f2fs: relocate chksum_offset for large_nat_bitmap feature
For large_nat_bitmap feature, there is a design flaw:
Previous:
struct f2fs_checkpoint layout:
+--------------------------+ 0x0000
| checkpoint_ver |
| ...... |
| checksum_offset |------+
| ...... | |
| sit_nat_version_bitmap[] |<-----|-------+
| ...... | | |
| checksum_value |<-----+ |
+--------------------------+ 0x1000 |
| | nat_bitmap + sit_bitmap
| payload blocks | |
| | |
+--------------------------|<-------------+
Obviously, if nat_bitmap size + sit_bitmap size is larger than
MAX_BITMAP_SIZE_IN_CKPT, nat_bitmap or sit_bitmap may overlap
checkpoint checksum's position, once checkpoint() is triggered
from kernel, nat or sit bitmap will be damaged by checksum field.
In order to fix this, let's relocate checksum_value's position
to the head of sit_nat_version_bitmap as below, then nat/sit
bitmap and chksum value update will become safe.
After:
struct f2fs_checkpoint layout:
+--------------------------+ 0x0000
| checkpoint_ver |
| ...... |
| checksum_offset |------+
| ...... | |
| sit_nat_version_bitmap[] |<-----+
| ...... |<-------------+
| | |
+--------------------------+ 0x1000 |
| | nat_bitmap + sit_bitmap
| payload blocks | |
| | |
+--------------------------|<-------------+
Related report and discussion:
https://sourceforge.net/p/linux-f2fs/mailman/message/36642346/
Reported-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
2 files changed