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[DECnet]: Use RCU locking in dn_rules.c
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As per Robert Olsson's patch for ipv4, this is the DECnet
version to keep the code "in step". It changes the list
of rules to use RCU rather than an rwlock.

Inspired-by: Robert Olsson <robert.olsson@its.uu.se>
Signed-off-by: Steven Whitehouse <steve@chygwyn.com>
Signed-off-by: Patrick Caulfield <patrick@tykepenguin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Steven Whitehouse authored and David S. Miller committed Mar 21, 2006
1 parent c60992d commit ecba320
Showing 1 changed file with 53 additions and 44 deletions.
97 changes: 53 additions & 44 deletions net/decnet/dn_rules.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@
#include <linux/timer.h>
#include <linux/spinlock.h>
#include <linux/in_route.h>
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <asm/atomic.h>
#include <asm/uaccess.h>
#include <net/neighbour.h>
Expand All @@ -39,7 +41,7 @@

struct dn_fib_rule
{
struct dn_fib_rule *r_next;
struct hlist_node r_hlist;
atomic_t r_clntref;
u32 r_preference;
unsigned char r_table;
Expand All @@ -58,6 +60,7 @@ struct dn_fib_rule
int r_ifindex;
char r_ifname[IFNAMSIZ];
int r_dead;
struct rcu_head rcu;
};

static struct dn_fib_rule default_rule = {
Expand All @@ -67,18 +70,17 @@ static struct dn_fib_rule default_rule = {
.r_action = RTN_UNICAST
};

static struct dn_fib_rule *dn_fib_rules = &default_rule;
static DEFINE_RWLOCK(dn_fib_rules_lock);

static struct hlist_head dn_fib_rules;

int dn_fib_rtm_delrule(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
{
struct rtattr **rta = arg;
struct rtmsg *rtm = NLMSG_DATA(nlh);
struct dn_fib_rule *r, **rp;
struct dn_fib_rule *r;
struct hlist_node *node;
int err = -ESRCH;

for(rp=&dn_fib_rules; (r=*rp) != NULL; rp = &r->r_next) {
hlist_for_each_entry(r, node, &dn_fib_rules, r_hlist) {
if ((!rta[RTA_SRC-1] || memcmp(RTA_DATA(rta[RTA_SRC-1]), &r->r_src, 2) == 0) &&
rtm->rtm_src_len == r->r_src_len &&
rtm->rtm_dst_len == r->r_dst_len &&
Expand All @@ -95,10 +97,8 @@ int dn_fib_rtm_delrule(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
if (r == &default_rule)
break;

write_lock_bh(&dn_fib_rules_lock);
*rp = r->r_next;
hlist_del_rcu(&r->r_hlist);
r->r_dead = 1;
write_unlock_bh(&dn_fib_rules_lock);
dn_fib_rule_put(r);
err = 0;
break;
Expand All @@ -108,11 +108,17 @@ int dn_fib_rtm_delrule(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
return err;
}

static inline void dn_fib_rule_put_rcu(struct rcu_head *head)
{
struct dn_fib_rule *r = container_of(head, struct dn_fib_rule, rcu);
kfree(r);
}

void dn_fib_rule_put(struct dn_fib_rule *r)
{
if (atomic_dec_and_test(&r->r_clntref)) {
if (r->r_dead)
kfree(r);
call_rcu(&r->rcu, dn_fib_rule_put_rcu);
else
printk(KERN_DEBUG "Attempt to free alive dn_fib_rule\n");
}
Expand All @@ -123,7 +129,8 @@ int dn_fib_rtm_newrule(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
{
struct rtattr **rta = arg;
struct rtmsg *rtm = NLMSG_DATA(nlh);
struct dn_fib_rule *r, *new_r, **rp;
struct dn_fib_rule *r, *new_r, *last = NULL;
struct hlist_node *node = NULL;
unsigned char table_id;

if (rtm->rtm_src_len > 16 || rtm->rtm_dst_len > 16)
Expand All @@ -149,6 +156,7 @@ int dn_fib_rtm_newrule(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
if (!new_r)
return -ENOMEM;
memset(new_r, 0, sizeof(*new_r));

if (rta[RTA_SRC-1])
memcpy(&new_r->r_src, RTA_DATA(rta[RTA_SRC-1]), 2);
if (rta[RTA_DST-1])
Expand Down Expand Up @@ -179,27 +187,26 @@ int dn_fib_rtm_newrule(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
}
}

rp = &dn_fib_rules;
r = container_of(dn_fib_rules.first, struct dn_fib_rule, r_hlist);
if (!new_r->r_preference) {
r = dn_fib_rules;
if (r && (r = r->r_next) != NULL) {
rp = &dn_fib_rules->r_next;
if (r && r->r_hlist.next != NULL) {
r = container_of(r->r_hlist.next, struct dn_fib_rule, r_hlist);
if (r->r_preference)
new_r->r_preference = r->r_preference - 1;
}
}

while((r=*rp) != NULL) {
hlist_for_each_entry(r, node, &dn_fib_rules, r_hlist) {
if (r->r_preference > new_r->r_preference)
break;
rp = &r->r_next;
last = r;
}

new_r->r_next = r;
atomic_inc(&new_r->r_clntref);
write_lock_bh(&dn_fib_rules_lock);
*rp = new_r;
write_unlock_bh(&dn_fib_rules_lock);

if (last)
hlist_add_after_rcu(&last->r_hlist, &new_r->r_hlist);
else
hlist_add_before_rcu(&new_r->r_hlist, &r->r_hlist);
return 0;
}

Expand All @@ -210,10 +217,12 @@ int dn_fib_lookup(const struct flowi *flp, struct dn_fib_res *res)
struct dn_fib_table *tb;
__le16 saddr = flp->fld_src;
__le16 daddr = flp->fld_dst;
struct hlist_node *node;
int err;

read_lock(&dn_fib_rules_lock);
for(r = dn_fib_rules; r; r = r->r_next) {
rcu_read_lock();

hlist_for_each_entry_rcu(r, node, &dn_fib_rules, r_hlist) {
if (((saddr^r->r_src) & r->r_srcmask) ||
((daddr^r->r_dst) & r->r_dstmask) ||
#ifdef CONFIG_DECNET_ROUTE_FWMARK
Expand All @@ -228,14 +237,14 @@ int dn_fib_lookup(const struct flowi *flp, struct dn_fib_res *res)
policy = r;
break;
case RTN_UNREACHABLE:
read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
return -ENETUNREACH;
default:
case RTN_BLACKHOLE:
read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
return -EINVAL;
case RTN_PROHIBIT:
read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
return -EACCES;
}

Expand All @@ -246,16 +255,16 @@ int dn_fib_lookup(const struct flowi *flp, struct dn_fib_res *res)
res->r = policy;
if (policy)
atomic_inc(&policy->r_clntref);
read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
return 0;
}
if (err < 0 && err != -EAGAIN) {
read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
return err;
}
}

read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
return -ESRCH;
}

Expand Down Expand Up @@ -297,27 +306,23 @@ __le16 dn_fib_rules_policy(__le16 saddr, struct dn_fib_res *res, unsigned *flags

static void dn_fib_rules_detach(struct net_device *dev)
{
struct hlist_node *node;
struct dn_fib_rule *r;

for(r = dn_fib_rules; r; r = r->r_next) {
if (r->r_ifindex == dev->ifindex) {
write_lock_bh(&dn_fib_rules_lock);
hlist_for_each_entry(r, node, &dn_fib_rules, r_hlist) {
if (r->r_ifindex == dev->ifindex)
r->r_ifindex = -1;
write_unlock_bh(&dn_fib_rules_lock);
}
}
}

static void dn_fib_rules_attach(struct net_device *dev)
{
struct hlist_node *node;
struct dn_fib_rule *r;

for(r = dn_fib_rules; r; r = r->r_next) {
if (r->r_ifindex == -1 && strcmp(dev->name, r->r_ifname) == 0) {
write_lock_bh(&dn_fib_rules_lock);
hlist_for_each_entry(r, node, &dn_fib_rules, r_hlist) {
if (r->r_ifindex == -1 && strcmp(dev->name, r->r_ifname) == 0)
r->r_ifindex = dev->ifindex;
write_unlock_bh(&dn_fib_rules_lock);
}
}
}

Expand Down Expand Up @@ -387,25 +392,29 @@ static int dn_fib_fill_rule(struct sk_buff *skb, struct dn_fib_rule *r,

int dn_fib_dump_rules(struct sk_buff *skb, struct netlink_callback *cb)
{
int idx;
int idx = 0;
int s_idx = cb->args[0];
struct dn_fib_rule *r;
struct hlist_node *node;

read_lock(&dn_fib_rules_lock);
for(r = dn_fib_rules, idx = 0; r; r = r->r_next, idx++) {
rcu_read_lock();
hlist_for_each_entry(r, node, &dn_fib_rules, r_hlist) {
if (idx < s_idx)
continue;
if (dn_fib_fill_rule(skb, r, cb, NLM_F_MULTI) < 0)
break;
idx++;
}
read_unlock(&dn_fib_rules_lock);
rcu_read_unlock();
cb->args[0] = idx;

return skb->len;
}

void __init dn_fib_rules_init(void)
{
INIT_HLIST_HEAD(&dn_fib_rules);
hlist_add_head(&default_rule.r_hlist, &dn_fib_rules);
register_netdevice_notifier(&dn_fib_rules_notifier);
}

Expand Down

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