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Linux/fs/ext4/move_extent.c

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  1 // SPDX-License-Identifier: LGPL-2.1
  2 /*
  3  * Copyright (c) 2008,2009 NEC Software Tohoku, Ltd.
  4  * Written by Takashi Sato <t-sato@yk.jp.nec.com>
  5  *            Akira Fujita <a-fujita@rs.jp.nec.com>
  6  */
  7 
  8 #include <linux/fs.h>
  9 #include <linux/quotaops.h>
 10 #include <linux/slab.h>
 11 #include "ext4_jbd2.h"
 12 #include "ext4.h"
 13 #include "ext4_extents.h"
 14 
 15 /**
 16  * get_ext_path - Find an extent path for designated logical block number.
 17  *
 18  * @inode:      an inode which is searched
 19  * @lblock:     logical block number to find an extent path
 20  * @path:       pointer to an extent path pointer (for output)
 21  *
 22  * ext4_find_extent wrapper. Return 0 on success, or a negative error value
 23  * on failure.
 24  */
 25 static inline int
 26 get_ext_path(struct inode *inode, ext4_lblk_t lblock,
 27                 struct ext4_ext_path **ppath)
 28 {
 29         struct ext4_ext_path *path;
 30 
 31         path = ext4_find_extent(inode, lblock, ppath, EXT4_EX_NOCACHE);
 32         if (IS_ERR(path))
 33                 return PTR_ERR(path);
 34         if (path[ext_depth(inode)].p_ext == NULL) {
 35                 ext4_ext_drop_refs(path);
 36                 kfree(path);
 37                 *ppath = NULL;
 38                 return -ENODATA;
 39         }
 40         *ppath = path;
 41         return 0;
 42 }
 43 
 44 /**
 45  * ext4_double_down_write_data_sem - Acquire two inodes' write lock
 46  *                                   of i_data_sem
 47  *
 48  * Acquire write lock of i_data_sem of the two inodes
 49  */
 50 void
 51 ext4_double_down_write_data_sem(struct inode *first, struct inode *second)
 52 {
 53         if (first < second) {
 54                 down_write(&EXT4_I(first)->i_data_sem);
 55                 down_write_nested(&EXT4_I(second)->i_data_sem, I_DATA_SEM_OTHER);
 56         } else {
 57                 down_write(&EXT4_I(second)->i_data_sem);
 58                 down_write_nested(&EXT4_I(first)->i_data_sem, I_DATA_SEM_OTHER);
 59 
 60         }
 61 }
 62 
 63 /**
 64  * ext4_double_up_write_data_sem - Release two inodes' write lock of i_data_sem
 65  *
 66  * @orig_inode:         original inode structure to be released its lock first
 67  * @donor_inode:        donor inode structure to be released its lock second
 68  * Release write lock of i_data_sem of two inodes (orig and donor).
 69  */
 70 void
 71 ext4_double_up_write_data_sem(struct inode *orig_inode,
 72                               struct inode *donor_inode)
 73 {
 74         up_write(&EXT4_I(orig_inode)->i_data_sem);
 75         up_write(&EXT4_I(donor_inode)->i_data_sem);
 76 }
 77 
 78 /**
 79  * mext_check_coverage - Check that all extents in range has the same type
 80  *
 81  * @inode:              inode in question
 82  * @from:               block offset of inode
 83  * @count:              block count to be checked
 84  * @unwritten:          extents expected to be unwritten
 85  * @err:                pointer to save error value
 86  *
 87  * Return 1 if all extents in range has expected type, and zero otherwise.
 88  */
 89 static int
 90 mext_check_coverage(struct inode *inode, ext4_lblk_t from, ext4_lblk_t count,
 91                     int unwritten, int *err)
 92 {
 93         struct ext4_ext_path *path = NULL;
 94         struct ext4_extent *ext;
 95         int ret = 0;
 96         ext4_lblk_t last = from + count;
 97         while (from < last) {
 98                 *err = get_ext_path(inode, from, &path);
 99                 if (*err)
100                         goto out;
101                 ext = path[ext_depth(inode)].p_ext;
102                 if (unwritten != ext4_ext_is_unwritten(ext))
103                         goto out;
104                 from += ext4_ext_get_actual_len(ext);
105                 ext4_ext_drop_refs(path);
106         }
107         ret = 1;
108 out:
109         ext4_ext_drop_refs(path);
110         kfree(path);
111         return ret;
112 }
113 
114 /**
115  * mext_page_double_lock - Grab and lock pages on both @inode1 and @inode2
116  *
117  * @inode1:     the inode structure
118  * @inode2:     the inode structure
119  * @index1:     page index
120  * @index2:     page index
121  * @page:       result page vector
122  *
123  * Grab two locked pages for inode's by inode order
124  */
125 static int
126 mext_page_double_lock(struct inode *inode1, struct inode *inode2,
127                       pgoff_t index1, pgoff_t index2, struct page *page[2])
128 {
129         struct address_space *mapping[2];
130         unsigned fl = AOP_FLAG_NOFS;
131 
132         BUG_ON(!inode1 || !inode2);
133         if (inode1 < inode2) {
134                 mapping[0] = inode1->i_mapping;
135                 mapping[1] = inode2->i_mapping;
136         } else {
137                 swap(index1, index2);
138                 mapping[0] = inode2->i_mapping;
139                 mapping[1] = inode1->i_mapping;
140         }
141 
142         page[0] = grab_cache_page_write_begin(mapping[0], index1, fl);
143         if (!page[0])
144                 return -ENOMEM;
145 
146         page[1] = grab_cache_page_write_begin(mapping[1], index2, fl);
147         if (!page[1]) {
148                 unlock_page(page[0]);
149                 put_page(page[0]);
150                 return -ENOMEM;
151         }
152         /*
153          * grab_cache_page_write_begin() may not wait on page's writeback if
154          * BDI not demand that. But it is reasonable to be very conservative
155          * here and explicitly wait on page's writeback
156          */
157         wait_on_page_writeback(page[0]);
158         wait_on_page_writeback(page[1]);
159         if (inode1 > inode2)
160                 swap(page[0], page[1]);
161 
162         return 0;
163 }
164 
165 /* Force page buffers uptodate w/o dropping page's lock */
166 static int
167 mext_page_mkuptodate(struct page *page, unsigned from, unsigned to)
168 {
169         struct inode *inode = page->mapping->host;
170         sector_t block;
171         struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
172         unsigned int blocksize, block_start, block_end;
173         int i, err,  nr = 0, partial = 0;
174         BUG_ON(!PageLocked(page));
175         BUG_ON(PageWriteback(page));
176 
177         if (PageUptodate(page))
178                 return 0;
179 
180         blocksize = i_blocksize(inode);
181         if (!page_has_buffers(page))
182                 create_empty_buffers(page, blocksize, 0);
183 
184         head = page_buffers(page);
185         block = (sector_t)page->index << (PAGE_SHIFT - inode->i_blkbits);
186         for (bh = head, block_start = 0; bh != head || !block_start;
187              block++, block_start = block_end, bh = bh->b_this_page) {
188                 block_end = block_start + blocksize;
189                 if (block_end <= from || block_start >= to) {
190                         if (!buffer_uptodate(bh))
191                                 partial = 1;
192                         continue;
193                 }
194                 if (buffer_uptodate(bh))
195                         continue;
196                 if (!buffer_mapped(bh)) {
197                         err = ext4_get_block(inode, block, bh, 0);
198                         if (err) {
199                                 SetPageError(page);
200                                 return err;
201                         }
202                         if (!buffer_mapped(bh)) {
203                                 zero_user(page, block_start, blocksize);
204                                 set_buffer_uptodate(bh);
205                                 continue;
206                         }
207                 }
208                 BUG_ON(nr >= MAX_BUF_PER_PAGE);
209                 arr[nr++] = bh;
210         }
211         /* No io required */
212         if (!nr)
213                 goto out;
214 
215         for (i = 0; i < nr; i++) {
216                 bh = arr[i];
217                 if (!bh_uptodate_or_lock(bh)) {
218                         err = bh_submit_read(bh);
219                         if (err)
220                                 return err;
221                 }
222         }
223 out:
224         if (!partial)
225                 SetPageUptodate(page);
226         return 0;
227 }
228 
229 /**
230  * move_extent_per_page - Move extent data per page
231  *
232  * @o_filp:                     file structure of original file
233  * @donor_inode:                donor inode
234  * @orig_page_offset:           page index on original file
235  * @donor_page_offset:          page index on donor file
236  * @data_offset_in_page:        block index where data swapping starts
237  * @block_len_in_page:          the number of blocks to be swapped
238  * @unwritten:                  orig extent is unwritten or not
239  * @err:                        pointer to save return value
240  *
241  * Save the data in original inode blocks and replace original inode extents
242  * with donor inode extents by calling ext4_swap_extents().
243  * Finally, write out the saved data in new original inode blocks. Return
244  * replaced block count.
245  */
246 static int
247 move_extent_per_page(struct file *o_filp, struct inode *donor_inode,
248                      pgoff_t orig_page_offset, pgoff_t donor_page_offset,
249                      int data_offset_in_page,
250                      int block_len_in_page, int unwritten, int *err)
251 {
252         struct inode *orig_inode = file_inode(o_filp);
253         struct page *pagep[2] = {NULL, NULL};
254         handle_t *handle;
255         ext4_lblk_t orig_blk_offset, donor_blk_offset;
256         unsigned long blocksize = orig_inode->i_sb->s_blocksize;
257         unsigned int tmp_data_size, data_size, replaced_size;
258         int i, err2, jblocks, retries = 0;
259         int replaced_count = 0;
260         int from = data_offset_in_page << orig_inode->i_blkbits;
261         int blocks_per_page = PAGE_SIZE >> orig_inode->i_blkbits;
262         struct super_block *sb = orig_inode->i_sb;
263         struct buffer_head *bh = NULL;
264 
265         /*
266          * It needs twice the amount of ordinary journal buffers because
267          * inode and donor_inode may change each different metadata blocks.
268          */
269 again:
270         *err = 0;
271         jblocks = ext4_writepage_trans_blocks(orig_inode) * 2;
272         handle = ext4_journal_start(orig_inode, EXT4_HT_MOVE_EXTENTS, jblocks);
273         if (IS_ERR(handle)) {
274                 *err = PTR_ERR(handle);
275                 return 0;
276         }
277 
278         orig_blk_offset = orig_page_offset * blocks_per_page +
279                 data_offset_in_page;
280 
281         donor_blk_offset = donor_page_offset * blocks_per_page +
282                 data_offset_in_page;
283 
284         /* Calculate data_size */
285         if ((orig_blk_offset + block_len_in_page - 1) ==
286             ((orig_inode->i_size - 1) >> orig_inode->i_blkbits)) {
287                 /* Replace the last block */
288                 tmp_data_size = orig_inode->i_size & (blocksize - 1);
289                 /*
290                  * If data_size equal zero, it shows data_size is multiples of
291                  * blocksize. So we set appropriate value.
292                  */
293                 if (tmp_data_size == 0)
294                         tmp_data_size = blocksize;
295 
296                 data_size = tmp_data_size +
297                         ((block_len_in_page - 1) << orig_inode->i_blkbits);
298         } else
299                 data_size = block_len_in_page << orig_inode->i_blkbits;
300 
301         replaced_size = data_size;
302 
303         *err = mext_page_double_lock(orig_inode, donor_inode, orig_page_offset,
304                                      donor_page_offset, pagep);
305         if (unlikely(*err < 0))
306                 goto stop_journal;
307         /*
308          * If orig extent was unwritten it can become initialized
309          * at any time after i_data_sem was dropped, in order to
310          * serialize with delalloc we have recheck extent while we
311          * hold page's lock, if it is still the case data copy is not
312          * necessary, just swap data blocks between orig and donor.
313          */
314         if (unwritten) {
315                 ext4_double_down_write_data_sem(orig_inode, donor_inode);
316                 /* If any of extents in range became initialized we have to
317                  * fallback to data copying */
318                 unwritten = mext_check_coverage(orig_inode, orig_blk_offset,
319                                                 block_len_in_page, 1, err);
320                 if (*err)
321                         goto drop_data_sem;
322 
323                 unwritten &= mext_check_coverage(donor_inode, donor_blk_offset,
324                                                  block_len_in_page, 1, err);
325                 if (*err)
326                         goto drop_data_sem;
327 
328                 if (!unwritten) {
329                         ext4_double_up_write_data_sem(orig_inode, donor_inode);
330                         goto data_copy;
331                 }
332                 if ((page_has_private(pagep[0]) &&
333                      !try_to_release_page(pagep[0], 0)) ||
334                     (page_has_private(pagep[1]) &&
335                      !try_to_release_page(pagep[1], 0))) {
336                         *err = -EBUSY;
337                         goto drop_data_sem;
338                 }
339                 replaced_count = ext4_swap_extents(handle, orig_inode,
340                                                    donor_inode, orig_blk_offset,
341                                                    donor_blk_offset,
342                                                    block_len_in_page, 1, err);
343         drop_data_sem:
344                 ext4_double_up_write_data_sem(orig_inode, donor_inode);
345                 goto unlock_pages;
346         }
347 data_copy:
348         *err = mext_page_mkuptodate(pagep[0], from, from + replaced_size);
349         if (*err)
350                 goto unlock_pages;
351 
352         /* At this point all buffers in range are uptodate, old mapping layout
353          * is no longer required, try to drop it now. */
354         if ((page_has_private(pagep[0]) && !try_to_release_page(pagep[0], 0)) ||
355             (page_has_private(pagep[1]) && !try_to_release_page(pagep[1], 0))) {
356                 *err = -EBUSY;
357                 goto unlock_pages;
358         }
359         ext4_double_down_write_data_sem(orig_inode, donor_inode);
360         replaced_count = ext4_swap_extents(handle, orig_inode, donor_inode,
361                                                orig_blk_offset, donor_blk_offset,
362                                            block_len_in_page, 1, err);
363         ext4_double_up_write_data_sem(orig_inode, donor_inode);
364         if (*err) {
365                 if (replaced_count) {
366                         block_len_in_page = replaced_count;
367                         replaced_size =
368                                 block_len_in_page << orig_inode->i_blkbits;
369                 } else
370                         goto unlock_pages;
371         }
372         /* Perform all necessary steps similar write_begin()/write_end()
373          * but keeping in mind that i_size will not change */
374         if (!page_has_buffers(pagep[0]))
375                 create_empty_buffers(pagep[0], 1 << orig_inode->i_blkbits, 0);
376         bh = page_buffers(pagep[0]);
377         for (i = 0; i < data_offset_in_page; i++)
378                 bh = bh->b_this_page;
379         for (i = 0; i < block_len_in_page; i++) {
380                 *err = ext4_get_block(orig_inode, orig_blk_offset + i, bh, 0);
381                 if (*err < 0)
382                         break;
383                 bh = bh->b_this_page;
384         }
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_inode_add_write(handle, orig_inode,
394                         (loff_t)orig_page_offset << PAGE_SHIFT, replaced_size);
395 
396 unlock_pages:
397         unlock_page(pagep[0]);
398         put_page(pagep[0]);
399         unlock_page(pagep[1]);
400         put_page(pagep[1]);
401 stop_journal:
402         ext4_journal_stop(handle);
403         if (*err == -ENOSPC &&
404             ext4_should_retry_alloc(sb, &retries))
405                 goto again;
406         /* Buffer was busy because probably is pinned to journal transaction,
407          * force transaction commit may help to free it. */
408         if (*err == -EBUSY && retries++ < 4 && EXT4_SB(sb)->s_journal &&
409             jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal))
410                 goto again;
411         return replaced_count;
412 
413 repair_branches:
414         /*
415          * This should never ever happen!
416          * Extents are swapped already, but we are not able to copy data.
417          * Try to swap extents to it's original places
418          */
419         ext4_double_down_write_data_sem(orig_inode, donor_inode);
420         replaced_count = ext4_swap_extents(handle, donor_inode, orig_inode,
421                                                orig_blk_offset, donor_blk_offset,
422                                            block_len_in_page, 0, &err2);
423         ext4_double_up_write_data_sem(orig_inode, donor_inode);
424         if (replaced_count != block_len_in_page) {
425                 EXT4_ERROR_INODE_BLOCK(orig_inode, (sector_t)(orig_blk_offset),
426                                        "Unable to copy data block,"
427                                        " data will be lost.");
428                 *err = -EIO;
429         }
430         replaced_count = 0;
431         goto unlock_pages;
432 }
433 
434 /**
435  * mext_check_arguments - Check whether move extent can be done
436  *
437  * @orig_inode:         original inode
438  * @donor_inode:        donor inode
439  * @orig_start:         logical start offset in block for orig
440  * @donor_start:        logical start offset in block for donor
441  * @len:                the number of blocks to be moved
442  *
443  * Check the arguments of ext4_move_extents() whether the files can be
444  * exchanged with each other.
445  * Return 0 on success, or a negative error value on failure.
446  */
447 static int
448 mext_check_arguments(struct inode *orig_inode,
449                      struct inode *donor_inode, __u64 orig_start,
450                      __u64 donor_start, __u64 *len)
451 {
452         __u64 orig_eof, donor_eof;
453         unsigned int blkbits = orig_inode->i_blkbits;
454         unsigned int blocksize = 1 << blkbits;
455 
456         orig_eof = (i_size_read(orig_inode) + blocksize - 1) >> blkbits;
457         donor_eof = (i_size_read(donor_inode) + blocksize - 1) >> blkbits;
458 
459 
460         if (donor_inode->i_mode & (S_ISUID|S_ISGID)) {
461                 ext4_debug("ext4 move extent: suid or sgid is set"
462                            " to donor file [ino:orig %lu, donor %lu]\n",
463                            orig_inode->i_ino, donor_inode->i_ino);
464                 return -EINVAL;
465         }
466 
467         if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
468                 return -EPERM;
469 
470         /* Ext4 move extent does not support swapfile */
471         if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
472                 ext4_debug("ext4 move extent: The argument files should "
473                         "not be swapfile [ino:orig %lu, donor %lu]\n",
474                         orig_inode->i_ino, donor_inode->i_ino);
475                 return -EBUSY;
476         }
477 
478         if (ext4_is_quota_file(orig_inode) && ext4_is_quota_file(donor_inode)) {
479                 ext4_debug("ext4 move extent: The argument files should "
480                         "not be quota files [ino:orig %lu, donor %lu]\n",
481                         orig_inode->i_ino, donor_inode->i_ino);
482                 return -EBUSY;
483         }
484 
485         /* Ext4 move extent supports only extent based file */
486         if (!(ext4_test_inode_flag(orig_inode, EXT4_INODE_EXTENTS))) {
487                 ext4_debug("ext4 move extent: orig file is not extents "
488                         "based file [ino:orig %lu]\n", orig_inode->i_ino);
489                 return -EOPNOTSUPP;
490         } else if (!(ext4_test_inode_flag(donor_inode, EXT4_INODE_EXTENTS))) {
491                 ext4_debug("ext4 move extent: donor file is not extents "
492                         "based file [ino:donor %lu]\n", donor_inode->i_ino);
493                 return -EOPNOTSUPP;
494         }
495 
496         if ((!orig_inode->i_size) || (!donor_inode->i_size)) {
497                 ext4_debug("ext4 move extent: File size is 0 byte\n");
498                 return -EINVAL;
499         }
500 
501         /* Start offset should be same */
502         if ((orig_start & ~(PAGE_MASK >> orig_inode->i_blkbits)) !=
503             (donor_start & ~(PAGE_MASK >> orig_inode->i_blkbits))) {
504                 ext4_debug("ext4 move extent: orig and donor's start "
505                         "offsets are not aligned [ino:orig %lu, donor %lu]\n",
506                         orig_inode->i_ino, donor_inode->i_ino);
507                 return -EINVAL;
508         }
509 
510         if ((orig_start >= EXT_MAX_BLOCKS) ||
511             (donor_start >= EXT_MAX_BLOCKS) ||
512             (*len > EXT_MAX_BLOCKS) ||
513             (donor_start + *len >= EXT_MAX_BLOCKS) ||
514             (orig_start + *len >= EXT_MAX_BLOCKS))  {
515                 ext4_debug("ext4 move extent: Can't handle over [%u] blocks "
516                         "[ino:orig %lu, donor %lu]\n", EXT_MAX_BLOCKS,
517                         orig_inode->i_ino, donor_inode->i_ino);
518                 return -EINVAL;
519         }
520         if (orig_eof <= orig_start)
521                 *len = 0;
522         else if (orig_eof < orig_start + *len - 1)
523                 *len = orig_eof - orig_start;
524         if (donor_eof <= donor_start)
525                 *len = 0;
526         else if (donor_eof < donor_start + *len - 1)
527                 *len = donor_eof - donor_start;
528         if (!*len) {
529                 ext4_debug("ext4 move extent: len should not be 0 "
530                         "[ino:orig %lu, donor %lu]\n", orig_inode->i_ino,
531                         donor_inode->i_ino);
532                 return -EINVAL;
533         }
534 
535         return 0;
536 }
537 
538 /**
539  * ext4_move_extents - Exchange the specified range of a file
540  *
541  * @o_filp:             file structure of the original file
542  * @d_filp:             file structure of the donor file
543  * @orig_blk:           start offset in block for orig
544  * @donor_blk:          start offset in block for donor
545  * @len:                the number of blocks to be moved
546  * @moved_len:          moved block length
547  *
548  * This function returns 0 and moved block length is set in moved_len
549  * if succeed, otherwise returns error value.
550  *
551  */
552 int
553 ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
554                   __u64 donor_blk, __u64 len, __u64 *moved_len)
555 {
556         struct inode *orig_inode = file_inode(o_filp);
557         struct inode *donor_inode = file_inode(d_filp);
558         struct ext4_ext_path *path = NULL;
559         int blocks_per_page = PAGE_SIZE >> orig_inode->i_blkbits;
560         ext4_lblk_t o_end, o_start = orig_blk;
561         ext4_lblk_t d_start = donor_blk;
562         int ret;
563 
564         if (orig_inode->i_sb != donor_inode->i_sb) {
565                 ext4_debug("ext4 move extent: The argument files "
566                         "should be in same FS [ino:orig %lu, donor %lu]\n",
567                         orig_inode->i_ino, donor_inode->i_ino);
568                 return -EINVAL;
569         }
570 
571         /* orig and donor should be different inodes */
572         if (orig_inode == donor_inode) {
573                 ext4_debug("ext4 move extent: The argument files should not "
574                         "be same inode [ino:orig %lu, donor %lu]\n",
575                         orig_inode->i_ino, donor_inode->i_ino);
576                 return -EINVAL;
577         }
578 
579         /* Regular file check */
580         if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
581                 ext4_debug("ext4 move extent: The argument files should be "
582                         "regular file [ino:orig %lu, donor %lu]\n",
583                         orig_inode->i_ino, donor_inode->i_ino);
584                 return -EINVAL;
585         }
586 
587         /* TODO: it's not obvious how to swap blocks for inodes with full
588            journaling enabled */
589         if (ext4_should_journal_data(orig_inode) ||
590             ext4_should_journal_data(donor_inode)) {
591                 ext4_msg(orig_inode->i_sb, KERN_ERR,
592                          "Online defrag not supported with data journaling");
593                 return -EOPNOTSUPP;
594         }
595 
596         if (IS_ENCRYPTED(orig_inode) || IS_ENCRYPTED(donor_inode)) {
597                 ext4_msg(orig_inode->i_sb, KERN_ERR,
598                          "Online defrag not supported for encrypted files");
599                 return -EOPNOTSUPP;
600         }
601 
602         /* Protect orig and donor inodes against a truncate */
603         lock_two_nondirectories(orig_inode, donor_inode);
604 
605         /* Wait for all existing dio workers */
606         inode_dio_wait(orig_inode);
607         inode_dio_wait(donor_inode);
608 
609         /* Protect extent tree against block allocations via delalloc */
610         ext4_double_down_write_data_sem(orig_inode, donor_inode);
611         /* Check the filesystem environment whether move_extent can be done */
612         ret = mext_check_arguments(orig_inode, donor_inode, orig_blk,
613                                     donor_blk, &len);
614         if (ret)
615                 goto out;
616         o_end = o_start + len;
617 
618         while (o_start < o_end) {
619                 struct ext4_extent *ex;
620                 ext4_lblk_t cur_blk, next_blk;
621                 pgoff_t orig_page_index, donor_page_index;
622                 int offset_in_page;
623                 int unwritten, cur_len;
624 
625                 ret = get_ext_path(orig_inode, o_start, &path);
626                 if (ret)
627                         goto out;
628                 ex = path[path->p_depth].p_ext;
629                 next_blk = ext4_ext_next_allocated_block(path);
630                 cur_blk = le32_to_cpu(ex->ee_block);
631                 cur_len = ext4_ext_get_actual_len(ex);
632                 /* Check hole before the start pos */
633                 if (cur_blk + cur_len - 1 < o_start) {
634                         if (next_blk == EXT_MAX_BLOCKS) {
635                                 o_start = o_end;
636                                 ret = -ENODATA;
637                                 goto out;
638                         }
639                         d_start += next_blk - o_start;
640                         o_start = next_blk;
641                         continue;
642                 /* Check hole after the start pos */
643                 } else if (cur_blk > o_start) {
644                         /* Skip hole */
645                         d_start += cur_blk - o_start;
646                         o_start = cur_blk;
647                         /* Extent inside requested range ?*/
648                         if (cur_blk >= o_end)
649                                 goto out;
650                 } else { /* in_range(o_start, o_blk, o_len) */
651                         cur_len += cur_blk - o_start;
652                 }
653                 unwritten = ext4_ext_is_unwritten(ex);
654                 if (o_end - o_start < cur_len)
655                         cur_len = o_end - o_start;
656 
657                 orig_page_index = o_start >> (PAGE_SHIFT -
658                                                orig_inode->i_blkbits);
659                 donor_page_index = d_start >> (PAGE_SHIFT -
660                                                donor_inode->i_blkbits);
661                 offset_in_page = o_start % blocks_per_page;
662                 if (cur_len > blocks_per_page- offset_in_page)
663                         cur_len = blocks_per_page - offset_in_page;
664                 /*
665                  * Up semaphore to avoid following problems:
666                  * a. transaction deadlock among ext4_journal_start,
667                  *    ->write_begin via pagefault, and jbd2_journal_commit
668                  * b. racing with ->readpage, ->write_begin, and ext4_get_block
669                  *    in move_extent_per_page
670                  */
671                 ext4_double_up_write_data_sem(orig_inode, donor_inode);
672                 /* Swap original branches with new branches */
673                 move_extent_per_page(o_filp, donor_inode,
674                                      orig_page_index, donor_page_index,
675                                      offset_in_page, cur_len,
676                                      unwritten, &ret);
677                 ext4_double_down_write_data_sem(orig_inode, donor_inode);
678                 if (ret < 0)
679                         break;
680                 o_start += cur_len;
681                 d_start += cur_len;
682         }
683         *moved_len = o_start - orig_blk;
684         if (*moved_len > len)
685                 *moved_len = len;
686 
687 out:
688         if (*moved_len) {
689                 ext4_discard_preallocations(orig_inode);
690                 ext4_discard_preallocations(donor_inode);
691         }
692 
693         ext4_ext_drop_refs(path);
694         kfree(path);
695         ext4_double_up_write_data_sem(orig_inode, donor_inode);
696         unlock_two_nondirectories(orig_inode, donor_inode);
697 
698         return ret;
699 }
700 

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