On Mon, 2013-05-27 at 10:44 +0300, Eliezer Tamir wrote:
> Adds a napi_id and a hashing mechanism to lookup a napi by id.
> This will be used by subsequent patches to implement low latency
> Ethernet device polling.
> Based on a code sample by Eric Dumazet.
>
> Signed-off-by: Eliezer Tamir <eliezer.ta...@linux.intel.com>
> ---
>
> include/linux/netdevice.h | 29 +++++++++++++++++++++++++++++
> net/core/dev.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 73 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index ea7b6bc..d1ec8b1 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -324,12 +324,15 @@ struct napi_struct {
> struct sk_buff *gro_list;
> struct sk_buff *skb;
> struct list_head dev_list;
> + struct hlist_node napi_hash_node;
> + int napi_id;
> };
>
> enum {
> NAPI_STATE_SCHED, /* Poll is scheduled */
> NAPI_STATE_DISABLE, /* Disable pending */
> NAPI_STATE_NPSVC, /* Netpoll - don't dequeue from poll_list */
> + NAPI_STATE_HASHED, /* In NAPI hash */
> };
>
> enum gro_result {
> @@ -446,6 +449,32 @@ extern void __napi_complete(struct napi_struct *n);
> extern void napi_complete(struct napi_struct *n);
>
> /**
> + * napi_hash_add - add a NAPI to global hashtable
> + * @napi: napi context
> + *
> + * generate a new napi_id and store a @napi under it in napi_hash
> + */
> +extern void napi_hash_add(struct napi_struct *napi);
> +
> +/**
> + * napi_hash_del - remove a NAPI from blobal table
global
> + * @napi: napi context
> + *
> + * Warning: caller must observe rcu grace period
> + * before freeing memory containing @NAPI
@napi
> + */
> +extern void napi_hash_del(struct napi_struct *napi);
> +
> +/**
> + * napi_by_is - lookup a NAPI by napi_id
napi_by_id
> + * @napi_id: hashed napi_id
> + *
> + * lookup napi_id in napi_hash table
@napi_id
> + * must be called under rcu_read_lock()
> + */
> +extern struct napi_struct *napi_by_id(int napi_id);
> +
> +/**
> * napi_disable - prevent NAPI from scheduling
> * @n: napi context
> *
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 50c02de..283ab14 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -129,6 +129,7 @@
> #include <linux/inetdevice.h>
> #include <linux/cpu_rmap.h>
> #include <linux/static_key.h>
> +#include <linux/hashtable.h>
>
> #include "net-sysfs.h"
>
> @@ -166,6 +167,10 @@ static struct list_head offload_base __read_mostly;
> DEFINE_RWLOCK(dev_base_lock);
> EXPORT_SYMBOL(dev_base_lock);
>
> +atomic_t napi_gen_id;
Not sure we need an atomic, we are protected by RTNL anyway.
> +
> +DEFINE_HASHTABLE(napi_hash, 8);
> +
> seqcount_t devnet_rename_seq;
>
> static inline void dev_base_seq_inc(struct net *net)
> @@ -4113,6 +4118,45 @@ void napi_complete(struct napi_struct *n)
> }
> EXPORT_SYMBOL(napi_complete);
>
> +void napi_hash_add(struct napi_struct *napi)
> +{
> + if (!test_and_set_bit(NAPI_STATE_HASHED, &napi->state)) {
> +
> + /* 0 is not a valid id */
> + napi->napi_id = 0;
> + while (!napi->napi_id)
> + napi->napi_id = atomic_inc_return(&napi_gen_id);
> +
> + hlist_add_head_rcu(&napi->napi_hash_node,
> + &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
> + }
> +}
> +EXPORT_SYMBOL_GPL(napi_hash_add);
> +
> +/* Warning : caller is responsible to make sure rcu grace period
> + * is respected before freeing memory containing @napi
> + */
> +void napi_hash_del(struct napi_struct *napi)
> +{
> + if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state))
> + hlist_del_rcu(&napi->napi_hash_node);
> +}
> +EXPORT_SYMBOL_GPL(napi_hash_del);
> +
> +/* must be called under rcu_read_lock(), as we dont take a reference */
> +struct napi_struct *napi_by_id(int napi_id)
> +{
> + unsigned int hash = napi_id % HASH_SIZE(napi_hash);
> + struct napi_struct *napi;
> +
> + hlist_for_each_entry_rcu(napi, &napi_hash[hash], napi_hash_node)
> + if (napi->napi_id == napi_id)
> + return napi;
> +
> + return NULL;
> +}
> +EXPORT_SYMBOL_GPL(napi_by_id);
> +
> void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
> int (*poll)(struct napi_struct *, int), int weight)
> {
>
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