linux-ext4 - [Bug 14602] New: JBD2 journal abort / checkpoint creation racy?

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Date:	Sat, 14 Nov 2009 12:05:15 GMT
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 14602] New: JBD2 journal abort / checkpoint creation racy?

http://bugzilla.kernel.org/show_bug.cgi?id=14602

           Summary: JBD2 journal abort / checkpoint creation racy?
           Product: File System
           Version: 2.5
    Kernel Version: 2.6.32-rc6
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
        AssignedTo: fs_ext4@...nel-bugs.osdl.org
        ReportedBy: andi-bz@...stfloor.org
        Regression: No

I was testing a new file system feature that triggered IO errors
on inode read. I did not actually change the abort part here
so I believe this is unrelated to my changes.

I had one case during testing where the journal abort didn't work
and jbd2 journal abort errored out.

<putting some stress on the file system>
EXT4-fs error (device sda1): ext4_iget: triggering IO error
EXT4-fs error (device sda1): ext4_put_super: Couldn't clean up the journal

This happens in
ext4_put_super->jbd2_journal_destroy->jbd2_log_do_checkpoint
and then finally 

  if (journal->j_sb_buffer) {
                if (!is_journal_aborted(journal)) {
                        /* We can now mark the journal as empty. */
                        journal->j_tail = 0;
                        journal->j_tail_sequence =
                                ++journal->j_transaction_sequence;
                        jbd2_journal_update_superblock(journal, 1);
                } else {
                        err = -EIO; <------------ this is triggered
                }

So it looks like jbd2_log_do_checkpoint sometimes does not succeed?
It does a couple of retry, maybe that log is not enough.

The problem is not easy to trigger unfortunately, i only saw it very rarely.
I assume it's some race in the checkpoint creation.

I tried to reproduce it with jbd2 debugging enabled, but no luck so far.

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