[U-Boot] [PATCH v3 09/13] ext4: After completely filled group, scan next group from the beginning

Stefan Brüns
2016-08-28T20:42:34Z

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 Br?ns <stefan.bruens@rwth-aachen.de>
---
fs/ext4/ext4_common.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

v3: Patch added to series

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 1ebdbe6..362668b 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -895,8 +895,8 @@ 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) {
@@ -914,8 +914,9 @@ 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;
}

@@ -932,6 +933,7 @@ 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;
}

--
2.9.3