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30#include <linux/swap_slots.h>
31#include <linux/cpu.h>
32#include <linux/cpumask.h>
33#include <linux/vmalloc.h>
34#include <linux/mutex.h>
35#include <linux/mm.h>
36
37static DEFINE_PER_CPU(struct swap_slots_cache, swp_slots);
38static bool swap_slot_cache_active;
39bool swap_slot_cache_enabled;
40static bool swap_slot_cache_initialized;
41DEFINE_MUTEX(swap_slots_cache_mutex);
42
43DEFINE_MUTEX(swap_slots_cache_enable_mutex);
44
45static void __drain_swap_slots_cache(unsigned int type);
46static void deactivate_swap_slots_cache(void);
47static void reactivate_swap_slots_cache(void);
48
49#define use_swap_slot_cache (swap_slot_cache_active && \
50 swap_slot_cache_enabled && swap_slot_cache_initialized)
51#define SLOTS_CACHE 0x1
52#define SLOTS_CACHE_RET 0x2
53
54static void deactivate_swap_slots_cache(void)
55{
56 mutex_lock(&swap_slots_cache_mutex);
57 swap_slot_cache_active = false;
58 __drain_swap_slots_cache(SLOTS_CACHE|SLOTS_CACHE_RET);
59 mutex_unlock(&swap_slots_cache_mutex);
60}
61
62static void reactivate_swap_slots_cache(void)
63{
64 mutex_lock(&swap_slots_cache_mutex);
65 swap_slot_cache_active = true;
66 mutex_unlock(&swap_slots_cache_mutex);
67}
68
69
70void disable_swap_slots_cache_lock(void)
71{
72 mutex_lock(&swap_slots_cache_enable_mutex);
73 swap_slot_cache_enabled = false;
74 if (swap_slot_cache_initialized) {
75
76 get_online_cpus();
77 __drain_swap_slots_cache(SLOTS_CACHE|SLOTS_CACHE_RET);
78 put_online_cpus();
79 }
80}
81
82static void __reenable_swap_slots_cache(void)
83{
84 swap_slot_cache_enabled = has_usable_swap();
85}
86
87void reenable_swap_slots_cache_unlock(void)
88{
89 __reenable_swap_slots_cache();
90 mutex_unlock(&swap_slots_cache_enable_mutex);
91}
92
93static bool check_cache_active(void)
94{
95 long pages;
96
97 if (!swap_slot_cache_enabled || !swap_slot_cache_initialized)
98 return false;
99
100 pages = get_nr_swap_pages();
101 if (!swap_slot_cache_active) {
102 if (pages > num_online_cpus() *
103 THRESHOLD_ACTIVATE_SWAP_SLOTS_CACHE)
104 reactivate_swap_slots_cache();
105 goto out;
106 }
107
108
109 if (pages < num_online_cpus() * THRESHOLD_DEACTIVATE_SWAP_SLOTS_CACHE)
110 deactivate_swap_slots_cache();
111out:
112 return swap_slot_cache_active;
113}
114
115static int alloc_swap_slot_cache(unsigned int cpu)
116{
117 struct swap_slots_cache *cache;
118 swp_entry_t *slots, *slots_ret;
119
120
121
122
123
124
125 slots = kvzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE,
126 GFP_KERNEL);
127 if (!slots)
128 return -ENOMEM;
129
130 slots_ret = kvzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE,
131 GFP_KERNEL);
132 if (!slots_ret) {
133 kvfree(slots);
134 return -ENOMEM;
135 }
136
137 mutex_lock(&swap_slots_cache_mutex);
138 cache = &per_cpu(swp_slots, cpu);
139 if (cache->slots || cache->slots_ret)
140
141 goto out;
142 if (!cache->lock_initialized) {
143 mutex_init(&cache->alloc_lock);
144 spin_lock_init(&cache->free_lock);
145 cache->lock_initialized = true;
146 }
147 cache->nr = 0;
148 cache->cur = 0;
149 cache->n_ret = 0;
150
151
152
153
154
155
156 mb();
157 cache->slots = slots;
158 slots = NULL;
159 cache->slots_ret = slots_ret;
160 slots_ret = NULL;
161out:
162 mutex_unlock(&swap_slots_cache_mutex);
163 if (slots)
164 kvfree(slots);
165 if (slots_ret)
166 kvfree(slots_ret);
167 return 0;
168}
169
170static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
171 bool free_slots)
172{
173 struct swap_slots_cache *cache;
174 swp_entry_t *slots = NULL;
175
176 cache = &per_cpu(swp_slots, cpu);
177 if ((type & SLOTS_CACHE) && cache->slots) {
178 mutex_lock(&cache->alloc_lock);
179 swapcache_free_entries(cache->slots + cache->cur, cache->nr);
180 cache->cur = 0;
181 cache->nr = 0;
182 if (free_slots && cache->slots) {
183 kvfree(cache->slots);
184 cache->slots = NULL;
185 }
186 mutex_unlock(&cache->alloc_lock);
187 }
188 if ((type & SLOTS_CACHE_RET) && cache->slots_ret) {
189 spin_lock_irq(&cache->free_lock);
190 swapcache_free_entries(cache->slots_ret, cache->n_ret);
191 cache->n_ret = 0;
192 if (free_slots && cache->slots_ret) {
193 slots = cache->slots_ret;
194 cache->slots_ret = NULL;
195 }
196 spin_unlock_irq(&cache->free_lock);
197 if (slots)
198 kvfree(slots);
199 }
200}
201
202static void __drain_swap_slots_cache(unsigned int type)
203{
204 unsigned int cpu;
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228
229 for_each_online_cpu(cpu)
230 drain_slots_cache_cpu(cpu, type, false);
231}
232
233static int free_slot_cache(unsigned int cpu)
234{
235 mutex_lock(&swap_slots_cache_mutex);
236 drain_slots_cache_cpu(cpu, SLOTS_CACHE | SLOTS_CACHE_RET, true);
237 mutex_unlock(&swap_slots_cache_mutex);
238 return 0;
239}
240
241int enable_swap_slots_cache(void)
242{
243 int ret = 0;
244
245 mutex_lock(&swap_slots_cache_enable_mutex);
246 if (swap_slot_cache_initialized) {
247 __reenable_swap_slots_cache();
248 goto out_unlock;
249 }
250
251 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "swap_slots_cache",
252 alloc_swap_slot_cache, free_slot_cache);
253 if (WARN_ONCE(ret < 0, "Cache allocation failed (%s), operating "
254 "without swap slots cache.\n", __func__))
255 goto out_unlock;
256
257 swap_slot_cache_initialized = true;
258 __reenable_swap_slots_cache();
259out_unlock:
260 mutex_unlock(&swap_slots_cache_enable_mutex);
261 return 0;
262}
263
264
265static int refill_swap_slots_cache(struct swap_slots_cache *cache)
266{
267 if (!use_swap_slot_cache || cache->nr)
268 return 0;
269
270 cache->cur = 0;
271 if (swap_slot_cache_active)
272 cache->nr = get_swap_pages(SWAP_SLOTS_CACHE_SIZE, false,
273 cache->slots);
274
275 return cache->nr;
276}
277
278int free_swap_slot(swp_entry_t entry)
279{
280 struct swap_slots_cache *cache;
281
282 cache = raw_cpu_ptr(&swp_slots);
283 if (likely(use_swap_slot_cache && cache->slots_ret)) {
284 spin_lock_irq(&cache->free_lock);
285
286 if (!use_swap_slot_cache || !cache->slots_ret) {
287 spin_unlock_irq(&cache->free_lock);
288 goto direct_free;
289 }
290 if (cache->n_ret >= SWAP_SLOTS_CACHE_SIZE) {
291
292
293
294
295
296
297 swapcache_free_entries(cache->slots_ret, cache->n_ret);
298 cache->n_ret = 0;
299 }
300 cache->slots_ret[cache->n_ret++] = entry;
301 spin_unlock_irq(&cache->free_lock);
302 } else {
303direct_free:
304 swapcache_free_entries(&entry, 1);
305 }
306
307 return 0;
308}
309
310swp_entry_t get_swap_page(struct page *page)
311{
312 swp_entry_t entry, *pentry;
313 struct swap_slots_cache *cache;
314
315 entry.val = 0;
316
317 if (PageTransHuge(page)) {
318 if (IS_ENABLED(CONFIG_THP_SWAP))
319 get_swap_pages(1, true, &entry);
320 return entry;
321 }
322
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332 cache = raw_cpu_ptr(&swp_slots);
333
334 if (likely(check_cache_active() && cache->slots)) {
335 mutex_lock(&cache->alloc_lock);
336 if (cache->slots) {
337repeat:
338 if (cache->nr) {
339 pentry = &cache->slots[cache->cur++];
340 entry = *pentry;
341 pentry->val = 0;
342 cache->nr--;
343 } else {
344 if (refill_swap_slots_cache(cache))
345 goto repeat;
346 }
347 }
348 mutex_unlock(&cache->alloc_lock);
349 if (entry.val)
350 return entry;
351 }
352
353 get_swap_pages(1, false, &entry);
354
355 return entry;
356}
357