[PATCH 22/64] fcoe: Fix module ref count bug by adding NETDEV UNREGISTER handling

Robert Love
2009-08-25T21:00:22Z

From: Chris Leech <christopher.leech@intel.com>

Fixes reference counting on fcoe_instance and net_device, and adds
NETDEV_UNREGISTER notifier handling so that you can unload network drivers.
FCoE no longer increments the module use count for the network driver.

On an NETDEV_UNREGISTER event, destroying the FCoE instance is deferred to a
workqueue context to avoid RTNL deadlocks.

Based in part by an earlier patch from John Fastabend

John's patch description:
Currently, the netdev module ref count is not decremented with module_put()
when the module is unloaded while fcoe instances are present. To fix this
removed reference count on netdev module completely and added functionality to
netdev event handling for NETDEV_UNREGISTER events.

This allows fcoe to remove devices cleanly when the netdev module is unloaded
so we no longer need to hold a reference count for the netdev module.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
---

drivers/scsi/fcoe/fcoe.c | 186 ++++++++++++++++------------------------------
drivers/scsi/fcoe/fcoe.h | 2
2 files changed, 67 insertions(+), 121 deletions(-)

diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index c9a0346..c0264a9 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -74,12 +74,13 @@ static int fcoe_link_ok(struct fc_lport *lp);

static struct fc_lport *fcoe_hostlist_lookup(const struct net_device *);
static int fcoe_hostlist_add(const struct fc_lport *);
-static int fcoe_hostlist_remove(const struct fc_lport *);

static void fcoe_check_wait_queue(struct fc_lport *, struct sk_buff *);
static int fcoe_device_notification(struct notifier_block *, ulong, void *);
static void fcoe_dev_setup(void);
static void fcoe_dev_cleanup(void);
+static struct fcoe_interface *
+ fcoe_hostlist_lookup_port(const struct net_device *dev);

/* notification function from net device */
static struct notifier_block fcoe_notifier = {
@@ -149,6 +150,7 @@ static int fcoe_fip_recv(struct sk_buff *skb, struct net_device *dev,
* @netdev : ptr to the associated netdevice struct
*
* Returns : 0 for success
+ * Locking: must be called with the RTNL mutex held
*/
static int fcoe_interface_setup(struct fcoe_interface *fcoe,
struct net_device *netdev)
@@ -188,13 +190,11 @@ static int fcoe_interface_setup(struct fcoe_interface *fcoe,
* or enter promiscuous mode if not capable of listening
* for multiple unicast MACs.
*/
- rtnl_lock();
memcpy(flogi_maddr, (u8[6]) FC_FCOE_FLOGI_MAC, ETH_ALEN);
dev_unicast_add(netdev, flogi_maddr);
if (fip->spma)
dev_unicast_add(netdev, fip->ctl_src_addr);
dev_mc_add(netdev, FIP_ALL_ENODE_MACS, ETH_ALEN, 0);
- rtnl_unlock();

/*
* setup the receive function from ethernet driver
@@ -215,6 +215,7 @@ static int fcoe_interface_setup(struct fcoe_interface *fcoe,

static void fcoe_fip_send(struct fcoe_ctlr *fip, struct sk_buff *skb);
static void fcoe_update_src_mac(struct fcoe_ctlr *fip, u8 *old, u8 *new);
+static void fcoe_destroy_work(struct work_struct *work);

/**
* fcoe_interface_create()
@@ -232,6 +233,7 @@ static struct fcoe_interface *fcoe_interface_create(struct net_device *netdev)
return NULL;
}

+ dev_hold(netdev);
kref_init(&fcoe->kref);

/*
@@ -249,6 +251,8 @@ static struct fcoe_interface *fcoe_interface_create(struct net_device *netdev)
/**
* fcoe_interface_cleanup() - clean up netdev configurations
* @fcoe:
+ *
+ * Caller must be holding the RTNL mutex
*/
void fcoe_interface_cleanup(struct fcoe_interface *fcoe)
{
@@ -266,11 +270,7 @@ void fcoe_interface_cleanup(struct fcoe_interface *fcoe)
__dev_remove_pack(&fcoe->fip_packet_type);
synchronize_net();

- /* tear-down the FCoE controller */
- fcoe_ctlr_destroy(&fcoe->ctlr);
-
/* Delete secondary MAC addresses */
- rtnl_lock();
memcpy(flogi_maddr, (u8[6]) FC_FCOE_FLOGI_MAC, ETH_ALEN);
dev_unicast_delete(netdev, flogi_maddr);
if (!is_zero_ether_addr(fip->data_src_addr))
@@ -278,7 +278,6 @@ void fcoe_interface_cleanup(struct fcoe_interface *fcoe)
if (fip->spma)
dev_unicast_delete(netdev, fip->ctl_src_addr);
dev_mc_delete(netdev, FIP_ALL_ENODE_MACS, ETH_ALEN, 0);
- rtnl_unlock();
}

/**
@@ -288,10 +287,14 @@ void fcoe_interface_cleanup(struct fcoe_interface *fcoe)
static void fcoe_interface_release(struct kref *kref)
{
struct fcoe_interface *fcoe;
+ struct net_device *netdev;

fcoe = container_of(kref, struct fcoe_interface, kref);
- fcoe_interface_cleanup(fcoe);
+ netdev = fcoe->netdev;
+ /* tear-down the FCoE controller */
+ fcoe_ctlr_destroy(&fcoe->ctlr);
kfree(fcoe);
+ dev_put(netdev);
}

/**
@@ -642,8 +645,7 @@ static void fcoe_if_destroy(struct fc_lport *lport)
/* Free memory used by statistical counters */
fc_lport_free_stats(lport);

- /* Release the net_device and Scsi_Host */
- dev_put(netdev);
+ /* Release the Scsi_Host */
scsi_host_put(lport->host);
}

@@ -718,7 +720,9 @@ static struct fc_lport *fcoe_if_create(struct fcoe_interface *fcoe,
}
lport = shost_priv(shost);
port = lport_priv(lport);
+ port->lport = lport;
port->fcoe = fcoe;
+ INIT_WORK(&port->destroy_work, fcoe_destroy_work);

/* configure fc_lport, e.g., em */
rc = fcoe_lport_config(lport);
@@ -769,7 +773,6 @@ static struct fc_lport *fcoe_if_create(struct fcoe_interface *fcoe,
goto out_lp_destroy;
}

- dev_hold(netdev);
fcoe_interface_get(fcoe);
return lport;

@@ -1530,19 +1533,19 @@ static int fcoe_device_notification(struct notifier_block *notifier,
struct fc_lport *lp = NULL;
struct net_device *netdev = ptr;
struct fcoe_interface *fcoe;
+ struct fcoe_port *port;
struct fcoe_dev_stats *stats;
u32 link_possible = 1;
u32 mfs;
int rc = NOTIFY_OK;

- read_lock(&fcoe_hostlist_lock);
+ write_lock(&fcoe_hostlist_lock);
list_for_each_entry(fcoe, &fcoe_hostlist, list) {
if (fcoe->netdev == netdev) {
lp = fcoe->ctlr.lp;
break;
}
}
- read_unlock(&fcoe_hostlist_lock);
if (lp == NULL) {
rc = NOTIFY_DONE;
goto out;
@@ -1564,6 +1567,13 @@ static int fcoe_device_notification(struct notifier_block *notifier,
break;
case NETDEV_REGISTER:
break;
+ case NETDEV_UNREGISTER:
+ list_del(&fcoe->list);
+ port = lport_priv(fcoe->ctlr.lp);
+ fcoe_interface_cleanup(fcoe);
+ schedule_work(&port->destroy_work);
+ goto out;
+ break;
default:
FCOE_NETDEV_DBG(netdev, "Unknown event %ld "
"from netdev netlink\n", event);
@@ -1576,6 +1586,7 @@ static int fcoe_device_notification(struct notifier_block *notifier,
fcoe_clean_pending_queue(lp);
}
out:
+ write_unlock(&fcoe_hostlist_lock);
return rc;
}

@@ -1601,75 +1612,6 @@ static struct net_device *fcoe_if_to_netdev(const char *buffer)
}

/**
- * fcoe_netdev_to_module_owner() - finds out the driver module of the netdev
- * @netdev: the target netdev
- *
- * Returns: ptr to the struct module, NULL for failure
- */
-static struct module *
-fcoe_netdev_to_module_owner(const struct net_device *netdev)
-{
- struct device *dev;
-
- if (!netdev)
- return NULL;
-
- dev = netdev->dev.parent;
- if (!dev)
- return NULL;
-
- if (!dev->driver)
- return NULL;
-
- return dev->driver->owner;
-}
-
-/**
- * fcoe_ethdrv_get() - Hold the Ethernet driver
- * @netdev: the target netdev
- *
- * Holds the Ethernet driver module by try_module_get() for
- * the corresponding netdev.
- *
- * Returns: 0 for success
- */
-static int fcoe_ethdrv_get(const struct net_device *netdev)
-{
- struct module *owner;
-
- owner = fcoe_netdev_to_module_owner(netdev);
- if (owner) {
- FCOE_NETDEV_DBG(netdev, "Hold driver module %s\n",
- module_name(owner));
- return try_module_get(owner);
- }
- return -ENODEV;
-}
-
-/**
- * fcoe_ethdrv_put() - Release the Ethernet driver
- * @netdev: the target netdev
- *
- * Releases the Ethernet driver module by module_put for
- * the corresponding netdev.
- *
- * Returns: 0 for success
- */
-static int fcoe_ethdrv_put(const struct net_device *netdev)
-{
- struct module *owner;
-
- owner = fcoe_netdev_to_module_owner(netdev);
- if (owner) {
- FCOE_NETDEV_DBG(netdev, "Release driver module %s\n",
- module_name(owner));
- module_put(owner);
- return 0;
- }
- return -ENODEV;
-}
-
-/**
* fcoe_destroy() - handles the destroy from sysfs
* @buffer: expected to be an eth if name
* @kp: associated kernel param
@@ -1678,10 +1620,8 @@ static int fcoe_ethdrv_put(const struct net_device *netdev)
*/
static int fcoe_destroy(const char *buffer, struct kernel_param *kp)
{
- struct net_device *netdev;
struct fcoe_interface *fcoe;
- struct fcoe_port *port;
- struct fc_lport *lport;
+ struct net_device *netdev;
int rc;

mutex_lock(&fcoe_config_mutex);
@@ -1702,19 +1642,20 @@ static int fcoe_destroy(const char *buffer, struct kernel_param *kp)
rc = -ENODEV;
goto out_nodev;
}
- /* look for existing lport */
- lport = fcoe_hostlist_lookup(netdev);
- if (!lport) {
+
+ write_lock(&fcoe_hostlist_lock);
+ fcoe = fcoe_hostlist_lookup_port(netdev);
+ if (!fcoe) {
+ write_unlock(&fcoe_hostlist_lock);
rc = -ENODEV;
goto out_putdev;
}
- /* Remove the instance from fcoe's list */
- fcoe_hostlist_remove(lport);
- port = lport_priv(lport);
- fcoe = port->fcoe;
- fcoe_if_destroy(lport);
- fcoe_ethdrv_put(netdev);
- rc = 0;
+ list_del(&fcoe->list);
+ write_unlock(&fcoe_hostlist_lock);
+ rtnl_lock();
+ fcoe_interface_cleanup(fcoe);
+ rtnl_unlock();
+ fcoe_if_destroy(fcoe->ctlr.lp);
out_putdev:
dev_put(netdev);
out_nodev:
@@ -1722,6 +1663,16 @@ out_nodev:
return rc;
}

+static void fcoe_destroy_work(struct work_struct *work)
+{
+ struct fcoe_port *port;
+
+ port = container_of(work, struct fcoe_port, destroy_work);
+ mutex_lock(&fcoe_config_mutex);
+ fcoe_if_destroy(port->lport);
+ mutex_unlock(&fcoe_config_mutex);
+}
+
/**
* fcoe_create() - Handles the create call from sysfs
* @buffer: expected to be an eth if name
@@ -1749,17 +1700,18 @@ static int fcoe_create(const char *buffer, struct kernel_param *kp)
}
#endif

+ rtnl_lock();
netdev = fcoe_if_to_netdev(buffer);
if (!netdev) {
rc = -ENODEV;
goto out_nodev;
}
+
/* look for existing lport */
if (fcoe_hostlist_lookup(netdev)) {
rc = -EEXIST;
goto out_putdev;
}
- fcoe_ethdrv_get(netdev);

fcoe = fcoe_interface_create(netdev);
if (!fcoe) {
@@ -1771,8 +1723,8 @@ static int fcoe_create(const char *buffer, struct kernel_param *kp)
if (IS_ERR(lport)) {
printk(KERN_ERR "fcoe: Failed to create interface (%s)\n",
netdev->name);
- fcoe_ethdrv_put(netdev);
rc = -EIO;
+ fcoe_interface_cleanup(fcoe);
goto out_free;
}

@@ -1798,6 +1750,7 @@ out_free:
out_putdev:
dev_put(netdev);
out_nodev:
+ rtnl_unlock();
mutex_unlock(&fcoe_config_mutex);
return rc;
}
@@ -1973,25 +1926,6 @@ int fcoe_hostlist_add(const struct fc_lport *lport)
}

/**
- * fcoe_hostlist_remove() - remove a lport from lports list
- * @lp: ptr to the fc_lport to be removed
- *
- * Returns: 0 for success
- */
-int fcoe_hostlist_remove(const struct fc_lport *lport)
-{
- struct fcoe_interface *fcoe;
-
- write_lock_bh(&fcoe_hostlist_lock);
- fcoe = fcoe_hostlist_lookup_port(fcoe_netdev(lport));
- BUG_ON(!fcoe);
- list_del(&fcoe->list);
- write_unlock_bh(&fcoe_hostlist_lock);
-
- return 0;
-}
-
-/**
* fcoe_init() - fcoe module loading initialization
*
* Returns 0 on success, negative on failure
@@ -2046,6 +1980,7 @@ static void __exit fcoe_exit(void)
unsigned int cpu;
struct fcoe_interface *fcoe, *tmp;
LIST_HEAD(local_list);
+ struct fcoe_port *port;

mutex_lock(&fcoe_config_mutex);

@@ -2058,7 +1993,11 @@ static void __exit fcoe_exit(void)

list_for_each_entry_safe(fcoe, tmp, &local_list, list) {
list_del(&fcoe->list);
- fcoe_if_destroy(fcoe->ctlr.lp);
+ port = lport_priv(fcoe->ctlr.lp);
+ rtnl_lock();
+ fcoe_interface_cleanup(fcoe);
+ rtnl_unlock();
+ schedule_work(&port->destroy_work);
}

unregister_hotcpu_notifier(&fcoe_cpu_notifier);
@@ -2066,9 +2005,14 @@ static void __exit fcoe_exit(void)
for_each_online_cpu(cpu)
fcoe_percpu_thread_destroy(cpu);

- /* detach from scsi transport */
- fcoe_if_exit();
-
mutex_unlock(&fcoe_config_mutex);
+
+ /* flush any asyncronous interface destroys,
+ * this should happen after the netdev notifier is unregistered */
+ flush_scheduled_work();
+
+ /* detach from scsi transport
+ * must happen after all destroys are done, therefor after the flush */
+ fcoe_if_exit();
}
module_exit(fcoe_exit);
diff --git a/drivers/scsi/fcoe/fcoe.h b/drivers/scsi/fcoe/fcoe.h
index ff22928..ce7f60f 100644
--- a/drivers/scsi/fcoe/fcoe.h
+++ b/drivers/scsi/fcoe/fcoe.h
@@ -93,9 +93,11 @@ struct fcoe_interface {
*/
struct fcoe_port {
struct fcoe_interface *fcoe;
+ struct fc_lport *lport;
struct sk_buff_head fcoe_pending_queue;
u8 fcoe_pending_queue_active;
struct timer_list timer; /* queue timer */
+ struct work_struct destroy_work; /* to prevent rtnl deadlocks */
};

#define fcoe_from_ctlr(fip) container_of(fip, struct fcoe_interface, ctlr)