On Fri, 2015-06-19 at 12:40 +0200, Pablo Neira Ayuso wrote:
> This patch converts the existing seqlock to per-cpu counters.
>
> Suggested-by: Patrick McHardy <kaber@xxxxxxxxx>
> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> ---
> net/netfilter/nft_counter.c | 97 ++++++++++++++++++++++++++++++-------------
> 1 file changed, 69 insertions(+), 28 deletions(-)
>
> diff --git a/net/netfilter/nft_counter.c b/net/netfilter/nft_counter.c
> index 1759123..84b22d8 100644
> --- a/net/netfilter/nft_counter.c
> +++ b/net/netfilter/nft_counter.c
> @@ -18,40 +18,58 @@
> #include <net/netfilter/nf_tables.h>
>
> struct nft_counter {
> - seqlock_t lock;
> u64 bytes;
> 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;
> +};
> +
> static void nft_counter_eval(const struct nft_expr *expr,
> struct nft_regs *regs,
> const struct nft_pktinfo *pkt)
> {
> - struct nft_counter *priv = nft_expr_priv(expr);
> -
> - write_seqlock_bh(&priv->lock);
> - priv->bytes += pkt->skb->len;
> - priv->packets++;
> - write_sequnlock_bh(&priv->lock);
> + struct nft_counter_percpu_priv *priv = nft_expr_priv(expr);
> + struct nft_counter_percpu *this_cpu;
> +
> + this_cpu = this_cpu_ptr(priv->counter);
> + u64_stats_update_begin(&this_cpu->syncp);
This is suspect : You had _bh() before this patch, so are you sure BH
are disabled at this point ?
Otherwise you could have reentrancy problem and lose a syncp update and
hang a reader forever.
> + this_cpu->counter.bytes += pkt->skb->len;
> + this_cpu->counter.packets++;
> + u64_stats_update_end(&this_cpu->syncp);
> }
>
> static int nft_counter_dump(struct sk_buff *skb, const struct nft_expr *expr)
> {
> - struct nft_counter *priv = nft_expr_priv(expr);
> + struct nft_counter_percpu_priv *priv = nft_expr_priv(expr);
> + struct nft_counter_percpu *cpu_stats;
> + struct nft_counter total;
> + u64 bytes, packets;
> unsigned int seq;
> - u64 bytes;
> - u64 packets;
> -
> - do {
> - seq = read_seqbegin(&priv->lock);
> - bytes = priv->bytes;
> - packets = priv->packets;
> - } while (read_seqretry(&priv->lock, seq));
> -
> - if (nla_put_be64(skb, NFTA_COUNTER_BYTES, cpu_to_be64(bytes)))
> - goto nla_put_failure;
> - if (nla_put_be64(skb, NFTA_COUNTER_PACKETS, cpu_to_be64(packets)))
> + int cpu;
> +
> + memset(&total, 0, sizeof(total));
> + for_each_possible_cpu(cpu) {
> + cpu_stats = 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;
> + }
> +
--
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