Re: [PATCH] rds: rds_ib_device.refcount overflow

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

[-- Attachment #1: Type: text/plain, Size: 2266 bytes --]

On 07/12/2015 09:18 PM, Wengang Wang wrote:
> Hi Doug,
> 
> How do you think about this patch?

Sorry, I picked this up already.  I must have missed sending out the
acknowledgment on this one.

> thanks,
> wengang
> 
> 在 2015年07月06日 14:35, Wengang Wang 写道:
>> Fixes: 3e0249f9c05c ("RDS/IB: add refcount tracking to struct
>> rds_ib_device")
>>
>> 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>
>> Reviewed-by: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@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)
> 
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD



[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 884 bytes --]