2 * Squashfs - a compressed read only filesystem for Linux
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@lougher.demon.co.uk>
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.
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.
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.
25 * This file implements code to make Squashfs filesystems exportable (NFS etc.)
27 * The export code uses an inode lookup table to map inode numbers passed in
28 * filehandles to an inode location on disk. This table is stored compressed
29 * into metadata blocks. A second index table is used to locate these. This
30 * second index table for speed of access (and because it is small) is read at
31 * mount time and cached in memory.
33 * The inode lookup table is used only by the export code, inode disk
34 * locations are directly encoded in directories, enabling direct access
35 * without an intermediate lookup for all operations except the export ops.
39 #include <linux/vfs.h>
40 #include <linux/dcache.h>
41 #include <linux/exportfs.h>
42 #include <linux/zlib.h>
43 #include <linux/slab.h>
45 #include "squashfs_fs.h"
46 #include "squashfs_fs_sb.h"
47 #include "squashfs_fs_i.h"
51 * Look-up inode number (ino) in table, returning the inode location.
53 static long long squashfs_inode_lookup(struct super_block *sb, int ino_num)
55 struct squashfs_sb_info *msblk = sb->s_fs_info;
56 int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1);
57 int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1);
58 u64 start = le64_to_cpu(msblk->inode_lookup_table[blk]);
62 TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num);
64 err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));
68 TRACE("squashfs_inode_lookup, inode = 0x%llx\n",
69 (u64) le64_to_cpu(ino));
71 return le64_to_cpu(ino);
75 static struct dentry *squashfs_export_iget(struct super_block *sb,
79 struct dentry *dentry = ERR_PTR(-ENOENT);
81 TRACE("Entered squashfs_export_iget\n");
83 ino = squashfs_inode_lookup(sb, ino_num);
85 dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num));
91 static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,
92 struct fid *fid, int fh_len, int fh_type)
94 if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)
98 return squashfs_export_iget(sb, fid->i32.ino);
102 static struct dentry *squashfs_fh_to_parent(struct super_block *sb,
103 struct fid *fid, int fh_len, int fh_type)
105 if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)
108 return squashfs_export_iget(sb, fid->i32.parent_ino);
112 static struct dentry *squashfs_get_parent(struct dentry *child)
114 struct inode *inode = child->d_inode;
115 unsigned int parent_ino = squashfs_i(inode)->parent;
117 return squashfs_export_iget(inode->i_sb, parent_ino);
122 * Read uncompressed inode lookup table indexes off disk into memory
124 __le64 *squashfs_read_inode_lookup_table(struct super_block *sb,
125 u64 lookup_table_start, unsigned int inodes)
127 unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);
128 __le64 *inode_lookup_table;
131 TRACE("In read_inode_lookup_table, length %d\n", length);
133 /* Allocate inode lookup table indexes */
134 inode_lookup_table = kmalloc(length, GFP_KERNEL);
135 if (inode_lookup_table == NULL) {
136 ERROR("Failed to allocate inode lookup table\n");
137 return ERR_PTR(-ENOMEM);
140 err = squashfs_read_table(sb, inode_lookup_table, lookup_table_start,
143 ERROR("unable to read inode lookup table\n");
144 kfree(inode_lookup_table);
148 return inode_lookup_table;
152 const struct export_operations squashfs_export_ops = {
153 .fh_to_dentry = squashfs_fh_to_dentry,
154 .fh_to_parent = squashfs_fh_to_parent,
155 .get_parent = squashfs_get_parent