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Commit c88da2c979369e6bf8d2c0c80fad2f90c35e64ce

Authored by Phillip Lougher
1 parent 6545b246a2
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

Squashfs: directory lookup operations 

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

Showing 1 changed file with 242 additions and 0 deletions Side-by-side Diff

  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 + */
  75 +static 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 +
  124 +out:
  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 +
  135 +static 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 +
  223 +exit_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 +
  230 +read_failure:
  231 + ERROR("Unable to read directory block [%llx:%x]\n",
  232 + squashfs_i(dir)->start + msblk->directory_table,
  233 + squashfs_i(dir)->offset);
  234 +failed:
  235 + kfree(dire);
  236 + return ERR_PTR(err);
  237 +}
  238 +
  239 +
  240 +const struct inode_operations squashfs_dir_inode_ops = {
  241 + .lookup = squashfs_lookup
  242 +};