[PATCH 5.5 294/367] IB/mlx5: Fix outstanding_pi index for GSI qps

[Greg Kroah-Hartman]

From: Prabhath Sajeepa <psajeepa@xxxxxxxxxxxxxxx>

commit b5671afe5e39ed71e94eae788bacdcceec69db09 upstream.

Commit b0ffeb537f3a ("IB/mlx5: Fix iteration overrun in GSI qps") changed
the way outstanding WRs are tracked for the GSI QP. But the fix did not
cover the case when a call to ib_post_send() fails and updates index to
track outstanding.

Since the prior commmit outstanding_pi should not be bounded otherwise the
loop generate_completions() will fail.

Fixes: b0ffeb537f3a ("IB/mlx5: Fix iteration overrun in GSI qps")
Link: https://lore.kernel.org/r/1576195889-23527-1-git-send-email-psajeepa@xxxxxxxxxxxxxxx
Signed-off-by: Prabhath Sajeepa <psajeepa@xxxxxxxxxxxxxxx>
Acked-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/hw/mlx5/gsi.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/infiniband/hw/mlx5/gsi.c
+++ b/drivers/infiniband/hw/mlx5/gsi.c
@@ -507,8 +507,7 @@ int mlx5_ib_gsi_post_send(struct ib_qp *
 		ret = ib_post_send(tx_qp, &cur_wr.wr, bad_wr);
 		if (ret) {
 			/* Undo the effect of adding the outstanding wr */
-			gsi->outstanding_pi = (gsi->outstanding_pi - 1) %
-					      gsi->cap.max_send_wr;
+			gsi->outstanding_pi--;
 			goto err;
 		}
 		spin_unlock_irqrestore(&gsi->lock, flags);