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-rw-r--r--fs/squashfs/namei.c242
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diff --git a/fs/squashfs/namei.c b/fs/squashfs/namei.c
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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 * namei.c
22 */
23
24/*
25 * This file implements code to do filename lookup in directories.
26 *
27 * Like inodes, directories are packed into compressed metadata blocks, stored
28 * in a directory table. Directories are accessed using the start address of
29 * the metablock containing the directory and the offset into the
30 * decompressed block (<block, offset>).
31 *
32 * Directories are organised in a slightly complex way, and are not simply
33 * a list of file names. The organisation takes advantage of the
34 * fact that (in most cases) the inodes of the files will be in the same
35 * compressed metadata block, and therefore, can share the start block.
36 * Directories are therefore organised in a two level list, a directory
37 * header containing the shared start block value, and a sequence of directory
38 * entries, each of which share the shared start block. A new directory header
39 * is written once/if the inode start block changes. The directory
40 * header/directory entry list is repeated as many times as necessary.
41 *
42 * Directories are sorted, and can contain a directory index to speed up
43 * file lookup. Directory indexes store one entry per metablock, each entry
44 * storing the index/filename mapping to the first directory header
45 * in each metadata block. Directories are sorted in alphabetical order,
46 * and at lookup the index is scanned linearly looking for the first filename
47 * alphabetically larger than the filename being looked up. At this point the
48 * location of the metadata block the filename is in has been found.
49 * The general idea of the index is ensure only one metadata block needs to be
50 * decompressed to do a lookup irrespective of the length of the directory.
51 * This scheme has the advantage that it doesn't require extra memory overhead
52 * and doesn't require much extra storage on disk.
53 */
54
55#include <linux/fs.h>
56#include <linux/vfs.h>
57#include <linux/slab.h>
58#include <linux/string.h>
59#include <linux/dcache.h>
60#include <linux/zlib.h>
61
62#include "squashfs_fs.h"
63#include "squashfs_fs_sb.h"
64#include "squashfs_fs_i.h"
65#include "squashfs.h"
66
67/*
68 * Lookup name in the directory index, returning the location of the metadata
69 * block containing it, and the directory index this represents.
70 *
71 * If we get an error reading the index then return the part of the index
72 * (if any) we have managed to read - the index isn't essential, just
73 * quicker.
74 */
75static int get_dir_index_using_name(struct super_block *sb,
76 u64 *next_block, int *next_offset, u64 index_start,
77 int index_offset, int i_count, const char *name,
78 int len)
79{
80 struct squashfs_sb_info *msblk = sb->s_fs_info;
81 int i, size, length = 0, err;
82 struct squashfs_dir_index *index;
83 char *str;
84
85 TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count);
86
87 index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL);
88 if (index == NULL) {
89 ERROR("Failed to allocate squashfs_dir_index\n");
90 goto out;
91 }
92
93 str = &index->name[SQUASHFS_NAME_LEN + 1];
94 strncpy(str, name, len);
95 str[len] = '\0';
96
97 for (i = 0; i < i_count; i++) {
98 err = squashfs_read_metadata(sb, index, &index_start,
99 &index_offset, sizeof(*index));
100 if (err < 0)
101 break;
102
103
104 size = le32_to_cpu(index->size) + 1;
105
106 err = squashfs_read_metadata(sb, index->name, &index_start,
107 &index_offset, size);
108 if (err < 0)
109 break;
110
111 index->name[size] = '\0';
112
113 if (strcmp(index->name, str) > 0)
114 break;
115
116 length = le32_to_cpu(index->index);
117 *next_block = le32_to_cpu(index->start_block) +
118 msblk->directory_table;
119 }
120
121 *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
122 kfree(index);
123
124out:
125 /*
126 * Return index (f_pos) of the looked up metadata block. Translate
127 * from internal f_pos to external f_pos which is offset by 3 because
128 * we invent "." and ".." entries which are not actually stored in the
129 * directory.
130 */
131 return length + 3;
132}
133
134
135static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry,
136 struct nameidata *nd)
137{
138 const unsigned char *name = dentry->d_name.name;
139 int len = dentry->d_name.len;
140 struct inode *inode = NULL;
141 struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
142 struct squashfs_dir_header dirh;
143 struct squashfs_dir_entry *dire;
144 u64 block = squashfs_i(dir)->start + msblk->directory_table;
145 int offset = squashfs_i(dir)->offset;
146 int err, length = 0, dir_count, size;
147
148 TRACE("Entered squashfs_lookup [%llx:%x]\n", block, offset);
149
150 dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
151 if (dire == NULL) {
152 ERROR("Failed to allocate squashfs_dir_entry\n");
153 return ERR_PTR(-ENOMEM);
154 }
155
156 if (len > SQUASHFS_NAME_LEN) {
157 err = -ENAMETOOLONG;
158 goto failed;
159 }
160
161 length = get_dir_index_using_name(dir->i_sb, &block, &offset,
162 squashfs_i(dir)->dir_idx_start,
163 squashfs_i(dir)->dir_idx_offset,
164 squashfs_i(dir)->dir_idx_cnt, name, len);
165
166 while (length < i_size_read(dir)) {
167 /*
168 * Read directory header.
169 */
170 err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
171 &offset, sizeof(dirh));
172 if (err < 0)
173 goto read_failure;
174
175 length += sizeof(dirh);
176
177 dir_count = le32_to_cpu(dirh.count) + 1;
178 while (dir_count--) {
179 /*
180 * Read directory entry.
181 */
182 err = squashfs_read_metadata(dir->i_sb, dire, &block,
183 &offset, sizeof(*dire));
184 if (err < 0)
185 goto read_failure;
186
187 size = le16_to_cpu(dire->size) + 1;
188
189 err = squashfs_read_metadata(dir->i_sb, dire->name,
190 &block, &offset, size);
191 if (err < 0)
192 goto read_failure;
193
194 length += sizeof(*dire) + size;
195
196 if (name[0] < dire->name[0])
197 goto exit_lookup;
198
199 if (len == size && !strncmp(name, dire->name, len)) {
200 unsigned int blk, off, ino_num;
201 long long ino;
202 blk = le32_to_cpu(dirh.start_block);
203 off = le16_to_cpu(dire->offset);
204 ino_num = le32_to_cpu(dirh.inode_number) +
205 (short) le16_to_cpu(dire->inode_number);
206 ino = SQUASHFS_MKINODE(blk, off);
207
208 TRACE("calling squashfs_iget for directory "
209 "entry %s, inode %x:%x, %d\n", name,
210 blk, off, ino_num);
211
212 inode = squashfs_iget(dir->i_sb, ino, ino_num);
213 if (IS_ERR(inode)) {
214 err = PTR_ERR(inode);
215 goto failed;
216 }
217
218 goto exit_lookup;
219 }
220 }
221 }
222
223exit_lookup:
224 kfree(dire);
225 if (inode)
226 return d_splice_alias(inode, dentry);
227 d_add(dentry, inode);
228 return ERR_PTR(0);
229
230read_failure:
231 ERROR("Unable to read directory block [%llx:%x]\n",
232 squashfs_i(dir)->start + msblk->directory_table,
233 squashfs_i(dir)->offset);
234failed:
235 kfree(dire);
236 return ERR_PTR(err);
237}
238
239
240const struct inode_operations squashfs_dir_inode_ops = {
241 .lookup = squashfs_lookup
242};
generated by cgit v1.2.2 (git 2.25.0) at 2026-01-07 17:45:53 -0500