summaryrefslogtreecommitdiffstats
path: root/fs/squashfs/export.c
blob: 8073b6532cf0473f7cb16d75764b3aa93d985a32 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
/*
 * 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.
 *
 * export.c
 */

/*
 * This file implements code to make Squashfs filesystems exportable (NFS etc.)
 *
 * The export code uses an inode lookup table to map inode numbers passed in
 * filehandles to an inode location on disk.  This table is stored compressed
 * into metadata blocks.  A second index table is used to locate these.  This
 * second index table for speed of access (and because it is small) is read at
 * mount time and cached in memory.
 *
 * The inode lookup table is used only by the export code, inode disk
 * locations are directly encoded in directories, enabling direct access
 * without an intermediate lookup for all operations except the export ops.
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/dcache.h>
#include <linux/exportfs.h>
#include <linux/slab.h>

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

/*
 * Look-up inode number (ino) in table, returning the inode location.
 */
static long long squashfs_inode_lookup(struct super_block *sb, int ino_num)
{
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1);
	int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1);
	u64 start = le64_to_cpu(msblk->inode_lookup_table[blk]);
	__le64 ino;
	int err;

	TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num);

	err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));
	if (err < 0)
		return err;

	TRACE("squashfs_inode_lookup, inode = 0x%llx\n",
		(u64) le64_to_cpu(ino));

	return le64_to_cpu(ino);
}


static struct dentry *squashfs_export_iget(struct super_block *sb,
	unsigned int ino_num)
{
	long long ino;
	struct dentry *dentry = ERR_PTR(-ENOENT);

	TRACE("Entered squashfs_export_iget\n");

	ino = squashfs_inode_lookup(sb, ino_num);
	if (ino >= 0)
		dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num));

	return dentry;
}


static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,
		struct fid *fid, int fh_len, int fh_type)
{
	if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)
			|| fh_len < 2)
		return NULL;

	return squashfs_export_iget(sb, fid->i32.ino);
}


static struct dentry *squashfs_fh_to_parent(struct super_block *sb,
		struct fid *fid, int fh_len, int fh_type)
{
	if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)
		return NULL;

	return squashfs_export_iget(sb, fid->i32.parent_ino);
}


static struct dentry *squashfs_get_parent(struct dentry *child)
{
	struct inode *inode = d_inode(child);
	unsigned int parent_ino = squashfs_i(inode)->parent;

	return squashfs_export_iget(inode->i_sb, parent_ino);
}


/*
 * Read uncompressed inode lookup table indexes off disk into memory
 */
__le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
		u64 lookup_table_start, u64 next_table, unsigned int inodes)
{
	unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);
	__le64 *table;

	TRACE("In read_inode_lookup_table, length %d\n", length);

	/* Sanity check values */

	/* there should always be at least one inode */
	if (inodes == 0)
		return ERR_PTR(-EINVAL);

	/* length bytes should not extend into the next table - this check
	 * also traps instances where lookup_table_start is incorrectly larger
	 * than the next table start
	 */
	if (lookup_table_start + length > next_table)
		return ERR_PTR(-EINVAL);

	table = squashfs_read_table(sb, lookup_table_start, length);

	/*
	 * table[0] points to the first inode lookup table metadata block,
	 * this should be less than lookup_table_start
	 */
	if (!IS_ERR(table) && le64_to_cpu(table[0]) >= lookup_table_start) {
		kfree(table);
		return ERR_PTR(-EINVAL);
	}

	return table;
}


const struct export_operations squashfs_export_ops = {
	.fh_to_dentry = squashfs_fh_to_dentry,
	.fh_to_parent = squashfs_fh_to_parent,
	.get_parent = squashfs_get_parent
};
OpenPOWER on IntegriCloud