Re: [PATCH] rds: rds_ib_device.refcount overflow

[Wengang Wang <wen.gang.wang-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

Haggai,

Thanks for review! I will add the message you suggested and re-post.

thanks,
wengang

在 2015年07月06日 14:18, Haggai Eran 写道:
> On 24/06/2015 07:54, Wengang Wang wrote:
>> There lacks a dropping on rds_ib_device.refcount in case rds_ib_alloc_fmr
>> failed(mr pool running out). this lead to the refcount overflow.
>>
>> A complain in line 117(see following) is seen. From vmcore:
>> s_ib_rdma_mr_pool_depleted is 2147485544 and rds_ibdev->refcount is -2147475448.
>> That is the evidence the mr pool is used up. so rds_ib_alloc_fmr is very likely
>> to return ERR_PTR(-EAGAIN).
>>
>> 115 void rds_ib_dev_put(struct rds_ib_device *rds_ibdev)
>> 116 {
>> 117         BUG_ON(atomic_read(&rds_ibdev->refcount) <= 0);
>> 118         if (atomic_dec_and_test(&rds_ibdev->refcount))
>> 119                 queue_work(rds_wq, &rds_ibdev->free_work);
>> 120 }
>>
>> fix is to drop refcount when rds_ib_alloc_fmr failed.
>>
>> Signed-off-by: Wengang Wang <wen.gang.wang-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
>> ---
>>   net/rds/ib_rdma.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
>> index 273b8bf..657ba9f 100644
>> --- a/net/rds/ib_rdma.c
>> +++ b/net/rds/ib_rdma.c
>> @@ -759,8 +759,10 @@ void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
>>   	}
>>   
>>   	ibmr = rds_ib_alloc_fmr(rds_ibdev);
>> -	if (IS_ERR(ibmr))
>> +	if (IS_ERR(ibmr)) {
>> +		rds_ib_dev_put(rds_ibdev);
>>   		return ibmr;
>> +	}
>>   
>>   	ret = rds_ib_map_fmr(rds_ibdev, ibmr, sg, nents);
>>   	if (ret == 0)
>>
> It seems like the function indeed is missing a put on the rds_ibdev in
> that case.
>
> Reviewed-by: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
>
> You may also want to add:
> Fixes: 3e0249f9c05c ("RDS/IB: add refcount tracking to struct
> rds_ib_device")

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