Phillip Lougher | 1226014 | 2009-01-05 08:46:25 +0000 | [diff] [blame] | 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 | * export.c |
| 22 | */ |
| 23 | |
| 24 | /* |
| 25 | * This file implements code to make Squashfs filesystems exportable (NFS etc.) |
| 26 | * |
| 27 | * The export code uses an inode lookup table to map inode numbers passed in |
| 28 | * filehandles to an inode location on disk. This table is stored compressed |
| 29 | * into metadata blocks. A second index table is used to locate these. This |
| 30 | * second index table for speed of access (and because it is small) is read at |
| 31 | * mount time and cached in memory. |
| 32 | * |
| 33 | * The inode lookup table is used only by the export code, inode disk |
| 34 | * locations are directly encoded in directories, enabling direct access |
| 35 | * without an intermediate lookup for all operations except the export ops. |
| 36 | */ |
| 37 | |
| 38 | #include <linux/fs.h> |
| 39 | #include <linux/vfs.h> |
| 40 | #include <linux/dcache.h> |
| 41 | #include <linux/exportfs.h> |
| 42 | #include <linux/zlib.h> |
| 43 | |
| 44 | #include "squashfs_fs.h" |
| 45 | #include "squashfs_fs_sb.h" |
| 46 | #include "squashfs_fs_i.h" |
| 47 | #include "squashfs.h" |
| 48 | |
| 49 | /* |
| 50 | * Look-up inode number (ino) in table, returning the inode location. |
| 51 | */ |
| 52 | static long long squashfs_inode_lookup(struct super_block *sb, int ino_num) |
| 53 | { |
| 54 | struct squashfs_sb_info *msblk = sb->s_fs_info; |
| 55 | int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1); |
| 56 | int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1); |
| 57 | u64 start = le64_to_cpu(msblk->inode_lookup_table[blk]); |
| 58 | __le64 ino; |
| 59 | int err; |
| 60 | |
| 61 | TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); |
| 62 | |
| 63 | err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino)); |
| 64 | if (err < 0) |
| 65 | return err; |
| 66 | |
| 67 | TRACE("squashfs_inode_lookup, inode = 0x%llx\n", |
| 68 | (u64) le64_to_cpu(ino)); |
| 69 | |
| 70 | return le64_to_cpu(ino); |
| 71 | } |
| 72 | |
| 73 | |
| 74 | static struct dentry *squashfs_export_iget(struct super_block *sb, |
| 75 | unsigned int ino_num) |
| 76 | { |
| 77 | long long ino; |
| 78 | struct dentry *dentry = ERR_PTR(-ENOENT); |
| 79 | |
| 80 | TRACE("Entered squashfs_export_iget\n"); |
| 81 | |
| 82 | ino = squashfs_inode_lookup(sb, ino_num); |
| 83 | if (ino >= 0) |
| 84 | dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); |
| 85 | |
| 86 | return dentry; |
| 87 | } |
| 88 | |
| 89 | |
| 90 | static struct dentry *squashfs_fh_to_dentry(struct super_block *sb, |
| 91 | struct fid *fid, int fh_len, int fh_type) |
| 92 | { |
| 93 | if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT) |
| 94 | || fh_len < 2) |
| 95 | return NULL; |
| 96 | |
| 97 | return squashfs_export_iget(sb, fid->i32.ino); |
| 98 | } |
| 99 | |
| 100 | |
| 101 | static struct dentry *squashfs_fh_to_parent(struct super_block *sb, |
| 102 | struct fid *fid, int fh_len, int fh_type) |
| 103 | { |
| 104 | if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4) |
| 105 | return NULL; |
| 106 | |
| 107 | return squashfs_export_iget(sb, fid->i32.parent_ino); |
| 108 | } |
| 109 | |
| 110 | |
| 111 | static struct dentry *squashfs_get_parent(struct dentry *child) |
| 112 | { |
| 113 | struct inode *inode = child->d_inode; |
| 114 | unsigned int parent_ino = squashfs_i(inode)->parent; |
| 115 | |
| 116 | return squashfs_export_iget(inode->i_sb, parent_ino); |
| 117 | } |
| 118 | |
| 119 | |
| 120 | /* |
| 121 | * Read uncompressed inode lookup table indexes off disk into memory |
| 122 | */ |
| 123 | __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, |
| 124 | u64 lookup_table_start, unsigned int inodes) |
| 125 | { |
| 126 | unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); |
| 127 | __le64 *inode_lookup_table; |
| 128 | int err; |
| 129 | |
| 130 | TRACE("In read_inode_lookup_table, length %d\n", length); |
| 131 | |
| 132 | /* Allocate inode lookup table indexes */ |
| 133 | inode_lookup_table = kmalloc(length, GFP_KERNEL); |
| 134 | if (inode_lookup_table == NULL) { |
| 135 | ERROR("Failed to allocate inode lookup table\n"); |
| 136 | return ERR_PTR(-ENOMEM); |
| 137 | } |
| 138 | |
| 139 | err = squashfs_read_table(sb, inode_lookup_table, lookup_table_start, |
| 140 | length); |
| 141 | if (err < 0) { |
| 142 | ERROR("unable to read inode lookup table\n"); |
| 143 | kfree(inode_lookup_table); |
| 144 | return ERR_PTR(err); |
| 145 | } |
| 146 | |
| 147 | return inode_lookup_table; |
| 148 | } |
| 149 | |
| 150 | |
| 151 | const struct export_operations squashfs_export_ops = { |
| 152 | .fh_to_dentry = squashfs_fh_to_dentry, |
| 153 | .fh_to_parent = squashfs_fh_to_parent, |
| 154 | .get_parent = squashfs_get_parent |
| 155 | }; |