[PATCH 4/5 try2] ib/ehca: check idr_find() return value

[Alexander Schmidt <alexs@linux.vnet.ibm.com>]

The idr_find() function may fail when trying to get the QP that is associated
with a CQE, e.g. when a QP has been destroyed between the generation of a CQE
and the poll request for it. In consequence, the return value of idr_find()
must be checked and the CQE must be discarded when the QP cannot be found.

Signed-off-by: Alexander Schmidt <alexs@linux.vnet.ibm.com>
---
 drivers/infiniband/hw/ehca/ehca_reqs.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- infiniband.git.orig/drivers/infiniband/hw/ehca/ehca_reqs.c
+++ infiniband.git/drivers/infiniband/hw/ehca/ehca_reqs.c
@@ -680,8 +680,10 @@ repoll:
 
 	read_lock(&ehca_qp_idr_lock);
 	my_qp = idr_find(&ehca_qp_idr, cqe->qp_token);
-	wc->qp = &my_qp->ib_qp;
 	read_unlock(&ehca_qp_idr_lock);
+	if (!my_qp)
+		goto repoll;
+	wc->qp = &my_qp->ib_qp;
 
 	wc->byte_len = cqe->nr_bytes_transferred;
 	wc->pkey_index = cqe->pkey_index;