Commit 52e3ad9f authored by David S. Miller's avatar David S. Miller

Merge branch 'rhashtable-next'

Ying Xue says:

====================
remove nl_sk_hash_lock from netlink socket

After tipc socket successfully avoids the involvement of an extra lock
with rhashtable_lookup_insert(), it's possible for netlink socket to
remove its hash socket lock now. But as netlink socket needs a compare
function to look for an object, we first introduce a new function
called rhashtable_lookup_compare_insert() in commit #1 which is
implemented based on original rhashtable_lookup_insert(). We
subsequently remove nl_sk_hash_lock from netlink socket with the new
introduced function in commit #2. Lastly, as Thomas requested, we add
commit #3 to indicate the implementation of what the grow and shrink
decision function must enforce min/max shift.

v2:
 As Thomas pointed out, there was a race between checking portid and
 then setting it in commit #2. Now use socket lock to make the process
 of both checking and setting portid atomic, and then eliminate the
 race.
====================
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents d2c60b13 6f73d3b1
......@@ -79,6 +79,10 @@ struct rhashtable;
* @obj_hashfn: Function to hash object
* @grow_decision: If defined, may return true if table should expand
* @shrink_decision: If defined, may return true if table should shrink
*
* Note: when implementing the grow and shrink decision function, min/max
* shift must be enforced, otherwise, resizing watermarks they set may be
* useless.
*/
struct rhashtable_params {
size_t nelem_hint;
......@@ -168,7 +172,12 @@ int rhashtable_shrink(struct rhashtable *ht);
void *rhashtable_lookup(struct rhashtable *ht, const void *key);
void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
bool (*compare)(void *, void *), void *arg);
bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
struct rhash_head *obj,
bool (*compare)(void *, void *),
void *arg);
void rhashtable_destroy(struct rhashtable *ht);
......
......@@ -726,6 +726,43 @@ EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
* to rhashtable_init().
*/
bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
{
struct rhashtable_compare_arg arg = {
.ht = ht,
.key = rht_obj(ht, obj) + ht->p.key_offset,
};
BUG_ON(!ht->p.key_len);
return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare,
&arg);
}
EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
/**
* rhashtable_lookup_compare_insert - search and insert object to hash table
* with compare function
* @ht: hash table
* @obj: pointer to hash head inside object
* @compare: compare function, must return true on match
* @arg: argument passed on to compare function
*
* Locks down the bucket chain in both the old and new table if a resize
* is in progress to ensure that writers can't remove from the old table
* and can't insert to the new table during the atomic operation of search
* and insertion. Searches for duplicates in both the old and new table if
* a resize is in progress.
*
* Lookups may occur in parallel with hashtable mutations and resizing.
*
* Will trigger an automatic deferred table resizing if the size grows
* beyond the watermark indicated by grow_decision() which can be passed
* to rhashtable_init().
*/
bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
struct rhash_head *obj,
bool (*compare)(void *, void *),
void *arg)
{
struct bucket_table *new_tbl, *old_tbl;
spinlock_t *new_bucket_lock, *old_bucket_lock;
......@@ -747,7 +784,8 @@ bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
if (unlikely(old_tbl != new_tbl))
spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
if (rhashtable_lookup(ht, rht_obj(ht, obj) + ht->p.key_offset)) {
if (rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset,
compare, arg)) {
success = false;
goto exit;
}
......@@ -763,7 +801,7 @@ bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
return success;
}
EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert);
static size_t rounded_hashtable_size(struct rhashtable_params *params)
{
......
......@@ -98,7 +98,7 @@ static void netlink_skb_destructor(struct sk_buff *skb);
/* nl_table locking explained:
* Lookup and traversal are protected with an RCU read-side lock. Insertion
* and removal are protected with nl_sk_hash_lock while using RCU list
* and removal are protected with per bucket lock while using RCU list
* modification primitives and may run in parallel to RCU protected lookups.
* Destruction of the Netlink socket may only occur *after* nl_table_lock has
* been acquired * either during or after the socket has been removed from
......@@ -110,10 +110,6 @@ static atomic_t nl_table_users = ATOMIC_INIT(0);
#define nl_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&nl_table_lock));
/* Protects netlink socket hash table mutations */
DEFINE_MUTEX(nl_sk_hash_lock);
EXPORT_SYMBOL_GPL(nl_sk_hash_lock);
static ATOMIC_NOTIFIER_HEAD(netlink_chain);
static DEFINE_SPINLOCK(netlink_tap_lock);
......@@ -998,6 +994,19 @@ static struct sock *__netlink_lookup(struct netlink_table *table, u32 portid,
&netlink_compare, &arg);
}
static bool __netlink_insert(struct netlink_table *table, struct sock *sk,
struct net *net)
{
struct netlink_compare_arg arg = {
.net = net,
.portid = nlk_sk(sk)->portid,
};
return rhashtable_lookup_compare_insert(&table->hash,
&nlk_sk(sk)->node,
&netlink_compare, &arg);
}
static struct sock *netlink_lookup(struct net *net, int protocol, u32 portid)
{
struct netlink_table *table = &nl_table[protocol];
......@@ -1043,9 +1052,7 @@ static int netlink_insert(struct sock *sk, struct net *net, u32 portid)
struct netlink_table *table = &nl_table[sk->sk_protocol];
int err = -EADDRINUSE;
mutex_lock(&nl_sk_hash_lock);
if (__netlink_lookup(table, portid, net))
goto err;
lock_sock(sk);
err = -EBUSY;
if (nlk_sk(sk)->portid)
......@@ -1058,10 +1065,12 @@ static int netlink_insert(struct sock *sk, struct net *net, u32 portid)
nlk_sk(sk)->portid = portid;
sock_hold(sk);
rhashtable_insert(&table->hash, &nlk_sk(sk)->node);
err = 0;
if (__netlink_insert(table, sk, net))
err = 0;
else
sock_put(sk);
err:
mutex_unlock(&nl_sk_hash_lock);
release_sock(sk);
return err;
}
......@@ -1069,13 +1078,11 @@ static void netlink_remove(struct sock *sk)
{
struct netlink_table *table;
mutex_lock(&nl_sk_hash_lock);
table = &nl_table[sk->sk_protocol];
if (rhashtable_remove(&table->hash, &nlk_sk(sk)->node)) {
WARN_ON(atomic_read(&sk->sk_refcnt) == 1);
__sock_put(sk);
}
mutex_unlock(&nl_sk_hash_lock);
netlink_table_grab();
if (nlk_sk(sk)->subscriptions) {
......
......@@ -74,6 +74,5 @@ struct netlink_table {
extern struct netlink_table *nl_table;
extern rwlock_t nl_table_lock;
extern struct mutex nl_sk_hash_lock;
#endif
......@@ -103,7 +103,7 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
{
struct netlink_table *tbl = &nl_table[protocol];
struct rhashtable *ht = &tbl->hash;
const struct bucket_table *htbl = rht_dereference(ht->tbl, ht);
const struct bucket_table *htbl = rht_dereference_rcu(ht->tbl, ht);
struct net *net = sock_net(skb->sk);
struct netlink_diag_req *req;
struct netlink_sock *nlsk;
......@@ -115,7 +115,7 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
for (i = 0; i < htbl->size; i++) {
struct rhash_head *pos;
rht_for_each_entry(nlsk, pos, htbl, i, node) {
rht_for_each_entry_rcu(nlsk, pos, htbl, i, node) {
sk = (struct sock *)nlsk;
if (!net_eq(sock_net(sk), net))
......@@ -172,7 +172,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
req = nlmsg_data(cb->nlh);
mutex_lock(&nl_sk_hash_lock);
rcu_read_lock();
read_lock(&nl_table_lock);
if (req->sdiag_protocol == NDIAG_PROTO_ALL) {
......@@ -186,7 +186,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
} else {
if (req->sdiag_protocol >= MAX_LINKS) {
read_unlock(&nl_table_lock);
mutex_unlock(&nl_sk_hash_lock);
rcu_read_unlock();
return -ENOENT;
}
......@@ -194,7 +194,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
}
read_unlock(&nl_table_lock);
mutex_unlock(&nl_sk_hash_lock);
rcu_read_unlock();
return skb->len;
}
......
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