IB/rxe: avoid putting a large struct rxe_qp on stack

A race condition fix added an rxe_qp structure to the stack in order
to be able to perform rollback in rxe_requester(), but the structure
is large enough to trigger the warning for possible stack overflow:

drivers/infiniband/sw/rxe/rxe_req.c: In function 'rxe_requester':
drivers/infiniband/sw/rxe/rxe_req.c:757:1: error: the frame size of 2064 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

This changes the rollback function to only save the psn inside
the qp, which is the only field we access in the rollback_qp
anyway.

Fixes: 3050b9985024 ("IB/rxe: Fix race condition between requester and completer")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/drivers/infiniband/sw/rxe/rxe_req.c b/drivers/infiniband/sw/rxe/rxe_req.c
index 832846b73ea0..205222909e53 100644
--- a/drivers/infiniband/sw/rxe/rxe_req.c
+++ b/drivers/infiniband/sw/rxe/rxe_req.c
@@ -548,23 +548,23 @@ static void update_wqe_psn(struct rxe_qp *qp,
 static void save_state(struct rxe_send_wqe *wqe,
                        struct rxe_qp *qp,
                        struct rxe_send_wqe *rollback_wqe,
-                       struct rxe_qp *rollback_qp)
+                       u32 *rollback_psn)
 {
         rollback_wqe->state     = wqe->state;
         rollback_wqe->first_psn = wqe->first_psn;
         rollback_wqe->last_psn  = wqe->last_psn;
-        rollback_qp->req.psn    = qp->req.psn;
+        *rollback_psn           = qp->req.psn;
 }
 
 static void rollback_state(struct rxe_send_wqe *wqe,
                            struct rxe_qp *qp,
                            struct rxe_send_wqe *rollback_wqe,
-                           struct rxe_qp *rollback_qp)
+                           u32 rollback_psn)
 {
         wqe->state     = rollback_wqe->state;
         wqe->first_psn = rollback_wqe->first_psn;
         wqe->last_psn  = rollback_wqe->last_psn;
-        qp->req.psn    = rollback_qp->req.psn;
+        qp->req.psn    = rollback_psn;
 }
 
 static void update_state(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
@@ -593,8 +593,8 @@ int rxe_requester(void *arg)
         int mtu;
         int opcode;
         int ret;
-        struct rxe_qp rollback_qp;
         struct rxe_send_wqe rollback_wqe;
+        u32 rollback_psn;
 
 next_wqe:
         if (unlikely(!qp->valid || qp->req.state == QP_STATE_ERROR))
@@ -718,7 +718,7 @@ next_wqe:
          * rxe_xmit_packet().
          * Otherwise, completer might initiate an unjustified retry flow.
          */
-        save_state(wqe, qp, &rollback_wqe, &rollback_qp);
+        save_state(wqe, qp, &rollback_wqe, &rollback_psn);
         update_wqe_state(qp, wqe, &pkt);
         update_wqe_psn(qp, wqe, &pkt, payload);
         ret = rxe_xmit_packet(to_rdev(qp->ibqp.device), qp, &pkt, skb);
@@ -726,7 +726,7 @@ next_wqe:
                 qp->need_req_skb = 1;
                 kfree_skb(skb);
 
-                rollback_state(wqe, qp, &rollback_wqe, &rollback_qp);
+                rollback_state(wqe, qp, &rollback_wqe, rollback_psn);
 
                 if (ret == -EAGAIN) {
                         rxe_run_task(&qp->req.task, 1);