2 * linux/fs/ext4/balloc.c
4 * Copyright (C) 1992, 1993, 1994, 1995
5 * Remy Card (card@masi.ibp.fr)
6 * Laboratoire MASI - Institut Blaise Pascal
7 * Universite Pierre et Marie Curie (Paris VI)
9 * Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
10 * Big-endian to little-endian byte-swapping/bitmaps by
11 * David S. Miller (davem@caip.rutgers.edu), 1995
14 #include <linux/time.h>
15 #include <linux/capability.h>
17 #include <linux/jbd2.h>
18 #include <linux/quotaops.h>
19 #include <linux/buffer_head.h>
21 #include "ext4_jbd2.h"
24 #include <trace/events/ext4.h>
27 * balloc.c contains the blocks allocation and deallocation routines
31 * Calculate the block group number and offset into the block/cluster
32 * allocation bitmap, given a block number
34 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
35 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
37 struct ext4_super_block *es = EXT4_SB(sb)->s_es;
40 blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
41 offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >>
42 EXT4_SB(sb)->s_cluster_bits;
50 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
51 ext4_group_t block_group)
53 ext4_group_t actual_group;
54 ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
55 if (actual_group == block_group)
60 /* Return the number of clusters used for file system metadata; this
61 * represents the overhead needed by the file system.
63 unsigned ext4_num_overhead_clusters(struct super_block *sb,
64 ext4_group_t block_group,
65 struct ext4_group_desc *gdp)
67 unsigned num_clusters;
68 int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
69 ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
70 ext4_fsblk_t itbl_blk;
71 struct ext4_sb_info *sbi = EXT4_SB(sb);
73 /* This is the number of clusters used by the superblock,
74 * block group descriptors, and reserved block group
75 * descriptor blocks */
76 num_clusters = ext4_num_base_meta_clusters(sb, block_group);
79 * For the allocation bitmaps and inode table, we first need
80 * to check to see if the block is in the block group. If it
81 * is, then check to see if the cluster is already accounted
82 * for in the clusters used for the base metadata cluster, or
83 * if we can increment the base metadata cluster to include
84 * that block. Otherwise, we will have to track the cluster
85 * used for the allocation bitmap or inode table explicitly.
86 * Normally all of these blocks are contiguous, so the special
87 * case handling shouldn't be necessary except for *very*
88 * unusual file system layouts.
90 if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
91 block_cluster = EXT4_B2C(sbi,
92 ext4_block_bitmap(sb, gdp) - start);
93 if (block_cluster < num_clusters)
95 else if (block_cluster == num_clusters) {
101 if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
102 inode_cluster = EXT4_B2C(sbi,
103 ext4_inode_bitmap(sb, gdp) - start);
104 if (inode_cluster < num_clusters)
106 else if (inode_cluster == num_clusters) {
112 itbl_blk = ext4_inode_table(sb, gdp);
113 for (i = 0; i < sbi->s_itb_per_group; i++) {
114 if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
115 c = EXT4_B2C(sbi, itbl_blk + i - start);
116 if ((c < num_clusters) || (c == inode_cluster) ||
117 (c == block_cluster) || (c == itbl_cluster))
119 if (c == num_clusters) {
128 if (block_cluster != -1)
130 if (inode_cluster != -1)
136 static unsigned int num_clusters_in_group(struct super_block *sb,
137 ext4_group_t block_group)
141 if (block_group == ext4_get_groups_count(sb) - 1) {
143 * Even though mke2fs always initializes the first and
144 * last group, just in case some other tool was used,
145 * we need to make sure we calculate the right free
148 blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -
149 ext4_group_first_block_no(sb, block_group);
151 blocks = EXT4_BLOCKS_PER_GROUP(sb);
152 return EXT4_NUM_B2C(EXT4_SB(sb), blocks);
155 /* Initializes an uninitialized block bitmap */
156 void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
157 ext4_group_t block_group,
158 struct ext4_group_desc *gdp)
160 unsigned int bit, bit_max;
161 struct ext4_sb_info *sbi = EXT4_SB(sb);
162 ext4_fsblk_t start, tmp;
165 J_ASSERT_BH(bh, buffer_locked(bh));
167 /* If checksum is bad mark all blocks used to prevent allocation
168 * essentially implementing a per-group read-only flag. */
169 if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
170 ext4_error(sb, "Checksum bad for group %u", block_group);
171 ext4_free_group_clusters_set(sb, gdp, 0);
172 ext4_free_inodes_set(sb, gdp, 0);
173 ext4_itable_unused_set(sb, gdp, 0);
174 memset(bh->b_data, 0xff, sb->s_blocksize);
177 memset(bh->b_data, 0, sb->s_blocksize);
179 bit_max = ext4_num_base_meta_clusters(sb, block_group);
180 for (bit = 0; bit < bit_max; bit++)
181 ext4_set_bit(bit, bh->b_data);
183 start = ext4_group_first_block_no(sb, block_group);
185 if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
188 /* Set bits for block and inode bitmaps, and inode table */
189 tmp = ext4_block_bitmap(sb, gdp);
190 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
191 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
193 tmp = ext4_inode_bitmap(sb, gdp);
194 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
195 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
197 tmp = ext4_inode_table(sb, gdp);
198 for (; tmp < ext4_inode_table(sb, gdp) +
199 sbi->s_itb_per_group; tmp++) {
200 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
201 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
205 * Also if the number of blocks within the group is less than
206 * the blocksize * 8 ( which is the size of bitmap ), set rest
207 * of the block bitmap to 1
209 ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
210 sb->s_blocksize * 8, bh->b_data);
213 /* Return the number of free blocks in a block group. It is used when
214 * the block bitmap is uninitialized, so we can't just count the bits
216 unsigned ext4_free_clusters_after_init(struct super_block *sb,
217 ext4_group_t block_group,
218 struct ext4_group_desc *gdp)
220 return num_clusters_in_group(sb, block_group) -
221 ext4_num_overhead_clusters(sb, block_group, gdp);
225 * The free blocks are managed by bitmaps. A file system contains several
226 * blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap
227 * block for inodes, N blocks for the inode table and data blocks.
229 * The file system contains group descriptors which are located after the
230 * super block. Each descriptor contains the number of the bitmap block and
231 * the free blocks count in the block. The descriptors are loaded in memory
232 * when a file system is mounted (see ext4_fill_super).
236 * ext4_get_group_desc() -- load group descriptor from disk
238 * @block_group: given block group
239 * @bh: pointer to the buffer head to store the block
242 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
243 ext4_group_t block_group,
244 struct buffer_head **bh)
246 unsigned int group_desc;
248 ext4_group_t ngroups = ext4_get_groups_count(sb);
249 struct ext4_group_desc *desc;
250 struct ext4_sb_info *sbi = EXT4_SB(sb);
252 if (block_group >= ngroups) {
253 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
254 " groups_count = %u", block_group, ngroups);
259 group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
260 offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
261 if (!sbi->s_group_desc[group_desc]) {
262 ext4_error(sb, "Group descriptor not loaded - "
263 "block_group = %u, group_desc = %u, desc = %u",
264 block_group, group_desc, offset);
268 desc = (struct ext4_group_desc *)(
269 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
270 offset * EXT4_DESC_SIZE(sb));
272 *bh = sbi->s_group_desc[group_desc];
276 static int ext4_valid_block_bitmap(struct super_block *sb,
277 struct ext4_group_desc *desc,
278 unsigned int block_group,
279 struct buffer_head *bh)
281 struct ext4_sb_info *sbi = EXT4_SB(sb);
282 ext4_grpblk_t offset;
283 ext4_grpblk_t next_zero_bit;
284 ext4_grpblk_t max_bit = EXT4_CLUSTERS_PER_GROUP(sb);
285 ext4_fsblk_t bitmap_blk;
286 ext4_fsblk_t group_first_block;
288 if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
289 /* with FLEX_BG, the inode/block bitmaps and itable
290 * blocks may not be in the group at all
291 * so the bitmap validation will be skipped for those groups
292 * or it has to also read the block group where the bitmaps
293 * are located to verify they are set.
297 group_first_block = ext4_group_first_block_no(sb, block_group);
299 /* check whether block bitmap block number is set */
300 bitmap_blk = ext4_block_bitmap(sb, desc);
301 offset = bitmap_blk - group_first_block;
302 if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
303 !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
304 /* bad block bitmap */
307 /* check whether the inode bitmap block number is set */
308 bitmap_blk = ext4_inode_bitmap(sb, desc);
309 offset = bitmap_blk - group_first_block;
310 if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
311 !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
312 /* bad block bitmap */
315 /* check whether the inode table block number is set */
316 bitmap_blk = ext4_inode_table(sb, desc);
317 offset = bitmap_blk - group_first_block;
318 if (offset < 0 || EXT4_B2C(sbi, offset) >= max_bit ||
319 EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= max_bit)
321 next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
322 EXT4_B2C(sbi, offset + EXT4_SB(sb)->s_itb_per_group),
323 EXT4_B2C(sbi, offset));
325 EXT4_B2C(sbi, offset + EXT4_SB(sb)->s_itb_per_group))
326 /* good bitmap for inode tables */
330 ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
331 block_group, bitmap_blk);
335 * ext4_read_block_bitmap()
337 * @block_group: given block group
339 * Read the bitmap for a given block_group,and validate the
340 * bits for block/inode/inode tables are set in the bitmaps
342 * Return buffer_head on success or NULL in case of failure.
345 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
347 struct ext4_group_desc *desc;
348 struct ext4_sb_info *sbi = EXT4_SB(sb);
349 struct buffer_head *bh = NULL;
350 ext4_fsblk_t bitmap_blk;
352 desc = ext4_get_group_desc(sb, block_group, NULL);
355 bitmap_blk = ext4_block_bitmap(sb, desc);
356 if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
357 (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
358 ext4_error(sb, "Invalid block bitmap block %llu in "
359 "block_group %u", bitmap_blk, block_group);
362 bh = sb_getblk(sb, bitmap_blk);
364 ext4_error(sb, "Cannot read block bitmap - "
365 "block_group = %u, block_bitmap = %llu",
366 block_group, bitmap_blk);
370 if (bitmap_uptodate(bh))
374 if (bitmap_uptodate(bh)) {
378 ext4_lock_group(sb, block_group);
379 if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
380 ext4_init_block_bitmap(sb, bh, block_group, desc);
381 set_bitmap_uptodate(bh);
382 set_buffer_uptodate(bh);
383 ext4_unlock_group(sb, block_group);
387 ext4_unlock_group(sb, block_group);
388 if (buffer_uptodate(bh)) {
390 * if not uninit if bh is uptodate,
391 * bitmap is also uptodate
393 set_bitmap_uptodate(bh);
398 * submit the buffer_head for read. We can
399 * safely mark the bitmap as uptodate now.
400 * We do it here so the bitmap uptodate bit
401 * get set with buffer lock held.
403 trace_ext4_read_block_bitmap_load(sb, block_group);
404 set_bitmap_uptodate(bh);
405 if (bh_submit_read(bh) < 0) {
407 ext4_error(sb, "Cannot read block bitmap - "
408 "block_group = %u, block_bitmap = %llu",
409 block_group, bitmap_blk);
412 ext4_valid_block_bitmap(sb, desc, block_group, bh);
414 * file system mounted not to panic on error,
415 * continue with corrupt bitmap
421 * ext4_has_free_clusters()
422 * @sbi: in-core super block structure.
423 * @nclusters: number of needed blocks
424 * @flags: flags from ext4_mb_new_blocks()
426 * Check if filesystem has nclusters free & available for allocation.
427 * On success return 1, return 0 on failure.
429 static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
430 s64 nclusters, unsigned int flags)
432 s64 free_clusters, dirty_clusters, root_clusters;
433 struct percpu_counter *fcc = &sbi->s_freeclusters_counter;
434 struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;
436 free_clusters = percpu_counter_read_positive(fcc);
437 dirty_clusters = percpu_counter_read_positive(dcc);
440 * r_blocks_count should always be multiple of the cluster ratio so
441 * we are safe to do a plane bit shift only.
443 root_clusters = ext4_r_blocks_count(sbi->s_es) >> sbi->s_cluster_bits;
445 if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
446 EXT4_FREECLUSTERS_WATERMARK) {
447 free_clusters = percpu_counter_sum_positive(fcc);
448 dirty_clusters = percpu_counter_sum_positive(dcc);
450 /* Check whether we have space after accounting for current
451 * dirty clusters & root reserved clusters.
453 if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters))
456 /* Hm, nope. Are (enough) root reserved clusters available? */
457 if (sbi->s_resuid == current_fsuid() ||
458 ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
459 capable(CAP_SYS_RESOURCE) ||
460 (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
462 if (free_clusters >= (nclusters + dirty_clusters))
469 int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
470 s64 nclusters, unsigned int flags)
472 if (ext4_has_free_clusters(sbi, nclusters, flags)) {
473 percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);
480 * ext4_should_retry_alloc()
482 * @retries number of attemps has been made
484 * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
485 * it is profitable to retry the operation, this function will wait
486 * for the current or committing transaction to complete, and then
489 * if the total number of retries exceed three times, return FALSE.
491 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
493 if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
495 !EXT4_SB(sb)->s_journal)
498 jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
500 return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
504 * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
506 * @handle: handle to this transaction
508 * @goal: given target block(filesystem wide)
509 * @count: pointer to total number of clusters needed
512 * Return 1st allocated block number on success, *count stores total account
513 * error stores in errp pointer
515 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
516 ext4_fsblk_t goal, unsigned int flags,
517 unsigned long *count, int *errp)
519 struct ext4_allocation_request ar;
522 memset(&ar, 0, sizeof(ar));
523 /* Fill with neighbour allocated blocks */
526 ar.len = count ? *count : 1;
529 ret = ext4_mb_new_blocks(handle, &ar, errp);
533 * Account for the allocated meta blocks. We will never
534 * fail EDQUOT for metdata, but we do account for it.
537 ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
538 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
539 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
540 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
541 dquot_alloc_block_nofail(inode,
542 EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));
548 * ext4_count_free_clusters() -- count filesystem free clusters
551 * Adds up the number of free clusters from each block group.
553 ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
555 ext4_fsblk_t desc_count;
556 struct ext4_group_desc *gdp;
558 ext4_group_t ngroups = ext4_get_groups_count(sb);
560 struct ext4_super_block *es;
561 ext4_fsblk_t bitmap_count;
563 struct buffer_head *bitmap_bh = NULL;
565 es = EXT4_SB(sb)->s_es;
570 for (i = 0; i < ngroups; i++) {
571 gdp = ext4_get_group_desc(sb, i, NULL);
574 desc_count += ext4_free_group_clusters(sb, gdp);
576 bitmap_bh = ext4_read_block_bitmap(sb, i);
577 if (bitmap_bh == NULL)
580 x = ext4_count_free(bitmap_bh->b_data,
581 EXT4_BLOCKS_PER_GROUP(sb) / 8);
582 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
583 i, ext4_free_group_clusters(sb, gdp), x);
587 printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
588 ", computed = %llu, %llu\n",
589 EXT4_NUM_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),
590 desc_count, bitmap_count);
594 for (i = 0; i < ngroups; i++) {
595 gdp = ext4_get_group_desc(sb, i, NULL);
598 desc_count += ext4_free_group_clusters(sb, gdp);
605 static inline int test_root(ext4_group_t a, int b)
614 static int ext4_group_sparse(ext4_group_t group)
620 return (test_root(group, 7) || test_root(group, 5) ||
621 test_root(group, 3));
625 * ext4_bg_has_super - number of blocks used by the superblock in group
626 * @sb: superblock for filesystem
627 * @group: group number to check
629 * Return the number of blocks used by the superblock (primary or backup)
630 * in this group. Currently this will be only 0 or 1.
632 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
634 if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
635 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
636 !ext4_group_sparse(group))
641 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
644 unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
645 ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
646 ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
648 if (group == first || group == first + 1 || group == last)
653 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
656 if (!ext4_bg_has_super(sb, group))
659 if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
660 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
662 return EXT4_SB(sb)->s_gdb_count;
666 * ext4_bg_num_gdb - number of blocks used by the group table in group
667 * @sb: superblock for filesystem
668 * @group: group number to check
670 * Return the number of blocks used by the group descriptor table
671 * (primary or backup) in this group. In the future there may be a
672 * different number of descriptor blocks in each group.
674 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
676 unsigned long first_meta_bg =
677 le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
678 unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
680 if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
681 metagroup < first_meta_bg)
682 return ext4_bg_num_gdb_nometa(sb, group);
684 return ext4_bg_num_gdb_meta(sb,group);
689 * This function returns the number of file system metadata clusters at
690 * the beginning of a block group, including the reserved gdt blocks.
692 unsigned ext4_num_base_meta_clusters(struct super_block *sb,
693 ext4_group_t block_group)
695 struct ext4_sb_info *sbi = EXT4_SB(sb);
698 /* Check for superblock and gdt backups in this group */
699 num = ext4_bg_has_super(sb, block_group);
701 if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
702 block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
703 sbi->s_desc_per_block) {
705 num += ext4_bg_num_gdb(sb, block_group);
706 num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
708 } else { /* For META_BG_BLOCK_GROUPS */
709 num += ext4_bg_num_gdb(sb, block_group);
711 return EXT4_NUM_B2C(sbi, num);
714 * ext4_inode_to_goal_block - return a hint for block allocation
715 * @inode: inode for block allocation
717 * Return the ideal location to start allocating blocks for a
718 * newly created inode.
720 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
722 struct ext4_inode_info *ei = EXT4_I(inode);
723 ext4_group_t block_group;
724 ext4_grpblk_t colour;
725 int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
726 ext4_fsblk_t bg_start;
727 ext4_fsblk_t last_block;
729 block_group = ei->i_block_group;
730 if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
732 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
733 * block groups per flexgroup, reserve the first block
734 * group for directories and special files. Regular
735 * files will start at the second block group. This
736 * tends to speed up directory access and improves
739 block_group &= ~(flex_size-1);
740 if (S_ISREG(inode->i_mode))
743 bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
744 last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
747 * If we are doing delayed allocation, we don't need take
748 * colour into account.
750 if (test_opt(inode->i_sb, DELALLOC))
753 if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
754 colour = (current->pid % 16) *
755 (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
757 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
758 return bg_start + colour;