IB/rdmavt: Add QP iterator API for QPs

There are currently 3 spots in the qib and hfi1 driver that have
knowledge of the internal QP hash list that should only be in
scope to rdmavt QP code.

Add an iterator API for processing all QPs to hide the
nature of the RCU hashlist.

The API consists of:
- rvt_qp_iter_init()
  * For iterating QPs one at a time for seq_file semantics
- rvt_qp_iter_next()
  * For iterating QPs one at a time for seq_file semantics
- rvt_qp_iter()
  * For iterating all QPs

The first two are used for things like seq_file prints.

The last is for code that just needs to iterate all QPs
in the system.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/sw/rdmavt/qp.c

@@ -2069,3 +2069,147 @@ enum hrtimer_restart rvt_rc_rnr_retry(struct hrtimer *t)
 	return HRTIMER_NORESTART;
 }
 EXPORT_SYMBOL(rvt_rc_rnr_retry);
+
+/**
+ * rvt_qp_iter_init - initial for QP iteration
+ * @rdi - rvt devinfo
+ * @v - u64 value
+ *
+ * This returns an iterator suitable for iterating QPs
+ * in the system.
+ *
+ * The @cb is a user defined callback and @v is a 64
+ * bit value passed to and relevant for processing in the
+ * @cb.  An example use case would be to alter QP processing
+ * based on criteria not part of the rvt_qp.
+ *
+ * Use cases that require memory allocation to succeed
+ * must preallocate appropriately.
+ *
+ * Return: a pointer to an rvt_qp_iter or NULL
+ */
+struct rvt_qp_iter *rvt_qp_iter_init(struct rvt_dev_info *rdi,
+				     u64 v,
+				     void (*cb)(struct rvt_qp *qp, u64 v))
+{
+	struct rvt_qp_iter *i;
+
+	i = kzalloc(sizeof(*i), GFP_KERNEL);
+	if (!i)
+		return NULL;
+
+	i->rdi = rdi;
+	/* number of special QPs (SMI/GSI) for device */
+	i->specials = rdi->ibdev.phys_port_cnt * 2;
+	i->v = v;
+	i->cb = cb;
+
+	return i;
+}
+EXPORT_SYMBOL(rvt_qp_iter_init);
+
+/**
+ * rvt_qp_iter_next - return the next QP in iter
+ * @iter - the iterator
+ *
+ * Fine grained QP iterator suitable for use
+ * with debugfs seq_file mechanisms.
+ *
+ * Updates iter->qp with the current QP when the return
+ * value is 0.
+ *
+ * Return: 0 - iter->qp is valid 1 - no more QPs
+ */
+int rvt_qp_iter_next(struct rvt_qp_iter *iter)
+	__must_hold(RCU)
+{
+	int n = iter->n;
+	int ret = 1;
+	struct rvt_qp *pqp = iter->qp;
+	struct rvt_qp *qp;
+	struct rvt_dev_info *rdi = iter->rdi;
+
+	/*
+	 * The approach is to consider the special qps
+	 * as additional table entries before the
+	 * real hash table.  Since the qp code sets
+	 * the qp->next hash link to NULL, this works just fine.
+	 *
+	 * iter->specials is 2 * # ports
+	 *
+	 * n = 0..iter->specials is the special qp indices
+	 *
+	 * n = iter->specials..rdi->qp_dev->qp_table_size+iter->specials are
+	 * the potential hash bucket entries
+	 *
+	 */
+	for (; n <  rdi->qp_dev->qp_table_size + iter->specials; n++) {
+		if (pqp) {
+			qp = rcu_dereference(pqp->next);
+		} else {
+			if (n < iter->specials) {
+				struct rvt_ibport *rvp;
+				int pidx;
+
+				pidx = n % rdi->ibdev.phys_port_cnt;
+				rvp = rdi->ports[pidx];
+				qp = rcu_dereference(rvp->qp[n & 1]);
+			} else {
+				qp = rcu_dereference(
+					rdi->qp_dev->qp_table[
+						(n - iter->specials)]);
+			}
+		}
+		pqp = qp;
+		if (qp) {
+			iter->qp = qp;
+			iter->n = n;
+			return 0;
+		}
+	}
+	return ret;
+}
+EXPORT_SYMBOL(rvt_qp_iter_next);
+
+/**
+ * rvt_qp_iter - iterate all QPs
+ * @rdi - rvt devinfo
+ * @v - a 64 bit value
+ * @cb - a callback
+ *
+ * This provides a way for iterating all QPs.
+ *
+ * The @cb is a user defined callback and @v is a 64
+ * bit value passed to and relevant for processing in the
+ * cb.  An example use case would be to alter QP processing
+ * based on criteria not part of the rvt_qp.
+ *
+ * The code has an internal iterator to simplify
+ * non seq_file use cases.
+ */
+void rvt_qp_iter(struct rvt_dev_info *rdi,
+		 u64 v,
+		 void (*cb)(struct rvt_qp *qp, u64 v))
+{
+	int ret;
+	struct rvt_qp_iter i = {
+		.rdi = rdi,
+		.specials = rdi->ibdev.phys_port_cnt * 2,
+		.v = v,
+		.cb = cb
+	};
+
+	rcu_read_lock();
+	do {
+		ret = rvt_qp_iter_next(&i);
+		if (!ret) {
+			rvt_get_qp(i.qp);
+			rcu_read_unlock();
+			i.cb(i.qp, i.v);
+			rcu_read_lock();
+			rvt_put_qp(i.qp);
+		}
+	} while (!ret);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL(rvt_qp_iter);

include/rdma/rdmavt_qp.h

@@ -673,4 +673,33 @@ void rvt_del_timers_sync(struct rvt_qp *qp);
 void rvt_stop_rc_timers(struct rvt_qp *qp);
 void rvt_add_retry_timer(struct rvt_qp *qp);
 
+/**
+ * struct rvt_qp_iter - the iterator for QPs
+ * @qp - the current QP
+ *
+ * This structure defines the current iterator
+ * state for sequenced access to all QPs relative
+ * to an rvt_dev_info.
+ */
+struct rvt_qp_iter {
+	struct rvt_qp *qp;
+	/* private: backpointer */
+	struct rvt_dev_info *rdi;
+	/* private: callback routine */
+	void (*cb)(struct rvt_qp *qp, u64 v);
+	/* private: for arg to callback routine */
+	u64 v;
+	/* private: number of SMI,GSI QPs for device */
+	int specials;
+	/* private: current iterator index */
+	int n;
+};
+
+struct rvt_qp_iter *rvt_qp_iter_init(struct rvt_dev_info *rdi,
+				     u64 v,
+				     void (*cb)(struct rvt_qp *qp, u64 v));
+int rvt_qp_iter_next(struct rvt_qp_iter *iter);
+void rvt_qp_iter(struct rvt_dev_info *rdi,
+		 u64 v,
+		 void (*cb)(struct rvt_qp *qp, u64 v));
 #endif          /* DEF_RDMAVT_INCQP_H */