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 (at) 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 }; 156
