Re: [PATCH][next] RDMA/rxe: Avoid -Wflex-array-member-not-at-end warnings

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2025/12/2 10:13, Jason Gunthorpe 写道:
> On Tue, Nov 11, 2025 at 12:35:02PM +0900, Gustavo A. R. Silva wrote:
>> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
>> index fd48075810dd..6498d61e8956 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_verbs.h
>> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h
>> @@ -219,12 +219,6 @@ struct rxe_resp_info {
>>   	u32			rkey;
>>   	u32			length;
>>   
>> -	/* SRQ only */
>> -	struct {
>> -		struct rxe_recv_wqe	wqe;
>> -		struct ib_sge		sge[RXE_MAX_SGE];
>> -	} srq_wqe;
> 
> I think this existing is just a mess, can we fix it properly?
> 
> What this code wants to do is to have rxe_resp_info allocate a
> rxe_recv_wqe and have a maximum size of its flex array pre-allocated.
> 
> Probably like this, though maybe we need a FLEX version of the
> INIT_RDMA_OBJ_SIZE macro to make it safer.
> 
> Zhu, this seems like a good thing for you to look at?
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 38d8c408320f11..189eaa59a5fb14 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -1524,7 +1524,8 @@ static const struct ib_device_ops rxe_dev_ops = {
>   	INIT_RDMA_OBJ_SIZE(ib_ah, rxe_ah, ibah),
>   	INIT_RDMA_OBJ_SIZE(ib_cq, rxe_cq, ibcq),
>   	INIT_RDMA_OBJ_SIZE(ib_pd, rxe_pd, ibpd),
> -	INIT_RDMA_OBJ_SIZE(ib_qp, rxe_qp, ibqp),
> +	/* For resp.srq_wqe.dma.sge */
> +	INIT_RDMA_OBJ_SIZE(ib_qp, rxe_qp, ibqp) + RXE_MAX_SGE*sizeof(struct ib_sge),
>   	INIT_RDMA_OBJ_SIZE(ib_srq, rxe_srq, ibsrq),
>   	INIT_RDMA_OBJ_SIZE(ib_ucontext, rxe_ucontext, ibuc),
>   	INIT_RDMA_OBJ_SIZE(ib_mw, rxe_mw, ibmw),
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
> index fd48075810dd10..dda741ec3ac701 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.h
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h
> @@ -219,12 +219,6 @@ struct rxe_resp_info {
>   	u32			rkey;
>   	u32			length;
>   
> -	/* SRQ only */
> -	struct {
> -		struct rxe_recv_wqe	wqe;
> -		struct ib_sge		sge[RXE_MAX_SGE];
> -	} srq_wqe;
> -
>   	/* Responder resources. It's a circular list where the oldest
>   	 * resource is dropped first.
>   	 */
> @@ -232,6 +226,9 @@ struct rxe_resp_info {
>   	unsigned int		res_head;
>   	unsigned int		res_tail;
>   	struct resp_res		*res;
> +
> +	/* SRQ only. srq_wqe.dma.sge is a flex array */
> +	struct rxe_recv_wqe srq_wqe;

drivers/infiniband/sw/rxe/rxe_resp.c: In function get_srq_wqe:
drivers/infiniband/sw/rxe/rxe_resp.c:289:41: error: struct rxe_recv_wqe 
has no member named wqe
   289 |         qp->resp.wqe = &qp->resp.srq_wqe.wqe;
       |                                         ^

struct {
	struct rxe_recv_wqe	wqe;
	struct ib_sge		sge[RXE_MAX_SGE];
} srq_wqe;

IMO, it is better to move this struct to the end of the struct 
rxe_resp_info.

Yanjun.Zhu

>   };
>   
>   struct rxe_qp {
> @@ -269,7 +266,6 @@ struct rxe_qp {
>   
>   	struct rxe_req_info	req;
>   	struct rxe_comp_info	comp;
> -	struct rxe_resp_info	resp;
>   
>   	atomic_t		ssn;
>   	atomic_t		skb_out;
> @@ -289,6 +285,7 @@ struct rxe_qp {
>   	spinlock_t		state_lock; /* guard requester and completer */
>   
>   	struct execute_work	cleanup_work;
> +	struct rxe_resp_info	resp;
>   };
>   
>   enum {