ||
7 | static DEFINE_MUTEX(swap_cgroup_mutex); | |
8 | struct swap_cgroup_ctrl { | |
9 | struct page **map; | |
10 | unsigned long length; | |
11 | spinlock_t lock; | |
12 | }; | |
13 | ||
14 | static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES]; | |
15 | ||
16 | struct swap_cgroup { | |
17 | unsigned short id; | |
18 | }; | |
19 | #define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup)) | |
20 | ||
21 | /* | |
22 | * SwapCgroup implements "lookup" and "exchange" operations. | |
23 | * In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge | |
24 | * against SwapCache. At swap_free(), this is accessed directly from swap. | |
25 | * | |
26 | * This means, | |
27 | * - we have no race in "exchange" when we're accessed via SwapCache because | |
28 | * SwapCache(and its swp_entry) is under lock. | |
29 | * - When called via swap_free(), there is no user of this entry and no race. | |
30 | * Then, we don't need lock around "exchange". | |
31 | * | |
32 | * TODO: we can push these buffers out to HIGHMEM. | |
33 | */ | |
34 | ||
35 | /* | |
36 | * allocate buffer for swap_cgroup. | |
37 | */ | |
38 | static int swap_cgroup_prepare(int type) | |
39 | { | |
40 | struct page *page; | |
41 | struct swap_cgroup_ctrl *ctrl; | |
42 | unsigned long idx, max; | |
43 | ||
44 | ctrl = &swap_cgroup_ctrl[type]; | |
45 | ||
46 | for (idx = 0; idx < ctrl->length; idx++) { | |
47 | page = alloc_page(GFP_KERNEL | __GFP_ZERO); | |
48 | if (!page) | |
49 | goto not_enough_page; | |
50 | ctrl->map[idx] = page; | |
51 | ||
52 | if (!(idx % SWAP_CLUSTER_MAX)) | |
53 | cond_resched(); | |
54 | } | |
55 | return 0; | |
56 | not_enough_page: | |
57 | max = idx; | |
58 | for (idx = 0; idx < max; idx++) | |
59 | __free_page(ctrl->map[idx]); | |
60 | ||
61 | return -ENOMEM; | |
62 | } | |
63 | ||
64 | static struct swap_cgroup *__lookup_swap_cgroup(struct swap_cgroup_ctrl *ctrl, | |
65 | pgoff_t offset) | |
66 | { | |
67 | struct page *mappage; | |
68 | struct swap_cgroup *sc; | |
69 | ||
70 | mappage = ctrl->map[offset / SC_PER_PAGE]; | |
71 | sc = page_address(mappage); | |
72 | return sc + offset % SC_PER_PAGE; | |
73 | } | |
74 | ||
75 | static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t ent, | |
76 | struct swap_cgroup_ctrl **ctrlp) | |
77 | { | |
78 | pgoff_t offset = swp_offset(ent); | |
79 | struct swap_cgroup_ctrl *ctrl; | |
80 | ||
81 | ctrl = &swap_cgroup_ctrl[swp_type(ent)]; | |
82 | if (ctrlp) | |
83 | *ctrlp = ctrl; | |
84 | return __lookup_swap_cgroup(ctrl, offset); | |
85 | } | |
86 | ||
87 | /** | |
88 | * swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry. | |
89 | * @ent: swap entry to be cmpxchged | |
90 | * @old: old id | |
91 | * @new: new id | |
92 | * | |
93 | * Returns old id at success, 0 at failure. | |
94 | * (There is no mem_cgroup using 0 as its id) | |
95 | */ | |
96 | unsigned short swap_cgroup_cmpxchg(swp_entry_t ent, | |
97 | unsigned short old, unsigned short new) | |
98 | { | |
99 | struct swap_cgroup_ctrl *ctrl; | |
100 | struct swap_cgroup *sc; | |
101 | unsigned long flags; | |
102 | unsigned short retval; | |
103 | ||
104 | sc = lookup_swap_cgroup(ent, &ctrl); | |
105 | ||
106 | spin_lock_irqsave(&ctrl->lock, flags); | |
107 | retval = sc->id; | |
108 | if (retval == old) | |
109 | sc->id = new; | |
110 | else | |
111 | retval = 0; | |
112 | spin_unlock_irqrestore(&ctrl->lock, flags); | |
113 | return retval; | |
114 | } | |
115 | ||
116 | /** | |
117 | * swap_cgroup_record - record mem_cgroup for a set of swap entries | |
118 | * @ent: the first swap entry to be recorded into | |
119 | * @id: mem_cgroup to be recorded | |
120 | * @nr_ents: number of swap entries to be recorded | |
121 | * | |
122 | * Returns old value at success, 0 at failure. | |
123 | * (Of course, old value can be 0.) | |
124 | */ | |
125 | unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id, | |
126 | unsigned int nr_ents) | |
127 | { | |
128 | struct swap_cgroup_ctrl *ctrl; | |
129 | struct swap_cgroup *sc; | |
130 | unsigned short old; | |
131 | unsigned long flags; | |
132 | pgoff_t offset = swp_offset(ent); | |
133 | pgoff_t end = offset + nr_ents; | |
134 | ||
135 | sc = lookup_swap_cgroup(ent, &ctrl); | |
136 | ||
137 | spin_lock_irqsave(&ctrl->lock, flags); | |
138 | old = sc->id; | |
139 | for (;;) { | |
140 | VM_BUG_ON(sc->id != old); | |
141 | sc->id = id; | |
142 | offset++; | |
143 | if (offset == end) | |
144 | break; | |
145 | if (offset % SC_PER_PAGE) | |
146 | sc++; | |
147 | else | |
148 | sc = __lookup_swap_cgroup(ctrl, offset); | |
149 | } | |
150 | spin_unlock_irqrestore(&ctrl->lock, flags); | |
151 | ||
152 | return old; | |
153 | } | |
154 | ||
155 | /** | |
156 | * lookup_swap_cgroup_id - lookup mem_cgroup id tied to swap entry | |
157 | * @ent: swap entry to be looked up. | |
158 | * | |
159 | * Returns ID of mem_cgroup at success. 0 at failure. (0 is invalid ID) | |
160 | */ | |
161 | unsigned short lookup_swap_cgroup_id(swp_entry_t ent) | |
162 | { | |
163 | return lookup_swap_cgroup(ent, NULL)->id; | |
164 | } | |
165 | ||
166 | int swap_cgroup_swapon(int type, unsigned long max_pages) | |
167 | { | |
168 | void *array; | |
169 | unsigned long array_size; | |
170 | unsigned long length; | |
171 | struct swap_cgroup_ctrl *ctrl; | |
172 | ||
173 | if (!do_swap_account) | |
174 | return 0; | |
175 | ||
176 | length = DIV_ROUND_UP(max_pages, SC_PER_PAGE); | |
177 | array_size = length * sizeof(void *); | |
178 | ||
179 | array = vzalloc(array_size); | |
180 | if (!array) | |
181 | goto nomem; | |
182 | ||
183 | ctrl = &swap_cgroup_ctrl[type]; | |
184 | mutex_lock(&swap_cgroup_mutex); | |
185 | ctrl->length = length; | |
186 | ctrl->map = array; | |
187 | spin_lock_init(&ctrl->lock); | |
188 | if (swap_cgroup_prepare(type)) { | |
189 | /* memory shortage */ | |
190 | ctrl->map = NULL; | |
191 | ctrl->length = 0; | |
192 | mutex_unlock(&swap_cgroup_mutex); | |
193 | vfree(array); | |
194 | goto nomem; | |
195 | } | |
196 | mutex_unlock(&swap_cgroup_mutex); | |
197 | ||
198 | return 0; | |
199 | nomem: | |
200 | pr_info("couldn't allocate enough memory for swap_cgroup\n"); | |
201 | pr_info("swap_cgroup can be disabled by swapaccount=0 boot option\n"); | |
202 | return -ENOMEM; | |
203 | } | |
204 | ||
205 | void swap_cgroup_swapoff(int type) | |
206 | { | |
207 | struct page **map; | |
208 | unsigned long i, length; | |
209 | struct swap_cgroup_ctrl *ctrl; | |
210 | ||
211 | if (!do_swap_account) | |
212 | return; | |
213 | ||
214 | mutex_lock(&swap_cgroup_mutex); | |
215 | ctrl = &swap_cgroup_ctrl[type]; | |
216 | map = ctrl->map; | |
217 | length = ctrl->length; | |
218 | ctrl->map = NULL; | |
219 | ctrl->length = 0; | |
220 | mutex_unlock(&swap_cgroup_mutex); | |
221 | ||
222 | if (map) { | |
223 | for (i = 0; i < length; i++) { | |
224 | struct page *page = map[i]; | |
225 | if (page) | |
226 | __free_page(page); | |
227 | if (!(i % SWAP_CLUSTER_MAX)) | |
228 | cond_resched(); | |
229 | } | |
230 | vfree(map); | |
231 | } | |
232 | } |