[PATCH rdma-next 3/6] RDMA/core: Add rdma_restrack_begin/abort/commit_del() operations

[Edward Srouji <edwards@nvidia.com>]

From: Patrisious Haddad <phaddad@nvidia.com>

Add rdma_restrack_abort_del(), rdma_restrack_begin_del() and
rdma_restrack_commit_del() functions to allow deleting a resource from
the xarray to effectively prevent future access to it and wait for all
current users to finish while preserving its index in the xarray to
allow to re-insert it if needed with guaranteed success.

This is a preparatory change for subsequent patches in the series
which will use these functions to fix the cleanup flow.

Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
---
 drivers/infiniband/core/restrack.c | 120 +++++++++++++++++++++++++++++++++----
 drivers/infiniband/core/restrack.h |   3 +
 2 files changed, 112 insertions(+), 11 deletions(-)

diff --git a/drivers/infiniband/core/restrack.c b/drivers/infiniband/core/restrack.c
index ac3688952cabbff1ebb899bacb78421f2515231b..97c8991081a49ff4f74d65c6c1bd8ca647aa72d1 100644
--- a/drivers/infiniband/core/restrack.c
+++ b/drivers/infiniband/core/restrack.c
@@ -71,6 +71,8 @@ int rdma_restrack_count(struct ib_device *dev, enum rdma_restrack_type type,
 
 	xa_lock(&rt->xa);
 	xas_for_each(&xas, e, U32_MAX) {
+		if (xa_is_zero(e))
+			continue;
 		if (xa_get_mark(&rt->xa, e->id, RESTRACK_DD) && !show_details)
 			continue;
 		cnt++;
@@ -127,6 +129,16 @@ static void rdma_restrack_attach_task(struct rdma_restrack_entry *res,
 	res->user = true;
 }
 
+static struct rdma_restrack_root *res_to_rt(struct rdma_restrack_entry *res)
+{
+	struct ib_device *dev = res_to_dev(res);
+
+	if (WARN_ON(!dev))
+		return NULL;
+
+	return &dev->res[res->type];
+}
+
 /**
  * rdma_restrack_set_name() - set the task for this resource
  * @res:  resource entry
@@ -180,17 +192,15 @@ EXPORT_SYMBOL(rdma_restrack_new);
  */
 void rdma_restrack_add(struct rdma_restrack_entry *res)
 {
-	struct ib_device *dev = res_to_dev(res);
 	struct rdma_restrack_root *rt;
 	int ret = 0;
 
-	if (!dev)
-		return;
-
 	if (res->no_track)
 		goto out;
 
-	rt = &dev->res[res->type];
+	rt = res_to_rt(res);
+	if (!rt)
+		return;
 
 	if (res->type == RDMA_RESTRACK_QP) {
 		/* Special case to ensure that LQPN points to right QP */
@@ -227,6 +237,37 @@ void rdma_restrack_add(struct rdma_restrack_entry *res)
 }
 EXPORT_SYMBOL(rdma_restrack_add);
 
+/**
+ * rdma_restrack_abort_del() - readd object to the resource tracking database
+ * it can only be used after rdma_restrack_begin_del().
+ * @res:  resource entry
+ */
+void rdma_restrack_abort_del(struct rdma_restrack_entry *res)
+{
+	struct rdma_restrack_entry *old;
+	struct rdma_restrack_root *rt;
+
+	if (!res->valid)
+		return;
+
+	if (res->no_track) {
+		rdma_restrack_new(res, res->type);
+		return;
+	}
+
+	rt = res_to_rt(res);
+	if (!rt)
+		return;
+
+	rdma_restrack_new(res, res->type);
+	old = xa_cmpxchg(&rt->xa, res->id, XA_ZERO_ENTRY, res, 0);
+	/* The only way this can fail if someone called this function
+	 * without first calling rdma_restrack_begin_del().
+	 */
+	WARN_ON(old);
+}
+EXPORT_SYMBOL(rdma_restrack_abort_del);
+
 int __must_check rdma_restrack_get(struct rdma_restrack_entry *res)
 {
 	return kref_get_unless_zero(&res->kref);
@@ -263,7 +304,7 @@ static void restrack_release(struct kref *kref)
 	struct rdma_restrack_entry *res;
 
 	res = container_of(kref, struct rdma_restrack_entry, kref);
-	if (res->task) {
+	if (res->task && !res->valid) {
 		put_task_struct(res->task);
 		res->task = NULL;
 	}
@@ -284,7 +325,6 @@ void rdma_restrack_del(struct rdma_restrack_entry *res)
 {
 	struct rdma_restrack_entry *old;
 	struct rdma_restrack_root *rt;
-	struct ib_device *dev;
 
 	if (!res->valid) {
 		if (res->task) {
@@ -297,12 +337,10 @@ void rdma_restrack_del(struct rdma_restrack_entry *res)
 	if (res->no_track)
 		goto out;
 
-	dev = res_to_dev(res);
-	if (WARN_ON(!dev))
+	rt = res_to_rt(res);
+	if (!rt)
 		return;
 
-	rt = &dev->res[res->type];
-
 	old = xa_erase(&rt->xa, res->id);
 	WARN_ON(old != res);
 
@@ -310,5 +348,65 @@ void rdma_restrack_del(struct rdma_restrack_entry *res)
 	res->valid = false;
 	rdma_restrack_put(res);
 	wait_for_completion(&res->comp);
+	if (res->task) {
+		put_task_struct(res->task);
+		res->task = NULL;
+	}
 }
 EXPORT_SYMBOL(rdma_restrack_del);
+
+/**
+ * rdma_restrack_begin_del() - invalidate the object from the resource tracking
+ * database but preserve its index in the array.
+ * @res:  resource entry
+ */
+void rdma_restrack_begin_del(struct rdma_restrack_entry *res)
+{
+	struct rdma_restrack_entry *old;
+	struct rdma_restrack_root *rt;
+
+	if (!res->valid)
+		return;
+
+	if (res->no_track)
+		goto out;
+
+	rt = res_to_rt(res);
+	if (!rt)
+		return;
+
+	old = xa_cmpxchg(&rt->xa, res->id, res, XA_ZERO_ENTRY, 0);
+	WARN_ON(old != res);
+
+out:
+	rdma_restrack_put(res);
+	wait_for_completion(&res->comp);
+}
+EXPORT_SYMBOL(rdma_restrack_begin_del);
+
+/**
+ * rdma_restrack_commit_del() - delete object from the resource tracking
+ * database and free the task.
+ * @res:  resource entry
+ */
+void rdma_restrack_commit_del(struct rdma_restrack_entry *res)
+{
+	struct rdma_restrack_root *rt;
+
+	if (!res->valid || res->no_track)
+		goto out;
+
+	rt = res_to_rt(res);
+	if (!rt)
+		return;
+
+	xa_erase(&rt->xa, res->id);
+
+out:
+	res->valid = false;
+	if (res->task) {
+		put_task_struct(res->task);
+		res->task = NULL;
+	}
+}
+EXPORT_SYMBOL(rdma_restrack_commit_del);
diff --git a/drivers/infiniband/core/restrack.h b/drivers/infiniband/core/restrack.h
index 6a04fc41f738010a90d96f88dbcc88bc36d3a289..45f2f06825f402324304113014fa90da03ec6f88 100644
--- a/drivers/infiniband/core/restrack.h
+++ b/drivers/infiniband/core/restrack.h
@@ -26,7 +26,10 @@ struct rdma_restrack_root {
 int rdma_restrack_init(struct ib_device *dev);
 void rdma_restrack_clean(struct ib_device *dev);
 void rdma_restrack_add(struct rdma_restrack_entry *res);
+void rdma_restrack_abort_del(struct rdma_restrack_entry *res);
 void rdma_restrack_del(struct rdma_restrack_entry *res);
+void rdma_restrack_begin_del(struct rdma_restrack_entry *res);
+void rdma_restrack_commit_del(struct rdma_restrack_entry *res);
 void rdma_restrack_new(struct rdma_restrack_entry *res,
 		       enum rdma_restrack_type type);
 void rdma_restrack_set_name(struct rdma_restrack_entry *res,

-- 
2.49.0