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 <[email protected]>
> ---
> 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?
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?
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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