1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2018 HUAWEI, Inc.
  4 *             https://www.huawei.com/
  5 * Copyright (C) 2024 Alibaba Cloud
  6 */
  7#include "internal.h"
  8
  9struct z_erofs_gbuf {
 10	spinlock_t lock;
 11	void *ptr;
 12	struct page **pages;
 13	unsigned int nrpages;
 14};
 15
 16static struct z_erofs_gbuf *z_erofs_gbufpool, *z_erofs_rsvbuf;
 17static unsigned int z_erofs_gbuf_count, z_erofs_gbuf_nrpages,
 18		z_erofs_rsv_nrpages;
 19
 20module_param_named(global_buffers, z_erofs_gbuf_count, uint, 0444);
 21module_param_named(reserved_pages, z_erofs_rsv_nrpages, uint, 0444);
 22
 23atomic_long_t erofs_global_shrink_cnt;	/* for all mounted instances */
 24
 25/* protects `erofs_sb_list_lock` and the mounted `erofs_sb_list` */
 26static DEFINE_SPINLOCK(erofs_sb_list_lock);
 27static LIST_HEAD(erofs_sb_list);
 28static unsigned int shrinker_run_no;
 29static struct shrinker *erofs_shrinker_info;
 30
 31static unsigned int z_erofs_gbuf_id(void)
 32{
 33	return raw_smp_processor_id() % z_erofs_gbuf_count;
 34}
 35
 36void *z_erofs_get_gbuf(unsigned int requiredpages)
 37	__acquires(gbuf->lock)
 38{
 39	struct z_erofs_gbuf *gbuf;
 40
 41	migrate_disable();
 42	gbuf = &z_erofs_gbufpool[z_erofs_gbuf_id()];
 43	spin_lock(&gbuf->lock);
 44	/* check if the buffer is too small */
 45	if (requiredpages > gbuf->nrpages) {
 46		spin_unlock(&gbuf->lock);
 47		migrate_enable();
 48		/* (for sparse checker) pretend gbuf->lock is still taken */
 49		__acquire(gbuf->lock);
 50		return NULL;
 51	}
 52	return gbuf->ptr;
 53}
 54
 55void z_erofs_put_gbuf(void *ptr) __releases(gbuf->lock)
 56{
 57	struct z_erofs_gbuf *gbuf;
 58
 59	gbuf = &z_erofs_gbufpool[z_erofs_gbuf_id()];
 60	DBG_BUGON(gbuf->ptr != ptr);
 61	spin_unlock(&gbuf->lock);
 62	migrate_enable();
 63}
 64
 65int z_erofs_gbuf_growsize(unsigned int nrpages)
 66{
 67	static DEFINE_MUTEX(gbuf_resize_mutex);
 68	struct page **tmp_pages = NULL;
 69	struct z_erofs_gbuf *gbuf;
 70	void *ptr, *old_ptr;
 71	int last, i, j;
 72
 73	mutex_lock(&gbuf_resize_mutex);
 74	/* avoid shrinking gbufs, since no idea how many fses rely on */
 75	if (nrpages <= z_erofs_gbuf_nrpages) {
 76		mutex_unlock(&gbuf_resize_mutex);
 77		return 0;
 78	}
 79
 80	for (i = 0; i < z_erofs_gbuf_count; ++i) {
 81		gbuf = &z_erofs_gbufpool[i];
 82		tmp_pages = kcalloc(nrpages, sizeof(*tmp_pages), GFP_KERNEL);
 83		if (!tmp_pages)
 84			goto out;
 85
 86		for (j = 0; j < gbuf->nrpages; ++j)
 87			tmp_pages[j] = gbuf->pages[j];
 88		do {
 89			last = j;
 90			j = alloc_pages_bulk_array(GFP_KERNEL, nrpages,
 91						   tmp_pages);
 92			if (last == j)
 93				goto out;
 94		} while (j != nrpages);
 95
 96		ptr = vmap(tmp_pages, nrpages, VM_MAP, PAGE_KERNEL);
 97		if (!ptr)
 98			goto out;
 99
100		spin_lock(&gbuf->lock);
101		kfree(gbuf->pages);
102		gbuf->pages = tmp_pages;
103		old_ptr = gbuf->ptr;
104		gbuf->ptr = ptr;
105		gbuf->nrpages = nrpages;
106		spin_unlock(&gbuf->lock);
107		if (old_ptr)
108			vunmap(old_ptr);
109	}
110	z_erofs_gbuf_nrpages = nrpages;
111out:
112	if (i < z_erofs_gbuf_count && tmp_pages) {
113		for (j = 0; j < nrpages; ++j)
114			if (tmp_pages[j] && (j >= gbuf->nrpages ||
115					     tmp_pages[j] != gbuf->pages[j]))
116				__free_page(tmp_pages[j]);
117		kfree(tmp_pages);
118	}
119	mutex_unlock(&gbuf_resize_mutex);
120	return i < z_erofs_gbuf_count ? -ENOMEM : 0;
121}
122
123int __init z_erofs_gbuf_init(void)
124{
125	unsigned int i, total = num_possible_cpus();
126
127	if (z_erofs_gbuf_count)
128		total = min(z_erofs_gbuf_count, total);
129	z_erofs_gbuf_count = total;
130
131	/* The last (special) global buffer is the reserved buffer */
132	total += !!z_erofs_rsv_nrpages;
133
134	z_erofs_gbufpool = kcalloc(total, sizeof(*z_erofs_gbufpool),
135				   GFP_KERNEL);
136	if (!z_erofs_gbufpool)
137		return -ENOMEM;
138
139	if (z_erofs_rsv_nrpages) {
140		z_erofs_rsvbuf = &z_erofs_gbufpool[total - 1];
141		z_erofs_rsvbuf->pages = kcalloc(z_erofs_rsv_nrpages,
142				sizeof(*z_erofs_rsvbuf->pages), GFP_KERNEL);
143		if (!z_erofs_rsvbuf->pages) {
144			z_erofs_rsvbuf = NULL;
145			z_erofs_rsv_nrpages = 0;
146		}
147	}
148	for (i = 0; i < total; ++i)
149		spin_lock_init(&z_erofs_gbufpool[i].lock);
150	return 0;
151}
152
153void z_erofs_gbuf_exit(void)
154{
155	int i, j;
156
157	for (i = 0; i < z_erofs_gbuf_count + (!!z_erofs_rsvbuf); ++i) {
158		struct z_erofs_gbuf *gbuf = &z_erofs_gbufpool[i];
159
160		if (gbuf->ptr) {
161			vunmap(gbuf->ptr);
162			gbuf->ptr = NULL;
163		}
164
165		if (!gbuf->pages)
166			continue;
167
168		for (j = 0; j < gbuf->nrpages; ++j)
169			if (gbuf->pages[j])
170				put_page(gbuf->pages[j]);
171		kfree(gbuf->pages);
172		gbuf->pages = NULL;
173	}
174	kfree(z_erofs_gbufpool);
175}
176
177struct page *__erofs_allocpage(struct page **pagepool, gfp_t gfp, bool tryrsv)
178{
179	struct page *page = *pagepool;
180
181	if (page) {
182		*pagepool = (struct page *)page_private(page);
183	} else if (tryrsv && z_erofs_rsvbuf && z_erofs_rsvbuf->nrpages) {
184		spin_lock(&z_erofs_rsvbuf->lock);
185		if (z_erofs_rsvbuf->nrpages)
186			page = z_erofs_rsvbuf->pages[--z_erofs_rsvbuf->nrpages];
187		spin_unlock(&z_erofs_rsvbuf->lock);
188	}
189	if (!page)
190		page = alloc_page(gfp);
191	DBG_BUGON(page && page_ref_count(page) != 1);
192	return page;
193}
194
195void erofs_release_pages(struct page **pagepool)
196{
197	while (*pagepool) {
198		struct page *page = *pagepool;
199
200		*pagepool = (struct page *)page_private(page);
201		/* try to fill reserved global pool first */
202		if (z_erofs_rsvbuf && z_erofs_rsvbuf->nrpages <
203				z_erofs_rsv_nrpages) {
204			spin_lock(&z_erofs_rsvbuf->lock);
205			if (z_erofs_rsvbuf->nrpages < z_erofs_rsv_nrpages) {
206				z_erofs_rsvbuf->pages[z_erofs_rsvbuf->nrpages++]
207						= page;
208				spin_unlock(&z_erofs_rsvbuf->lock);
209				continue;
210			}
211			spin_unlock(&z_erofs_rsvbuf->lock);
212		}
213		put_page(page);
214	}
215}
216
217void erofs_shrinker_register(struct super_block *sb)
218{
219	struct erofs_sb_info *sbi = EROFS_SB(sb);
220
221	mutex_init(&sbi->umount_mutex);
222
223	spin_lock(&erofs_sb_list_lock);
224	list_add(&sbi->list, &erofs_sb_list);
225	spin_unlock(&erofs_sb_list_lock);
226}
227
228void erofs_shrinker_unregister(struct super_block *sb)
229{
230	struct erofs_sb_info *const sbi = EROFS_SB(sb);
231
232	mutex_lock(&sbi->umount_mutex);
233	while (!xa_empty(&sbi->managed_pslots)) {
234		z_erofs_shrink_scan(sbi, ~0UL);
235		cond_resched();
236	}
237	spin_lock(&erofs_sb_list_lock);
238	list_del(&sbi->list);
239	spin_unlock(&erofs_sb_list_lock);
240	mutex_unlock(&sbi->umount_mutex);
241}
242
243static unsigned long erofs_shrink_count(struct shrinker *shrink,
244					struct shrink_control *sc)
245{
246	return atomic_long_read(&erofs_global_shrink_cnt);
247}
248
249static unsigned long erofs_shrink_scan(struct shrinker *shrink,
250				       struct shrink_control *sc)
251{
252	struct erofs_sb_info *sbi;
253	struct list_head *p;
254
255	unsigned long nr = sc->nr_to_scan;
256	unsigned int run_no;
257	unsigned long freed = 0;
258
259	spin_lock(&erofs_sb_list_lock);
260	do {
261		run_no = ++shrinker_run_no;
262	} while (run_no == 0);
263
264	/* Iterate over all mounted superblocks and try to shrink them */
265	p = erofs_sb_list.next;
266	while (p != &erofs_sb_list) {
267		sbi = list_entry(p, struct erofs_sb_info, list);
268
269		/*
270		 * We move the ones we do to the end of the list, so we stop
271		 * when we see one we have already done.
272		 */
273		if (sbi->shrinker_run_no == run_no)
274			break;
275
276		if (!mutex_trylock(&sbi->umount_mutex)) {
277			p = p->next;
278			continue;
279		}
280
281		spin_unlock(&erofs_sb_list_lock);
282		sbi->shrinker_run_no = run_no;
283		freed += z_erofs_shrink_scan(sbi, nr - freed);
284		spin_lock(&erofs_sb_list_lock);
285		/* Get the next list element before we move this one */
286		p = p->next;
287
288		/*
289		 * Move this one to the end of the list to provide some
290		 * fairness.
291		 */
292		list_move_tail(&sbi->list, &erofs_sb_list);
293		mutex_unlock(&sbi->umount_mutex);
294
295		if (freed >= nr)
296			break;
297	}
298	spin_unlock(&erofs_sb_list_lock);
299	return freed;
300}
301
302int __init erofs_init_shrinker(void)
303{
304	erofs_shrinker_info = shrinker_alloc(0, "erofs-shrinker");
305	if (!erofs_shrinker_info)
306		return -ENOMEM;
307
308	erofs_shrinker_info->count_objects = erofs_shrink_count;
309	erofs_shrinker_info->scan_objects = erofs_shrink_scan;
310	shrinker_register(erofs_shrinker_info);
311	return 0;
312}
313
314void erofs_exit_shrinker(void)
315{
316	shrinker_free(erofs_shrinker_info);
317}