Messages in this thread Patch in this message | | | From | Chao Yu <> | Subject | [PATCH v2 2/2] f2fs: relocate chksum_offset for large_nat_bitmap feature | Date | Fri, 26 Apr 2019 10:25:54 +0800 |
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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> --- v2: - improve hint message suggested by Ju Hyung. - move verification to f2fs_sanity_check_ckpt(). fs/f2fs/f2fs.h | 4 +++- fs/f2fs/super.c | 13 +++++++++++++ 2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 119bc5a9783e..aa71c1aa9eaa 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -1909,9 +1909,11 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag) int offset; if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) { + unsigned int chksum_size = sizeof(__le32); + offset = (flag == SIT_BITMAP) ? le32_to_cpu(ckpt->nat_ver_bitmap_bytesize) : 0; - return &ckpt->sit_nat_version_bitmap + offset; + return &ckpt->sit_nat_version_bitmap + offset + chksum_size; } if (__cp_payload(sbi) > 0) { diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index fefc8cc6e756..22241bb866df 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -2714,6 +2714,19 @@ int f2fs_sanity_check_ckpt(struct f2fs_sb_info *sbi) return 1; } + if (__is_set_ckpt_flags(ckpt, CP_LARGE_NAT_BITMAP_FLAG)) { + unsigned int chksum_offset; + + chksum_offset = le32_to_cpu(ckpt->checksum_offset); + if (chksum_offset != CP_MIN_CHKSUM_OFFSET) { + f2fs_msg(sbi->sb, KERN_WARNING, + "using deprecated layout of large_nat_bitmap, " + "please run fsck v1.13.0 or higher to repair, " + "chksum_offset: %u", chksum_offset); + return 1; + } + } + if (unlikely(f2fs_cp_error(sbi))) { f2fs_msg(sbi->sb, KERN_ERR, "A bug case: need to run fsck"); return 1; -- 2.18.0.rc1
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