1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2018 HUAWEI, Inc.
4 * https://www.huawei.com/
5 * Created by Gao Xiang <gaoxiang25@huawei.com>
6 */
7 #include "internal.h"
8 #include <linux/pagevec.h>
9
erofs_allocpage(struct list_head * pool,gfp_t gfp)10 struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
11 {
12 struct page *page;
13
14 if (!list_empty(pool)) {
15 page = lru_to_page(pool);
16 DBG_BUGON(page_ref_count(page) != 1);
17 list_del(&page->lru);
18 } else {
19 page = alloc_page(gfp);
20 }
21 return page;
22 }
23
24 #if (EROFS_PCPUBUF_NR_PAGES > 0)
25 static struct {
26 u8 data[PAGE_SIZE * EROFS_PCPUBUF_NR_PAGES];
27 } ____cacheline_aligned_in_smp erofs_pcpubuf[NR_CPUS];
28
erofs_get_pcpubuf(unsigned int pagenr)29 void *erofs_get_pcpubuf(unsigned int pagenr)
30 {
31 preempt_disable();
32 return &erofs_pcpubuf[smp_processor_id()].data[pagenr * PAGE_SIZE];
33 }
34 #endif
35
36 #ifdef CONFIG_EROFS_FS_ZIP
37 /* global shrink count (for all mounted EROFS instances) */
38 static atomic_long_t erofs_global_shrink_cnt;
39
erofs_workgroup_get(struct erofs_workgroup * grp)40 static int erofs_workgroup_get(struct erofs_workgroup *grp)
41 {
42 int o;
43
44 repeat:
45 o = erofs_wait_on_workgroup_freezed(grp);
46 if (o <= 0)
47 return -1;
48
49 if (atomic_cmpxchg(&grp->refcount, o, o + 1) != o)
50 goto repeat;
51
52 /* decrease refcount paired by erofs_workgroup_put */
53 if (o == 1)
54 atomic_long_dec(&erofs_global_shrink_cnt);
55 return 0;
56 }
57
erofs_find_workgroup(struct super_block * sb,pgoff_t index)58 struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
59 pgoff_t index)
60 {
61 struct erofs_sb_info *sbi = EROFS_SB(sb);
62 struct erofs_workgroup *grp;
63
64 repeat:
65 rcu_read_lock();
66 grp = xa_load(&sbi->managed_pslots, index);
67 if (grp) {
68 if (erofs_workgroup_get(grp)) {
69 /* prefer to relax rcu read side */
70 rcu_read_unlock();
71 goto repeat;
72 }
73
74 DBG_BUGON(index != grp->index);
75 }
76 rcu_read_unlock();
77 return grp;
78 }
79
erofs_insert_workgroup(struct super_block * sb,struct erofs_workgroup * grp)80 struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
81 struct erofs_workgroup *grp)
82 {
83 struct erofs_sb_info *const sbi = EROFS_SB(sb);
84 struct erofs_workgroup *pre;
85
86 /*
87 * Bump up a reference count before making this visible
88 * to others for the XArray in order to avoid potential
89 * UAF without serialized by xa_lock.
90 */
91 atomic_inc(&grp->refcount);
92
93 repeat:
94 xa_lock(&sbi->managed_pslots);
95 pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
96 NULL, grp, GFP_NOFS);
97 if (pre) {
98 if (xa_is_err(pre)) {
99 pre = ERR_PTR(xa_err(pre));
100 } else if (erofs_workgroup_get(pre)) {
101 /* try to legitimize the current in-tree one */
102 xa_unlock(&sbi->managed_pslots);
103 cond_resched();
104 goto repeat;
105 }
106 atomic_dec(&grp->refcount);
107 grp = pre;
108 }
109 xa_unlock(&sbi->managed_pslots);
110 return grp;
111 }
112
__erofs_workgroup_free(struct erofs_workgroup * grp)113 static void __erofs_workgroup_free(struct erofs_workgroup *grp)
114 {
115 atomic_long_dec(&erofs_global_shrink_cnt);
116 erofs_workgroup_free_rcu(grp);
117 }
118
erofs_workgroup_put(struct erofs_workgroup * grp)119 int erofs_workgroup_put(struct erofs_workgroup *grp)
120 {
121 int count = atomic_dec_return(&grp->refcount);
122
123 if (count == 1)
124 atomic_long_inc(&erofs_global_shrink_cnt);
125 else if (!count)
126 __erofs_workgroup_free(grp);
127 return count;
128 }
129
erofs_try_to_release_workgroup(struct erofs_sb_info * sbi,struct erofs_workgroup * grp)130 static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
131 struct erofs_workgroup *grp)
132 {
133 /*
134 * If managed cache is on, refcount of workgroups
135 * themselves could be < 0 (freezed). In other words,
136 * there is no guarantee that all refcounts > 0.
137 */
138 if (!erofs_workgroup_try_to_freeze(grp, 1))
139 return false;
140
141 /*
142 * Note that all cached pages should be unattached
143 * before deleted from the XArray. Otherwise some
144 * cached pages could be still attached to the orphan
145 * old workgroup when the new one is available in the tree.
146 */
147 if (erofs_try_to_free_all_cached_pages(sbi, grp)) {
148 erofs_workgroup_unfreeze(grp, 1);
149 return false;
150 }
151
152 /*
153 * It's impossible to fail after the workgroup is freezed,
154 * however in order to avoid some race conditions, add a
155 * DBG_BUGON to observe this in advance.
156 */
157 DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp);
158
159 /* last refcount should be connected with its managed pslot. */
160 erofs_workgroup_unfreeze(grp, 0);
161 __erofs_workgroup_free(grp);
162 return true;
163 }
164
erofs_shrink_workstation(struct erofs_sb_info * sbi,unsigned long nr_shrink)165 static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
166 unsigned long nr_shrink)
167 {
168 struct erofs_workgroup *grp;
169 unsigned int freed = 0;
170 unsigned long index;
171
172 xa_lock(&sbi->managed_pslots);
173 xa_for_each(&sbi->managed_pslots, index, grp) {
174 /* try to shrink each valid workgroup */
175 if (!erofs_try_to_release_workgroup(sbi, grp))
176 continue;
177 xa_unlock(&sbi->managed_pslots);
178
179 ++freed;
180 if (!--nr_shrink)
181 return freed;
182 xa_lock(&sbi->managed_pslots);
183 }
184 xa_unlock(&sbi->managed_pslots);
185 return freed;
186 }
187
188 /* protected by 'erofs_sb_list_lock' */
189 static unsigned int shrinker_run_no;
190
191 /* protects the mounted 'erofs_sb_list' */
192 static DEFINE_SPINLOCK(erofs_sb_list_lock);
193 static LIST_HEAD(erofs_sb_list);
194
erofs_shrinker_register(struct super_block * sb)195 void erofs_shrinker_register(struct super_block *sb)
196 {
197 struct erofs_sb_info *sbi = EROFS_SB(sb);
198
199 mutex_init(&sbi->umount_mutex);
200
201 spin_lock(&erofs_sb_list_lock);
202 list_add(&sbi->list, &erofs_sb_list);
203 spin_unlock(&erofs_sb_list_lock);
204 }
205
erofs_shrinker_unregister(struct super_block * sb)206 void erofs_shrinker_unregister(struct super_block *sb)
207 {
208 struct erofs_sb_info *const sbi = EROFS_SB(sb);
209
210 mutex_lock(&sbi->umount_mutex);
211 /* clean up all remaining workgroups in memory */
212 erofs_shrink_workstation(sbi, ~0UL);
213
214 spin_lock(&erofs_sb_list_lock);
215 list_del(&sbi->list);
216 spin_unlock(&erofs_sb_list_lock);
217 mutex_unlock(&sbi->umount_mutex);
218 }
219
erofs_shrink_count(struct shrinker * shrink,struct shrink_control * sc)220 static unsigned long erofs_shrink_count(struct shrinker *shrink,
221 struct shrink_control *sc)
222 {
223 return atomic_long_read(&erofs_global_shrink_cnt);
224 }
225
erofs_shrink_scan(struct shrinker * shrink,struct shrink_control * sc)226 static unsigned long erofs_shrink_scan(struct shrinker *shrink,
227 struct shrink_control *sc)
228 {
229 struct erofs_sb_info *sbi;
230 struct list_head *p;
231
232 unsigned long nr = sc->nr_to_scan;
233 unsigned int run_no;
234 unsigned long freed = 0;
235
236 spin_lock(&erofs_sb_list_lock);
237 do {
238 run_no = ++shrinker_run_no;
239 } while (run_no == 0);
240
241 /* Iterate over all mounted superblocks and try to shrink them */
242 p = erofs_sb_list.next;
243 while (p != &erofs_sb_list) {
244 sbi = list_entry(p, struct erofs_sb_info, list);
245
246 /*
247 * We move the ones we do to the end of the list, so we stop
248 * when we see one we have already done.
249 */
250 if (sbi->shrinker_run_no == run_no)
251 break;
252
253 if (!mutex_trylock(&sbi->umount_mutex)) {
254 p = p->next;
255 continue;
256 }
257
258 spin_unlock(&erofs_sb_list_lock);
259 sbi->shrinker_run_no = run_no;
260
261 freed += erofs_shrink_workstation(sbi, nr - freed);
262
263 spin_lock(&erofs_sb_list_lock);
264 /* Get the next list element before we move this one */
265 p = p->next;
266
267 /*
268 * Move this one to the end of the list to provide some
269 * fairness.
270 */
271 list_move_tail(&sbi->list, &erofs_sb_list);
272 mutex_unlock(&sbi->umount_mutex);
273
274 if (freed >= nr)
275 break;
276 }
277 spin_unlock(&erofs_sb_list_lock);
278 return freed;
279 }
280
281 static struct shrinker erofs_shrinker_info = {
282 .scan_objects = erofs_shrink_scan,
283 .count_objects = erofs_shrink_count,
284 .seeks = DEFAULT_SEEKS,
285 };
286
erofs_init_shrinker(void)287 int __init erofs_init_shrinker(void)
288 {
289 return register_shrinker(&erofs_shrinker_info);
290 }
291
erofs_exit_shrinker(void)292 void erofs_exit_shrinker(void)
293 {
294 unregister_shrinker(&erofs_shrinker_info);
295 }
296 #endif /* !CONFIG_EROFS_FS_ZIP */
297
298