fs/ext4/move_extent.c

   1 /*
   2  * Copyright (c) 2008,2009 NEC Software Tohoku, Ltd.
   3  * Written by Takashi Sato <t-sato@yk.jp.nec.com>
   4  *            Akira Fujita <a-fujita@rs.jp.nec.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of version 2.1 of the GNU Lesser General Public License
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <linux/fs.h>
  17 #include <linux/quotaops.h>
  18 #include <linux/slab.h>
  19 #include "ext4_jbd2.h"
  20 #include "ext4.h"
  21 #include "ext4_extents.h"
  22
  23 /**
  24  * get_ext_path - Find an extent path for designated logical block number.
  25  *
  26  * @inode:      an inode which is searched
  27  * @lblock:     logical block number to find an extent path
  28  * @path:       pointer to an extent path pointer (for output)
  29  *
  30  * ext4_find_extent wrapper. Return 0 on success, or a negative error value
  31  * on failure.
  32  */
  33 static inline int
  34 get_ext_path(struct inode *inode, ext4_lblk_t lblock,
  35                 struct ext4_ext_path **ppath)
  36 {
  37         struct ext4_ext_path *path;
  38
  39         path = ext4_find_extent(inode, lblock, ppath, EXT4_EX_NOCACHE);
  40         if (IS_ERR(path))
  41                 return PTR_ERR(path);
  42         if (path[ext_depth(inode)].p_ext == NULL) {
  43                 ext4_ext_drop_refs(path);
  44                 kfree(path);
  45                 *ppath = NULL;
  46                 return -ENODATA;
  47         }
  48         *ppath = path;
  49         return 0;
  50 }
  51
  52 /**
  53  * ext4_double_down_write_data_sem - Acquire two inodes' write lock
  54  *                                   of i_data_sem
  55  *
  56  * Acquire write lock of i_data_sem of the two inodes
  57  */
  58 void
  59 ext4_double_down_write_data_sem(struct inode *first, struct inode *second)
  60 {
  61         if (first < second) {
  62                 down_write(&EXT4_I(first)->i_data_sem);
  63                 down_write_nested(&EXT4_I(second)->i_data_sem, SINGLE_DEPTH_NESTING);
  64         } else {
  65                 down_write(&EXT4_I(second)->i_data_sem);
  66                 down_write_nested(&EXT4_I(first)->i_data_sem, SINGLE_DEPTH_NESTING);
  67
  68         }
  69 }
  70
  71 /**
  72  * ext4_double_up_write_data_sem - Release two inodes' write lock of i_data_sem
  73  *
  74  * @orig_inode:         original inode structure to be released its lock first
  75  * @donor_inode:        donor inode structure to be released its lock second
  76  * Release write lock of i_data_sem of two inodes (orig and donor).
  77  */
  78 void
  79 ext4_double_up_write_data_sem(struct inode *orig_inode,
  80                               struct inode *donor_inode)
  81 {
  82         up_write(&EXT4_I(orig_inode)->i_data_sem);
  83         up_write(&EXT4_I(donor_inode)->i_data_sem);
  84 }
  85
  86 /**
  87  * mext_check_coverage - Check that all extents in range has the same type
  88  *
  89  * @inode:              inode in question
  90  * @from:               block offset of inode
  91  * @count:              block count to be checked
  92  * @unwritten:          extents expected to be unwritten
  93  * @err:                pointer to save error value
  94  *
  95  * Return 1 if all extents in range has expected type, and zero otherwise.
  96  */
  97 static int
  98 mext_check_coverage(struct inode *inode, ext4_lblk_t from, ext4_lblk_t count,
  99                     int unwritten, int *err)
 100 {
 101         struct ext4_ext_path *path = NULL;
 102         struct ext4_extent *ext;
 103         int ret = 0;
 104         ext4_lblk_t last = from + count;
 105         while (from < last) {
 106                 *err = get_ext_path(inode, from, &path);
 107                 if (*err)
 108                         goto out;
 109                 ext = path[ext_depth(inode)].p_ext;
 110                 if (unwritten != ext4_ext_is_unwritten(ext))
 111                         goto out;
 112                 from += ext4_ext_get_actual_len(ext);
 113                 ext4_ext_drop_refs(path);
 114         }
 115         ret = 1;
 116 out:
 117         ext4_ext_drop_refs(path);
 118         kfree(path);
 119         return ret;
 120 }
 121
 122 /**
 123  * mext_page_double_lock - Grab and lock pages on both @inode1 and @inode2
 124  *
 125  * @inode1:     the inode structure
 126  * @inode2:     the inode structure
 127  * @index1:     page index
 128  * @index2:     page index
 129  * @page:       result page vector
 130  *
 131  * Grab two locked pages for inode's by inode order
 132  */
 133 static int
 134 mext_page_double_lock(struct inode *inode1, struct inode *inode2,
 135                       pgoff_t index1, pgoff_t index2, struct page *page[2])
 136 {
 137         struct address_space *mapping[2];
 138         unsigned fl = AOP_FLAG_NOFS;
 139
 140         BUG_ON(!inode1 || !inode2);
 141         if (inode1 < inode2) {
 142                 mapping[0] = inode1->i_mapping;
 143                 mapping[1] = inode2->i_mapping;
 144         } else {
 145                 pgoff_t tmp = index1;
 146                 index1 = index2;
 147                 index2 = tmp;
 148                 mapping[0] = inode2->i_mapping;
 149                 mapping[1] = inode1->i_mapping;
 150         }
 151
 152         page[0] = grab_cache_page_write_begin(mapping[0], index1, fl);
 153         if (!page[0])
 154                 return -ENOMEM;
 155
 156         page[1] = grab_cache_page_write_begin(mapping[1], index2, fl);
 157         if (!page[1]) {
 158                 unlock_page(page[0]);
 159                 page_cache_release(page[0]);
 160                 return -ENOMEM;
 161         }
 162         /*
 163          * grab_cache_page_write_begin() may not wait on page's writeback if
 164          * BDI not demand that. But it is reasonable to be very conservative
 165          * here and explicitly wait on page's writeback
 166          */
 167         wait_on_page_writeback(page[0]);
 168         wait_on_page_writeback(page[1]);
 169         if (inode1 > inode2)
 170                 swap(page[0], page[1]);
 171
 172         return 0;
 173 }
 174
 175 /* Force page buffers uptodate w/o dropping page's lock */
 176 static int
 177 mext_page_mkuptodate(struct page *page, unsigned from, unsigned to)
 178 {
 179         struct inode *inode = page->mapping->host;
 180         sector_t block;
 181         struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
 182         unsigned int blocksize, block_start, block_end;
 183         int i, err,  nr = 0, partial = 0;
 184         BUG_ON(!PageLocked(page));
 185         BUG_ON(PageWriteback(page));
 186
 187         if (PageUptodate(page))
 188                 return 0;
 189
 190         blocksize = 1 << inode->i_blkbits;
 191         if (!page_has_buffers(page))
 192                 create_empty_buffers(page, blocksize, 0);
 193
 194         head = page_buffers(page);
 195         block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
 196         for (bh = head, block_start = 0; bh != head || !block_start;
 197              block++, block_start = block_end, bh = bh->b_this_page) {
 198                 block_end = block_start + blocksize;
 199                 if (block_end <= from || block_start >= to) {
 200                         if (!buffer_uptodate(bh))
 201                                 partial = 1;
 202                         continue;
 203                 }
 204                 if (buffer_uptodate(bh))
 205                         continue;
 206                 if (!buffer_mapped(bh)) {
 207                         err = ext4_get_block(inode, block, bh, 0);
 208                         if (err) {
 209                                 SetPageError(page);
 210                                 return err;
 211                         }
 212                         if (!buffer_mapped(bh)) {
 213                                 zero_user(page, block_start, blocksize);
 214                                 set_buffer_uptodate(bh);
 215                                 continue;
 216                         }
 217                 }
 218                 BUG_ON(nr >= MAX_BUF_PER_PAGE);
 219                 arr[nr++] = bh;
 220         }
 221         /* No io required */
 222         if (!nr)
 223                 goto out;
 224
 225         for (i = 0; i < nr; i++) {
 226                 bh = arr[i];
 227                 if (!bh_uptodate_or_lock(bh)) {
 228                         err = bh_submit_read(bh);
 229                         if (err)
 230                                 return err;
 231                 }
 232         }
 233 out:
 234         if (!partial)
 235                 SetPageUptodate(page);
 236         return 0;
 237 }
 238
 239 /**
 240  * move_extent_per_page - Move extent data per page
 241  *
 242  * @o_filp:                     file structure of original file
 243  * @donor_inode:                donor inode
 244  * @orig_page_offset:           page index on original file
 245  * @donor_page_offset:          page index on donor file
 246  * @data_offset_in_page:        block index where data swapping starts
 247  * @block_len_in_page:          the number of blocks to be swapped
 248  * @unwritten:                  orig extent is unwritten or not
 249  * @err:                        pointer to save return value
 250  *
 251  * Save the data in original inode blocks and replace original inode extents
 252  * with donor inode extents by calling ext4_swap_extents().
 253  * Finally, write out the saved data in new original inode blocks. Return
 254  * replaced block count.
 255  */
 256 static int
 257 move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
 258                      pgoff_t orig_page_offset, pgoff_t donor_page_offset,
 259                      int data_offset_in_page,
 260                      int block_len_in_page, int unwritten, int *err)
 261 {
 262         struct inode *orig_inode = file_inode(o_filp);
 263         struct page *pagep[2] = {NULL, NULL};
 264         handle_t *handle;
 265         ext4_lblk_t orig_blk_offset, donor_blk_offset;
 266         unsigned long blocksize = orig_inode->i_sb->s_blocksize;
 267         unsigned int tmp_data_size, data_size, replaced_size;
 268         int err2, jblocks, retries = 0;
 269         int replaced_count = 0;
 270         int from = data_offset_in_page << orig_inode->i_blkbits;
 271         int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
 272         struct super_block *sb = orig_inode->i_sb;
 273
 274         /*
 275          * It needs twice the amount of ordinary journal buffers because
 276          * inode and donor_inode may change each different metadata blocks.
 277          */
 278 again:
 279         *err = 0;
 280         jblocks = ext4_writepage_trans_blocks(orig_inode) * 2;
 281         handle = ext4_journal_start(orig_inode, EXT4_HT_MOVE_EXTENTS, jblocks);
 282         if (IS_ERR(handle)) {
 283                 *err = PTR_ERR(handle);
 284                 return 0;
 285         }
 286
 287         orig_blk_offset = orig_page_offset * blocks_per_page +
 288                 data_offset_in_page;
 289
 290         donor_blk_offset = donor_page_offset * blocks_per_page +
 291                 data_offset_in_page;
 292
 293         /* Calculate data_size */
 294         if ((orig_blk_offset + block_len_in_page - 1) ==
 295             ((orig_inode->i_size - 1) >> orig_inode->i_blkbits)) {
 296                 /* Replace the last block */
 297                 tmp_data_size = orig_inode->i_size & (blocksize - 1);
 298                 /*
 299                  * If data_size equal zero, it shows data_size is multiples of
 300                  * blocksize. So we set appropriate value.
 301                  */
 302                 if (tmp_data_size == 0)
 303                         tmp_data_size = blocksize;
 304
 305                 data_size = tmp_data_size +
 306                         ((block_len_in_page - 1) << orig_inode->i_blkbits);
 307         } else
 308                 data_size = block_len_in_page << orig_inode->i_blkbits;
 309
 310         replaced_size = data_size;
 311
 312         *err = mext_page_double_lock(orig_inode, donor_inode, orig_page_offset,
 313                                      donor_page_offset, pagep);
 314         if (unlikely(*err < 0))
 315                 goto stop_journal;
 316         /*
 317          * If orig extent was unwritten it can become initialized
 318          * at any time after i_data_sem was dropped, in order to
 319          * serialize with delalloc we have recheck extent while we
 320          * hold page's lock, if it is still the case data copy is not
 321          * necessary, just swap data blocks between orig and donor.
 322          */
 323         if (unwritten) {
 324                 ext4_double_down_write_data_sem(orig_inode, donor_inode);
 325                 /* If any of extents in range became initialized we have to
 326                  * fallback to data copying */
 327                 unwritten = mext_check_coverage(orig_inode, orig_blk_offset,
 328                                                 block_len_in_page, 1, err);
 329                 if (*err)
 330                         goto drop_data_sem;
 331
 332                 unwritten &= mext_check_coverage(donor_inode, donor_blk_offset,
 333                                                  block_len_in_page, 1, err);
 334                 if (*err)
 335                         goto drop_data_sem;
 336
 337                 if (!unwritten) {
 338                         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 339                         goto data_copy;
 340                 }
 341                 if ((page_has_private(pagep[0]) &&
 342                      !try_to_release_page(pagep[0], 0)) ||
 343                     (page_has_private(pagep[1]) &&
 344                      !try_to_release_page(pagep[1], 0))) {
 345                         *err = -EBUSY;
 346                         goto drop_data_sem;
 347                 }
 348                 replaced_count = ext4_swap_extents(handle, orig_inode,
 349                                                    donor_inode, orig_blk_offset,
 350                                                    donor_blk_offset,
 351                                                    block_len_in_page, 1, err);
 352         drop_data_sem:
 353                 ext4_double_up_write_data_sem(orig_inode, donor_inode);
 354                 goto unlock_pages;
 355         }
 356 data_copy:
 357         *err = mext_page_mkuptodate(pagep[0], from, from + replaced_size);
 358         if (*err)
 359                 goto unlock_pages;
 360
 361         /* At this point all buffers in range are uptodate, old mapping layout
 362          * is no longer required, try to drop it now. */
 363         if ((page_has_private(pagep[0]) && !try_to_release_page(pagep[0], 0)) ||
 364             (page_has_private(pagep[1]) && !try_to_release_page(pagep[1], 0))) {
 365                 *err = -EBUSY;
 366                 goto unlock_pages;
 367         }
 368         ext4_double_down_write_data_sem(orig_inode, donor_inode);
 369         replaced_count = ext4_swap_extents(handle, orig_inode, donor_inode,
 370                                                orig_blk_offset, donor_blk_offset,
 371                                            block_len_in_page, 1, err);
 372         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 373         if (*err) {
 374                 if (replaced_count) {
 375                         block_len_in_page = replaced_count;
 376                         replaced_size =
 377                                 block_len_in_page << orig_inode->i_blkbits;
 378                 } else
 379                         goto unlock_pages;
 380         }
 381         /* Perform all necessary steps similar write_begin()/write_end()
 382          * but keeping in mind that i_size will not change */
 383         *err = __block_write_begin(pagep[0], from, replaced_size,
 384                                    ext4_get_block);
 385         if (!*err)
 386                 *err = block_commit_write(pagep[0], from, from + replaced_size);
 387
 388         if (unlikely(*err < 0))
 389                 goto repair_branches;
 390
 391         /* Even in case of data=writeback it is reasonable to pin
 392          * inode to transaction, to prevent unexpected data loss */
 393         *err = ext4_jbd2_file_inode(handle, orig_inode);
 394
 395 unlock_pages:
 396         unlock_page(pagep[0]);
 397         page_cache_release(pagep[0]);
 398         unlock_page(pagep[1]);
 399         page_cache_release(pagep[1]);
 400 stop_journal:
 401         ext4_journal_stop(handle);
 402         if (*err == -ENOSPC &&
 403             ext4_should_retry_alloc(sb, &retries))
 404                 goto again;
 405         /* Buffer was busy because probably is pinned to journal transaction,
 406          * force transaction commit may help to free it. */
 407         if (*err == -EBUSY && retries++ < 4 && EXT4_SB(sb)->s_journal &&
 408             jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal))
 409                 goto again;
 410         return replaced_count;
 411
 412 repair_branches:
 413         /*
 414          * This should never ever happen!
 415          * Extents are swapped already, but we are not able to copy data.
 416          * Try to swap extents to it's original places
 417          */
 418         ext4_double_down_write_data_sem(orig_inode, donor_inode);
 419         replaced_count = ext4_swap_extents(handle, donor_inode, orig_inode,
 420                                                orig_blk_offset, donor_blk_offset,
 421                                            block_len_in_page, 0, &err2);
 422         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 423         if (replaced_count != block_len_in_page) {
 424                 EXT4_ERROR_INODE_BLOCK(orig_inode, (sector_t)(orig_blk_offset),
 425                                        "Unable to copy data block,"
 426                                        " data will be lost.");
 427                 *err = -EIO;
 428         }
 429         replaced_count = 0;
 430         goto unlock_pages;
 431 }
 432
 433 /**
 434  * mext_check_arguments - Check whether move extent can be done
 435  *
 436  * @orig_inode:         original inode
 437  * @donor_inode:        donor inode
 438  * @orig_start:         logical start offset in block for orig
 439  * @donor_start:        logical start offset in block for donor
 440  * @len:                the number of blocks to be moved
 441  *
 442  * Check the arguments of ext4_move_extents() whether the files can be
 443  * exchanged with each other.
 444  * Return 0 on success, or a negative error value on failure.
 445  */
 446 static int
 447 mext_check_arguments(struct inode *orig_inode,
 448                      struct inode *donor_inode, __u64 orig_start,
 449                      __u64 donor_start, __u64 *len)
 450 {
 451         __u64 orig_eof, donor_eof;
 452         unsigned int blkbits = orig_inode->i_blkbits;
 453         unsigned int blocksize = 1 << blkbits;
 454
 455         orig_eof = (i_size_read(orig_inode) + blocksize - 1) >> blkbits;
 456         donor_eof = (i_size_read(donor_inode) + blocksize - 1) >> blkbits;
 457
 458
 459         if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
 460                 ext4_debug("ext4 move extent: suid or sgid is set"
 461                            " to donor file [ino:orig %lu, donor %lu]\n",
 462                            orig_inode->i_ino, donor_inode->i_ino);
 463                 return -EINVAL;
 464         }
 465
 466         if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
 467                 return -EPERM;
 468
 469         /* Ext4 move extent does not support swapfile */
 470         if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
 471                 ext4_debug("ext4 move extent: The argument files should "
 472                         "not be swapfile [ino:orig %lu, donor %lu]\n",
 473                         orig_inode->i_ino, donor_inode->i_ino);
 474                 return -EBUSY;
 475         }
 476
 477         /* Ext4 move extent supports only extent based file */
 478         if (!(ext4_test_inode_flag(orig_inode, EXT4_INODE_EXTENTS))) {
 479                 ext4_debug("ext4 move extent: orig file is not extents "
 480                         "based file [ino:orig %lu]\n", orig_inode->i_ino);
 481                 return -EOPNOTSUPP;
 482         } else if (!(ext4_test_inode_flag(donor_inode, EXT4_INODE_EXTENTS))) {
 483                 ext4_debug("ext4 move extent: donor file is not extents "
 484                         "based file [ino:donor %lu]\n", donor_inode->i_ino);
 485                 return -EOPNOTSUPP;
 486         }
 487
 488         if ((!orig_inode->i_size) || (!donor_inode->i_size)) {
 489                 ext4_debug("ext4 move extent: File size is 0 byte\n");
 490                 return -EINVAL;
 491         }
 492
 493         /* Start offset should be same */
 494         if ((orig_start & ~(PAGE_MASK >> orig_inode->i_blkbits)) !=
 495             (donor_start & ~(PAGE_MASK >> orig_inode->i_blkbits))) {
 496                 ext4_debug("ext4 move extent: orig and donor's start "
 497                         "offset are not alligned [ino:orig %lu, donor %lu]\n",
 498                         orig_inode->i_ino, donor_inode->i_ino);
 499                 return -EINVAL;
 500         }
 501
 502         if ((orig_start >= EXT_MAX_BLOCKS) ||
 503             (donor_start >= EXT_MAX_BLOCKS) ||
 504             (*len > EXT_MAX_BLOCKS) ||
 505             (donor_start + *len >= EXT_MAX_BLOCKS) ||
 506             (orig_start + *len >= EXT_MAX_BLOCKS))  {
 507                 ext4_debug("ext4 move extent: Can't handle over [%u] blocks "
 508                         "[ino:orig %lu, donor %lu]\n", EXT_MAX_BLOCKS,
 509                         orig_inode->i_ino, donor_inode->i_ino);
 510                 return -EINVAL;
 511         }
 512         if (orig_eof < orig_start + *len - 1)
 513                 *len = orig_eof - orig_start;
 514         if (donor_eof < donor_start + *len - 1)
 515                 *len = donor_eof - donor_start;
 516         if (!*len) {
 517                 ext4_debug("ext4 move extent: len should not be 0 "
 518                         "[ino:orig %lu, donor %lu]\n", orig_inode->i_ino,
 519                         donor_inode->i_ino);
 520                 return -EINVAL;
 521         }
 522
 523         return 0;
 524 }
 525
 526 /**
 527  * ext4_move_extents - Exchange the specified range of a file
 528  *
 529  * @o_filp:             file structure of the original file
 530  * @d_filp:             file structure of the donor file
 531  * @orig_blk:           start offset in block for orig
 532  * @donor_blk:          start offset in block for donor
 533  * @len:                the number of blocks to be moved
 534  * @moved_len:          moved block length
 535  *
 536  * This function returns 0 and moved block length is set in moved_len
 537  * if succeed, otherwise returns error value.
 538  *
 539  */
 540 int
 541 ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 542                   __u64 donor_blk, __u64 len, __u64 *moved_len)
 543 {
 544         struct inode *orig_inode = file_inode(o_filp);
 545         struct inode *donor_inode = file_inode(d_filp);
 546         struct ext4_ext_path *path = NULL;
 547         int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
 548         ext4_lblk_t o_end, o_start = orig_blk;
 549         ext4_lblk_t d_start = donor_blk;
 550         int ret;
 551
 552         if (orig_inode->i_sb != donor_inode->i_sb) {
 553                 ext4_debug("ext4 move extent: The argument files "
 554                         "should be in same FS [ino:orig %lu, donor %lu]\n",
 555                         orig_inode->i_ino, donor_inode->i_ino);
 556                 return -EINVAL;
 557         }
 558
 559         /* orig and donor should be different inodes */
 560         if (orig_inode == donor_inode) {
 561                 ext4_debug("ext4 move extent: The argument files should not "
 562                         "be same inode [ino:orig %lu, donor %lu]\n",
 563                         orig_inode->i_ino, donor_inode->i_ino);
 564                 return -EINVAL;
 565         }
 566
 567         /* Regular file check */
 568         if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
 569                 ext4_debug("ext4 move extent: The argument files should be "
 570                         "regular file [ino:orig %lu, donor %lu]\n",
 571                         orig_inode->i_ino, donor_inode->i_ino);
 572                 return -EINVAL;
 573         }
 574         /* TODO: This is non obvious task to swap blocks for inodes with full
 575            jornaling enabled */
 576         if (ext4_should_journal_data(orig_inode) ||
 577             ext4_should_journal_data(donor_inode)) {
 578                 return -EINVAL;
 579         }
 580         /* Protect orig and donor inodes against a truncate */
 581         lock_two_nondirectories(orig_inode, donor_inode);
 582
 583         /* Wait for all existing dio workers */
 584         ext4_inode_block_unlocked_dio(orig_inode);
 585         ext4_inode_block_unlocked_dio(donor_inode);
 586         inode_dio_wait(orig_inode);
 587         inode_dio_wait(donor_inode);
 588
 589         /* Protect extent tree against block allocations via delalloc */
 590         ext4_double_down_write_data_sem(orig_inode, donor_inode);
 591         /* Check the filesystem environment whether move_extent can be done */
 592         ret = mext_check_arguments(orig_inode, donor_inode, orig_blk,
 593                                     donor_blk, &len);
 594         if (ret)
 595                 goto out;
 596         o_end = o_start + len;
 597
 598         while (o_start < o_end) {
 599                 struct ext4_extent *ex;
 600                 ext4_lblk_t cur_blk, next_blk;
 601                 pgoff_t orig_page_index, donor_page_index;
 602                 int offset_in_page;
 603                 int unwritten, cur_len;
 604
 605                 ret = get_ext_path(orig_inode, o_start, &path);
 606                 if (ret)
 607                         goto out;
 608                 ex = path[path->p_depth].p_ext;
 609                 next_blk = ext4_ext_next_allocated_block(path);
 610                 cur_blk = le32_to_cpu(ex->ee_block);
 611                 cur_len = ext4_ext_get_actual_len(ex);
 612                 /* Check hole before the start pos */
 613                 if (cur_blk + cur_len - 1 < o_start) {
 614                         if (next_blk == EXT_MAX_BLOCKS) {
 615                                 o_start = o_end;
 616                                 ret = -ENODATA;
 617                                 goto out;
 618                         }
 619                         d_start += next_blk - o_start;
 620                         o_start = next_blk;
 621                         continue;
 622                 /* Check hole after the start pos */
 623                 } else if (cur_blk > o_start) {
 624                         /* Skip hole */
 625                         d_start += cur_blk - o_start;
 626                         o_start = cur_blk;
 627                         /* Extent inside requested range ?*/
 628                         if (cur_blk >= o_end)
 629                                 goto out;
 630                 } else { /* in_range(o_start, o_blk, o_len) */
 631                         cur_len += cur_blk - o_start;
 632                 }
 633                 unwritten = ext4_ext_is_unwritten(ex);
 634                 if (o_end - o_start < cur_len)
 635                         cur_len = o_end - o_start;
 636
 637                 orig_page_index = o_start >> (PAGE_CACHE_SHIFT -
 638                                                orig_inode->i_blkbits);
 639                 donor_page_index = d_start >> (PAGE_CACHE_SHIFT -
 640                                                donor_inode->i_blkbits);
 641                 offset_in_page = o_start % blocks_per_page;
 642                 if (cur_len > blocks_per_page- offset_in_page)
 643                         cur_len = blocks_per_page - offset_in_page;
 644                 /*
 645                  * Up semaphore to avoid following problems:
 646                  * a. transaction deadlock among ext4_journal_start,
 647                  *    ->write_begin via pagefault, and jbd2_journal_commit
 648                  * b. racing with ->readpage, ->write_begin, and ext4_get_block
 649                  *    in move_extent_per_page
 650                  */
 651                 ext4_double_up_write_data_sem(orig_inode, donor_inode);
 652                 /* Swap original branches with new branches */
 653                 move_extent_per_page(o_filp, donor_inode,
 654                                      orig_page_index, donor_page_index,
 655                                      offset_in_page, cur_len,
 656                                      unwritten, &ret);
 657                 ext4_double_down_write_data_sem(orig_inode, donor_inode);
 658                 if (ret < 0)
 659                         break;
 660                 o_start += cur_len;
 661                 d_start += cur_len;
 662         }
 663         *moved_len = o_start - orig_blk;
 664         if (*moved_len > len)
 665                 *moved_len = len;
 666
 667 out:
 668         if (*moved_len) {
 669                 ext4_discard_preallocations(orig_inode);
 670                 ext4_discard_preallocations(donor_inode);
 671         }
 672
 673         ext4_ext_drop_refs(path);
 674         kfree(path);
 675         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 676         ext4_inode_resume_unlocked_dio(orig_inode);
 677         ext4_inode_resume_unlocked_dio(donor_inode);
 678         unlock_two_nondirectories(orig_inode, donor_inode);
 679
 680         return ret;
 681 }