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f2fs: relocate chksum_offset for large_nat_bitmap feature

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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>
This commit is contained in:
Chao Yu 2019-04-22 17:33:53 +08:00 committed by Jaegeuk Kim
parent d7eb8f1cdf
commit b471eb99e6
2 changed files with 16 additions and 1 deletions
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11
fs/f2fs/checkpoint.c
View File

@ -795,6 +795,17 @@ static int get_checkpoint_version(struct f2fs_sb_info *sbi, block_t cp_addr,
return -EINVAL;
}
if (__is_set_ckpt_flags(*cp_block, CP_LARGE_NAT_BITMAP_FLAG)) {
if (crc_offset != CP_MIN_CHKSUM_OFFSET) {
f2fs_put_page(*cp_page, 1);
f2fs_msg(sbi->sb, KERN_WARNING,
"layout of large_nat_bitmap is deprecated, "
"run fsck to repair, chksum_offset: %zu",
crc_offset);
return -EINVAL;
}
}
crc = f2fs_checkpoint_chksum(sbi, *cp_block);
if (crc != cur_cp_crc(*cp_block)) {
f2fs_put_page(*cp_page, 1);

6
fs/f2fs/f2fs.h
View File

@ -1910,7 +1910,11 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) {
offset = (flag == SIT_BITMAP) ?
le32_to_cpu(ckpt->nat_ver_bitmap_bytesize) : 0;
return &ckpt->sit_nat_version_bitmap + offset;
/*
* if large_nat_bitmap feature is enabled, leave checksum
* protection for all nat/sit bitmaps.
*/
return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32);
}
if (__cp_payload(sbi) > 0) {