+/*
+ * The ib_uobject locking scheme is as follows:
+ *
+ * - ib_uverbs_idr_lock protects the uverbs idrs themselves, so it
+ * needs to be held during all idr operations. When an object is
+ * looked up, a reference must be taken on the object's kref before
+ * dropping this lock.
+ *
+ * - Each object also has an rwsem. This rwsem must be held for
+ * reading while an operation that uses the object is performed.
+ * For example, while registering an MR, the associated PD's
+ * uobject.mutex must be held for reading. The rwsem must be held
+ * for writing while initializing or destroying an object.
+ *
+ * - In addition, each object has a "live" flag. If this flag is not
+ * set, then lookups of the object will fail even if it is found in
+ * the idr. This handles a reader that blocks and does not acquire
+ * the rwsem until after the object is destroyed. The destroy
+ * operation will set the live flag to 0 and then drop the rwsem;
+ * this will allow the reader to acquire the rwsem, see that the
+ * live flag is 0, and then drop the rwsem and its reference to
+ * object. The underlying storage will not be freed until the last
+ * reference to the object is dropped.
+ */
+
+static void init_uobj(struct ib_uobject *uobj, u64 user_handle,
+ struct ib_ucontext *context, struct lock_class_key *key)
+{
+ uobj->user_handle = user_handle;
+ uobj->context = context;
+ kref_init(&uobj->ref);
+ init_rwsem(&uobj->mutex);
+ lockdep_set_class(&uobj->mutex, key);
+ uobj->live = 0;
+}
+
+static void release_uobj(struct kref *kref)
+{
+ kfree(container_of(kref, struct ib_uobject, ref));
+}
+
+static void put_uobj(struct ib_uobject *uobj)
+{
+ kref_put(&uobj->ref, release_uobj);
+}
+
+static void put_uobj_read(struct ib_uobject *uobj)
+{
+ up_read(&uobj->mutex);
+ put_uobj(uobj);
+}
+
+static void put_uobj_write(struct ib_uobject *uobj)
+{
+ up_write(&uobj->mutex);
+ put_uobj(uobj);
+}
+
+static int idr_add_uobj(struct idr *idr, struct ib_uobject *uobj)
+{
+ int ret;
+
+retry:
+ if (!idr_pre_get(idr, GFP_KERNEL))
+ return -ENOMEM;
+
+ spin_lock(&ib_uverbs_idr_lock);
+ ret = idr_get_new(idr, uobj, &uobj->id);
+ spin_unlock(&ib_uverbs_idr_lock);
+
+ if (ret == -EAGAIN)
+ goto retry;
+
+ return ret;
+}
+
+void idr_remove_uobj(struct idr *idr, struct ib_uobject *uobj)
+{
+ spin_lock(&ib_uverbs_idr_lock);
+ idr_remove(idr, uobj->id);
+ spin_unlock(&ib_uverbs_idr_lock);
+}
+
+static struct ib_uobject *__idr_get_uobj(struct idr *idr, int id,
+ struct ib_ucontext *context)
+{
+ struct ib_uobject *uobj;
+
+ spin_lock(&ib_uverbs_idr_lock);
+ uobj = idr_find(idr, id);
+ if (uobj)
+ kref_get(&uobj->ref);
+ spin_unlock(&ib_uverbs_idr_lock);
+
+ return uobj;
+}
+
+static struct ib_uobject *idr_read_uobj(struct idr *idr, int id,
+ struct ib_ucontext *context, int nested)
+{
+ struct ib_uobject *uobj;
+
+ uobj = __idr_get_uobj(idr, id, context);
+ if (!uobj)
+ return NULL;
+
+ if (nested)
+ down_read_nested(&uobj->mutex, SINGLE_DEPTH_NESTING);
+ else
+ down_read(&uobj->mutex);
+ if (!uobj->live) {
+ put_uobj_read(uobj);
+ return NULL;
+ }
+
+ return uobj;
+}
+
+static struct ib_uobject *idr_write_uobj(struct idr *idr, int id,
+ struct ib_ucontext *context)
+{
+ struct ib_uobject *uobj;
+
+ uobj = __idr_get_uobj(idr, id, context);
+ if (!uobj)
+ return NULL;
+
+ down_write(&uobj->mutex);
+ if (!uobj->live) {
+ put_uobj_write(uobj);
+ return NULL;
+ }
+
+ return uobj;
+}
+
+static void *idr_read_obj(struct idr *idr, int id, struct ib_ucontext *context,
+ int nested)
+{
+ struct ib_uobject *uobj;
+
+ uobj = idr_read_uobj(idr, id, context, nested);
+ return uobj ? uobj->object : NULL;
+}
+
+static struct ib_pd *idr_read_pd(int pd_handle, struct ib_ucontext *context)
+{
+ return idr_read_obj(&ib_uverbs_pd_idr, pd_handle, context, 0);
+}
+
+static void put_pd_read(struct ib_pd *pd)
+{
+ put_uobj_read(pd->uobject);
+}
+
+static struct ib_cq *idr_read_cq(int cq_handle, struct ib_ucontext *context, int nested)
+{
+ return idr_read_obj(&ib_uverbs_cq_idr, cq_handle, context, nested);
+}
+
+static void put_cq_read(struct ib_cq *cq)
+{
+ put_uobj_read(cq->uobject);
+}
+
+static struct ib_ah *idr_read_ah(int ah_handle, struct ib_ucontext *context)
+{
+ return idr_read_obj(&ib_uverbs_ah_idr, ah_handle, context, 0);
+}
+
+static void put_ah_read(struct ib_ah *ah)
+{
+ put_uobj_read(ah->uobject);
+}
+
+static struct ib_qp *idr_read_qp(int qp_handle, struct ib_ucontext *context)
+{
+ return idr_read_obj(&ib_uverbs_qp_idr, qp_handle, context, 0);
+}
+
+static void put_qp_read(struct ib_qp *qp)
+{
+ put_uobj_read(qp->uobject);
+}
+
+static struct ib_srq *idr_read_srq(int srq_handle, struct ib_ucontext *context)
+{
+ return idr_read_obj(&ib_uverbs_srq_idr, srq_handle, context, 0);
+}
+
+static void put_srq_read(struct ib_srq *srq)
+{
+ put_uobj_read(srq->uobject);
+}
+