openfs.c revision 544349270e4c74a6feb971123884a8cf5052a7ee
1/* 2 * openfs.c --- open an ext2 filesystem 3 * 4 * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o. 5 * 6 * %Begin-Header% 7 * This file may be redistributed under the terms of the GNU Public 8 * License. 9 * %End-Header% 10 */ 11 12#include <stdio.h> 13#include <string.h> 14#if HAVE_UNISTD_H 15#include <unistd.h> 16#endif 17#include <fcntl.h> 18#include <time.h> 19#if HAVE_SYS_STAT_H 20#include <sys/stat.h> 21#endif 22#if HAVE_SYS_TYPES_H 23#include <sys/types.h> 24#endif 25 26#include "ext2_fs.h" 27 28 29#include "ext2fs.h" 30#include "e2image.h" 31 32blk_t ext2fs_descriptor_block_loc(ext2_filsys fs, blk_t group_block, dgrp_t i) 33{ 34 int bg; 35 int has_super = 0; 36 int ret_blk; 37 38 if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) || 39 (i < fs->super->s_first_meta_bg)) 40 return (group_block + i + 1); 41 42 bg = (fs->blocksize / sizeof (struct ext2_group_desc)) * i; 43 if (ext2fs_bg_has_super(fs, bg)) 44 has_super = 1; 45 ret_blk = (fs->super->s_first_data_block + has_super + 46 (bg * fs->super->s_blocks_per_group)); 47 /* 48 * If group_block is not the normal value, we're trying to use 49 * the backup group descriptors and superblock --- so use the 50 * alternate location of the second block group in the 51 * metablock group. Ideally we should be testing each bg 52 * descriptor block individually for correctness, but we don't 53 * have the infrastructure in place to do that. 54 */ 55 if (group_block != fs->super->s_first_data_block && 56 ((ret_blk + fs->super->s_blocks_per_group) < 57 fs->super->s_blocks_count)) 58 ret_blk += fs->super->s_blocks_per_group; 59 return ret_blk; 60} 61 62/* 63 * Note: if superblock is non-zero, block-size must also be non-zero. 64 * Superblock and block_size can be zero to use the default size. 65 * 66 * Valid flags for ext2fs_open() 67 * 68 * EXT2_FLAG_RW - Open the filesystem for read/write. 69 * EXT2_FLAG_FORCE - Open the filesystem even if some of the 70 * features aren't supported. 71 * EXT2_FLAG_JOURNAL_DEV_OK - Open an ext3 journal device 72 */ 73errcode_t ext2fs_open(const char *name, int flags, int superblock, 74 unsigned int block_size, io_manager manager, 75 ext2_filsys *ret_fs) 76{ 77 ext2_filsys fs; 78 errcode_t retval; 79 unsigned long i; 80 int j, groups_per_block, blocks_per_group; 81 blk_t group_block, blk; 82 char *dest; 83 struct ext2_group_desc *gdp; 84 85 EXT2_CHECK_MAGIC(manager, EXT2_ET_MAGIC_IO_MANAGER); 86 87 retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs); 88 if (retval) 89 return retval; 90 91 memset(fs, 0, sizeof(struct struct_ext2_filsys)); 92 fs->magic = EXT2_ET_MAGIC_EXT2FS_FILSYS; 93 fs->flags = flags; 94 fs->umask = 022; 95 retval = manager->open(name, (flags & EXT2_FLAG_RW) ? IO_FLAG_RW : 0, 96 &fs->io); 97 if (retval) 98 goto cleanup; 99 fs->io->app_data = fs; 100 retval = ext2fs_get_mem(strlen(name)+1, &fs->device_name); 101 if (retval) 102 goto cleanup; 103 strcpy(fs->device_name, name); 104 retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->super); 105 if (retval) 106 goto cleanup; 107 if (flags & EXT2_FLAG_IMAGE_FILE) { 108 retval = ext2fs_get_mem(sizeof(struct ext2_image_hdr), 109 &fs->image_header); 110 if (retval) 111 goto cleanup; 112 retval = io_channel_read_blk(fs->io, 0, 113 -sizeof(struct ext2_image_hdr), 114 fs->image_header); 115 if (retval) 116 goto cleanup; 117 if (fs->image_header->magic_number != EXT2_ET_MAGIC_E2IMAGE) 118 return EXT2_ET_MAGIC_E2IMAGE; 119 superblock = 1; 120 block_size = fs->image_header->fs_blocksize; 121 } 122 123 /* 124 * If the user specifies a specific block # for the 125 * superblock, then he/she must also specify the block size! 126 * Otherwise, read the master superblock located at offset 127 * SUPERBLOCK_OFFSET from the start of the partition. 128 * 129 * Note: we only save a backup copy of the superblock if we 130 * are reading the superblock from the primary superblock location. 131 */ 132 if (superblock) { 133 if (!block_size) { 134 retval = EXT2_ET_INVALID_ARGUMENT; 135 goto cleanup; 136 } 137 io_channel_set_blksize(fs->io, block_size); 138 group_block = superblock; 139 fs->orig_super = 0; 140 } else { 141 io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET); 142 superblock = 1; 143 group_block = 0; 144 retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super); 145 if (retval) 146 goto cleanup; 147 } 148 retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE, 149 fs->super); 150 if (retval) 151 goto cleanup; 152 if (fs->orig_super) 153 memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE); 154 155#ifdef EXT2FS_ENABLE_SWAPFS 156 if ((fs->super->s_magic == ext2fs_swab16(EXT2_SUPER_MAGIC)) || 157 (fs->flags & EXT2_FLAG_SWAP_BYTES)) { 158 fs->flags |= EXT2_FLAG_SWAP_BYTES; 159 160 ext2fs_swap_super(fs->super); 161 } 162#endif 163 164 if (fs->super->s_magic != EXT2_SUPER_MAGIC) { 165 retval = EXT2_ET_BAD_MAGIC; 166 goto cleanup; 167 } 168 if (fs->super->s_rev_level > EXT2_LIB_CURRENT_REV) { 169 retval = EXT2_ET_REV_TOO_HIGH; 170 goto cleanup; 171 } 172 173 /* 174 * Check for feature set incompatibility 175 */ 176 if (!(flags & EXT2_FLAG_FORCE)) { 177 if (fs->super->s_feature_incompat & 178 ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) { 179 retval = EXT2_ET_UNSUPP_FEATURE; 180 goto cleanup; 181 } 182 if ((flags & EXT2_FLAG_RW) && 183 (fs->super->s_feature_ro_compat & 184 ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) { 185 retval = EXT2_ET_RO_UNSUPP_FEATURE; 186 goto cleanup; 187 } 188 if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) && 189 (fs->super->s_feature_incompat & 190 EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) { 191 retval = EXT2_ET_UNSUPP_FEATURE; 192 goto cleanup; 193 } 194 } 195 196 fs->blocksize = EXT2_BLOCK_SIZE(fs->super); 197 if (fs->blocksize == 0) { 198 retval = EXT2_ET_CORRUPT_SUPERBLOCK; 199 goto cleanup; 200 } 201 fs->fragsize = EXT2_FRAG_SIZE(fs->super); 202 fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group * 203 EXT2_INODE_SIZE(fs->super) + 204 EXT2_BLOCK_SIZE(fs->super) - 1) / 205 EXT2_BLOCK_SIZE(fs->super)); 206 if (block_size) { 207 if (block_size != fs->blocksize) { 208 retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE; 209 goto cleanup; 210 } 211 } 212 /* 213 * Set the blocksize to the filesystem's blocksize. 214 */ 215 io_channel_set_blksize(fs->io, fs->blocksize); 216 217 /* 218 * If this is an external journal device, don't try to read 219 * the group descriptors, because they're not there. 220 */ 221 if (fs->super->s_feature_incompat & 222 EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) { 223 fs->group_desc_count = 0; 224 *ret_fs = fs; 225 return 0; 226 } 227 228 /* 229 * Read group descriptors 230 */ 231 blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super); 232 if (blocks_per_group == 0 || 233 blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) || 234 fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super)) { 235 retval = EXT2_ET_CORRUPT_SUPERBLOCK; 236 goto cleanup; 237 } 238 fs->group_desc_count = (fs->super->s_blocks_count - 239 fs->super->s_first_data_block + 240 blocks_per_group - 1) / blocks_per_group; 241 fs->desc_blocks = (fs->group_desc_count + 242 EXT2_DESC_PER_BLOCK(fs->super) - 1) 243 / EXT2_DESC_PER_BLOCK(fs->super); 244 retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize, 245 &fs->group_desc); 246 if (retval) 247 goto cleanup; 248 if (!group_block) 249 group_block = fs->super->s_first_data_block; 250 dest = (char *) fs->group_desc; 251 groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc); 252 for (i=0 ; i < fs->desc_blocks; i++) { 253 blk = ext2fs_descriptor_block_loc(fs, group_block, i); 254 retval = io_channel_read_blk(fs->io, blk, 1, dest); 255 if (retval) 256 goto cleanup; 257#ifdef EXT2FS_ENABLE_SWAPFS 258 if (fs->flags & EXT2_FLAG_SWAP_BYTES) { 259 gdp = (struct ext2_group_desc *) dest; 260 for (j=0; j < groups_per_block; j++) 261 ext2fs_swap_group_desc(gdp++); 262 } 263#endif 264 dest += fs->blocksize; 265 } 266 267 *ret_fs = fs; 268 return 0; 269cleanup: 270 ext2fs_free(fs); 271 return retval; 272} 273 274