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linux-next/fs/btrfs/zstd.c
Dennis Zhou 3f93aef535 btrfs: add zstd compression level support 
Zstd compression requires different amounts of memory for each level of
compression. The prior patches implemented indirection to allow for each
compression type to manage their workspaces independently. This patch
uses this indirection to implement compression level support for zstd.

To manage the additional memory require, each compression level has its
own queue of workspaces. A global LRU is used to help with reclaim.
Reclaim is done via a timer which provides a mechanism to decrease
memory utilization by keeping only workspaces around that are sized
appropriately. Forward progress is guaranteed by a preallocated max
workspace hidden from the LRU.

When getting a workspace, it uses a bitmap to identify the levels that
are populated and scans up. If it finds a workspace that is greater than
it, it uses it, but does not update the last_used time and the
corresponding place in the LRU. If we hit memory pressure, we sleep on
the max level workspace. We continue to rescan in case we can use a
smaller workspace, but eventually should be able to obtain the max level
workspace or allocate one again should memory pressure subside.

The memory requirement for decompression is the same as level 1, and
therefore can use any of available workspace.

The number of workspaces is bound by an upper limit of the workqueue's
limit which currently is 2 (percpu limit). The reclaim timer is used to
free inactive/improperly sized workspaces and is set to 307s to avoid
colliding with transaction commit (every 30s).

Repeating the experiment from v2 [1], the Silesia corpus was copied to a
btrfs filesystem 10 times and then read back after dropping the caches.
The btrfs filesystem was on an SSD.

Level   Ratio   Compression (MB/s)  Decompression (MB/s)  Memory (KB)
1       2.658        438.47                910.51            780
2       2.744        364.86                886.55           1004
3       2.801        336.33                828.41           1260
4       2.858        286.71                886.55           1260
5       2.916        212.77                556.84           1388
6       2.363        119.82                990.85           1516
7       3.000        154.06                849.30           1516
8       3.011        159.54                875.03           1772
9       3.025        100.51                940.15           1772
10      3.033        118.97                616.26           1772
11      3.036         94.19                802.11           1772
12      3.037         73.45                931.49           1772
13      3.041         55.17                835.26           2284
14      3.087         44.70                716.78           2547
15      3.126         37.30                878.84           2547

[1] https://lore.kernel.org/linux-btrfs/20181031181108.289340-1-terrelln@fb.com/

Cc: Nick Terrell <terrelln@fb.com>
Cc: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-02-25 14:13:33 +01:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2016-present, Facebook, Inc.
* All rights reserved.
*
*/
#include <linux/bio.h>
#include <linux/bitmap.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/pagemap.h>
#include <linux/refcount.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/zstd.h>
#include "compression.h"
#include "ctree.h"
#define ZSTD_BTRFS_MAX_WINDOWLOG 17
#define ZSTD_BTRFS_MAX_INPUT (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
#define ZSTD_BTRFS_DEFAULT_LEVEL 3
#define ZSTD_BTRFS_MAX_LEVEL 15
/* 307s to avoid pathologically clashing with transaction commit */
#define ZSTD_BTRFS_RECLAIM_JIFFIES (307 * HZ)
static ZSTD_parameters zstd_get_btrfs_parameters(unsigned int level,
size_t src_len)
{
ZSTD_parameters params = ZSTD_getParams(level, src_len, 0);
if (params.cParams.windowLog > ZSTD_BTRFS_MAX_WINDOWLOG)
params.cParams.windowLog = ZSTD_BTRFS_MAX_WINDOWLOG;
WARN_ON(src_len > ZSTD_BTRFS_MAX_INPUT);
return params;
}
struct workspace {
void *mem;
size_t size;
char *buf;
unsigned int level;
unsigned int req_level;
unsigned long last_used; /* jiffies */
struct list_head list;
struct list_head lru_list;
ZSTD_inBuffer in_buf;
ZSTD_outBuffer out_buf;
};
/*
* Zstd Workspace Management
*
* Zstd workspaces have different memory requirements depending on the level.
* The zstd workspaces are managed by having individual lists for each level
* and a global lru. Forward progress is maintained by protecting a max level
* workspace.
*
* Getting a workspace is done by using the bitmap to identify the levels that
* have available workspaces and scans up. This lets us recycle higher level
* workspaces because of the monotonic memory guarantee. A workspace's
* last_used is only updated if it is being used by the corresponding memory
* level. Putting a workspace involves adding it back to the appropriate places
* and adding it back to the lru if necessary.
*
* A timer is used to reclaim workspaces if they have not been used for
* ZSTD_BTRFS_RECLAIM_JIFFIES. This helps keep only active workspaces around.
* The upper bound is provided by the workqueue limit which is 2 (percpu limit).
*/
struct zstd_workspace_manager {
const struct btrfs_compress_op *ops;
spinlock_t lock;
struct list_head lru_list;
struct list_head idle_ws[ZSTD_BTRFS_MAX_LEVEL];
unsigned long active_map;
wait_queue_head_t wait;
struct timer_list timer;
};
static struct zstd_workspace_manager wsm;
static size_t zstd_ws_mem_sizes[ZSTD_BTRFS_MAX_LEVEL];
static inline struct workspace *list_to_workspace(struct list_head *list)
{
return container_of(list, struct workspace, list);
}
/*
* zstd_reclaim_timer_fn - reclaim timer
* @t: timer
*
* This scans the lru_list and attempts to reclaim any workspace that hasn't
* been used for ZSTD_BTRFS_RECLAIM_JIFFIES.
*/
static void zstd_reclaim_timer_fn(struct timer_list *timer)
{
unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES;
struct list_head *pos, *next;
spin_lock(&wsm.lock);
if (list_empty(&wsm.lru_list)) {
spin_unlock(&wsm.lock);
return;
}
list_for_each_prev_safe(pos, next, &wsm.lru_list) {
struct workspace *victim = container_of(pos, struct workspace,
lru_list);
unsigned int level;
if (time_after(victim->last_used, reclaim_threshold))
break;
/* workspace is in use */
if (victim->req_level)
continue;
level = victim->level;
list_del(&victim->lru_list);
list_del(&victim->list);
wsm.ops->free_workspace(&victim->list);
if (list_empty(&wsm.idle_ws[level - 1]))
clear_bit(level - 1, &wsm.active_map);
}
if (!list_empty(&wsm.lru_list))
mod_timer(&wsm.timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
spin_unlock(&wsm.lock);
}
/*
* zstd_calc_ws_mem_sizes - calculate monotonic memory bounds
*
* It is possible based on the level configurations that a higher level
* workspace uses less memory than a lower level workspace. In order to reuse
* workspaces, this must be made a monotonic relationship. This precomputes
* the required memory for each level and enforces the monotonicity between
* level and memory required.
*/
static void zstd_calc_ws_mem_sizes(void)
{
size_t max_size = 0;
unsigned int level;
for (level = 1; level <= ZSTD_BTRFS_MAX_LEVEL; level++) {
ZSTD_parameters params =
zstd_get_btrfs_parameters(level, ZSTD_BTRFS_MAX_INPUT);
size_t level_size =
max_t(size_t,
ZSTD_CStreamWorkspaceBound(params.cParams),
ZSTD_DStreamWorkspaceBound(ZSTD_BTRFS_MAX_INPUT));
max_size = max_t(size_t, max_size, level_size);
zstd_ws_mem_sizes[level - 1] = max_size;
}
}
static void zstd_init_workspace_manager(void)
{
struct list_head *ws;
int i;
zstd_calc_ws_mem_sizes();
wsm.ops = &btrfs_zstd_compress;
spin_lock_init(&wsm.lock);
init_waitqueue_head(&wsm.wait);
timer_setup(&wsm.timer, zstd_reclaim_timer_fn, 0);
INIT_LIST_HEAD(&wsm.lru_list);
for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++)
INIT_LIST_HEAD(&wsm.idle_ws[i]);
ws = wsm.ops->alloc_workspace(ZSTD_BTRFS_MAX_LEVEL);
if (IS_ERR(ws)) {
pr_warn(
"BTRFS: cannot preallocate zstd compression workspace\n");
} else {
set_bit(ZSTD_BTRFS_MAX_LEVEL - 1, &wsm.active_map);
list_add(ws, &wsm.idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1]);
}
}
static void zstd_cleanup_workspace_manager(void)
{
struct workspace *workspace;
int i;
del_timer(&wsm.timer);
for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) {
while (!list_empty(&wsm.idle_ws[i])) {
workspace = container_of(wsm.idle_ws[i].next,
struct workspace, list);
list_del(&workspace->list);
list_del(&workspace->lru_list);
wsm.ops->free_workspace(&workspace->list);
}
}
}
/*
* zstd_find_workspace - find workspace
* @level: compression level
*
* This iterates over the set bits in the active_map beginning at the requested
* compression level. This lets us utilize already allocated workspaces before
* allocating a new one. If the workspace is of a larger size, it is used, but
* the place in the lru_list and last_used times are not updated. This is to
* offer the opportunity to reclaim the workspace in favor of allocating an
* appropriately sized one in the future.
*/
static struct list_head *zstd_find_workspace(unsigned int level)
{
struct list_head *ws;
struct workspace *workspace;
int i = level - 1;
spin_lock(&wsm.lock);
for_each_set_bit_from(i, &wsm.active_map, ZSTD_BTRFS_MAX_LEVEL) {
if (!list_empty(&wsm.idle_ws[i])) {
ws = wsm.idle_ws[i].next;
workspace = list_to_workspace(ws);
list_del_init(ws);
/* keep its place if it's a lower level using this */
workspace->req_level = level;
if (level == workspace->level)
list_del(&workspace->lru_list);
if (list_empty(&wsm.idle_ws[i]))
clear_bit(i, &wsm.active_map);
spin_unlock(&wsm.lock);
return ws;
}
}
spin_unlock(&wsm.lock);
return NULL;
}
/*
* zstd_get_workspace - zstd's get_workspace
* @level: compression level
*
* If @level is 0, then any compression level can be used. Therefore, we begin
* scanning from 1. We first scan through possible workspaces and then after
* attempt to allocate a new workspace. If we fail to allocate one due to
* memory pressure, go to sleep waiting for the max level workspace to free up.
*/
static struct list_head *zstd_get_workspace(unsigned int level)
{
struct list_head *ws;
unsigned int nofs_flag;
/* level == 0 means we can use any workspace */
if (!level)
level = 1;
again:
ws = zstd_find_workspace(level);
if (ws)
return ws;
nofs_flag = memalloc_nofs_save();
ws = wsm.ops->alloc_workspace(level);
memalloc_nofs_restore(nofs_flag);
if (IS_ERR(ws)) {
DEFINE_WAIT(wait);
prepare_to_wait(&wsm.wait, &wait, TASK_UNINTERRUPTIBLE);
schedule();
finish_wait(&wsm.wait, &wait);
goto again;
}
return ws;
}
/*
* zstd_put_workspace - zstd put_workspace
* @ws: list_head for the workspace
*
* When putting back a workspace, we only need to update the LRU if we are of
* the requested compression level. Here is where we continue to protect the
* max level workspace or update last_used accordingly. If the reclaim timer
* isn't set, it is also set here. Only the max level workspace tries and wakes
* up waiting workspaces.
*/
static void zstd_put_workspace(struct list_head *ws)
{
struct workspace *workspace = list_to_workspace(ws);
spin_lock(&wsm.lock);
/* A node is only taken off the lru if we are the corresponding level */
if (workspace->req_level == workspace->level) {
/* Hide a max level workspace from reclaim */
if (list_empty(&wsm.idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1])) {
INIT_LIST_HEAD(&workspace->lru_list);
} else {
workspace->last_used = jiffies;
list_add(&workspace->lru_list, &wsm.lru_list);
if (!timer_pending(&wsm.timer))
mod_timer(&wsm.timer,
jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
}
}
set_bit(workspace->level - 1, &wsm.active_map);
list_add(&workspace->list, &wsm.idle_ws[workspace->level - 1]);
workspace->req_level = 0;
spin_unlock(&wsm.lock);
if (workspace->level == ZSTD_BTRFS_MAX_LEVEL)
cond_wake_up(&wsm.wait);
}
static void zstd_free_workspace(struct list_head *ws)
{
struct workspace *workspace = list_entry(ws, struct workspace, list);
kvfree(workspace->mem);
kfree(workspace->buf);
kfree(workspace);
}
static struct list_head *zstd_alloc_workspace(unsigned int level)
{
struct workspace *workspace;
workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);
if (!workspace)
return ERR_PTR(-ENOMEM);
workspace->size = zstd_ws_mem_sizes[level - 1];
workspace->level = level;
workspace->req_level = level;
workspace->last_used = jiffies;
workspace->mem = kvmalloc(workspace->size, GFP_KERNEL);
workspace->buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!workspace->mem || !workspace->buf)
goto fail;
INIT_LIST_HEAD(&workspace->list);
INIT_LIST_HEAD(&workspace->lru_list);
return &workspace->list;
fail:
zstd_free_workspace(&workspace->list);
return ERR_PTR(-ENOMEM);
}
static int zstd_compress_pages(struct list_head *ws,
struct address_space *mapping,
u64 start,
struct page **pages,
unsigned long *out_pages,
unsigned long *total_in,
unsigned long *total_out)
{
struct workspace *workspace = list_entry(ws, struct workspace, list);
ZSTD_CStream *stream;
int ret = 0;
int nr_pages = 0;
struct page *in_page = NULL; /* The current page to read */
struct page *out_page = NULL; /* The current page to write to */
unsigned long tot_in = 0;
unsigned long tot_out = 0;
unsigned long len = *total_out;
const unsigned long nr_dest_pages = *out_pages;
unsigned long max_out = nr_dest_pages * PAGE_SIZE;
ZSTD_parameters params = zstd_get_btrfs_parameters(workspace->req_level,
len);
*out_pages = 0;
*total_out = 0;
*total_in = 0;
/* Initialize the stream */
stream = ZSTD_initCStream(params, len, workspace->mem,
workspace->size);
if (!stream) {
pr_warn("BTRFS: ZSTD_initCStream failed\n");
ret = -EIO;
goto out;
}
/* map in the first page of input data */
in_page = find_get_page(mapping, start >> PAGE_SHIFT);
workspace->in_buf.src = kmap(in_page);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
/* Allocate and map in the output buffer */
out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
if (out_page == NULL) {
ret = -ENOMEM;
goto out;
}
pages[nr_pages++] = out_page;
workspace->out_buf.dst = kmap(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
while (1) {
size_t ret2;
ret2 = ZSTD_compressStream(stream, &workspace->out_buf,
&workspace->in_buf);
if (ZSTD_isError(ret2)) {
pr_debug("BTRFS: ZSTD_compressStream returned %d\n",
ZSTD_getErrorCode(ret2));
ret = -EIO;
goto out;
}
/* Check to see if we are making it bigger */
if (tot_in + workspace->in_buf.pos > 8192 &&
tot_in + workspace->in_buf.pos <
tot_out + workspace->out_buf.pos) {
ret = -E2BIG;
goto out;
}
/* We've reached the end of our output range */
if (workspace->out_buf.pos >= max_out) {
tot_out += workspace->out_buf.pos;
ret = -E2BIG;
goto out;
}
/* Check if we need more output space */
if (workspace->out_buf.pos == workspace->out_buf.size) {
tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
kunmap(out_page);
if (nr_pages == nr_dest_pages) {
out_page = NULL;
ret = -E2BIG;
goto out;
}
out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
if (out_page == NULL) {
ret = -ENOMEM;
goto out;
}
pages[nr_pages++] = out_page;
workspace->out_buf.dst = kmap(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out,
PAGE_SIZE);
}
/* We've reached the end of the input */
if (workspace->in_buf.pos >= len) {
tot_in += workspace->in_buf.pos;
break;
}
/* Check if we need more input */
if (workspace->in_buf.pos == workspace->in_buf.size) {
tot_in += PAGE_SIZE;
kunmap(in_page);
put_page(in_page);
start += PAGE_SIZE;
len -= PAGE_SIZE;
in_page = find_get_page(mapping, start >> PAGE_SHIFT);
workspace->in_buf.src = kmap(in_page);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
}
}
while (1) {
size_t ret2;
ret2 = ZSTD_endStream(stream, &workspace->out_buf);
if (ZSTD_isError(ret2)) {
pr_debug("BTRFS: ZSTD_endStream returned %d\n",
ZSTD_getErrorCode(ret2));
ret = -EIO;
goto out;
}
if (ret2 == 0) {
tot_out += workspace->out_buf.pos;
break;
}
if (workspace->out_buf.pos >= max_out) {
tot_out += workspace->out_buf.pos;
ret = -E2BIG;
goto out;
}
tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
kunmap(out_page);
if (nr_pages == nr_dest_pages) {
out_page = NULL;
ret = -E2BIG;
goto out;
}
out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
if (out_page == NULL) {
ret = -ENOMEM;
goto out;
}
pages[nr_pages++] = out_page;
workspace->out_buf.dst = kmap(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
}
if (tot_out >= tot_in) {
ret = -E2BIG;
goto out;
}
ret = 0;
*total_in = tot_in;
*total_out = tot_out;
out:
*out_pages = nr_pages;
/* Cleanup */
if (in_page) {
kunmap(in_page);
put_page(in_page);
}
if (out_page)
kunmap(out_page);
return ret;
}
static int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
{
struct workspace *workspace = list_entry(ws, struct workspace, list);
struct page **pages_in = cb->compressed_pages;
u64 disk_start = cb->start;
struct bio *orig_bio = cb->orig_bio;
size_t srclen = cb->compressed_len;
ZSTD_DStream *stream;
int ret = 0;
unsigned long page_in_index = 0;
unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
unsigned long buf_start;
unsigned long total_out = 0;
stream = ZSTD_initDStream(
ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
if (!stream) {
pr_debug("BTRFS: ZSTD_initDStream failed\n");
ret = -EIO;
goto done;
}
workspace->in_buf.src = kmap(pages_in[page_in_index]);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
workspace->out_buf.dst = workspace->buf;
workspace->out_buf.pos = 0;
workspace->out_buf.size = PAGE_SIZE;
while (1) {
size_t ret2;
ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
&workspace->in_buf);
if (ZSTD_isError(ret2)) {
pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
ZSTD_getErrorCode(ret2));
ret = -EIO;
goto done;
}
buf_start = total_out;
total_out += workspace->out_buf.pos;
workspace->out_buf.pos = 0;
ret = btrfs_decompress_buf2page(workspace->out_buf.dst,
buf_start, total_out, disk_start, orig_bio);
if (ret == 0)
break;
if (workspace->in_buf.pos >= srclen)
break;
/* Check if we've hit the end of a frame */
if (ret2 == 0)
break;
if (workspace->in_buf.pos == workspace->in_buf.size) {
kunmap(pages_in[page_in_index++]);
if (page_in_index >= total_pages_in) {
workspace->in_buf.src = NULL;
ret = -EIO;
goto done;
}
srclen -= PAGE_SIZE;
workspace->in_buf.src = kmap(pages_in[page_in_index]);
workspace->in_buf.pos = 0;
workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
}
}
ret = 0;
zero_fill_bio(orig_bio);
done:
if (workspace->in_buf.src)
kunmap(pages_in[page_in_index]);
return ret;
}
static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
struct page *dest_page,
unsigned long start_byte,
size_t srclen, size_t destlen)
{
struct workspace *workspace = list_entry(ws, struct workspace, list);
ZSTD_DStream *stream;
int ret = 0;
size_t ret2;
unsigned long total_out = 0;
unsigned long pg_offset = 0;
char *kaddr;
stream = ZSTD_initDStream(
ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
if (!stream) {
pr_warn("BTRFS: ZSTD_initDStream failed\n");
ret = -EIO;
goto finish;
}
destlen = min_t(size_t, destlen, PAGE_SIZE);
workspace->in_buf.src = data_in;
workspace->in_buf.pos = 0;
workspace->in_buf.size = srclen;
workspace->out_buf.dst = workspace->buf;
workspace->out_buf.pos = 0;
workspace->out_buf.size = PAGE_SIZE;
ret2 = 1;
while (pg_offset < destlen
&& workspace->in_buf.pos < workspace->in_buf.size) {
unsigned long buf_start;
unsigned long buf_offset;
unsigned long bytes;
/* Check if the frame is over and we still need more input */
if (ret2 == 0) {
pr_debug("BTRFS: ZSTD_decompressStream ended early\n");
ret = -EIO;
goto finish;
}
ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
&workspace->in_buf);
if (ZSTD_isError(ret2)) {
pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
ZSTD_getErrorCode(ret2));
ret = -EIO;
goto finish;
}
buf_start = total_out;
total_out += workspace->out_buf.pos;
workspace->out_buf.pos = 0;
if (total_out <= start_byte)
continue;
if (total_out > start_byte && buf_start < start_byte)
buf_offset = start_byte - buf_start;
else
buf_offset = 0;
bytes = min_t(unsigned long, destlen - pg_offset,
workspace->out_buf.size - buf_offset);
kaddr = kmap_atomic(dest_page);
memcpy(kaddr + pg_offset, workspace->out_buf.dst + buf_offset,
bytes);
kunmap_atomic(kaddr);
pg_offset += bytes;
}
ret = 0;
finish:
if (pg_offset < destlen) {
kaddr = kmap_atomic(dest_page);
memset(kaddr + pg_offset, 0, destlen - pg_offset);
kunmap_atomic(kaddr);
}
return ret;
}
static unsigned int zstd_set_level(unsigned int level)
{
if (!level)
return ZSTD_BTRFS_DEFAULT_LEVEL;
return min_t(unsigned int, level, ZSTD_BTRFS_MAX_LEVEL);
}
const struct btrfs_compress_op btrfs_zstd_compress = {
.init_workspace_manager = zstd_init_workspace_manager,
.cleanup_workspace_manager = zstd_cleanup_workspace_manager,
.get_workspace = zstd_get_workspace,
.put_workspace = zstd_put_workspace,
.alloc_workspace = zstd_alloc_workspace,
.free_workspace = zstd_free_workspace,
.compress_pages = zstd_compress_pages,
.decompress_bio = zstd_decompress_bio,
.decompress = zstd_decompress,
.set_level = zstd_set_level,
};
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