1 files changed, 386 insertions, 0 deletions

diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index c85363c45fc0..a7188eeb135b 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -22,6 +22,7 @@
 #include <linux/list_nulls.h>
 #include <linux/workqueue.h>
 #include <linux/mutex.h>
+#include <linux/rcupdate.h>
 
 /*
  * The end of the chain is marked with a special nulls marks which has
@@ -42,6 +43,9 @@
 #define RHT_HASH_BITS		27
 #define RHT_BASE_SHIFT		RHT_HASH_BITS
 
+/* Base bits plus 1 bit for nulls marker */
+#define RHT_HASH_RESERVED_SPACE	(RHT_BASE_BITS + 1)
+
 struct rhash_head {
 	struct rhash_head __rcu		*next;
 };
@@ -72,8 +76,20 @@ struct bucket_table {
 	struct rhash_head __rcu	*buckets[] ____cacheline_aligned_in_smp;
 };
 
+/**
+ * struct rhashtable_compare_arg - Key for the function rhashtable_compare
+ * @ht: Hash table
+ * @key: Key to compare against
+ */
+struct rhashtable_compare_arg {
+	struct rhashtable *ht;
+	const void *key;
+};
+
 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
+typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg,
+			       const void *obj);
 
 struct rhashtable;
 
@@ -89,6 +105,7 @@ struct rhashtable;
  * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
  * @hashfn: Function to hash key
  * @obj_hashfn: Function to hash object
+ * @obj_cmpfn: Function to compare key with object
  */
 struct rhashtable_params {
 	size_t			nelem_hint;
@@ -101,6 +118,7 @@ struct rhashtable_params {
 	size_t			locks_mul;
 	rht_hashfn_t		hashfn;
 	rht_obj_hashfn_t	obj_hashfn;
+	rht_obj_cmpfn_t		obj_cmpfn;
 };
 
 /**
@@ -165,6 +183,83 @@ static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
 	return ((unsigned long) ptr) >> 1;
 }
 
+static inline void *rht_obj(const struct rhashtable *ht,
+			    const struct rhash_head *he)
+{
+	return (char *)he - ht->p.head_offset;
+}
+
+static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
+					    unsigned int hash)
+{
+	return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1);
+}
+
+static inline unsigned int rht_key_hashfn(
+	struct rhashtable *ht, const struct bucket_table *tbl,
+	const void *key, const struct rhashtable_params params)
+{
+	return rht_bucket_index(tbl, params.hashfn(key, params.key_len ?:
+							ht->p.key_len,
+						   tbl->hash_rnd));
+}
+
+static inline unsigned int rht_head_hashfn(
+	struct rhashtable *ht, const struct bucket_table *tbl,
+	const struct rhash_head *he, const struct rhashtable_params params)
+{
+	const char *ptr = rht_obj(ht, he);
+
+	return likely(params.obj_hashfn) ?
+	       rht_bucket_index(tbl, params.obj_hashfn(ptr, tbl->hash_rnd)) :
+	       rht_key_hashfn(ht, tbl, ptr + params.key_offset, params);
+}
+
+/**
+ * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
+ * @ht:		hash table
+ * @tbl:	current table
+ */
+static inline bool rht_grow_above_75(const struct rhashtable *ht,
+				     const struct bucket_table *tbl)
+{
+	/* Expand table when exceeding 75% load */
+	return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
+	       (!ht->p.max_size || tbl->size < ht->p.max_size);
+}
+
+/**
+ * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
+ * @ht:		hash table
+ * @tbl:	current table
+ */
+static inline bool rht_shrink_below_30(const struct rhashtable *ht,
+				       const struct bucket_table *tbl)
+{
+	/* Shrink table beneath 30% load */
+	return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
+	       tbl->size > ht->p.min_size;
+}
+
+/* The bucket lock is selected based on the hash and protects mutations
+ * on a group of hash buckets.
+ *
+ * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
+ * a single lock always covers both buckets which may both contains
+ * entries which link to the same bucket of the old table during resizing.
+ * This allows to simplify the locking as locking the bucket in both
+ * tables during resize always guarantee protection.
+ *
+ * IMPORTANT: When holding the bucket lock of both the old and new table
+ * during expansions and shrinking, the old bucket lock must always be
+ * acquired first.
+ */
+static inline spinlock_t *rht_bucket_lock(const struct bucket_table *tbl,
+					  unsigned int hash)
+{
+	return &tbl->locks[hash & tbl->locks_mask];
+}
+
 #ifdef CONFIG_PROVE_LOCKING
 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
@@ -184,6 +279,9 @@ static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
 int rhashtable_init(struct rhashtable *ht,
 		    const struct rhashtable_params *params);
 
+int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
+			   struct rhash_head *obj,
+			   struct bucket_table *old_tbl);
 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
 
@@ -356,4 +454,292 @@ void rhashtable_destroy(struct rhashtable *ht);
 	rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
 					tbl, hash, member)
 
+static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
+				     const void *obj)
+{
+	struct rhashtable *ht = arg->ht;
+	const char *ptr = obj;
+
+	return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
+}
+
+/**
+ * rhashtable_lookup_fast - search hash table, inlined version
+ * @ht:		hash table
+ * @key:	the pointer to the key
+ * @params:	hash table parameters
+ *
+ * Computes the hash value for the key and traverses the bucket chain looking
+ * for a entry with an identical key. The first matching entry is returned.
+ *
+ * Returns the first entry on which the compare function returned true.
+ */
+static inline void *rhashtable_lookup_fast(
+	struct rhashtable *ht, const void *key,
+	const struct rhashtable_params params)
+{
+	struct rhashtable_compare_arg arg = {
+		.ht = ht,
+		.key = key,
+	};
+	const struct bucket_table *tbl;
+	struct rhash_head *he;
+	unsigned hash;
+
+	rcu_read_lock();
+
+	tbl = rht_dereference_rcu(ht->tbl, ht);
+restart:
+	hash = rht_key_hashfn(ht, tbl, key, params);
+	rht_for_each_rcu(he, tbl, hash) {
+		if (params.obj_cmpfn ?
+		    params.obj_cmpfn(&arg, rht_obj(ht, he)) :
+		    rhashtable_compare(&arg, rht_obj(ht, he)))
+			continue;
+		rcu_read_unlock();
+		return rht_obj(ht, he);
+	}
+
+	/* Ensure we see any new tables. */
+	smp_rmb();
+
+	tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+	if (unlikely(tbl))
+		goto restart;
+	rcu_read_unlock();
+
+	return NULL;
+}
+
+static inline int __rhashtable_insert_fast(
+	struct rhashtable *ht, const void *key, struct rhash_head *obj,
+	const struct rhashtable_params params)
+{
+	struct rhashtable_compare_arg arg = {
+		.ht = ht,
+		.key = key,
+	};
+	int err = -EEXIST;
+	struct bucket_table *tbl, *new_tbl;
+	struct rhash_head *head;
+	spinlock_t *lock;
+	unsigned hash;
+
+	rcu_read_lock();
+
+	tbl = rht_dereference_rcu(ht->tbl, ht);
+	hash = rht_head_hashfn(ht, tbl, obj, params);
+	lock = rht_bucket_lock(tbl, hash);
+
+	spin_lock_bh(lock);
+
+	/* Because we have already taken the bucket lock in tbl,
+	 * if we find that future_tbl is not yet visible then
+	 * that guarantees all other insertions of the same entry
+	 * will also grab the bucket lock in tbl because until
+	 * the rehash completes ht->tbl won't be changed.
+	 */
+	new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+	if (unlikely(new_tbl)) {
+		err = rhashtable_insert_slow(ht, key, obj, new_tbl);
+		goto out;
+	}
+
+	if (!key)
+		goto skip_lookup;
+
+	rht_for_each(head, tbl, hash) {
+		if (unlikely(!(params.obj_cmpfn ?
+			       params.obj_cmpfn(&arg, rht_obj(ht, head)) :
+			       rhashtable_compare(&arg, rht_obj(ht, head)))))
+			goto out;
+	}
+
+skip_lookup:
+	err = 0;
+
+	head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
+
+	RCU_INIT_POINTER(obj->next, head);
+
+	rcu_assign_pointer(tbl->buckets[hash], obj);
+
+	atomic_inc(&ht->nelems);
+	if (rht_grow_above_75(ht, tbl))
+		schedule_work(&ht->run_work);
+
+out:
+	spin_unlock_bh(lock);
+	rcu_read_unlock();
+
+	return err;
+}
+
+/**
+ * rhashtable_insert_fast - insert object into hash table
+ * @ht:		hash table
+ * @obj:	pointer to hash head inside object
+ * @params:	hash table parameters
+ *
+ * Will take a per bucket spinlock to protect against mutual mutations
+ * on the same bucket. Multiple insertions may occur in parallel unless
+ * they map to the same bucket lock.
+ *
+ * It is safe to call this function from atomic context.
+ *
+ * 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().
+ */
+static inline int rhashtable_insert_fast(
+	struct rhashtable *ht, struct rhash_head *obj,
+	const struct rhashtable_params params)
+{
+	return __rhashtable_insert_fast(ht, NULL, obj, params);
+}
+
+/**
+ * rhashtable_lookup_insert_fast - lookup and insert object into hash table
+ * @ht:		hash table
+ * @obj:	pointer to hash head inside object
+ * @params:	hash table parameters
+ *
+ * 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.
+ *
+ * This lookup function may only be used for fixed key hash table (key_len
+ * parameter set). It will BUG() if used inappropriately.
+ *
+ * It is safe to call this function from atomic context.
+ *
+ * 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().
+ */
+static inline int rhashtable_lookup_insert_fast(
+	struct rhashtable *ht, struct rhash_head *obj,
+	const struct rhashtable_params params)
+{
+	const char *key = rht_obj(ht, obj);
+
+	BUG_ON(ht->p.obj_hashfn);
+
+	return __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj,
+					params);
+}
+
+/**
+ * rhashtable_lookup_insert_key - search and insert object to hash table
+ *				  with explicit key
+ * @ht:		hash table
+ * @key:	key
+ * @obj:	pointer to hash head inside object
+ * @params:	hash table parameters
+ *
+ * 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().
+ *
+ * Returns zero on success.
+ */
+static inline int rhashtable_lookup_insert_key(
+	struct rhashtable *ht, const void *key, struct rhash_head *obj,
+	const struct rhashtable_params params)
+{
+	BUG_ON(!ht->p.obj_hashfn || !key);
+
+	return __rhashtable_insert_fast(ht, key, obj, params);
+}
+
+static inline int __rhashtable_remove_fast(
+	struct rhashtable *ht, struct bucket_table *tbl,
+	struct rhash_head *obj, const struct rhashtable_params params)
+{
+	struct rhash_head __rcu **pprev;
+	struct rhash_head *he;
+	spinlock_t * lock;
+	unsigned hash;
+	int err = -ENOENT;
+
+	hash = rht_head_hashfn(ht, tbl, obj, params);
+	lock = rht_bucket_lock(tbl, hash);
+
+	spin_lock_bh(lock);
+
+	pprev = &tbl->buckets[hash];
+	rht_for_each(he, tbl, hash) {
+		if (he != obj) {
+			pprev = &he->next;
+			continue;
+		}
+
+		rcu_assign_pointer(*pprev, obj->next);
+		err = 0;
+		break;
+	}
+
+	spin_unlock_bh(lock);
+
+	return err;
+}
+
+/**
+ * rhashtable_remove_fast - remove object from hash table
+ * @ht:		hash table
+ * @obj:	pointer to hash head inside object
+ * @params:	hash table parameters
+ *
+ * Since the hash chain is single linked, the removal operation needs to
+ * walk the bucket chain upon removal. The removal operation is thus
+ * considerable slow if the hash table is not correctly sized.
+ *
+ * Will automatically shrink the table via rhashtable_expand() if the
+ * shrink_decision function specified at rhashtable_init() returns true.
+ *
+ * Returns zero on success, -ENOENT if the entry could not be found.
+ */
+static inline int rhashtable_remove_fast(
+	struct rhashtable *ht, struct rhash_head *obj,
+	const struct rhashtable_params params)
+{
+	struct bucket_table *tbl;
+	int err;
+
+	rcu_read_lock();
+
+	tbl = rht_dereference_rcu(ht->tbl, ht);
+
+	/* Because we have already taken (and released) the bucket
+	 * lock in old_tbl, if we find that future_tbl is not yet
+	 * visible then that guarantees the entry to still be in
+	 * the old tbl if it exists.
+	 */
+	while ((err = __rhashtable_remove_fast(ht, tbl, obj, params)) &&
+	       (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
+		;
+
+	if (err)
+		goto out;
+
+	atomic_dec(&ht->nelems);
+	if (rht_shrink_below_30(ht, tbl))
+		schedule_work(&ht->run_work);
+
+out:
+	rcu_read_unlock();
+
+	return err;
+}
+
 #endif /* _LINUX_RHASHTABLE_H */