lustre/kernel_patches/patches/jbd-journal-chksum-2.6-sles10.patch

   1 Index: linux-2.6.16.53-0.16/fs/jbd/commit.c
   2 ===================================================================
   3 --- linux-2.6.16.53-0.16.orig/fs/jbd/commit.c
   4 +++ linux-2.6.16.53-0.16/fs/jbd/commit.c
   5 @@ -22,6 +22,7 @@
   6  #include <linux/pagemap.h>
   7  #include <linux/smp_lock.h>
   8  #include <linux/jiffies.h>
   9 +#include <linux/crc32.h>
  10
  11  /*
  12   * Default IO end handler for temporary BJ_IO buffer_heads.
  13 @@ -94,19 +95,23 @@ static int inverted_lock(journal_t *jour
  14         return 1;
  15  }
  16
  17 -/* Done it all: now write the commit record.  We should have
  18 +/*
  19 + * Done it all: now submit the commit record.  We should have
  20   * cleaned up our previous buffers by now, so if we are in abort
  21   * mode we can now just skip the rest of the journal write
  22   * entirely.
  23   *
  24   * Returns 1 if the journal needs to be aborted or 0 on success
  25   */
  26 -static int journal_write_commit_record(journal_t *journal,
  27 -                                       transaction_t *commit_transaction)
  28 +static int journal_submit_commit_record(journal_t *journal,
  29 +                                       transaction_t *commit_transaction,
  30 +                                       struct buffer_head **cbh,
  31 +                                       __u32 crc32_sum)
  32  {
  33         struct journal_head *descriptor;
  34 +       struct commit_header *tmp;
  35         struct buffer_head *bh;
  36 -       int i, ret;
  37 +       int ret;
  38         int barrier_done = 0;
  39
  40         if (is_journal_aborted(journal))
  41 @@ -118,21 +123,35 @@ static int journal_write_commit_record(j
  42
  43         bh = jh2bh(descriptor);
  44
  45 -       /* AKPM: buglet - add `i' to tmp! */
  46 -       for (i = 0; i < bh->b_size; i += 512) {
  47 -               journal_header_t *tmp = (journal_header_t*)bh->b_data;
  48 -               tmp->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
  49 -               tmp->h_blocktype = cpu_to_be32(JFS_COMMIT_BLOCK);
  50 -               tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
  51 +       tmp = (struct commit_header *)bh->b_data;
  52 +       tmp->h_magic = cpu_to_be32(JFS_MAGIC_NUMBER);
  53 +       tmp->h_blocktype = cpu_to_be32(JFS_COMMIT_BLOCK);
  54 +       tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
  55 +
  56 +       if (JFS_HAS_COMPAT_FEATURE(journal,
  57 +                               JFS_FEATURE_COMPAT_CHECKSUM)) {
  58 +               tmp->h_chksum_type      = JFS_CRC32_CHKSUM;
  59 +               tmp->h_chksum_size      = JFS_CRC32_CHKSUM_SIZE;
  60 +               tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
  61         }
  62
  63 -       JBUFFER_TRACE(descriptor, "write commit block");
  64 +       JBUFFER_TRACE(descriptor, "submit commit block");
  65 +       lock_buffer(bh);
  66 +       get_bh(bh);
  67 +
  68         set_buffer_dirty(bh);
  69 -       if (journal->j_flags & JFS_BARRIER) {
  70 +       set_buffer_uptodate(bh);
  71 +       bh->b_end_io = journal_end_buffer_io_sync;
  72 +
  73 +       if (journal->j_flags & JFS_BARRIER &&
  74 +               !JFS_HAS_INCOMPAT_FEATURE(journal,
  75 +                                        JFS_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
  76 +
  77                 set_buffer_ordered(bh);
  78                 barrier_done = 1;
  79         }
  80 -       ret = sync_dirty_buffer(bh);
  81 +       ret = submit_bh(WRITE, bh);
  82 +
  83         /* is it possible for another commit to fail at roughly
  84          * the same time as this one?  If so, we don't want to
  85          * trust the barrier flag in the super, but instead want
  86 @@ -153,12 +172,84 @@ static int journal_write_commit_record(j
  87                 clear_buffer_ordered(bh);
  88                 set_buffer_uptodate(bh);
  89                 set_buffer_dirty(bh);
  90 -               ret = sync_dirty_buffer(bh);
  91 +               ret = submit_bh(WRITE, bh);
  92         }
  93 -       put_bh(bh);             /* One for getblk() */
  94 -       journal_put_journal_head(descriptor);
  95 +       *cbh = bh;
  96 +       return ret;
  97 +}
  98
  99 -       return (ret == -EIO);
 100 +/*
 101 + * This function along with journal_submit_commit_record
 102 + * allows to write the commit record asynchronously.
 103 + */
 104 +static int journal_wait_on_commit_record(struct buffer_head *bh)
 105 +{
 106 +       int ret = 0;
 107 +
 108 +       clear_buffer_dirty(bh);
 109 +       wait_on_buffer(bh);
 110 +
 111 +       if (unlikely(!buffer_uptodate(bh)))
 112 +               ret = -EIO;
 113 +       put_bh(bh);            /* One for getblk() */
 114 +       journal_put_journal_head(bh2jh(bh));
 115 +
 116 +       return ret;
 117 +}
 118 +
 119 +/*
 120 + * Wait for all submitted IO to complete.
 121 + */
 122 +static int journal_wait_on_locked_list(journal_t *journal,
 123 +                                      transaction_t *commit_transaction)
 124 +{
 125 +       int ret = 0;
 126 +       struct journal_head *jh;
 127 +
 128 +       while (commit_transaction->t_locked_list) {
 129 +               struct buffer_head *bh;
 130 +
 131 +               jh = commit_transaction->t_locked_list->b_tprev;
 132 +               bh = jh2bh(jh);
 133 +               get_bh(bh);
 134 +               if (buffer_locked(bh)) {
 135 +                       spin_unlock(&journal->j_list_lock);
 136 +                       wait_on_buffer(bh);
 137 +                       if (unlikely(!buffer_uptodate(bh)))
 138 +                               ret = -EIO;
 139 +                       spin_lock(&journal->j_list_lock);
 140 +               }
 141 +               if (!inverted_lock(journal, bh)) {
 142 +                       put_bh(bh);
 143 +                       spin_lock(&journal->j_list_lock);
 144 +                       continue;
 145 +               }
 146 +               if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
 147 +                       __journal_unfile_buffer(jh);
 148 +                       jbd_unlock_bh_state(bh);
 149 +                       journal_remove_journal_head(bh);
 150 +                       put_bh(bh);
 151 +               } else {
 152 +                       jbd_unlock_bh_state(bh);
 153 +               }
 154 +               put_bh(bh);
 155 +               cond_resched_lock(&journal->j_list_lock);
 156 +       }
 157 +       return ret;
 158 +}
 159 +
 160 +static inline __u32 jbd_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 161 +{
 162 +       struct page *page = bh->b_page;
 163 +       char *addr;
 164 +       __u32 checksum;
 165 +
 166 +       addr = kmap_atomic(page, KM_USER0);
 167 +       checksum = crc32_be(crc32_sum,
 168 +                           (void *)(addr + offset_in_page(bh->b_data)),
 169 +                           bh->b_size);
 170 +       kunmap_atomic(addr, KM_USER0);
 171 +       return checksum;
 172  }
 173
 174  /*
 175 @@ -184,6 +275,8 @@ void journal_commit_transaction(journal_
 176         int first_tag = 0;
 177         int tag_flag;
 178         int i;
 179 +       struct buffer_head *cbh = NULL; /* For transactional checksums */
 180 +       __u32 crc32_sum = ~0;
 181
 182         /*
 183          * First job: lock down the current transaction and wait for
 184 @@ -395,37 +488,14 @@ write_out_data:
 185         }
 186
 187         /*
 188 -        * Wait for all previously submitted IO to complete.
 189 +        * Wait for all previously submitted IO to complete if commit
 190 +        * record is to be written synchronously.
 191          */
 192 -       while (commit_transaction->t_locked_list) {
 193 -               struct buffer_head *bh;
 194 +       if (!JFS_HAS_INCOMPAT_FEATURE(journal,
 195 +               JFS_FEATURE_INCOMPAT_ASYNC_COMMIT))
 196 +               err = journal_wait_on_locked_list(journal,
 197 +                                                 commit_transaction);
 198
 199 -               jh = commit_transaction->t_locked_list->b_tprev;
 200 -               bh = jh2bh(jh);
 201 -               get_bh(bh);
 202 -               if (buffer_locked(bh)) {
 203 -                       spin_unlock(&journal->j_list_lock);
 204 -                       wait_on_buffer(bh);
 205 -                       if (unlikely(!buffer_uptodate(bh)))
 206 -                               err = -EIO;
 207 -                       spin_lock(&journal->j_list_lock);
 208 -               }
 209 -               if (!inverted_lock(journal, bh)) {
 210 -                       put_bh(bh);
 211 -                       spin_lock(&journal->j_list_lock);
 212 -                       continue;
 213 -               }
 214 -               if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
 215 -                       __journal_unfile_buffer(jh);
 216 -                       jbd_unlock_bh_state(bh);
 217 -                       journal_remove_journal_head(bh);
 218 -                       put_bh(bh);
 219 -               } else {
 220 -                       jbd_unlock_bh_state(bh);
 221 -               }
 222 -               put_bh(bh);
 223 -               cond_resched_lock(&journal->j_list_lock);
 224 -       }
 225         spin_unlock(&journal->j_list_lock);
 226
 227         if (err)
 228 @@ -598,6 +668,16 @@ write_out_data:
 229  start_journal_io:
 230                         for (i = 0; i < bufs; i++) {
 231                                 struct buffer_head *bh = wbuf[i];
 232 +                               /*
 233 +                                * Compute checksum.
 234 +                                */
 235 +                               if (JFS_HAS_COMPAT_FEATURE(journal,
 236 +                                       JFS_FEATURE_COMPAT_CHECKSUM)) {
 237 +                                       crc32_sum =
 238 +                                               jbd_checksum_data(crc32_sum,
 239 +                                                                  bh);
 240 +                               }
 241 +
 242                                 lock_buffer(bh);
 243                                 clear_buffer_dirty(bh);
 244                                 set_buffer_uptodate(bh);
 245 @@ -614,6 +694,23 @@ start_journal_io:
 246                 }
 247         }
 248
 249 +       /* Done it all: now write the commit record asynchronously. */
 250 +
 251 +       if (JFS_HAS_INCOMPAT_FEATURE(journal,
 252 +               JFS_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 253 +               err = journal_submit_commit_record(journal, commit_transaction,
 254 +                                                &cbh, crc32_sum);
 255 +               if (err)
 256 +                       __journal_abort_hard(journal);
 257 +
 258 +               spin_lock(&journal->j_list_lock);
 259 +               err = journal_wait_on_locked_list(journal,
 260 +                                               commit_transaction);
 261 +               spin_unlock(&journal->j_list_lock);
 262 +               if (err)
 263 +                       __journal_abort_hard(journal);
 264 +       }
 265 +
 266         /* Lo and behold: we have just managed to send a transaction to
 267             the log.  Before we can commit it, wait for the IO so far to
 268             complete.  Control buffers being written are on the
 269 @@ -712,9 +809,15 @@ wait_for_iobuf:
 270         }
 271
 272         jbd_debug(3, "JBD: commit phase 6\n");
 273 -
 274 -       if (journal_write_commit_record(journal, commit_transaction))
 275 -               err = -EIO;
 276 +
 277 +       if (!JFS_HAS_INCOMPAT_FEATURE(journal,
 278 +               JFS_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 279 +               err = journal_submit_commit_record(journal, commit_transaction,
 280 +                                               &cbh, crc32_sum);
 281 +               if (err)
 282 +                       __journal_abort_hard(journal);
 283 +       }
 284 +       err = journal_wait_on_commit_record(cbh);
 285
 286         if (err)
 287                 __journal_abort_hard(journal);
 288 Index: linux-2.6.16.53-0.16/include/linux/jbd.h
 289 ===================================================================
 290 --- linux-2.6.16.53-0.16.orig/include/linux/jbd.h
 291 +++ linux-2.6.16.53-0.16/include/linux/jbd.h
 292 @@ -142,6 +142,29 @@ typedef struct journal_header_s
 293         __be32          h_sequence;
 294  } journal_header_t;
 295
 296 +/*
 297 + * Checksum types.
 298 + */
 299 +#define JFS_CRC32_CHKSUM   1
 300 +#define JFS_MD5_CHKSUM     2
 301 +#define JFS_SHA1_CHKSUM    3
 302 +
 303 +#define JFS_CRC32_CHKSUM_SIZE 4
 304 +
 305 +#define JFS_CHECKSUM_BYTES (32 / sizeof(u32))
 306 +/*
 307 + * Commit block header for storing transactional checksums:
 308 + */
 309 +struct commit_header
 310 +{
 311 +       __be32          h_magic;
 312 +       __be32          h_blocktype;
 313 +       __be32          h_sequence;
 314 +       unsigned char   h_chksum_type;
 315 +       unsigned char   h_chksum_size;
 316 +       unsigned char   h_padding[2];
 317 +       __be32          h_chksum[JFS_CHECKSUM_BYTES];
 318 +};
 319
 320  /*
 321   * The block tag: used to describe a single buffer in the journal
 322 @@ -228,12 +251,16 @@ typedef struct journal_superblock_s
 323         ((j)->j_format_version >= 2 &&                                  \
 324          ((j)->j_superblock->s_feature_incompat & cpu_to_be32((mask))))
 325
 326 -#define JFS_FEATURE_INCOMPAT_REVOKE    0x00000001
 327 +#define JFS_FEATURE_COMPAT_CHECKSUM    0x00000001
 328 +
 329 +#define JFS_FEATURE_INCOMPAT_REVOKE            0x00000001
 330 +#define JFS_FEATURE_INCOMPAT_ASYNC_COMMIT      0x00000004
 331
 332  /* Features known to this kernel version: */
 333 -#define JFS_KNOWN_COMPAT_FEATURES      0
 334 +#define JFS_KNOWN_COMPAT_FEATURES      JFS_FEATURE_COMPAT_CHECKSUM
 335  #define JFS_KNOWN_ROCOMPAT_FEATURES    0
 336 -#define JFS_KNOWN_INCOMPAT_FEATURES    JFS_FEATURE_INCOMPAT_REVOKE
 337 +#define JFS_KNOWN_INCOMPAT_FEATURES    (JFS_FEATURE_INCOMPAT_REVOKE | \
 338 +                                       JFS_FEATURE_INCOMPAT_ASYNC_COMMIT)
 339
 340  #ifdef __KERNEL__
 341
 342 @@ -1041,6 +1068,8 @@ extern int           journal_check_available_fe
 343                    (journal_t *, unsigned long, unsigned long, unsigned long);
 344  extern int        journal_set_features
 345                    (journal_t *, unsigned long, unsigned long, unsigned long);
 346 +extern int        journal_clear_features
 347 +                  (journal_t *, unsigned long, unsigned long, unsigned long);
 348  extern int        journal_create     (journal_t *);
 349  extern int        journal_load       (journal_t *journal);
 350  extern void       journal_destroy    (journal_t *);
 351 Index: linux-2.6.16.53-0.16/fs/jbd/recovery.c
 352 ===================================================================
 353 --- linux-2.6.16.53-0.16.orig/fs/jbd/recovery.c
 354 +++ linux-2.6.16.53-0.16/fs/jbd/recovery.c
 355 @@ -21,6 +21,7 @@
 356  #include <linux/jbd.h>
 357  #include <linux/errno.h>
 358  #include <linux/slab.h>
 359 +#include <linux/crc32.h>
 360  #endif
 361
 362  /*
 363 @@ -307,6 +308,37 @@ int journal_skip_recovery(journal_t *jou
 364         return err;
 365  }
 366
 367 +/*
 368 + * calc_chksums calculates the checksums for the blocks described in the
 369 + * descriptor block.
 370 + */
 371 +static int calc_chksums(journal_t *journal, struct buffer_head *bh,
 372 +                      unsigned long *next_log_block, __u32 *crc32_sum)
 373 +{
 374 +       int i, num_blks, err;
 375 +       unsigned long io_block;
 376 +       struct buffer_head *obh;
 377 +
 378 +       num_blks = count_tags(bh, journal->j_blocksize);
 379 +       /* Calculate checksum of the descriptor block. */
 380 +       *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
 381 +
 382 +       for (i = 0; i < num_blks; i++) {
 383 +               io_block = (*next_log_block)++;
 384 +               wrap(journal, *next_log_block);
 385 +               err = jread(&obh, journal, io_block);
 386 +               if (err) {
 387 +                       printk(KERN_ERR "JBD: IO error %d recovering block "
 388 +                               "%lu in log\n", err, io_block);
 389 +                       return 1;
 390 +               } else {
 391 +                       *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
 392 +                                    obh->b_size);
 393 +               }
 394 +       }
 395 +       return 0;
 396 +}
 397 +
 398  static int do_one_pass(journal_t *journal,
 399                         struct recovery_info *info, enum passtype pass)
 400  {
 401 @@ -318,6 +350,7 @@ static int do_one_pass(journal_t *journa
 402         struct buffer_head *    bh;
 403         unsigned int            sequence;
 404         int                     blocktype;
 405 +       __u32                   crc32_sum = ~0; /* Transactional Checksums */
 406
 407         /* Precompute the maximum metadata descriptors in a descriptor block */
 408         int                     MAX_BLOCKS_PER_DESC;
 409 @@ -409,9 +442,24 @@ static int do_one_pass(journal_t *journa
 410                 switch(blocktype) {
 411                 case JFS_DESCRIPTOR_BLOCK:
 412                         /* If it is a valid descriptor block, replay it
 413 -                        * in pass REPLAY; otherwise, just skip over the
 414 -                        * blocks it describes. */
 415 +                        * in pass REPLAY; if journal_checksums enabled, then
 416 +                        * calculate checksums in PASS_SCAN, otherwise,
 417 +                        * just skip over the blocks it describes. */
 418                         if (pass != PASS_REPLAY) {
 419 +                               if (pass == PASS_SCAN &&
 420 +                                   JFS_HAS_COMPAT_FEATURE(journal,
 421 +                                           JFS_FEATURE_COMPAT_CHECKSUM) &&
 422 +                                   !info->end_transaction) {
 423 +                                       if (calc_chksums(journal, bh,
 424 +                                                       &next_log_block,
 425 +                                                       &crc32_sum)) {
 426 +                                               put_bh(bh);
 427 +                                               break;
 428 +                                       }
 429 +                                       put_bh(bh);
 430 +                                       continue;
 431 +                               }
 432 +
 433                                 next_log_block +=
 434                                         count_tags(bh, journal->j_blocksize);
 435                                 wrap(journal, next_log_block);
 436 @@ -506,9 +554,97 @@ static int do_one_pass(journal_t *journa
 437                         continue;
 438
 439                 case JFS_COMMIT_BLOCK:
 440 -                       /* Found an expected commit block: not much to
 441 -                        * do other than move on to the next sequence
 442 +                       /*     How to differentiate between interrupted commit
 443 +                        *               and journal corruption ?
 444 +                        *
 445 +                        * {nth transaction}
 446 +                        *        Checksum Verification Failed
 447 +                        *                       |
 448 +                        *               ____________________
 449 +                        *              |                    |
 450 +                        *      async_commit             sync_commit
 451 +                        *              |                    |
 452 +                        *              | GO TO NEXT    "Journal Corruption"
 453 +                        *              | TRANSACTION
 454 +                        *              |
 455 +                        * {(n+1)th transanction}
 456 +                        *              |
 457 +                        *       _______|______________
 458 +                        *      |                     |
 459 +                        * Commit block found   Commit block not found
 460 +                        *      |                     |
 461 +                        * "Journal Corruption"       |
 462 +                        *               _____________|__________
 463 +                        *              |                       |
 464 +                        *      nth trans corrupt       OR   nth trans
 465 +                        *      and (n+1)th interrupted     interrupted
 466 +                        *      before commit block
 467 +                        *      could reach the disk.
 468 +                        *      (Cannot find the difference in above
 469 +                        *       mentioned conditions. Hence assume
 470 +                        *       "Interrupted Commit".)
 471 +                        */
 472 +
 473 +                       /* Found an expected commit block: if checksums
 474 +                        * are present verify them in PASS_SCAN; else not
 475 +                        * much to do other than move on to the next sequence
 476                          * number. */
 477 +                       if (pass == PASS_SCAN &&
 478 +                           JFS_HAS_COMPAT_FEATURE(journal,
 479 +                                   JFS_FEATURE_COMPAT_CHECKSUM)) {
 480 +                               int chksum_err, chksum_seen;
 481 +                               struct commit_header *cbh =
 482 +                                       (struct commit_header *)bh->b_data;
 483 +                               unsigned found_chksum =
 484 +                                               be32_to_cpu(cbh->h_chksum[0]);
 485 +
 486 +                               chksum_err = chksum_seen = 0;
 487 +
 488 +                               if (info->end_transaction) {
 489 +                                       printk(KERN_ERR "JBD: Transaction %u "
 490 +                                               "found to be corrupt.\n",
 491 +                                               next_commit_ID - 1);
 492 +                                       brelse(bh);
 493 +                                       break;
 494 +                               }
 495 +
 496 +                               if (crc32_sum == found_chksum &&
 497 +                                   cbh->h_chksum_type == JFS_CRC32_CHKSUM &&
 498 +                                   cbh->h_chksum_size ==
 499 +                                               JFS_CRC32_CHKSUM_SIZE) {
 500 +                                      chksum_seen = 1;
 501 +                               } else if (!(cbh->h_chksum_type == 0 &&
 502 +                                            cbh->h_chksum_size == 0 &&
 503 +                                            found_chksum == 0 &&
 504 +                                            !chksum_seen)) {
 505 +                               /*
 506 +                                * If fs is mounted using an old kernel and then
 507 +                                * kernel with journal_chksum is used then we
 508 +                                * get a situation where the journal flag has
 509 +                                * checksum flag set but checksums are not
 510 +                                * present i.e chksum = 0, in the individual
 511 +                                * commit blocks.
 512 +                                * Hence to avoid checksum failures, in this
 513 +                                * situation, this extra check is added.
 514 +                                */
 515 +                                               chksum_err = 1;
 516 +                               }
 517 +
 518 +                               if (chksum_err) {
 519 +                                       info->end_transaction = next_commit_ID;
 520 +
 521 +                                       if (!JFS_HAS_INCOMPAT_FEATURE(journal,
 522 +                                           JFS_FEATURE_INCOMPAT_ASYNC_COMMIT)){
 523 +                                               printk(KERN_ERR
 524 +                                                      "JBD: Transaction %u "
 525 +                                                      "found to be corrupt.\n",
 526 +                                                      next_commit_ID);
 527 +                                               brelse(bh);
 528 +                                               break;
 529 +                                       }
 530 +                               }
 531 +                               crc32_sum = ~0;
 532 +                       }
 533                         brelse(bh);
 534                         next_commit_ID++;
 535                         continue;
 536 @@ -543,9 +679,10 @@ static int do_one_pass(journal_t *journa
 537          * transaction marks the end of the valid log.
 538          */
 539
 540 -       if (pass == PASS_SCAN)
 541 -               info->end_transaction = next_commit_ID;
 542 -       else {
 543 +       if (pass == PASS_SCAN) {
 544 +               if (!info->end_transaction)
 545 +                       info->end_transaction = next_commit_ID;
 546 +       } else {
 547                 /* It's really bad news if different passes end up at
 548                  * different places (but possible due to IO errors). */
 549                 if (info->end_transaction != next_commit_ID) {
 550 Index: linux-2.6.16.53-0.16/fs/jbd/journal.c
 551 ===================================================================
 552 --- linux-2.6.16.53-0.16.orig/fs/jbd/journal.c
 553 +++ linux-2.6.16.53-0.16/fs/jbd/journal.c
 554 @@ -64,6 +64,7 @@ EXPORT_SYMBOL(journal_update_format);
 555  EXPORT_SYMBOL(journal_check_used_features);
 556  EXPORT_SYMBOL(journal_check_available_features);
 557  EXPORT_SYMBOL(journal_set_features);
 558 +EXPORT_SYMBOL(journal_clear_features);
 559  EXPORT_SYMBOL(journal_create);
 560  EXPORT_SYMBOL(journal_load);
 561  EXPORT_SYMBOL(journal_destroy);
 562 @@ -1565,6 +1566,33 @@ int journal_set_features (journal_t *jou
 563         return 1;
 564  }
 565
 566 +/**
 567 + * int journal_clear_features () - Clear a given journal feature in the superblock
 568 + * @journal: Journal to act on.
 569 + * @compat: bitmask of compatible features
 570 + * @ro: bitmask of features that force read-only mount
 571 + * @incompat: bitmask of incompatible features
 572 + *
 573 + * Clear a given journal feature as present on the
 574 + * superblock.  Returns true if the requested features could be reset.
 575 + *
 576 + */
 577 +int journal_clear_features (journal_t *journal, unsigned long compat,
 578 +                         unsigned long ro, unsigned long incompat)
 579 +{
 580 +       journal_superblock_t *sb;
 581 +
 582 +       jbd_debug(1, "Clear features 0x%lx/0x%lx/0x%lx\n",
 583 +                 compat, ro, incompat);
 584 +
 585 +       sb = journal->j_superblock;
 586 +
 587 +       sb->s_feature_compat    &= ~cpu_to_be32(compat);
 588 +       sb->s_feature_ro_compat &= ~cpu_to_be32(ro);
 589 +       sb->s_feature_incompat  &= ~cpu_to_be32(incompat);
 590 +
 591 +       return 1;
 592 +}
 593
 594  /**
 595   * int journal_update_format () - Update on-disk journal structure.
 596 Index: linux-2.6.16.53-0.16/fs/Kconfig
 597 ===================================================================
 598 --- linux-2.6.16.53-0.16.orig/fs/Kconfig
 599 +++ linux-2.6.16.53-0.16/fs/Kconfig
 600 @@ -140,6 +140,7 @@ config EXT3_FS_SECURITY
 601
 602  config JBD
 603         tristate
 604 +       select CRC32
 605         help
 606           This is a generic journaling layer for block devices.  It is
 607           currently used by the ext3 and OCFS2 file systems, but it could
 608 Index: linux-2.6.16.53-0.16/Documentation/filesystems/ext3.txt
 609 ===================================================================
 610 --- linux-2.6.16.53-0.16.orig/Documentation/filesystems/ext3.txt
 611 +++ linux-2.6.16.53-0.16/Documentation/filesystems/ext3.txt
 612 @@ -14,6 +14,16 @@ Options
 613  When mounting an ext3 filesystem, the following option are accepted:
 614  (*) == default
 615
 616 +journal_checksum       Enable checksumming of the journal transactions.
 617 +                       This will allow the recovery code in e2fsck and the
 618 +                       kernel to detect corruption in the kernel.  It is a
 619 +                       compatible change and will be ignored by older kernels.
 620 +
 621 +journal_async_commit   Commit block can be written to disk without waiting
 622 +                       for descriptor blocks. If enabled older kernels cannot
 623 +                       mount the device. This will enable 'journal_checksum'
 624 +                       internally.
 625 +
 626  journal=update         Update the ext3 file system's journal to the current
 627                         format.
 628