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net: sched: rcu'ify cls_bpf
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This patch makes the cls_bpf classifier RCU safe. The tcf_lock
was being used to protect a list of cls_bpf_prog now this list
is RCU safe and updates occur with rcu_replace.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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John Fastabend authored and David S. Miller committed Sep 13, 2014
1 parent 8b21e23 commit d355ab0
Showing 1 changed file with 47 additions and 47 deletions.
94 changes: 47 additions & 47 deletions net/sched/cls_bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ MODULE_DESCRIPTION("TC BPF based classifier");
struct cls_bpf_head {
struct list_head plist;
u32 hgen;
struct rcu_head rcu;
};

struct cls_bpf_prog {
Expand All @@ -37,6 +38,8 @@ struct cls_bpf_prog {
struct list_head link;
u32 handle;
u16 bpf_len;
struct tcf_proto *tp;
struct rcu_head rcu;
};

static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
Expand All @@ -49,11 +52,11 @@ static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_head *head = rcu_dereference(tp->root);
struct cls_bpf_prog *prog;
int ret;

list_for_each_entry(prog, &head->plist, link) {
list_for_each_entry_rcu(prog, &head->plist, link) {
int filter_res = BPF_PROG_RUN(prog->filter, skb);

if (filter_res == 0)
Expand Down Expand Up @@ -81,8 +84,8 @@ static int cls_bpf_init(struct tcf_proto *tp)
if (head == NULL)
return -ENOBUFS;

INIT_LIST_HEAD(&head->plist);
tp->root = head;
INIT_LIST_HEAD_RCU(&head->plist);
rcu_assign_pointer(tp->root, head);

return 0;
}
Expand All @@ -98,18 +101,22 @@ static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
kfree(prog);
}

static void __cls_bpf_delete_prog(struct rcu_head *rcu)
{
struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu);

cls_bpf_delete_prog(prog->tp, prog);
}

static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *prog, *todel = (struct cls_bpf_prog *) arg;

list_for_each_entry(prog, &head->plist, link) {
if (prog == todel) {
tcf_tree_lock(tp);
list_del(&prog->link);
tcf_tree_unlock(tp);

cls_bpf_delete_prog(tp, prog);
list_del_rcu(&prog->link);
call_rcu(&prog->rcu, __cls_bpf_delete_prog);
return 0;
}
}
Expand All @@ -119,27 +126,28 @@ static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)

static void cls_bpf_destroy(struct tcf_proto *tp)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *prog, *tmp;

list_for_each_entry_safe(prog, tmp, &head->plist, link) {
list_del(&prog->link);
cls_bpf_delete_prog(tp, prog);
list_del_rcu(&prog->link);
call_rcu(&prog->rcu, __cls_bpf_delete_prog);
}

kfree(head);
RCU_INIT_POINTER(tp->root, NULL);
kfree_rcu(head, rcu);
}

static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *prog;
unsigned long ret = 0UL;

if (head == NULL)
return 0UL;

list_for_each_entry(prog, &head->plist, link) {
list_for_each_entry_rcu(prog, &head->plist, link) {
if (prog->handle == handle) {
ret = (unsigned long) prog;
break;
Expand All @@ -158,10 +166,10 @@ static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
unsigned long base, struct nlattr **tb,
struct nlattr *est, bool ovr)
{
struct sock_filter *bpf_ops, *bpf_old;
struct sock_filter *bpf_ops;
struct tcf_exts exts;
struct sock_fprog_kern tmp;
struct bpf_prog *fp, *fp_old;
struct bpf_prog *fp;
u16 bpf_size, bpf_len;
u32 classid;
int ret;
Expand Down Expand Up @@ -197,26 +205,15 @@ static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
if (ret)
goto errout_free;

tcf_tree_lock(tp);
fp_old = prog->filter;
bpf_old = prog->bpf_ops;

prog->bpf_len = bpf_len;
prog->bpf_ops = bpf_ops;
prog->filter = fp;
prog->res.classid = classid;
tcf_tree_unlock(tp);

tcf_bind_filter(tp, &prog->res, base);
tcf_exts_change(tp, &prog->exts, &exts);

if (fp_old)
bpf_prog_destroy(fp_old);
if (bpf_old)
kfree(bpf_old);

return 0;

errout_free:
kfree(bpf_ops);
errout:
Expand Down Expand Up @@ -244,9 +241,10 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
u32 handle, struct nlattr **tca,
unsigned long *arg, bool ovr)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog = (struct cls_bpf_prog *) *arg;
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *oldprog = (struct cls_bpf_prog *) *arg;
struct nlattr *tb[TCA_BPF_MAX + 1];
struct cls_bpf_prog *prog;
int ret;

if (tca[TCA_OPTIONS] == NULL)
Expand All @@ -256,18 +254,19 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
if (ret < 0)
return ret;

if (prog != NULL) {
if (handle && prog->handle != handle)
return -EINVAL;
return cls_bpf_modify_existing(net, tp, prog, base, tb,
tca[TCA_RATE], ovr);
}

prog = kzalloc(sizeof(*prog), GFP_KERNEL);
if (prog == NULL)
if (!prog)
return -ENOBUFS;

tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);

if (oldprog) {
if (handle && oldprog->handle != handle) {
ret = -EINVAL;
goto errout;
}
}

if (handle == 0)
prog->handle = cls_bpf_grab_new_handle(tp, head);
else
Expand All @@ -281,16 +280,17 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
if (ret < 0)
goto errout;

tcf_tree_lock(tp);
list_add(&prog->link, &head->plist);
tcf_tree_unlock(tp);
if (oldprog) {
list_replace_rcu(&prog->link, &oldprog->link);
call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
} else {
list_add_rcu(&prog->link, &head->plist);
}

*arg = (unsigned long) prog;

return 0;
errout:
if (*arg == 0UL && prog)
kfree(prog);
kfree(prog);

return ret;
}
Expand Down Expand Up @@ -339,10 +339,10 @@ static int cls_bpf_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,

static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *prog;

list_for_each_entry(prog, &head->plist, link) {
list_for_each_entry_rcu(prog, &head->plist, link) {
if (arg->count < arg->skip)
goto skip;
if (arg->fn(tp, (unsigned long) prog, arg) < 0) {
Expand Down

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