/*
   * 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.
   */
  
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/init.h>
  #include <linux/err.h>
  #include <linux/sched.h>
  #include <linux/pagemap.h>
  #include <linux/bio.h>
  #include <linux/lzo.h>
  #include "compression.h"
  
  #define LZO_LEN	4
  
  struct workspace {
  	void *mem;
  	void *buf;	/* where decompressed data goes */
  	void *cbuf;	/* where compressed data goes */
  	struct list_head list;
  };
  
  static void lzo_free_workspace(struct list_head *ws)
  {
  	struct workspace *workspace = list_entry(ws, struct workspace, list);
  
  	vfree(workspace->buf);
  	vfree(workspace->cbuf);
  	vfree(workspace->mem);
  	kfree(workspace);
  }
  
  static struct list_head *lzo_alloc_workspace(void)
  {
  	struct workspace *workspace;
  
  	workspace = kzalloc(sizeof(*workspace), GFP_NOFS);
  	if (!workspace)
  		return ERR_PTR(-ENOMEM);
  
  	workspace->mem = vmalloc(LZO1X_MEM_COMPRESS);
  	workspace->buf = vmalloc(lzo1x_worst_compress(PAGE_CACHE_SIZE));
  	workspace->cbuf = vmalloc(lzo1x_worst_compress(PAGE_CACHE_SIZE));
  	if (!workspace->mem || !workspace->buf || !workspace->cbuf)
  		goto fail;
  
  	INIT_LIST_HEAD(&workspace->list);
  
  	return &workspace->list;
  fail:
  	lzo_free_workspace(&workspace->list);
  	return ERR_PTR(-ENOMEM);
  }
  
  static inline void write_compress_length(char *buf, size_t len)
  {
  	__le32 dlen;
  
  	dlen = cpu_to_le32(len);
  	memcpy(buf, &dlen, LZO_LEN);
  }
  
  static inline size_t read_compress_length(char *buf)
  {
  	__le32 dlen;
  
  	memcpy(&dlen, buf, LZO_LEN);
  	return le32_to_cpu(dlen);
  }
  
  static int lzo_compress_pages(struct list_head *ws,
  			      struct address_space *mapping,
  			      u64 start, unsigned long len,
  			      struct page **pages,
  			      unsigned long nr_dest_pages,
  			      unsigned long *out_pages,
  			      unsigned long *total_in,
  			      unsigned long *total_out,
  			      unsigned long max_out)
  {
  	struct workspace *workspace = list_entry(ws, struct workspace, list);
  	int ret = 0;
  	char *data_in;
  	char *cpage_out;
  	int nr_pages = 0;
  	struct page *in_page = NULL;
  	struct page *out_page = NULL;
  	unsigned long bytes_left;
  
  	size_t in_len;
  	size_t out_len;
  	char *buf;
  	unsigned long tot_in = 0;
  	unsigned long tot_out = 0;
  	unsigned long pg_bytes_left;
  	unsigned long out_offset;
  	unsigned long bytes;
  
  	*out_pages = 0;
  	*total_out = 0;
  	*total_in = 0;
  
  	in_page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
  	data_in = kmap(in_page);
  
  	/*
  	 * store the size of all chunks of compressed data in
  	 * the first 4 bytes
  	 */
  	out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
  	if (out_page == NULL) {
  		ret = -ENOMEM;
  		goto out;
  	}
  	cpage_out = kmap(out_page);
  	out_offset = LZO_LEN;
  	tot_out = LZO_LEN;
  	pages[0] = out_page;
  	nr_pages = 1;
  	pg_bytes_left = PAGE_CACHE_SIZE - LZO_LEN;
  
  	/* compress at most one page of data each time */
  	in_len = min(len, PAGE_CACHE_SIZE);
  	while (tot_in < len) {
  		ret = lzo1x_1_compress(data_in, in_len, workspace->cbuf,
  				       &out_len, workspace->mem);
  		if (ret != LZO_E_OK) {
  			printk(KERN_DEBUG "BTRFS: deflate in loop returned %d
  ",
  			       ret);
  			ret = -1;
  			goto out;
  		}
  
  		/* store the size of this chunk of compressed data */
  		write_compress_length(cpage_out + out_offset, out_len);
  		tot_out += LZO_LEN;
  		out_offset += LZO_LEN;
  		pg_bytes_left -= LZO_LEN;
  
  		tot_in += in_len;
  		tot_out += out_len;
  
  		/* copy bytes from the working buffer into the pages */
  		buf = workspace->cbuf;
  		while (out_len) {
  			bytes = min_t(unsigned long, pg_bytes_left, out_len);
  
  			memcpy(cpage_out + out_offset, buf, bytes);
  
  			out_len -= bytes;
  			pg_bytes_left -= bytes;
  			buf += bytes;
  			out_offset += bytes;
  
  			/*
  			 * we need another page for writing out.
  			 *
  			 * Note if there's less than 4 bytes left, we just
  			 * skip to a new page.
  			 */
  			if ((out_len == 0 && pg_bytes_left < LZO_LEN) ||
  			    pg_bytes_left == 0) {
  				if (pg_bytes_left) {
  					memset(cpage_out + out_offset, 0,
  					       pg_bytes_left);
  					tot_out += pg_bytes_left;
  				}
  
  				/* we're done, don't allocate new page */
  				if (out_len == 0 && tot_in >= len)
  					break;
  
  				kunmap(out_page);
  				if (nr_pages == nr_dest_pages) {
  					out_page = NULL;
  					ret = -1;
  					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;
  
  				pg_bytes_left = PAGE_CACHE_SIZE;
  				out_offset = 0;
  			}
  		}
  
  		/* we're making it bigger, give up */
  		if (tot_in > 8192 && tot_in < tot_out) {
  			ret = -1;
  			goto out;
  		}
  
  		/* we're all done */
  		if (tot_in >= len)
  			break;
  
  		if (tot_out > max_out)
  			break;
  
  		bytes_left = len - tot_in;
  		kunmap(in_page);
  		page_cache_release(in_page);
  
  		start += PAGE_CACHE_SIZE;
  		in_page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
  		data_in = kmap(in_page);
  		in_len = min(bytes_left, PAGE_CACHE_SIZE);
  	}
  
  	if (tot_out > tot_in)
  		goto out;
  
  	/* store the size of all chunks of compressed data */
  	cpage_out = kmap(pages[0]);
  	write_compress_length(cpage_out, tot_out);
  
  	kunmap(pages[0]);
  
  	ret = 0;
  	*total_out = tot_out;
  	*total_in = tot_in;
  out:
  	*out_pages = nr_pages;
  	if (out_page)
  		kunmap(out_page);
  
  	if (in_page) {
  		kunmap(in_page);
  		page_cache_release(in_page);
  	}
  
  	return ret;
  }
  
  static int lzo_decompress_biovec(struct list_head *ws,
  				 struct page **pages_in,
  				 u64 disk_start,
  				 struct bio_vec *bvec,
  				 int vcnt,
  				 size_t srclen)
  {
  	struct workspace *workspace = list_entry(ws, struct workspace, list);
  	int ret = 0, ret2;
  	char *data_in;
  	unsigned long page_in_index = 0;
  	unsigned long page_out_index = 0;
  	unsigned long total_pages_in = (srclen + PAGE_CACHE_SIZE - 1) /
  					PAGE_CACHE_SIZE;
  	unsigned long buf_start;
  	unsigned long buf_offset = 0;
  	unsigned long bytes;
  	unsigned long working_bytes;
  	unsigned long pg_offset;
  
  	size_t in_len;
  	size_t out_len;
  	unsigned long in_offset;
  	unsigned long in_page_bytes_left;
  	unsigned long tot_in;
  	unsigned long tot_out;
  	unsigned long tot_len;
  	char *buf;
  	bool may_late_unmap, need_unmap;
  
  	data_in = kmap(pages_in[0]);
  	tot_len = read_compress_length(data_in);
  
  	tot_in = LZO_LEN;
  	in_offset = LZO_LEN;
  	tot_len = min_t(size_t, srclen, tot_len);
  	in_page_bytes_left = PAGE_CACHE_SIZE - LZO_LEN;
  
  	tot_out = 0;
  	pg_offset = 0;
  
  	while (tot_in < tot_len) {
  		in_len = read_compress_length(data_in + in_offset);
  		in_page_bytes_left -= LZO_LEN;
  		in_offset += LZO_LEN;
  		tot_in += LZO_LEN;
  
  		tot_in += in_len;
  		working_bytes = in_len;
  		may_late_unmap = need_unmap = false;
  
  		/* fast path: avoid using the working buffer */
  		if (in_page_bytes_left >= in_len) {
  			buf = data_in + in_offset;
  			bytes = in_len;
  			may_late_unmap = true;
  			goto cont;
  		}
  
  		/* copy bytes from the pages into the working buffer */
  		buf = workspace->cbuf;
  		buf_offset = 0;
  		while (working_bytes) {
  			bytes = min(working_bytes, in_page_bytes_left);
  
  			memcpy(buf + buf_offset, data_in + in_offset, bytes);
  			buf_offset += bytes;
  cont:
  			working_bytes -= bytes;
  			in_page_bytes_left -= bytes;
  			in_offset += bytes;
  
  			/* check if we need to pick another page */
  			if ((working_bytes == 0 && in_page_bytes_left < LZO_LEN)
  			    || in_page_bytes_left == 0) {
  				tot_in += in_page_bytes_left;
  
  				if (working_bytes == 0 && tot_in >= tot_len)
  					break;
  
  				if (page_in_index + 1 >= total_pages_in) {
  					ret = -1;
  					goto done;
  				}
  
  				if (may_late_unmap)
  					need_unmap = true;
  				else
  					kunmap(pages_in[page_in_index]);
  
  				data_in = kmap(pages_in[++page_in_index]);
  
  				in_page_bytes_left = PAGE_CACHE_SIZE;
  				in_offset = 0;
  			}
  		}
  
  		out_len = lzo1x_worst_compress(PAGE_CACHE_SIZE);
  		ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
  					    &out_len);
  		if (need_unmap)
  			kunmap(pages_in[page_in_index - 1]);
  		if (ret != LZO_E_OK) {
  			printk(KERN_WARNING "BTRFS: decompress failed
  ");
  			ret = -1;
  			break;
  		}
  
  		buf_start = tot_out;
  		tot_out += out_len;
  
  		ret2 = btrfs_decompress_buf2page(workspace->buf, buf_start,
  						 tot_out, disk_start,
  						 bvec, vcnt,
  						 &page_out_index, &pg_offset);
  		if (ret2 == 0)
  			break;
  	}
  done:
  	kunmap(pages_in[page_in_index]);
  	return ret;
  }
  
  static int lzo_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);
  	size_t in_len;
  	size_t out_len;
  	size_t tot_len;
  	int ret = 0;
  	char *kaddr;
  	unsigned long bytes;
  
  	BUG_ON(srclen < LZO_LEN);
  
  	tot_len = read_compress_length(data_in);
  	data_in += LZO_LEN;
  
  	in_len = read_compress_length(data_in);
  	data_in += LZO_LEN;
  
  	out_len = PAGE_CACHE_SIZE;
  	ret = lzo1x_decompress_safe(data_in, in_len, workspace->buf, &out_len);
  	if (ret != LZO_E_OK) {
  		printk(KERN_WARNING "BTRFS: decompress failed!
  ");
  		ret = -1;
  		goto out;
  	}
  
  	if (out_len < start_byte) {
  		ret = -1;
  		goto out;
  	}
  
  	bytes = min_t(unsigned long, destlen, out_len - start_byte);
  
  	kaddr = kmap_atomic(dest_page);
  	memcpy(kaddr, workspace->buf + start_byte, bytes);
  	kunmap_atomic(kaddr);
  out:
  	return ret;
  }
  
  struct btrfs_compress_op btrfs_lzo_compress = {
  	.alloc_workspace	= lzo_alloc_workspace,
  	.free_workspace		= lzo_free_workspace,
  	.compress_pages		= lzo_compress_pages,
  	.decompress_biovec	= lzo_decompress_biovec,
  	.decompress		= lzo_decompress,
  };