Re: [PATCHSET 0/2] Don't let blk_put_request leak BIOs

[Boaz Harrosh <bharrosh@panasas.com>]

Jens Axboe wrote:
> On Thu, Mar 19 2009, Boaz Harrosh wrote:
>> Hi Jens
>>
>> You never commented on these patches. Please have a look?
>>
>> The issue is that if we map some memory into a request but then
>> do not execute it. Then calling blk_put_request() will leak the bio(s)
>> unless one does an ugly code like:
>> -	struct bio *bio;
>> -
>> -	while ((bio = rq->bio) != NULL) {
>> -		rq->bio = bio->bi_next;
>> -		bio_endio(bio, 0);
>> -	}

This is the code I have today in osd_initiator.c (In scsi-misc tree)

> 
> Sorry, I think this is a horrible design. blk_put_request() doesn't care
> about any data attachments, in fact (if possible) it should go BUG() if
> the request hasn't been completed in some way or other. It deals with
> the deallocation part, blk_get_request() doesn't attach any data. The
> end result with code like the above is an assymmetric API.
> 
>> This problem arise in OSD when we can fail to setup the write
>> or the read side and then we must cleanup the other half.
>> Same problem exist in bsg, on bidi commands. But there the bio
>> is just leaked on the error path, it does not do the ugly loop above.
> 
> These drivers should just be fixed, then.
> 
> So if you have spotted this problem in eg bsg, then please send a patch
> for that to Tomo!
> 

Then the above code taken from today's osd_initiator is good? People where
complaining that it is not good, because it is messing up with internal
block structures.

What about just exporting an blk_rq_abort(struct request *req) that is
the same as PATCH 1/2. But is not called from blk_put_request ?

Boaz