1/*
2 * Squashfs - a compressed read only filesystem for Linux
3 *
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@squashfs.org.uk>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2,
10 * or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 *
21 * symlink.c
22 */
23
24/*
25 * This file implements code to handle symbolic links.
26 *
27 * The data contents of symbolic links are stored inside the symbolic
28 * link inode within the inode table.  This allows the normally small symbolic
29 * link to be compressed as part of the inode table, achieving much greater
30 * compression than if the symbolic link was compressed individually.
31 */
32
33#include <linux/fs.h>
34#include <linux/vfs.h>
35#include <linux/kernel.h>
36#include <linux/string.h>
37#include <linux/pagemap.h>
38#include <linux/xattr.h>
39
40#include "squashfs_fs.h"
41#include "squashfs_fs_sb.h"
42#include "squashfs_fs_i.h"
43#include "squashfs.h"
44#include "xattr.h"
45
46static int squashfs_symlink_readpage(struct file *file, struct page *page)
47{
48	struct inode *inode = page->mapping->host;
49	struct super_block *sb = inode->i_sb;
50	struct squashfs_sb_info *msblk = sb->s_fs_info;
51	int index = page->index << PAGE_CACHE_SHIFT;
52	u64 block = squashfs_i(inode)->start;
53	int offset = squashfs_i(inode)->offset;
54	int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE);
55	int bytes, copied;
56	void *pageaddr;
57	struct squashfs_cache_entry *entry;
58
59	TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
60			"%llx, offset %x\n", page->index, block, offset);
61
62	/*
63	 * Skip index bytes into symlink metadata.
64	 */
65	if (index) {
66		bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
67								index);
68		if (bytes < 0) {
69			ERROR("Unable to read symlink [%llx:%x]\n",
70				squashfs_i(inode)->start,
71				squashfs_i(inode)->offset);
72			goto error_out;
73		}
74	}
75
76	/*
77	 * Read length bytes from symlink metadata.  Squashfs_read_metadata
78	 * is not used here because it can sleep and we want to use
79	 * kmap_atomic to map the page.  Instead call the underlying
80	 * squashfs_cache_get routine.  As length bytes may overlap metadata
81	 * blocks, we may need to call squashfs_cache_get multiple times.
82	 */
83	for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
84		entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
85		if (entry->error) {
86			ERROR("Unable to read symlink [%llx:%x]\n",
87				squashfs_i(inode)->start,
88				squashfs_i(inode)->offset);
89			squashfs_cache_put(entry);
90			goto error_out;
91		}
92
93		pageaddr = kmap_atomic(page);
94		copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
95								length - bytes);
96		if (copied == length - bytes)
97			memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length);
98		else
99			block = entry->next_index;
100		kunmap_atomic(pageaddr);
101		squashfs_cache_put(entry);
102	}
103
104	flush_dcache_page(page);
105	SetPageUptodate(page);
106	unlock_page(page);
107	return 0;
108
109error_out:
110	SetPageError(page);
111	unlock_page(page);
112	return 0;
113}
114
115
116const struct address_space_operations squashfs_symlink_aops = {
117	.readpage = squashfs_symlink_readpage
118};
119
120const struct inode_operations squashfs_symlink_inode_ops = {
121	.readlink = generic_readlink,
122	.follow_link = page_follow_link_light,
123	.put_link = page_put_link,
124	.getxattr = generic_getxattr,
125	.listxattr = squashfs_listxattr
126};
127
128