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-rw-r--r--fs/btrfs/zstd.c703
1 files changed, 703 insertions, 0 deletions
diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
new file mode 100644
index 000000000..35a0224d4
--- /dev/null
+++ b/fs/btrfs/zstd.c
@@ -0,0 +1,703 @@
+// 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 "misc.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_get_params(level, src_len);
+
+ 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_in_buffer in_buf;
+ zstd_out_buffer 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);
+}
+
+void zstd_free_workspace(struct list_head *ws);
+struct list_head *zstd_alloc_workspace(unsigned int level);
+
+/**
+ * Timer callback to free unused workspaces.
+ *
+ * @t: timer
+ *
+ * This scans the lru_list and attempts to reclaim any workspace that hasn't
+ * been used for ZSTD_BTRFS_RECLAIM_JIFFIES.
+ *
+ * The context is softirq and does not need the _bh locking primitives.
+ */
+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);
+ zstd_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_cstream_workspace_bound(&params.cParams),
+ zstd_dstream_workspace_bound(ZSTD_BTRFS_MAX_INPUT));
+
+ max_size = max_t(size_t, max_size, level_size);
+ zstd_ws_mem_sizes[level - 1] = max_size;
+ }
+}
+
+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 = zstd_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]);
+ }
+}
+
+void zstd_cleanup_workspace_manager(void)
+{
+ struct workspace *workspace;
+ int i;
+
+ spin_lock_bh(&wsm.lock);
+ 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);
+ zstd_free_workspace(&workspace->list);
+ }
+ }
+ spin_unlock_bh(&wsm.lock);
+
+ del_timer_sync(&wsm.timer);
+}
+
+/*
+ * 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_bh(&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_bh(&wsm.lock);
+ return ws;
+ }
+ }
+ spin_unlock_bh(&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.
+ */
+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 = zstd_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.
+ */
+void zstd_put_workspace(struct list_head *ws)
+{
+ struct workspace *workspace = list_to_workspace(ws);
+
+ spin_lock_bh(&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_bh(&wsm.lock);
+
+ if (workspace->level == ZSTD_BTRFS_MAX_LEVEL)
+ cond_wake_up(&wsm.wait);
+}
+
+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);
+}
+
+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);
+}
+
+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_init_cstream(&params, len, workspace->mem,
+ workspace->size);
+ if (!stream) {
+ pr_warn("BTRFS: zstd_init_cstream 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_local_page(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);
+ if (out_page == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ pages[nr_pages++] = out_page;
+ workspace->out_buf.dst = page_address(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_compress_stream(stream, &workspace->out_buf,
+ &workspace->in_buf);
+ if (zstd_is_error(ret2)) {
+ pr_debug("BTRFS: zstd_compress_stream returned %d\n",
+ zstd_get_error_code(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;
+ if (nr_pages == nr_dest_pages) {
+ ret = -E2BIG;
+ goto out;
+ }
+ out_page = alloc_page(GFP_NOFS);
+ if (out_page == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ pages[nr_pages++] = out_page;
+ workspace->out_buf.dst = page_address(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_local(workspace->in_buf.src);
+ put_page(in_page);
+ start += PAGE_SIZE;
+ len -= PAGE_SIZE;
+ in_page = find_get_page(mapping, start >> PAGE_SHIFT);
+ workspace->in_buf.src = kmap_local_page(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_end_stream(stream, &workspace->out_buf);
+ if (zstd_is_error(ret2)) {
+ pr_debug("BTRFS: zstd_end_stream returned %d\n",
+ zstd_get_error_code(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;
+ if (nr_pages == nr_dest_pages) {
+ ret = -E2BIG;
+ goto out;
+ }
+ out_page = alloc_page(GFP_NOFS);
+ if (out_page == NULL) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ pages[nr_pages++] = out_page;
+ workspace->out_buf.dst = page_address(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;
+ if (workspace->in_buf.src) {
+ kunmap_local(workspace->in_buf.src);
+ put_page(in_page);
+ }
+ return ret;
+}
+
+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;
+ 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_init_dstream(
+ ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
+ if (!stream) {
+ pr_debug("BTRFS: zstd_init_dstream failed\n");
+ ret = -EIO;
+ goto done;
+ }
+
+ workspace->in_buf.src = kmap_local_page(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_decompress_stream(stream, &workspace->out_buf,
+ &workspace->in_buf);
+ if (zstd_is_error(ret2)) {
+ pr_debug("BTRFS: zstd_decompress_stream returned %d\n",
+ zstd_get_error_code(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,
+ total_out - buf_start, cb, buf_start);
+ 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_local(workspace->in_buf.src);
+ 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_local_page(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(cb->orig_bio);
+done:
+ if (workspace->in_buf.src)
+ kunmap_local(workspace->in_buf.src);
+ return ret;
+}
+
+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;
+
+ stream = zstd_init_dstream(
+ ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
+ if (!stream) {
+ pr_warn("BTRFS: zstd_init_dstream 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_decompress_stream ended early\n");
+ ret = -EIO;
+ goto finish;
+ }
+ ret2 = zstd_decompress_stream(stream, &workspace->out_buf,
+ &workspace->in_buf);
+ if (zstd_is_error(ret2)) {
+ pr_debug("BTRFS: zstd_decompress_stream returned %d\n",
+ zstd_get_error_code(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);
+
+ memcpy_to_page(dest_page, pg_offset,
+ workspace->out_buf.dst + buf_offset, bytes);
+
+ pg_offset += bytes;
+ }
+ ret = 0;
+finish:
+ if (pg_offset < destlen) {
+ memzero_page(dest_page, pg_offset, destlen - pg_offset);
+ }
+ return ret;
+}
+
+const struct btrfs_compress_op btrfs_zstd_compress = {
+ /* ZSTD uses own workspace manager */
+ .workspace_manager = NULL,
+ .max_level = ZSTD_BTRFS_MAX_LEVEL,
+ .default_level = ZSTD_BTRFS_DEFAULT_LEVEL,
+};