On 02/12, guoweichao wrote:
>
>
> On 2018/2/12 10:32, Jaegeuk Kim wrote:
> > On 02/12, guoweichao wrote:
> >> Hi Jaegeuk,
> >>
> >> On 2018/2/12 7:32, Jaegeuk Kim wrote:
> >>> On 02/06, Weichao Guo wrote:
> >>>> There is a potential inconsistent metadata case due to a cp block
> >>>> crc invalid in the latest checkpoint caused by hardware issues:
> >>>> 1) write nodes into segment x;
> >>>> 2) write checkpoint A;
> >>>> 3) remove nodes in segment x;
> >>>> 4) write checkpoint B;
> >>>> 5) issue discard or write datas into segment x;
> >>>> 6) sudden power-cut;
> >>>> 7) use checkpoint A after reboot as checkpoint B is invalid
> >>>>
> >>>> This inconsistency may be found after several reboots long time later
> >>>> and the kernel log about cp block crc invalid has disappeared. This
> >>>> makes the root cause of the inconsistency is hard to locate. Let us
> >>>> separate such other part issues from f2fs logical bugs in debug version.
> >>>>
> >>>> Signed-off-by: Weichao Guo <guoweic...@huawei.com>
> >>>> ---
> >>>> fs/f2fs/checkpoint.c | 8 ++++++--
> >>>> 1 file changed, 6 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> >>>> index 8b0945b..16ba96a 100644
> >>>> --- a/fs/f2fs/checkpoint.c
> >>>> +++ b/fs/f2fs/checkpoint.c
> >>>> @@ -737,13 +737,17 @@ static int get_checkpoint_version(struct
> >>>> f2fs_sb_info *sbi, block_t cp_addr,
> >>>> crc_offset = le32_to_cpu((*cp_block)->checksum_offset);
> >>>> if (crc_offset > (blk_size - sizeof(__le32))) {
> >>>> f2fs_msg(sbi->sb, KERN_WARNING,
> >>>> - "invalid crc_offset: %zu", crc_offset);
> >>>> + "invalid crc_offset: %zu at blk_addr: 0x%x",
> >>>> + crc_offset, cp_addr);
> >>>> + f2fs_bug_on(sbi, 1);
> >>>
> >>> I don't think we can use bug_on here, since we're easily getting this when
> >>> power-cut happened in the middle of checkpoint pack writes, which is an
> >>> expected
> >>> behavior. Hmm, we need to consider another way to detect that.
> >> We only check CP block crc here. The two CP blocks may have different CP
> >> versions when
> >> power-cut happened, but their crc value should be valid. IMO, this patch
> >> will trigger a
> >> bug_on only when some external issues cause CP block crc invalid as one 4K
> >> page is
> >> persisted atomically.
> >
> > Huh? This checks crc_offset, not crc? Unfortunately, my simple fault
> > injection
> > test gave this bug_on within a day. The below bug_on seems what you're
> > saying
> > about tho.
> oh sorry, I didn't notice the code line carefully. But which fault injection
> trigger
> this bug_on? The crc_offset is also parts of the CP block, it seems power-cut
> happened
> in middle of writing checkpoint should not produce an invalid crc_offset.
The second cp block can have stale data used by previous part of checkpoint.
>
> Thanks,
>
> >
> >>
> >> Thanks,
> >>>
> >>> Thanks,
> >>>
> >>>> return -EINVAL;
> >>>> }
> >>>>
> >>>> crc = cur_cp_crc(*cp_block);
> >>>> if (!f2fs_crc_valid(sbi, crc, *cp_block, crc_offset)) {
> >>>> - f2fs_msg(sbi->sb, KERN_WARNING, "invalid crc value");
> >>>> + f2fs_msg(sbi->sb, KERN_WARNING,
> >>>> + "invalid crc value at blk_addr: 0x%x", cp_addr);
> >>>> + f2fs_bug_on(sbi, 1);
> >>>> return -EINVAL;
> >>>> }
> >>>>
> >>>> --
> >>>> 2.10.1
> >>>
> >>> .
> >>>
> >
> > .
> >
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