A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-28 18:51:56 -04:00
Code Issues Projects Releases Packages Wiki Activity

ipv4: Restore old dst_free() behavior.

Browse source 
commit 404e0a8b6a (net: ipv4: fix RCU races on dst refcounts) tried
to solve a race but added a problem at device/fib dismantle time :

We really want to call dst_free() as soon as possible, even if sockets
still have dst in their cache.
dst_release() calls in free_fib_info_rcu() are not welcomed.

Root of the problem was that now we also cache output routes (in
nh_rth_output), we must use call_rcu() instead of call_rcu_bh() in
rt_free(), because output route lookups are done in process context.

Based on feedback and initial patch from David Miller (adding another
call_rcu_bh() call in fib, but it appears it was not the right fix)

I left the inet_sk_rx_dst_set() helper and added __rcu attributes
to nh_rth_output and nh_rth_input to better document what is going on in
this code.

Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Eric Dumazet 2012-07-31 01:08:23 +00:00 • committed by David S. Miller
commit 54764bb647
7 changed files with 50 additions and 50 deletions
Download patch file Download diff file Expand all files Collapse all files

21
net/ipv4/fib_semantics.c
View file

@ -161,6 +161,21 @@ static void free_nh_exceptions(struct fib_nh *nh)
kfree(hash);
}
static void rt_nexthop_free(struct rtable __rcu **rtp)
{
struct rtable *rt = rcu_dereference_protected(*rtp, 1);
if (!rt)
return;
/* Not even needed : RCU_INIT_POINTER(*rtp, NULL);
* because we waited an RCU grace period before calling
* free_fib_info_rcu()
*/
dst_free(&rt->dst);
}
/* Release a nexthop info record */
static void free_fib_info_rcu(struct rcu_head *head)
{
@ -171,10 +186,8 @@ static void free_fib_info_rcu(struct rcu_head *head)
dev_put(nexthop_nh->nh_dev);
if (nexthop_nh->nh_exceptions)
free_nh_exceptions(nexthop_nh);
if (nexthop_nh->nh_rth_output)
dst_release(&nexthop_nh->nh_rth_output->dst);
if (nexthop_nh->nh_rth_input)
dst_release(&nexthop_nh->nh_rth_input->dst);
rt_nexthop_free(&nexthop_nh->nh_rth_output);
rt_nexthop_free(&nexthop_nh->nh_rth_input);
} endfor_nexthops(fi);
release_net(fi->fib_net);

26
net/ipv4/route.c
View file

@ -1199,23 +1199,31 @@ restart:
fnhe->fnhe_stamp = jiffies;
}
static inline void rt_free(struct rtable *rt)
{
call_rcu(&rt->dst.rcu_head, dst_rcu_free);
}
static void rt_cache_route(struct fib_nh *nh, struct rtable *rt)
{
struct rtable *orig, *prev, **p = &nh->nh_rth_output;
struct rtable *orig, *prev, **p = (struct rtable **)&nh->nh_rth_output;
if (rt_is_input_route(rt))
p = &nh->nh_rth_input;
p = (struct rtable **)&nh->nh_rth_input;
orig = *p;
rt->dst.flags |= DST_RCU_FREE;
dst_hold(&rt->dst);
prev = cmpxchg(p, orig, rt);
if (prev == orig) {
if (orig)
dst_release(&orig->dst);
rt_free(orig);
} else {
dst_release(&rt->dst);
/* Routes we intend to cache in the FIB nexthop have
* the DST_NOCACHE bit clear. However, if we are
* unsuccessful at storing this route into the cache
* we really need to set it.
*/
rt->dst.flags |= DST_NOCACHE;
}
}
@ -1412,7 +1420,7 @@ static int __mkroute_input(struct sk_buff *skb,
do_cache = false;
if (res->fi) {
if (!itag) {
rth = FIB_RES_NH(*res).nh_rth_input;
rth = rcu_dereference(FIB_RES_NH(*res).nh_rth_input);
if (rt_cache_valid(rth)) {
skb_dst_set_noref(skb, &rth->dst);
goto out;
@ -1574,7 +1582,7 @@ local_input:
do_cache = false;
if (res.fi) {
if (!itag) {
rth = FIB_RES_NH(res).nh_rth_input;
rth = rcu_dereference(FIB_RES_NH(res).nh_rth_input);
if (rt_cache_valid(rth)) {
skb_dst_set_noref(skb, &rth->dst);
err = 0;
@ -1742,7 +1750,7 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
if (fi) {
fnhe = find_exception(&FIB_RES_NH(*res), fl4->daddr);
if (!fnhe) {
rth = FIB_RES_NH(*res).nh_rth_output;
rth = rcu_dereference(FIB_RES_NH(*res).nh_rth_output);
if (rt_cache_valid(rth)) {
dst_hold(&rth->dst);
return rth;