In the same manner that we don't allow to destroy a PD, CQ, etc if
there are open QPs that relate to them, don't let one destory a QP
if there are active attachment/s of it to multicast groups. Use the
existing usecnt field of struct ib_qp which was added by commit
0e0ec7e "RDMA/core: Export ib_open_qp() to share XRC TGT QPs".

Signed-off-by: Or Gerlitz <[email protected]>
---
 drivers/infiniband/core/verbs.c |   14 ++++++++++++--
 include/rdma/ib_verbs.h         |    2 +-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
index 140f9a5..30f199e 100644
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -1184,23 +1184,33 @@ EXPORT_SYMBOL(ib_dealloc_fmr);
 
 int ib_attach_mcast(struct ib_qp *qp, union ib_gid *gid, u16 lid)
 {
+       int ret;
+
        if (!qp->device->attach_mcast)
                return -ENOSYS;
        if (gid->raw[0] != 0xff || qp->qp_type != IB_QPT_UD)
                return -EINVAL;
 
-       return qp->device->attach_mcast(qp, gid, lid);
+       ret = qp->device->attach_mcast(qp, gid, lid);
+       if (!ret)
+               atomic_inc(&qp->usecnt);
+       return ret;
 }
 EXPORT_SYMBOL(ib_attach_mcast);
 
 int ib_detach_mcast(struct ib_qp *qp, union ib_gid *gid, u16 lid)
 {
+       int ret;
+
        if (!qp->device->detach_mcast)
                return -ENOSYS;
        if (gid->raw[0] != 0xff || qp->qp_type != IB_QPT_UD)
                return -EINVAL;
 
-       return qp->device->detach_mcast(qp, gid, lid);
+       ret = qp->device->detach_mcast(qp, gid, lid);
+       if (!ret)
+               atomic_dec(&qp->usecnt);
+       return ret;
 }
 EXPORT_SYMBOL(ib_detach_mcast);
 
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index a3fa323..07996af 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -964,7 +964,7 @@ struct ib_qp {
        struct ib_srq          *srq;
        struct ib_xrcd         *xrcd; /* XRC TGT QPs only */
        struct list_head        xrcd_list;
-       atomic_t                usecnt; /* count times opened */
+       atomic_t                usecnt; /* count times opened, mcast attaches */
        struct list_head        open_list;
        struct ib_qp           *real_qp;
        struct ib_uobject      *uobject;
-- 
1.7.1

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