Re: [PATCH] ocfs2: call journal flush to mark journal as empty after journal recovery when mount

[Changwei Ge]

Hi Joseph,

On 12/11/19 9:17 PM, Joseph Qi wrote:
> On 19/12/11 18:03, 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.
> I think I've finally understood the problem. But I don't think it has
> been clearly described for reviewing. I strongly suggest you describe
> the problem in the way of timeline, such as in which step, do what
> operation, and what is the status, etc.
>
>
> > This exception happens 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 sb block will be updated after recovery.
> >
> > To fix this problem, use jbd2_journal_flush to mark journal as empty as
> > ocfs2_replay_journal has done.>
> Sounds reasonable. But IMO, it is really a corner use scenario, using
> cluster filesystem in single node...

True, this use case should be rare.
But considering that fixing this is not complicated and does no harm at 
least, I am inclining taking this in. We can only merge it to mainline 
rather than -stable branches. :-)

Thanks,
Changwei


> Thanks,
> Joseph
>
> > 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@xxxxxxx>
> > ---
> >   fs/ocfs2/journal.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
> > index 1afe57f425a0..b8b9d26fa731 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) {
> > +		/* wipe the journal */
> > +		jbd2_journal_lock_updates(journal->j_journal);
> > +		status = jbd2_journal_flush(journal->j_journal);
> > +		jbd2_journal_unlock_updates(journal->j_journal);
> > +		mlog(ML_NOTICE, "journal recovery complete, status=%d", status);
> > +	}
> > +
> >   	status = ocfs2_journal_toggle_dirty(osb, 1, replayed);
> >   	if (status < 0) {
> >   		mlog_errno(status);