Re: [PATCH v8 rdma-next 3/7] RDMA/efa: Use the common mmap_xa helpers

[Gal Pressman <galpress@amazon.com>]

On 30/08/2019 9:15, Michal Kalderon wrote:
>> From: Gal Pressman <galpress@amazon.com>
>> Sent: Thursday, August 29, 2019 5:21 PM
>>
>> On 27/08/2019 16:28, Michal Kalderon wrote:
>>> +static void efa_qp_user_mmap_entries_remove(struct efa_ucontext
>> *ucontext,
>>> +					    struct efa_qp *qp)
>>> +{
>>> +	rdma_user_mmap_entry_remove(&ucontext->ibucontext, qp-
>>> sq_db_mmap_key);
>>> +	rdma_user_mmap_entry_remove(&ucontext->ibucontext,
>>> +				    qp->llq_desc_mmap_key);
>>> +	rdma_user_mmap_entry_remove(&ucontext->ibucontext, qp-
>>> rq_mmap_key);
>>> +	rdma_user_mmap_entry_remove(&ucontext->ibucontext,
>>> +qp->rq_db_mmap_key);
>>
>> Please remove the entries in reverse insertion order.
> I don't mind fixing, but why ? 

So the flows will be symmetric.

>>
>>> +}
>>> +
>>> @@ -767,15 +726,17 @@ struct ib_qp *efa_create_qp(struct ib_pd *ibpd,
>>>
>>>  	return &qp->ibqp;
>>>
>>> +err_remove_mmap_entries:
>>> +	efa_qp_user_mmap_entries_remove(ucontext, qp);
>>>  err_destroy_qp:
>>>  	efa_destroy_qp_handle(dev, create_qp_resp.qp_handle);
>>>  err_free_mapped:
>>> -	if (qp->rq_size) {
>>> +	if (qp->rq_dma_addr)
>>
>> What's the difference?
> Seemed a better query since it now only covers the rq_dma_addr unmapping. 
> 
>>
>>>  		dma_unmap_single(&dev->pdev->dev, qp->rq_dma_addr,
>> qp->rq_size,
>>>  				 DMA_TO_DEVICE);
>>> -		if (!rq_entry_inserted)
>>> -			free_pages_exact(qp->rq_cpu_addr, qp->rq_size);
>>> -	}
>>> +
>>> +	if (qp->rq_mmap_key == RDMA_USER_MMAP_INVALID)
>>> +		free_pages_exact(qp->rq_cpu_addr, qp->rq_size);
>>
>> This should be inside the previous if statement, otherwise it might try to free
>> pages that weren't allocated.
> If they weren't allocated the key will be INVALID and they won't be freed.

If the key is INVALID you call free_pages_exact, but rq_cpu_addr might have
never been allocated (if RQ is of size zero).

> 
>>
>>>  err_free_qp:
>>>  	kfree(qp);
>>>  err_out:
>>> @@ -887,6 +848,7 @@ static int efa_destroy_cq_idx(struct efa_dev *dev,
>>> int cq_idx)
>>>
>>>  void efa_destroy_cq(struct ib_cq *ibcq, struct ib_udata *udata)  {
>>> +	struct efa_ucontext *ucontext;
>>
>> Reverse xmas tree.
> ok
>>
>>>  	struct efa_dev *dev = to_edev(ibcq->device);
>>>  	struct efa_cq *cq = to_ecq(ibcq);
>>>
>>> @@ -894,20 +856,33 @@ void efa_destroy_cq(struct ib_cq *ibcq, struct
>> ib_udata *udata)
>>>  		  "Destroy cq[%d] virt[0x%p] freed: size[%lu], dma[%pad]\n",
>>>  		  cq->cq_idx, cq->cpu_addr, cq->size, &cq->dma_addr);
>>>
>>> +	ucontext = rdma_udata_to_drv_context(udata, struct efa_ucontext,
>>> +					     ibucontext);
>>>  	efa_destroy_cq_idx(dev, cq->cq_idx);
>>>  	dma_unmap_single(&dev->pdev->dev, cq->dma_addr, cq->size,
>>>  			 DMA_FROM_DEVICE);
>>> +	rdma_user_mmap_entry_remove(&ucontext->ibucontext,
>>> +				    cq->mmap_key);
>>
>> Entry removal should be first.
> Why ? removing can lead to freeing, why would we want that before unmapping ? 

Makes sense, thanks.

>>
>>>  }
>>>