linux-kernel - Re: [dm-devel] [PATCH 02/13] dm: kill dm_rq_bio

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Message-ID: <4FBB160D.9040600@ce.jp.nec.com>
Date:	Tue, 22 May 2012 13:29:01 +0900
From:	"Jun'ichi Nomura" <j-nomura@...jp.nec.com>
To:	device-mapper development <dm-devel@...hat.com>,
	Kent Overstreet <koverstreet@...gle.com>
CC:	Tejun Heo <tj@...nel.org>, axboe@...nel.dk,
	linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, agk@...hat.com,
	Mikulas Patocka <mpatocka@...hat.com>
Subject: Re: [dm-devel] [PATCH 02/13] dm: kill dm_rq_bio_destructor

Hi,

On 05/19/12 03:50, Kent Overstreet wrote:
> On Fri, May 18, 2012 at 05:43:19PM +0100, Alasdair G Kergon wrote:
>> On Fri, May 18, 2012 at 08:57:29AM -0700, Tejun Heo wrote:
>>> Please explain why this is done and how it's safe.  Alasdair / dm
>>> folks, can you please ack this?
>>  
>> I think it's relying on there being never more than one reference on those 
>> bios so that that endio fn, called exactly once, always frees it and there
>> are no dm_puts elsewhere.
> 
> Is that a safe assumption? From my perusal of the code it certainly
> looks like it should be, but I don't know dm all that well.

Doing free_bio_info() in end_clone_bio() is safe.

But there is other problem.
This bio may be put by blk_rq_unprep_clone() and leak memory
without the destructor.

So could it be possible to keep bi_destructor available for this case?

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation
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