Dump and reset doesn't work unless cmpxchg64() is used both from both
packet and control plane paths. This approach is going to be slow
though. Instead, use a percpu seqcount to fetch counters consistently,
then subtract bytes and packets in case a reset was requested.
This patch is based on original sketch from Eric Dumazet.
Suggested-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Fixes: 43da04a593d8 ("netfilter: nf_tables: atomic dump and reset for stateful objects")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/netfilter/nft_counter.c | 128 ++++++++++++++++++--------------------------
1 file changed, 51 insertions(+), 77 deletions(-)
diff --git a/net/netfilter/nft_counter.c b/net/netfilter/nft_counter.c
index f6a02c5071c2..c37983d0a141 100644
--- a/net/netfilter/nft_counter.c
+++ b/net/netfilter/nft_counter.c
@@ -22,27 +22,29 @@ struct nft_counter {
u64 packets;
};
-struct nft_counter_percpu {
- struct nft_counter counter;
- struct u64_stats_sync syncp;
-};
-
struct nft_counter_percpu_priv {
- struct nft_counter_percpu __percpu *counter;
+ struct nft_counter __percpu *counter;
};
+static DEFINE_PER_CPU(seqcount_t, nft_counter_seq);
+
static inline void nft_counter_do_eval(struct nft_counter_percpu_priv *priv,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
- struct nft_counter_percpu *this_cpu;
+ struct nft_counter *this_cpu;
+ seqcount_t *myseq;
local_bh_disable();
this_cpu = this_cpu_ptr(priv->counter);
- u64_stats_update_begin(&this_cpu->syncp);
- this_cpu->counter.bytes += pkt->skb->len;
- this_cpu->counter.packets++;
- u64_stats_update_end(&this_cpu->syncp);
+ myseq = this_cpu_ptr(&nft_counter_seq);
+
+ write_seqcount_begin(myseq);
+
+ this_cpu->bytes += pkt->skb->len;
+ this_cpu->packets++;
+
+ write_seqcount_end(myseq);
local_bh_enable();
}
@@ -58,21 +60,21 @@ static inline void nft_counter_obj_eval(struct nft_object *obj,
static int nft_counter_do_init(const struct nlattr * const tb[],
struct nft_counter_percpu_priv *priv)
{
- struct nft_counter_percpu __percpu *cpu_stats;
- struct nft_counter_percpu *this_cpu;
+ struct nft_counter __percpu *cpu_stats;
+ struct nft_counter *this_cpu;
- cpu_stats = netdev_alloc_pcpu_stats(struct nft_counter_percpu);
+ cpu_stats = alloc_percpu(struct nft_counter);
if (cpu_stats == NULL)
return -ENOMEM;
preempt_disable();
this_cpu = this_cpu_ptr(cpu_stats);
if (tb[NFTA_COUNTER_PACKETS]) {
- this_cpu->counter.packets =
+ this_cpu->packets =
be64_to_cpu(nla_get_be64(tb[NFTA_COUNTER_PACKETS]));
}
if (tb[NFTA_COUNTER_BYTES]) {
- this_cpu->counter.bytes =
+ this_cpu->bytes =
be64_to_cpu(nla_get_be64(tb[NFTA_COUNTER_BYTES]));
}
preempt_enable();
@@ -100,74 +102,44 @@ static void nft_counter_obj_destroy(struct nft_object *obj)
nft_counter_do_destroy(priv);
}
-static void nft_counter_fetch(struct nft_counter_percpu __percpu *counter,
- struct nft_counter *total)
+static void nft_counter_fetch(struct nft_counter_percpu_priv *priv,
+ struct nft_counter *total, bool reset)
{
- struct nft_counter_percpu *cpu_stats;
+ struct nft_counter *this_cpu;
+ const seqcount_t *myseq;
u64 bytes, packets;
unsigned int seq;
int cpu;
memset(total, 0, sizeof(*total));
for_each_possible_cpu(cpu) {
- cpu_stats = per_cpu_ptr(counter, cpu);
+ myseq = per_cpu_ptr(&nft_counter_seq, cpu);
+ this_cpu = per_cpu_ptr(priv->counter, cpu);
do {
- seq = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
- bytes = cpu_stats->counter.bytes;
- packets = cpu_stats->counter.packets;
- } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, seq));
-
- total->packets += packets;
- total->bytes += bytes;
- }
-}
-
-static u64 __nft_counter_reset(u64 *counter)
-{
- u64 ret, old;
-
- do {
- old = *counter;
- ret = cmpxchg64(counter, old, 0);
- } while (ret != old);
-
- return ret;
-}
-
-static void nft_counter_reset(struct nft_counter_percpu __percpu *counter,
- struct nft_counter *total)
-{
- struct nft_counter_percpu *cpu_stats;
- u64 bytes, packets;
- unsigned int seq;
- int cpu;
-
- memset(total, 0, sizeof(*total));
- for_each_possible_cpu(cpu) {
- bytes = packets = 0;
-
- cpu_stats = per_cpu_ptr(counter, cpu);
- do {
- seq = u64_stats_fetch_begin_irq(&cpu_stats->syncp);
- packets += __nft_counter_reset(&cpu_stats->counter.packets);
- bytes += __nft_counter_reset(&cpu_stats->counter.bytes);
- } while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, seq));
-
- total->packets += packets;
- total->bytes += bytes;
+ seq = read_seqcount_begin(myseq);
+ bytes = this_cpu->bytes;
+ packets = this_cpu->packets;
+ } while (read_seqcount_retry(myseq, seq));
+
+ total->bytes += bytes;
+ total->packets += packets;
+
+ if (reset) {
+ local_bh_disable();
+ this_cpu->packets -= packets;
+ this_cpu->bytes -= bytes;
+ local_bh_enable();
+ }
}
}
static int nft_counter_do_dump(struct sk_buff *skb,
- const struct nft_counter_percpu_priv *priv,
+ struct nft_counter_percpu_priv *priv,
bool reset)
{
struct nft_counter total;
- if (reset)
- nft_counter_reset(priv->counter, &total);
- else
- nft_counter_fetch(priv->counter, &total);
+ nft_counter_fetch(priv, &total, reset);
if (nla_put_be64(skb, NFTA_COUNTER_BYTES, cpu_to_be64(total.bytes),
NFTA_COUNTER_PAD) ||
@@ -216,7 +188,7 @@ static void nft_counter_eval(const struct nft_expr *expr,
static int nft_counter_dump(struct sk_buff *skb, const struct nft_expr *expr)
{
- const struct nft_counter_percpu_priv *priv = nft_expr_priv(expr);
+ struct nft_counter_percpu_priv *priv = nft_expr_priv(expr);
return nft_counter_do_dump(skb, priv, false);
}
@@ -242,21 +214,20 @@ static int nft_counter_clone(struct nft_expr *dst, const struct nft_expr *src)
{
struct nft_counter_percpu_priv *priv = nft_expr_priv(src);
struct nft_counter_percpu_priv *priv_clone = nft_expr_priv(dst);
- struct nft_counter_percpu __percpu *cpu_stats;
- struct nft_counter_percpu *this_cpu;
+ struct nft_counter __percpu *cpu_stats;
+ struct nft_counter *this_cpu;
struct nft_counter total;
- nft_counter_fetch(priv->counter, &total);
+ nft_counter_fetch(priv, &total, false);
- cpu_stats = __netdev_alloc_pcpu_stats(struct nft_counter_percpu,
- GFP_ATOMIC);
+ cpu_stats = alloc_percpu_gfp(struct nft_counter, GFP_ATOMIC);
if (cpu_stats == NULL)
return -ENOMEM;
preempt_disable();
this_cpu = this_cpu_ptr(cpu_stats);
- this_cpu->counter.packets = total.packets;
- this_cpu->counter.bytes = total.bytes;
+ this_cpu->packets = total.packets;
+ this_cpu->bytes = total.bytes;
preempt_enable();
priv_clone->counter = cpu_stats;
@@ -285,7 +256,10 @@ static struct nft_expr_type nft_counter_type __read_mostly = {
static int __init nft_counter_module_init(void)
{
- int err;
+ int cpu, err;
+
+ for_each_possible_cpu(cpu)
+ seqcount_init(per_cpu_ptr(&nft_counter_seq, cpu));
err = nft_register_obj(&nft_counter_obj);
if (err < 0)
--
2.1.4
--
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