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_metadata_csum(sb)) 24 return 1; 25 26 return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp); 27 } 28 29 static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp) 30 { 31 if (!ext4_has_metadata_csum(sb)) 32 return; 33 34 mmp->mmp_checksum = ext4_mmp_csum(sb, mmp); 35 } 36 37 /* 38 * Write the MMP block using WRITE_SYNC to try to get the block on-disk 39 * faster. 40 */ 41 static int write_mmp_block(struct super_block *sb, struct buffer_head *bh) 42 { 43 struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data); 44 45 /* 46 * We protect against freezing so that we don't create dirty buffers 47 * on frozen filesystem. 48 */ 49 sb_start_write(sb); 50 ext4_mmp_csum_set(sb, mmp); 51 mark_buffer_dirty(bh); 52 lock_buffer(bh); 53 bh->b_end_io = end_buffer_write_sync; 54 get_bh(bh); 55 submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh); 56 wait_on_buffer(bh); 57 sb_end_write(sb); 58 if (unlikely(!buffer_uptodate(bh))) 59 return 1; 60 61 return 0; 62 } 63 64 /* 65 * Read the MMP block. It _must_ be read from disk and hence we clear the 66 * uptodate flag on the buffer. 67 */ 68 static int read_mmp_block(struct super_block *sb, struct buffer_head **bh, 69 ext4_fsblk_t mmp_block) 70 { 71 struct mmp_struct *mmp; 72 int ret; 73 74 if (*bh) 75 clear_buffer_uptodate(*bh); 76 77 /* This would be sb_bread(sb, mmp_block), except we need to be sure 78 * that the MD RAID device cache has been bypassed, and that the read 79 * is not blocked in the elevator. */ 80 if (!*bh) { 81 *bh = sb_getblk(sb, mmp_block); 82 if (!*bh) { 83 ret = -ENOMEM; 84 goto warn_exit; 85 } 86 } 87 88 get_bh(*bh); 89 lock_buffer(*bh); 90 (*bh)->b_end_io = end_buffer_read_sync; 91 submit_bh(READ_SYNC | REQ_META | REQ_PRIO, *bh); 92 wait_on_buffer(*bh); 93 if (!buffer_uptodate(*bh)) { 94 brelse(*bh); 95 *bh = NULL; 96 ret = -EIO; 97 goto warn_exit; 98 } 99 100 mmp = (struct mmp_struct *)((*bh)->b_data); 101 if (le32_to_cpu(mmp->mmp_magic) == EXT4_MMP_MAGIC && 102 ext4_mmp_csum_verify(sb, mmp)) 103 return 0; 104 ret = -EINVAL; 105 106 warn_exit: 107 ext4_warning(sb, "Error %d while reading MMP block %llu", 108 ret, mmp_block); 109 return ret; 110 } 111 112 /* 113 * Dump as much information as possible to help the admin. 114 */ 115 void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp, 116 const char *function, unsigned int line, const char *msg) 117 { 118 __ext4_warning(sb, function, line, "%s", msg); 119 __ext4_warning(sb, function, line, 120 "MMP failure info: last update time: %llu, last update " 121 "node: %s, last update device: %s\n", 122 (long long unsigned int) le64_to_cpu(mmp->mmp_time), 123 mmp->mmp_nodename, mmp->mmp_bdevname); 124 } 125 126 /* 127 * kmmpd will update the MMP sequence every s_mmp_update_interval seconds 128 */ 129 static int kmmpd(void *data) 130 { 131 struct super_block *sb = ((struct mmpd_data *) data)->sb; 132 struct buffer_head *bh = ((struct mmpd_data *) data)->bh; 133 struct ext4_super_block *es = EXT4_SB(sb)->s_es; 134 struct mmp_struct *mmp; 135 ext4_fsblk_t mmp_block; 136 u32 seq = 0; 137 unsigned long failed_writes = 0; 138 int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval); 139 unsigned mmp_check_interval; 140 unsigned long last_update_time; 141 unsigned long diff; 142 int retval; 143 144 mmp_block = le64_to_cpu(es->s_mmp_block); 145 mmp = (struct mmp_struct *)(bh->b_data); 146 mmp->mmp_time = cpu_to_le64(get_seconds()); 147 /* 148 * Start with the higher mmp_check_interval and reduce it if 149 * the MMP block is being updated on time. 150 */ 151 mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval, 152 EXT4_MMP_MIN_CHECK_INTERVAL); 153 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval); 154 bdevname(bh->b_bdev, mmp->mmp_bdevname); 155 156 memcpy(mmp->mmp_nodename, init_utsname()->nodename, 157 sizeof(mmp->mmp_nodename)); 158 159 while (!kthread_should_stop()) { 160 if (++seq > EXT4_MMP_SEQ_MAX) 161 seq = 1; 162 163 mmp->mmp_seq = cpu_to_le32(seq); 164 mmp->mmp_time = cpu_to_le64(get_seconds()); 165 last_update_time = jiffies; 166 167 retval = write_mmp_block(sb, bh); 168 /* 169 * Don't spew too many error messages. Print one every 170 * (s_mmp_update_interval * 60) seconds. 171 */ 172 if (retval) { 173 if ((failed_writes % 60) == 0) 174 ext4_error(sb, "Error writing to MMP block"); 175 failed_writes++; 176 } 177 178 if (!(le32_to_cpu(es->s_feature_incompat) & 179 EXT4_FEATURE_INCOMPAT_MMP)) { 180 ext4_warning(sb, "kmmpd being stopped since MMP feature" 181 " has been disabled."); 182 EXT4_SB(sb)->s_mmp_tsk = NULL; 183 goto failed; 184 } 185 186 if (sb->s_flags & MS_RDONLY) { 187 ext4_warning(sb, "kmmpd being stopped since filesystem " 188 "has been remounted as readonly."); 189 EXT4_SB(sb)->s_mmp_tsk = NULL; 190 goto failed; 191 } 192 193 diff = jiffies - last_update_time; 194 if (diff < mmp_update_interval * HZ) 195 schedule_timeout_interruptible(mmp_update_interval * 196 HZ - diff); 197 198 /* 199 * We need to make sure that more than mmp_check_interval 200 * seconds have not passed since writing. If that has happened 201 * we need to check if the MMP block is as we left it. 202 */ 203 diff = jiffies - last_update_time; 204 if (diff > mmp_check_interval * HZ) { 205 struct buffer_head *bh_check = NULL; 206 struct mmp_struct *mmp_check; 207 208 retval = read_mmp_block(sb, &bh_check, mmp_block); 209 if (retval) { 210 ext4_error(sb, "error reading MMP data: %d", 211 retval); 212 213 EXT4_SB(sb)->s_mmp_tsk = NULL; 214 goto failed; 215 } 216 217 mmp_check = (struct mmp_struct *)(bh_check->b_data); 218 if (mmp->mmp_seq != mmp_check->mmp_seq || 219 memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename, 220 sizeof(mmp->mmp_nodename))) { 221 dump_mmp_msg(sb, mmp_check, 222 "Error while updating MMP info. " 223 "The filesystem seems to have been" 224 " multiply mounted."); 225 ext4_error(sb, "abort"); 226 goto failed; 227 } 228 put_bh(bh_check); 229 } 230 231 /* 232 * Adjust the mmp_check_interval depending on how much time 233 * it took for the MMP block to be written. 234 */ 235 mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ, 236 EXT4_MMP_MAX_CHECK_INTERVAL), 237 EXT4_MMP_MIN_CHECK_INTERVAL); 238 mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval); 239 } 240 241 /* 242 * Unmount seems to be clean. 243 */ 244 mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN); 245 mmp->mmp_time = cpu_to_le64(get_seconds()); 246 247 retval = write_mmp_block(sb, bh); 248 249 failed: 250 kfree(data); 251 brelse(bh); 252 return retval; 253 } 254 255 /* 256 * Get a random new sequence number but make sure it is not greater than 257 * EXT4_MMP_SEQ_MAX. 258 */ 259 static unsigned int mmp_new_seq(void) 260 { 261 u32 new_seq; 262 263 do { 264 new_seq = prandom_u32(); 265 } while (new_seq > EXT4_MMP_SEQ_MAX); 266 267 return new_seq; 268 } 269 270 /* 271 * Protect the filesystem from being mounted more than once. 272 */ 273 int ext4_multi_mount_protect(struct super_block *sb, 274 ext4_fsblk_t mmp_block) 275 { 276 struct ext4_super_block *es = EXT4_SB(sb)->s_es; 277 struct buffer_head *bh = NULL; 278 struct mmp_struct *mmp = NULL; 279 struct mmpd_data *mmpd_data; 280 u32 seq; 281 unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval); 282 unsigned int wait_time = 0; 283 int retval; 284 285 if (mmp_block < le32_to_cpu(es->s_first_data_block) || 286 mmp_block >= ext4_blocks_count(es)) { 287 ext4_warning(sb, "Invalid MMP block in superblock"); 288 goto failed; 289 } 290 291 retval = read_mmp_block(sb, &bh, mmp_block); 292 if (retval) 293 goto failed; 294 295 mmp = (struct mmp_struct *)(bh->b_data); 296 297 if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL) 298 mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL; 299 300 /* 301 * If check_interval in MMP block is larger, use that instead of 302 * update_interval from the superblock. 303 */ 304 if (le16_to_cpu(mmp->mmp_check_interval) > mmp_check_interval) 305 mmp_check_interval = le16_to_cpu(mmp->mmp_check_interval); 306 307 seq = le32_to_cpu(mmp->mmp_seq); 308 if (seq == EXT4_MMP_SEQ_CLEAN) 309 goto skip; 310 311 if (seq == EXT4_MMP_SEQ_FSCK) { 312 dump_mmp_msg(sb, mmp, "fsck is running on the filesystem"); 313 goto failed; 314 } 315 316 wait_time = min(mmp_check_interval * 2 + 1, 317 mmp_check_interval + 60); 318 319 /* Print MMP interval if more than 20 secs. */ 320 if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4) 321 ext4_warning(sb, "MMP interval %u higher than expected, please" 322 " wait.\n", wait_time * 2); 323 324 if (schedule_timeout_interruptible(HZ * wait_time) != 0) { 325 ext4_warning(sb, "MMP startup interrupted, failing mount\n"); 326 goto failed; 327 } 328 329 retval = read_mmp_block(sb, &bh, mmp_block); 330 if (retval) 331 goto failed; 332 mmp = (struct mmp_struct *)(bh->b_data); 333 if (seq != le32_to_cpu(mmp->mmp_seq)) { 334 dump_mmp_msg(sb, mmp, 335 "Device is already active on another node."); 336 goto failed; 337 } 338 339 skip: 340 /* 341 * write a new random sequence number. 342 */ 343 seq = mmp_new_seq(); 344 mmp->mmp_seq = cpu_to_le32(seq); 345 346 retval = write_mmp_block(sb, bh); 347 if (retval) 348 goto failed; 349 350 /* 351 * wait for MMP interval and check mmp_seq. 352 */ 353 if (schedule_timeout_interruptible(HZ * wait_time) != 0) { 354 ext4_warning(sb, "MMP startup interrupted, failing mount\n"); 355 goto failed; 356 } 357 358 retval = read_mmp_block(sb, &bh, mmp_block); 359 if (retval) 360 goto failed; 361 mmp = (struct mmp_struct *)(bh->b_data); 362 if (seq != le32_to_cpu(mmp->mmp_seq)) { 363 dump_mmp_msg(sb, mmp, 364 "Device is already active on another node."); 365 goto failed; 366 } 367 368 mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL); 369 if (!mmpd_data) { 370 ext4_warning(sb, "not enough memory for mmpd_data"); 371 goto failed; 372 } 373 mmpd_data->sb = sb; 374 mmpd_data->bh = bh; 375 376 /* 377 * Start a kernel thread to update the MMP block periodically. 378 */ 379 EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s", 380 bdevname(bh->b_bdev, 381 mmp->mmp_bdevname)); 382 if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) { 383 EXT4_SB(sb)->s_mmp_tsk = NULL; 384 kfree(mmpd_data); 385 ext4_warning(sb, "Unable to create kmmpd thread for %s.", 386 sb->s_id); 387 goto failed; 388 } 389 390 return 0; 391 392 failed: 393 brelse(bh); 394 return 1; 395 } 396 397 398