Re: [PATCH rdma-core RESEND] providers/rxe: Replace '%' with '&' in check_qp_queue_full()

[Leon Romanovsky <leon@kernel.org>]

On Tue, Jan 11, 2022 at 09:19:46AM +0000, yangx.jy@fujitsu.com wrote:
> On 2022/1/11 14:11, Leon Romanovsky wrote:
> > On Tue, Jan 11, 2022 at 10:24:04AM +0800, Xiao Yang wrote:
> >> The expression "cons == ((qp->cur_index + 1) % q->index_mask)" mistakenly
> >> assumes the queue is full when the number of entires is equal to "maximum - 1"
> >> (maximum is correct).
> >>
> >> For example:
> >> If cons and qp->cur_index are 0 and q->index_mask is 1, check_qp_queue_full()
> >> reports ENOSPC.
> >>
> >> Fixes: 1a894ca10105 ("Providers/rxe: Implement ibv_create_qp_ex verb")
> >> Signed-off-by: Xiao Yang<yangx.jy@fujitsu.com>
> >> ---
> >>   providers/rxe/rxe_queue.h | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/providers/rxe/rxe_queue.h b/providers/rxe/rxe_queue.h
> >> index 6de8140c..708e76ac 100644
> >> --- a/providers/rxe/rxe_queue.h
> >> +++ b/providers/rxe/rxe_queue.h
> >> @@ -205,7 +205,7 @@ static inline int check_qp_queue_full(struct rxe_qp *qp)
> >>   	if (qp->err)
> >>   		goto err;
> >>
> >> -	if (cons == ((qp->cur_index + 1) % q->index_mask))
> >> +	if (cons == ((qp->cur_index + 1)&  q->index_mask))
> > Please reuse queue_full().
> Hi Leon,
> 
> qp->cur_index and qp->err are introduced for new ibv_wr_* APIs and I am 
> not sure if check_qp_queue_full() can be replaced with queue_full().
> 
> Bob, do you have any suggestion?


diff --git a/providers/rxe/rxe_queue.h b/providers/rxe/rxe_queue.h
index 6de8140c..83eb4a5f 100644
--- a/providers/rxe/rxe_queue.h
+++ b/providers/rxe/rxe_queue.h
@@ -198,14 +198,11 @@ static inline void advance_qp_cur_index(struct rxe_qp *qp)
 static inline int check_qp_queue_full(struct rxe_qp *qp)
 {
        struct rxe_queue_buf *q = qp->sq.queue;
-       uint32_t cons;
-
-       cons = atomic_load_explicit(consumer(q), memory_order_acquire);
 
        if (qp->err)
                goto err;
 
-       if (cons == ((qp->cur_index + 1) % q->index_mask))
+       if (queue_full(q))
                qp->err = ENOSPC;
 err:
        return qp->err;
(END)


> 
> Best Regards,
> Xiao Yang
> > Thanks
> >
> >>   		qp->err = ENOSPC;
> >>   err:
> >>   	return qp->err;
> >> -- 
> >> 2.25.1
> >>
> >>
> >>