1 #include <linux/fs.h> 2 #include <linux/random.h> 3 #include <linux/buffer_head.h> 4 #include <linux/utsname.h> 5 #include <linux/kthread.h> 6 7 #include "ext4.h" 8 9 /* Checksumming functions */ 10 static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp) 11 { 12 struct ext4_sb_info *sbi = EXT4_SB(sb); 13 int offset = offsetof(struct mmp_struct, mmp_checksum); 14 __u32 csum; 15 16 csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset); 17 18 return cpu_to_le32(csum); 19 } 20 21 static int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp) 22 { 23 if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, 24 EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) 25 return 1; 26 27 return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp); 28 } 29 30 static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp) 31 { 32 if (!EXT4_HAS_RO_COMPAT_FEATURE(sb, 33 EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) 34 return; 35 36 mmp->mmp_checksum = ext4_mmp_csum(sb, mmp); 37 } 38 39 /* 40 * Write the MMP block using WRITE_SYNC to try to get the block on-disk 41 * faster. 42 */ 43 static int write_mmp_block(struct super_block *sb, struct buffer_head *bh) 44 { 45 struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data); 46 47 /* 48 * We protect against freezing so that we don't create dirty buffers 49 * on frozen filesystem. 50 */ 51 sb_start_write(sb); 52 ext4_mmp_csum_set(sb, mmp); 53 mark_buffer_dirty(bh); 54 lock_buffer(bh); 55 bh->b_end_io = end_buffer_write_sync; 56 get_bh(bh); 57 submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh); 58 wait_on_buffer(bh); 59 sb_end_write(sb); 60 if (unlikely(!buffer_uptodate(bh))) 61 return 1; 62 63 return 0; 64 } 65 66 /* 67 * Read the MMP block. It _must_ be read from disk and hence we clear the 68 * uptodate flag on the buffer. 69 */ 70 static int read_mmp_block(struct super_block *sb, struct buffer_head **bh, 71 ext4_fsblk_t mmp_block) 72 { 73 struct mmp_struct *mmp; 74 75 if (*bh) 76 clear_buffer_uptodate(*bh); 77 78 /* This would be sb_bread(sb, mmp_block), except we need to be sure 79 * that the MD RAID device cache has been bypassed, and that the read 80 * is not blocked in the elevator. */ 81 if (!*bh) 82 *bh = sb_getblk(sb, mmp_block); 83 if (!*bh) 84 return -ENOMEM; 85 if (*bh) { 86 get_bh(*bh); 87 lock_buffer(*bh); 88 (*bh)->b_end_io = end_buffer_read_sync; 89 submit_bh(READ_SYNC | REQ_META | REQ_PRIO, *bh); 90 wait_on_buffer(*bh); 91 if (!buffer_uptodate(*bh)) { 92 brelse(*bh); 93 *bh = NULL; 94 } 95 } 96 if (unlikely(!*bh)) { 97 ext4_warning(sb, "Error while reading MMP block %llu", 98 mmp_block); 99 return -EIO; 100 } 101 102 mmp = (struct mmp_struct *)((*bh)->b_data); 103 if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC || 104 !ext4_mmp_csum_verify(sb, mmp)) 105 return -EINVAL; 106 107 return 0; 108 } 109 110 /* 111 * Dump as much information as possible to help the admin. 112 */ 113 void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp, 114 const char *function, unsigned int line, const char *msg) 115 { 116 __ext4_warning(sb, function, line, msg); 117 __ext4_warning(sb, function, line, 118 "MMP failure info: last update time: %llu, last update " 119 "node: %s, last update device: %s\n", 120 (long long unsigned int) le64_to_cpu(mmp->mmp_time), 121 mmp->mmp_nodename, mmp->mmp_bdevname); 122 } 123 124 /* 125 * kmmpd will update the MMP sequence every s_mmp_update_interval seconds 126 */ 127 static int kmmpd(void *data) 128 { 129 struct super_block *sb = ((struct mmpd_data *) data)->sb; 130 struct buffer_head *bh = ((struct mmpd_data *) data)->bh; 131 struct ext4_super_block *es = EXT4_SB(sb)->s_es; 132 struct mmp_struct *mmp; 133 ext4_fsblk_t mmp_block; 134 u32 seq = 0; 135 unsigned long failed_writes = 0; 136 int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval); 137 unsigned mmp_check_interval; 138 unsigned long last_update_time; 139 unsigned long diff; 140 int retval; 141 142 mmp_block = le64_to_cpu(es->s_mmp_block); 143 mmp = (struct mmp_struct *)(bh->b_data); 144 mmp->mmp_time = cpu_to_le64(get_seconds()); 145 /* 146 * Start with the higher mmp_check_interval and reduce it if 147 * the MMP block is being updated on time. 148 */ 149 mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval, 150 EXT4_MMP_MIN_CHECK_INTERVAL); 151 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval); 152 bdevname(bh->b_bdev, mmp->mmp_bdevname); 153 154 memcpy(mmp->mmp_nodename, init_utsname()->nodename, 155 sizeof(mmp->mmp_nodename)); 156 157 while (!kthread_should_stop()) { 158 if (++seq > EXT4_MMP_SEQ_MAX) 159 seq = 1; 160 161 mmp->mmp_seq = cpu_to_le32(seq); 162 mmp->mmp_time = cpu_to_le64(get_seconds()); 163 last_update_time = jiffies; 164 165 retval = write_mmp_block(sb, bh); 166 /* 167 * Don't spew too many error messages. Print one every 168 * (s_mmp_update_interval * 60) seconds. 169 */ 170 if (retval) { 171 if ((failed_writes % 60) == 0) 172 ext4_error(sb, "Error writing to MMP block"); 173 failed_writes++; 174 } 175 176 if (!(le32_to_cpu(es->s_feature_incompat) & 177 EXT4_FEATURE_INCOMPAT_MMP)) { 178 ext4_warning(sb, "kmmpd being stopped since MMP feature" 179 " has been disabled."); 180 EXT4_SB(sb)->s_mmp_tsk = NULL; 181 goto failed; 182 } 183 184 if (sb->s_flags & MS_RDONLY) { 185 ext4_warning(sb, "kmmpd being stopped since filesystem " 186 "has been remounted as readonly."); 187 EXT4_SB(sb)->s_mmp_tsk = NULL; 188 goto failed; 189 } 190 191 diff = jiffies - last_update_time; 192 if (diff < mmp_update_interval * HZ) 193 schedule_timeout_interruptible(mmp_update_interval * 194 HZ - diff); 195 196 /* 197 * We need to make sure that more than mmp_check_interval 198 * seconds have not passed since writing. If that has happened 199 * we need to check if the MMP block is as we left it. 200 */ 201 diff = jiffies - last_update_time; 202 if (diff > mmp_check_interval * HZ) { 203 struct buffer_head *bh_check = NULL; 204 struct mmp_struct *mmp_check; 205 206 retval = read_mmp_block(sb, &bh_check, mmp_block); 207 if (retval) { 208 ext4_error(sb, "error reading MMP data: %d", 209 retval); 210 211 EXT4_SB(sb)->s_mmp_tsk = NULL; 212 goto failed; 213 } 214 215 mmp_check = (struct mmp_struct *)(bh_check->b_data); 216 if (mmp->mmp_seq != mmp_check->mmp_seq || 217 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename, 218 sizeof(mmp->mmp_nodename))) { 219 dump_mmp_msg(sb, mmp_check, 220 "Error while updating MMP info. " 221 "The filesystem seems to have been" 222 " multiply mounted."); 223 ext4_error(sb, "abort"); 224 goto failed; 225 } 226 put_bh(bh_check); 227 } 228 229 /* 230 * Adjust the mmp_check_interval depending on how much time 231 * it took for the MMP block to be written. 232 */ 233 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ, 234 EXT4_MMP_MAX_CHECK_INTERVAL), 235 EXT4_MMP_MIN_CHECK_INTERVAL); 236 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval); 237 } 238 239 /* 240 * Unmount seems to be clean. 241 */ 242 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN); 243 mmp->mmp_time = cpu_to_le64(get_seconds()); 244 245 retval = write_mmp_block(sb, bh); 246 247 failed: 248 kfree(data); 249 brelse(bh); 250 return retval; 251 } 252 253 /* 254 * Get a random new sequence number but make sure it is not greater than 255 * EXT4_MMP_SEQ_MAX. 256 */ 257 static unsigned int mmp_new_seq(void) 258 { 259 u32 new_seq; 260 261 do { 262 new_seq = prandom_u32(); 263 } while (new_seq > EXT4_MMP_SEQ_MAX); 264 265 return new_seq; 266 } 267 268 /* 269 * Protect the filesystem from being mounted more than once. 270 */ 271 int ext4_multi_mount_protect(struct super_block *sb, 272 ext4_fsblk_t mmp_block) 273 { 274 struct ext4_super_block *es = EXT4_SB(sb)->s_es; 275 struct buffer_head *bh = NULL; 276 struct mmp_struct *mmp = NULL; 277 struct mmpd_data *mmpd_data; 278 u32 seq; 279 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval); 280 unsigned int wait_time = 0; 281 int retval; 282 283 if (mmp_block < le32_to_cpu(es->s_first_data_block) || 284 mmp_block >= ext4_blocks_count(es)) { 285 ext4_warning(sb, "Invalid MMP block in superblock"); 286 goto failed; 287 } 288 289 retval = read_mmp_block(sb, &bh, mmp_block); 290 if (retval) 291 goto failed; 292 293 mmp = (struct mmp_struct *)(bh->b_data); 294 295 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL) 296 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL; 297 298 /* 299 * If check_interval in MMP block is larger, use that instead of 300 * update_interval from the superblock. 301 */ 302 if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval) 303 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval); 304 305 seq = le32_to_cpu(mmp->mmp_seq); 306 if (seq == EXT4_MMP_SEQ_CLEAN) 307 goto skip; 308 309 if (seq == EXT4_MMP_SEQ_FSCK) { 310 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem"); 311 goto failed; 312 } 313 314 wait_time = min(mmp_check_interval * 2 + 1, 315 mmp_check_interval + 60); 316 317 /* Print MMP interval if more than 20 secs. */ 318 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4) 319 ext4_warning(sb, "MMP interval %u higher than expected, please" 320 " wait.\n", wait_time * 2); 321 322 if (schedule_timeout_interruptible(HZ * wait_time) != 0) { 323 ext4_warning(sb, "MMP startup interrupted, failing mount\n"); 324 goto failed; 325 } 326 327 retval = read_mmp_block(sb, &bh, mmp_block); 328 if (retval) 329 goto failed; 330 mmp = (struct mmp_struct *)(bh->b_data); 331 if (seq != le32_to_cpu(mmp->mmp_seq)) { 332 dump_mmp_msg(sb, mmp, 333 "Device is already active on another node."); 334 goto failed; 335 } 336 337 skip: 338 /* 339 * write a new random sequence number. 340 */ 341 seq = mmp_new_seq(); 342 mmp->mmp_seq = cpu_to_le32(seq); 343 344 retval = write_mmp_block(sb, bh); 345 if (retval) 346 goto failed; 347 348 /* 349 * wait for MMP interval and check mmp_seq. 350 */ 351 if (schedule_timeout_interruptible(HZ * wait_time) != 0) { 352 ext4_warning(sb, "MMP startup interrupted, failing mount\n"); 353 goto failed; 354 } 355 356 retval = read_mmp_block(sb, &bh, mmp_block); 357 if (retval) 358 goto failed; 359 mmp = (struct mmp_struct *)(bh->b_data); 360 if (seq != le32_to_cpu(mmp->mmp_seq)) { 361 dump_mmp_msg(sb, mmp, 362 "Device is already active on another node."); 363 goto failed; 364 } 365 366 mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL); 367 if (!mmpd_data) { 368 ext4_warning(sb, "not enough memory for mmpd_data"); 369 goto failed; 370 } 371 mmpd_data->sb = sb; 372 mmpd_data->bh = bh; 373 374 /* 375 * Start a kernel thread to update the MMP block periodically. 376 */ 377 EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s", 378 bdevname(bh->b_bdev, 379 mmp->mmp_bdevname)); 380 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) { 381 EXT4_SB(sb)->s_mmp_tsk = NULL; 382 kfree(mmpd_data); 383 ext4_warning(sb, "Unable to create kmmpd thread for %s.", 384 sb->s_id); 385 goto failed; 386 } 387 388 return 0; 389 390 failed: 391 brelse(bh); 392 return 1; 393 } 394 395 396