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_folios(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 */
288