RDMA/core: Optimize XRC target lookup

Replace the mutex with read write semaphore and use xarray instead of
linked list for XRC target QPs. This will give faster XRC target
lookup. In addition, when QP is closed, don't insert it back to the xarray
if the destroy command failed.

Link: https://lore.kernel.org/r/20200706122716.647338-4-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
index a9b99c3..b1b6cc2 100644 (file)
--- a/drivers/infiniband/core/verbs.c
+++ b/drivers/infiniband/core/verbs.c
@@ -1090,13 +1090,6 @@ static void __ib_shared_qp_event_handler(struct ib_event *event, void *context)
        spin_unlock_irqrestore(&qp->device->qp_open_list_lock, flags);
 }
 
-static void __ib_insert_xrcd_qp(struct ib_xrcd *xrcd, struct ib_qp *qp)
-{
-       mutex_lock(&xrcd->tgt_qp_mutex);
-       list_add(&qp->xrcd_list, &xrcd->tgt_qp_list);
-       mutex_unlock(&xrcd->tgt_qp_mutex);
-}
-
 static struct ib_qp *__ib_open_qp(struct ib_qp *real_qp,
                                  void (*event_handler)(struct ib_event *, void *),
                                  void *qp_context)
@@ -1139,16 +1132,15 @@ struct ib_qp *ib_open_qp(struct ib_xrcd *xrcd,
        if (qp_open_attr->qp_type != IB_QPT_XRC_TGT)
                return ERR_PTR(-EINVAL);
 
-       qp = ERR_PTR(-EINVAL);
-       mutex_lock(&xrcd->tgt_qp_mutex);
-       list_for_each_entry(real_qp, &xrcd->tgt_qp_list, xrcd_list) {
-               if (real_qp->qp_num == qp_open_attr->qp_num) {
-                       qp = __ib_open_qp(real_qp, qp_open_attr->event_handler,
-                                         qp_open_attr->qp_context);
-                       break;
-               }
+       down_read(&xrcd->tgt_qps_rwsem);
+       real_qp = xa_load(&xrcd->tgt_qps, qp_open_attr->qp_num);
+       if (!real_qp) {
+               up_read(&xrcd->tgt_qps_rwsem);
+               return ERR_PTR(-EINVAL);
        }
-       mutex_unlock(&xrcd->tgt_qp_mutex);
+       qp = __ib_open_qp(real_qp, qp_open_attr->event_handler,
+                         qp_open_attr->qp_context);
+       up_read(&xrcd->tgt_qps_rwsem);
        return qp;
 }
 EXPORT_SYMBOL(ib_open_qp);
@@ -1157,6 +1149,7 @@ static struct ib_qp *create_xrc_qp_user(struct ib_qp *qp,
                                        struct ib_qp_init_attr *qp_init_attr)
 {
        struct ib_qp *real_qp = qp;
+       int err;
 
        qp->event_handler = __ib_shared_qp_event_handler;
        qp->qp_context = qp;
@@ -1172,7 +1165,12 @@ static struct ib_qp *create_xrc_qp_user(struct ib_qp *qp,
        if (IS_ERR(qp))
                return qp;
 
-       __ib_insert_xrcd_qp(qp_init_attr->xrcd, real_qp);
+       err = xa_err(xa_store(&qp_init_attr->xrcd->tgt_qps, real_qp->qp_num,
+                             real_qp, GFP_KERNEL));
+       if (err) {
+               ib_close_qp(qp);
+               return ERR_PTR(err);
+       }
        return qp;
 }
 
@@ -1887,21 +1885,18 @@ static int __ib_destroy_shared_qp(struct ib_qp *qp)
 
        real_qp = qp->real_qp;
        xrcd = real_qp->xrcd;
-
-       mutex_lock(&xrcd->tgt_qp_mutex);
+       down_write(&xrcd->tgt_qps_rwsem);
        ib_close_qp(qp);
        if (atomic_read(&real_qp->usecnt) == 0)
-               list_del(&real_qp->xrcd_list);
+               xa_erase(&xrcd->tgt_qps, real_qp->qp_num);
        else
                real_qp = NULL;
-       mutex_unlock(&xrcd->tgt_qp_mutex);
+       up_write(&xrcd->tgt_qps_rwsem);
 
        if (real_qp) {
                ret = ib_destroy_qp(real_qp);
                if (!ret)
                        atomic_dec(&xrcd->usecnt);
-               else
-                       __ib_insert_xrcd_qp(xrcd, real_qp);
        }
 
        return 0;
@@ -2307,8 +2302,8 @@ struct ib_xrcd *ib_alloc_xrcd_user(struct ib_device *device,
                xrcd->device = device;
                xrcd->inode = inode;
                atomic_set(&xrcd->usecnt, 0);
-               mutex_init(&xrcd->tgt_qp_mutex);
-               INIT_LIST_HEAD(&xrcd->tgt_qp_list);
+               init_rwsem(&xrcd->tgt_qps_rwsem);
+               xa_init(&xrcd->tgt_qps);
        }
 
        return xrcd;
@@ -2322,20 +2317,10 @@ EXPORT_SYMBOL(ib_alloc_xrcd_user);
  */
 int ib_dealloc_xrcd_user(struct ib_xrcd *xrcd, struct ib_udata *udata)
 {
-       struct ib_qp *qp;
-       int ret;
-
        if (atomic_read(&xrcd->usecnt))
                return -EBUSY;
 
-       while (!list_empty(&xrcd->tgt_qp_list)) {
-               qp = list_entry(xrcd->tgt_qp_list.next, struct ib_qp, xrcd_list);
-               ret = ib_destroy_qp(qp);
-               if (ret)
-                       return ret;
-       }
-       mutex_destroy(&xrcd->tgt_qp_mutex);
-
+       WARN_ON(!xa_empty(&xrcd->tgt_qps));
        return xrcd->device->ops.dealloc_xrcd(xrcd, udata);
 }
 EXPORT_SYMBOL(ib_dealloc_xrcd_user);

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index db6f78c..20c8017 100644 (file)
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1567,9 +1567,8 @@ struct ib_xrcd {
        struct ib_device       *device;
        atomic_t                usecnt; /* count all exposed resources */
        struct inode           *inode;
-
-       struct mutex            tgt_qp_mutex;
-       struct list_head        tgt_qp_list;
+       struct rw_semaphore     tgt_qps_rwsem;
+       struct xarray           tgt_qps;
 };
 
 struct ib_ah {