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Subject[PATCH v3 2/2] IB/mad: Use IDR for agent IDs
Date
Allocate agent IDs from a global IDR instead of an atomic variable.
This eliminates the possibility of reusing an ID which is already in
use after 4 billion registrations. We limit the assigned ID to be less
than 2^24 as the mlx4 driver uses the most significant byte of the agent
ID to store the slave number. Users unlucky enough to see a collision
between agent numbers and slave numbers see messages like:

mlx4_ib: egress mad has non-null tid msb:1 class:4 slave:0

and the MAD layer stops working.

We look up the agent under protection of the RCU lock, which means we
have to free the agent using kfree_rcu, and only increment the reference
counter if it is not 0.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reported-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Acked-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Tested-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
---
drivers/infiniband/core/mad.c | 83 ++++++++++++++++++------------
drivers/infiniband/core/mad_priv.h | 7 +--
2 files changed, 55 insertions(+), 35 deletions(-)

diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c
index 68f4dda916c8..b854aeddd221 100644
--- a/drivers/infiniband/core/mad.c
+++ b/drivers/infiniband/core/mad.c
@@ -38,6 +38,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/dma-mapping.h>
+#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/security.h>
@@ -58,8 +59,13 @@ MODULE_PARM_DESC(send_queue_size, "Size of send queue in number of work requests
module_param_named(recv_queue_size, mad_recvq_size, int, 0444);
MODULE_PARM_DESC(recv_queue_size, "Size of receive queue in number of work requests");

+/*
+ * The mlx4 driver uses the top byte to distinguish which virtual function
+ * generated the MAD, so we must avoid using it.
+ */
+#define AGENT_ID_LIMIT (1 << 24)
+static DEFINE_IDR(ib_mad_clients);
static struct list_head ib_mad_port_list;
-static atomic_t ib_mad_client_id = ATOMIC_INIT(0);

/* Port list lock */
static DEFINE_SPINLOCK(ib_mad_port_list_lock);
@@ -377,13 +383,24 @@ struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device,
goto error4;
}

- spin_lock_irq(&port_priv->reg_lock);
- mad_agent_priv->agent.hi_tid = atomic_inc_return(&ib_mad_client_id);
+ idr_preload(GFP_KERNEL);
+ idr_lock(&ib_mad_clients);
+ ret2 = idr_alloc_cyclic(&ib_mad_clients, mad_agent_priv, 0,
+ AGENT_ID_LIMIT, GFP_ATOMIC);
+ idr_unlock(&ib_mad_clients);
+ idr_preload_end();
+
+ if (ret2 < 0) {
+ ret = ERR_PTR(ret2);
+ goto error5;
+ }
+ mad_agent_priv->agent.hi_tid = ret2;

/*
* Make sure MAD registration (if supplied)
* is non overlapping with any existing ones
*/
+ spin_lock_irq(&port_priv->reg_lock);
if (mad_reg_req) {
mgmt_class = convert_mgmt_class(mad_reg_req->mgmt_class);
if (!is_vendor_class(mgmt_class)) {
@@ -394,7 +411,7 @@ struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device,
if (method) {
if (method_in_use(&method,
mad_reg_req))
- goto error5;
+ goto error6;
}
}
ret2 = add_nonoui_reg_req(mad_reg_req, mad_agent_priv,
@@ -410,24 +427,25 @@ struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device,
if (is_vendor_method_in_use(
vendor_class,
mad_reg_req))
- goto error5;
+ goto error6;
}
}
ret2 = add_oui_reg_req(mad_reg_req, mad_agent_priv);
}
if (ret2) {
ret = ERR_PTR(ret2);
- goto error5;
+ goto error6;
}
}
-
- /* Add mad agent into port's agent list */
- list_add_tail(&mad_agent_priv->agent_list, &port_priv->agent_list);
spin_unlock_irq(&port_priv->reg_lock);

return &mad_agent_priv->agent;
-error5:
+error6:
spin_unlock_irq(&port_priv->reg_lock);
+ idr_lock(&ib_mad_clients);
+ idr_remove(&ib_mad_clients, mad_agent_priv->agent.hi_tid);
+ idr_unlock(&ib_mad_clients);
+error5:
ib_mad_agent_security_cleanup(&mad_agent_priv->agent);
error4:
kfree(reg_req);
@@ -589,8 +607,10 @@ static void unregister_mad_agent(struct ib_mad_agent_private *mad_agent_priv)

spin_lock_irq(&port_priv->reg_lock);
remove_mad_reg_req(mad_agent_priv);
- list_del(&mad_agent_priv->agent_list);
spin_unlock_irq(&port_priv->reg_lock);
+ idr_lock(&ib_mad_clients);
+ idr_remove(&ib_mad_clients, mad_agent_priv->agent.hi_tid);
+ idr_unlock(&ib_mad_clients);

flush_workqueue(port_priv->wq);
ib_cancel_rmpp_recvs(mad_agent_priv);
@@ -601,7 +621,7 @@ static void unregister_mad_agent(struct ib_mad_agent_private *mad_agent_priv)
ib_mad_agent_security_cleanup(&mad_agent_priv->agent);

kfree(mad_agent_priv->reg_req);
- kfree(mad_agent_priv);
+ kfree_rcu(mad_agent_priv, rcu);
}

static void unregister_mad_snoop(struct ib_mad_snoop_private *mad_snoop_priv)
@@ -1722,22 +1742,19 @@ find_mad_agent(struct ib_mad_port_private *port_priv,
struct ib_mad_agent_private *mad_agent = NULL;
unsigned long flags;

- spin_lock_irqsave(&port_priv->reg_lock, flags);
if (ib_response_mad(mad_hdr)) {
u32 hi_tid;
- struct ib_mad_agent_private *entry;

/*
* Routing is based on high 32 bits of transaction ID
* of MAD.
*/
hi_tid = be64_to_cpu(mad_hdr->tid) >> 32;
- list_for_each_entry(entry, &port_priv->agent_list, agent_list) {
- if (entry->agent.hi_tid == hi_tid) {
- mad_agent = entry;
- break;
- }
- }
+ rcu_read_lock();
+ mad_agent = idr_find(&ib_mad_clients, hi_tid);
+ if (mad_agent && !atomic_inc_not_zero(&mad_agent->refcount))
+ mad_agent = NULL;
+ rcu_read_unlock();
} else {
struct ib_mad_mgmt_class_table *class;
struct ib_mad_mgmt_method_table *method;
@@ -1746,6 +1763,7 @@ find_mad_agent(struct ib_mad_port_private *port_priv,
const struct ib_vendor_mad *vendor_mad;
int index;

+ spin_lock_irqsave(&port_priv->reg_lock, flags);
/*
* Routing is based on version, class, and method
* For "newer" vendor MADs, also based on OUI
@@ -1785,20 +1803,19 @@ find_mad_agent(struct ib_mad_port_private *port_priv,
~IB_MGMT_METHOD_RESP];
}
}
+ if (mad_agent)
+ atomic_inc(&mad_agent->refcount);
+out:
+ spin_unlock_irqrestore(&port_priv->reg_lock, flags);
}

- if (mad_agent) {
- if (mad_agent->agent.recv_handler)
- atomic_inc(&mad_agent->refcount);
- else {
- dev_notice(&port_priv->device->dev,
- "No receive handler for client %p on port %d\n",
- &mad_agent->agent, port_priv->port_num);
- mad_agent = NULL;
- }
+ if (mad_agent && !mad_agent->agent.recv_handler) {
+ dev_notice(&port_priv->device->dev,
+ "No receive handler for client %p on port %d\n",
+ &mad_agent->agent, port_priv->port_num);
+ deref_mad_agent(mad_agent);
+ mad_agent = NULL;
}
-out:
- spin_unlock_irqrestore(&port_priv->reg_lock, flags);

return mad_agent;
}
@@ -3161,7 +3178,6 @@ static int ib_mad_port_open(struct ib_device *device,
port_priv->device = device;
port_priv->port_num = port_num;
spin_lock_init(&port_priv->reg_lock);
- INIT_LIST_HEAD(&port_priv->agent_list);
init_mad_qp(port_priv, &port_priv->qp_info[0]);
init_mad_qp(port_priv, &port_priv->qp_info[1]);

@@ -3340,6 +3356,9 @@ int ib_mad_init(void)

INIT_LIST_HEAD(&ib_mad_port_list);

+ /* Client ID 0 is used for snoop-only clients */
+ idr_alloc(&ib_mad_clients, NULL, 0, 0, GFP_KERNEL);
+
if (ib_register_client(&mad_client)) {
pr_err("Couldn't register ib_mad client\n");
return -EINVAL;
diff --git a/drivers/infiniband/core/mad_priv.h b/drivers/infiniband/core/mad_priv.h
index 28669f6419e1..d84ae1671898 100644
--- a/drivers/infiniband/core/mad_priv.h
+++ b/drivers/infiniband/core/mad_priv.h
@@ -89,7 +89,6 @@ struct ib_rmpp_segment {
};

struct ib_mad_agent_private {
- struct list_head agent_list;
struct ib_mad_agent agent;
struct ib_mad_reg_req *reg_req;
struct ib_mad_qp_info *qp_info;
@@ -105,7 +104,10 @@ struct ib_mad_agent_private {
struct list_head rmpp_list;

atomic_t refcount;
- struct completion comp;
+ union {
+ struct completion comp;
+ struct rcu_head rcu;
+ };
};

struct ib_mad_snoop_private {
@@ -203,7 +205,6 @@ struct ib_mad_port_private {

spinlock_t reg_lock;
struct ib_mad_mgmt_version_table version[MAX_MGMT_VERSION];
- struct list_head agent_list;
struct workqueue_struct *wq;
struct ib_mad_qp_info qp_info[IB_MAD_QPS_CORE];
};
--
2.17.1
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