[Ocfs2-devel] ocfs2: Should move ocfs2_start_trans out of lock_page

[Joseph Qi]

Hi Joel,
Thanks very much for replying this message.
Actually we just met this issue in a case which did a mess of read/write
IOs.
And after analyzing, we found it is just the lock_page that caused this
issue.

We have tried to solve this issue by looking up ext4. Since there are 5
functions related, it requires a lot code changes. So firstly I'd like
to get a second opinion from you.

On 2013/6/29 21:17, Joel Becker wrote:
> I'm pretty sure we did it for a reason, which means we need to think
> about it more than just looking at ext4.  Remember that we get access
> coming from other node actions.
> 
> Joel
> 
> On Mon, Jun 24, 2013 at 04:55:20PM +0800, Joseph Qi wrote:
>> Any different opinion?
>>
>> On 2013/6/19 16:17, Joseph Qi wrote:
>>> Currently ocfs2_start_trans/ocfs2_commit_trans are in
>>> lock_page/unlock_page. This may cause dead lock.
>>>
>>> Here is the situation:
>>> write -> lock_page -> ocfs2_start_trans -> ocfs2_commit_trans -> unlock_page
>>> ocfs2_start_trans/ocfs2_commit_trans calls
>>> jbd2_journal_start/jbd2_journal_stop which may also call lock_page. So
>>> if the page operated is unfortunately the same with the page to be
>>> committed, dead lock happens.
>>>
>>> In ext4, lock_page/unlock_page are in
>>> ext4_journal_start/ext4_journal_stop, this can avoid such kind of dead
>>> lock. So I think we should move ocfs2_start_trans/ocfs2_commit_trans out
>>> of lock_page/unlock_page.
>>>
>>> Totally there are 5 related functions:
>>> ocfs2_write_begin_nolock
>>> ocfs2_write_begin_inline
>>> ocfs2_write_end_nolock
>>> ocfs2_write_zero_page
>>> ocfs2_convert_inline_data_to_extents
>>>
>>>
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>>> Ocfs2-devel mailing list
>>> Ocfs2-devel at oss.oracle.com
>>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>>>
>>>
>>
>>
>>
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>