fs/reiserfs/file.c

   1 /*
   2  * Copyright 2000 by Hans Reiser, licensing governed by reiserfs/README
   3  */
   4
   5 #include <linux/time.h>
   6 #include <linux/reiserfs_fs.h>
   7 #include <linux/reiserfs_acl.h>
   8 #include <linux/reiserfs_xattr.h>
   9 #include <linux/smp_lock.h>
  10 #include <asm/uaccess.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/swap.h>
  13 #include <linux/writeback.h>
  14 #include <linux/blkdev.h>
  15 #include <linux/buffer_head.h>
  16 #include <linux/quotaops.h>
  17
  18 /*
  19 ** We pack the tails of files on file close, not at the time they are written.
  20 ** This implies an unnecessary copy of the tail and an unnecessary indirect item
  21 ** insertion/balancing, for files that are written in one write.
  22 ** It avoids unnecessary tail packings (balances) for files that are written in
  23 ** multiple writes and are small enough to have tails.
  24 **
  25 ** file_release is called by the VFS layer when the file is closed.  If
  26 ** this is the last open file descriptor, and the file
  27 ** small enough to have a tail, and the tail is currently in an
  28 ** unformatted node, the tail is converted back into a direct item.
  29 **
  30 ** We use reiserfs_truncate_file to pack the tail, since it already has
  31 ** all the conditions coded.
  32 */
  33 static int reiserfs_file_release(struct inode *inode, struct file *filp)
  34 {
  35
  36         struct reiserfs_transaction_handle th;
  37         int err;
  38         int jbegin_failure = 0;
  39
  40         if (!S_ISREG(inode->i_mode))
  41                 BUG();
  42
  43         /* fast out for when nothing needs to be done */
  44         if ((atomic_read(&inode->i_count) > 1 ||
  45              !(REISERFS_I(inode)->i_flags & i_pack_on_close_mask) ||
  46              !tail_has_to_be_packed(inode)) &&
  47             REISERFS_I(inode)->i_prealloc_count <= 0) {
  48                 return 0;
  49         }
  50
  51         reiserfs_write_lock(inode->i_sb);
  52         down(&inode->i_sem);
  53         /* freeing preallocation only involves relogging blocks that
  54          * are already in the current transaction.  preallocation gets
  55          * freed at the end of each transaction, so it is impossible for
  56          * us to log any additional blocks (including quota blocks)
  57          */
  58         err = journal_begin(&th, inode->i_sb, 1);
  59         if (err) {
  60                 /* uh oh, we can't allow the inode to go away while there
  61                  * is still preallocation blocks pending.  Try to join the
  62                  * aborted transaction
  63                  */
  64                 jbegin_failure = err;
  65                 err = journal_join_abort(&th, inode->i_sb, 1);
  66
  67                 if (err) {
  68                         /* hmpf, our choices here aren't good.  We can pin the inode
  69                          * which will disallow unmount from every happening, we can
  70                          * do nothing, which will corrupt random memory on unmount,
  71                          * or we can forcibly remove the file from the preallocation
  72                          * list, which will leak blocks on disk.  Lets pin the inode
  73                          * and let the admin know what is going on.
  74                          */
  75                         igrab(inode);
  76                         reiserfs_warning(inode->i_sb,
  77                                          "pinning inode %lu because the "
  78                                          "preallocation can't be freed");
  79                         goto out;
  80                 }
  81         }
  82         reiserfs_update_inode_transaction(inode);
  83
  84 #ifdef REISERFS_PREALLOCATE
  85         reiserfs_discard_prealloc(&th, inode);
  86 #endif
  87         err = journal_end(&th, inode->i_sb, 1);
  88
  89         /* copy back the error code from journal_begin */
  90         if (!err)
  91                 err = jbegin_failure;
  92
  93         if (!err && atomic_read(&inode->i_count) <= 1 &&
  94             (REISERFS_I(inode)->i_flags & i_pack_on_close_mask) &&
  95             tail_has_to_be_packed(inode)) {
  96                 /* if regular file is released by last holder and it has been
  97                    appended (we append by unformatted node only) or its direct
  98                    item(s) had to be converted, then it may have to be
  99                    indirect2direct converted */
 100                 err = reiserfs_truncate_file(inode, 0);
 101         }
 102       out:
 103         up(&inode->i_sem);
 104         reiserfs_write_unlock(inode->i_sb);
 105         return err;
 106 }
 107
 108 static void reiserfs_vfs_truncate_file(struct inode *inode)
 109 {
 110         reiserfs_truncate_file(inode, 1);
 111 }
 112
 113 /* Sync a reiserfs file. */
 114
 115 /*
 116  * FIXME: sync_mapping_buffers() never has anything to sync.  Can
 117  * be removed...
 118  */
 119
 120 static int reiserfs_sync_file(struct file *p_s_filp,
 121                               struct dentry *p_s_dentry, int datasync)
 122 {
 123         struct inode *p_s_inode = p_s_dentry->d_inode;
 124         int n_err;
 125         int barrier_done;
 126
 127         if (!S_ISREG(p_s_inode->i_mode))
 128                 BUG();
 129         n_err = sync_mapping_buffers(p_s_inode->i_mapping);
 130         reiserfs_write_lock(p_s_inode->i_sb);
 131         barrier_done = reiserfs_commit_for_inode(p_s_inode);
 132         reiserfs_write_unlock(p_s_inode->i_sb);
 133         if (barrier_done != 1)
 134                 blkdev_issue_flush(p_s_inode->i_sb->s_bdev, NULL);
 135         if (barrier_done < 0)
 136                 return barrier_done;
 137         return (n_err < 0) ? -EIO : 0;
 138 }
 139
 140 /* I really do not want to play with memory shortage right now, so
 141    to simplify the code, we are not going to write more than this much pages at
 142    a time. This still should considerably improve performance compared to 4k
 143    at a time case. This is 32 pages of 4k size. */
 144 #define REISERFS_WRITE_PAGES_AT_A_TIME (128 * 1024) / PAGE_CACHE_SIZE
 145
 146 /* Allocates blocks for a file to fulfil write request.
 147    Maps all unmapped but prepared pages from the list.
 148    Updates metadata with newly allocated blocknumbers as needed */
 149 static int reiserfs_allocate_blocks_for_region(struct reiserfs_transaction_handle *th, struct inode *inode,     /* Inode we work with */
 150                                                loff_t pos,      /* Writing position */
 151                                                int num_pages,   /* number of pages write going
 152                                                                    to touch */
 153                                                int write_bytes, /* amount of bytes to write */
 154                                                struct page **prepared_pages,    /* array of
 155                                                                                    prepared pages
 156                                                                                  */
 157                                                int blocks_to_allocate   /* Amount of blocks we
 158                                                                            need to allocate to
 159                                                                            fit the data into file
 160                                                                          */
 161     )
 162 {
 163         struct cpu_key key;     // cpu key of item that we are going to deal with
 164         struct item_head *ih;   // pointer to item head that we are going to deal with
 165         struct buffer_head *bh; // Buffer head that contains items that we are going to deal with
 166         __le32 *item;           // pointer to item we are going to deal with
 167         INITIALIZE_PATH(path);  // path to item, that we are going to deal with.
 168         b_blocknr_t *allocated_blocks;  // Pointer to a place where allocated blocknumbers would be stored.
 169         reiserfs_blocknr_hint_t hint;   // hint structure for block allocator.
 170         size_t res;             // return value of various functions that we call.
 171         int curr_block;         // current block used to keep track of unmapped blocks.
 172         int i;                  // loop counter
 173         int itempos;            // position in item
 174         unsigned int from = (pos & (PAGE_CACHE_SIZE - 1));      // writing position in
 175         // first page
 176         unsigned int to = ((pos + write_bytes - 1) & (PAGE_CACHE_SIZE - 1)) + 1;        /* last modified byte offset in last page */
 177         __u64 hole_size;        // amount of blocks for a file hole, if it needed to be created.
 178         int modifying_this_item = 0;    // Flag for items traversal code to keep track
 179         // of the fact that we already prepared
 180         // current block for journal
 181         int will_prealloc = 0;
 182         RFALSE(!blocks_to_allocate,
 183                "green-9004: tried to allocate zero blocks?");
 184
 185         /* only preallocate if this is a small write */
 186         if (REISERFS_I(inode)->i_prealloc_count ||
 187             (!(write_bytes & (inode->i_sb->s_blocksize - 1)) &&
 188              blocks_to_allocate <
 189              REISERFS_SB(inode->i_sb)->s_alloc_options.preallocsize))
 190                 will_prealloc =
 191                     REISERFS_SB(inode->i_sb)->s_alloc_options.preallocsize;
 192
 193         allocated_blocks = kmalloc((blocks_to_allocate + will_prealloc) *
 194                                    sizeof(b_blocknr_t), GFP_NOFS);
 195
 196         /* First we compose a key to point at the writing position, we want to do
 197            that outside of any locking region. */
 198         make_cpu_key(&key, inode, pos + 1, TYPE_ANY, 3 /*key length */ );
 199
 200         /* If we came here, it means we absolutely need to open a transaction,
 201            since we need to allocate some blocks */
 202         reiserfs_write_lock(inode->i_sb);       // Journaling stuff and we need that.
 203         res = journal_begin(th, inode->i_sb, JOURNAL_PER_BALANCE_CNT * 3 + 1 + 2 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb));   // Wish I know if this number enough
 204         if (res)
 205                 goto error_exit;
 206         reiserfs_update_inode_transaction(inode);
 207
 208         /* Look for the in-tree position of our write, need path for block allocator */
 209         res = search_for_position_by_key(inode->i_sb, &key, &path);
 210         if (res == IO_ERROR) {
 211                 res = -EIO;
 212                 goto error_exit;
 213         }
 214
 215         /* Allocate blocks */
 216         /* First fill in "hint" structure for block allocator */
 217         hint.th = th;           // transaction handle.
 218         hint.path = &path;      // Path, so that block allocator can determine packing locality or whatever it needs to determine.
 219         hint.inode = inode;     // Inode is needed by block allocator too.
 220         hint.search_start = 0;  // We have no hint on where to search free blocks for block allocator.
 221         hint.key = key.on_disk_key;     // on disk key of file.
 222         hint.block = inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9);    // Number of disk blocks this file occupies already.
 223         hint.formatted_node = 0;        // We are allocating blocks for unformatted node.
 224         hint.preallocate = will_prealloc;
 225
 226         /* Call block allocator to allocate blocks */
 227         res =
 228             reiserfs_allocate_blocknrs(&hint, allocated_blocks,
 229                                        blocks_to_allocate, blocks_to_allocate);
 230         if (res != CARRY_ON) {
 231                 if (res == NO_DISK_SPACE) {
 232                         /* We flush the transaction in case of no space. This way some
 233                            blocks might become free */
 234                         SB_JOURNAL(inode->i_sb)->j_must_wait = 1;
 235                         res = restart_transaction(th, inode, &path);
 236                         if (res)
 237                                 goto error_exit;
 238
 239                         /* We might have scheduled, so search again */
 240                         res =
 241                             search_for_position_by_key(inode->i_sb, &key,
 242                                                        &path);
 243                         if (res == IO_ERROR) {
 244                                 res = -EIO;
 245                                 goto error_exit;
 246                         }
 247
 248                         /* update changed info for hint structure. */
 249                         res =
 250                             reiserfs_allocate_blocknrs(&hint, allocated_blocks,
 251                                                        blocks_to_allocate,
 252                                                        blocks_to_allocate);
 253                         if (res != CARRY_ON) {
 254                                 res = -ENOSPC;
 255                                 pathrelse(&path);
 256                                 goto error_exit;
 257                         }
 258                 } else {
 259                         res = -ENOSPC;
 260                         pathrelse(&path);
 261                         goto error_exit;
 262                 }
 263         }
 264 #ifdef __BIG_ENDIAN
 265         // Too bad, I have not found any way to convert a given region from
 266         // cpu format to little endian format
 267         {
 268                 int i;
 269                 for (i = 0; i < blocks_to_allocate; i++)
 270                         allocated_blocks[i] = cpu_to_le32(allocated_blocks[i]);
 271         }
 272 #endif
 273
 274         /* Blocks allocating well might have scheduled and tree might have changed,
 275            let's search the tree again */
 276         /* find where in the tree our write should go */
 277         res = search_for_position_by_key(inode->i_sb, &key, &path);
 278         if (res == IO_ERROR) {
 279                 res = -EIO;
 280                 goto error_exit_free_blocks;
 281         }
 282
 283         bh = get_last_bh(&path);        // Get a bufferhead for last element in path.
 284         ih = get_ih(&path);     // Get a pointer to last item head in path.
 285         item = get_item(&path); // Get a pointer to last item in path
 286
 287         /* Let's see what we have found */
 288         if (res != POSITION_FOUND) {    /* position not found, this means that we
 289                                            might need to append file with holes
 290                                            first */
 291                 // Since we are writing past the file's end, we need to find out if
 292                 // there is a hole that needs to be inserted before our writing
 293                 // position, and how many blocks it is going to cover (we need to
 294                 //  populate pointers to file blocks representing the hole with zeros)
 295
 296                 {
 297                         int item_offset = 1;
 298                         /*
 299                          * if ih is stat data, its offset is 0 and we don't want to
 300                          * add 1 to pos in the hole_size calculation
 301                          */
 302                         if (is_statdata_le_ih(ih))
 303                                 item_offset = 0;
 304                         hole_size = (pos + item_offset -
 305                                      (le_key_k_offset
 306                                       (get_inode_item_key_version(inode),
 307                                        &(ih->ih_key)) + op_bytes_number(ih,
 308                                                                         inode->
 309                                                                         i_sb->
 310                                                                         s_blocksize)))
 311                             >> inode->i_sb->s_blocksize_bits;
 312                 }
 313
 314                 if (hole_size > 0) {
 315                         int to_paste = min_t(__u64, hole_size, MAX_ITEM_LEN(inode->i_sb->s_blocksize) / UNFM_P_SIZE);   // How much data to insert first time.
 316                         /* area filled with zeroes, to supply as list of zero blocknumbers
 317                            We allocate it outside of loop just in case loop would spin for
 318                            several iterations. */
 319                         char *zeros = kmalloc(to_paste * UNFM_P_SIZE, GFP_ATOMIC);      // We cannot insert more than MAX_ITEM_LEN bytes anyway.
 320                         if (!zeros) {
 321                                 res = -ENOMEM;
 322                                 goto error_exit_free_blocks;
 323                         }
 324                         memset(zeros, 0, to_paste * UNFM_P_SIZE);
 325                         do {
 326                                 to_paste =
 327                                     min_t(__u64, hole_size,
 328                                           MAX_ITEM_LEN(inode->i_sb->
 329                                                        s_blocksize) /
 330                                           UNFM_P_SIZE);
 331                                 if (is_indirect_le_ih(ih)) {
 332                                         /* Ok, there is existing indirect item already. Need to append it */
 333                                         /* Calculate position past inserted item */
 334                                         make_cpu_key(&key, inode,
 335                                                      le_key_k_offset
 336                                                      (get_inode_item_key_version
 337                                                       (inode),
 338                                                       &(ih->ih_key)) +
 339                                                      op_bytes_number(ih,
 340                                                                      inode->
 341                                                                      i_sb->
 342                                                                      s_blocksize),
 343                                                      TYPE_INDIRECT, 3);
 344                                         res =
 345                                             reiserfs_paste_into_item(th, &path,
 346                                                                      &key,
 347                                                                      inode,
 348                                                                      (char *)
 349                                                                      zeros,
 350                                                                      UNFM_P_SIZE
 351                                                                      *
 352                                                                      to_paste);
 353                                         if (res) {
 354                                                 kfree(zeros);
 355                                                 goto error_exit_free_blocks;
 356                                         }
 357                                 } else if (is_statdata_le_ih(ih)) {
 358                                         /* No existing item, create it */
 359                                         /* item head for new item */
 360                                         struct item_head ins_ih;
 361
 362                                         /* create a key for our new item */
 363                                         make_cpu_key(&key, inode, 1,
 364                                                      TYPE_INDIRECT, 3);
 365
 366                                         /* Create new item head for our new item */
 367                                         make_le_item_head(&ins_ih, &key,
 368                                                           key.version, 1,
 369                                                           TYPE_INDIRECT,
 370                                                           to_paste *
 371                                                           UNFM_P_SIZE,
 372                                                           0 /* free space */ );
 373
 374                                         /* Find where such item should live in the tree */
 375                                         res =
 376                                             search_item(inode->i_sb, &key,
 377                                                         &path);
 378                                         if (res != ITEM_NOT_FOUND) {
 379                                                 /* item should not exist, otherwise we have error */
 380                                                 if (res != -ENOSPC) {
 381                                                         reiserfs_warning(inode->
 382                                                                          i_sb,
 383                                                                          "green-9008: search_by_key (%K) returned %d",
 384                                                                          &key,
 385                                                                          res);
 386                                                 }
 387                                                 res = -EIO;
 388                                                 kfree(zeros);
 389                                                 goto error_exit_free_blocks;
 390                                         }
 391                                         res =
 392                                             reiserfs_insert_item(th, &path,
 393                                                                  &key, &ins_ih,
 394                                                                  inode,
 395                                                                  (char *)zeros);
 396                                 } else {
 397                                         reiserfs_panic(inode->i_sb,
 398                                                        "green-9011: Unexpected key type %K\n",
 399                                                        &key);
 400                                 }
 401                                 if (res) {
 402                                         kfree(zeros);
 403                                         goto error_exit_free_blocks;
 404                                 }
 405                                 /* Now we want to check if transaction is too full, and if it is
 406                                    we restart it. This will also free the path. */
 407                                 if (journal_transaction_should_end
 408                                     (th, th->t_blocks_allocated)) {
 409                                         res =
 410                                             restart_transaction(th, inode,
 411                                                                 &path);
 412                                         if (res) {
 413                                                 pathrelse(&path);
 414                                                 kfree(zeros);
 415                                                 goto error_exit;
 416                                         }
 417                                 }
 418
 419                                 /* Well, need to recalculate path and stuff */
 420                                 set_cpu_key_k_offset(&key,
 421                                                      cpu_key_k_offset(&key) +
 422                                                      (to_paste << inode->
 423                                                       i_blkbits));
 424                                 res =
 425                                     search_for_position_by_key(inode->i_sb,
 426                                                                &key, &path);
 427                                 if (res == IO_ERROR) {
 428                                         res = -EIO;
 429                                         kfree(zeros);
 430                                         goto error_exit_free_blocks;
 431                                 }
 432                                 bh = get_last_bh(&path);
 433                                 ih = get_ih(&path);
 434                                 item = get_item(&path);
 435                                 hole_size -= to_paste;
 436                         } while (hole_size);
 437                         kfree(zeros);
 438                 }
 439         }
 440         // Go through existing indirect items first
 441         // replace all zeroes with blocknumbers from list
 442         // Note that if no corresponding item was found, by previous search,
 443         // it means there are no existing in-tree representation for file area
 444         // we are going to overwrite, so there is nothing to scan through for holes.
 445         for (curr_block = 0, itempos = path.pos_in_item;
 446              curr_block < blocks_to_allocate && res == POSITION_FOUND;) {
 447               retry:
 448
 449                 if (itempos >= ih_item_len(ih) / UNFM_P_SIZE) {
 450                         /* We run out of data in this indirect item, let's look for another
 451                            one. */
 452                         /* First if we are already modifying current item, log it */
 453                         if (modifying_this_item) {
 454                                 journal_mark_dirty(th, inode->i_sb, bh);
 455                                 modifying_this_item = 0;
 456                         }
 457                         /* Then set the key to look for a new indirect item (offset of old
 458                            item is added to old item length */
 459                         set_cpu_key_k_offset(&key,
 460                                              le_key_k_offset
 461                                              (get_inode_item_key_version(inode),
 462                                               &(ih->ih_key)) +
 463                                              op_bytes_number(ih,
 464                                                              inode->i_sb->
 465                                                              s_blocksize));
 466                         /* Search ofor position of new key in the tree. */
 467                         res =
 468                             search_for_position_by_key(inode->i_sb, &key,
 469                                                        &path);
 470                         if (res == IO_ERROR) {
 471                                 res = -EIO;
 472                                 goto error_exit_free_blocks;
 473                         }
 474                         bh = get_last_bh(&path);
 475                         ih = get_ih(&path);
 476                         item = get_item(&path);
 477                         itempos = path.pos_in_item;
 478                         continue;       // loop to check all kinds of conditions and so on.
 479                 }
 480                 /* Ok, we have correct position in item now, so let's see if it is
 481                    representing file hole (blocknumber is zero) and fill it if needed */
 482                 if (!item[itempos]) {
 483                         /* Ok, a hole. Now we need to check if we already prepared this
 484                            block to be journaled */
 485                         while (!modifying_this_item) {  // loop until succeed
 486                                 /* Well, this item is not journaled yet, so we must prepare
 487                                    it for journal first, before we can change it */
 488                                 struct item_head tmp_ih;        // We copy item head of found item,
 489                                 // here to detect if fs changed under
 490                                 // us while we were preparing for
 491                                 // journal.
 492                                 int fs_gen;     // We store fs generation here to find if someone
 493                                 // changes fs under our feet
 494
 495                                 copy_item_head(&tmp_ih, ih);    // Remember itemhead
 496                                 fs_gen = get_generation(inode->i_sb);   // remember fs generation
 497                                 reiserfs_prepare_for_journal(inode->i_sb, bh, 1);       // Prepare a buffer within which indirect item is stored for changing.
 498                                 if (fs_changed(fs_gen, inode->i_sb)
 499                                     && item_moved(&tmp_ih, &path)) {
 500                                         // Sigh, fs was changed under us, we need to look for new
 501                                         // location of item we are working with
 502
 503                                         /* unmark prepaerd area as journaled and search for it's
 504                                            new position */
 505                                         reiserfs_restore_prepared_buffer(inode->
 506                                                                          i_sb,
 507                                                                          bh);
 508                                         res =
 509                                             search_for_position_by_key(inode->
 510                                                                        i_sb,
 511                                                                        &key,
 512                                                                        &path);
 513                                         if (res == IO_ERROR) {
 514                                                 res = -EIO;
 515                                                 goto error_exit_free_blocks;
 516                                         }
 517                                         bh = get_last_bh(&path);
 518                                         ih = get_ih(&path);
 519                                         item = get_item(&path);
 520                                         itempos = path.pos_in_item;
 521                                         goto retry;
 522                                 }
 523                                 modifying_this_item = 1;
 524                         }
 525                         item[itempos] = allocated_blocks[curr_block];   // Assign new block
 526                         curr_block++;
 527                 }
 528                 itempos++;
 529         }
 530
 531         if (modifying_this_item) {      // We need to log last-accessed block, if it
 532                 // was modified, but not logged yet.
 533                 journal_mark_dirty(th, inode->i_sb, bh);
 534         }
 535
 536         if (curr_block < blocks_to_allocate) {
 537                 // Oh, well need to append to indirect item, or to create indirect item
 538                 // if there weren't any
 539                 if (is_indirect_le_ih(ih)) {
 540                         // Existing indirect item - append. First calculate key for append
 541                         // position. We do not need to recalculate path as it should
 542                         // already point to correct place.
 543                         make_cpu_key(&key, inode,
 544                                      le_key_k_offset(get_inode_item_key_version
 545                                                      (inode),
 546                                                      &(ih->ih_key)) +
 547                                      op_bytes_number(ih,
 548                                                      inode->i_sb->s_blocksize),
 549                                      TYPE_INDIRECT, 3);
 550                         res =
 551                             reiserfs_paste_into_item(th, &path, &key, inode,
 552                                                      (char *)(allocated_blocks +
 553                                                               curr_block),
 554                                                      UNFM_P_SIZE *
 555                                                      (blocks_to_allocate -
 556                                                       curr_block));
 557                         if (res) {
 558                                 goto error_exit_free_blocks;
 559                         }
 560                 } else if (is_statdata_le_ih(ih)) {
 561                         // Last found item was statdata. That means we need to create indirect item.
 562                         struct item_head ins_ih;        /* itemhead for new item */
 563
 564                         /* create a key for our new item */
 565                         make_cpu_key(&key, inode, 1, TYPE_INDIRECT, 3); // Position one,
 566                         // because that's
 567                         // where first
 568                         // indirect item
 569                         // begins
 570                         /* Create new item head for our new item */
 571                         make_le_item_head(&ins_ih, &key, key.version, 1,
 572                                           TYPE_INDIRECT,
 573                                           (blocks_to_allocate -
 574                                            curr_block) * UNFM_P_SIZE,
 575                                           0 /* free space */ );
 576                         /* Find where such item should live in the tree */
 577                         res = search_item(inode->i_sb, &key, &path);
 578                         if (res != ITEM_NOT_FOUND) {
 579                                 /* Well, if we have found such item already, or some error
 580                                    occured, we need to warn user and return error */
 581                                 if (res != -ENOSPC) {
 582                                         reiserfs_warning(inode->i_sb,
 583                                                          "green-9009: search_by_key (%K) "
 584                                                          "returned %d", &key,
 585                                                          res);
 586                                 }
 587                                 res = -EIO;
 588                                 goto error_exit_free_blocks;
 589                         }
 590                         /* Insert item into the tree with the data as its body */
 591                         res =
 592                             reiserfs_insert_item(th, &path, &key, &ins_ih,
 593                                                  inode,
 594                                                  (char *)(allocated_blocks +
 595                                                           curr_block));
 596                 } else {
 597                         reiserfs_panic(inode->i_sb,
 598                                        "green-9010: unexpected item type for key %K\n",
 599                                        &key);
 600                 }
 601         }
 602         // the caller is responsible for closing the transaction
 603         // unless we return an error, they are also responsible for logging
 604         // the inode.
 605         //
 606         pathrelse(&path);
 607         /*
 608          * cleanup prellocation from previous writes
 609          * if this is a partial block write
 610          */
 611         if (write_bytes & (inode->i_sb->s_blocksize - 1))
 612                 reiserfs_discard_prealloc(th, inode);
 613         reiserfs_write_unlock(inode->i_sb);
 614
 615         // go through all the pages/buffers and map the buffers to newly allocated
 616         // blocks (so that system knows where to write these pages later).
 617         curr_block = 0;
 618         for (i = 0; i < num_pages; i++) {
 619                 struct page *page = prepared_pages[i];  //current page
 620                 struct buffer_head *head = page_buffers(page);  // first buffer for a page
 621                 int block_start, block_end;     // in-page offsets for buffers.
 622
 623                 if (!page_buffers(page))
 624                         reiserfs_panic(inode->i_sb,
 625                                        "green-9005: No buffers for prepared page???");
 626
 627                 /* For each buffer in page */
 628                 for (bh = head, block_start = 0; bh != head || !block_start;
 629                      block_start = block_end, bh = bh->b_this_page) {
 630                         if (!bh)
 631                                 reiserfs_panic(inode->i_sb,
 632                                                "green-9006: Allocated but absent buffer for a page?");
 633                         block_end = block_start + inode->i_sb->s_blocksize;
 634                         if (i == 0 && block_end <= from)
 635                                 /* if this buffer is before requested data to map, skip it */
 636                                 continue;
 637                         if (i == num_pages - 1 && block_start >= to)
 638                                 /* If this buffer is after requested data to map, abort
 639                                    processing of current page */
 640                                 break;
 641
 642                         if (!buffer_mapped(bh)) {       // Ok, unmapped buffer, need to map it
 643                                 map_bh(bh, inode->i_sb,
 644                                        le32_to_cpu(allocated_blocks
 645                                                    [curr_block]));
 646                                 curr_block++;
 647                                 set_buffer_new(bh);
 648                         }
 649                 }
 650         }
 651
 652         RFALSE(curr_block > blocks_to_allocate,
 653                "green-9007: Used too many blocks? weird");
 654
 655         kfree(allocated_blocks);
 656         return 0;
 657
 658 // Need to deal with transaction here.
 659       error_exit_free_blocks:
 660         pathrelse(&path);
 661         // free blocks
 662         for (i = 0; i < blocks_to_allocate; i++)
 663                 reiserfs_free_block(th, inode, le32_to_cpu(allocated_blocks[i]),
 664                                     1);
 665
 666       error_exit:
 667         if (th->t_trans_id) {
 668                 int err;
 669                 // update any changes we made to blk count
 670                 reiserfs_update_sd(th, inode);
 671                 err =
 672                     journal_end(th, inode->i_sb,
 673                                 JOURNAL_PER_BALANCE_CNT * 3 + 1 +
 674                                 2 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb));
 675                 if (err)
 676                         res = err;
 677         }
 678         reiserfs_write_unlock(inode->i_sb);
 679         kfree(allocated_blocks);
 680
 681         return res;
 682 }
 683
 684 /* Unlock pages prepared by reiserfs_prepare_file_region_for_write */
 685 static void reiserfs_unprepare_pages(struct page **prepared_pages,      /* list of locked pages */
 686                                      size_t num_pages /* amount of pages */ )
 687 {
 688         int i;                  // loop counter
 689
 690         for (i = 0; i < num_pages; i++) {
 691                 struct page *page = prepared_pages[i];
 692
 693                 try_to_free_buffers(page);
 694                 unlock_page(page);
 695                 page_cache_release(page);
 696         }
 697 }
 698
 699 /* This function will copy data from userspace to specified pages within
 700    supplied byte range */
 701 static int reiserfs_copy_from_user_to_file_region(loff_t pos,   /* In-file position */
 702                                                   int num_pages,        /* Number of pages affected */
 703                                                   int write_bytes,      /* Amount of bytes to write */
 704                                                   struct page **prepared_pages, /* pointer to
 705                                                                                    array to
 706                                                                                    prepared pages
 707                                                                                  */
 708                                                   const char __user * buf       /* Pointer to user-supplied
 709                                                                                    data */
 710     )
 711 {
 712         long page_fault = 0;    // status of copy_from_user.
 713         int i;                  // loop counter.
 714         int offset;             // offset in page
 715
 716         for (i = 0, offset = (pos & (PAGE_CACHE_SIZE - 1)); i < num_pages;
 717              i++, offset = 0) {
 718                 size_t count = min_t(size_t, PAGE_CACHE_SIZE - offset, write_bytes);    // How much of bytes to write to this page
 719                 struct page *page = prepared_pages[i];  // Current page we process.
 720
 721                 fault_in_pages_readable(buf, count);
 722
 723                 /* Copy data from userspace to the current page */
 724                 kmap(page);
 725                 page_fault = __copy_from_user(page_address(page) + offset, buf, count); // Copy the data.
 726                 /* Flush processor's dcache for this page */
 727                 flush_dcache_page(page);
 728                 kunmap(page);
 729                 buf += count;
 730                 write_bytes -= count;
 731
 732                 if (page_fault)
 733                         break;  // Was there a fault? abort.
 734         }
 735
 736         return page_fault ? -EFAULT : 0;
 737 }
 738
 739 /* taken fs/buffer.c:__block_commit_write */
 740 int reiserfs_commit_page(struct inode *inode, struct page *page,
 741                          unsigned from, unsigned to)
 742 {
 743         unsigned block_start, block_end;
 744         int partial = 0;
 745         unsigned blocksize;
 746         struct buffer_head *bh, *head;
 747         unsigned long i_size_index = inode->i_size >> PAGE_CACHE_SHIFT;
 748         int new;
 749         int logit = reiserfs_file_data_log(inode);
 750         struct super_block *s = inode->i_sb;
 751         int bh_per_page = PAGE_CACHE_SIZE / s->s_blocksize;
 752         struct reiserfs_transaction_handle th;
 753         int ret = 0;
 754
 755         th.t_trans_id = 0;
 756         blocksize = 1 << inode->i_blkbits;
 757
 758         if (logit) {
 759                 reiserfs_write_lock(s);
 760                 ret = journal_begin(&th, s, bh_per_page + 1);
 761                 if (ret)
 762                         goto drop_write_lock;
 763                 reiserfs_update_inode_transaction(inode);
 764         }
 765         for (bh = head = page_buffers(page), block_start = 0;
 766              bh != head || !block_start;
 767              block_start = block_end, bh = bh->b_this_page) {
 768
 769                 new = buffer_new(bh);
 770                 clear_buffer_new(bh);
 771                 block_end = block_start + blocksize;
 772                 if (block_end <= from || block_start >= to) {
 773                         if (!buffer_uptodate(bh))
 774                                 partial = 1;
 775                 } else {
 776                         set_buffer_uptodate(bh);
 777                         if (logit) {
 778                                 reiserfs_prepare_for_journal(s, bh, 1);
 779                                 journal_mark_dirty(&th, s, bh);
 780                         } else if (!buffer_dirty(bh)) {
 781                                 mark_buffer_dirty(bh);
 782                                 /* do data=ordered on any page past the end
 783                                  * of file and any buffer marked BH_New.
 784                                  */
 785                                 if (reiserfs_data_ordered(inode->i_sb) &&
 786                                     (new || page->index >= i_size_index)) {
 787                                         reiserfs_add_ordered_list(inode, bh);
 788                                 }
 789                         }
 790                 }
 791         }
 792         if (logit) {
 793                 ret = journal_end(&th, s, bh_per_page + 1);
 794               drop_write_lock:
 795                 reiserfs_write_unlock(s);
 796         }
 797         /*
 798          * If this is a partial write which happened to make all buffers
 799          * uptodate then we can optimize away a bogus readpage() for
 800          * the next read(). Here we 'discover' whether the page went
 801          * uptodate as a result of this (potentially partial) write.
 802          */
 803         if (!partial)
 804                 SetPageUptodate(page);
 805         return ret;
 806 }
 807
 808 /* Submit pages for write. This was separated from actual file copying
 809    because we might want to allocate block numbers in-between.
 810    This function assumes that caller will adjust file size to correct value. */
 811 static int reiserfs_submit_file_region_for_write(struct reiserfs_transaction_handle *th, struct inode *inode, loff_t pos,       /* Writing position offset */
 812                                                  size_t num_pages,      /* Number of pages to write */
 813                                                  size_t write_bytes,    /* number of bytes to write */
 814                                                  struct page **prepared_pages   /* list of pages */
 815     )
 816 {
 817         int status;             // return status of block_commit_write.
 818         int retval = 0;         // Return value we are going to return.
 819         int i;                  // loop counter
 820         int offset;             // Writing offset in page.
 821         int orig_write_bytes = write_bytes;
 822         int sd_update = 0;
 823
 824         for (i = 0, offset = (pos & (PAGE_CACHE_SIZE - 1)); i < num_pages;
 825              i++, offset = 0) {
 826                 int count = min_t(int, PAGE_CACHE_SIZE - offset, write_bytes);  // How much of bytes to write to this page
 827                 struct page *page = prepared_pages[i];  // Current page we process.
 828
 829                 status =
 830                     reiserfs_commit_page(inode, page, offset, offset + count);
 831                 if (status)
 832                         retval = status;        // To not overcomplicate matters We are going to
 833                 // submit all the pages even if there was error.
 834                 // we only remember error status to report it on
 835                 // exit.
 836                 write_bytes -= count;
 837         }
 838         /* now that we've gotten all the ordered buffers marked dirty,
 839          * we can safely update i_size and close any running transaction
 840          */
 841         if (pos + orig_write_bytes > inode->i_size) {
 842                 inode->i_size = pos + orig_write_bytes; // Set new size
 843                 /* If the file have grown so much that tail packing is no
 844                  * longer possible, reset "need to pack" flag */
 845                 if ((have_large_tails(inode->i_sb) &&
 846                      inode->i_size > i_block_size(inode) * 4) ||
 847                     (have_small_tails(inode->i_sb) &&
 848                      inode->i_size > i_block_size(inode)))
 849                         REISERFS_I(inode)->i_flags &= ~i_pack_on_close_mask;
 850                 else if ((have_large_tails(inode->i_sb) &&
 851                           inode->i_size < i_block_size(inode) * 4) ||
 852                          (have_small_tails(inode->i_sb) &&
 853                           inode->i_size < i_block_size(inode)))
 854                         REISERFS_I(inode)->i_flags |= i_pack_on_close_mask;
 855
 856                 if (th->t_trans_id) {
 857                         reiserfs_write_lock(inode->i_sb);
 858                         reiserfs_update_sd(th, inode);  // And update on-disk metadata
 859                         reiserfs_write_unlock(inode->i_sb);
 860                 } else
 861                         inode->i_sb->s_op->dirty_inode(inode);
 862
 863                 sd_update = 1;
 864         }
 865         if (th->t_trans_id) {
 866                 reiserfs_write_lock(inode->i_sb);
 867                 if (!sd_update)
 868                         reiserfs_update_sd(th, inode);
 869                 status = journal_end(th, th->t_super, th->t_blocks_allocated);
 870                 if (status)
 871                         retval = status;
 872                 reiserfs_write_unlock(inode->i_sb);
 873         }
 874         th->t_trans_id = 0;
 875
 876         /*
 877          * we have to unlock the pages after updating i_size, otherwise
 878          * we race with writepage
 879          */
 880         for (i = 0; i < num_pages; i++) {
 881                 struct page *page = prepared_pages[i];
 882                 unlock_page(page);
 883                 mark_page_accessed(page);
 884                 page_cache_release(page);
 885         }
 886         return retval;
 887 }
 888
 889 /* Look if passed writing region is going to touch file's tail
 890    (if it is present). And if it is, convert the tail to unformatted node */
 891 static int reiserfs_check_for_tail_and_convert(struct inode *inode,     /* inode to deal with */
 892                                                loff_t pos,      /* Writing position */
 893                                                int write_bytes  /* amount of bytes to write */
 894     )
 895 {
 896         INITIALIZE_PATH(path);  // needed for search_for_position
 897         struct cpu_key key;     // Key that would represent last touched writing byte.
 898         struct item_head *ih;   // item header of found block;
 899         int res;                // Return value of various functions we call.
 900         int cont_expand_offset; // We will put offset for generic_cont_expand here
 901         // This can be int just because tails are created
 902         // only for small files.
 903
 904 /* this embodies a dependency on a particular tail policy */
 905         if (inode->i_size >= inode->i_sb->s_blocksize * 4) {
 906                 /* such a big files do not have tails, so we won't bother ourselves
 907                    to look for tails, simply return */
 908                 return 0;
 909         }
 910
 911         reiserfs_write_lock(inode->i_sb);
 912         /* find the item containing the last byte to be written, or if
 913          * writing past the end of the file then the last item of the
 914          * file (and then we check its type). */
 915         make_cpu_key(&key, inode, pos + write_bytes + 1, TYPE_ANY,
 916                      3 /*key length */ );
 917         res = search_for_position_by_key(inode->i_sb, &key, &path);
 918         if (res == IO_ERROR) {
 919                 reiserfs_write_unlock(inode->i_sb);
 920                 return -EIO;
 921         }
 922         ih = get_ih(&path);
 923         res = 0;
 924         if (is_direct_le_ih(ih)) {
 925                 /* Ok, closest item is file tail (tails are stored in "direct"
 926                  * items), so we need to unpack it. */
 927                 /* To not overcomplicate matters, we just call generic_cont_expand
 928                    which will in turn call other stuff and finally will boil down to
 929                    reiserfs_get_block() that would do necessary conversion. */
 930                 cont_expand_offset =
 931                     le_key_k_offset(get_inode_item_key_version(inode),
 932                                     &(ih->ih_key));
 933                 pathrelse(&path);
 934                 res = generic_cont_expand(inode, cont_expand_offset);
 935         } else
 936                 pathrelse(&path);
 937
 938         reiserfs_write_unlock(inode->i_sb);
 939         return res;
 940 }
 941
 942 /* This function locks pages starting from @pos for @inode.
 943    @num_pages pages are locked and stored in
 944    @prepared_pages array. Also buffers are allocated for these pages.
 945    First and last page of the region is read if it is overwritten only
 946    partially. If last page did not exist before write (file hole or file
 947    append), it is zeroed, then.
 948    Returns number of unallocated blocks that should be allocated to cover
 949    new file data.*/
 950 static int reiserfs_prepare_file_region_for_write(struct inode *inode
 951                                                   /* Inode of the file */ ,
 952                                                   loff_t pos,   /* position in the file */
 953                                                   size_t num_pages,     /* number of pages to
 954                                                                            prepare */
 955                                                   size_t write_bytes,   /* Amount of bytes to be
 956                                                                            overwritten from
 957                                                                            @pos */
 958                                                   struct page **prepared_pages  /* pointer to array
 959                                                                                    where to store
 960                                                                                    prepared pages */
 961     )
 962 {
 963         int res = 0;            // Return values of different functions we call.
 964         unsigned long index = pos >> PAGE_CACHE_SHIFT;  // Offset in file in pages.
 965         int from = (pos & (PAGE_CACHE_SIZE - 1));       // Writing offset in first page
 966         int to = ((pos + write_bytes - 1) & (PAGE_CACHE_SIZE - 1)) + 1;
 967         /* offset of last modified byte in last
 968            page */
 969         struct address_space *mapping = inode->i_mapping;       // Pages are mapped here.
 970         int i;                  // Simple counter
 971         int blocks = 0;         /* Return value (blocks that should be allocated) */
 972         struct buffer_head *bh, *head;  // Current bufferhead and first bufferhead
 973         // of a page.
 974         unsigned block_start, block_end;        // Starting and ending offsets of current
 975         // buffer in the page.
 976         struct buffer_head *wait[2], **wait_bh = wait;  // Buffers for page, if
 977         // Page appeared to be not up
 978         // to date. Note how we have
 979         // at most 2 buffers, this is
 980         // because we at most may
 981         // partially overwrite two
 982         // buffers for one page. One at                                                 // the beginning of write area
 983         // and one at the end.
 984         // Everything inthe middle gets                                                 // overwritten totally.
 985
 986         struct cpu_key key;     // cpu key of item that we are going to deal with
 987         struct item_head *ih = NULL;    // pointer to item head that we are going to deal with
 988         struct buffer_head *itembuf = NULL;     // Buffer head that contains items that we are going to deal with
 989         INITIALIZE_PATH(path);  // path to item, that we are going to deal with.
 990         __le32 *item = NULL;    // pointer to item we are going to deal with
 991         int item_pos = -1;      /* Position in indirect item */
 992
 993         if (num_pages < 1) {
 994                 reiserfs_warning(inode->i_sb,
 995                                  "green-9001: reiserfs_prepare_file_region_for_write "
 996                                  "called with zero number of pages to process");
 997                 return -EFAULT;
 998         }
 999
1000         /* We have 2 loops for pages. In first loop we grab and lock the pages, so
1001            that nobody would touch these until we release the pages. Then
1002            we'd start to deal with mapping buffers to blocks. */
1003         for (i = 0; i < num_pages; i++) {
1004                 prepared_pages[i] = grab_cache_page(mapping, index + i);        // locks the page
1005                 if (!prepared_pages[i]) {
1006                         res = -ENOMEM;
1007                         goto failed_page_grabbing;
1008                 }
1009                 if (!page_has_buffers(prepared_pages[i]))
1010                         create_empty_buffers(prepared_pages[i],
1011                                              inode->i_sb->s_blocksize, 0);
1012         }
1013
1014         /* Let's count amount of blocks for a case where all the blocks
1015            overwritten are new (we will substract already allocated blocks later) */
1016         if (num_pages > 2)
1017                 /* These are full-overwritten pages so we count all the blocks in
1018                    these pages are counted as needed to be allocated */
1019                 blocks =
1020                     (num_pages - 2) << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1021
1022         /* count blocks needed for first page (possibly partially written) */
1023         blocks += ((PAGE_CACHE_SIZE - from) >> inode->i_blkbits) + !!(from & (inode->i_sb->s_blocksize - 1));   /* roundup */
1024
1025         /* Now we account for last page. If last page == first page (we
1026            overwrite only one page), we substract all the blocks past the
1027            last writing position in a page out of already calculated number
1028            of blocks */
1029         blocks += ((num_pages > 1) << (PAGE_CACHE_SHIFT - inode->i_blkbits)) -
1030             ((PAGE_CACHE_SIZE - to) >> inode->i_blkbits);
1031         /* Note how we do not roundup here since partial blocks still
1032            should be allocated */
1033
1034         /* Now if all the write area lies past the file end, no point in
1035            maping blocks, since there is none, so we just zero out remaining
1036            parts of first and last pages in write area (if needed) */
1037         if ((pos & ~((loff_t) PAGE_CACHE_SIZE - 1)) > inode->i_size) {
1038                 if (from != 0) {        /* First page needs to be partially zeroed */
1039                         char *kaddr = kmap_atomic(prepared_pages[0], KM_USER0);
1040                         memset(kaddr, 0, from);
1041                         kunmap_atomic(kaddr, KM_USER0);
1042                 }
1043                 if (to != PAGE_CACHE_SIZE) {    /* Last page needs to be partially zeroed */
1044                         char *kaddr =
1045                             kmap_atomic(prepared_pages[num_pages - 1],
1046                                         KM_USER0);
1047                         memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
1048                         kunmap_atomic(kaddr, KM_USER0);
1049                 }
1050
1051                 /* Since all blocks are new - use already calculated value */
1052                 return blocks;
1053         }
1054
1055         /* Well, since we write somewhere into the middle of a file, there is
1056            possibility we are writing over some already allocated blocks, so
1057            let's map these blocks and substract number of such blocks out of blocks
1058            we need to allocate (calculated above) */
1059         /* Mask write position to start on blocksize, we do it out of the
1060            loop for performance reasons */
1061         pos &= ~((loff_t) inode->i_sb->s_blocksize - 1);
1062         /* Set cpu key to the starting position in a file (on left block boundary) */
1063         make_cpu_key(&key, inode,
1064                      1 + ((pos) & ~((loff_t) inode->i_sb->s_blocksize - 1)),
1065                      TYPE_ANY, 3 /*key length */ );
1066
1067         reiserfs_write_lock(inode->i_sb);       // We need that for at least search_by_key()
1068         for (i = 0; i < num_pages; i++) {
1069
1070                 head = page_buffers(prepared_pages[i]);
1071                 /* For each buffer in the page */
1072                 for (bh = head, block_start = 0; bh != head || !block_start;
1073                      block_start = block_end, bh = bh->b_this_page) {
1074                         if (!bh)
1075                                 reiserfs_panic(inode->i_sb,
1076                                                "green-9002: Allocated but absent buffer for a page?");
1077                         /* Find where this buffer ends */
1078                         block_end = block_start + inode->i_sb->s_blocksize;
1079                         if (i == 0 && block_end <= from)
1080                                 /* if this buffer is before requested data to map, skip it */
1081                                 continue;
1082
1083                         if (i == num_pages - 1 && block_start >= to) {
1084                                 /* If this buffer is after requested data to map, abort
1085                                    processing of current page */
1086                                 break;
1087                         }
1088
1089                         if (buffer_mapped(bh) && bh->b_blocknr != 0) {
1090                                 /* This is optimisation for a case where buffer is mapped
1091                                    and have blocknumber assigned. In case significant amount
1092                                    of such buffers are present, we may avoid some amount
1093                                    of search_by_key calls.
1094                                    Probably it would be possible to move parts of this code
1095                                    out of BKL, but I afraid that would overcomplicate code
1096                                    without any noticeable benefit.
1097                                  */
1098                                 item_pos++;
1099                                 /* Update the key */
1100                                 set_cpu_key_k_offset(&key,
1101                                                      cpu_key_k_offset(&key) +
1102                                                      inode->i_sb->s_blocksize);
1103                                 blocks--;       // Decrease the amount of blocks that need to be
1104                                 // allocated
1105                                 continue;       // Go to the next buffer
1106                         }
1107
1108                         if (!itembuf || /* if first iteration */
1109                             item_pos >= ih_item_len(ih) / UNFM_P_SIZE) {        /* or if we progressed past the
1110                                                                                    current unformatted_item */
1111                                 /* Try to find next item */
1112                                 res =
1113                                     search_for_position_by_key(inode->i_sb,
1114                                                                &key, &path);
1115                                 /* Abort if no more items */
1116                                 if (res != POSITION_FOUND) {
1117                                         /* make sure later loops don't use this item */
1118                                         itembuf = NULL;
1119                                         item = NULL;
1120                                         break;
1121                                 }
1122
1123                                 /* Update information about current indirect item */
1124                                 itembuf = get_last_bh(&path);
1125                                 ih = get_ih(&path);
1126                                 item = get_item(&path);
1127                                 item_pos = path.pos_in_item;
1128
1129                                 RFALSE(!is_indirect_le_ih(ih),
1130                                        "green-9003: indirect item expected");
1131                         }
1132
1133                         /* See if there is some block associated with the file
1134                            at that position, map the buffer to this block */
1135                         if (get_block_num(item, item_pos)) {
1136                                 map_bh(bh, inode->i_sb,
1137                                        get_block_num(item, item_pos));
1138                                 blocks--;       // Decrease the amount of blocks that need to be
1139                                 // allocated
1140                         }
1141                         item_pos++;
1142                         /* Update the key */
1143                         set_cpu_key_k_offset(&key,
1144                                              cpu_key_k_offset(&key) +
1145                                              inode->i_sb->s_blocksize);
1146                 }
1147         }
1148         pathrelse(&path);       // Free the path
1149         reiserfs_write_unlock(inode->i_sb);
1150
1151         /* Now zero out unmappend buffers for the first and last pages of
1152            write area or issue read requests if page is mapped. */
1153         /* First page, see if it is not uptodate */
1154         if (!PageUptodate(prepared_pages[0])) {
1155                 head = page_buffers(prepared_pages[0]);
1156
1157                 /* For each buffer in page */
1158                 for (bh = head, block_start = 0; bh != head || !block_start;
1159                      block_start = block_end, bh = bh->b_this_page) {
1160
1161                         if (!bh)
1162                                 reiserfs_panic(inode->i_sb,
1163                                                "green-9002: Allocated but absent buffer for a page?");
1164                         /* Find where this buffer ends */
1165                         block_end = block_start + inode->i_sb->s_blocksize;
1166                         if (block_end <= from)
1167                                 /* if this buffer is before requested data to map, skip it */
1168                                 continue;
1169                         if (block_start < from) {       /* Aha, our partial buffer */
1170                                 if (buffer_mapped(bh)) {        /* If it is mapped, we need to
1171                                                                    issue READ request for it to
1172                                                                    not loose data */
1173                                         ll_rw_block(READ, 1, &bh);
1174                                         *wait_bh++ = bh;
1175                                 } else {        /* Not mapped, zero it */
1176                                         char *kaddr =
1177                                             kmap_atomic(prepared_pages[0],
1178                                                         KM_USER0);
1179                                         memset(kaddr + block_start, 0,
1180                                                from - block_start);
1181                                         kunmap_atomic(kaddr, KM_USER0);
1182                                         set_buffer_uptodate(bh);
1183                                 }
1184                         }
1185                 }
1186         }
1187
1188         /* Last page, see if it is not uptodate, or if the last page is past the end of the file. */
1189         if (!PageUptodate(prepared_pages[num_pages - 1]) ||
1190             ((pos + write_bytes) >> PAGE_CACHE_SHIFT) >
1191             (inode->i_size >> PAGE_CACHE_SHIFT)) {
1192                 head = page_buffers(prepared_pages[num_pages - 1]);
1193
1194                 /* for each buffer in page */
1195                 for (bh = head, block_start = 0; bh != head || !block_start;
1196                      block_start = block_end, bh = bh->b_this_page) {
1197
1198                         if (!bh)
1199                                 reiserfs_panic(inode->i_sb,
1200                                                "green-9002: Allocated but absent buffer for a page?");
1201                         /* Find where this buffer ends */
1202                         block_end = block_start + inode->i_sb->s_blocksize;
1203                         if (block_start >= to)
1204                                 /* if this buffer is after requested data to map, skip it */
1205                                 break;
1206                         if (block_end > to) {   /* Aha, our partial buffer */
1207                                 if (buffer_mapped(bh)) {        /* If it is mapped, we need to
1208                                                                    issue READ request for it to
1209                                                                    not loose data */
1210                                         ll_rw_block(READ, 1, &bh);
1211                                         *wait_bh++ = bh;
1212                                 } else {        /* Not mapped, zero it */
1213                                         char *kaddr =
1214                                             kmap_atomic(prepared_pages
1215                                                         [num_pages - 1],
1216                                                         KM_USER0);
1217                                         memset(kaddr + to, 0, block_end - to);
1218                                         kunmap_atomic(kaddr, KM_USER0);
1219                                         set_buffer_uptodate(bh);
1220                                 }
1221                         }
1222                 }
1223         }
1224
1225         /* Wait for read requests we made to happen, if necessary */
1226         while (wait_bh > wait) {
1227                 wait_on_buffer(*--wait_bh);
1228                 if (!buffer_uptodate(*wait_bh)) {
1229                         res = -EIO;
1230                         goto failed_read;
1231                 }
1232         }
1233
1234         return blocks;
1235       failed_page_grabbing:
1236         num_pages = i;
1237       failed_read:
1238         reiserfs_unprepare_pages(prepared_pages, num_pages);
1239         return res;
1240 }
1241
1242 /* Write @count bytes at position @ppos in a file indicated by @file
1243    from the buffer @buf.
1244
1245    generic_file_write() is only appropriate for filesystems that are not seeking to optimize performance and want
1246    something simple that works.  It is not for serious use by general purpose filesystems, excepting the one that it was
1247    written for (ext2/3).  This is for several reasons:
1248
1249    * It has no understanding of any filesystem specific optimizations.
1250
1251    * It enters the filesystem repeatedly for each page that is written.
1252
1253    * It depends on reiserfs_get_block() function which if implemented by reiserfs performs costly search_by_key
1254    * operation for each page it is supplied with. By contrast reiserfs_file_write() feeds as much as possible at a time
1255    * to reiserfs which allows for fewer tree traversals.
1256
1257    * Each indirect pointer insertion takes a lot of cpu, because it involves memory moves inside of blocks.
1258
1259    * Asking the block allocation code for blocks one at a time is slightly less efficient.
1260
1261    All of these reasons for not using only generic file write were understood back when reiserfs was first miscoded to
1262    use it, but we were in a hurry to make code freeze, and so it couldn't be revised then.  This new code should make
1263    things right finally.
1264
1265    Future Features: providing search_by_key with hints.
1266
1267 */
1268 static ssize_t reiserfs_file_write(struct file *file,   /* the file we are going to write into */
1269                                    const char __user * buf,     /*  pointer to user supplied data
1270                                                                    (in userspace) */
1271                                    size_t count,        /* amount of bytes to write */
1272                                    loff_t * ppos        /* pointer to position in file that we start writing at. Should be updated to
1273                                                          * new current position before returning. */
1274                                    )
1275 {
1276         size_t already_written = 0;     // Number of bytes already written to the file.
1277         loff_t pos;             // Current position in the file.
1278         ssize_t res;            // return value of various functions that we call.
1279         int err = 0;
1280         struct inode *inode = file->f_dentry->d_inode;  // Inode of the file that we are writing to.
1281         /* To simplify coding at this time, we store
1282            locked pages in array for now */
1283         struct page *prepared_pages[REISERFS_WRITE_PAGES_AT_A_TIME];
1284         struct reiserfs_transaction_handle th;
1285         th.t_trans_id = 0;
1286
1287         if (file->f_flags & O_DIRECT) { // Direct IO needs treatment
1288                 ssize_t result, after_file_end = 0;
1289                 if ((*ppos + count >= inode->i_size)
1290                     || (file->f_flags & O_APPEND)) {
1291                         /* If we are appending a file, we need to put this savelink in here.
1292                            If we will crash while doing direct io, finish_unfinished will
1293                            cut the garbage from the file end. */
1294                         reiserfs_write_lock(inode->i_sb);
1295                         err =
1296                             journal_begin(&th, inode->i_sb,
1297                                           JOURNAL_PER_BALANCE_CNT);
1298                         if (err) {
1299                                 reiserfs_write_unlock(inode->i_sb);
1300                                 return err;
1301                         }
1302                         reiserfs_update_inode_transaction(inode);
1303                         add_save_link(&th, inode, 1 /* Truncate */ );
1304                         after_file_end = 1;
1305                         err =
1306                             journal_end(&th, inode->i_sb,
1307                                         JOURNAL_PER_BALANCE_CNT);
1308                         reiserfs_write_unlock(inode->i_sb);
1309                         if (err)
1310                                 return err;
1311                 }
1312                 result = generic_file_write(file, buf, count, ppos);
1313
1314                 if (after_file_end) {   /* Now update i_size and remove the savelink */
1315                         struct reiserfs_transaction_handle th;
1316                         reiserfs_write_lock(inode->i_sb);
1317                         err = journal_begin(&th, inode->i_sb, 1);
1318                         if (err) {
1319                                 reiserfs_write_unlock(inode->i_sb);
1320                                 return err;
1321                         }
1322                         reiserfs_update_inode_transaction(inode);
1323                         reiserfs_update_sd(&th, inode);
1324                         err = journal_end(&th, inode->i_sb, 1);
1325                         if (err) {
1326                                 reiserfs_write_unlock(inode->i_sb);
1327                                 return err;
1328                         }
1329                         err = remove_save_link(inode, 1 /* truncate */ );
1330                         reiserfs_write_unlock(inode->i_sb);
1331                         if (err)
1332                                 return err;
1333                 }
1334
1335                 return result;
1336         }
1337
1338         if (unlikely((ssize_t) count < 0))
1339                 return -EINVAL;
1340
1341         if (unlikely(!access_ok(VERIFY_READ, buf, count)))
1342                 return -EFAULT;
1343
1344         down(&inode->i_sem);    // locks the entire file for just us
1345
1346         pos = *ppos;
1347
1348         /* Check if we can write to specified region of file, file
1349            is not overly big and this kind of stuff. Adjust pos and
1350            count, if needed */
1351         res = generic_write_checks(file, &pos, &count, 0);
1352         if (res)
1353                 goto out;
1354
1355         if (count == 0)
1356                 goto out;
1357
1358         res = remove_suid(file->f_dentry);
1359         if (res)
1360                 goto out;
1361
1362         inode_update_time(inode, 1);    /* Both mtime and ctime */
1363
1364         // Ok, we are done with all the checks.
1365
1366         // Now we should start real work
1367
1368         /* If we are going to write past the file's packed tail or if we are going
1369            to overwrite part of the tail, we need that tail to be converted into
1370            unformatted node */
1371         res = reiserfs_check_for_tail_and_convert(inode, pos, count);
1372         if (res)
1373                 goto out;
1374
1375         while (count > 0) {
1376                 /* This is the main loop in which we running until some error occures
1377                    or until we write all of the data. */
1378                 size_t num_pages;       /* amount of pages we are going to write this iteration */
1379                 size_t write_bytes;     /* amount of bytes to write during this iteration */
1380                 size_t blocks_to_allocate;      /* how much blocks we need to allocate for this iteration */
1381
1382                 /*  (pos & (PAGE_CACHE_SIZE-1)) is an idiom for offset into a page of pos */
1383                 num_pages = !!((pos + count) & (PAGE_CACHE_SIZE - 1)) + /* round up partial
1384                                                                            pages */
1385                     ((count +
1386                       (pos & (PAGE_CACHE_SIZE - 1))) >> PAGE_CACHE_SHIFT);
1387                 /* convert size to amount of
1388                    pages */
1389                 reiserfs_write_lock(inode->i_sb);
1390                 if (num_pages > REISERFS_WRITE_PAGES_AT_A_TIME
1391                     || num_pages > reiserfs_can_fit_pages(inode->i_sb)) {
1392                         /* If we were asked to write more data than we want to or if there
1393                            is not that much space, then we shorten amount of data to write
1394                            for this iteration. */
1395                         num_pages =
1396                             min_t(size_t, REISERFS_WRITE_PAGES_AT_A_TIME,
1397                                   reiserfs_can_fit_pages(inode->i_sb));
1398                         /* Also we should not forget to set size in bytes accordingly */
1399                         write_bytes = (num_pages << PAGE_CACHE_SHIFT) -
1400                             (pos & (PAGE_CACHE_SIZE - 1));
1401                         /* If position is not on the
1402                            start of the page, we need
1403                            to substract the offset
1404                            within page */
1405                 } else
1406                         write_bytes = count;
1407
1408                 /* reserve the blocks to be allocated later, so that later on
1409                    we still have the space to write the blocks to */
1410                 reiserfs_claim_blocks_to_be_allocated(inode->i_sb,
1411                                                       num_pages <<
1412                                                       (PAGE_CACHE_SHIFT -
1413                                                        inode->i_blkbits));
1414                 reiserfs_write_unlock(inode->i_sb);
1415
1416                 if (!num_pages) {       /* If we do not have enough space even for a single page... */
1417                         if (pos >
1418                             inode->i_size + inode->i_sb->s_blocksize -
1419                             (pos & (inode->i_sb->s_blocksize - 1))) {
1420                                 res = -ENOSPC;
1421                                 break;  // In case we are writing past the end of the last file block, break.
1422                         }
1423                         // Otherwise we are possibly overwriting the file, so
1424                         // let's set write size to be equal or less than blocksize.
1425                         // This way we get it correctly for file holes.
1426                         // But overwriting files on absolutelly full volumes would not
1427                         // be very efficient. Well, people are not supposed to fill
1428                         // 100% of disk space anyway.
1429                         write_bytes =
1430                             min_t(size_t, count,
1431                                   inode->i_sb->s_blocksize -
1432                                   (pos & (inode->i_sb->s_blocksize - 1)));
1433                         num_pages = 1;
1434                         // No blocks were claimed before, so do it now.
1435                         reiserfs_claim_blocks_to_be_allocated(inode->i_sb,
1436                                                               1 <<
1437                                                               (PAGE_CACHE_SHIFT
1438                                                                -
1439                                                                inode->
1440                                                                i_blkbits));
1441                 }
1442
1443                 /* Prepare for writing into the region, read in all the
1444                    partially overwritten pages, if needed. And lock the pages,
1445                    so that nobody else can access these until we are done.
1446                    We get number of actual blocks needed as a result. */
1447                 blocks_to_allocate =
1448                     reiserfs_prepare_file_region_for_write(inode, pos,
1449                                                            num_pages,
1450                                                            write_bytes,
1451                                                            prepared_pages);
1452                 if (blocks_to_allocate < 0) {
1453                         res = blocks_to_allocate;
1454                         reiserfs_release_claimed_blocks(inode->i_sb,
1455                                                         num_pages <<
1456                                                         (PAGE_CACHE_SHIFT -
1457                                                          inode->i_blkbits));
1458                         break;
1459                 }
1460
1461                 /* First we correct our estimate of how many blocks we need */
1462                 reiserfs_release_claimed_blocks(inode->i_sb,
1463                                                 (num_pages <<
1464                                                  (PAGE_CACHE_SHIFT -
1465                                                   inode->i_sb->
1466                                                   s_blocksize_bits)) -
1467                                                 blocks_to_allocate);
1468
1469                 if (blocks_to_allocate > 0) {   /*We only allocate blocks if we need to */
1470                         /* Fill in all the possible holes and append the file if needed */
1471                         res =
1472                             reiserfs_allocate_blocks_for_region(&th, inode, pos,
1473                                                                 num_pages,
1474                                                                 write_bytes,
1475                                                                 prepared_pages,
1476                                                                 blocks_to_allocate);
1477                 }
1478
1479                 /* well, we have allocated the blocks, so it is time to free
1480                    the reservation we made earlier. */
1481                 reiserfs_release_claimed_blocks(inode->i_sb,
1482                                                 blocks_to_allocate);
1483                 if (res) {
1484                         reiserfs_unprepare_pages(prepared_pages, num_pages);
1485                         break;
1486                 }
1487
1488 /* NOTE that allocating blocks and filling blocks can be done in reverse order
1489    and probably we would do that just to get rid of garbage in files after a
1490    crash */
1491
1492                 /* Copy data from user-supplied buffer to file's pages */
1493                 res =
1494                     reiserfs_copy_from_user_to_file_region(pos, num_pages,
1495                                                            write_bytes,
1496                                                            prepared_pages, buf);
1497                 if (res) {
1498                         reiserfs_unprepare_pages(prepared_pages, num_pages);
1499                         break;
1500                 }
1501
1502                 /* Send the pages to disk and unlock them. */
1503                 res =
1504                     reiserfs_submit_file_region_for_write(&th, inode, pos,
1505                                                           num_pages,
1506                                                           write_bytes,
1507                                                           prepared_pages);
1508                 if (res)
1509                         break;
1510
1511                 already_written += write_bytes;
1512                 buf += write_bytes;
1513                 *ppos = pos += write_bytes;
1514                 count -= write_bytes;
1515                 balance_dirty_pages_ratelimited(inode->i_mapping);
1516         }
1517
1518         /* this is only true on error */
1519         if (th.t_trans_id) {
1520                 reiserfs_write_lock(inode->i_sb);
1521                 err = journal_end(&th, th.t_super, th.t_blocks_allocated);
1522                 reiserfs_write_unlock(inode->i_sb);
1523                 if (err) {
1524                         res = err;
1525                         goto out;
1526                 }
1527         }
1528
1529         if ((file->f_flags & O_SYNC) || IS_SYNC(inode))
1530                 res =
1531                     generic_osync_inode(inode, file->f_mapping,
1532                                         OSYNC_METADATA | OSYNC_DATA);
1533
1534         up(&inode->i_sem);
1535         reiserfs_async_progress_wait(inode->i_sb);
1536         return (already_written != 0) ? already_written : res;
1537
1538       out:
1539         up(&inode->i_sem);      // unlock the file on exit.
1540         return res;
1541 }
1542
1543 static ssize_t reiserfs_aio_write(struct kiocb *iocb, const char __user * buf,
1544                                   size_t count, loff_t pos)
1545 {
1546         return generic_file_aio_write(iocb, buf, count, pos);
1547 }
1548
1549 struct file_operations reiserfs_file_operations = {
1550         .read = generic_file_read,
1551         .write = reiserfs_file_write,
1552         .ioctl = reiserfs_ioctl,
1553         .mmap = generic_file_mmap,
1554         .release = reiserfs_file_release,
1555         .fsync = reiserfs_sync_file,
1556         .sendfile = generic_file_sendfile,
1557         .aio_read = generic_file_aio_read,
1558         .aio_write = reiserfs_aio_write,
1559 };
1560
1561 struct inode_operations reiserfs_file_inode_operations = {
1562         .truncate = reiserfs_vfs_truncate_file,
1563         .setattr = reiserfs_setattr,
1564         .setxattr = reiserfs_setxattr,
1565         .getxattr = reiserfs_getxattr,
1566         .listxattr = reiserfs_listxattr,
1567         .removexattr = reiserfs_removexattr,
1568         .permission = reiserfs_permission,
1569 };