linuxdebug/fs/btrfs/zstd.c

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2024-07-16 15:50:57 +02:00
// 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,
};