linux-kernel - Re: [PATCH v4 1/2] aio: make kiocb->private NUll in init_sync

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Message-ID: <4FED8847.9000204@oracle.com>
Date:	Fri, 29 Jun 2012 18:49:43 +0800
From:	Junxiao Bi <junxiao.bi@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	ocfs2-devel@....oracle.com, linux-aio@...ck.org, mfasheh@...e.com,
	linux-kernel@...r.kernel.org, joe.jin@...cle.com,
	stable@...r.kernel.org, jlbec@...lplan.org
Subject: Re: [PATCH v4 1/2] aio: make kiocb->private NUll in init_sync_kiocb()

On 06/29/2012 05:22 PM, Joel Becker wrote:
> On Thu, Jun 28, 2012 at 03:39:56PM -0700, Andrew Morton wrote:
>> On Wed, 27 Jun 2012 17:09:54 +0800
>> Junxiao Bi <junxiao.bi@...cle.com> wrote:
>>
>>> Ocfs2 uses kiocb.*private as a flag of unsigned long size. In
>>> commit a11f7e6 ocfs2: serialize unaligned aio, the unaligned
>>> io flag is involved in it to serialize the unaligned aio. As
>>> *private is not initialized in init_sync_kiocb() of do_sync_write(),
>>> this unaligned io flag may be unexpectly set in an aligned dio.
>>> And this will cause OCFS2_I(inode)->ip_unaligned_aio decreased
>>> to -1 in ocfs2_dio_end_io(), thus the following unaligned dio
>>> will hang forever at ocfs2_aiodio_wait() in ocfs2_file_aio_write().
>>>
>>> Signed-off-by: Junxiao Bi <junxiao.bi@...cle.com>
>>> Cc: stable@...r.kernel.org
>>> Acked-by: Jeff Moyer <jmoyer@...hat.com>
>>> Acked-by: Joel Becker <jlbec@...lplan.org>
>>> ---
>>>  include/linux/aio.h |    1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/include/linux/aio.h b/include/linux/aio.h
>>> index 2314ad8..b1a520e 100644
>>> --- a/include/linux/aio.h
>>> +++ b/include/linux/aio.h
>>> @@ -140,6 +140,7 @@ struct kiocb {
>>>  		(x)->ki_dtor = NULL;			\
>>>  		(x)->ki_obj.tsk = tsk;			\
>>>  		(x)->ki_user_data = 0;                  \
>>> +		(x)->private = NULL;			\
>>>  	} while (0)
>>>  
>>>  #define AIO_RING_MAGIC			0xa10a10a1
>> hm, that code is rather cruddy.  Pointless macromania.
> Agreed.
>
>> If we do this:
>>
>> static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
>> {
>> 	*kiocb = (struct kiocb) {
>> 			.ki_users = 1,
>> 			.ki_key = KIOCB_SYNC_KEY,
>> 			.ki_filp = filp,
>> 			.ki_obj.tsk = current,
>> 		};
>> }
>>
>> then fs/read_write.o's .text is shrunk from 9857 bytes to 9714, which
>> is rather a lot.
>>
>> But that's all rather irrelevant to your bugfix.
> 	I like your solution.  Junxiao, if you send me that version, I'd
> be happy to take it.
Joel, since Andrew will feed his cleanup patch later on. Please help
merge my patches. Though it is covered by the cleanup patch, but I think
it's useful to merge it, at least we can see from the git log this is
for an ocfs2 hang bug.
>
> Joel
>

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