fs/btrfs/zstd.c - third_party/kernel - Git at Google

 // 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_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);
 }

 static void zstd_free_workspace(struct list_head *ws);
 static struct list_head *zstd_alloc_workspace(unsigned int level);

 /*
  * 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_bh(&wsm.lock);

 	if (list_empty(&wsm.lru_list)) {
 		spin_unlock_bh(&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_bh(&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 = 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]);
 	}
 }

 static 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.
  */
 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 = 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.
  */
 static 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);
 }

 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;
 }

 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,
 	.max_level	= ZSTD_BTRFS_MAX_LEVEL,
 	.default_level	= ZSTD_BTRFS_DEFAULT_LEVEL,
 };
	// 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_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);
	}

	static void zstd_free_workspace(struct list_head *ws);
	static struct list_head *zstd_alloc_workspace(unsigned int level);

	/*
	* 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_bh(&wsm.lock);

	if (list_empty(&wsm.lru_list)) {
	spin_unlock_bh(&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_bh(&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 = 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]);
	}
	}

	static 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.
	*/
	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 = 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.
	*/
	static 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);
	}

	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;
	}

	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,
	.max_level = ZSTD_BTRFS_MAX_LEVEL,
	.default_level = ZSTD_BTRFS_DEFAULT_LEVEL,
	};