netfilter: revised locking for x_tables
The x_tables are organized with a table structure and a per-cpu copies
of the counters and rules. On older kernels there was a reader/writer
lock per table which was a performance bottleneck. In 2.6.30-rc, this
was converted to use RCU and the counters/rules which solved the performance
problems for do_table but made replacing rules much slower because of
the necessary RCU grace period.
This version uses a per-cpu set of spinlocks and counters to allow to
table processing to proceed without the cache thrashing of a global
reader lock and keeps the same performance for table updates.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 810c0b6..2ec8d72 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -338,10 +338,9 @@
tgpar.hooknum = hook;
IP_NF_ASSERT(table->valid_hooks & (1 << hook));
-
- rcu_read_lock_bh();
- private = rcu_dereference(table->private);
- table_base = rcu_dereference(private->entries[smp_processor_id()]);
+ xt_info_rdlock_bh();
+ private = table->private;
+ table_base = private->entries[smp_processor_id()];
e = get_entry(table_base, private->hook_entry[hook]);
@@ -436,8 +435,7 @@
e = (void *)e + e->next_offset;
}
} while (!hotdrop);
-
- rcu_read_unlock_bh();
+ xt_info_rdunlock_bh();
#ifdef DEBUG_ALLOW_ALL
return NF_ACCEPT;
@@ -896,10 +894,13 @@
/* Instead of clearing (by a previous call to memset())
* the counters and using adds, we set the counters
- * with data used by 'current' CPU
- * We dont care about preemption here.
+ * with data used by 'current' CPU.
+ *
+ * Bottom half has to be disabled to prevent deadlock
+ * if new softirq were to run and call ipt_do_table
*/
- curcpu = raw_smp_processor_id();
+ local_bh_disable();
+ curcpu = smp_processor_id();
i = 0;
IPT_ENTRY_ITERATE(t->entries[curcpu],
@@ -912,74 +913,22 @@
if (cpu == curcpu)
continue;
i = 0;
+ xt_info_wrlock(cpu);
IPT_ENTRY_ITERATE(t->entries[cpu],
t->size,
add_entry_to_counter,
counters,
&i);
+ xt_info_wrunlock(cpu);
}
-
-}
-
-/* We're lazy, and add to the first CPU; overflow works its fey magic
- * and everything is OK. */
-static int
-add_counter_to_entry(struct ipt_entry *e,
- const struct xt_counters addme[],
- unsigned int *i)
-{
- ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
-
- (*i)++;
- return 0;
-}
-
-/* Take values from counters and add them back onto the current cpu */
-static void put_counters(struct xt_table_info *t,
- const struct xt_counters counters[])
-{
- unsigned int i, cpu;
-
- local_bh_disable();
- cpu = smp_processor_id();
- i = 0;
- IPT_ENTRY_ITERATE(t->entries[cpu],
- t->size,
- add_counter_to_entry,
- counters,
- &i);
local_bh_enable();
}
-
-static inline int
-zero_entry_counter(struct ipt_entry *e, void *arg)
-{
- e->counters.bcnt = 0;
- e->counters.pcnt = 0;
- return 0;
-}
-
-static void
-clone_counters(struct xt_table_info *newinfo, const struct xt_table_info *info)
-{
- unsigned int cpu;
- const void *loc_cpu_entry = info->entries[raw_smp_processor_id()];
-
- memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
- for_each_possible_cpu(cpu) {
- memcpy(newinfo->entries[cpu], loc_cpu_entry, info->size);
- IPT_ENTRY_ITERATE(newinfo->entries[cpu], newinfo->size,
- zero_entry_counter, NULL);
- }
-}
-
static struct xt_counters * alloc_counters(struct xt_table *table)
{
unsigned int countersize;
struct xt_counters *counters;
struct xt_table_info *private = table->private;
- struct xt_table_info *info;
/* We need atomic snapshot of counters: rest doesn't change
(other than comefrom, which userspace doesn't care
@@ -988,30 +937,11 @@
counters = vmalloc_node(countersize, numa_node_id());
if (counters == NULL)
- goto nomem;
+ return ERR_PTR(-ENOMEM);
- info = xt_alloc_table_info(private->size);
- if (!info)
- goto free_counters;
-
- clone_counters(info, private);
-
- mutex_lock(&table->lock);
- xt_table_entry_swap_rcu(private, info);
- synchronize_net(); /* Wait until smoke has cleared */
-
- get_counters(info, counters);
- put_counters(private, counters);
- mutex_unlock(&table->lock);
-
- xt_free_table_info(info);
+ get_counters(private, counters);
return counters;
-
- free_counters:
- vfree(counters);
- nomem:
- return ERR_PTR(-ENOMEM);
}
static int
@@ -1306,8 +1236,9 @@
(newinfo->number <= oldinfo->initial_entries))
module_put(t->me);
- /* Get the old counters. */
+ /* Get the old counters, and synchronize with replace */
get_counters(oldinfo, counters);
+
/* Decrease module usage counts and free resource */
loc_cpu_old_entry = oldinfo->entries[raw_smp_processor_id()];
IPT_ENTRY_ITERATE(loc_cpu_old_entry, oldinfo->size, cleanup_entry,
@@ -1377,11 +1308,23 @@
return ret;
}
+/* We're lazy, and add to the first CPU; overflow works its fey magic
+ * and everything is OK. */
+static int
+add_counter_to_entry(struct ipt_entry *e,
+ const struct xt_counters addme[],
+ unsigned int *i)
+{
+ ADD_COUNTER(e->counters, addme[*i].bcnt, addme[*i].pcnt);
+
+ (*i)++;
+ return 0;
+}
static int
do_add_counters(struct net *net, void __user *user, unsigned int len, int compat)
{
- unsigned int i;
+ unsigned int i, curcpu;
struct xt_counters_info tmp;
struct xt_counters *paddc;
unsigned int num_counters;
@@ -1437,25 +1380,26 @@
goto free;
}
- mutex_lock(&t->lock);
+ local_bh_disable();
private = t->private;
if (private->number != num_counters) {
ret = -EINVAL;
goto unlock_up_free;
}
- preempt_disable();
i = 0;
/* Choose the copy that is on our node */
- loc_cpu_entry = private->entries[raw_smp_processor_id()];
+ curcpu = smp_processor_id();
+ loc_cpu_entry = private->entries[curcpu];
+ xt_info_wrlock(curcpu);
IPT_ENTRY_ITERATE(loc_cpu_entry,
private->size,
add_counter_to_entry,
paddc,
&i);
- preempt_enable();
+ xt_info_wrunlock(curcpu);
unlock_up_free:
- mutex_unlock(&t->lock);
+ local_bh_enable();
xt_table_unlock(t);
module_put(t->me);
free: