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authorFlorian Westphal <fw@strlen.de>2014-07-24 16:50:36 +0200
committerAlex Shi <alex.shi@linaro.org>2015-12-01 15:01:20 +0800
commit31b36090a9807196f6885b8ed2c39a6ab31d23f5 (patch)
treec42be4eff2d1b9bd28939f3073317953381337ad
parent1af41b58c2d3572206912ac0becd4197b62de419 (diff)
downloadlinux-linaro-stable-linux-linaro-lsk-v3.10-android-test.tar.gz
rehash is rare operation, don't force readers to take the read-side rwlock. Instead, we only have to detect the (rare) case where the secret was altered while we are trying to insert a new inetfrag queue into the table. If it was changed, drop the bucket lock and recompute the hash to get the 'new' chain bucket that we have to insert into. Joint work with Nikolay Aleksandrov. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> (cherry picked from commit ab1c724f633080ed2e8a0cfe61654599b55cf8f9) Signed-off-by: Alex Shi <alex.shi@linaro.org> Conflicts: net/ipv6/netfilter/nf_conntrack_reasm.c net/ipv6/reassembly.c
-rw-r--r--include/net/inet_frag.h13
-rw-r--r--net/ieee802154/reassembly.c1
-rw-r--r--net/ipv4/inet_fragment.c88
-rw-r--r--net/ipv4/ip_fragment.c1
-rw-r--r--net/ipv6/netfilter/nf_conntrack_reasm.c2
5 files changed, 62 insertions, 43 deletions
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index d9cc5bb..6f4930a 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -53,11 +53,6 @@ struct inet_frag_bucket {
struct inet_frags {
struct inet_frag_bucket hash[INETFRAGS_HASHSZ];
- /* This rwlock is a global lock (seperate per IPv4, IPv6 and
- * netfilter). Important to keep this on a seperate cacheline.
- * Its primarily a rebuild protection rwlock.
- */
- rwlock_t lock ____cacheline_aligned_in_smp;
struct work_struct frags_work;
unsigned int next_bucket;
@@ -66,8 +61,12 @@ struct inet_frags {
/* The first call to hashfn is responsible to initialize
* rnd. This is best done with net_get_random_once.
+ *
+ * rnd_seqlock is used to let hash insertion detect
+ * when it needs to re-lookup the hash chain to use.
*/
u32 rnd;
+ seqlock_t rnd_seqlock;
int qsize;
unsigned int (*hashfn)(const struct inet_frag_queue *);
@@ -89,8 +88,8 @@ void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f);
void inet_frag_kill(struct inet_frag_queue *q, struct inet_frags *f);
void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f);
struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
- struct inet_frags *f, void *key, unsigned int hash)
- __releases(&f->lock);
+ struct inet_frags *f, void *key, unsigned int hash);
+
void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q,
const char *prefix);
diff --git a/net/ieee802154/reassembly.c b/net/ieee802154/reassembly.c
index 20d2196..8da635d 100644
--- a/net/ieee802154/reassembly.c
+++ b/net/ieee802154/reassembly.c
@@ -124,7 +124,6 @@ fq_find(struct net *net, const struct lowpan_frag_info *frag_info,
arg.src = src;
arg.dst = dst;
- read_lock(&lowpan_frags.lock);
hash = lowpan_hash_frag(frag_info->d_tag, frag_info->d_size, src, dst);
q = inet_frag_find(&ieee802154_lowpan->frags,
diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index 58d4c38..62b1f73 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -68,8 +68,7 @@ static void inet_frag_secret_rebuild(struct inet_frags *f)
{
int i;
- /* Per bucket lock NOT needed here, due to write lock protection */
- write_lock_bh(&f->lock);
+ write_seqlock_bh(&f->rnd_seqlock);
if (!inet_frag_may_rebuild(f))
goto out;
@@ -82,6 +81,8 @@ static void inet_frag_secret_rebuild(struct inet_frags *f)
struct hlist_node *n;
hb = &f->hash[i];
+ spin_lock(&hb->chain_lock);
+
hlist_for_each_entry_safe(q, n, &hb->chain, list) {
unsigned int hval = inet_frag_hashfn(f, q);
@@ -92,15 +93,28 @@ static void inet_frag_secret_rebuild(struct inet_frags *f)
/* Relink to new hash chain. */
hb_dest = &f->hash[hval];
+
+ /* This is the only place where we take
+ * another chain_lock while already holding
+ * one. As this will not run concurrently,
+ * we cannot deadlock on hb_dest lock below, if its
+ * already locked it will be released soon since
+ * other caller cannot be waiting for hb lock
+ * that we've taken above.
+ */
+ spin_lock_nested(&hb_dest->chain_lock,
+ SINGLE_DEPTH_NESTING);
hlist_add_head(&q->list, &hb_dest->chain);
+ spin_unlock(&hb_dest->chain_lock);
}
}
+ spin_unlock(&hb->chain_lock);
}
f->rebuild = false;
f->last_rebuild_jiffies = jiffies;
out:
- write_unlock_bh(&f->lock);
+ write_sequnlock_bh(&f->rnd_seqlock);
}
static bool inet_fragq_should_evict(const struct inet_frag_queue *q)
@@ -163,7 +177,7 @@ static void inet_frag_worker(struct work_struct *work)
BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ);
- read_lock_bh(&f->lock);
+ local_bh_disable();
for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) {
evicted += inet_evict_bucket(f, &f->hash[i]);
@@ -174,7 +188,8 @@ static void inet_frag_worker(struct work_struct *work)
f->next_bucket = i;
- read_unlock_bh(&f->lock);
+ local_bh_enable();
+
if (f->rebuild && inet_frag_may_rebuild(f))
inet_frag_secret_rebuild(f);
}
@@ -197,7 +212,8 @@ void inet_frags_init(struct inet_frags *f)
spin_lock_init(&hb->chain_lock);
INIT_HLIST_HEAD(&hb->chain);
}
- rwlock_init(&f->lock);
+
+ seqlock_init(&f->rnd_seqlock);
f->last_rebuild_jiffies = 0;
}
EXPORT_SYMBOL(inet_frags_init);
@@ -216,35 +232,56 @@ EXPORT_SYMBOL(inet_frags_fini);
void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
{
+ unsigned int seq;
int i;
nf->low_thresh = 0;
+ local_bh_disable();
- read_lock_bh(&f->lock);
+evict_again:
+ seq = read_seqbegin(&f->rnd_seqlock);
for (i = 0; i < INETFRAGS_HASHSZ ; i++)
inet_evict_bucket(f, &f->hash[i]);
- read_unlock_bh(&f->lock);
+ if (read_seqretry(&f->rnd_seqlock, seq))
+ goto evict_again;
+
+ local_bh_enable();
percpu_counter_destroy(&nf->mem);
}
EXPORT_SYMBOL(inet_frags_exit_net);
-static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
+static struct inet_frag_bucket *
+get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f)
+__acquires(hb->chain_lock)
{
struct inet_frag_bucket *hb;
- unsigned int hash;
+ unsigned int seq, hash;
+
+ restart:
+ seq = read_seqbegin(&f->rnd_seqlock);
- read_lock(&f->lock);
hash = inet_frag_hashfn(f, fq);
hb = &f->hash[hash];
spin_lock(&hb->chain_lock);
+ if (read_seqretry(&f->rnd_seqlock, seq)) {
+ spin_unlock(&hb->chain_lock);
+ goto restart;
+ }
+
+ return hb;
+}
+
+static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
+{
+ struct inet_frag_bucket *hb;
+
+ hb = get_frag_bucket_locked(fq, f);
hlist_del(&fq->list);
spin_unlock(&hb->chain_lock);
-
- read_unlock(&f->lock);
}
void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f)
@@ -300,30 +337,18 @@ static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
struct inet_frag_queue *qp_in, struct inet_frags *f,
void *arg)
{
- struct inet_frag_bucket *hb;
+ struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f);
struct inet_frag_queue *qp;
- unsigned int hash;
-
- read_lock(&f->lock); /* Protects against hash rebuild */
- /*
- * While we stayed w/o the lock other CPU could update
- * the rnd seed, so we need to re-calculate the hash
- * chain. Fortunatelly the qp_in can be used to get one.
- */
- hash = inet_frag_hashfn(f, qp_in);
- hb = &f->hash[hash];
- spin_lock(&hb->chain_lock);
#ifdef CONFIG_SMP
/* With SMP race we have to recheck hash table, because
- * such entry could be created on other cpu, while we
- * released the hash bucket lock.
+ * such entry could have been created on other cpu before
+ * we acquired hash bucket lock.
*/
hlist_for_each_entry(qp, &hb->chain, list) {
if (qp->net == nf && f->match(qp, arg)) {
atomic_inc(&qp->refcnt);
spin_unlock(&hb->chain_lock);
- read_unlock(&f->lock);
qp_in->last_in |= INET_FRAG_COMPLETE;
inet_frag_put(qp_in, f);
return qp;
@@ -338,7 +363,6 @@ static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf,
hlist_add_head(&qp->list, &hb->chain);
spin_unlock(&hb->chain_lock);
- read_unlock(&f->lock);
return qp;
}
@@ -382,7 +406,6 @@ static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf,
struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
struct inet_frags *f, void *key, unsigned int hash)
- __releases(&f->lock)
{
struct inet_frag_bucket *hb;
struct inet_frag_queue *q;
@@ -399,19 +422,18 @@ struct inet_frag_queue *inet_frag_find(struct netns_frags *nf,
if (q->net == nf && f->match(q, key)) {
atomic_inc(&q->refcnt);
spin_unlock(&hb->chain_lock);
- read_unlock(&f->lock);
return q;
}
depth++;
}
spin_unlock(&hb->chain_lock);
- read_unlock(&f->lock);
if (depth <= INETFRAGS_MAXDEPTH)
return inet_frag_create(nf, f, key);
if (inet_frag_may_rebuild(f)) {
- f->rebuild = true;
+ if (!f->rebuild)
+ f->rebuild = true;
inet_frag_schedule_worker(f);
}
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index dd223e1..0b91b7b 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -242,7 +242,6 @@ static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
arg.iph = iph;
arg.user = user;
- read_lock(&ip4_frags.lock);
hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index d4ea995..2197b29 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -193,7 +193,7 @@ static inline struct frag_queue *fq_find(struct net *net, __be32 id,
arg.dst = dst;
arg.ecn = ecn;
- read_lock_bh(&nf_frags.lock);
+ local_bh_disable();
hash = inet6_hash_frag(id, src, dst, nf_frags.rnd);
q = inet_frag_find(&net->nf_frag.frags, &nf_frags, &arg, hash);