On 2014/6/10 9:54, Wengang wrote:
> Wenfang,
>
> You have to call the access function before modifying the buffer_head.
> The access function takes care the case that the buffer_head is included in
> the previous transaction.
> In that case, the access function would make a copy of old contents(the right
> content for previous transaction) in the bh.
> If you modified the bh before calling access function, you may destroyed
> previous transaction.
>
I checked the code of modifying the buffer_head, no modifying the bh before
calling access function.
thanks,
vicky
> For this problem, I'd suggest you to check all modification on this bh(for
> inode) and call access function before the first modification and make sure
> the transaction-restart safe.
>
> thanks,
> wengang
>
>
> 于 2014年06月09日 20:54, yangwenfang 写道:
>> 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.yangwenf...@huawei.com>
>> ---
>> fs/ocfs2/aops.c | 20 +++++++++-----------
>> 1 file changed, 9 insertions(+), 11 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index d310d12..1f87c7c 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -1818,16 +1818,6 @@ try_again:
>> if (ret)
>> goto out_commit;
>> }
>> - /*
>> - * We don't want this to fail in ocfs2_write_end(), so do it
>> - * here.
>> - */
>> - ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
>> - OCFS2_JOURNAL_ACCESS_WRITE);
>> - if (ret) {
>> - mlog_errno(ret);
>> - goto out_quota;
>> - }
>>
>> /*
>> * Fill our page array first. That way we've grabbed enough so
>> @@ -2040,8 +2030,16 @@ out_write_size:
>> di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
>> di->i_mtime_nsec = di->i_ctime_nsec =
>> cpu_to_le32(inode->i_mtime.tv_nsec);
>> ocfs2_update_inode_fsync_trans(handle, inode, 1);
>> - ocfs2_journal_dirty(handle, wc->w_di_bh);
>> + ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
>> + OCFS2_JOURNAL_ACCESS_WRITE);
>> + if (ret) {
>> + copied = ret;
>> + mlog_errno(ret);
>> + goto out;
>> + }
>>
>> + ocfs2_journal_dirty(handle, wc->w_di_bh);
>> +out:
>> ocfs2_commit_trans(osb, handle);
>>
>> ocfs2_run_deallocs(osb, &wc->w_dealloc);
>
>
> .
>
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