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RDMA/cm: Use RCU synchronization mechanism to protect cm_id_private xa_load() 

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>
This commit is contained in:
Danit Goldberg 2019-12-19 15:47:50 +02:00 committed by Jason Gunthorpe
parent 9f48db0d4a
commit 4d6e8a033f
1 changed files with 13 additions and 30 deletions
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43
drivers/infiniband/core/cm.c
View File

@ -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_req(struct cm_work *work,
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_req(struct cm_work *work,
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 *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_rejected_id(struct cm_rej_msg *rej_msg)
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);