linux-kernel - Re: [PATCH] aio: block exit_aio() until all context requests are completed

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Date:	Thu, 4 Sep 2014 08:47:19 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	Benjamin LaHaise <bcrl@...ck.org>
CC:	<linux-aio@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] aio: block exit_aio() until all context requests are
 completed

Hi Ben,
On 09/03/2014 10:43 PM, Benjamin LaHaise wrote:

> Hi Gu,
> 
> On Wed, Sep 03, 2014 at 05:45:44PM +0800, Gu Zheng wrote:
>> It seems that exit_aio() also needs to wait for all iocbs to complete (like
>> io_destroy), but we missed the wait step in current implemention, so fix
>> it in the same way as we did in io_destroy.
> 
> I actually already have another version of this patch queued up that 
> checks the return value of kill_ioctx().

That's good, but I did not find it, have you sent it to the open list?
IMO, there's no need to check the return value of kill_ioctx(), because
context can be marked as DEAD only by io_destroy(), and io_destroy() is
on the block mode. So if we run into the calling of kill_ioctx() in
exit_aio, the context is surely valid.

Thanks,
Gu

> 
> 		-ben
> 
>> Signed-off-by: Gu Zheng <guz.fnst@...fujitsu.com>
>> ---
>>  fs/aio.c |    7 ++++++-
>>  1 files changed, 6 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/aio.c b/fs/aio.c
>> index 97bc62c..3e35b12 100644
>> --- a/fs/aio.c
>> +++ b/fs/aio.c
>> @@ -793,6 +793,8 @@ void exit_aio(struct mm_struct *mm)
>>  
>>  	for (i = 0; i < table->nr; ++i) {
>>  		struct kioctx *ctx = table->table[i];
>> +		struct completion requests_done =
>> +			COMPLETION_INITIALIZER_ONSTACK(requests_done);
>>  
>>  		if (!ctx)
>>  			continue;
>> @@ -804,7 +806,10 @@ void exit_aio(struct mm_struct *mm)
>>  		 * that it needs to unmap the area, just set it to 0.
>>  		 */
>>  		ctx->mmap_size = 0;
>> -		kill_ioctx(mm, ctx, NULL);
>> +		kill_ioctx(mm, ctx, &requests_done);
>> +
>> +		/* Wait until all IO for the context are done. */
>> +		wait_for_completion(&requests_done);
>>  	}
>>  
>>  	RCU_INIT_POINTER(mm->ioctx_table, NULL);
>> -- 
>> 1.7.7
> 


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