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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2018 HUAWEI, Inc.
4 * https://www.huawei.com/
5 */
6#include "internal.h"
7
8struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp)
9{
10 struct page *page = *pagepool;
11
12 if (page) {
13 DBG_BUGON(page_ref_count(page) != 1);
14 *pagepool = (struct page *)page_private(page);
15 } else {
16 page = alloc_page(gfp);
17 }
18 return page;
19}
20
21void erofs_release_pages(struct page **pagepool)
22{
23 while (*pagepool) {
24 struct page *page = *pagepool;
25
26 *pagepool = (struct page *)page_private(page);
27 put_page(page);
28 }
29}
30
31#ifdef CONFIG_EROFS_FS_ZIP
32/* global shrink count (for all mounted EROFS instances) */
33static atomic_long_t erofs_global_shrink_cnt;
34
35static bool erofs_workgroup_get(struct erofs_workgroup *grp)
36{
37 if (lockref_get_not_zero(&grp->lockref))
38 return true;
39
40 spin_lock(&grp->lockref.lock);
41 if (__lockref_is_dead(&grp->lockref)) {
42 spin_unlock(&grp->lockref.lock);
43 return false;
44 }
45
46 if (!grp->lockref.count++)
47 atomic_long_dec(&erofs_global_shrink_cnt);
48 spin_unlock(&grp->lockref.lock);
49 return true;
50}
51
52struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
53 pgoff_t index)
54{
55 struct erofs_sb_info *sbi = EROFS_SB(sb);
56 struct erofs_workgroup *grp;
57
58repeat:
59 rcu_read_lock();
60 grp = xa_load(&sbi->managed_pslots, index);
61 if (grp) {
62 if (!erofs_workgroup_get(grp)) {
63 /* prefer to relax rcu read side */
64 rcu_read_unlock();
65 goto repeat;
66 }
67
68 DBG_BUGON(index != grp->index);
69 }
70 rcu_read_unlock();
71 return grp;
72}
73
74struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
75 struct erofs_workgroup *grp)
76{
77 struct erofs_sb_info *const sbi = EROFS_SB(sb);
78 struct erofs_workgroup *pre;
79
80 DBG_BUGON(grp->lockref.count < 1);
81repeat:
82 xa_lock(&sbi->managed_pslots);
83 pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
84 NULL, grp, GFP_KERNEL);
85 if (pre) {
86 if (xa_is_err(pre)) {
87 pre = ERR_PTR(xa_err(pre));
88 } else if (!erofs_workgroup_get(pre)) {
89 /* try to legitimize the current in-tree one */
90 xa_unlock(&sbi->managed_pslots);
91 cond_resched();
92 goto repeat;
93 }
94 grp = pre;
95 }
96 xa_unlock(&sbi->managed_pslots);
97 return grp;
98}
99
100static void __erofs_workgroup_free(struct erofs_workgroup *grp)
101{
102 atomic_long_dec(&erofs_global_shrink_cnt);
103 erofs_workgroup_free_rcu(grp);
104}
105
106void erofs_workgroup_put(struct erofs_workgroup *grp)
107{
108 if (lockref_put_or_lock(&grp->lockref))
109 return;
110
111 DBG_BUGON(__lockref_is_dead(&grp->lockref));
112 if (grp->lockref.count == 1)
113 atomic_long_inc(&erofs_global_shrink_cnt);
114 --grp->lockref.count;
115 spin_unlock(&grp->lockref.lock);
116}
117
118static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
119 struct erofs_workgroup *grp)
120{
121 int free = false;
122
123 spin_lock(&grp->lockref.lock);
124 if (grp->lockref.count)
125 goto out;
126
127 /*
128 * Note that all cached pages should be detached before deleted from
129 * the XArray. Otherwise some cached pages could be still attached to
130 * the orphan old workgroup when the new one is available in the tree.
131 */
132 if (erofs_try_to_free_all_cached_pages(sbi, grp))
133 goto out;
134
135 /*
136 * It's impossible to fail after the workgroup is freezed,
137 * however in order to avoid some race conditions, add a
138 * DBG_BUGON to observe this in advance.
139 */
140 DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp);
141
142 lockref_mark_dead(&grp->lockref);
143 free = true;
144out:
145 spin_unlock(&grp->lockref.lock);
146 if (free)
147 __erofs_workgroup_free(grp);
148 return free;
149}
150
151static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
152 unsigned long nr_shrink)
153{
154 struct erofs_workgroup *grp;
155 unsigned int freed = 0;
156 unsigned long index;
157
158 xa_lock(&sbi->managed_pslots);
159 xa_for_each(&sbi->managed_pslots, index, grp) {
160 /* try to shrink each valid workgroup */
161 if (!erofs_try_to_release_workgroup(sbi, grp))
162 continue;
163 xa_unlock(&sbi->managed_pslots);
164
165 ++freed;
166 if (!--nr_shrink)
167 return freed;
168 xa_lock(&sbi->managed_pslots);
169 }
170 xa_unlock(&sbi->managed_pslots);
171 return freed;
172}
173
174/* protected by 'erofs_sb_list_lock' */
175static unsigned int shrinker_run_no;
176
177/* protects the mounted 'erofs_sb_list' */
178static DEFINE_SPINLOCK(erofs_sb_list_lock);
179static LIST_HEAD(erofs_sb_list);
180
181void erofs_shrinker_register(struct super_block *sb)
182{
183 struct erofs_sb_info *sbi = EROFS_SB(sb);
184
185 mutex_init(&sbi->umount_mutex);
186
187 spin_lock(&erofs_sb_list_lock);
188 list_add(&sbi->list, &erofs_sb_list);
189 spin_unlock(&erofs_sb_list_lock);
190}
191
192void erofs_shrinker_unregister(struct super_block *sb)
193{
194 struct erofs_sb_info *const sbi = EROFS_SB(sb);
195
196 mutex_lock(&sbi->umount_mutex);
197 /* clean up all remaining workgroups in memory */
198 erofs_shrink_workstation(sbi, ~0UL);
199
200 spin_lock(&erofs_sb_list_lock);
201 list_del(&sbi->list);
202 spin_unlock(&erofs_sb_list_lock);
203 mutex_unlock(&sbi->umount_mutex);
204}
205
206static unsigned long erofs_shrink_count(struct shrinker *shrink,
207 struct shrink_control *sc)
208{
209 return atomic_long_read(&erofs_global_shrink_cnt);
210}
211
212static unsigned long erofs_shrink_scan(struct shrinker *shrink,
213 struct shrink_control *sc)
214{
215 struct erofs_sb_info *sbi;
216 struct list_head *p;
217
218 unsigned long nr = sc->nr_to_scan;
219 unsigned int run_no;
220 unsigned long freed = 0;
221
222 spin_lock(&erofs_sb_list_lock);
223 do {
224 run_no = ++shrinker_run_no;
225 } while (run_no == 0);
226
227 /* Iterate over all mounted superblocks and try to shrink them */
228 p = erofs_sb_list.next;
229 while (p != &erofs_sb_list) {
230 sbi = list_entry(p, struct erofs_sb_info, list);
231
232 /*
233 * We move the ones we do to the end of the list, so we stop
234 * when we see one we have already done.
235 */
236 if (sbi->shrinker_run_no == run_no)
237 break;
238
239 if (!mutex_trylock(&sbi->umount_mutex)) {
240 p = p->next;
241 continue;
242 }
243
244 spin_unlock(&erofs_sb_list_lock);
245 sbi->shrinker_run_no = run_no;
246
247 freed += erofs_shrink_workstation(sbi, nr - freed);
248
249 spin_lock(&erofs_sb_list_lock);
250 /* Get the next list element before we move this one */
251 p = p->next;
252
253 /*
254 * Move this one to the end of the list to provide some
255 * fairness.
256 */
257 list_move_tail(&sbi->list, &erofs_sb_list);
258 mutex_unlock(&sbi->umount_mutex);
259
260 if (freed >= nr)
261 break;
262 }
263 spin_unlock(&erofs_sb_list_lock);
264 return freed;
265}
266
267static struct shrinker *erofs_shrinker_info;
268
269int __init erofs_init_shrinker(void)
270{
271 erofs_shrinker_info = shrinker_alloc(0, "erofs-shrinker");
272 if (!erofs_shrinker_info)
273 return -ENOMEM;
274
275 erofs_shrinker_info->count_objects = erofs_shrink_count;
276 erofs_shrinker_info->scan_objects = erofs_shrink_scan;
277
278 shrinker_register(erofs_shrinker_info);
279
280 return 0;
281}
282
283void erofs_exit_shrinker(void)
284{
285 shrinker_free(erofs_shrinker_info);
286}
287#endif /* !CONFIG_EROFS_FS_ZIP */
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2018 HUAWEI, Inc.
4 * https://www.huawei.com/
5 */
6#include "internal.h"
7#include <linux/pagevec.h>
8
9struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp)
10{
11 struct page *page = *pagepool;
12
13 if (page) {
14 DBG_BUGON(page_ref_count(page) != 1);
15 *pagepool = (struct page *)page_private(page);
16 } else {
17 page = alloc_page(gfp);
18 }
19 return page;
20}
21
22void erofs_release_pages(struct page **pagepool)
23{
24 while (*pagepool) {
25 struct page *page = *pagepool;
26
27 *pagepool = (struct page *)page_private(page);
28 put_page(page);
29 }
30}
31
32#ifdef CONFIG_EROFS_FS_ZIP
33/* global shrink count (for all mounted EROFS instances) */
34static atomic_long_t erofs_global_shrink_cnt;
35
36static int erofs_workgroup_get(struct erofs_workgroup *grp)
37{
38 int o;
39
40repeat:
41 o = erofs_wait_on_workgroup_freezed(grp);
42 if (o <= 0)
43 return -1;
44
45 if (atomic_cmpxchg(&grp->refcount, o, o + 1) != o)
46 goto repeat;
47
48 /* decrease refcount paired by erofs_workgroup_put */
49 if (o == 1)
50 atomic_long_dec(&erofs_global_shrink_cnt);
51 return 0;
52}
53
54struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
55 pgoff_t index)
56{
57 struct erofs_sb_info *sbi = EROFS_SB(sb);
58 struct erofs_workgroup *grp;
59
60repeat:
61 rcu_read_lock();
62 grp = xa_load(&sbi->managed_pslots, index);
63 if (grp) {
64 if (erofs_workgroup_get(grp)) {
65 /* prefer to relax rcu read side */
66 rcu_read_unlock();
67 goto repeat;
68 }
69
70 DBG_BUGON(index != grp->index);
71 }
72 rcu_read_unlock();
73 return grp;
74}
75
76struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
77 struct erofs_workgroup *grp)
78{
79 struct erofs_sb_info *const sbi = EROFS_SB(sb);
80 struct erofs_workgroup *pre;
81
82 /*
83 * Bump up a reference count before making this visible
84 * to others for the XArray in order to avoid potential
85 * UAF without serialized by xa_lock.
86 */
87 atomic_inc(&grp->refcount);
88
89repeat:
90 xa_lock(&sbi->managed_pslots);
91 pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
92 NULL, grp, GFP_NOFS);
93 if (pre) {
94 if (xa_is_err(pre)) {
95 pre = ERR_PTR(xa_err(pre));
96 } else if (erofs_workgroup_get(pre)) {
97 /* try to legitimize the current in-tree one */
98 xa_unlock(&sbi->managed_pslots);
99 cond_resched();
100 goto repeat;
101 }
102 atomic_dec(&grp->refcount);
103 grp = pre;
104 }
105 xa_unlock(&sbi->managed_pslots);
106 return grp;
107}
108
109static void __erofs_workgroup_free(struct erofs_workgroup *grp)
110{
111 atomic_long_dec(&erofs_global_shrink_cnt);
112 erofs_workgroup_free_rcu(grp);
113}
114
115int erofs_workgroup_put(struct erofs_workgroup *grp)
116{
117 int count = atomic_dec_return(&grp->refcount);
118
119 if (count == 1)
120 atomic_long_inc(&erofs_global_shrink_cnt);
121 else if (!count)
122 __erofs_workgroup_free(grp);
123 return count;
124}
125
126static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
127 struct erofs_workgroup *grp)
128{
129 /*
130 * If managed cache is on, refcount of workgroups
131 * themselves could be < 0 (freezed). In other words,
132 * there is no guarantee that all refcounts > 0.
133 */
134 if (!erofs_workgroup_try_to_freeze(grp, 1))
135 return false;
136
137 /*
138 * Note that all cached pages should be unattached
139 * before deleted from the XArray. Otherwise some
140 * cached pages could be still attached to the orphan
141 * old workgroup when the new one is available in the tree.
142 */
143 if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
144 erofs_workgroup_unfreeze(grp, 1);
145 return false;
146 }
147
148 /*
149 * It's impossible to fail after the workgroup is freezed,
150 * however in order to avoid some race conditions, add a
151 * DBG_BUGON to observe this in advance.
152 */
153 DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp);
154
155 /* last refcount should be connected with its managed pslot. */
156 erofs_workgroup_unfreeze(grp, 0);
157 __erofs_workgroup_free(grp);
158 return true;
159}
160
161static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
162 unsigned long nr_shrink)
163{
164 struct erofs_workgroup *grp;
165 unsigned int freed = 0;
166 unsigned long index;
167
168 xa_lock(&sbi->managed_pslots);
169 xa_for_each(&sbi->managed_pslots, index, grp) {
170 /* try to shrink each valid workgroup */
171 if (!erofs_try_to_release_workgroup(sbi, grp))
172 continue;
173 xa_unlock(&sbi->managed_pslots);
174
175 ++freed;
176 if (!--nr_shrink)
177 return freed;
178 xa_lock(&sbi->managed_pslots);
179 }
180 xa_unlock(&sbi->managed_pslots);
181 return freed;
182}
183
184/* protected by 'erofs_sb_list_lock' */
185static unsigned int shrinker_run_no;
186
187/* protects the mounted 'erofs_sb_list' */
188static DEFINE_SPINLOCK(erofs_sb_list_lock);
189static LIST_HEAD(erofs_sb_list);
190
191void erofs_shrinker_register(struct super_block *sb)
192{
193 struct erofs_sb_info *sbi = EROFS_SB(sb);
194
195 mutex_init(&sbi->umount_mutex);
196
197 spin_lock(&erofs_sb_list_lock);
198 list_add(&sbi->list, &erofs_sb_list);
199 spin_unlock(&erofs_sb_list_lock);
200}
201
202void erofs_shrinker_unregister(struct super_block *sb)
203{
204 struct erofs_sb_info *const sbi = EROFS_SB(sb);
205
206 mutex_lock(&sbi->umount_mutex);
207 /* clean up all remaining workgroups in memory */
208 erofs_shrink_workstation(sbi, ~0UL);
209
210 spin_lock(&erofs_sb_list_lock);
211 list_del(&sbi->list);
212 spin_unlock(&erofs_sb_list_lock);
213 mutex_unlock(&sbi->umount_mutex);
214}
215
216static unsigned long erofs_shrink_count(struct shrinker *shrink,
217 struct shrink_control *sc)
218{
219 return atomic_long_read(&erofs_global_shrink_cnt);
220}
221
222static unsigned long erofs_shrink_scan(struct shrinker *shrink,
223 struct shrink_control *sc)
224{
225 struct erofs_sb_info *sbi;
226 struct list_head *p;
227
228 unsigned long nr = sc->nr_to_scan;
229 unsigned int run_no;
230 unsigned long freed = 0;
231
232 spin_lock(&erofs_sb_list_lock);
233 do {
234 run_no = ++shrinker_run_no;
235 } while (run_no == 0);
236
237 /* Iterate over all mounted superblocks and try to shrink them */
238 p = erofs_sb_list.next;
239 while (p != &erofs_sb_list) {
240 sbi = list_entry(p, struct erofs_sb_info, list);
241
242 /*
243 * We move the ones we do to the end of the list, so we stop
244 * when we see one we have already done.
245 */
246 if (sbi->shrinker_run_no == run_no)
247 break;
248
249 if (!mutex_trylock(&sbi->umount_mutex)) {
250 p = p->next;
251 continue;
252 }
253
254 spin_unlock(&erofs_sb_list_lock);
255 sbi->shrinker_run_no = run_no;
256
257 freed += erofs_shrink_workstation(sbi, nr - freed);
258
259 spin_lock(&erofs_sb_list_lock);
260 /* Get the next list element before we move this one */
261 p = p->next;
262
263 /*
264 * Move this one to the end of the list to provide some
265 * fairness.
266 */
267 list_move_tail(&sbi->list, &erofs_sb_list);
268 mutex_unlock(&sbi->umount_mutex);
269
270 if (freed >= nr)
271 break;
272 }
273 spin_unlock(&erofs_sb_list_lock);
274 return freed;
275}
276
277static struct shrinker erofs_shrinker_info = {
278 .scan_objects = erofs_shrink_scan,
279 .count_objects = erofs_shrink_count,
280 .seeks = DEFAULT_SEEKS,
281};
282
283int __init erofs_init_shrinker(void)
284{
285 return register_shrinker(&erofs_shrinker_info, "erofs-shrinker");
286}
287
288void erofs_exit_shrinker(void)
289{
290 unregister_shrinker(&erofs_shrinker_info);
291}
292#endif /* !CONFIG_EROFS_FS_ZIP */