ldiskfs/kernel_patches/patches/ext4-mmp-rhel6.patch

   1 Prevent an ext4 filesystem from being mounted multiple times.
   2 A sequence number is stored on disk and is periodically updated (every 5
   3 seconds by default) by a mounted filesystem.
   4 At mount time, we now wait for s_mmp_update_interval seconds to make sure
   5 that the MMP sequence does not change.
   6 In case of failure, the nodename, bdevname and the time at which the MMP
   7 block was last updated is displayed.
   8 Move all mmp code to a dedicated file (mmp.c).
   9
  10 Signed-off-by: Andreas Dilger <adilger <at> whamcloud.com>
  11 Signed-off-by: Johann Lombardi <johann <at> whamcloud.com>
  12 ---
  13  fs/ext4/Makefile |    3 +-
  14  fs/ext4/ext4.h   |   76 ++++++++++++-
  15  fs/ext4/mmp.c    |  351 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
  16  fs/ext4/super.c  |   18 +++-
  17  4 files changed, 444 insertions(+), 4 deletions(-)
  18  create mode 100644 fs/ext4/mmp.c
  19
  20 Index: linux-stage/fs/ext4/Makefile
  21 ===================================================================
  22 --- linux-stage.orig/fs/ext4/Makefile
  23 +++ linux-stage/fs/ext4/Makefile
  24 @@ -6,7 +6,8 @@ obj-$(CONFIG_EXT4_FS) += ext4.o
  25
  26  ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
  27                 ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
  28 -               ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o
  29 +               ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
  30 +               mmp.o
  31
  32  ext4-$(CONFIG_EXT4_FS_XATTR)           += xattr.o xattr_user.o xattr_trusted.o
  33  ext4-$(CONFIG_EXT4_FS_POSIX_ACL)       += acl.o
  34 Index: linux-stage/fs/ext4/ext4.h
  35 ===================================================================
  36 --- linux-stage.orig/fs/ext4/ext4.h
  37 +++ linux-stage/fs/ext4/ext4.h
  38 @@ -893,7 +893,7 @@ struct ext4_super_block {
  39         __le16  s_want_extra_isize;     /* New inodes should reserve # bytes */
  40         __le32  s_flags;                /* Miscellaneous flags */
  41         __le16  s_raid_stride;          /* RAID stride */
  42 -       __le16  s_mmp_interval;         /* # seconds to wait in MMP checking */
  43 +       __le16  s_mmp_update_interval;  /* # seconds to wait in MMP checking */
  44         __le64  s_mmp_block;            /* Block for multi-mount protection */
  45         __le32  s_raid_stripe_width;    /* blocks on all data disks (N*stride)*/
  46         __u8    s_log_groups_per_flex;  /* FLEX_BG group size */
  47 @@ -1040,6 +1040,9 @@ struct ext4_sb_info {
  48
  49         /* workqueue for dio unwritten */
  50         struct workqueue_struct *dio_unwritten_wq;
  51 +
  52 +       /* Kernel thread for multiple mount protection */
  53 +       struct task_struct *s_mmp_tsk;
  54
  55         /* Lazy inode table initialization info */
  56         struct ext4_li_request *s_li_request;
  57 @@ -1176,7 +1179,8 @@ static inline void ext4_clear_inode_stat
  58                                          EXT4_FEATURE_INCOMPAT_META_BG| \
  59                                          EXT4_FEATURE_INCOMPAT_EXTENTS| \
  60                                          EXT4_FEATURE_INCOMPAT_64BIT| \
  61 -                                        EXT4_FEATURE_INCOMPAT_FLEX_BG)
  62 +                                        EXT4_FEATURE_INCOMPAT_FLEX_BG| \
  63 +                                        EXT4_FEATURE_INCOMPAT_MMP)
  64  #define EXT4_FEATURE_RO_COMPAT_SUPP    (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
  65                                          EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \
  66                                          EXT4_FEATURE_RO_COMPAT_GDT_CSUM| \
  67 @@ -1383,6 +1387,67 @@ void ext4_get_group_no_and_offset(struct
  68  extern struct proc_dir_entry *ext4_proc_root;
  69
  70  /*
  71 + * This structure will be used for multiple mount protection. It will be
  72 + * written into the block number saved in the s_mmp_block field in the
  73 + * superblock. Programs that check MMP should assume that if
  74 + * SEQ_FSCK (or any unknown code above SEQ_MAX) is present then it is NOT safe
  75 + * to use the filesystem, regardless of how old the timestamp is.
  76 + */
  77 +#define EXT4_MMP_MAGIC     0x004D4D50U /* ASCII for MMP */
  78 +#define EXT4_MMP_SEQ_CLEAN 0xFF4D4D50U /* mmp_seq value for clean unmount */
  79 +#define EXT4_MMP_SEQ_FSCK  0xE24D4D50U /* mmp_seq value when being fscked */
  80 +#define EXT4_MMP_SEQ_MAX   0xE24D4D4FU /* maximum valid mmp_seq value */
  81 +
  82 +struct mmp_struct {
  83 +       __le32  mmp_magic;              /* Magic number for MMP */
  84 +       __le32  mmp_seq;                /* Sequence no. updated periodically */
  85 +
  86 +       /*
  87 +        * mmp_time, mmp_nodename & mmp_bdevname are only used for information
  88 +        * purposes and do not affect the correctness of the algorithm
  89 +        */
  90 +       __le64  mmp_time;               /* Time last updated */
  91 +       char    mmp_nodename[64];       /* Node which last updated MMP block */
  92 +       char    mmp_bdevname[32];       /* Bdev which last updated MMP block */
  93 +
  94 +       /*
  95 +        * mmp_check_interval is used to verify if the MMP block has been
  96 +        * updated on the block device. The value is updated based on the
  97 +        * maximum time to write the MMP block during an update cycle.
  98 +        */
  99 +       __le16  mmp_check_interval;
 100 +
 101 +       __le16  mmp_pad1;
 102 +       __le32  mmp_pad2[227];
 103 +};
 104 +
 105 +/* arguments passed to the mmp thread */
 106 +struct mmpd_data {
 107 +       struct buffer_head *bh; /* bh from initial read_mmp_block() */
 108 +       struct super_block *sb;  /* super block of the fs */
 109 +};
 110 +
 111 +/*
 112 + * Check interval multiplier
 113 + * The MMP block is written every update interval and initially checked every
 114 + * update interval x the multiplier (the value is then adapted based on the
 115 + * write latency). The reason is that writes can be delayed under load and we
 116 + * don't want readers to incorrectly assume that the filesystem is no longer
 117 + * in use.
 118 + */
 119 +#define EXT4_MMP_CHECK_MULT            2UL
 120 +
 121 +/*
 122 + * Minimum interval for MMP checking in seconds.
 123 + */
 124 +#define EXT4_MMP_MIN_CHECK_INTERVAL    5UL
 125 +
 126 +/*
 127 + * Maximum interval for MMP checking in seconds.
 128 + */
 129 +#define EXT4_MMP_MAX_CHECK_INTERVAL    300UL
 130 +
 131 +/*
 132   * Function prototypes
 133   */
 134
 135 @@ -1552,6 +1617,10 @@ extern void __ext4_warning(struct super_
 136  #define ext4_warning(sb, message...)   __ext4_warning(sb, __func__, ## message)
 137  extern void ext4_msg(struct super_block *, const char *, const char *, ...)
 138         __attribute__ ((format (printf, 3, 4)));
 139 +extern void __dump_mmp_msg(struct super_block *, struct mmp_struct *mmp,
 140 +                          const char *, const char *);
 141 +#define dump_mmp_msg(sb, mmp, msg)     __dump_mmp_msg(sb, mmp, __func__, \
 142 +                                                      msg)
 143  extern void ext4_grp_locked_error(struct super_block *, ext4_group_t,
 144                                 const char *, const char *, ...)
 145         __attribute__ ((format (printf, 4, 5)));
 146 @@ -1833,6 +1902,8 @@ extern int ext4_move_extents(struct file
 147                              __u64 start_orig, __u64 start_donor,
 148                              __u64 len, __u64 *moved_len);
 149
 150 +/* mmp.c */
 151 +extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);
 152
 153  /*
 154   * Add new method to test wether block and inode bitmaps are properly
 155 Index: linux-stage/fs/ext4/mmp.c
 156 ===================================================================
 157 --- /dev/null
 158 +++ linux-stage/fs/ext4/mmp.c
 159 @@ -0,0 +1,351 @@
 160 +#include <linux/fs.h>
 161 +#include <linux/random.h>
 162 +#include <linux/buffer_head.h>
 163 +#include <linux/utsname.h>
 164 +#include <linux/kthread.h>
 165 +
 166 +#include "ext4.h"
 167 +
 168 +/*
 169 + * Write the MMP block using WRITE_SYNC to try to get the block on-disk
 170 + * faster.
 171 + */
 172 +static int write_mmp_block(struct buffer_head *bh)
 173 +{
 174 +       mark_buffer_dirty(bh);
 175 +       lock_buffer(bh);
 176 +       bh->b_end_io = end_buffer_write_sync;
 177 +       get_bh(bh);
 178 +       submit_bh(WRITE_SYNC, bh);
 179 +       wait_on_buffer(bh);
 180 +       if (unlikely(!buffer_uptodate(bh)))
 181 +               return 1;
 182 +
 183 +       return 0;
 184 +}
 185 +
 186 +/*
 187 + * Read the MMP block. It _must_ be read from disk and hence we clear the
 188 + * uptodate flag on the buffer.
 189 + */
 190 +static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
 191 +                         ext4_fsblk_t mmp_block)
 192 +{
 193 +       struct mmp_struct *mmp;
 194 +
 195 +       if (*bh)
 196 +               clear_buffer_uptodate(*bh);
 197 +
 198 +       /* This would be sb_bread(sb, mmp_block), except we need to be sure
 199 +        * that the MD RAID device cache has been bypassed, and that the read
 200 +        * is not blocked in the elevator. */
 201 +       if (!*bh)
 202 +               *bh = sb_getblk(sb, mmp_block);
 203 +       if (*bh) {
 204 +               get_bh(*bh);
 205 +               lock_buffer(*bh);
 206 +               (*bh)->b_end_io = end_buffer_read_sync;
 207 +               submit_bh(READ_SYNC, *bh);
 208 +               wait_on_buffer(*bh);
 209 +               if (!buffer_uptodate(*bh)) {
 210 +                       brelse(*bh);
 211 +                       *bh = NULL;
 212 +               }
 213 +       }
 214 +       if (!*bh) {
 215 +               ext4_warning(sb, "Error while reading MMP block %llu",
 216 +                            mmp_block);
 217 +               return -EIO;
 218 +       }
 219 +
 220 +       mmp = (struct mmp_struct *)((*bh)->b_data);
 221 +       if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC)
 222 +               return -EINVAL;
 223 +
 224 +       return 0;
 225 +}
 226 +
 227 +/*
 228 + * Dump as much information as possible to help the admin.
 229 + */
 230 +void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
 231 +                   const char *function, const char *msg)
 232 +{
 233 +       __ext4_warning(sb, function, msg);
 234 +       __ext4_warning(sb, function,
 235 +                      "MMP failure info: last update time: %llu, last update "
 236 +                      "node: %s, last update device: %s\n",
 237 +                      (long long unsigned int) le64_to_cpu(mmp->mmp_time),
 238 +                      mmp->mmp_nodename, mmp->mmp_bdevname);
 239 +}
 240 +
 241 +/*
 242 + * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
 243 + */
 244 +static int kmmpd(void *data)
 245 +{
 246 +       struct super_block *sb = ((struct mmpd_data *) data)->sb;
 247 +       struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
 248 +       struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 249 +       struct mmp_struct *mmp;
 250 +       ext4_fsblk_t mmp_block;
 251 +       u32 seq = 0;
 252 +       unsigned long failed_writes = 0;
 253 +       int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
 254 +       unsigned mmp_check_interval;
 255 +       unsigned long last_update_time;
 256 +       unsigned long diff;
 257 +       int retval;
 258 +
 259 +       mmp_block = le64_to_cpu(es->s_mmp_block);
 260 +       mmp = (struct mmp_struct *)(bh->b_data);
 261 +       mmp->mmp_time = cpu_to_le64(get_seconds());
 262 +       /*
 263 +        * Start with the higher mmp_check_interval and reduce it if
 264 +        * the MMP block is being updated on time.
 265 +        */
 266 +       mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
 267 +                                EXT4_MMP_MIN_CHECK_INTERVAL);
 268 +       mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
 269 +       bdevname(bh->b_bdev, mmp->mmp_bdevname);
 270 +
 271 +       memcpy(mmp->mmp_nodename, init_utsname()->nodename,
 272 +              sizeof(mmp->mmp_nodename));
 273 +
 274 +       while (!kthread_should_stop()) {
 275 +               if (++seq > EXT4_MMP_SEQ_MAX)
 276 +                       seq = 1;
 277 +
 278 +               mmp->mmp_seq = cpu_to_le32(seq);
 279 +               mmp->mmp_time = cpu_to_le64(get_seconds());
 280 +               last_update_time = jiffies;
 281 +
 282 +               retval = write_mmp_block(bh);
 283 +               /*
 284 +                * Don't spew too many error messages. Print one every
 285 +                * (s_mmp_update_interval * 60) seconds.
 286 +                */
 287 +               if (retval && (failed_writes % 60) == 0) {
 288 +                       ext4_error(sb, "Error writing to MMP block");
 289 +                       failed_writes++;
 290 +               }
 291 +
 292 +               if (!(le32_to_cpu(es->s_feature_incompat) &
 293 +                   EXT4_FEATURE_INCOMPAT_MMP)) {
 294 +                       ext4_warning(sb, "kmmpd being stopped since MMP feature"
 295 +                                    " has been disabled.");
 296 +                       EXT4_SB(sb)->s_mmp_tsk = NULL;
 297 +                       goto failed;
 298 +               }
 299 +
 300 +               if (sb->s_flags & MS_RDONLY) {
 301 +                       ext4_warning(sb, "kmmpd being stopped since filesystem "
 302 +                                    "has been remounted as readonly.");
 303 +                       EXT4_SB(sb)->s_mmp_tsk = NULL;
 304 +                       goto failed;
 305 +               }
 306 +
 307 +               diff = jiffies - last_update_time;
 308 +               if (diff < mmp_update_interval * HZ)
 309 +                       schedule_timeout_interruptible(mmp_update_interval *
 310 +                                                      HZ - diff);
 311 +
 312 +               /*
 313 +                * We need to make sure that more than mmp_check_interval
 314 +                * seconds have not passed since writing. If that has happened
 315 +                * we need to check if the MMP block is as we left it.
 316 +                */
 317 +               diff = jiffies - last_update_time;
 318 +               if (diff > mmp_check_interval * HZ) {
 319 +                       struct buffer_head *bh_check = NULL;
 320 +                       struct mmp_struct *mmp_check;
 321 +
 322 +                       retval = read_mmp_block(sb, &bh_check, mmp_block);
 323 +                       if (retval) {
 324 +                               ext4_error(sb, "error reading MMP data: %d",
 325 +                                          retval);
 326 +
 327 +                               EXT4_SB(sb)->s_mmp_tsk = NULL;
 328 +                               goto failed;
 329 +                       }
 330 +
 331 +                       mmp_check = (struct mmp_struct *)(bh_check->b_data);
 332 +                       if (mmp->mmp_seq != mmp_check->mmp_seq ||
 333 +                           memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
 334 +                                  sizeof(mmp->mmp_nodename))) {
 335 +                               dump_mmp_msg(sb, mmp_check,
 336 +                                            "Error while updating MMP info. "
 337 +                                            "The filesystem seems to have been"
 338 +                                            " multiply mounted.");
 339 +                               ext4_error(sb, "abort");
 340 +                               goto failed;
 341 +                       }
 342 +                       put_bh(bh_check);
 343 +               }
 344 +
 345 +                /*
 346 +                * Adjust the mmp_check_interval depending on how much time
 347 +                * it took for the MMP block to be written.
 348 +                */
 349 +               mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff / HZ,
 350 +                                            EXT4_MMP_MAX_CHECK_INTERVAL),
 351 +                                        EXT4_MMP_MIN_CHECK_INTERVAL);
 352 +               mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
 353 +       }
 354 +
 355 +       /*
 356 +        * Unmount seems to be clean.
 357 +        */
 358 +       mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
 359 +       mmp->mmp_time = cpu_to_le64(get_seconds());
 360 +
 361 +       retval = write_mmp_block(bh);
 362 +
 363 +failed:
 364 +       kfree(data);
 365 +       brelse(bh);
 366 +       return retval;
 367 +}
 368 +
 369 +/*
 370 + * Get a random new sequence number but make sure it is not greater than
 371 + * EXT4_MMP_SEQ_MAX.
 372 + */
 373 +static unsigned int mmp_new_seq(void)
 374 +{
 375 +       u32 new_seq;
 376 +
 377 +       do {
 378 +               get_random_bytes(&new_seq, sizeof(u32));
 379 +       } while (new_seq > EXT4_MMP_SEQ_MAX);
 380 +
 381 +       return new_seq;
 382 +}
 383 +
 384 +/*
 385 + * Protect the filesystem from being mounted more than once.
 386 + */
 387 +int ext4_multi_mount_protect(struct super_block *sb,
 388 +                                   ext4_fsblk_t mmp_block)
 389 +{
 390 +       struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 391 +       struct buffer_head *bh = NULL;
 392 +       struct mmp_struct *mmp = NULL;
 393 +       struct mmpd_data *mmpd_data;
 394 +       u32 seq;
 395 +       unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
 396 +       unsigned int wait_time = 0;
 397 +       int retval;
 398 +
 399 +       if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
 400 +           mmp_block >= ext4_blocks_count(es)) {
 401 +               ext4_warning(sb, "Invalid MMP block in superblock");
 402 +               goto failed;
 403 +       }
 404 +
 405 +       retval = read_mmp_block(sb, &bh, mmp_block);
 406 +       if (retval)
 407 +               goto failed;
 408 +
 409 +       mmp = (struct mmp_struct *)(bh->b_data);
 410 +
 411 +       if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
 412 +               mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
 413 +
 414 +       /*
 415 +        * If check_interval in MMP block is larger, use that instead of
 416 +        * update_interval from the superblock.
 417 +        */
 418 +       if (mmp->mmp_check_interval > mmp_check_interval)
 419 +               mmp_check_interval = mmp->mmp_check_interval;
 420 +
 421 +       seq = le32_to_cpu(mmp->mmp_seq);
 422 +       if (seq == EXT4_MMP_SEQ_CLEAN)
 423 +               goto skip;
 424 +
 425 +       if (seq == EXT4_MMP_SEQ_FSCK) {
 426 +               dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
 427 +               goto failed;
 428 +       }
 429 +
 430 +       wait_time = min(mmp_check_interval * 2 + 1,
 431 +                       mmp_check_interval + 60);
 432 +
 433 +       /* Print MMP interval if more than 20 secs. */
 434 +       if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
 435 +               ext4_warning(sb, "MMP interval %u higher than expected, please"
 436 +                            " wait.\n", wait_time * 2);
 437 +
 438 +       if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
 439 +               ext4_warning(sb, "MMP startup interrupted, failing mount\n");
 440 +               goto failed;
 441 +       }
 442 +
 443 +       retval = read_mmp_block(sb, &bh, mmp_block);
 444 +       if (retval)
 445 +               goto failed;
 446 +       mmp = (struct mmp_struct *)(bh->b_data);
 447 +       if (seq != le32_to_cpu(mmp->mmp_seq)) {
 448 +               dump_mmp_msg(sb, mmp,
 449 +                            "Device is already active on another node.");
 450 +               goto failed;
 451 +       }
 452 +
 453 +skip:
 454 +       /*
 455 +        * write a new random sequence number.
 456 +        */
 457 +       mmp->mmp_seq = seq = cpu_to_le32(mmp_new_seq());
 458 +
 459 +       retval = write_mmp_block(bh);
 460 +       if (retval)
 461 +               goto failed;
 462 +
 463 +       /*
 464 +        * wait for MMP interval and check mmp_seq.
 465 +        */
 466 +       if (schedule_timeout_interruptible(HZ * wait_time) != 0) {
 467 +               ext4_warning(sb, "MMP startup interrupted, failing mount\n");
 468 +               goto failed;
 469 +       }
 470 +
 471 +       retval = read_mmp_block(sb, &bh, mmp_block);
 472 +       if (retval)
 473 +               goto failed;
 474 +       mmp = (struct mmp_struct *)(bh->b_data);
 475 +       if (seq != le32_to_cpu(mmp->mmp_seq)) {
 476 +               dump_mmp_msg(sb, mmp,
 477 +                            "Device is already active on another node.");
 478 +               goto failed;
 479 +       }
 480 +
 481 +       mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
 482 +       if (!mmpd_data) {
 483 +               ext4_warning(sb, "not enough memory for mmpd_data");
 484 +               goto failed;
 485 +       }
 486 +       mmpd_data->sb = sb;
 487 +       mmpd_data->bh = bh;
 488 +
 489 +       /*
 490 +        * Start a kernel thread to update the MMP block periodically.
 491 +        */
 492 +       EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
 493 +                                            bdevname(bh->b_bdev,
 494 +                                                     mmp->mmp_bdevname));
 495 +       if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
 496 +               EXT4_SB(sb)->s_mmp_tsk = NULL;
 497 +               kfree(mmpd_data);
 498 +               ext4_warning(sb, "Unable to create kmmpd thread for %s.",
 499 +                            sb->s_id);
 500 +               goto failed;
 501 +       }
 502 +
 503 +       return 0;
 504 +
 505 +failed:
 506 +       brelse(bh);
 507 +       return 1;
 508 +}
 509 +
 510 +
 511 Index: linux-stage/fs/ext4/super.c
 512 ===================================================================
 513 --- linux-stage.orig/fs/ext4/super.c
 514 +++ linux-stage/fs/ext4/super.c
 515 @@ -40,6 +40,8 @@
 516  #include <linux/log2.h>
 517  #include <linux/crc16.h>
 518  #include <asm/uaccess.h>
 519 +#include <linux/kthread.h>
 520 +#include <linux/utsname.h>
 521
 522  #include "ext4.h"
 523  #include "ext4_jbd2.h"
 524 @@ -700,6 +702,8 @@ static void ext4_put_super(struct super_
 525                 invalidate_bdev(sbi->journal_bdev);
 526                 ext4_blkdev_remove(sbi);
 527         }
 528 +       if (sbi->s_mmp_tsk)
 529 +               kthread_stop(sbi->s_mmp_tsk);
 530         sb->s_fs_info = NULL;
 531         /*
 532          * Now that we are completely done shutting down the
 533 @@ -2799,6 +2803,10 @@ static int ext4_fill_super(struct super_
 534         needs_recovery = (es->s_last_orphan != 0 ||
 535                           EXT4_HAS_INCOMPAT_FEATURE(sb,
 536                                     EXT4_FEATURE_INCOMPAT_RECOVER));
 537 +       if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_MMP) &&
 538 +           !(sb->s_flags & MS_RDONLY))
 539 +               if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
 540 +                       goto failed_mount3;
 541
 542         /*
 543          * The first inode we look at is the journal inode.  Don't try
 544 @@ -3036,6 +3044,8 @@ failed_mount3:
 545         percpu_counter_destroy(&sbi->s_freeinodes_counter);
 546         percpu_counter_destroy(&sbi->s_dirs_counter);
 547         percpu_counter_destroy(&sbi->s_dirtyblocks_counter);
 548 +       if (sbi->s_mmp_tsk)
 549 +               kthread_stop(sbi->s_mmp_tsk);
 550  failed_mount2:
 551         for (i = 0; i < db_count; i++)
 552                 brelse(sbi->s_group_desc[i]);
 553 @@ -3544,7 +3554,7 @@ static int ext4_remount(struct super_blo
 554         struct ext4_mount_options old_opts;
 555         ext4_group_t g;
 556         unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 557 -       int err;
 558 +       int err = 0;
 559  #ifdef CONFIG_QUOTA
 560         int i;
 561  #endif
 562 @@ -3666,6 +3676,13 @@ static int ext4_remount(struct super_blo
 563                                 goto restore_opts;
 564                         if (!ext4_setup_super(sb, es, 0))
 565                                 sb->s_flags &= ~MS_RDONLY;
 566 +                       if (EXT4_HAS_INCOMPAT_FEATURE(sb,
 567 +                                                   EXT4_FEATURE_INCOMPAT_MMP))
 568 +                               if (ext4_multi_mount_protect(sb,
 569 +                                               le64_to_cpu(es->s_mmp_block))) {
 570 +                                       err = -EROFS;
 571 +                                       goto restore_opts;
 572 +                               }
 573                 }
 574         }
 575         ext4_setup_system_zone(sb);