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

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Message-ID: <76d8166c-afe9-fc63-98b2-5293e3956669@linux.alibaba.com>
Date:   Wed, 11 Dec 2019 21:17:23 +0800
From:   Joseph Qi <joseph.qi@...ux.alibaba.com>
To:     Kai Li <li.kai4@....com>, mark@...heh.com, jlbec@...lplan.org,
        chge@...ux.alibaba.com
Cc:     ocfs2-devel@....oracle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ocfs2: call journal flush to mark journal as empty after
 journal recovery when mount



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...

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@....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..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);
>