[PATCH v2 3/3] IB/core: Obtain subnet_prefix from cache in IB devices

[Anand Khoje]

ib_query_port() calls device->ops.query_port() to get the port
attributes. The method of querying is device driver specific.
The same function calls device->ops.query_gid() to get the GID and
extract the subnet_prefix (gid_prefix).

The GID and subnet_prefix are stored in a cache. But they do not get
read from the cache if the device is an Infiniband device. The
following change takes advantage of the cached subnet_prefix.
Testing with RDBMS has shown a significant improvement in performance
with this change.

The function ib_cache_is_initialised() is introduced because
ib_query_port() gets called early in the stage when the cache is not
built while reading port immutable property.

In that case, the default GID still gets read from HCA for IB link-
layer devices.

Fixes: fad61ad ("IB/core: Add subnet prefix to port info")
Signed-off-by: Anand Khoje <anand.a.khoje@xxxxxxxxxx>
Signed-off-by: Haakon Bugge <haakon.bugge@xxxxxxxxxx>
---
 drivers/infiniband/core/cache.c  | 7 ++++++-
 drivers/infiniband/core/device.c | 9 +++++++++
 include/rdma/ib_cache.h          | 6 ++++++
 include/rdma/ib_verbs.h          | 6 ++++++
 4 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
index b6700ad..724ac0e 100644
--- a/drivers/infiniband/core/cache.c
+++ b/drivers/infiniband/core/cache.c
@@ -1624,6 +1624,8 @@ int ib_cache_setup_one(struct ib_device *device)
 		err = ib_cache_update(device, p, true);
 		if (err)
 			return err;
+		set_bit(IB_PORT_CACHE_INITIALIZED,
+			&device->port_data[p].flags);
 	}
 
 	return 0;
@@ -1639,8 +1641,11 @@ void ib_cache_release_one(struct ib_device *device)
 	 * all the device's resources when the cache could no
 	 * longer be accessed.
 	 */
-	rdma_for_each_port (device, p)
+	rdma_for_each_port (device, p) {
+		clear_bit(IB_PORT_CACHE_INITIALIZED,
+			 &device->port_data[p].flags);
 		kfree(device->port_data[p].cache.pkey);
+	}
 
 	gid_table_release_one(device);
 }
diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index c2fa592..b3e20ac 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -2060,6 +2060,15 @@ static int __ib_query_port(struct ib_device *device,
 	    IB_LINK_LAYER_INFINIBAND)
 		return 0;
 
+	if (!ib_cache_is_initialised(device, port_num))
+		goto query_gid_from_device;
+
+	ib_get_cached_subnet_prefix(device, port_num,
+				    &port_attr->subnet_prefix);
+
+	return 0;
+
+query_gid_from_device:
 	err = device->ops.query_gid(device, port_num, 0, &gid);
 	if (err)
 		return err;
diff --git a/include/rdma/ib_cache.h b/include/rdma/ib_cache.h
index 226ae37..1526fc6 100644
--- a/include/rdma/ib_cache.h
+++ b/include/rdma/ib_cache.h
@@ -114,4 +114,10 @@ ssize_t rdma_query_gid_table(struct ib_device *device,
 			     struct ib_uverbs_gid_entry *entries,
 			     size_t max_entries);
 
+static inline bool ib_cache_is_initialised(struct ib_device *device,
+					  u8 port_num)
+{
+	return test_bit(IB_PORT_CACHE_INITIALIZED,
+			&device->port_data[port_num].flags);
+}
 #endif /* _IB_CACHE_H */
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 41cbec5..ad2a55e 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -2169,6 +2169,10 @@ struct ib_port_immutable {
 	u32                           max_mad_size;
 };
 
+enum ib_port_data_flags {
+	IB_PORT_CACHE_INITIALIZED = 1 << 0,
+};
+
 struct ib_port_data {
 	struct ib_device *ib_dev;
 
@@ -2178,6 +2182,8 @@ struct ib_port_data {
 
 	spinlock_t netdev_lock;
 
+	unsigned long flags;
+
 	struct list_head pkey_list;
 
 	struct ib_port_cache cache;
-- 
1.8.3.1