/*
 * Copyright (c) 2016-present, Facebook, Inc.
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */
#include <linux/bio.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/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"

#define ZSTD_BTRFS_MAX_WINDOWLOG 17
#define ZSTD_BTRFS_MAX_INPUT (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
#define ZSTD_BTRFS_DEFAULT_LEVEL 3

static ZSTD_parameters zstd_get_btrfs_parameters(size_t src_len)
{
	ZSTD_parameters params = ZSTD_getParams(ZSTD_BTRFS_DEFAULT_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;
	struct list_head list;
};

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(void)
{
	ZSTD_parameters params =
			zstd_get_btrfs_parameters(ZSTD_BTRFS_MAX_INPUT);
	struct workspace *workspace;

	workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);
	if (!workspace)
		return ERR_PTR(-ENOMEM);

	workspace->size = max_t(size_t,
			ZSTD_CStreamWorkspaceBound(params.cParams),
			ZSTD_DStreamWorkspaceBound(ZSTD_BTRFS_MAX_INPUT));
	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);

	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 */
	ZSTD_inBuffer in_buf = { NULL, 0, 0 };
	ZSTD_outBuffer out_buf = { NULL, 0, 0 };
	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(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);
	in_buf.src = kmap(in_page);
	in_buf.pos = 0;
	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;
	out_buf.dst = kmap(out_page);
	out_buf.pos = 0;
	out_buf.size = min_t(size_t, max_out, PAGE_SIZE);

	while (1) {
		size_t ret2;

		ret2 = ZSTD_compressStream(stream, &out_buf, &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 + in_buf.pos > 8192 &&
				tot_in + in_buf.pos <
				tot_out + out_buf.pos) {
			ret = -E2BIG;
			goto out;
		}

		/* We've reached the end of our output range */
		if (out_buf.pos >= max_out) {
			tot_out += out_buf.pos;
			ret = -E2BIG;
			goto out;
		}

		/* Check if we need more output space */
		if (out_buf.pos == 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;
			out_buf.dst = kmap(out_page);
			out_buf.pos = 0;
			out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
		}

		/* We've reached the end of the input */
		if (in_buf.pos >= len) {
			tot_in += in_buf.pos;
			break;
		}

		/* Check if we need more input */
		if (in_buf.pos == 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);
			in_buf.src = kmap(in_page);
			in_buf.pos = 0;
			in_buf.size = min_t(size_t, len, PAGE_SIZE);
		}
	}
	while (1) {
		size_t ret2;

		ret2 = ZSTD_endStream(stream, &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 += out_buf.pos;
			break;
		}
		if (out_buf.pos >= max_out) {
			tot_out += 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;
		out_buf.dst = kmap(out_page);
		out_buf.pos = 0;
		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;
	ZSTD_inBuffer in_buf = { NULL, 0, 0 };
	ZSTD_outBuffer out_buf = { NULL, 0, 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;
	}

	in_buf.src = kmap(pages_in[page_in_index]);
	in_buf.pos = 0;
	in_buf.size = min_t(size_t, srclen, PAGE_SIZE);

	out_buf.dst = workspace->buf;
	out_buf.pos = 0;
	out_buf.size = PAGE_SIZE;

	while (1) {
		size_t ret2;

		ret2 = ZSTD_decompressStream(stream, &out_buf, &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 += out_buf.pos;
		out_buf.pos = 0;

		ret = btrfs_decompress_buf2page(out_buf.dst, buf_start,
				total_out, disk_start, orig_bio);
		if (ret == 0)
			break;

		if (in_buf.pos >= srclen)
			break;

		/* Check if we've hit the end of a frame */
		if (ret2 == 0)
			break;

		if (in_buf.pos == in_buf.size) {
			kunmap(pages_in[page_in_index++]);
			if (page_in_index >= total_pages_in) {
				in_buf.src = NULL;
				ret = -EIO;
				goto done;
			}
			srclen -= PAGE_SIZE;
			in_buf.src = kmap(pages_in[page_in_index]);
			in_buf.pos = 0;
			in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
		}
	}
	ret = 0;
	zero_fill_bio(orig_bio);
done:
	if (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;
	ZSTD_inBuffer in_buf = { NULL, 0, 0 };
	ZSTD_outBuffer out_buf = { NULL, 0, 0 };
	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);

	in_buf.src = data_in;
	in_buf.pos = 0;
	in_buf.size = srclen;

	out_buf.dst = workspace->buf;
	out_buf.pos = 0;
	out_buf.size = PAGE_SIZE;

	ret2 = 1;
	while (pg_offset < destlen && in_buf.pos < 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, &out_buf, &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 += out_buf.pos;
		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,
				out_buf.size - buf_offset);

		kaddr = kmap_atomic(dest_page);
		memcpy(kaddr + pg_offset, 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 = {
	.alloc_workspace = zstd_alloc_workspace,
	.free_workspace = zstd_free_workspace,
	.compress_pages = zstd_compress_pages,
	.decompress_bio = zstd_decompress_bio,
	.decompress = zstd_decompress,
};