From: Danit Goldberg <danitg@mellanox.com>
Date: Thu, 19 Dec 2019 15:47:50 +0200
Subject: RDMA/cm: Use RCU synchronization mechanism to protect cm_id_private
xa_load()
Patch-mainline: v5.6-rc1
Git-commit: 4d6e8a033f7c6665c7ca5c5cdcf66019baa4b7a2
References: jsc#SLE-8449
The RCU mechanism is optimized for read-mostly scenarios and therefore
more suitable to protect the cm_id_private to decrease "cm.lock"
congestion.
This patch replaces the existing spinlock locking mechanism and kfree with
RCU mechanism in places where spinlock(cm.lock) protected xa_load
returning the cm_id_priv
In addition, delete the cm_get_id() function as there is no longer a
distinction if the caller already holds the cm_lock.
Remove an open coded version of cm_get_id().
Link: https://lore.kernel.org/r/20191219134750.413429-1-leon@kernel.org
Signed-off-by: Danit Goldberg <danitg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
drivers/infiniband/core/cm.c | 43 +++++++++++++------------------------------
1 file changed, 13 insertions(+), 30 deletions(-)
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -241,6 +241,7 @@ struct cm_id_private {
/* Number of clients sharing this ib_cm_id. Only valid for listeners.
* Protected by the cm.lock spinlock. */
int listen_sharecount;
+ struct rcu_head rcu;
struct ib_mad_send_buf *msg;
struct cm_timewait_info *timewait_info;
@@ -593,28 +594,16 @@ static void cm_free_id(__be32 local_id)
xa_erase_irq(&cm.local_id_table, cm_local_id(local_id));
}
-static struct cm_id_private * cm_get_id(__be32 local_id, __be32 remote_id)
+static struct cm_id_private *cm_acquire_id(__be32 local_id, __be32 remote_id)
{
struct cm_id_private *cm_id_priv;
+ rcu_read_lock();
cm_id_priv = xa_load(&cm.local_id_table, cm_local_id(local_id));
- if (cm_id_priv) {
- if (cm_id_priv->id.remote_id == remote_id)
- refcount_inc(&cm_id_priv->refcount);
- else
- cm_id_priv = NULL;
- }
-
- return cm_id_priv;
-}
-
-static struct cm_id_private * cm_acquire_id(__be32 local_id, __be32 remote_id)
-{
- struct cm_id_private *cm_id_priv;
-
- spin_lock_irq(&cm.lock);
- cm_id_priv = cm_get_id(local_id, remote_id);
- spin_unlock_irq(&cm.lock);
+ if (!cm_id_priv || cm_id_priv->id.remote_id != remote_id ||
+ !refcount_inc_not_zero(&cm_id_priv->refcount))
+ cm_id_priv = NULL;
+ rcu_read_unlock();
return cm_id_priv;
}
@@ -1089,7 +1078,7 @@ retest:
rdma_destroy_ah_attr(&cm_id_priv->av.ah_attr);
rdma_destroy_ah_attr(&cm_id_priv->alt_av.ah_attr);
kfree(cm_id_priv->private_data);
- kfree(cm_id_priv);
+ kfree_rcu(cm_id_priv, rcu);
}
void ib_destroy_cm_id(struct ib_cm_id *cm_id)
@@ -1821,7 +1810,7 @@ static struct cm_id_private * cm_match_r
spin_lock_irq(&cm.lock);
timewait_info = cm_insert_remote_id(cm_id_priv->timewait_info);
if (timewait_info) {
- cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,
+ cur_cm_id_priv = cm_acquire_id(timewait_info->work.local_id,
timewait_info->work.remote_id);
spin_unlock_irq(&cm.lock);
if (cur_cm_id_priv) {
@@ -1835,7 +1824,7 @@ static struct cm_id_private * cm_match_r
timewait_info = cm_insert_remote_qpn(cm_id_priv->timewait_info);
if (timewait_info) {
cm_cleanup_timewait(cm_id_priv->timewait_info);
- cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,
+ cur_cm_id_priv = cm_acquire_id(timewait_info->work.local_id,
timewait_info->work.remote_id);
spin_unlock_irq(&cm.lock);
@@ -2293,7 +2282,7 @@ static int cm_rep_handler(struct cm_work
rb_erase(&cm_id_priv->timewait_info->remote_id_node,
&cm.remote_id_table);
cm_id_priv->timewait_info->inserted_remote_id = 0;
- cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,
+ cur_cm_id_priv = cm_acquire_id(timewait_info->work.local_id,
timewait_info->work.remote_id);
spin_unlock(&cm.lock);
@@ -2788,14 +2777,8 @@ static struct cm_id_private * cm_acquire
spin_unlock_irq(&cm.lock);
return NULL;
}
- cm_id_priv = xa_load(&cm.local_id_table,
- cm_local_id(timewait_info->work.local_id));
- if (cm_id_priv) {
- if (cm_id_priv->id.remote_id == remote_id)
- refcount_inc(&cm_id_priv->refcount);
- else
- cm_id_priv = NULL;
- }
+ cm_id_priv =
+ cm_acquire_id(timewait_info->work.local_id, remote_id);
spin_unlock_irq(&cm.lock);
} else if (cm_rej_get_msg_rejected(rej_msg) == CM_MSG_RESPONSE_REQ)
cm_id_priv = cm_acquire_id(rej_msg->remote_comm_id, 0);