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                 struct page *tmp;
 171                 tmp = page[0];
 172                 page[0] = page[1];
 173                 page[1] = tmp;
 174         }
 175         return 0;
 176 }
 177
 178 /* Force page buffers uptodate w/o dropping page's lock */
 179 static int
 180 mext_page_mkuptodate(struct page *page, unsigned from, unsigned to)
 181 {
 182         struct inode *inode = page->mapping->host;
 183         sector_t block;
 184         struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
 185         unsigned int blocksize, block_start, block_end;
 186         int i, err,  nr = 0, partial = 0;
 187         BUG_ON(!PageLocked(page));
 188         BUG_ON(PageWriteback(page));
 189
 190         if (PageUptodate(page))
 191                 return 0;
 192
 193         blocksize = 1 << inode->i_blkbits;
 194         if (!page_has_buffers(page))
 195                 create_empty_buffers(page, blocksize, 0);
 196
 197         head = page_buffers(page);
 198         block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
 199         for (bh = head, block_start = 0; bh != head || !block_start;
 200              block++, block_start = block_end, bh = bh->b_this_page) {
 201                 block_end = block_start + blocksize;
 202                 if (block_end <= from || block_start >= to) {
 203                         if (!buffer_uptodate(bh))
 204                                 partial = 1;
 205                         continue;
 206                 }
 207                 if (buffer_uptodate(bh))
 208                         continue;
 209                 if (!buffer_mapped(bh)) {
 210                         err = ext4_get_block(inode, block, bh, 0);
 211                         if (err) {
 212                                 SetPageError(page);
 213                                 return err;
 214                         }
 215                         if (!buffer_mapped(bh)) {
 216                                 zero_user(page, block_start, blocksize);
 217                                 set_buffer_uptodate(bh);
 218                                 continue;
 219                         }
 220                 }
 221                 BUG_ON(nr >= MAX_BUF_PER_PAGE);
 222                 arr[nr++] = bh;
 223         }
 224         /* No io required */
 225         if (!nr)
 226                 goto out;
 227
 228         for (i = 0; i < nr; i++) {
 229                 bh = arr[i];
 230                 if (!bh_uptodate_or_lock(bh)) {
 231                         err = bh_submit_read(bh);
 232                         if (err)
 233                                 return err;
 234                 }
 235         }
 236 out:
 237         if (!partial)
 238                 SetPageUptodate(page);
 239         return 0;
 240 }
 241
 242 /**
 243  * move_extent_per_page - Move extent data per page
 244  *
 245  * @o_filp:                     file structure of original file
 246  * @donor_inode:                donor inode
 247  * @orig_page_offset:           page index on original file
 248  * @donor_page_offset:          page index on donor file
 249  * @data_offset_in_page:        block index where data swapping starts
 250  * @block_len_in_page:          the number of blocks to be swapped
 251  * @unwritten:                  orig extent is unwritten or not
 252  * @err:                        pointer to save return value
 253  *
 254  * Save the data in original inode blocks and replace original inode extents
 255  * with donor inode extents by calling ext4_swap_extents().
 256  * Finally, write out the saved data in new original inode blocks. Return
 257  * replaced block count.
 258  */
 259 static int
 260 move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
 261                      pgoff_t orig_page_offset, pgoff_t donor_page_offset,
 262                      int data_offset_in_page,
 263                      int block_len_in_page, int unwritten, int *err)
 264 {
 265         struct inode *orig_inode = file_inode(o_filp);
 266         struct page *pagep[2] = {NULL, NULL};
 267         handle_t *handle;
 268         ext4_lblk_t orig_blk_offset, donor_blk_offset;
 269         unsigned long blocksize = orig_inode->i_sb->s_blocksize;
 270         unsigned int tmp_data_size, data_size, replaced_size;
 271         int err2, jblocks, retries = 0;
 272         int replaced_count = 0;
 273         int from = data_offset_in_page << orig_inode->i_blkbits;
 274         int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
 275         struct super_block *sb = orig_inode->i_sb;
 276
 277         /*
 278          * It needs twice the amount of ordinary journal buffers because
 279          * inode and donor_inode may change each different metadata blocks.
 280          */
 281 again:
 282         *err = 0;
 283         jblocks = ext4_writepage_trans_blocks(orig_inode) * 2;
 284         handle = ext4_journal_start(orig_inode, EXT4_HT_MOVE_EXTENTS, jblocks);
 285         if (IS_ERR(handle)) {
 286                 *err = PTR_ERR(handle);
 287                 return 0;
 288         }
 289
 290         orig_blk_offset = orig_page_offset * blocks_per_page +
 291                 data_offset_in_page;
 292
 293         donor_blk_offset = donor_page_offset * blocks_per_page +
 294                 data_offset_in_page;
 295
 296         /* Calculate data_size */
 297         if ((orig_blk_offset + block_len_in_page - 1) ==
 298             ((orig_inode->i_size - 1) >> orig_inode->i_blkbits)) {
 299                 /* Replace the last block */
 300                 tmp_data_size = orig_inode->i_size & (blocksize - 1);
 301                 /*
 302                  * If data_size equal zero, it shows data_size is multiples of
 303                  * blocksize. So we set appropriate value.
 304                  */
 305                 if (tmp_data_size == 0)
 306                         tmp_data_size = blocksize;
 307
 308                 data_size = tmp_data_size +
 309                         ((block_len_in_page - 1) << orig_inode->i_blkbits);
 310         } else
 311                 data_size = block_len_in_page << orig_inode->i_blkbits;
 312
 313         replaced_size = data_size;
 314
 315         *err = mext_page_double_lock(orig_inode, donor_inode, orig_page_offset,
 316                                      donor_page_offset, pagep);
 317         if (unlikely(*err < 0))
 318                 goto stop_journal;
 319         /*
 320          * If orig extent was unwritten it can become initialized
 321          * at any time after i_data_sem was dropped, in order to
 322          * serialize with delalloc we have recheck extent while we
 323          * hold page's lock, if it is still the case data copy is not
 324          * necessary, just swap data blocks between orig and donor.
 325          */
 326         if (unwritten) {
 327                 ext4_double_down_write_data_sem(orig_inode, donor_inode);
 328                 /* If any of extents in range became initialized we have to
 329                  * fallback to data copying */
 330                 unwritten = mext_check_coverage(orig_inode, orig_blk_offset,
 331                                                 block_len_in_page, 1, err);
 332                 if (*err)
 333                         goto drop_data_sem;
 334
 335                 unwritten &= mext_check_coverage(donor_inode, donor_blk_offset,
 336                                                  block_len_in_page, 1, err);
 337                 if (*err)
 338                         goto drop_data_sem;
 339
 340                 if (!unwritten) {
 341                         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 342                         goto data_copy;
 343                 }
 344                 if ((page_has_private(pagep[0]) &&
 345                      !try_to_release_page(pagep[0], 0)) ||
 346                     (page_has_private(pagep[1]) &&
 347                      !try_to_release_page(pagep[1], 0))) {
 348                         *err = -EBUSY;
 349                         goto drop_data_sem;
 350                 }
 351                 replaced_count = ext4_swap_extents(handle, orig_inode,
 352                                                    donor_inode, orig_blk_offset,
 353                                                    donor_blk_offset,
 354                                                    block_len_in_page, 1, err);
 355         drop_data_sem:
 356                 ext4_double_up_write_data_sem(orig_inode, donor_inode);
 357                 goto unlock_pages;
 358         }
 359 data_copy:
 360         *err = mext_page_mkuptodate(pagep[0], from, from + replaced_size);
 361         if (*err)
 362                 goto unlock_pages;
 363
 364         /* At this point all buffers in range are uptodate, old mapping layout
 365          * is no longer required, try to drop it now. */
 366         if ((page_has_private(pagep[0]) && !try_to_release_page(pagep[0], 0)) ||
 367             (page_has_private(pagep[1]) && !try_to_release_page(pagep[1], 0))) {
 368                 *err = -EBUSY;
 369                 goto unlock_pages;
 370         }
 371         ext4_double_down_write_data_sem(orig_inode, donor_inode);
 372         replaced_count = ext4_swap_extents(handle, orig_inode, donor_inode,
 373                                                orig_blk_offset, donor_blk_offset,
 374                                            block_len_in_page, 1, err);
 375         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 376         if (*err) {
 377                 if (replaced_count) {
 378                         block_len_in_page = replaced_count;
 379                         replaced_size =
 380                                 block_len_in_page << orig_inode->i_blkbits;
 381                 } else
 382                         goto unlock_pages;
 383         }
 384         /* Perform all necessary steps similar write_begin()/write_end()
 385          * but keeping in mind that i_size will not change */
 386         *err = __block_write_begin(pagep[0], from, replaced_size,
 387                                    ext4_get_block);
 388         if (!*err)
 389                 *err = block_commit_write(pagep[0], from, from + replaced_size);
 390
 391         if (unlikely(*err < 0))
 392                 goto repair_branches;
 393
 394         /* Even in case of data=writeback it is reasonable to pin
 395          * inode to transaction, to prevent unexpected data loss */
 396         *err = ext4_jbd2_file_inode(handle, orig_inode);
 397
 398 unlock_pages:
 399         unlock_page(pagep[0]);
 400         page_cache_release(pagep[0]);
 401         unlock_page(pagep[1]);
 402         page_cache_release(pagep[1]);
 403 stop_journal:
 404         ext4_journal_stop(handle);
 405         if (*err == -ENOSPC &&
 406             ext4_should_retry_alloc(sb, &retries))
 407                 goto again;
 408         /* Buffer was busy because probably is pinned to journal transaction,
 409          * force transaction commit may help to free it. */
 410         if (*err == -EBUSY && retries++ < 4 && EXT4_SB(sb)->s_journal &&
 411             jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal))
 412                 goto again;
 413         return replaced_count;
 414
 415 repair_branches:
 416         /*
 417          * This should never ever happen!
 418          * Extents are swapped already, but we are not able to copy data.
 419          * Try to swap extents to it's original places
 420          */
 421         ext4_double_down_write_data_sem(orig_inode, donor_inode);
 422         replaced_count = ext4_swap_extents(handle, donor_inode, orig_inode,
 423                                                orig_blk_offset, donor_blk_offset,
 424                                            block_len_in_page, 0, &err2);
 425         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 426         if (replaced_count != block_len_in_page) {
 427                 EXT4_ERROR_INODE_BLOCK(orig_inode, (sector_t)(orig_blk_offset),
 428                                        "Unable to copy data block,"
 429                                        " data will be lost.");
 430                 *err = -EIO;
 431         }
 432         replaced_count = 0;
 433         goto unlock_pages;
 434 }
 435
 436 /**
 437  * mext_check_arguments - Check whether move extent can be done
 438  *
 439  * @orig_inode:         original inode
 440  * @donor_inode:        donor inode
 441  * @orig_start:         logical start offset in block for orig
 442  * @donor_start:        logical start offset in block for donor
 443  * @len:                the number of blocks to be moved
 444  *
 445  * Check the arguments of ext4_move_extents() whether the files can be
 446  * exchanged with each other.
 447  * Return 0 on success, or a negative error value on failure.
 448  */
 449 static int
 450 mext_check_arguments(struct inode *orig_inode,
 451                      struct inode *donor_inode, __u64 orig_start,
 452                      __u64 donor_start, __u64 *len)
 453 {
 454         __u64 orig_eof, donor_eof;
 455         unsigned int blkbits = orig_inode->i_blkbits;
 456         unsigned int blocksize = 1 << blkbits;
 457
 458         orig_eof = (i_size_read(orig_inode) + blocksize - 1) >> blkbits;
 459         donor_eof = (i_size_read(donor_inode) + blocksize - 1) >> blkbits;
 460
 461
 462         if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
 463                 ext4_debug("ext4 move extent: suid or sgid is set"
 464                            " to donor file [ino:orig %lu, donor %lu]\n",
 465                            orig_inode->i_ino, donor_inode->i_ino);
 466                 return -EINVAL;
 467         }
 468
 469         if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
 470                 return -EPERM;
 471
 472         /* Ext4 move extent does not support swapfile */
 473         if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
 474                 ext4_debug("ext4 move extent: The argument files should "
 475                         "not be swapfile [ino:orig %lu, donor %lu]\n",
 476                         orig_inode->i_ino, donor_inode->i_ino);
 477                 return -EBUSY;
 478         }
 479
 480         /* Ext4 move extent supports only extent based file */
 481         if (!(ext4_test_inode_flag(orig_inode, EXT4_INODE_EXTENTS))) {
 482                 ext4_debug("ext4 move extent: orig file is not extents "
 483                         "based file [ino:orig %lu]\n", orig_inode->i_ino);
 484                 return -EOPNOTSUPP;
 485         } else if (!(ext4_test_inode_flag(donor_inode, EXT4_INODE_EXTENTS))) {
 486                 ext4_debug("ext4 move extent: donor file is not extents "
 487                         "based file [ino:donor %lu]\n", donor_inode->i_ino);
 488                 return -EOPNOTSUPP;
 489         }
 490
 491         if ((!orig_inode->i_size) || (!donor_inode->i_size)) {
 492                 ext4_debug("ext4 move extent: File size is 0 byte\n");
 493                 return -EINVAL;
 494         }
 495
 496         /* Start offset should be same */
 497         if ((orig_start & ~(PAGE_MASK >> orig_inode->i_blkbits)) !=
 498             (donor_start & ~(PAGE_MASK >> orig_inode->i_blkbits))) {
 499                 ext4_debug("ext4 move extent: orig and donor's start "
 500                         "offset are not alligned [ino:orig %lu, donor %lu]\n",
 501                         orig_inode->i_ino, donor_inode->i_ino);
 502                 return -EINVAL;
 503         }
 504
 505         if ((orig_start >= EXT_MAX_BLOCKS) ||
 506             (donor_start >= EXT_MAX_BLOCKS) ||
 507             (*len > EXT_MAX_BLOCKS) ||
 508             (donor_start + *len >= EXT_MAX_BLOCKS) ||
 509             (orig_start + *len >= EXT_MAX_BLOCKS))  {
 510                 ext4_debug("ext4 move extent: Can't handle over [%u] blocks "
 511                         "[ino:orig %lu, donor %lu]\n", EXT_MAX_BLOCKS,
 512                         orig_inode->i_ino, donor_inode->i_ino);
 513                 return -EINVAL;
 514         }
 515         if (orig_eof < orig_start + *len - 1)
 516                 *len = orig_eof - orig_start;
 517         if (donor_eof < donor_start + *len - 1)
 518                 *len = donor_eof - donor_start;
 519         if (!*len) {
 520                 ext4_debug("ext4 move extent: len should not be 0 "
 521                         "[ino:orig %lu, donor %lu]\n", orig_inode->i_ino,
 522                         donor_inode->i_ino);
 523                 return -EINVAL;
 524         }
 525
 526         return 0;
 527 }
 528
 529 /**
 530  * ext4_move_extents - Exchange the specified range of a file
 531  *
 532  * @o_filp:             file structure of the original file
 533  * @d_filp:             file structure of the donor file
 534  * @orig_blk:           start offset in block for orig
 535  * @donor_blk:          start offset in block for donor
 536  * @len:                the number of blocks to be moved
 537  * @moved_len:          moved block length
 538  *
 539  * This function returns 0 and moved block length is set in moved_len
 540  * if succeed, otherwise returns error value.
 541  *
 542  */
 543 int
 544 ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 545                   __u64 donor_blk, __u64 len, __u64 *moved_len)
 546 {
 547         struct inode *orig_inode = file_inode(o_filp);
 548         struct inode *donor_inode = file_inode(d_filp);
 549         struct ext4_ext_path *path = NULL;
 550         int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
 551         ext4_lblk_t o_end, o_start = orig_blk;
 552         ext4_lblk_t d_start = donor_blk;
 553         int ret;
 554
 555         if (orig_inode->i_sb != donor_inode->i_sb) {
 556                 ext4_debug("ext4 move extent: The argument files "
 557                         "should be in same FS [ino:orig %lu, donor %lu]\n",
 558                         orig_inode->i_ino, donor_inode->i_ino);
 559                 return -EINVAL;
 560         }
 561
 562         /* orig and donor should be different inodes */
 563         if (orig_inode == donor_inode) {
 564                 ext4_debug("ext4 move extent: The argument files should not "
 565                         "be same inode [ino:orig %lu, donor %lu]\n",
 566                         orig_inode->i_ino, donor_inode->i_ino);
 567                 return -EINVAL;
 568         }
 569
 570         /* Regular file check */
 571         if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
 572                 ext4_debug("ext4 move extent: The argument files should be "
 573                         "regular file [ino:orig %lu, donor %lu]\n",
 574                         orig_inode->i_ino, donor_inode->i_ino);
 575                 return -EINVAL;
 576         }
 577         /* TODO: This is non obvious task to swap blocks for inodes with full
 578            jornaling enabled */
 579         if (ext4_should_journal_data(orig_inode) ||
 580             ext4_should_journal_data(donor_inode)) {
 581                 return -EINVAL;
 582         }
 583         /* Protect orig and donor inodes against a truncate */
 584         lock_two_nondirectories(orig_inode, donor_inode);
 585
 586         /* Wait for all existing dio workers */
 587         ext4_inode_block_unlocked_dio(orig_inode);
 588         ext4_inode_block_unlocked_dio(donor_inode);
 589         inode_dio_wait(orig_inode);
 590         inode_dio_wait(donor_inode);
 591
 592         /* Protect extent tree against block allocations via delalloc */
 593         ext4_double_down_write_data_sem(orig_inode, donor_inode);
 594         /* Check the filesystem environment whether move_extent can be done */
 595         ret = mext_check_arguments(orig_inode, donor_inode, orig_blk,
 596                                     donor_blk, &len);
 597         if (ret)
 598                 goto out;
 599         o_end = o_start + len;
 600
 601         while (o_start < o_end) {
 602                 struct ext4_extent *ex;
 603                 ext4_lblk_t cur_blk, next_blk;
 604                 pgoff_t orig_page_index, donor_page_index;
 605                 int offset_in_page;
 606                 int unwritten, cur_len;
 607
 608                 ret = get_ext_path(orig_inode, o_start, &path);
 609                 if (ret)
 610                         goto out;
 611                 ex = path[path->p_depth].p_ext;
 612                 next_blk = ext4_ext_next_allocated_block(path);
 613                 cur_blk = le32_to_cpu(ex->ee_block);
 614                 cur_len = ext4_ext_get_actual_len(ex);
 615                 /* Check hole before the start pos */
 616                 if (cur_blk + cur_len - 1 < o_start) {
 617                         if (next_blk == EXT_MAX_BLOCKS) {
 618                                 o_start = o_end;
 619                                 ret = -ENODATA;
 620                                 goto out;
 621                         }
 622                         d_start += next_blk - o_start;
 623                         o_start = next_blk;
 624                         continue;
 625                 /* Check hole after the start pos */
 626                 } else if (cur_blk > o_start) {
 627                         /* Skip hole */
 628                         d_start += cur_blk - o_start;
 629                         o_start = cur_blk;
 630                         /* Extent inside requested range ?*/
 631                         if (cur_blk >= o_end)
 632                                 goto out;
 633                 } else { /* in_range(o_start, o_blk, o_len) */
 634                         cur_len += cur_blk - o_start;
 635                 }
 636                 unwritten = ext4_ext_is_unwritten(ex);
 637                 if (o_end - o_start < cur_len)
 638                         cur_len = o_end - o_start;
 639
 640                 orig_page_index = o_start >> (PAGE_CACHE_SHIFT -
 641                                                orig_inode->i_blkbits);
 642                 donor_page_index = d_start >> (PAGE_CACHE_SHIFT -
 643                                                donor_inode->i_blkbits);
 644                 offset_in_page = o_start % blocks_per_page;
 645                 if (cur_len > blocks_per_page- offset_in_page)
 646                         cur_len = blocks_per_page - offset_in_page;
 647                 /*
 648                  * Up semaphore to avoid following problems:
 649                  * a. transaction deadlock among ext4_journal_start,
 650                  *    ->write_begin via pagefault, and jbd2_journal_commit
 651                  * b. racing with ->readpage, ->write_begin, and ext4_get_block
 652                  *    in move_extent_per_page
 653                  */
 654                 ext4_double_up_write_data_sem(orig_inode, donor_inode);
 655                 /* Swap original branches with new branches */
 656                 move_extent_per_page(o_filp, donor_inode,
 657                                      orig_page_index, donor_page_index,
 658                                      offset_in_page, cur_len,
 659                                      unwritten, &ret);
 660                 ext4_double_down_write_data_sem(orig_inode, donor_inode);
 661                 if (ret < 0)
 662                         break;
 663                 o_start += cur_len;
 664                 d_start += cur_len;
 665         }
 666         *moved_len = o_start - orig_blk;
 667         if (*moved_len > len)
 668                 *moved_len = len;
 669
 670 out:
 671         if (*moved_len) {
 672                 ext4_discard_preallocations(orig_inode);
 673                 ext4_discard_preallocations(donor_inode);
 674         }
 675
 676         ext4_ext_drop_refs(path);
 677         kfree(path);
 678         ext4_double_up_write_data_sem(orig_inode, donor_inode);
 679         ext4_inode_resume_unlocked_dio(orig_inode);
 680         ext4_inode_resume_unlocked_dio(donor_inode);
 681         unlock_two_nondirectories(orig_inode, donor_inode);
 682
 683         return ret;
 684 }