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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2016-present, Facebook, Inc.
4 * All rights reserved.
5 *
6 */
7
8#include <linux/bio.h>
9#include <linux/bitmap.h>
10#include <linux/err.h>
11#include <linux/init.h>
12#include <linux/kernel.h>
13#include <linux/mm.h>
14#include <linux/sched/mm.h>
15#include <linux/pagemap.h>
16#include <linux/refcount.h>
17#include <linux/sched.h>
18#include <linux/slab.h>
19#include <linux/zstd.h>
20#include "misc.h"
21#include "compression.h"
22#include "ctree.h"
23
24#define ZSTD_BTRFS_MAX_WINDOWLOG 17
25#define ZSTD_BTRFS_MAX_INPUT (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
26#define ZSTD_BTRFS_DEFAULT_LEVEL 3
27#define ZSTD_BTRFS_MAX_LEVEL 15
28/* 307s to avoid pathologically clashing with transaction commit */
29#define ZSTD_BTRFS_RECLAIM_JIFFIES (307 * HZ)
30
31static ZSTD_parameters zstd_get_btrfs_parameters(unsigned int level,
32 size_t src_len)
33{
34 ZSTD_parameters params = ZSTD_getParams(level, src_len, 0);
35
36 if (params.cParams.windowLog > ZSTD_BTRFS_MAX_WINDOWLOG)
37 params.cParams.windowLog = ZSTD_BTRFS_MAX_WINDOWLOG;
38 WARN_ON(src_len > ZSTD_BTRFS_MAX_INPUT);
39 return params;
40}
41
42struct workspace {
43 void *mem;
44 size_t size;
45 char *buf;
46 unsigned int level;
47 unsigned int req_level;
48 unsigned long last_used; /* jiffies */
49 struct list_head list;
50 struct list_head lru_list;
51 ZSTD_inBuffer in_buf;
52 ZSTD_outBuffer out_buf;
53};
54
55/*
56 * Zstd Workspace Management
57 *
58 * Zstd workspaces have different memory requirements depending on the level.
59 * The zstd workspaces are managed by having individual lists for each level
60 * and a global lru. Forward progress is maintained by protecting a max level
61 * workspace.
62 *
63 * Getting a workspace is done by using the bitmap to identify the levels that
64 * have available workspaces and scans up. This lets us recycle higher level
65 * workspaces because of the monotonic memory guarantee. A workspace's
66 * last_used is only updated if it is being used by the corresponding memory
67 * level. Putting a workspace involves adding it back to the appropriate places
68 * and adding it back to the lru if necessary.
69 *
70 * A timer is used to reclaim workspaces if they have not been used for
71 * ZSTD_BTRFS_RECLAIM_JIFFIES. This helps keep only active workspaces around.
72 * The upper bound is provided by the workqueue limit which is 2 (percpu limit).
73 */
74
75struct zstd_workspace_manager {
76 const struct btrfs_compress_op *ops;
77 spinlock_t lock;
78 struct list_head lru_list;
79 struct list_head idle_ws[ZSTD_BTRFS_MAX_LEVEL];
80 unsigned long active_map;
81 wait_queue_head_t wait;
82 struct timer_list timer;
83};
84
85static struct zstd_workspace_manager wsm;
86
87static size_t zstd_ws_mem_sizes[ZSTD_BTRFS_MAX_LEVEL];
88
89static inline struct workspace *list_to_workspace(struct list_head *list)
90{
91 return container_of(list, struct workspace, list);
92}
93
94void zstd_free_workspace(struct list_head *ws);
95struct list_head *zstd_alloc_workspace(unsigned int level);
96/*
97 * zstd_reclaim_timer_fn - reclaim timer
98 * @t: timer
99 *
100 * This scans the lru_list and attempts to reclaim any workspace that hasn't
101 * been used for ZSTD_BTRFS_RECLAIM_JIFFIES.
102 */
103static void zstd_reclaim_timer_fn(struct timer_list *timer)
104{
105 unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES;
106 struct list_head *pos, *next;
107
108 spin_lock_bh(&wsm.lock);
109
110 if (list_empty(&wsm.lru_list)) {
111 spin_unlock_bh(&wsm.lock);
112 return;
113 }
114
115 list_for_each_prev_safe(pos, next, &wsm.lru_list) {
116 struct workspace *victim = container_of(pos, struct workspace,
117 lru_list);
118 unsigned int level;
119
120 if (time_after(victim->last_used, reclaim_threshold))
121 break;
122
123 /* workspace is in use */
124 if (victim->req_level)
125 continue;
126
127 level = victim->level;
128 list_del(&victim->lru_list);
129 list_del(&victim->list);
130 zstd_free_workspace(&victim->list);
131
132 if (list_empty(&wsm.idle_ws[level - 1]))
133 clear_bit(level - 1, &wsm.active_map);
134
135 }
136
137 if (!list_empty(&wsm.lru_list))
138 mod_timer(&wsm.timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
139
140 spin_unlock_bh(&wsm.lock);
141}
142
143/*
144 * zstd_calc_ws_mem_sizes - calculate monotonic memory bounds
145 *
146 * It is possible based on the level configurations that a higher level
147 * workspace uses less memory than a lower level workspace. In order to reuse
148 * workspaces, this must be made a monotonic relationship. This precomputes
149 * the required memory for each level and enforces the monotonicity between
150 * level and memory required.
151 */
152static void zstd_calc_ws_mem_sizes(void)
153{
154 size_t max_size = 0;
155 unsigned int level;
156
157 for (level = 1; level <= ZSTD_BTRFS_MAX_LEVEL; level++) {
158 ZSTD_parameters params =
159 zstd_get_btrfs_parameters(level, ZSTD_BTRFS_MAX_INPUT);
160 size_t level_size =
161 max_t(size_t,
162 ZSTD_CStreamWorkspaceBound(params.cParams),
163 ZSTD_DStreamWorkspaceBound(ZSTD_BTRFS_MAX_INPUT));
164
165 max_size = max_t(size_t, max_size, level_size);
166 zstd_ws_mem_sizes[level - 1] = max_size;
167 }
168}
169
170void zstd_init_workspace_manager(void)
171{
172 struct list_head *ws;
173 int i;
174
175 zstd_calc_ws_mem_sizes();
176
177 wsm.ops = &btrfs_zstd_compress;
178 spin_lock_init(&wsm.lock);
179 init_waitqueue_head(&wsm.wait);
180 timer_setup(&wsm.timer, zstd_reclaim_timer_fn, 0);
181
182 INIT_LIST_HEAD(&wsm.lru_list);
183 for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++)
184 INIT_LIST_HEAD(&wsm.idle_ws[i]);
185
186 ws = zstd_alloc_workspace(ZSTD_BTRFS_MAX_LEVEL);
187 if (IS_ERR(ws)) {
188 pr_warn(
189 "BTRFS: cannot preallocate zstd compression workspace\n");
190 } else {
191 set_bit(ZSTD_BTRFS_MAX_LEVEL - 1, &wsm.active_map);
192 list_add(ws, &wsm.idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1]);
193 }
194}
195
196void zstd_cleanup_workspace_manager(void)
197{
198 struct workspace *workspace;
199 int i;
200
201 spin_lock_bh(&wsm.lock);
202 for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) {
203 while (!list_empty(&wsm.idle_ws[i])) {
204 workspace = container_of(wsm.idle_ws[i].next,
205 struct workspace, list);
206 list_del(&workspace->list);
207 list_del(&workspace->lru_list);
208 zstd_free_workspace(&workspace->list);
209 }
210 }
211 spin_unlock_bh(&wsm.lock);
212
213 del_timer_sync(&wsm.timer);
214}
215
216/*
217 * zstd_find_workspace - find workspace
218 * @level: compression level
219 *
220 * This iterates over the set bits in the active_map beginning at the requested
221 * compression level. This lets us utilize already allocated workspaces before
222 * allocating a new one. If the workspace is of a larger size, it is used, but
223 * the place in the lru_list and last_used times are not updated. This is to
224 * offer the opportunity to reclaim the workspace in favor of allocating an
225 * appropriately sized one in the future.
226 */
227static struct list_head *zstd_find_workspace(unsigned int level)
228{
229 struct list_head *ws;
230 struct workspace *workspace;
231 int i = level - 1;
232
233 spin_lock_bh(&wsm.lock);
234 for_each_set_bit_from(i, &wsm.active_map, ZSTD_BTRFS_MAX_LEVEL) {
235 if (!list_empty(&wsm.idle_ws[i])) {
236 ws = wsm.idle_ws[i].next;
237 workspace = list_to_workspace(ws);
238 list_del_init(ws);
239 /* keep its place if it's a lower level using this */
240 workspace->req_level = level;
241 if (level == workspace->level)
242 list_del(&workspace->lru_list);
243 if (list_empty(&wsm.idle_ws[i]))
244 clear_bit(i, &wsm.active_map);
245 spin_unlock_bh(&wsm.lock);
246 return ws;
247 }
248 }
249 spin_unlock_bh(&wsm.lock);
250
251 return NULL;
252}
253
254/*
255 * zstd_get_workspace - zstd's get_workspace
256 * @level: compression level
257 *
258 * If @level is 0, then any compression level can be used. Therefore, we begin
259 * scanning from 1. We first scan through possible workspaces and then after
260 * attempt to allocate a new workspace. If we fail to allocate one due to
261 * memory pressure, go to sleep waiting for the max level workspace to free up.
262 */
263struct list_head *zstd_get_workspace(unsigned int level)
264{
265 struct list_head *ws;
266 unsigned int nofs_flag;
267
268 /* level == 0 means we can use any workspace */
269 if (!level)
270 level = 1;
271
272again:
273 ws = zstd_find_workspace(level);
274 if (ws)
275 return ws;
276
277 nofs_flag = memalloc_nofs_save();
278 ws = zstd_alloc_workspace(level);
279 memalloc_nofs_restore(nofs_flag);
280
281 if (IS_ERR(ws)) {
282 DEFINE_WAIT(wait);
283
284 prepare_to_wait(&wsm.wait, &wait, TASK_UNINTERRUPTIBLE);
285 schedule();
286 finish_wait(&wsm.wait, &wait);
287
288 goto again;
289 }
290
291 return ws;
292}
293
294/*
295 * zstd_put_workspace - zstd put_workspace
296 * @ws: list_head for the workspace
297 *
298 * When putting back a workspace, we only need to update the LRU if we are of
299 * the requested compression level. Here is where we continue to protect the
300 * max level workspace or update last_used accordingly. If the reclaim timer
301 * isn't set, it is also set here. Only the max level workspace tries and wakes
302 * up waiting workspaces.
303 */
304void zstd_put_workspace(struct list_head *ws)
305{
306 struct workspace *workspace = list_to_workspace(ws);
307
308 spin_lock_bh(&wsm.lock);
309
310 /* A node is only taken off the lru if we are the corresponding level */
311 if (workspace->req_level == workspace->level) {
312 /* Hide a max level workspace from reclaim */
313 if (list_empty(&wsm.idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1])) {
314 INIT_LIST_HEAD(&workspace->lru_list);
315 } else {
316 workspace->last_used = jiffies;
317 list_add(&workspace->lru_list, &wsm.lru_list);
318 if (!timer_pending(&wsm.timer))
319 mod_timer(&wsm.timer,
320 jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
321 }
322 }
323
324 set_bit(workspace->level - 1, &wsm.active_map);
325 list_add(&workspace->list, &wsm.idle_ws[workspace->level - 1]);
326 workspace->req_level = 0;
327
328 spin_unlock_bh(&wsm.lock);
329
330 if (workspace->level == ZSTD_BTRFS_MAX_LEVEL)
331 cond_wake_up(&wsm.wait);
332}
333
334void zstd_free_workspace(struct list_head *ws)
335{
336 struct workspace *workspace = list_entry(ws, struct workspace, list);
337
338 kvfree(workspace->mem);
339 kfree(workspace->buf);
340 kfree(workspace);
341}
342
343struct list_head *zstd_alloc_workspace(unsigned int level)
344{
345 struct workspace *workspace;
346
347 workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);
348 if (!workspace)
349 return ERR_PTR(-ENOMEM);
350
351 workspace->size = zstd_ws_mem_sizes[level - 1];
352 workspace->level = level;
353 workspace->req_level = level;
354 workspace->last_used = jiffies;
355 workspace->mem = kvmalloc(workspace->size, GFP_KERNEL);
356 workspace->buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
357 if (!workspace->mem || !workspace->buf)
358 goto fail;
359
360 INIT_LIST_HEAD(&workspace->list);
361 INIT_LIST_HEAD(&workspace->lru_list);
362
363 return &workspace->list;
364fail:
365 zstd_free_workspace(&workspace->list);
366 return ERR_PTR(-ENOMEM);
367}
368
369int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
370 u64 start, struct page **pages, unsigned long *out_pages,
371 unsigned long *total_in, unsigned long *total_out)
372{
373 struct workspace *workspace = list_entry(ws, struct workspace, list);
374 ZSTD_CStream *stream;
375 int ret = 0;
376 int nr_pages = 0;
377 struct page *in_page = NULL; /* The current page to read */
378 struct page *out_page = NULL; /* The current page to write to */
379 unsigned long tot_in = 0;
380 unsigned long tot_out = 0;
381 unsigned long len = *total_out;
382 const unsigned long nr_dest_pages = *out_pages;
383 unsigned long max_out = nr_dest_pages * PAGE_SIZE;
384 ZSTD_parameters params = zstd_get_btrfs_parameters(workspace->req_level,
385 len);
386
387 *out_pages = 0;
388 *total_out = 0;
389 *total_in = 0;
390
391 /* Initialize the stream */
392 stream = ZSTD_initCStream(params, len, workspace->mem,
393 workspace->size);
394 if (!stream) {
395 pr_warn("BTRFS: ZSTD_initCStream failed\n");
396 ret = -EIO;
397 goto out;
398 }
399
400 /* map in the first page of input data */
401 in_page = find_get_page(mapping, start >> PAGE_SHIFT);
402 workspace->in_buf.src = kmap(in_page);
403 workspace->in_buf.pos = 0;
404 workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
405
406
407 /* Allocate and map in the output buffer */
408 out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
409 if (out_page == NULL) {
410 ret = -ENOMEM;
411 goto out;
412 }
413 pages[nr_pages++] = out_page;
414 workspace->out_buf.dst = kmap(out_page);
415 workspace->out_buf.pos = 0;
416 workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
417
418 while (1) {
419 size_t ret2;
420
421 ret2 = ZSTD_compressStream(stream, &workspace->out_buf,
422 &workspace->in_buf);
423 if (ZSTD_isError(ret2)) {
424 pr_debug("BTRFS: ZSTD_compressStream returned %d\n",
425 ZSTD_getErrorCode(ret2));
426 ret = -EIO;
427 goto out;
428 }
429
430 /* Check to see if we are making it bigger */
431 if (tot_in + workspace->in_buf.pos > 8192 &&
432 tot_in + workspace->in_buf.pos <
433 tot_out + workspace->out_buf.pos) {
434 ret = -E2BIG;
435 goto out;
436 }
437
438 /* We've reached the end of our output range */
439 if (workspace->out_buf.pos >= max_out) {
440 tot_out += workspace->out_buf.pos;
441 ret = -E2BIG;
442 goto out;
443 }
444
445 /* Check if we need more output space */
446 if (workspace->out_buf.pos == workspace->out_buf.size) {
447 tot_out += PAGE_SIZE;
448 max_out -= PAGE_SIZE;
449 kunmap(out_page);
450 if (nr_pages == nr_dest_pages) {
451 out_page = NULL;
452 ret = -E2BIG;
453 goto out;
454 }
455 out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
456 if (out_page == NULL) {
457 ret = -ENOMEM;
458 goto out;
459 }
460 pages[nr_pages++] = out_page;
461 workspace->out_buf.dst = kmap(out_page);
462 workspace->out_buf.pos = 0;
463 workspace->out_buf.size = min_t(size_t, max_out,
464 PAGE_SIZE);
465 }
466
467 /* We've reached the end of the input */
468 if (workspace->in_buf.pos >= len) {
469 tot_in += workspace->in_buf.pos;
470 break;
471 }
472
473 /* Check if we need more input */
474 if (workspace->in_buf.pos == workspace->in_buf.size) {
475 tot_in += PAGE_SIZE;
476 kunmap(in_page);
477 put_page(in_page);
478
479 start += PAGE_SIZE;
480 len -= PAGE_SIZE;
481 in_page = find_get_page(mapping, start >> PAGE_SHIFT);
482 workspace->in_buf.src = kmap(in_page);
483 workspace->in_buf.pos = 0;
484 workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
485 }
486 }
487 while (1) {
488 size_t ret2;
489
490 ret2 = ZSTD_endStream(stream, &workspace->out_buf);
491 if (ZSTD_isError(ret2)) {
492 pr_debug("BTRFS: ZSTD_endStream returned %d\n",
493 ZSTD_getErrorCode(ret2));
494 ret = -EIO;
495 goto out;
496 }
497 if (ret2 == 0) {
498 tot_out += workspace->out_buf.pos;
499 break;
500 }
501 if (workspace->out_buf.pos >= max_out) {
502 tot_out += workspace->out_buf.pos;
503 ret = -E2BIG;
504 goto out;
505 }
506
507 tot_out += PAGE_SIZE;
508 max_out -= PAGE_SIZE;
509 kunmap(out_page);
510 if (nr_pages == nr_dest_pages) {
511 out_page = NULL;
512 ret = -E2BIG;
513 goto out;
514 }
515 out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
516 if (out_page == NULL) {
517 ret = -ENOMEM;
518 goto out;
519 }
520 pages[nr_pages++] = out_page;
521 workspace->out_buf.dst = kmap(out_page);
522 workspace->out_buf.pos = 0;
523 workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
524 }
525
526 if (tot_out >= tot_in) {
527 ret = -E2BIG;
528 goto out;
529 }
530
531 ret = 0;
532 *total_in = tot_in;
533 *total_out = tot_out;
534out:
535 *out_pages = nr_pages;
536 /* Cleanup */
537 if (in_page) {
538 kunmap(in_page);
539 put_page(in_page);
540 }
541 if (out_page)
542 kunmap(out_page);
543 return ret;
544}
545
546int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
547{
548 struct workspace *workspace = list_entry(ws, struct workspace, list);
549 struct page **pages_in = cb->compressed_pages;
550 u64 disk_start = cb->start;
551 struct bio *orig_bio = cb->orig_bio;
552 size_t srclen = cb->compressed_len;
553 ZSTD_DStream *stream;
554 int ret = 0;
555 unsigned long page_in_index = 0;
556 unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
557 unsigned long buf_start;
558 unsigned long total_out = 0;
559
560 stream = ZSTD_initDStream(
561 ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
562 if (!stream) {
563 pr_debug("BTRFS: ZSTD_initDStream failed\n");
564 ret = -EIO;
565 goto done;
566 }
567
568 workspace->in_buf.src = kmap(pages_in[page_in_index]);
569 workspace->in_buf.pos = 0;
570 workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
571
572 workspace->out_buf.dst = workspace->buf;
573 workspace->out_buf.pos = 0;
574 workspace->out_buf.size = PAGE_SIZE;
575
576 while (1) {
577 size_t ret2;
578
579 ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
580 &workspace->in_buf);
581 if (ZSTD_isError(ret2)) {
582 pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
583 ZSTD_getErrorCode(ret2));
584 ret = -EIO;
585 goto done;
586 }
587 buf_start = total_out;
588 total_out += workspace->out_buf.pos;
589 workspace->out_buf.pos = 0;
590
591 ret = btrfs_decompress_buf2page(workspace->out_buf.dst,
592 buf_start, total_out, disk_start, orig_bio);
593 if (ret == 0)
594 break;
595
596 if (workspace->in_buf.pos >= srclen)
597 break;
598
599 /* Check if we've hit the end of a frame */
600 if (ret2 == 0)
601 break;
602
603 if (workspace->in_buf.pos == workspace->in_buf.size) {
604 kunmap(pages_in[page_in_index++]);
605 if (page_in_index >= total_pages_in) {
606 workspace->in_buf.src = NULL;
607 ret = -EIO;
608 goto done;
609 }
610 srclen -= PAGE_SIZE;
611 workspace->in_buf.src = kmap(pages_in[page_in_index]);
612 workspace->in_buf.pos = 0;
613 workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
614 }
615 }
616 ret = 0;
617 zero_fill_bio(orig_bio);
618done:
619 if (workspace->in_buf.src)
620 kunmap(pages_in[page_in_index]);
621 return ret;
622}
623
624int zstd_decompress(struct list_head *ws, unsigned char *data_in,
625 struct page *dest_page, unsigned long start_byte, size_t srclen,
626 size_t destlen)
627{
628 struct workspace *workspace = list_entry(ws, struct workspace, list);
629 ZSTD_DStream *stream;
630 int ret = 0;
631 size_t ret2;
632 unsigned long total_out = 0;
633 unsigned long pg_offset = 0;
634
635 stream = ZSTD_initDStream(
636 ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
637 if (!stream) {
638 pr_warn("BTRFS: ZSTD_initDStream failed\n");
639 ret = -EIO;
640 goto finish;
641 }
642
643 destlen = min_t(size_t, destlen, PAGE_SIZE);
644
645 workspace->in_buf.src = data_in;
646 workspace->in_buf.pos = 0;
647 workspace->in_buf.size = srclen;
648
649 workspace->out_buf.dst = workspace->buf;
650 workspace->out_buf.pos = 0;
651 workspace->out_buf.size = PAGE_SIZE;
652
653 ret2 = 1;
654 while (pg_offset < destlen
655 && workspace->in_buf.pos < workspace->in_buf.size) {
656 unsigned long buf_start;
657 unsigned long buf_offset;
658 unsigned long bytes;
659
660 /* Check if the frame is over and we still need more input */
661 if (ret2 == 0) {
662 pr_debug("BTRFS: ZSTD_decompressStream ended early\n");
663 ret = -EIO;
664 goto finish;
665 }
666 ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
667 &workspace->in_buf);
668 if (ZSTD_isError(ret2)) {
669 pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
670 ZSTD_getErrorCode(ret2));
671 ret = -EIO;
672 goto finish;
673 }
674
675 buf_start = total_out;
676 total_out += workspace->out_buf.pos;
677 workspace->out_buf.pos = 0;
678
679 if (total_out <= start_byte)
680 continue;
681
682 if (total_out > start_byte && buf_start < start_byte)
683 buf_offset = start_byte - buf_start;
684 else
685 buf_offset = 0;
686
687 bytes = min_t(unsigned long, destlen - pg_offset,
688 workspace->out_buf.size - buf_offset);
689
690 memcpy_to_page(dest_page, pg_offset,
691 workspace->out_buf.dst + buf_offset, bytes);
692
693 pg_offset += bytes;
694 }
695 ret = 0;
696finish:
697 if (pg_offset < destlen) {
698 memzero_page(dest_page, pg_offset, destlen - pg_offset);
699 }
700 return ret;
701}
702
703const struct btrfs_compress_op btrfs_zstd_compress = {
704 /* ZSTD uses own workspace manager */
705 .workspace_manager = NULL,
706 .max_level = ZSTD_BTRFS_MAX_LEVEL,
707 .default_level = ZSTD_BTRFS_DEFAULT_LEVEL,
708};