Hi Changwei,
On 2018/1/25 19:59, Changwei Ge wrote:
> Hi Jun,
>
> On 2018/1/25 10:41, piaojun wrote:
>> We should not reuse the dirty bh in jbd2 directly due to the following
>> situation:
>>
>> 1. When removing extent rec, we will dirty the bhs of extent rec and
> Quick questions:
> Do you mean current code puts modifying extent records belonging to a certain
> file and modifying truncate log into the same transaction?
> If so, forgive me since I didn't figure it out. Could you point out in your
> following sequence diagram?
>
> Afterwards, I can understand the issue your change log is describing better.
>
> Thanks,
> Changwei
>
Yes, I mean they are in the same transaction as below:
ocfs2_remove_btree_range
ocfs2_remove_extent // modify extent records
ocfs2_truncate_log_append // modify truncate log
thanks,
Jun
>> truncate log at the same time, and hand them over to jbd2.
>> 2. The bhs are not flushed to disk due to abnormal storage link.
>> 3. After a while the storage link become normal. Truncate log flush
>> worker triggered by the next space reclaiming found the dirty bh of
>> truncate log and clear its 'BH_Write_EIO' and then set it uptodate
>> in __ocfs2_journal_access():
>>
>> ocfs2_truncate_log_worker
>> ocfs2_flush_truncate_log
>> __ocfs2_flush_truncate_log
>> ocfs2_replay_truncate_records
>> ocfs2_journal_access_di
>> __ocfs2_journal_access // here we clear io_error and set 'tl_bh'
>> uptodata.
>>
>> 4. Then jbd2 will flush the bh of truncate log to disk, but the bh of
>> extent rec is still in error state, and unfortunately nobody will
>> take care of it.
>> 5. At last the space of extent rec was not reduced, but truncate log
>> flush worker have given it back to globalalloc. That will cause
>> duplicate cluster problem which could be identified by fsck.ocfs2.
>>
>> So we should return -EIO in case of ruining atomicity and consistency
>> of space reclaim.
>>
>> Fixes: acf8fdbe6afb ("ocfs2: do not BUG if buffer not uptodate in
>> __ocfs2_journal_access")
>>
>> Signed-off-by: Jun Piao <piao...@huawei.com>
>> Reviewed-by: Yiwen Jiang <jiangyi...@huawei.com>
>> ---
>> fs/ocfs2/journal.c | 45 +++++++++++++++++++++++++++++++++++----------
>> 1 file changed, 35 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
>> index 3630443..d769ca2 100644
>> --- a/fs/ocfs2/journal.c
>> +++ b/fs/ocfs2/journal.c
>> @@ -666,21 +666,46 @@ static int __ocfs2_journal_access(handle_t *handle,
>> /* we can safely remove this assertion after testing. */
>> if (!buffer_uptodate(bh)) {
>> mlog(ML_ERROR, "giving me a buffer that's not uptodate!\n");
>> - mlog(ML_ERROR, "b_blocknr=%llu\n",
>> - (unsigned long long)bh->b_blocknr);
>> + mlog(ML_ERROR, "b_blocknr=%llu, b_state=0x%lx\n",
>> + (unsigned long long)bh->b_blocknr, bh->b_state);
>>
>> lock_buffer(bh);
>> /*
>> - * A previous attempt to write this buffer head failed.
>> - * Nothing we can do but to retry the write and hope for
>> - * the best.
>> + * We should not reuse the dirty bh directly due to the
>> + * following situation:
>> + *
>> + * 1. When removing extent rec, we will dirty the bhs of
>> + * extent rec and truncate log at the same time, and
>> + * hand them over to jbd2.
>> + * 2. The bhs are not flushed to disk due to abnormal
>> + * storage link.
>> + * 3. After a while the storage link become normal.
>> + * Truncate log flush worker triggered by the next
>> + * space reclaiming found the dirty bh of truncate log
>> + * and clear its 'BH_Write_EIO' and then set it uptodate
>> + * in __ocfs2_journal_access():
>> + *
>> + * ocfs2_truncate_log_worker
>> + * ocfs2_flush_truncate_log
>> + * __ocfs2_flush_truncate_log
>> + * ocfs2_replay_truncate_records
>> + * ocfs2_journal_access_di
>> + * __ocfs2_journal_access
>> + *
>> + * 4. Then jbd2 will flush the bh of truncate log to disk,
>> + * but the bh of extent rec is still in error state, and
>> + * unfortunately nobody will take care of it.
>> + * 5. At last the space of extent rec was not reduced,
>> + * but truncate log flush worker have given it back to
>> + * globalalloc. That will cause duplicate cluster problem
>> + * which could be identified by fsck.ocfs2.
>> + *
>> + * So we should return -EIO in case of ruining atomicity
>> + * and consistency of space reclaim.
>> */
>> if (buffer_write_io_error(bh) && !buffer_uptodate(bh)) {
>> - clear_buffer_write_io_error(bh);
>> - set_buffer_uptodate(bh);
>> - }
>> -
>> - if (!buffer_uptodate(bh)) {
>> + mlog(ML_ERROR, "A previous attempt to write this "
>> + "buffer head failed\n");
>> unlock_buffer(bh);
>> return -EIO;
>> }
>>
> .
>
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