zstd.c revision bbaf9715
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 = page_address(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);
409	if (out_page == NULL) {
410		ret = -ENOMEM;
411		goto out;
412	}
413	pages[nr_pages++] = out_page;
414	workspace->out_buf.dst = page_address(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			if (nr_pages == nr_dest_pages) {
450				out_page = NULL;
451				ret = -E2BIG;
452				goto out;
453			}
454			out_page = alloc_page(GFP_NOFS);
455			if (out_page == NULL) {
456				ret = -ENOMEM;
457				goto out;
458			}
459			pages[nr_pages++] = out_page;
460			workspace->out_buf.dst = page_address(out_page);
461			workspace->out_buf.pos = 0;
462			workspace->out_buf.size = min_t(size_t, max_out,
463							PAGE_SIZE);
464		}
465
466		/* We've reached the end of the input */
467		if (workspace->in_buf.pos >= len) {
468			tot_in += workspace->in_buf.pos;
469			break;
470		}
471
472		/* Check if we need more input */
473		if (workspace->in_buf.pos == workspace->in_buf.size) {
474			tot_in += PAGE_SIZE;
475			put_page(in_page);
476
477			start += PAGE_SIZE;
478			len -= PAGE_SIZE;
479			in_page = find_get_page(mapping, start >> PAGE_SHIFT);
480			workspace->in_buf.src = page_address(in_page);
481			workspace->in_buf.pos = 0;
482			workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
483		}
484	}
485	while (1) {
486		size_t ret2;
487
488		ret2 = ZSTD_endStream(stream, &workspace->out_buf);
489		if (ZSTD_isError(ret2)) {
490			pr_debug("BTRFS: ZSTD_endStream returned %d\n",
491					ZSTD_getErrorCode(ret2));
492			ret = -EIO;
493			goto out;
494		}
495		if (ret2 == 0) {
496			tot_out += workspace->out_buf.pos;
497			break;
498		}
499		if (workspace->out_buf.pos >= max_out) {
500			tot_out += workspace->out_buf.pos;
501			ret = -E2BIG;
502			goto out;
503		}
504
505		tot_out += PAGE_SIZE;
506		max_out -= PAGE_SIZE;
507		if (nr_pages == nr_dest_pages) {
508			out_page = NULL;
509			ret = -E2BIG;
510			goto out;
511		}
512		out_page = alloc_page(GFP_NOFS);
513		if (out_page == NULL) {
514			ret = -ENOMEM;
515			goto out;
516		}
517		pages[nr_pages++] = out_page;
518		workspace->out_buf.dst = page_address(out_page);
519		workspace->out_buf.pos = 0;
520		workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
521	}
522
523	if (tot_out >= tot_in) {
524		ret = -E2BIG;
525		goto out;
526	}
527
528	ret = 0;
529	*total_in = tot_in;
530	*total_out = tot_out;
531out:
532	*out_pages = nr_pages;
533	/* Cleanup */
534	if (in_page)
535		put_page(in_page);
536	return ret;
537}
538
539int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
540{
541	struct workspace *workspace = list_entry(ws, struct workspace, list);
542	struct page **pages_in = cb->compressed_pages;
543	u64 disk_start = cb->start;
544	struct bio *orig_bio = cb->orig_bio;
545	size_t srclen = cb->compressed_len;
546	ZSTD_DStream *stream;
547	int ret = 0;
548	unsigned long page_in_index = 0;
549	unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
550	unsigned long buf_start;
551	unsigned long total_out = 0;
552
553	stream = ZSTD_initDStream(
554			ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
555	if (!stream) {
556		pr_debug("BTRFS: ZSTD_initDStream failed\n");
557		ret = -EIO;
558		goto done;
559	}
560
561	workspace->in_buf.src = page_address(pages_in[page_in_index]);
562	workspace->in_buf.pos = 0;
563	workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
564
565	workspace->out_buf.dst = workspace->buf;
566	workspace->out_buf.pos = 0;
567	workspace->out_buf.size = PAGE_SIZE;
568
569	while (1) {
570		size_t ret2;
571
572		ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
573				&workspace->in_buf);
574		if (ZSTD_isError(ret2)) {
575			pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
576					ZSTD_getErrorCode(ret2));
577			ret = -EIO;
578			goto done;
579		}
580		buf_start = total_out;
581		total_out += workspace->out_buf.pos;
582		workspace->out_buf.pos = 0;
583
584		ret = btrfs_decompress_buf2page(workspace->out_buf.dst,
585				buf_start, total_out, disk_start, orig_bio);
586		if (ret == 0)
587			break;
588
589		if (workspace->in_buf.pos >= srclen)
590			break;
591
592		/* Check if we've hit the end of a frame */
593		if (ret2 == 0)
594			break;
595
596		if (workspace->in_buf.pos == workspace->in_buf.size) {
597			page_in_index++;
598			if (page_in_index >= total_pages_in) {
599				workspace->in_buf.src = NULL;
600				ret = -EIO;
601				goto done;
602			}
603			srclen -= PAGE_SIZE;
604			workspace->in_buf.src = page_address(pages_in[page_in_index]);
605			workspace->in_buf.pos = 0;
606			workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
607		}
608	}
609	ret = 0;
610	zero_fill_bio(orig_bio);
611done:
612	return ret;
613}
614
615int zstd_decompress(struct list_head *ws, unsigned char *data_in,
616		struct page *dest_page, unsigned long start_byte, size_t srclen,
617		size_t destlen)
618{
619	struct workspace *workspace = list_entry(ws, struct workspace, list);
620	ZSTD_DStream *stream;
621	int ret = 0;
622	size_t ret2;
623	unsigned long total_out = 0;
624	unsigned long pg_offset = 0;
625
626	stream = ZSTD_initDStream(
627			ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
628	if (!stream) {
629		pr_warn("BTRFS: ZSTD_initDStream failed\n");
630		ret = -EIO;
631		goto finish;
632	}
633
634	destlen = min_t(size_t, destlen, PAGE_SIZE);
635
636	workspace->in_buf.src = data_in;
637	workspace->in_buf.pos = 0;
638	workspace->in_buf.size = srclen;
639
640	workspace->out_buf.dst = workspace->buf;
641	workspace->out_buf.pos = 0;
642	workspace->out_buf.size = PAGE_SIZE;
643
644	ret2 = 1;
645	while (pg_offset < destlen
646	       && workspace->in_buf.pos < workspace->in_buf.size) {
647		unsigned long buf_start;
648		unsigned long buf_offset;
649		unsigned long bytes;
650
651		/* Check if the frame is over and we still need more input */
652		if (ret2 == 0) {
653			pr_debug("BTRFS: ZSTD_decompressStream ended early\n");
654			ret = -EIO;
655			goto finish;
656		}
657		ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
658				&workspace->in_buf);
659		if (ZSTD_isError(ret2)) {
660			pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
661					ZSTD_getErrorCode(ret2));
662			ret = -EIO;
663			goto finish;
664		}
665
666		buf_start = total_out;
667		total_out += workspace->out_buf.pos;
668		workspace->out_buf.pos = 0;
669
670		if (total_out <= start_byte)
671			continue;
672
673		if (total_out > start_byte && buf_start < start_byte)
674			buf_offset = start_byte - buf_start;
675		else
676			buf_offset = 0;
677
678		bytes = min_t(unsigned long, destlen - pg_offset,
679				workspace->out_buf.size - buf_offset);
680
681		memcpy_to_page(dest_page, pg_offset,
682			       workspace->out_buf.dst + buf_offset, bytes);
683
684		pg_offset += bytes;
685	}
686	ret = 0;
687finish:
688	if (pg_offset < destlen) {
689		memzero_page(dest_page, pg_offset, destlen - pg_offset);
690	}
691	return ret;
692}
693
694const struct btrfs_compress_op btrfs_zstd_compress = {
695	/* ZSTD uses own workspace manager */
696	.workspace_manager = NULL,
697	.max_level	= ZSTD_BTRFS_MAX_LEVEL,
698	.default_level	= ZSTD_BTRFS_DEFAULT_LEVEL,
699};
700