From: Huy Nguyen <huyn@mellanox.com>
Date: Mon, 8 Jan 2018 12:15:37 +0200
Subject: IB/core: Remove the locking for character device bitmaps
Patch-mainline: v4.16-rc1
Git-commit: 008b656f429824a1987f28150d66eaf8f26d58a1
References: bsc#1103992 FATE#326009

Remove the locks that protect character device bitmaps of
uverbs, umad and issm.

The character device bitmaps are accessed in "client->add" and
"client->remove" calls from ib_register_device and ib_unregister_device
respectively. These calls are already protected by the "device_mutex"
mutex. Thus, the spinlocks are not needed.

Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/core/user_mad.c    |    5 -----
 drivers/infiniband/core/uverbs_main.c |    5 -----
 2 files changed, 10 deletions(-)

--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -129,7 +129,6 @@ static struct class *umad_class;
 
 static const dev_t base_dev = MKDEV(IB_UMAD_MAJOR, IB_UMAD_MINOR_BASE);
 
-static DEFINE_SPINLOCK(port_lock);
 static DECLARE_BITMAP(dev_map, IB_UMAD_MAX_PORTS);
 
 static void ib_umad_add_one(struct ib_device *device);
@@ -1172,15 +1171,12 @@ static int ib_umad_init_port(struct ib_d
 	int devnum;
 	dev_t base;
 
-	spin_lock(&port_lock);
 	devnum = find_first_zero_bit(dev_map, IB_UMAD_MAX_PORTS);
 	if (devnum >= IB_UMAD_MAX_PORTS) {
-		spin_unlock(&port_lock);
 		devnum = find_overflow_devnum(device);
 		if (devnum < 0)
 			return -1;
 
-		spin_lock(&port_lock);
 		port->dev_num = devnum + IB_UMAD_MAX_PORTS;
 		base = devnum + overflow_maj;
 		set_bit(devnum, overflow_map);
@@ -1189,7 +1185,6 @@ static int ib_umad_init_port(struct ib_d
 		base = devnum + base_dev;
 		set_bit(devnum, dev_map);
 	}
-	spin_unlock(&port_lock);
 
 	port->ib_dev   = device;
 	port->port_num = port_num;
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -69,7 +69,6 @@ enum {
 
 static struct class *uverbs_class;
 
-static DEFINE_SPINLOCK(map_lock);
 static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
 
 static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
@@ -1062,15 +1061,12 @@ static void ib_uverbs_add_one(struct ib_
 	INIT_LIST_HEAD(&uverbs_dev->uverbs_file_list);
 	INIT_LIST_HEAD(&uverbs_dev->uverbs_events_file_list);
 
-	spin_lock(&map_lock);
 	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
 	if (devnum >= IB_UVERBS_MAX_DEVICES) {
-		spin_unlock(&map_lock);
 		devnum = find_overflow_devnum();
 		if (devnum < 0)
 			goto err;
 
-		spin_lock(&map_lock);
 		uverbs_dev->devnum = devnum + IB_UVERBS_MAX_DEVICES;
 		base = devnum + overflow_maj;
 		set_bit(devnum, overflow_map);
@@ -1079,7 +1075,6 @@ static void ib_uverbs_add_one(struct ib_
 		base = devnum + IB_UVERBS_BASE_DEV;
 		set_bit(devnum, dev_map);
 	}
-	spin_unlock(&map_lock);
 
 	rcu_assign_pointer(uverbs_dev->ib_dev, device);
 	uverbs_dev->num_comp_vectors = device->num_comp_vectors;