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Date: Tue, 09 Sep 2014 06:27:01 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: John Fastabend <john.fastabend@...il.com>
Cc: xiyou.wangcong@...il.com, davem@...emloft.net, jhs@...atatu.com,
netdev@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
brouer@...hat.com
Subject: Re: [net-next PATCH v3 10/15] net: sched: rcu'ify cls_rsvp
On Mon, 2014-09-08 at 22:58 -0700, John Fastabend wrote:
> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
> ---
> net/sched/cls_rsvp.h | 155 +++++++++++++++++++++++++++++---------------------
> 1 file changed, 89 insertions(+), 66 deletions(-)
>
> diff --git a/net/sched/cls_rsvp.h b/net/sched/cls_rsvp.h
> index 1020e23..8a35bdc 100644
> --- a/net/sched/cls_rsvp.h
> +++ b/net/sched/cls_rsvp.h
> @@ -70,31 +70,34 @@ struct rsvp_head {
> u32 tmap[256/32];
> u32 hgenerator;
> u8 tgenerator;
> - struct rsvp_session *ht[256];
> + struct rsvp_session __rcu *ht[256];
> + struct rcu_head rcu;
> };
>
> struct rsvp_session {
> - struct rsvp_session *next;
> - __be32 dst[RSVP_DST_LEN];
> - struct tc_rsvp_gpi dpi;
> - u8 protocol;
> - u8 tunnelid;
> + struct rsvp_session __rcu *next;
> + __be32 dst[RSVP_DST_LEN];
> + struct tc_rsvp_gpi dpi;
> + u8 protocol;
> + u8 tunnelid;
> /* 16 (src,sport) hash slots, and one wildcard source slot */
> - struct rsvp_filter *ht[16 + 1];
> + struct rsvp_filter __rcu *ht[16 + 1];
> + struct rcu_head rcu;
> };
>
>
> struct rsvp_filter {
> - struct rsvp_filter *next;
> - __be32 src[RSVP_DST_LEN];
> - struct tc_rsvp_gpi spi;
> - u8 tunnelhdr;
> + struct rsvp_filter __rcu *next;
> + __be32 src[RSVP_DST_LEN];
> + struct tc_rsvp_gpi spi;
> + u8 tunnelhdr;
>
> - struct tcf_result res;
> - struct tcf_exts exts;
> + struct tcf_result res;
> + struct tcf_exts exts;
>
> - u32 handle;
> - struct rsvp_session *sess;
> + u32 handle;
> + struct rsvp_session *sess;
> + struct rcu_head rcu;
> };
>
> static inline unsigned int hash_dst(__be32 *dst, u8 protocol, u8 tunnelid)
> @@ -128,7 +131,7 @@ static inline unsigned int hash_src(__be32 *src)
> static int rsvp_classify(struct sk_buff *skb, const struct tcf_proto *tp,
> struct tcf_result *res)
> {
> - struct rsvp_session **sht = ((struct rsvp_head *)tp->root)->ht;
> + struct rsvp_head *head = rcu_dereference_bh(tp->root);
> struct rsvp_session *s;
> struct rsvp_filter *f;
> unsigned int h1, h2;
> @@ -169,7 +172,8 @@ restart:
> h1 = hash_dst(dst, protocol, tunnelid);
> h2 = hash_src(src);
>
> - for (s = sht[h1]; s; s = s->next) {
> + for (s = rcu_dereference_bh(head->ht[h1]); s;
> + s = rcu_dereference_bh(s->next)) {
> if (dst[RSVP_DST_LEN-1] == s->dst[RSVP_DST_LEN - 1] &&
> protocol == s->protocol &&
> !(s->dpi.mask &
> @@ -181,7 +185,8 @@ restart:
> #endif
> tunnelid == s->tunnelid) {
>
> - for (f = s->ht[h2]; f; f = f->next) {
> + for (f = rcu_dereference_bh(s->ht[h2]); f;
> + f = rcu_dereference_bh(f->next)) {
> if (src[RSVP_DST_LEN-1] == f->src[RSVP_DST_LEN - 1] &&
> !(f->spi.mask & (*(u32 *)(xprt + f->spi.offset) ^ f->spi.key))
> #if RSVP_DST_LEN == 4
> @@ -205,7 +210,8 @@ matched:
> }
>
> /* And wildcard bucket... */
> - for (f = s->ht[16]; f; f = f->next) {
> + for (f = rcu_dereference_bh(s->ht[16]); f;
> + f = rcu_dereference_bh(f->next)) {
> *res = f->res;
> RSVP_APPLY_RESULT();
> goto matched;
> @@ -218,7 +224,7 @@ matched:
>
> static unsigned long rsvp_get(struct tcf_proto *tp, u32 handle)
> {
> - struct rsvp_session **sht = ((struct rsvp_head *)tp->root)->ht;
> + struct rsvp_head *head = rtnl_dereference(tp->root);
> struct rsvp_session *s;
> struct rsvp_filter *f;
> unsigned int h1 = handle & 0xFF;
> @@ -227,8 +233,10 @@ static unsigned long rsvp_get(struct tcf_proto *tp, u32 handle)
> if (h2 > 16)
> return 0;
>
> - for (s = sht[h1]; s; s = s->next) {
> - for (f = s->ht[h2]; f; f = f->next) {
> + for (s = rtnl_dereference(head->ht[h1]); s;
> + s = rtnl_dereference(s->next)) {
> + for (f = rtnl_dereference(s->ht[h2]); f;
> + f = rtnl_dereference(f->next)) {
> if (f->handle == handle)
> return (unsigned long)f;
> }
> @@ -246,7 +254,7 @@ static int rsvp_init(struct tcf_proto *tp)
>
> data = kzalloc(sizeof(struct rsvp_head), GFP_KERNEL);
> if (data) {
> - tp->root = data;
> + rcu_assign_pointer(tp->root, data);
> return 0;
> }
> return -ENOBUFS;
> @@ -257,53 +265,55 @@ rsvp_delete_filter(struct tcf_proto *tp, struct rsvp_filter *f)
> {
> tcf_unbind_filter(tp, &f->res);
> tcf_exts_destroy(tp, &f->exts);
> - kfree(f);
> + kfree_rcu(f, rcu);
> }
>
> static void rsvp_destroy(struct tcf_proto *tp)
> {
> - struct rsvp_head *data = xchg(&tp->root, NULL);
> - struct rsvp_session **sht;
> + struct rsvp_head *data = rtnl_dereference(tp->root);
> int h1, h2;
>
> if (data == NULL)
> return;
>
> - sht = data->ht;
> + RCU_INIT_POINTER(tp->root, NULL);
>
> for (h1 = 0; h1 < 256; h1++) {
> struct rsvp_session *s;
>
> - while ((s = sht[h1]) != NULL) {
> - sht[h1] = s->next;
> + while ((s = rtnl_dereference(data->ht[h1])) != NULL) {
> + rcu_assign_pointer(data->ht[h1], s->next);
RCU_INIT_POINTER()
>
> for (h2 = 0; h2 <= 16; h2++) {
> struct rsvp_filter *f;
>
> - while ((f = s->ht[h2]) != NULL) {
> - s->ht[h2] = f->next;
> + while ((f = rtnl_dereference(s->ht[h2])) != NULL) {
> + rcu_assign_pointer(s->ht[h2], f->next);
> rsvp_delete_filter(tp, f);
> }
> }
> - kfree(s);
> + kfree_rcu(s, rcu);
> }
> }
> - kfree(data);
> + RCU_INIT_POINTER(tp->root, NULL);
> + kfree_rcu(data, rcu);
> }
>
> static int rsvp_delete(struct tcf_proto *tp, unsigned long arg)
> {
> - struct rsvp_filter **fp, *f = (struct rsvp_filter *)arg;
> + struct rsvp_head *head = rtnl_dereference(tp->root);
> + struct rsvp_filter *nfp, *f = (struct rsvp_filter *)arg;
> + struct rsvp_filter __rcu **fp;
> unsigned int h = f->handle;
> - struct rsvp_session **sp;
> - struct rsvp_session *s = f->sess;
> + struct rsvp_session __rcu **sp;
> + struct rsvp_session *nsp, *s = f->sess;
> int i;
>
> - for (fp = &s->ht[(h >> 8) & 0xFF]; *fp; fp = &(*fp)->next) {
> - if (*fp == f) {
> - tcf_tree_lock(tp);
> + fp = &s->ht[(h >> 8) & 0xFF];
> + for (nfp = rtnl_dereference(*fp); nfp;
> + fp = &nfp->next, nfp = rtnl_dereference(*fp)) {
> + if (nfp == f) {
> *fp = f->next;
> - tcf_tree_unlock(tp);
> rsvp_delete_filter(tp, f);
>
> /* Strip tree */
> @@ -313,14 +323,12 @@ static int rsvp_delete(struct tcf_proto *tp, unsigned long arg)
> return 0;
>
> /* OK, session has no flows */
> - for (sp = &((struct rsvp_head *)tp->root)->ht[h & 0xFF];
> - *sp; sp = &(*sp)->next) {
> - if (*sp == s) {
> - tcf_tree_lock(tp);
> + sp = &head->ht[h & 0xFF];
> + for (nsp = rtnl_dereference(*sp); nsp;
> + sp = &nsp->next, nsp = rtnl_dereference(*sp)) {
> + if (nsp == s) {
> *sp = s->next;
> - tcf_tree_unlock(tp);
> -
> - kfree(s);
> + kfree_rcu(s, rcu);
> return 0;
> }
> }
> @@ -333,7 +341,7 @@ static int rsvp_delete(struct tcf_proto *tp, unsigned long arg)
>
> static unsigned int gen_handle(struct tcf_proto *tp, unsigned salt)
> {
> - struct rsvp_head *data = tp->root;
> + struct rsvp_head *data = rtnl_dereference(tp->root);
> int i = 0xFFFF;
>
> while (i-- > 0) {
> @@ -361,7 +369,7 @@ static int tunnel_bts(struct rsvp_head *data)
>
> static void tunnel_recycle(struct rsvp_head *data)
> {
> - struct rsvp_session **sht = data->ht;
> + struct rsvp_session __rcu **sht = data->ht;
> u32 tmap[256/32];
> int h1, h2;
>
> @@ -369,11 +377,13 @@ static void tunnel_recycle(struct rsvp_head *data)
>
> for (h1 = 0; h1 < 256; h1++) {
> struct rsvp_session *s;
> - for (s = sht[h1]; s; s = s->next) {
> + for (s = rtnl_dereference(sht[h1]); s;
> + s = rtnl_dereference(s->next)) {
> for (h2 = 0; h2 <= 16; h2++) {
> struct rsvp_filter *f;
>
> - for (f = s->ht[h2]; f; f = f->next) {
> + for (f = rtnl_dereference(s->ht[h2]); f;
> + f = rtnl_dereference(f->next)) {
> if (f->tunnelhdr == 0)
> continue;
> data->tgenerator = f->res.classid;
> @@ -417,9 +427,11 @@ static int rsvp_change(struct net *net, struct sk_buff *in_skb,
> struct nlattr **tca,
> unsigned long *arg, bool ovr)
> {
> - struct rsvp_head *data = tp->root;
> - struct rsvp_filter *f, **fp;
> - struct rsvp_session *s, **sp;
> + struct rsvp_head *data = rtnl_dereference(tp->root);
> + struct rsvp_filter *f, *nfp;
> + struct rsvp_filter __rcu **fp;
> + struct rsvp_session *nsp, *s;
> + struct rsvp_session __rcu **sp;
> struct tc_rsvp_pinfo *pinfo = NULL;
> struct nlattr *opt = tca[TCA_OPTIONS];
> struct nlattr *tb[TCA_RSVP_MAX + 1];
> @@ -499,7 +511,9 @@ static int rsvp_change(struct net *net, struct sk_buff *in_skb,
> goto errout;
> }
>
> - for (sp = &data->ht[h1]; (s = *sp) != NULL; sp = &s->next) {
> + for (sp = &data->ht[h1];
> + (s = rtnl_dereference(*sp)) != NULL;
> + sp = &s->next) {
> if (dst[RSVP_DST_LEN-1] == s->dst[RSVP_DST_LEN-1] &&
> pinfo && pinfo->protocol == s->protocol &&
> memcmp(&pinfo->dpi, &s->dpi, sizeof(s->dpi)) == 0 &&
> @@ -521,12 +535,17 @@ insert:
>
> tcf_exts_change(tp, &f->exts, &e);
>
> - for (fp = &s->ht[h2]; *fp; fp = &(*fp)->next)
> - if (((*fp)->spi.mask & f->spi.mask) != f->spi.mask)
> + fp = &s->ht[h2];
> + for (nfp = rtnl_dereference(*fp); nfp;
> + fp = &nfp->next, nfp = rtnl_dereference(*fp)) {
> + __u32 mask = nfp->spi.mask & f->spi.mask;
> +
> + if (mask != f->spi.mask)
> break;
> - f->next = *fp;
> + }
> + rcu_assign_pointer(f->next, nfp);
RCU_INIT_POINTER()
> wmb();
Are you sure we need to keep this wmb() ? I dont think so.
> - *fp = f;
> + rcu_assign_pointer(*fp, f);
>
> *arg = (unsigned long)f;
> return 0;
> @@ -546,13 +565,15 @@ insert:
> s->protocol = pinfo->protocol;
> s->tunnelid = pinfo->tunnelid;
> }
> - for (sp = &data->ht[h1]; *sp; sp = &(*sp)->next) {
> - if (((*sp)->dpi.mask&s->dpi.mask) != s->dpi.mask)
> + sp = &data->ht[h1];
> + for (nsp = rtnl_dereference(*sp); nsp;
> + sp = &nsp->next, nsp = rtnl_dereference(*sp)) {
> + if ((nsp->dpi.mask & s->dpi.mask) != s->dpi.mask)
> break;
> }
> - s->next = *sp;
> + rcu_assign_pointer(s->next, nsp);
RCU_INIT_POINTER()
> wmb();
This wmb() can be removed.
> - *sp = s;
> + rcu_assign_pointer(*sp, s);
>
> goto insert;
>
> @@ -565,7 +586,7 @@ errout2:
>
> static void rsvp_walk(struct tcf_proto *tp, struct tcf_walker *arg)
> {
> - struct rsvp_head *head = tp->root;
> + struct rsvp_head *head = rtnl_dereference(tp->root);
> unsigned int h, h1;
>
> if (arg->stop)
> @@ -574,11 +595,13 @@ static void rsvp_walk(struct tcf_proto *tp, struct tcf_walker *arg)
> for (h = 0; h < 256; h++) {
> struct rsvp_session *s;
>
> - for (s = head->ht[h]; s; s = s->next) {
> + for (s = rtnl_dereference(head->ht[h]); s;
> + s = rtnl_dereference(s->next)) {
> for (h1 = 0; h1 <= 16; h1++) {
> struct rsvp_filter *f;
>
> - for (f = s->ht[h1]; f; f = f->next) {
> + for (f = rtnl_dereference(s->ht[h1]); f;
> + f = rtnl_dereference(f->next)) {
> if (arg->count < arg->skip) {
> arg->count++;
> continue;
>
Thanks !
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