On 2018/7/26 19:52, Chao Yu wrote:
> On 2018/7/24 23:28, Weichao Guo wrote:
>> We may encounter both checkpoints invalid in such a case:
>> 1. write checkpoint A, B, C;
>> 2. sudden power-cut during write checkpoint D;
>> 3. fsck changes the total block count of checkpoint C;
>> 4. sudden power-cut during fsck write checkpoint C in place
>>
>> --------- ---------
>> | ver C | | ver D |
>> | ... | | ... |
>> | content | | content |
>> | ... | | ... |
>> | ver C | | |
>> | ver A | | ver B |
>> --------- ---------
>>
>> As the total # of checkpoint C is changed, an old cp block
>> like ver A or an invalid cp block may be referenced.
>> To avoid both checkpoints invalid, and considering fsck should
>> not update the checkpoint version, fsck could write checkpoint
>> out of place first and then write checkpoint in place. This
>> makes sure the file system is fixed by fsck and at least one
>> of the two checkpoints is valid.
>>
>> Signed-off-by: Weichao Guo <guoweic...@huawei.com>
>> ---
>> fsck/fsck.c | 13 ++++++++++++-
>> fsck/mount.c | 13 ++++++++++++-
>> 2 files changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/fsck/fsck.c b/fsck/fsck.c
>> index 91c8529..28320d5 100644
>> --- a/fsck/fsck.c
>> +++ b/fsck/fsck.c
>> @@ -1954,6 +1954,7 @@ static void fix_checkpoint(struct f2fs_sb_info *sbi)
>> u32 i;
>> int ret;
>> u_int32_t crc = 0;
>> + int phase = 0;
>>
>> if (is_set_ckpt_flags(cp, CP_ORPHAN_PRESENT_FLAG)) {
>> orphan_blks = __start_sum_addr(sbi) - 1;
>> @@ -1975,9 +1976,11 @@ static void fix_checkpoint(struct f2fs_sb_info *sbi)
>> *((__le32 *)((unsigned char *)cp + CHECKSUM_OFFSET)) = cpu_to_le32(crc);
>>
>> cp_blk_no = get_sb(cp_blkaddr);
>> - if (sbi->cur_cp == 2)
>> + /* write checkpoint with current version out of place first */
>> + if (sbi->cur_cp == 1)
>> cp_blk_no += 1 << get_sb(log_blocks_per_seg);
>>
>> +next_step:
>> ret = dev_write_block(cp, cp_blk_no++);
>> ASSERT(ret >= 0);
>>
>> @@ -2002,6 +2005,14 @@ static void fix_checkpoint(struct f2fs_sb_info *sbi)
>> /* Write nat bits */
>> if (flags & CP_NAT_BITS_FLAG)
>> write_nat_bits(sbi, sb, cp, sbi->cur_cp);
>> +
>> + if (phase == 0) {
>> + cp_blk_no = get_sb(cp_blkaddr);
>> + if (sbi->cur_cp == 2)
>> + cp_blk_no += 1 << get_sb(log_blocks_per_seg);
>> + phase++;
>> + goto next_step;
>
> Before goes to second round, we need to keep all cached data being persistent,
> so additional fsync() is needed?
Yes.
>
> Since we are trying to implement OPU style checkpoint() in f2fs-tools, can you
> check whether all caller of {fix,write}_checkpoint() need such logic?
OK, I will resend a revised version of this patch.
Thanks,
>
> Thanks,
>
>> + }
>> }
>>
>> int check_curseg_offset(struct f2fs_sb_info *sbi)
>> diff --git a/fsck/mount.c b/fsck/mount.c
>> index e5574c5..8d7a9bb 100644
>> --- a/fsck/mount.c
>> +++ b/fsck/mount.c
>> @@ -2088,6 +2088,7 @@ void write_checkpoint(struct f2fs_sb_info *sbi)
>> u32 flags = CP_UMOUNT_FLAG;
>> int i, ret;
>> u_int32_t crc = 0;
>> + int phase = 0;
>>
>> if (is_set_ckpt_flags(cp, CP_ORPHAN_PRESENT_FLAG)) {
>> orphan_blks = __start_sum_addr(sbi) - 1;
>> @@ -2105,9 +2106,11 @@ void write_checkpoint(struct f2fs_sb_info *sbi)
>> *((__le32 *)((unsigned char *)cp + CHECKSUM_OFFSET)) = cpu_to_le32(crc);
>>
>> cp_blk_no = get_sb(cp_blkaddr);
>> - if (sbi->cur_cp == 2)
>> + /* write checkpoint with current version out of place first */
>> + if (sbi->cur_cp == 1)
>> cp_blk_no += 1 << get_sb(log_blocks_per_seg);
>>
>> +next_step:
>> /* write the first cp */
>> ret = dev_write_block(cp, cp_blk_no++);
>> ASSERT(ret >= 0);
>> @@ -2142,6 +2145,14 @@ void write_checkpoint(struct f2fs_sb_info *sbi)
>> /* write the last cp */
>> ret = dev_write_block(cp, cp_blk_no++);
>> ASSERT(ret >= 0);
>> +
>> + if (phase == 0) {
>> + cp_blk_no = get_sb(cp_blkaddr);
>> + if (sbi->cur_cp == 2)
>> + cp_blk_no += 1 << get_sb(log_blocks_per_seg);
>> + phase++;
>> + goto next_step;
>> + }
>> }
>>
>> void build_nat_area_bitmap(struct f2fs_sb_info *sbi)
>>
>
>
> .
>
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