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

[Leon Romanovsky <leon@kernel.org>]

On Tue, Nov 11, 2025 at 12:35:02PM +0900, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
> 
> 21 drivers/infiniband/sw/rxe/rxe_verbs.h:271:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> This helper creates a union between a flexible-array member (FAM) and a
> set of MEMBERS that would otherwise follow it.
> 
> This overlays the trailing MEMBER struct ib_sge sge[RXE_MAX_SGE]; onto
> the FAM struct rxe_recv_wqe::dma.sge, while keeping the FAM and the
> start of MEMBER aligned.
> 
> The static_assert() ensures this alignment remains, and it's
> intentionally placed inmediately after the related structure --no
> blank line in between.
> 
> Lastly, move the conflicting declaration struct rxe_resp_info resp;
> to the end of the corresponding structure.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>  drivers/infiniband/sw/rxe/rxe_verbs.h | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> 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;
> -
>  	/* Responder resources. It's a circular list where the oldest
>  	 * resource is dropped first.
>  	 */
> @@ -232,7 +226,15 @@ struct rxe_resp_info {
>  	unsigned int		res_head;
>  	unsigned int		res_tail;
>  	struct resp_res		*res;
> +
> +	/* SRQ only */
> +	/* Must be last as it ends in a flexible-array member. */
> +	TRAILING_OVERLAP(struct rxe_recv_wqe, wqe, dma.sge,
> +		struct ib_sge		sge[RXE_MAX_SGE];
> +	) srq_wqe;

Will this change be enough?

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
index fd48075810dd..9ab11421a585 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 +226,12 @@ struct rxe_resp_info {
        unsigned int            res_head;
        unsigned int            res_tail;
        struct resp_res         *res;
+
+       /* SRQ only */
+       struct {
+               struct ib_sge           sge[RXE_MAX_SGE];
+               struct rxe_recv_wqe     wqe;
+       } srq_wqe;
 };
 
 struct rxe_qp {
~