net: sched: RCU cls_tcindex
Make cls_tcindex RCU safe.
This patch addds a new RCU routine rcu_dereference_bh_rtnl() to check
caller either holds the rcu read lock or RTNL. This is needed to
handle the case where tcindex_lookup() is being called in both cases.
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>
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 167bae7..6cacbce 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -47,6 +47,16 @@
rcu_dereference_check(p, lockdep_rtnl_is_held())
/**
+ * rcu_dereference_bh_rtnl - rcu_dereference_bh with debug checking
+ * @p: The pointer to read, prior to dereference
+ *
+ * Do an rcu_dereference_bh(p), but check caller either holds rcu_read_lock_bh()
+ * or RTNL. Note : Please prefer rtnl_dereference() or rcu_dereference_bh()
+ */
+#define rcu_dereference_bh_rtnl(p) \
+ rcu_dereference_bh_check(p, lockdep_rtnl_is_held())
+
+/**
* rtnl_dereference - fetch RCU pointer when updates are prevented by RTNL
* @p: The pointer to read, prior to dereferencing
*
diff --git a/net/sched/cls_tcindex.c b/net/sched/cls_tcindex.c
index 3e9f764..a9f4279 100644
--- a/net/sched/cls_tcindex.c
+++ b/net/sched/cls_tcindex.c
@@ -32,19 +32,21 @@
struct tcindex_filter {
u16 key;
struct tcindex_filter_result result;
- struct tcindex_filter *next;
+ struct tcindex_filter __rcu *next;
+ struct rcu_head rcu;
};
struct tcindex_data {
struct tcindex_filter_result *perfect; /* perfect hash; NULL if none */
- struct tcindex_filter **h; /* imperfect hash; only used if !perfect;
- NULL if unused */
+ struct tcindex_filter __rcu **h; /* imperfect hash; */
+ struct tcf_proto *tp;
u16 mask; /* AND key with mask */
- int shift; /* shift ANDed key to the right */
- int hash; /* hash table size; 0 if undefined */
- int alloc_hash; /* allocated size */
- int fall_through; /* 0: only classify if explicit match */
+ u32 shift; /* shift ANDed key to the right */
+ u32 hash; /* hash table size; 0 if undefined */
+ u32 alloc_hash; /* allocated size */
+ u32 fall_through; /* 0: only classify if explicit match */
+ struct rcu_head rcu;
};
static inline int
@@ -56,13 +58,18 @@
static struct tcindex_filter_result *
tcindex_lookup(struct tcindex_data *p, u16 key)
{
- struct tcindex_filter *f;
+ if (p->perfect) {
+ struct tcindex_filter_result *f = p->perfect + key;
- if (p->perfect)
- return tcindex_filter_is_set(p->perfect + key) ?
- p->perfect + key : NULL;
- else if (p->h) {
- for (f = p->h[key % p->hash]; f; f = f->next)
+ return tcindex_filter_is_set(f) ? f : NULL;
+ } else if (p->h) {
+ struct tcindex_filter __rcu **fp;
+ struct tcindex_filter *f;
+
+ fp = &p->h[key % p->hash];
+ for (f = rcu_dereference_bh_rtnl(*fp);
+ f;
+ fp = &f->next, f = rcu_dereference_bh_rtnl(*fp))
if (f->key == key)
return &f->result;
}
@@ -74,7 +81,7 @@
static int tcindex_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rcu_dereference(tp->root);
struct tcindex_filter_result *f;
int key = (skb->tc_index & p->mask) >> p->shift;
@@ -99,7 +106,7 @@
static unsigned long tcindex_get(struct tcf_proto *tp, u32 handle)
{
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r;
pr_debug("tcindex_get(tp %p,handle 0x%08x)\n", tp, handle);
@@ -129,49 +136,59 @@
p->hash = DEFAULT_HASH_SIZE;
p->fall_through = 1;
- tp->root = p;
+ rcu_assign_pointer(tp->root, p);
return 0;
}
-
static int
-__tcindex_delete(struct tcf_proto *tp, unsigned long arg, int lock)
+tcindex_delete(struct tcf_proto *tp, unsigned long arg)
{
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r = (struct tcindex_filter_result *) arg;
+ struct tcindex_filter __rcu **walk;
struct tcindex_filter *f = NULL;
- pr_debug("tcindex_delete(tp %p,arg 0x%lx),p %p,f %p\n", tp, arg, p, f);
+ pr_debug("tcindex_delete(tp %p,arg 0x%lx),p %p\n", tp, arg, p);
if (p->perfect) {
if (!r->res.class)
return -ENOENT;
} else {
int i;
- struct tcindex_filter **walk = NULL;
- for (i = 0; i < p->hash; i++)
- for (walk = p->h+i; *walk; walk = &(*walk)->next)
- if (&(*walk)->result == r)
+ for (i = 0; i < p->hash; i++) {
+ walk = p->h + i;
+ for (f = rtnl_dereference(*walk); f;
+ walk = &f->next, f = rtnl_dereference(*walk)) {
+ if (&f->result == r)
goto found;
+ }
+ }
return -ENOENT;
found:
- f = *walk;
- if (lock)
- tcf_tree_lock(tp);
- *walk = f->next;
- if (lock)
- tcf_tree_unlock(tp);
+ rcu_assign_pointer(*walk, rtnl_dereference(f->next));
}
tcf_unbind_filter(tp, &r->res);
tcf_exts_destroy(tp, &r->exts);
- kfree(f);
+ if (f)
+ kfree_rcu(f, rcu);
return 0;
}
-static int tcindex_delete(struct tcf_proto *tp, unsigned long arg)
+static int tcindex_destroy_element(struct tcf_proto *tp,
+ unsigned long arg,
+ struct tcf_walker *walker)
{
- return __tcindex_delete(tp, arg, 1);
+ return tcindex_delete(tp, arg);
+}
+
+static void __tcindex_destroy(struct rcu_head *head)
+{
+ struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);
+
+ kfree(p->perfect);
+ kfree(p->h);
+ kfree(p);
}
static inline int
@@ -194,6 +211,14 @@
tcf_exts_init(&r->exts, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
}
+static void __tcindex_partial_destroy(struct rcu_head *head)
+{
+ struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);
+
+ kfree(p->perfect);
+ kfree(p);
+}
+
static int
tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,
u32 handle, struct tcindex_data *p,
@@ -203,7 +228,7 @@
int err, balloc = 0;
struct tcindex_filter_result new_filter_result, *old_r = r;
struct tcindex_filter_result cr;
- struct tcindex_data cp;
+ struct tcindex_data *cp, *oldp;
struct tcindex_filter *f = NULL; /* make gcc behave */
struct tcf_exts e;
@@ -212,84 +237,118 @@
if (err < 0)
return err;
- memcpy(&cp, p, sizeof(cp));
- tcindex_filter_result_init(&new_filter_result);
+ /* tcindex_data attributes must look atomic to classifier/lookup so
+ * allocate new tcindex data and RCU assign it onto root. Keeping
+ * perfect hash and hash pointers from old data.
+ */
+ cp = kzalloc(sizeof(cp), GFP_KERNEL);
+ if (!cp)
+ return -ENOMEM;
+
+ cp->mask = p->mask;
+ cp->shift = p->shift;
+ cp->hash = p->hash;
+ cp->alloc_hash = p->alloc_hash;
+ cp->fall_through = p->fall_through;
+ cp->tp = tp;
+
+ if (p->perfect) {
+ cp->perfect = kmemdup(p->perfect,
+ sizeof(*r) * cp->hash, GFP_KERNEL);
+ if (!cp->perfect)
+ goto errout;
+ }
+ cp->h = p->h;
+
+ memset(&new_filter_result, 0, sizeof(new_filter_result));
+ tcf_exts_init(&new_filter_result.exts,
+ TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
tcindex_filter_result_init(&cr);
if (old_r)
cr.res = r->res;
if (tb[TCA_TCINDEX_HASH])
- cp.hash = nla_get_u32(tb[TCA_TCINDEX_HASH]);
+ cp->hash = nla_get_u32(tb[TCA_TCINDEX_HASH]);
if (tb[TCA_TCINDEX_MASK])
- cp.mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);
+ cp->mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);
if (tb[TCA_TCINDEX_SHIFT])
- cp.shift = nla_get_u32(tb[TCA_TCINDEX_SHIFT]);
+ cp->shift = nla_get_u32(tb[TCA_TCINDEX_SHIFT]);
err = -EBUSY;
+
/* Hash already allocated, make sure that we still meet the
* requirements for the allocated hash.
*/
- if (cp.perfect) {
- if (!valid_perfect_hash(&cp) ||
- cp.hash > cp.alloc_hash)
+ if (cp->perfect) {
+ if (!valid_perfect_hash(cp) ||
+ cp->hash > cp->alloc_hash)
goto errout;
- } else if (cp.h && cp.hash != cp.alloc_hash)
+ } else if (cp->h && cp->hash != cp->alloc_hash) {
goto errout;
+ }
err = -EINVAL;
if (tb[TCA_TCINDEX_FALL_THROUGH])
- cp.fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);
+ cp->fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);
- if (!cp.hash) {
+ if (!cp->hash) {
/* Hash not specified, use perfect hash if the upper limit
* of the hashing index is below the threshold.
*/
- if ((cp.mask >> cp.shift) < PERFECT_HASH_THRESHOLD)
- cp.hash = (cp.mask >> cp.shift) + 1;
+ if ((cp->mask >> cp->shift) < PERFECT_HASH_THRESHOLD)
+ cp->hash = (cp->mask >> cp->shift) + 1;
else
- cp.hash = DEFAULT_HASH_SIZE;
+ cp->hash = DEFAULT_HASH_SIZE;
}
- if (!cp.perfect && !cp.h)
- cp.alloc_hash = cp.hash;
+ if (!cp->perfect && cp->h)
+ cp->alloc_hash = cp->hash;
/* Note: this could be as restrictive as if (handle & ~(mask >> shift))
* but then, we'd fail handles that may become valid after some future
* mask change. While this is extremely unlikely to ever matter,
* the check below is safer (and also more backwards-compatible).
*/
- if (cp.perfect || valid_perfect_hash(&cp))
- if (handle >= cp.alloc_hash)
+ if (cp->perfect || valid_perfect_hash(cp))
+ if (handle >= cp->alloc_hash)
goto errout;
err = -ENOMEM;
- if (!cp.perfect && !cp.h) {
- if (valid_perfect_hash(&cp)) {
+ if (!cp->perfect && !cp->h) {
+ if (valid_perfect_hash(cp)) {
int i;
- cp.perfect = kcalloc(cp.hash, sizeof(*r), GFP_KERNEL);
- if (!cp.perfect)
+ cp->perfect = kcalloc(cp->hash, sizeof(*r), GFP_KERNEL);
+ if (!cp->perfect)
goto errout;
- for (i = 0; i < cp.hash; i++)
- tcf_exts_init(&cp.perfect[i].exts, TCA_TCINDEX_ACT,
+ for (i = 0; i < cp->hash; i++)
+ tcf_exts_init(&cp->perfect[i].exts,
+ TCA_TCINDEX_ACT,
TCA_TCINDEX_POLICE);
balloc = 1;
} else {
- cp.h = kcalloc(cp.hash, sizeof(f), GFP_KERNEL);
- if (!cp.h)
+ struct tcindex_filter __rcu **hash;
+
+ hash = kcalloc(cp->hash,
+ sizeof(struct tcindex_filter *),
+ GFP_KERNEL);
+
+ if (!hash)
goto errout;
+
+ cp->h = hash;
balloc = 2;
}
}
- if (cp.perfect)
- r = cp.perfect + handle;
+ if (cp->perfect)
+ r = cp->perfect + handle;
else
- r = tcindex_lookup(&cp, handle) ? : &new_filter_result;
+ r = tcindex_lookup(cp, handle) ? : &new_filter_result;
if (r == &new_filter_result) {
f = kzalloc(sizeof(*f), GFP_KERNEL);
@@ -307,33 +366,41 @@
else
tcf_exts_change(tp, &cr.exts, &e);
- tcf_tree_lock(tp);
if (old_r && old_r != r)
tcindex_filter_result_init(old_r);
- memcpy(p, &cp, sizeof(cp));
+ oldp = p;
r->res = cr.res;
+ rcu_assign_pointer(tp->root, cp);
if (r == &new_filter_result) {
- struct tcindex_filter **fp;
+ struct tcindex_filter *nfp;
+ struct tcindex_filter __rcu **fp;
f->key = handle;
f->result = new_filter_result;
f->next = NULL;
- for (fp = p->h+(handle % p->hash); *fp; fp = &(*fp)->next)
- /* nothing */;
- *fp = f;
- }
- tcf_tree_unlock(tp);
+ fp = p->h + (handle % p->hash);
+ for (nfp = rtnl_dereference(*fp);
+ nfp;
+ fp = &nfp->next, nfp = rtnl_dereference(*fp))
+ ; /* nothing */
+
+ rcu_assign_pointer(*fp, f);
+ }
+
+ if (oldp)
+ call_rcu(&oldp->rcu, __tcindex_partial_destroy);
return 0;
errout_alloc:
if (balloc == 1)
- kfree(cp.perfect);
+ kfree(cp->perfect);
else if (balloc == 2)
- kfree(cp.h);
+ kfree(cp->h);
errout:
+ kfree(cp);
tcf_exts_destroy(tp, &e);
return err;
}
@@ -345,7 +412,7 @@
{
struct nlattr *opt = tca[TCA_OPTIONS];
struct nlattr *tb[TCA_TCINDEX_MAX + 1];
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r = (struct tcindex_filter_result *) *arg;
int err;
@@ -364,10 +431,9 @@
tca[TCA_RATE], ovr);
}
-
static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker)
{
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter *f, *next;
int i;
@@ -390,8 +456,8 @@
if (!p->h)
return;
for (i = 0; i < p->hash; i++) {
- for (f = p->h[i]; f; f = next) {
- next = f->next;
+ for (f = rtnl_dereference(p->h[i]); f; f = next) {
+ next = rtnl_dereference(f->next);
if (walker->count >= walker->skip) {
if (walker->fn(tp, (unsigned long) &f->result,
walker) < 0) {
@@ -404,17 +470,9 @@
}
}
-
-static int tcindex_destroy_element(struct tcf_proto *tp,
- unsigned long arg, struct tcf_walker *walker)
-{
- return __tcindex_delete(tp, arg, 0);
-}
-
-
static void tcindex_destroy(struct tcf_proto *tp)
{
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcf_walker walker;
pr_debug("tcindex_destroy(tp %p),p %p\n", tp, p);
@@ -422,17 +480,16 @@
walker.skip = 0;
walker.fn = tcindex_destroy_element;
tcindex_walk(tp, &walker);
- kfree(p->perfect);
- kfree(p->h);
- kfree(p);
- tp->root = NULL;
+
+ RCU_INIT_POINTER(tp->root, NULL);
+ call_rcu(&p->rcu, __tcindex_destroy);
}
static int tcindex_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
struct sk_buff *skb, struct tcmsg *t)
{
- struct tcindex_data *p = tp->root;
+ struct tcindex_data *p = rtnl_dereference(tp->root);
struct tcindex_filter_result *r = (struct tcindex_filter_result *) fh;
unsigned char *b = skb_tail_pointer(skb);
struct nlattr *nest;
@@ -455,15 +512,18 @@
nla_nest_end(skb, nest);
} else {
if (p->perfect) {
- t->tcm_handle = r-p->perfect;
+ t->tcm_handle = r - p->perfect;
} else {
struct tcindex_filter *f;
+ struct tcindex_filter __rcu **fp;
int i;
t->tcm_handle = 0;
for (i = 0; !t->tcm_handle && i < p->hash; i++) {
- for (f = p->h[i]; !t->tcm_handle && f;
- f = f->next) {
+ fp = &p->h[i];
+ for (f = rtnl_dereference(*fp);
+ !t->tcm_handle && f;
+ fp = &f->next, f = rtnl_dereference(*fp)) {
if (&f->result == r)
t->tcm_handle = f->key;
}