Commit 122edd1514aaaa90fd894663ecfcb4135063c63d
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Squashfs: fragment block operations
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Showing 1 changed file with 98 additions and 0 deletions Side-by-side Diff
fs/squashfs/fragment.c
| 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 | +#include <linux/zlib.h> | |
| 40 | + | |
| 41 | +#include "squashfs_fs.h" | |
| 42 | +#include "squashfs_fs_sb.h" | |
| 43 | +#include "squashfs_fs_i.h" | |
| 44 | +#include "squashfs.h" | |
| 45 | + | |
| 46 | +/* | |
| 47 | + * Look-up fragment using the fragment index table. Return the on disk | |
| 48 | + * location of the fragment and its compressed size | |
| 49 | + */ | |
| 50 | +int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment, | |
| 51 | + u64 *fragment_block) | |
| 52 | +{ | |
| 53 | + struct squashfs_sb_info *msblk = sb->s_fs_info; | |
| 54 | + int block = SQUASHFS_FRAGMENT_INDEX(fragment); | |
| 55 | + int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment); | |
| 56 | + u64 start_block = le64_to_cpu(msblk->fragment_index[block]); | |
| 57 | + struct squashfs_fragment_entry fragment_entry; | |
| 58 | + int size; | |
| 59 | + | |
| 60 | + size = squashfs_read_metadata(sb, &fragment_entry, &start_block, | |
| 61 | + &offset, sizeof(fragment_entry)); | |
| 62 | + if (size < 0) | |
| 63 | + return size; | |
| 64 | + | |
| 65 | + *fragment_block = le64_to_cpu(fragment_entry.start_block); | |
| 66 | + size = le32_to_cpu(fragment_entry.size); | |
| 67 | + | |
| 68 | + return size; | |
| 69 | +} | |
| 70 | + | |
| 71 | + | |
| 72 | +/* | |
| 73 | + * Read the uncompressed fragment lookup table indexes off disk into memory | |
| 74 | + */ | |
| 75 | +__le64 *squashfs_read_fragment_index_table(struct super_block *sb, | |
| 76 | + u64 fragment_table_start, unsigned int fragments) | |
| 77 | +{ | |
| 78 | + unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments); | |
| 79 | + __le64 *fragment_index; | |
| 80 | + int err; | |
| 81 | + | |
| 82 | + /* Allocate fragment lookup table indexes */ | |
| 83 | + fragment_index = kmalloc(length, GFP_KERNEL); | |
| 84 | + if (fragment_index == NULL) { | |
| 85 | + ERROR("Failed to allocate fragment index table\n"); | |
| 86 | + return ERR_PTR(-ENOMEM); | |
| 87 | + } | |
| 88 | + | |
| 89 | + err = squashfs_read_table(sb, fragment_index, fragment_table_start, | |
| 90 | + length); | |
| 91 | + if (err < 0) { | |
| 92 | + ERROR("unable to read fragment index table\n"); | |
| 93 | + kfree(fragment_index); | |
| 94 | + return ERR_PTR(err); | |
| 95 | + } | |
| 96 | + | |
| 97 | + return fragment_index; | |
| 98 | +} |