Re: [PATCH RFC] jbd2: detect old record when do journal scan

[yebin]

On 2022/8/19 17:54, Jan Kara wrote:
> On Wed 10-08-22 09:34:42, Ye Bin wrote:
> > As https://github.com/tytso/e2fsprogs/issues/120 describe tune2fs do not update
> > j_tail_sequence when do journal recovery. This maybe recover old journal record,
> > then will lead to file system corruption.
> > To avoid file system corruption in this case, if detect current transaction's
> > commit time earlier than previous transaction's commit time when do journal
> > scan, just return error.
> >
> > Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
> Thanks for the patch! Let me see if I understand your concern right. You
> are concerned about the following scenario:
>
> 1) Kernel uses the filesystem, there's a crash.
> 2) E2fsprogs replays the journal but fails to update sb->s_sequence in the
> journal superblock.
> 3) Kernel mounts the fs again - however note that even if kernel skips
> recovery, it does scan the journal jbd2_journal_skip_recovery() and
> journal->j_transaction_sequence is set based on the last transaction found
> in the journal.
>
> So I don't think there is really possibility we will quickly reuse some
> transaction IDs and thus possibility of corruption on replay? Am I missing
> something?
>
> 								Honza
The file system corruption I encountered was indeed because e2fsprogs 
did not update
journal - > J_ transaction_ Sequence leads to replay the old transaction.
So I wonder whether the kernel should detect this kind of exception, at 
least when there
is a file system corruption, there are clues to trace.
> > ---
> >   fs/jbd2/recovery.c | 11 ++++++++++-
> >   1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
> > index f548479615c6..f3def21a96a5 100644
> > --- a/fs/jbd2/recovery.c
> > +++ b/fs/jbd2/recovery.c
> > @@ -812,8 +812,17 @@ static int do_one_pass(journal_t *journal,
> >   					break;
> >   				}
> >   			}
> > -			if (pass == PASS_SCAN)
> > +			if (pass == PASS_SCAN) {
> > +				if (commit_time < last_trans_commit_time) {
> > +					pr_err("JBD2: old journal record found "
> > +					       "in transaction %u\n",
> > +					       next_commit_ID);
> > +					err = -EFSBADCRC;
> > +					brelse(bh);
> > +					goto failed;
> > +				}
> >   				last_trans_commit_time = commit_time;
> > +			}
> >   			brelse(bh);
> >   			next_commit_ID++;
> >   			continue;
> > --
> > 2.31.1