/*
   * Squashfs - a compressed read only filesystem for Linux
   *
   * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008

   * Phillip Lougher <phillip@squashfs.org.uk>

   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version 2,
   * or (at your option) any later version.
   *
   * 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, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   *
   * symlink.c
   */
  
  /*
   * This file implements code to handle symbolic links.
   *
   * The data contents of symbolic links are stored inside the symbolic
   * link inode within the inode table.  This allows the normally small symbolic
   * link to be compressed as part of the inode table, achieving much greater
   * compression than if the symbolic link was compressed individually.
   */
  
  #include <linux/fs.h>
  #include <linux/vfs.h>
  #include <linux/kernel.h>

  #include <linux/string.h>
  #include <linux/pagemap.h>

  #include <linux/xattr.h>

  
  #include "squashfs_fs.h"
  #include "squashfs_fs_sb.h"
  #include "squashfs_fs_i.h"
  #include "squashfs.h"

  #include "xattr.h"

  
  static int squashfs_symlink_readpage(struct file *file, struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	struct super_block *sb = inode->i_sb;
  	struct squashfs_sb_info *msblk = sb->s_fs_info;
  	int index = page->index << PAGE_CACHE_SHIFT;
  	u64 block = squashfs_i(inode)->start;
  	int offset = squashfs_i(inode)->offset;
  	int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE);
  	int bytes, copied;
  	void *pageaddr;
  	struct squashfs_cache_entry *entry;
  
  	TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
  			"%llx, offset %x
  ", page->index, block, offset);
  
  	/*
  	 * Skip index bytes into symlink metadata.
  	 */
  	if (index) {
  		bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
  								index);
  		if (bytes < 0) {
  			ERROR("Unable to read symlink [%llx:%x]
  ",
  				squashfs_i(inode)->start,
  				squashfs_i(inode)->offset);
  			goto error_out;
  		}
  	}
  
  	/*
  	 * Read length bytes from symlink metadata.  Squashfs_read_metadata
  	 * is not used here because it can sleep and we want to use
  	 * kmap_atomic to map the page.  Instead call the underlying
  	 * squashfs_cache_get routine.  As length bytes may overlap metadata
  	 * blocks, we may need to call squashfs_cache_get multiple times.
  	 */
  	for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
  		entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
  		if (entry->error) {
  			ERROR("Unable to read symlink [%llx:%x]
  ",
  				squashfs_i(inode)->start,
  				squashfs_i(inode)->offset);
  			squashfs_cache_put(entry);
  			goto error_out;
  		}
  
  		pageaddr = kmap_atomic(page, KM_USER0);
  		copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
  								length - bytes);
  		if (copied == length - bytes)
  			memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length);
  		else
  			block = entry->next_index;
  		kunmap_atomic(pageaddr, KM_USER0);
  		squashfs_cache_put(entry);
  	}
  
  	flush_dcache_page(page);
  	SetPageUptodate(page);
  	unlock_page(page);
  	return 0;
  
  error_out:
  	SetPageError(page);
  	unlock_page(page);
  	return 0;
  }
  
  
  const struct address_space_operations squashfs_symlink_aops = {
  	.readpage = squashfs_symlink_readpage
  };

  
  const struct inode_operations squashfs_symlink_inode_ops = {
  	.readlink = generic_readlink,
  	.follow_link = page_follow_link_light,
  	.put_link = page_put_link,
  	.getxattr = generic_getxattr,
  	.listxattr = squashfs_listxattr
  };