/*
   * Copyright (C) 2008 Oracle.  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.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   *
   * Based on jffs2 zlib code:
   * Copyright © 2001-2007 Red Hat, Inc.
   * Created by David Woodhouse <dwmw2@infradead.org>
   */
  
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/zlib.h>
  #include <linux/zutil.h>

  #include <linux/mm.h>

  #include <linux/init.h>
  #include <linux/err.h>
  #include <linux/sched.h>
  #include <linux/pagemap.h>
  #include <linux/bio.h>

  #include <linux/refcount.h>

  #include "compression.h"

  struct workspace {

  	z_stream strm;

  	char *buf;
  	struct list_head list;
  };

  static void zlib_free_workspace(struct list_head *ws)
  {
  	struct workspace *workspace = list_entry(ws, struct workspace, list);

  	kvfree(workspace->strm.workspace);

  	kfree(workspace->buf);
  	kfree(workspace);
  }
  
  static struct list_head *zlib_alloc_workspace(void)

  {
  	struct workspace *workspace;

  	int workspacesize;

  	workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);

  	if (!workspace)
  		return ERR_PTR(-ENOMEM);

  	workspacesize = max(zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
  			zlib_inflate_workspacesize());

  	workspace->strm.workspace = kvmalloc(workspacesize, GFP_KERNEL);

  	workspace->buf = kmalloc(PAGE_SIZE, GFP_KERNEL);

  	if (!workspace->strm.workspace || !workspace->buf)

  		goto fail;

  	INIT_LIST_HEAD(&workspace->list);

  	return &workspace->list;
  fail:
  	zlib_free_workspace(&workspace->list);
  	return ERR_PTR(-ENOMEM);

  }

  static int zlib_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);

  	int ret;

  	char *data_in;
  	char *cpage_out;
  	int nr_pages = 0;
  	struct page *in_page = NULL;
  	struct page *out_page = NULL;

  	unsigned long bytes_left;

  	unsigned long len = *total_out;

  	unsigned long nr_dest_pages = *out_pages;

  	const unsigned long max_out = nr_dest_pages * PAGE_SIZE;

  
  	*out_pages = 0;
  	*total_out = 0;
  	*total_in = 0;

  	if (Z_OK != zlib_deflateInit(&workspace->strm, 3)) {

  		pr_warn("BTRFS: deflateInit failed
  ");

  		ret = -EIO;

  		goto out;
  	}

  	workspace->strm.total_in = 0;
  	workspace->strm.total_out = 0;

  	in_page = find_get_page(mapping, start >> PAGE_SHIFT);

  	data_in = kmap(in_page);
  
  	out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);

  	if (out_page == NULL) {

  		ret = -ENOMEM;

  		goto out;
  	}

  	cpage_out = kmap(out_page);
  	pages[0] = out_page;
  	nr_pages = 1;

  	workspace->strm.next_in = data_in;
  	workspace->strm.next_out = cpage_out;

  	workspace->strm.avail_out = PAGE_SIZE;
  	workspace->strm.avail_in = min(len, PAGE_SIZE);

  	while (workspace->strm.total_in < len) {
  		ret = zlib_deflate(&workspace->strm, Z_SYNC_FLUSH);

  		if (ret != Z_OK) {

  			pr_debug("BTRFS: deflate in loop returned %d
  ",

  			       ret);

  			zlib_deflateEnd(&workspace->strm);

  			ret = -EIO;

  			goto out;
  		}
  
  		/* we're making it bigger, give up */

  		if (workspace->strm.total_in > 8192 &&
  		    workspace->strm.total_in <
  		    workspace->strm.total_out) {

  			ret = -E2BIG;

  			goto out;
  		}
  		/* we need another page for writing out.  Test this
  		 * before the total_in so we will pull in a new page for
  		 * the stream end if required
  		 */

  		if (workspace->strm.avail_out == 0) {

  			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;
  			}

  			cpage_out = kmap(out_page);
  			pages[nr_pages] = out_page;
  			nr_pages++;

  			workspace->strm.avail_out = PAGE_SIZE;

  			workspace->strm.next_out = cpage_out;

  		}
  		/* we're all done */

  		if (workspace->strm.total_in >= len)

  			break;
  
  		/* we've read in a full page, get a new one */

  		if (workspace->strm.avail_in == 0) {
  			if (workspace->strm.total_out > max_out)

  				break;

  			bytes_left = len - workspace->strm.total_in;

  			kunmap(in_page);

  			put_page(in_page);

  			start += PAGE_SIZE;

  			in_page = find_get_page(mapping,

  						start >> PAGE_SHIFT);

  			data_in = kmap(in_page);

  			workspace->strm.avail_in = min(bytes_left,

  							   PAGE_SIZE);

  			workspace->strm.next_in = data_in;

  		}
  	}

  	workspace->strm.avail_in = 0;
  	ret = zlib_deflate(&workspace->strm, Z_FINISH);
  	zlib_deflateEnd(&workspace->strm);

  
  	if (ret != Z_STREAM_END) {

  		ret = -EIO;

  		goto out;
  	}

  	if (workspace->strm.total_out >= workspace->strm.total_in) {

  		ret = -E2BIG;

  		goto out;
  	}
  
  	ret = 0;

  	*total_out = workspace->strm.total_out;
  	*total_in = workspace->strm.total_in;

  out:
  	*out_pages = nr_pages;
  	if (out_page)
  		kunmap(out_page);
  
  	if (in_page) {
  		kunmap(in_page);

  		put_page(in_page);

  	}

  	return ret;
  }

  static int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)

  {

  	struct workspace *workspace = list_entry(ws, struct workspace, list);

  	int ret = 0, ret2;

  	int wbits = MAX_WBITS;

  	char *data_in;
  	size_t total_out = 0;

  	unsigned long page_in_index = 0;

  	size_t srclen = cb->compressed_len;

  	unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);

  	unsigned long buf_start;

  	struct page **pages_in = cb->compressed_pages;
  	u64 disk_start = cb->start;
  	struct bio *orig_bio = cb->orig_bio;

  	data_in = kmap(pages_in[page_in_index]);

  	workspace->strm.next_in = data_in;

  	workspace->strm.avail_in = min_t(size_t, srclen, PAGE_SIZE);

  	workspace->strm.total_in = 0;

  	workspace->strm.total_out = 0;
  	workspace->strm.next_out = workspace->buf;

  	workspace->strm.avail_out = PAGE_SIZE;

  
  	/* If it's deflate, and it's got no preset dictionary, then
  	   we can tell zlib to skip the adler32 check. */
  	if (srclen > 2 && !(data_in[1] & PRESET_DICT) &&
  	    ((data_in[0] & 0x0f) == Z_DEFLATED) &&
  	    !(((data_in[0]<<8) + data_in[1]) % 31)) {
  
  		wbits = -((data_in[0] >> 4) + 8);

  		workspace->strm.next_in += 2;
  		workspace->strm.avail_in -= 2;

  	}

  	if (Z_OK != zlib_inflateInit2(&workspace->strm, wbits)) {

  		pr_warn("BTRFS: inflateInit failed
  ");

  		kunmap(pages_in[page_in_index]);

  		return -EIO;

  	}

  	while (workspace->strm.total_in < srclen) {
  		ret = zlib_inflate(&workspace->strm, Z_NO_FLUSH);

  		if (ret != Z_OK && ret != Z_STREAM_END)

  			break;

  		buf_start = total_out;

  		total_out = workspace->strm.total_out;

  		/* we didn't make progress in this inflate call, we're done */
  		if (buf_start == total_out)

  			break;

  		ret2 = btrfs_decompress_buf2page(workspace->buf, buf_start,
  						 total_out, disk_start,

  						 orig_bio);

  		if (ret2 == 0) {
  			ret = 0;
  			goto done;

  		}

  		workspace->strm.next_out = workspace->buf;

  		workspace->strm.avail_out = PAGE_SIZE;

  		if (workspace->strm.avail_in == 0) {

  			unsigned long tmp;
  			kunmap(pages_in[page_in_index]);
  			page_in_index++;
  			if (page_in_index >= total_pages_in) {
  				data_in = NULL;
  				break;
  			}
  			data_in = kmap(pages_in[page_in_index]);

  			workspace->strm.next_in = data_in;
  			tmp = srclen - workspace->strm.total_in;
  			workspace->strm.avail_in = min(tmp,

  							   PAGE_SIZE);

  		}
  	}

  	if (ret != Z_STREAM_END)

  		ret = -EIO;

  	else

  		ret = 0;

  done:

  	zlib_inflateEnd(&workspace->strm);

  	if (data_in)
  		kunmap(pages_in[page_in_index]);

  	if (!ret)

  		zero_fill_bio(orig_bio);

  	return ret;
  }

  static int zlib_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);

  	int ret = 0;
  	int wbits = MAX_WBITS;

  	unsigned long bytes_left;

  	unsigned long total_out = 0;

  	unsigned long pg_offset = 0;

  	char *kaddr;

  	destlen = min_t(unsigned long, destlen, PAGE_SIZE);
  	bytes_left = destlen;

  	workspace->strm.next_in = data_in;
  	workspace->strm.avail_in = srclen;
  	workspace->strm.total_in = 0;

  	workspace->strm.next_out = workspace->buf;

  	workspace->strm.avail_out = PAGE_SIZE;

  	workspace->strm.total_out = 0;

  	/* If it's deflate, and it's got no preset dictionary, then
  	   we can tell zlib to skip the adler32 check. */
  	if (srclen > 2 && !(data_in[1] & PRESET_DICT) &&
  	    ((data_in[0] & 0x0f) == Z_DEFLATED) &&
  	    !(((data_in[0]<<8) + data_in[1]) % 31)) {
  
  		wbits = -((data_in[0] >> 4) + 8);

  		workspace->strm.next_in += 2;
  		workspace->strm.avail_in -= 2;

  	}

  	if (Z_OK != zlib_inflateInit2(&workspace->strm, wbits)) {

  		pr_warn("BTRFS: inflateInit failed
  ");

  		return -EIO;

  	}

  	while (bytes_left > 0) {

  		unsigned long buf_start;
  		unsigned long buf_offset;
  		unsigned long bytes;

  		ret = zlib_inflate(&workspace->strm, Z_NO_FLUSH);

  		if (ret != Z_OK && ret != Z_STREAM_END)

  			break;

  
  		buf_start = total_out;

  		total_out = workspace->strm.total_out;

  
  		if (total_out == buf_start) {

  			ret = -EIO;

  			break;
  		}

  		if (total_out <= start_byte)

  			goto next;

  		if (total_out > start_byte && buf_start < start_byte)

  			buf_offset = start_byte - buf_start;

  		else

  			buf_offset = 0;

  		bytes = min(PAGE_SIZE - pg_offset,
  			    PAGE_SIZE - buf_offset);

  		bytes = min(bytes, bytes_left);

  		kaddr = kmap_atomic(dest_page);

  		memcpy(kaddr + pg_offset, workspace->buf + buf_offset, bytes);

  		kunmap_atomic(kaddr);

  
  		pg_offset += bytes;
  		bytes_left -= bytes;
  next:

  		workspace->strm.next_out = workspace->buf;

  		workspace->strm.avail_out = PAGE_SIZE;

  	}

  
  	if (ret != Z_STREAM_END && bytes_left != 0)

  		ret = -EIO;

  	else

  		ret = 0;

  	zlib_inflateEnd(&workspace->strm);

  
  	/*
  	 * this should only happen if zlib returned fewer bytes than we
  	 * expected.  btrfs_get_block is responsible for zeroing from the
  	 * end of the inline extent (destlen) to the end of the page
  	 */
  	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_zlib_compress = {

  	.alloc_workspace	= zlib_alloc_workspace,
  	.free_workspace		= zlib_free_workspace,
  	.compress_pages		= zlib_compress_pages,

  	.decompress_bio		= zlib_decompress_bio,

  	.decompress		= zlib_decompress,
  };