[PATCH net-next 01/10] netdevsim: fib: Introduce a lock to guard nexthop hashtable

[Petr Machata]

Currently netdevsim relies on RTNL to maintain exclusivity in accessing the
nexthop hash table. However, bucket notification may be called without RTNL
having been held. Instead, introduce a custom lock to guard the table.

Signed-off-by: Petr Machata <pe...@nvidia.com>
Reviewed-by: Ido Schimmel <ido...@nvidia.com>
---
 drivers/net/netdevsim/fib.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/net/netdevsim/fib.c b/drivers/net/netdevsim/fib.c
index 3ca0f54d0c3b..ba577e20b1a1 100644
--- a/drivers/net/netdevsim/fib.c
+++ b/drivers/net/netdevsim/fib.c
@@ -47,13 +47,14 @@ struct nsim_fib_data {
        struct nsim_fib_entry nexthops;
        struct rhashtable fib_rt_ht;
        struct list_head fib_rt_list;
-       struct mutex fib_lock; /* Protects hashtable and list */
+       struct mutex fib_lock; /* Protects FIB HT and list */
        struct notifier_block nexthop_nb;
        struct rhashtable nexthop_ht;
        struct devlink *devlink;
        struct work_struct fib_event_work;
        struct list_head fib_event_queue;
        spinlock_t fib_event_queue_lock; /* Protects fib event queue list */
+       struct mutex nh_lock; /* Protects NH HT */
        struct dentry *ddir;
        bool fail_route_offload;
 };
@@ -1262,8 +1263,7 @@ static int nsim_nexthop_event_nb(struct notifier_block 
*nb, unsigned long event,
        struct nh_notifier_info *info = ptr;
        int err = 0;
 
-       ASSERT_RTNL();
-
+       mutex_lock(&data->nh_lock);
        switch (event) {
        case NEXTHOP_EVENT_REPLACE:
                err = nsim_nexthop_insert(data, info);
@@ -1275,6 +1275,7 @@ static int nsim_nexthop_event_nb(struct notifier_block 
*nb, unsigned long event,
                break;
        }
 
+       mutex_unlock(&data->nh_lock);
        return notifier_from_errno(err);
 }
 
@@ -1404,6 +1405,7 @@ struct nsim_fib_data *nsim_fib_create(struct devlink 
*devlink,
        if (err)
                goto err_data_free;
 
+       mutex_init(&data->nh_lock);
        err = rhashtable_init(&data->nexthop_ht, &nsim_nexthop_ht_params);
        if (err)
                goto err_debugfs_exit;
@@ -1469,6 +1471,7 @@ struct nsim_fib_data *nsim_fib_create(struct devlink 
*devlink,
                                    data);
        mutex_destroy(&data->fib_lock);
 err_debugfs_exit:
+       mutex_destroy(&data->nh_lock);
        nsim_fib_debugfs_exit(data);
 err_data_free:
        kfree(data);
@@ -1497,6 +1500,7 @@ void nsim_fib_destroy(struct devlink *devlink, struct 
nsim_fib_data *data)
        WARN_ON_ONCE(!list_empty(&data->fib_event_queue));
        WARN_ON_ONCE(!list_empty(&data->fib_rt_list));
        mutex_destroy(&data->fib_lock);
+       mutex_destroy(&data->nh_lock);
        nsim_fib_debugfs_exit(data);
        kfree(data);
 }
-- 
2.26.2