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 * fragment.c 22 */ 23 24 /* 25 * This file implements code to handle compressed fragments (tail-end packed 26 * datablocks). 27 * 28 * Regular files contain a fragment index which is mapped to a fragment 29 * location on disk and compressed size using a fragment lookup table. 30 * Like everything in Squashfs this fragment lookup table is itself stored 31 * compressed into metadata blocks. A second index table is used to locate 32 * these. This second index table for speed of access (and because it 33 * is small) is read at mount time and cached in memory. 34 */ 35 36 #include <linux/fs.h> 37 #include <linux/vfs.h> 38 #include <linux/slab.h> 39 40 #include "squashfs_fs.h" 41 #include "squashfs_fs_sb.h" 42 #include "squashfs_fs_i.h" 43 #include "squashfs.h" 44 45 /* 46 * Look-up fragment using the fragment index table. Return the on disk 47 * location of the fragment and its compressed size 48 */ 49 int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment, 50 u64 *fragment_block) 51 { 52 struct squashfs_sb_info *msblk = sb->s_fs_info; 53 int block = SQUASHFS_FRAGMENT_INDEX(fragment); 54 int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment); 55 u64 start_block = le64_to_cpu(msblk->fragment_index[block]); 56 struct squashfs_fragment_entry fragment_entry; 57 int size; 58 59 size = squashfs_read_metadata(sb, &fragment_entry, &start_block, 60 &offset, sizeof(fragment_entry)); 61 if (size < 0) 62 return size; 63 64 *fragment_block = le64_to_cpu(fragment_entry.start_block); 65 size = le32_to_cpu(fragment_entry.size); 66 67 return size; 68 } 69 70 71 /* 72 * Read the uncompressed fragment lookup table indexes off disk into memory 73 */ 74 __le64 *squashfs_read_fragment_index_table(struct super_block *sb, 75 u64 fragment_table_start, unsigned int fragments) 76 { 77 unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments); 78 __le64 *fragment_index; 79 int err; 80 81 /* Allocate fragment lookup table indexes */ 82 fragment_index = kmalloc(length, GFP_KERNEL); 83 if (fragment_index == NULL) { 84 ERROR("Failed to allocate fragment index table\n"); 85 return ERR_PTR(-ENOMEM); 86 } 87 88 err = squashfs_read_table(sb, fragment_index, fragment_table_start, 89 length); 90 if (err < 0) { 91 ERROR("unable to read fragment index table\n"); 92 kfree(fragment_index); 93 return ERR_PTR(err); 94 } 95 96 return fragment_index; 97 } 98