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ext4: After completely filled group, scan next group from the beginning

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The last free block of a block group may be in its middle. After it has
been allocated, the next block group should be scanned from its beginning.

The following command triggers the bad behaviour (on a blocksize 1024 fs):

./sandbox/u-boot -c 'i=0; host bind 0 ./disk.raw ;
	while test $i -lt 260 ; do echo $i; setexpr i $i + 1;
		ext4write host 0:2 0 /X${i} 0x1450; done ;
	ext4write host 0:2 0 /X240 0x2000 ; '

When 'X240' is extended from 5200 byte to 8192 byte, the new blocks should
start from the first free block (8811), but it uses the blocks 8098-8103
and 16296-16297 -- 8103 + 1 + 8192 = 16296. This can be shown with
debugfs, commands 'ffb' and 'stat X240'.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
This commit is contained in:
Stefan Brüns 2016-09-06 04:36:49 +02:00 committed by Tom Rini
parent e927265225
commit a9fa0ed183
1 changed files with 5 additions and 3 deletions
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8
fs/ext4/ext4_common.c
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@ -903,8 +903,8 @@ uint32_t ext4fs_get_new_blk_no(void)
goto fail;
} else {
restart:
fs->curr_blkno++;
restart:
/* get the blockbitmap index respective to blockno */
bg_idx = fs->curr_blkno / blk_per_grp;
if (fs->blksz == 1024) {
@ -922,8 +922,9 @@ restart:
if (bgd[bg_idx].free_blocks == 0) {
debug("block group %u is full. Skipping\n", bg_idx);
fs->curr_blkno = fs->curr_blkno + blk_per_grp;
fs->curr_blkno--;
fs->curr_blkno = (bg_idx + 1) * blk_per_grp;
if (fs->blksz == 1024)
fs->curr_blkno += 1;
goto restart;
}
@ -940,6 +941,7 @@ restart:
bg_idx) != 0) {
debug("going for restart for the block no %ld %u\n",
fs->curr_blkno, bg_idx);
fs->curr_blkno++;
goto restart;
}