Commit 49a00e7b authored Apr 22, 2019 by Chao Yu Committed by Jaegeuk Kim May 08, 2019

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>

parent 16794d90

fs/f2fs/checkpoint.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -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);

fs/f2fs/f2fs.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -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) {