ldiskfs/kernel_patches/patches/rhel6.4/ext4-mmp.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    |  354 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
  16  fs/ext4/super.c  |   18 +++-
  17  4 files changed, 447 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 @@ -1009,7 +1009,7 @@ 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 @@ -1177,6 +1177,9 @@ struct ext4_sb_info {
  48         /* workqueue for dio unwritten */
  49         struct workqueue_struct *dio_unwritten_wq;
  50
  51 +       /* Kernel thread for multiple mount protection */
  52 +       struct task_struct *s_mmp_tsk;
  53 +
  54         /* Lazy inode table initialization info */
  55         struct ext4_li_request *s_li_request;
  56         /* Wait multiplier for lazy initialization thread */
  57 @@ -1322,7 +1325,8 @@ EXT4_INODE_BIT_FNS(state, state_flags)
  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 @@ -1576,6 +1580,67 @@ struct ext4_features {
  68  };
  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 @@ -1757,6 +1822,10 @@ 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 @@ -2050,6 +2119,8 @@ 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 +1,357 @@
 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 +               brelse(*bh);
 223 +               *bh = NULL;
 224 +               return -EINVAL;
 225 +       }
 226 +
 227 +       return 0;
 228 +}
 229 +
 230 +/*
 231 + * Dump as much information as possible to help the admin.
 232 + */
 233 +void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
 234 +                   const char *function, const char *msg)
 235 +{
 236 +       __ext4_warning(sb, function, msg);
 237 +       __ext4_warning(sb, function,
 238 +                      "MMP failure info: last update time: %llu, last update "
 239 +                      "node: %s, last update device: %s\n",
 240 +                      (long long unsigned int) le64_to_cpu(mmp->mmp_time),
 241 +                      mmp->mmp_nodename, mmp->mmp_bdevname);
 242 +}
 243 +
 244 +/*
 245 + * kmmpd will update the MMP sequence every s_mmp_update_interval seconds
 246 + */
 247 +static int kmmpd(void *data)
 248 +{
 249 +       struct super_block *sb = ((struct mmpd_data *) data)->sb;
 250 +       struct buffer_head *bh = ((struct mmpd_data *) data)->bh;
 251 +       struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 252 +       struct mmp_struct *mmp;
 253 +       ext4_fsblk_t mmp_block;
 254 +       u32 seq = 0;
 255 +       unsigned long failed_writes = 0;
 256 +       int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
 257 +       unsigned mmp_check_interval;
 258 +       unsigned long last_update_time;
 259 +       unsigned long diff;
 260 +       int retval;
 261 +
 262 +       mmp_block = le64_to_cpu(es->s_mmp_block);
 263 +       mmp = (struct mmp_struct *)(bh->b_data);
 264 +       mmp->mmp_time = cpu_to_le64(get_seconds());
 265 +       /*
 266 +        * Start with the higher mmp_check_interval and reduce it if
 267 +        * the MMP block is being updated on time.
 268 +        */
 269 +       mmp_check_interval = max(EXT4_MMP_CHECK_MULT * mmp_update_interval,
 270 +                                EXT4_MMP_MIN_CHECK_INTERVAL);
 271 +       mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
 272 +       bdevname(bh->b_bdev, mmp->mmp_bdevname);
 273 +
 274 +       memcpy(mmp->mmp_nodename, init_utsname()->nodename,
 275 +              sizeof(mmp->mmp_nodename));
 276 +
 277 +       while (!kthread_should_stop()) {
 278 +               if (++seq > EXT4_MMP_SEQ_MAX)
 279 +                       seq = 1;
 280 +
 281 +               mmp->mmp_seq = cpu_to_le32(seq);
 282 +               mmp->mmp_time = cpu_to_le64(get_seconds());
 283 +               last_update_time = jiffies;
 284 +
 285 +               retval = write_mmp_block(bh);
 286 +               /*
 287 +                * Don't spew too many error messages. Print one every
 288 +                * (s_mmp_update_interval * 60) seconds.
 289 +                */
 290 +               if (retval) {
 291 +                       if ((failed_writes % 60) == 0)
 292 +                               ext4_error(sb, "Error writing to MMP block");
 293 +                       failed_writes++;
 294 +               }
 295 +
 296 +               if (!(le32_to_cpu(es->s_feature_incompat) &
 297 +                   EXT4_FEATURE_INCOMPAT_MMP)) {
 298 +                       ext4_warning(sb, "kmmpd being stopped since MMP feature"
 299 +                                    " has been disabled.");
 300 +                       EXT4_SB(sb)->s_mmp_tsk = NULL;
 301 +                       goto failed;
 302 +               }
 303 +
 304 +               if (sb->s_flags & MS_RDONLY) {
 305 +                       ext4_warning(sb, "kmmpd being stopped since filesystem "
 306 +                                    "has been remounted as readonly.");
 307 +                       EXT4_SB(sb)->s_mmp_tsk = NULL;
 308 +                       goto failed;
 309 +               }
 310 +
 311 +               diff = jiffies - last_update_time;
 312 +               if (diff < mmp_update_interval * msecs_to_jiffies(MSEC_PER_SEC))
 313 +                       schedule_timeout_interruptible(mmp_update_interval *
 314 +                               msecs_to_jiffies(MSEC_PER_SEC) - diff);
 315 +
 316 +               /*
 317 +                * We need to make sure that more than mmp_check_interval
 318 +                * seconds have not passed since writing. If that has happened
 319 +                * we need to check if the MMP block is as we left it.
 320 +                */
 321 +               diff = jiffies - last_update_time;
 322 +               if (diff > mmp_check_interval * msecs_to_jiffies(MSEC_PER_SEC)) {
 323 +                       struct buffer_head *bh_check = NULL;
 324 +                       struct mmp_struct *mmp_check;
 325 +
 326 +                       retval = read_mmp_block(sb, &bh_check, mmp_block);
 327 +                       if (retval) {
 328 +                               ext4_error(sb, "error reading MMP data: %d",
 329 +                                          retval);
 330 +                               EXT4_SB(sb)->s_mmp_tsk = NULL;
 331 +                               goto failed;
 332 +                       }
 333 +
 334 +                       mmp_check = (struct mmp_struct *)(bh_check->b_data);
 335 +                       if (mmp->mmp_seq != mmp_check->mmp_seq ||
 336 +                           memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
 337 +                                  sizeof(mmp->mmp_nodename))) {
 338 +                               dump_mmp_msg(sb, mmp_check,
 339 +                                            "Error while updating MMP info. "
 340 +                                            "The filesystem seems to have been"
 341 +                                            " multiply mounted.");
 342 +                               ext4_error(sb, "abort");
 343 +                               put_bh(bh_check);
 344 +                               goto failed;
 345 +                       }
 346 +                       put_bh(bh_check);
 347 +               }
 348 +
 349 +               /*
 350 +                * Adjust the mmp_check_interval depending on how much time
 351 +                * it took for the MMP block to be written.
 352 +                */
 353 +               mmp_check_interval = max(min(EXT4_MMP_CHECK_MULT * diff /
 354 +                                            msecs_to_jiffies(MSEC_PER_SEC),
 355 +                                            EXT4_MMP_MAX_CHECK_INTERVAL),
 356 +                                        EXT4_MMP_MIN_CHECK_INTERVAL);
 357 +               mmp->mmp_check_interval = cpu_to_le16(mmp_check_interval);
 358 +       }
 359 +
 360 +       /*
 361 +        * Unmount seems to be clean.
 362 +        */
 363 +       mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
 364 +       mmp->mmp_time = cpu_to_le64(get_seconds());
 365 +
 366 +       retval = write_mmp_block(bh);
 367 +
 368 +failed:
 369 +       kfree(data);
 370 +       brelse(bh);
 371 +       return retval;
 372 +}
 373 +
 374 +/*
 375 + * Get a random new sequence number but make sure it is not greater than
 376 + * EXT4_MMP_SEQ_MAX.
 377 + */
 378 +static unsigned int mmp_new_seq(void)
 379 +{
 380 +       u32 new_seq;
 381 +
 382 +       do {
 383 +               get_random_bytes(&new_seq, sizeof(u32));
 384 +       } while (new_seq > EXT4_MMP_SEQ_MAX);
 385 +
 386 +       return new_seq;
 387 +}
 388 +
 389 +/*
 390 + * Protect the filesystem from being mounted more than once.
 391 + */
 392 +int ext4_multi_mount_protect(struct super_block *sb,
 393 +                                   ext4_fsblk_t mmp_block)
 394 +{
 395 +       struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 396 +       struct buffer_head *bh = NULL;
 397 +       struct mmp_struct *mmp = NULL;
 398 +       struct mmpd_data *mmpd_data;
 399 +       u32 seq;
 400 +       unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval);
 401 +       unsigned int wait_time = 0;
 402 +       int retval;
 403 +
 404 +       if (mmp_block < le32_to_cpu(es->s_first_data_block) ||
 405 +           mmp_block >= ext4_blocks_count(es)) {
 406 +               ext4_warning(sb, "Invalid MMP block in superblock");
 407 +               goto failed;
 408 +       }
 409 +
 410 +       retval = read_mmp_block(sb, &bh, mmp_block);
 411 +       if (retval)
 412 +               goto failed;
 413 +
 414 +       mmp = (struct mmp_struct *)(bh->b_data);
 415 +
 416 +       if (mmp_check_interval < EXT4_MMP_MIN_CHECK_INTERVAL)
 417 +               mmp_check_interval = EXT4_MMP_MIN_CHECK_INTERVAL;
 418 +
 419 +       /*
 420 +        * If check_interval in MMP block is larger, use that instead of
 421 +        * update_interval from the superblock.
 422 +        */
 423 +       if (mmp->mmp_check_interval > mmp_check_interval)
 424 +               mmp_check_interval = mmp->mmp_check_interval;
 425 +
 426 +       seq = le32_to_cpu(mmp->mmp_seq);
 427 +       if (seq == EXT4_MMP_SEQ_CLEAN)
 428 +               goto skip;
 429 +
 430 +       if (seq == EXT4_MMP_SEQ_FSCK) {
 431 +               dump_mmp_msg(sb, mmp, "fsck is running on the filesystem");
 432 +               goto failed;
 433 +       }
 434 +
 435 +       wait_time = min(mmp_check_interval * 2 + 1,
 436 +                       mmp_check_interval + 60);
 437 +
 438 +       /* Print MMP interval if more than 20 secs. */
 439 +       if (wait_time > EXT4_MMP_MIN_CHECK_INTERVAL * 4)
 440 +               ext4_warning(sb, "MMP interval %u higher than expected, please"
 441 +                            " wait.\n", wait_time * 2);
 442 +
 443 +       if (schedule_timeout_interruptible(msecs_to_jiffies(MSEC_PER_SEC) *
 444 +                                          wait_time) != 0) {
 445 +               ext4_warning(sb, "MMP startup interrupted, failing mount\n");
 446 +               goto failed;
 447 +       }
 448 +
 449 +       retval = read_mmp_block(sb, &bh, mmp_block);
 450 +       if (retval)
 451 +               goto failed;
 452 +       mmp = (struct mmp_struct *)(bh->b_data);
 453 +       if (seq != le32_to_cpu(mmp->mmp_seq)) {
 454 +               dump_mmp_msg(sb, mmp,
 455 +                            "Device is already active on another node.");
 456 +               goto failed;
 457 +       }
 458 +
 459 +skip:
 460 +       /*
 461 +        * write a new random sequence number.
 462 +        */
 463 +       mmp->mmp_seq = seq = cpu_to_le32(mmp_new_seq());
 464 +
 465 +       retval = write_mmp_block(bh);
 466 +       if (retval)
 467 +               goto failed;
 468 +
 469 +       /*
 470 +        * wait for MMP interval and check mmp_seq.
 471 +        */
 472 +       if (schedule_timeout_interruptible(msecs_to_jiffies(MSEC_PER_SEC) *
 473 +                                          wait_time) != 0) {
 474 +               ext4_warning(sb, "MMP startup interrupted, failing mount\n");
 475 +               goto failed;
 476 +       }
 477 +
 478 +       retval = read_mmp_block(sb, &bh, mmp_block);
 479 +       if (retval)
 480 +               goto failed;
 481 +       mmp = (struct mmp_struct *)(bh->b_data);
 482 +       if (seq != le32_to_cpu(mmp->mmp_seq)) {
 483 +               dump_mmp_msg(sb, mmp,
 484 +                            "Device is already active on another node.");
 485 +               goto failed;
 486 +       }
 487 +
 488 +       mmpd_data = kmalloc(sizeof(struct mmpd_data), GFP_KERNEL);
 489 +       if (!mmpd_data) {
 490 +               ext4_warning(sb, "not enough memory for mmpd_data");
 491 +               goto failed;
 492 +       }
 493 +       mmpd_data->sb = sb;
 494 +       mmpd_data->bh = bh;
 495 +
 496 +       /*
 497 +        * Start a kernel thread to update the MMP block periodically.
 498 +        */
 499 +       EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%s",
 500 +                                            bdevname(bh->b_bdev,
 501 +                                                     mmp->mmp_bdevname));
 502 +       if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) {
 503 +               EXT4_SB(sb)->s_mmp_tsk = NULL;
 504 +               kfree(mmpd_data);
 505 +               ext4_warning(sb, "Unable to create kmmpd thread for %s.",
 506 +                            sb->s_id);
 507 +               goto failed;
 508 +       }
 509 +
 510 +       return 0;
 511 +
 512 +failed:
 513 +       brelse(bh);
 514 +       return 1;
 515 +}
 516 +
 517 Index: linux-stage/fs/ext4/super.c
 518 ===================================================================
 519 --- linux-stage.orig/fs/ext4/super.c
 520 +++ linux-stage/fs/ext4/super.c
 521 @@ -40,6 +40,8 @@
 522  #include <linux/log2.h>
 523  #include <linux/crc16.h>
 524  #include <asm/uaccess.h>
 525 +#include <linux/kthread.h>
 526 +#include <linux/utsname.h>
 527
 528  #include <linux/kthread.h>
 529  #include <linux/freezer.h>
 530 @@ -716,6 +718,8 @@ static void ext4_put_super(struct super_
 531                 invalidate_bdev(sbi->journal_bdev);
 532                 ext4_blkdev_remove(sbi);
 533         }
 534 +       if (sbi->s_mmp_tsk)
 535 +               kthread_stop(sbi->s_mmp_tsk);
 536         sb->s_fs_info = NULL;
 537         /*
 538          * Now that we are completely done shutting down the
 539 @@ -3241,6 +3245,10 @@ static int ext4_fill_super(struct super_
 540         needs_recovery = (es->s_last_orphan != 0 ||
 541                           EXT4_HAS_INCOMPAT_FEATURE(sb,
 542                                     EXT4_FEATURE_INCOMPAT_RECOVER));
 543 +       if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_MMP) &&
 544 +           !(sb->s_flags & MS_RDONLY))
 545 +               if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
 546 +                       goto failed_mount3;
 547
 548         /*
 549          * The first inode we look at is the journal inode.  Don't try
 550 @@ -3491,6 +3499,8 @@ failed_mount3:
 551         percpu_counter_destroy(&sbi->s_freeinodes_counter);
 552         percpu_counter_destroy(&sbi->s_dirs_counter);
 553         percpu_counter_destroy(&sbi->s_dirtyblocks_counter);
 554 +       if (sbi->s_mmp_tsk)
 555 +               kthread_stop(sbi->s_mmp_tsk);
 556  failed_mount2:
 557         for (i = 0; i < db_count; i++)
 558                 brelse(sbi->s_group_desc[i]);
 559 @@ -4001,7 +4011,7 @@ static int ext4_remount(struct super_blo
 560         int enable_quota = 0;
 561         ext4_group_t g;
 562         unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 563 -       int err;
 564 +       int err = 0;
 565  #ifdef CONFIG_QUOTA
 566         int i;
 567  #endif
 568 @@ -4129,6 +4139,13 @@ static int ext4_remount(struct super_blo
 569                                 goto restore_opts;
 570                         if (!ext4_setup_super(sb, es, 0))
 571                                 sb->s_flags &= ~MS_RDONLY;
 572 +                       if (EXT4_HAS_INCOMPAT_FEATURE(sb,
 573 +                                                   EXT4_FEATURE_INCOMPAT_MMP))
 574 +                               if (ext4_multi_mount_protect(sb,
 575 +                                               le64_to_cpu(es->s_mmp_block))) {
 576 +                                       err = -EROFS;
 577 +                                       goto restore_opts;
 578 +                               }
 579                         enable_quota = 1;
 580                 }
 581         }