Re: [PATCH] lightnvm: pblk: fix bio leak on large sized io

["Javier González" <javier@javigon.com>]

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> On 30 Jan 2019, at 15.06, Matias Bjørling <mb@lightnvm.io> wrote:
> 
> On 1/30/19 2:53 AM, 김찬솔 wrote:
>> Changes:
>>  1. Function pblk_rw_io to get bio* as a reference
>>  2. In pblk_rw_io bio_put call on read case removed
>> A fix to address issue where
>>  1. pblk_make_rq calls pblk_rw_io passes bio* pointer as a value (0xA)
>>  2. pblk_rw_io calls blk_queue_split passing bio* pointer as reference
>>  3. In blk_queue_split, when there is a split, the original bio* (0xA)
>>     is passed to generic_make_requests, and the newly allocated bio is
>>     returned
>>  4. If NVM_IO_DONE returned, pblk_make_rq calls bio_endio on the bio*,
>>     that is not the one returned by blk_queue_split
>>  5. As a result bio_endio is not called on the newly allocated bio.
> 
> The commit message needs a bit of massaging. The Changes: paragraph is not needed (that is what the patch is for). Also, please redo the second paragraph in without the bullets.
> 
>> Signed-off-by: chansol.kim <chansol.kim@samsung.com>
>> ---
>>  drivers/lightnvm/pblk-init.c | 22 ++++++++--------------
>>  1 file changed, 8 insertions(+), 14 deletions(-)
>> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
>> index b57f764d..4efc929 100644
>> --- a/drivers/lightnvm/pblk-init.c
>> +++ b/drivers/lightnvm/pblk-init.c
>> @@ -31,30 +31,24 @@ static DECLARE_RWSEM(pblk_lock);
>>  struct bio_set pblk_bio_set;
>>    static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
>> -			  struct bio *bio)
>> +			  struct bio **bio)
> 
> I am not sure why the **bio change is needed. Can you elaborate?

bio_split creates a new bio and queues the original one again. If the
reference is not updated then the newly created bio is never freed when
NVM_IO_DONE is returned to pblk_make_rq(), thus resulting on a leak.

Javier

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