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12260140 PL |
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@lougher.demon.co.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 | * export.c | |
22 | */ | |
23 | ||
24 | /* | |
25 | * This file implements code to make Squashfs filesystems exportable (NFS etc.) | |
26 | * | |
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. | |
32 | * | |
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. | |
36 | */ | |
37 | ||
38 | #include <linux/fs.h> | |
39 | #include <linux/vfs.h> | |
40 | #include <linux/dcache.h> | |
41 | #include <linux/exportfs.h> | |
42 | #include <linux/zlib.h> | |
23516dc7 | 43 | #include <linux/slab.h> |
12260140 PL |
44 | |
45 | #include "squashfs_fs.h" | |
46 | #include "squashfs_fs_sb.h" | |
47 | #include "squashfs_fs_i.h" | |
48 | #include "squashfs.h" | |
49 | ||
50 | /* | |
51 | * Look-up inode number (ino) in table, returning the inode location. | |
52 | */ | |
53 | static long long squashfs_inode_lookup(struct super_block *sb, int ino_num) | |
54 | { | |
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]); | |
59 | __le64 ino; | |
60 | int err; | |
61 | ||
62 | TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); | |
63 | ||
64 | err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino)); | |
65 | if (err < 0) | |
66 | return err; | |
67 | ||
68 | TRACE("squashfs_inode_lookup, inode = 0x%llx\n", | |
69 | (u64) le64_to_cpu(ino)); | |
70 | ||
71 | return le64_to_cpu(ino); | |
72 | } | |
73 | ||
74 | ||
75 | static struct dentry *squashfs_export_iget(struct super_block *sb, | |
76 | unsigned int ino_num) | |
77 | { | |
78 | long long ino; | |
79 | struct dentry *dentry = ERR_PTR(-ENOENT); | |
80 | ||
81 | TRACE("Entered squashfs_export_iget\n"); | |
82 | ||
83 | ino = squashfs_inode_lookup(sb, ino_num); | |
84 | if (ino >= 0) | |
85 | dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); | |
86 | ||
87 | return dentry; | |
88 | } | |
89 | ||
90 | ||
91 | static struct dentry *squashfs_fh_to_dentry(struct super_block *sb, | |
92 | struct fid *fid, int fh_len, int fh_type) | |
93 | { | |
94 | if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT) | |
95 | || fh_len < 2) | |
96 | return NULL; | |
97 | ||
98 | return squashfs_export_iget(sb, fid->i32.ino); | |
99 | } | |
100 | ||
101 | ||
102 | static struct dentry *squashfs_fh_to_parent(struct super_block *sb, | |
103 | struct fid *fid, int fh_len, int fh_type) | |
104 | { | |
105 | if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4) | |
106 | return NULL; | |
107 | ||
108 | return squashfs_export_iget(sb, fid->i32.parent_ino); | |
109 | } | |
110 | ||
111 | ||
112 | static struct dentry *squashfs_get_parent(struct dentry *child) | |
113 | { | |
114 | struct inode *inode = child->d_inode; | |
115 | unsigned int parent_ino = squashfs_i(inode)->parent; | |
116 | ||
117 | return squashfs_export_iget(inode->i_sb, parent_ino); | |
118 | } | |
119 | ||
120 | ||
121 | /* | |
122 | * Read uncompressed inode lookup table indexes off disk into memory | |
123 | */ | |
124 | __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, | |
125 | u64 lookup_table_start, unsigned int inodes) | |
126 | { | |
127 | unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); | |
128 | __le64 *inode_lookup_table; | |
129 | int err; | |
130 | ||
131 | TRACE("In read_inode_lookup_table, length %d\n", length); | |
132 | ||
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); | |
138 | } | |
139 | ||
140 | err = squashfs_read_table(sb, inode_lookup_table, lookup_table_start, | |
141 | length); | |
142 | if (err < 0) { | |
143 | ERROR("unable to read inode lookup table\n"); | |
144 | kfree(inode_lookup_table); | |
145 | return ERR_PTR(err); | |
146 | } | |
147 | ||
148 | return inode_lookup_table; | |
149 | } | |
150 | ||
151 | ||
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 | |
156 | }; |