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Date:   Thu, 9 Jan 2020 12:51:41 +0100
From:   Jan Kara <jack@...e.cz>
To:     Likai <li.kai4@....com>
Cc:     "tytso@....edu" <tytso@....edu>, "jack@...e.cz" <jack@...e.cz>,
        "yi.zhang@...wei.com" <yi.zhang@...wei.com>,
        "liu.song11@....com.cn" <liu.song11@....com.cn>,
        "xiaoguang.wang@...ux.alibaba.com" <xiaoguang.wang@...ux.alibaba.com>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] jbd2: update log tail info after journal recovery

Hello!

On Wed 04-12-19 03:47:52, Likai wrote:
> Hi,  I meet a new problem that file may be lost althougth it is recorded in the jbd2 journal
> with ocfs2 file system in one node scene(like ext4). Can you give some suggestions for this problem
> and modification patch?
> 
> Test method:
> 1. touch some files after mount
> 2. emergency restart
> 3. mount again, then log tail will not be updated
> 4. touch a new file and confirm that it is recorded in the journal area
> 5.emergency restart again
> 6. the new log will not be replayed becasuse its seq and blknum are not consistent with journal super block although it is an unbroken commit.
> 
> After analizing the codes, its cause is as follow:
> 
> Journal->j_flags will be set JBD2_ABORT in journal_init_common first when mount.
> if this flag is not cleared before journal_reset in journal recovery
> scene, super log tail cannot be updated, then the new commit trans in
> the journal may not be replayed because new commit recover old trans area.
> 
> 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)
> 
> syslog:
> Dec  3 11:41:05 cvknode02 kernel: [ 2265.648622] ocfs2: File system on device (252,1) was not unmounted cleanly, recovering it.
> Dec  3 11:41:05 cvknode02 kernel: [ 2265.649695] fs/jbd2/recovery.c:(do_one_pass, 449): Starting recovery pass 0
> Dec  3 11:41:05 cvknode02 kernel: [ 2265.650407] fs/jbd2/recovery.c:(do_one_pass, 449): Starting recovery pass 1
> Dec  3 11:41:05 cvknode02 kernel: [ 2265.650409] fs/jbd2/recovery.c:(do_one_pass, 449): Starting recovery pass 2
> Dec  3 11:41:05 cvknode02 kernel: [ 2265.650410] fs/jbd2/recovery.c:(jbd2_journal_recover, 278): JBD2: recovery, exit status 0, recovered transactions 13 to 13
> 
> Seq 15 is an unbroken commit, but it cannot be replayed, inode 8257802
> is a new file and it will be lost.
> 
> 
> To fix this problem, I clear JBD2_ABORT flag before journal_reset so that jbd2_journal_update_sb_log_tail
> can update log tail later. After test, it is ok now.

Thanks for the report and the patch! I agree with the analysis and the fix.
This seems to be a bug introduced by commit 85e0c4e89c1b8 "jbd2: if the
journal is aborted then don't allow update of the log tail". So can you
please create a patch with proper changelog, your signed-off-by, unmangled
white-spaces, and also

Fixes: 85e0c4e89c1b "jbd2: if the journal is aborted then don't allow update of the log tail"

tag and resubmit it? Thank you!

								Honza

> 
> ---
> fs/jbd2/journal.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 593f3e31fb21..6fc9fd41830e 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1685,6 +1685,11 @@ int jbd2_journal_load(journal_t *journal)
>                        journal->j_devname);
>                 return -EFSCORRUPTED;
>        }
> +       /*
> +       * clear JBD2_ABORT flag which was initialized in journal_init_common
> +       * here to update log tail information with the newest seq.
> +       */
> +       journal->j_flags &= ~JBD2_ABORT;
>         /* OK, we've finished with the dynamic journal bits:
>         * reinitialise the dynamic contents of the superblock in memory
> @@ -1692,7 +1697,6 @@ int jbd2_journal_load(journal_t *journal)
>        if (journal_reset(journal))
>                 goto recovery_error;
> -        journal->j_flags &= ~JBD2_ABORT;
>        journal->j_flags |= JBD2_LOADED;
>        return 0;
> -------------------------------------------------------------------------------------------------------------------------------------
> ?????????????????????????????????
> ????????????????????????????????????????
> ????????????????????????????????????????
> ???
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-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

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