[Ocfs2-devel] [patch 17/28] ocfs2: call ocfs2_journal_access_di() before ocfs2_journal_dirty() in ocfs2_write_end_nolock()

[Mark Fasheh]

On Wed, Aug 26, 2015 at 03:12:06PM -0700, Andrew Morton wrote:
> From: yangwenfang <vicky.yangwenfang at huawei.com>
> Subject: ocfs2: call ocfs2_journal_access_di() before ocfs2_journal_dirty() in ocfs2_write_end_nolock()
> 
> 1: After we call ocfs2_journal_access_di() in ocfs2_write_begin(),
>    jbd2_journal_restart() may also be called, in this function transaction
>    A's t_updates-- and obtains a new transaction B.  If
>    jbd2_journal_commit_transaction() is happened to commit transaction A,
>    when t_updates==0, it will continue to complete commit and unfile
>    buffer.
> 
>    So when jbd2_journal_dirty_metadata(), the handle is pointed a new
>    transaction B, and the buffer head's journal head is already freed,
>    jh->b_transaction == NULL, jh->b_next_transaction == NULL, it returns
>    EINVAL, So it triggers the BUG_ON(status).
> 
> thread 1                                          jbd2
> ocfs2_write_begin                     jbd2_journal_commit_transaction
> ocfs2_write_begin_nolock
>   ocfs2_start_trans
>     jbd2__journal_start(t_updates+1,
>                        transaction A)
>     ocfs2_journal_access_di
>     ocfs2_write_cluster_by_desc
>       ocfs2_mark_extent_written
>         ocfs2_change_extent_flag
>           ocfs2_split_extent
>             ocfs2_extend_rotate_transaction
>               jbd2_journal_restart
>               (t_updates-1,transaction B) t_updates==0
>                                         __jbd2_journal_refile_buffer
>                                         (jh->b_transaction = NULL)
> ocfs2_write_end
> ocfs2_write_end_nolock
>     ocfs2_journal_dirty
>         jbd2_journal_dirty_metadata(bug)
>    ocfs2_commit_trans
> 
> 2.  In ext4, I found that: jbd2_journal_get_write_access() called by
>    ext4_write_end.
> 
> ext4_write_begin
>     ext4_journal_start
>         __ext4_journal_start_sb
>             ext4_journal_check_start
>             jbd2__journal_start
> 
> ext4_write_end
>     ext4_mark_inode_dirty
>         ext4_reserve_inode_write
>             ext4_journal_get_write_access
>                 jbd2_journal_get_write_access
>         ext4_mark_iloc_dirty
>             ext4_do_update_inode
>                 ext4_handle_dirty_metadata
>                     jbd2_journal_dirty_metadata
> 
> 3. So I think we should put ocfs2_journal_access_di before
>    ocfs2_journal_dirty in the ocfs2_write_end.  and it works well after my
>    modification.
> 
> Signed-off-by: vicky <vicky.yangwenfang at huawei.com>
> Cc: Mark Fasheh <mfasheh at suse.com>
> Cc: Joel Becker <jlbec at evilplan.org>
> Cc: Zhangguanghui <zhang.guanghui at h3c.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Reviewed-by: Mark Fasheh <mfasheh at suse.de>
	--Mark

--
Mark Fasheh