release/src-rt-6.x.4708/linux/linux-2.6.36/fs/squashfs/namei.c

   1 /* Modified by Broadcom Corp. Portions Copyright (c) Broadcom Corp, 2012. */
   2 /*
   3  * Squashfs - a compressed read only filesystem for Linux
   4  *
   5  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   6  * Phillip Lougher <phillip@lougher.demon.co.uk>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License
  10  * as published by the Free Software Foundation; either version 2,
  11  * or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  *
  22  * namei.c
  23  */
  24
  25 /*
  26  * This file implements code to do filename lookup in directories.
  27  *
  28  * Like inodes, directories are packed into compressed metadata blocks, stored
  29  * in a directory table.  Directories are accessed using the start address of
  30  * the metablock containing the directory and the offset into the
  31  * decompressed block (<block, offset>).
  32  *
  33  * Directories are organised in a slightly complex way, and are not simply
  34  * a list of file names.  The organisation takes advantage of the
  35  * fact that (in most cases) the inodes of the files will be in the same
  36  * compressed metadata block, and therefore, can share the start block.
  37  * Directories are therefore organised in a two level list, a directory
  38  * header containing the shared start block value, and a sequence of directory
  39  * entries, each of which share the shared start block.  A new directory header
  40  * is written once/if the inode start block changes.  The directory
  41  * header/directory entry list is repeated as many times as necessary.
  42  *
  43  * Directories are sorted, and can contain a directory index to speed up
  44  * file lookup.  Directory indexes store one entry per metablock, each entry
  45  * storing the index/filename mapping to the first directory header
  46  * in each metadata block.  Directories are sorted in alphabetical order,
  47  * and at lookup the index is scanned linearly looking for the first filename
  48  * alphabetically larger than the filename being looked up.  At this point the
  49  * location of the metadata block the filename is in has been found.
  50  * The general idea of the index is ensure only one metadata block needs to be
  51  * decompressed to do a lookup irrespective of the length of the directory.
  52  * This scheme has the advantage that it doesn't require extra memory overhead
  53  * and doesn't require much extra storage on disk.
  54  */
  55
  56 #include <linux/fs.h>
  57 #include <linux/vfs.h>
  58 #include <linux/slab.h>
  59 #include <linux/string.h>
  60 #include <linux/dcache.h>
  61 #include <linux/xattr.h>
  62
  63 #include "squashfs_fs.h"
  64 #include "squashfs_fs_sb.h"
  65 #include "squashfs_fs_i.h"
  66 #include "squashfs.h"
  67 #include "xattr.h"
  68
  69 /*
  70  * Lookup name in the directory index, returning the location of the metadata
  71  * block containing it, and the directory index this represents.
  72  *
  73  * If we get an error reading the index then return the part of the index
  74  * (if any) we have managed to read - the index isn't essential, just
  75  * quicker.
  76  */
  77 static int get_dir_index_using_name(struct super_block *sb,
  78                         u64 *next_block, int *next_offset, u64 index_start,
  79                         int index_offset, int i_count, const char *name,
  80                         int len)
  81 {
  82         struct squashfs_sb_info *msblk = sb->s_fs_info;
  83         int i, size, length = 0, err;
  84         struct squashfs_dir_index *index;
  85         char *str;
  86
  87         TRACE("Entered get_dir_index_using_name, i_count %d\n", i_count);
  88
  89         index = kmalloc(sizeof(*index) + SQUASHFS_NAME_LEN * 2 + 2, GFP_KERNEL);
  90         if (index == NULL) {
  91                 ERROR("Failed to allocate squashfs_dir_index\n");
  92                 goto out;
  93         }
  94
  95         str = &index->name[SQUASHFS_NAME_LEN + 1];
  96         strncpy(str, name, len);
  97         str[len] = '\0';
  98
  99         for (i = 0; i < i_count; i++) {
 100                 err = squashfs_read_metadata(sb, index, &index_start,
 101                                         &index_offset, sizeof(*index));
 102                 if (err < 0)
 103                         break;
 104
 105
 106                 size = le32_to_cpu(index->size) + 1;
 107
 108                 err = squashfs_read_metadata(sb, index->name, &index_start,
 109                                         &index_offset, size);
 110                 if (err < 0)
 111                         break;
 112
 113                 index->name[size] = '\0';
 114
 115                 if (strcmp(index->name, str) > 0)
 116                         break;
 117
 118                 length = le32_to_cpu(index->index);
 119                 *next_block = le32_to_cpu(index->start_block) +
 120                                         msblk->directory_table;
 121         }
 122
 123         *next_offset = (length + *next_offset) % SQUASHFS_METADATA_SIZE;
 124         kfree(index);
 125
 126 out:
 127         /*
 128          * Return index (f_pos) of the looked up metadata block.  Translate
 129          * from internal f_pos to external f_pos which is offset by 3 because
 130          * we invent "." and ".." entries which are not actually stored in the
 131          * directory.
 132          */
 133         return length + 3;
 134 }
 135
 136
 137 static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry,
 138                                  struct nameidata *nd)
 139 {
 140         const unsigned char *name = dentry->d_name.name;
 141         int len = dentry->d_name.len;
 142         struct inode *inode = NULL;
 143         struct squashfs_sb_info *msblk = dir->i_sb->s_fs_info;
 144         struct squashfs_dir_header dirh;
 145         struct squashfs_dir_entry *dire;
 146         u64 block = squashfs_i(dir)->start + msblk->directory_table;
 147         int offset = squashfs_i(dir)->offset;
 148         int err, length = 0, dir_count, size;
 149
 150         TRACE("Entered squashfs_lookup [%llx:%x]\n", block, offset);
 151
 152         dire = kmalloc(sizeof(*dire) + SQUASHFS_NAME_LEN + 1, GFP_KERNEL);
 153         if (dire == NULL) {
 154                 ERROR("Failed to allocate squashfs_dir_entry\n");
 155                 return ERR_PTR(-ENOMEM);
 156         }
 157
 158         if (len > SQUASHFS_NAME_LEN) {
 159                 err = -ENAMETOOLONG;
 160                 goto failed;
 161         }
 162
 163         length = get_dir_index_using_name(dir->i_sb, &block, &offset,
 164                                 squashfs_i(dir)->dir_idx_start,
 165                                 squashfs_i(dir)->dir_idx_offset,
 166                                 squashfs_i(dir)->dir_idx_cnt, name, len);
 167
 168         while (length < i_size_read(dir)) {
 169                 /*
 170                  * Read directory header.
 171                  */
 172                 err = squashfs_read_metadata(dir->i_sb, &dirh, &block,
 173                                 &offset, sizeof(dirh));
 174                 if (err < 0)
 175                         goto read_failure;
 176
 177                 length += sizeof(dirh);
 178
 179                 dir_count = le32_to_cpu(dirh.count) + 1;
 180
 181                 /* dir_count should never be larger than 256 */
 182                 if (dir_count > 256)
 183                         goto data_error;
 184
 185                 while (dir_count--) {
 186                         /*
 187                          * Read directory entry.
 188                          */
 189                         err = squashfs_read_metadata(dir->i_sb, dire, &block,
 190                                         &offset, sizeof(*dire));
 191                         if (err < 0)
 192                                 goto read_failure;
 193
 194                         size = le16_to_cpu(dire->size) + 1;
 195
 196                         /* size should never be larger than SQUASHFS_NAME_LEN */
 197                         if (size > SQUASHFS_NAME_LEN)
 198                                 goto data_error;
 199
 200                         err = squashfs_read_metadata(dir->i_sb, dire->name,
 201                                         &block, &offset, size);
 202                         if (err < 0)
 203                                 goto read_failure;
 204
 205                         length += sizeof(*dire) + size;
 206
 207                         if (name[0] < dire->name[0])
 208                                 goto exit_lookup;
 209
 210                         if (len == size && !strncmp(name, dire->name, len)) {
 211                                 unsigned int blk, off, ino_num;
 212                                 long long ino;
 213                                 blk = le32_to_cpu(dirh.start_block);
 214                                 off = le16_to_cpu(dire->offset);
 215                                 ino_num = le32_to_cpu(dirh.inode_number) +
 216                                         (short) le16_to_cpu(dire->inode_number);
 217                                 ino = SQUASHFS_MKINODE(blk, off);
 218
 219                                 TRACE("calling squashfs_iget for directory "
 220                                         "entry %s, inode  %x:%x, %d\n", name,
 221                                         blk, off, ino_num);
 222
 223                                 inode = squashfs_iget(dir->i_sb, ino, ino_num);
 224                                 if (IS_ERR(inode)) {
 225                                         err = PTR_ERR(inode);
 226                                         goto failed;
 227                                 }
 228
 229                                 goto exit_lookup;
 230                         }
 231                 }
 232         }
 233
 234 exit_lookup:
 235         kfree(dire);
 236         if (inode)
 237                 return d_splice_alias(inode, dentry);
 238         d_add(dentry, inode);
 239         return ERR_PTR(0);
 240
 241 data_error:
 242         err = -EIO;
 243
 244 read_failure:
 245         ERROR("Unable to read directory block [%llx:%x]\n",
 246                 squashfs_i(dir)->start + msblk->directory_table,
 247                 squashfs_i(dir)->offset);
 248 failed:
 249         kfree(dire);
 250         return ERR_PTR(err);
 251 }
 252
 253
 254 const struct inode_operations squashfs_dir_inode_ops = {
 255         .lookup = squashfs_lookup,
 256         .getxattr = generic_getxattr,
 257         .listxattr = squashfs_listxattr
 258 };