RE: [PATCH] elevator: fix double release for elevator module

[Chao Yu]

Hi Jens and Jeff,

Thanks for your review and help! :)

Regards,

> -----Original Message-----
> From: Jens Axboe [mailto:axboe@xxxxxxxxx]
> Sent: Friday, April 24, 2015 12:49 AM
> To: Jeff Moyer; Chao Yu
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] elevator: fix double release for elevator module
> 
> On 04/23/2015 08:59 AM, Jeff Moyer wrote:
> > Chao Yu <chao2.yu@xxxxxxxxxxx> writes:
> >
> >> Our issue is descripted in below call path:
> >> ->elevator_init
> >>   ->elevator_init_fn
> >>    ->{cfq,deadline,noop}_init_queue
> >>     ->elevator_alloc
> >>      ->kzalloc_node
> >>     fail to call kzalloc_node and then put module in elevator_alloc;
> >> fail to call elevator_init_fn and then put module again in elevator_init.
> >>
> >> Remove elevator_put invoking in error path of elevator_alloc to avoid
> >> double release issue.
> >>
> >> Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
> >> ---
> >>   block/elevator.c | 5 +----
> >>   1 file changed, 1 insertion(+), 4 deletions(-)
> >>
> >> diff --git a/block/elevator.c b/block/elevator.c
> >> index d146a5e..8985038 100644
> >> --- a/block/elevator.c
> >> +++ b/block/elevator.c
> >> @@ -157,7 +157,7 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
> >>
> >>   	eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
> >>   	if (unlikely(!eq))
> >> -		goto err;
> >> +		return NULL;
> >>
> >>   	eq->type = e;
> >>   	kobject_init(&eq->kobj, &elv_ktype);
> >> @@ -165,9 +165,6 @@ struct elevator_queue *elevator_alloc(struct request_queue *q,
> >>   	hash_init(eq->hash);
> >>
> >>   	return eq;
> >> -err:
> >> -	elevator_put(e);
> >> -	return NULL;
> >>   }
> >>   EXPORT_SYMBOL(elevator_alloc);
> >
> > You could have posted the two patches together, as they are related.
> > Anyway, looks good to me.
> >
> > Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
> 
> Agree, it should be one patch. I've combined them, and applied the fix
> for 4.1. Thanks.
> 
> --
> Jens Axboe

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