Messages in this thread | | | Subject | Re: [Ocfs2-devel] [PATCH v3] ocfs2: call journal flush to mark journal as empty after journal recovery when mount | From | Changwei Ge <> | Date | Sat, 21 Dec 2019 15:24:55 +0800 |
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On 12/20/19 8:52 PM, Jiangyiwen wrote: > On 2019/12/20 17:33, Likai wrote: >> On 2019/12/20 17:14, piaojun wrote: >>> On 2019/12/20 9:11, Joseph Qi wrote: >>>> On 19/12/19 22:15, piaojun wrote: >>>>> On 2019/12/17 10:01, Kai Li wrote: >>>>>> If journal is dirty when mount, it will be replayed but jbd2 sb >>>>>> log tail cannot be updated to mark a new start because >>>>>> journal->j_flag has already been set with JBD2_ABORT first >>>>>> in journal_init_common. When a new transaction is committed, it >>>>>> will be recored in block 1 first(journal->j_tail is set to 1 in >>>>>> journal_reset).If emergency restart happens again before journal >>>>>> super block is updated unfortunately, the new recorded trans will >>>>>> not be replayed in the next mount. >>>>>> >>>>>> The following steps describe this procedure in detail. >>>>>> 1. mount and touch some files >>>>>> 2. these transactions are committed to journal area but not >>>>>> checkpointed >>>>>> 3. emergency restart >>>>>> 4. mount again and its journals are replayed >>>>>> 5. journal super block's first s_start is 1, but its s_seq is not >>>>>> updated >>>>>> 6. touch a new file and its trans is committed but not checkpointed > > Hi, > > I wonder that in this step, does the function > jbd2_journal_commit_transaction() return? > I understand only jbd2_journal_commit_transaction() return it means the > transaction > is committed completely, and the s_seq can be updated in > jbd2_journal_commit_transaction()->jbd2_update_log_tail(), so I don't > know how > this scenario happened. > > If emergency restart happens in before jbd2_journal_commit_transaction()
The trick is that jbd2 kernel thread even doesn't have a chance to to update tail. Assuming that a timepoint sits between *mount completion* and the *first iteration* of committing work that jbd2 thread.
-Changwei
> return, > I think this transaction shouldn't be a valid transaction. > > Can you explain where the specific function is executed? > > Thanks, > Yiwen. > >>>>>> 7. emergency restart again >>>>>> 8. mount and journal is dirty, but trans committed in 6 will not be >>>>>> replayed. >>>>>> >>>>>> This exception happens easily when this lun is used by only one >>>>>> node. If it >>>>>> is used by multi-nodes, other node will replay its journal and its >>>>>> journal super block will be updated after recovery like what this >>>>>> patch >>>>>> does. >>>>>> >>>>>> ocfs2_recover_node->ocfs2_replay_journal. >>>>>> >>>>>> The following jbd2 journal can be generated by touching a new file >>>>>> after >>>>>> journal is replayed, and seq 15 is the first valid commit, but >>>>>> first seq >>>>>> is 13 in journal super block. >>>>>> logdump: >>>>>> Block 0: Journal Superblock >>>>>> Seq: 0 Type: 4 (JBD2_SUPERBLOCK_V2) >>>>>> Blocksize: 4096 Total Blocks: 32768 First Block: 1 >>>>>> First Commit ID: 13 Start Log Blknum: 1 >>>>>> Error: 0 >>>>>> Feature Compat: 0 >>>>>> Feature Incompat: 2 block64 >>>>>> Feature RO compat: 0 >>>>>> Journal UUID: 4ED3822C54294467A4F8E87D2BA4BC36 >>>>>> FS Share Cnt: 1 Dynamic Superblk Blknum: 0 >>>>>> Per Txn Block Limit Journal: 0 Data: 0 >>>>>> >>>>>> Block 1: Journal Commit Block >>>>>> Seq: 14 Type: 2 (JBD2_COMMIT_BLOCK) >>>>>> >>>>>> Block 2: Journal Descriptor >>>>>> Seq: 15 Type: 1 (JBD2_DESCRIPTOR_BLOCK) >>>>>> No. Blocknum Flags >>>>>> 0. 587 none >>>>>> UUID: 00000000000000000000000000000000 >>>>>> 1. 8257792 JBD2_FLAG_SAME_UUID >>>>>> 2. 619 JBD2_FLAG_SAME_UUID >>>>>> 3. 24772864 JBD2_FLAG_SAME_UUID >>>>>> 4. 8257802 JBD2_FLAG_SAME_UUID >>>>>> 5. 513 JBD2_FLAG_SAME_UUID JBD2_FLAG_LAST_TAG >>>>>> ... >>>>>> Block 7: Inode >>>>>> Inode: 8257802 Mode: 0640 Generation: 57157641 (0x3682809) >>>>>> FS Generation: 2839773110 (0xa9437fb6) >>>>>> CRC32: 00000000 ECC: 0000 >>>>>> Type: Regular Attr: 0x0 Flags: Valid >>>>>> Dynamic Features: (0x1) InlineData >>>>>> User: 0 (root) Group: 0 (root) Size: 7 >>>>>> Links: 1 Clusters: 0 >>>>>> ctime: 0x5de5d870 0x11104c61 -- Tue Dec 3 11:37:20.286280801 2019 >>>>>> atime: 0x5de5d870 0x113181a1 -- Tue Dec 3 11:37:20.288457121 2019 >>>>>> mtime: 0x5de5d870 0x11104c61 -- Tue Dec 3 11:37:20.286280801 2019 >>>>>> dtime: 0x0 -- Thu Jan 1 08:00:00 1970 >>>>>> ... >>>>>> Block 9: Journal Commit Block >>>>>> Seq: 15 Type: 2 (JBD2_COMMIT_BLOCK) >>>>>> >>>>>> The following is jouranl recovery log when recovering the upper jbd2 >>>>>> journal when mount again. >>>>>> syslog: >>>>>> [ 2265.648622] ocfs2: File system on device (252,1) was not >>>>>> unmounted cleanly, recovering it. >>>>>> [ 2265.649695] fs/jbd2/recovery.c:(do_one_pass, 449): Starting >>>>>> recovery pass 0 >>>>>> [ 2265.650407] fs/jbd2/recovery.c:(do_one_pass, 449): Starting >>>>>> recovery pass 1 >>>>>> [ 2265.650409] fs/jbd2/recovery.c:(do_one_pass, 449): Starting >>>>>> recovery pass 2 >>>>>> [ 2265.650410] fs/jbd2/recovery.c:(jbd2_journal_recover, 278): >>>>>> JBD2: recovery, exit status 0, recovered transactions 13 to 13 >>>>>> >>>>>> Due to first commit seq 13 recorded in journal super is not >>>>>> consistent >>>>>> with the value recorded in block 1(seq is 14), journal recovery >>>>>> will be >>>>>> terminated before seq 15 even though it is an unbroken commit, inode >>>>>> 8257802 is a new file and it will be lost. >>>>>> >>>>>> Signed-off-by: Kai Li <li.kai4@h3c.com> >>>>>> --- >>>>>> fs/ocfs2/journal.c | 8 ++++++++ >>>>>> 1 file changed, 8 insertions(+) >>>>>> >>>>>> diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c >>>>>> index 1afe57f425a0..68ba354cf361 100644 >>>>>> --- a/fs/ocfs2/journal.c >>>>>> +++ b/fs/ocfs2/journal.c >>>>>> @@ -1066,6 +1066,14 @@ int ocfs2_journal_load(struct ocfs2_journal >>>>>> *journal, int local, int replayed) >>>>>> ocfs2_clear_journal_error(osb->sb, journal->j_journal, >>>>>> osb->slot_num); >>>>>> + if (replayed) { >>>>>> + jbd2_journal_lock_updates(journal->j_journal); >>>>>> + status = jbd2_journal_flush(journal->j_journal); >>>>> What if jbd2_journal_flush gets failed? The 's_sequence' and 's_start' >>>>> won't be reset, and I wonder if the problem still remains. >>>>> >>>> Yes, but we don't want this to fail the mount process, instead we >>>> just log >>>> an error and system administrator should know the result. >>>> >>> Thanks for your reply and I have another question about this issue. IMO >>> the second trans is not complete as jbd2 sb has not been updated, so we >>> do not need to replay it when mount again. >>> >>> Jun >>> >>> >> I don't think so. The problem is that jbd2 sb should be updated to mark >> a new start after mount rather than whether trans committed later is >> complete or not. >> >> In fact , the trans is complete too as the commit log described. >> >> Thanks >> >> >> _______________________________________________ >> Ocfs2-devel mailing list >> Ocfs2-devel@oss.oracle.com >> https://oss.oracle.com/mailman/listinfo/ocfs2-devel >> >> . >> >
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