2 files changed, 44 insertions, 385 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index e75c48d9d82f..83cfedd6612a 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -1,13 +1,13 @@
 /*
  * Resizable, Scalable, Concurrent Hash Table
  *
+ * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
  * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
  * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
  *
- * Based on the following paper:
- * https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
- *
  * Code partially derived from nft_hash
+ * Rewritten with rehash code from br_multicast plus single list
+ * pointer as suggested by Josh Triplett
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -30,53 +30,11 @@
 #define HASH_MIN_SIZE		4U
 #define BUCKET_LOCKS_PER_CPU   128UL
 
-/* Base bits plus 1 bit for nulls marker */
-#define HASH_RESERVED_SPACE	(RHT_BASE_BITS + 1)
-
-/* 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 spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash)
-{
-	return &tbl->locks[hash & tbl->locks_mask];
-}
-
-static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he)
-{
-	return (void *) he - ht->p.head_offset;
-}
-
-static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash)
-{
-	return (hash >> HASH_RESERVED_SPACE) & (tbl->size - 1);
-}
-
-static u32 key_hashfn(struct rhashtable *ht, const struct bucket_table *tbl,
-		      const void *key)
-{
-	return rht_bucket_index(tbl, ht->p.hashfn(key, ht->p.key_len,
-						  tbl->hash_rnd));
-}
-
 static u32 head_hashfn(struct rhashtable *ht,
 		       const struct bucket_table *tbl,
 		       const struct rhash_head *he)
 {
-	const char *ptr = rht_obj(ht, he);
-
-	return likely(ht->p.key_len) ?
-	       key_hashfn(ht, tbl, ptr + ht->p.key_offset) :
-	       rht_bucket_index(tbl, ht->p.obj_hashfn(ptr, tbl->hash_rnd));
+	return rht_head_hashfn(ht, tbl, he, ht->p);
 }
 
 #ifdef CONFIG_PROVE_LOCKING
@@ -90,7 +48,7 @@ EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
 
 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
 {
-	spinlock_t *lock = bucket_lock(tbl, hash);
+	spinlock_t *lock = rht_bucket_lock(tbl, hash);
 
 	return (debug_locks) ? lockdep_is_held(lock) : 1;
 }
@@ -178,32 +136,6 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
 	return tbl;
 }
 
-/**
- * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
- * @ht:		hash table
- * @tbl:	current table
- */
-static 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 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;
-}
-
 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned old_hash)
 {
 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
@@ -230,7 +162,7 @@ static int rhashtable_rehash_one(struct rhashtable *ht, unsigned old_hash)
 
 	new_hash = head_hashfn(ht, new_tbl, entry);
 
-	new_bucket_lock = bucket_lock(new_tbl, new_hash);
+	new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
 
 	spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
 	head = rht_dereference_bucket(new_tbl->buckets[new_hash],
@@ -255,7 +187,7 @@ static void rhashtable_rehash_chain(struct rhashtable *ht, unsigned old_hash)
 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
 	spinlock_t *old_bucket_lock;
 
-	old_bucket_lock = bucket_lock(old_tbl, old_hash);
+	old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
 
 	spin_lock_bh(old_bucket_lock);
 	while (!rhashtable_rehash_one(ht, old_hash))
@@ -376,315 +308,36 @@ unlock:
 	mutex_unlock(&ht->mutex);
 }
 
-static bool __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
-				bool (*compare)(void *, void *), void *arg)
+int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
+			   struct rhash_head *obj,
+			   struct bucket_table *tbl)
 {
-	struct bucket_table *tbl, *old_tbl;
 	struct rhash_head *head;
-	bool no_resize_running;
 	unsigned hash;
-	spinlock_t *old_lock;
-	bool success = true;
-
-	rcu_read_lock();
-
-	old_tbl = rht_dereference_rcu(ht->tbl, ht);
-	hash = head_hashfn(ht, old_tbl, obj);
-	old_lock = bucket_lock(old_tbl, hash);
+	int err = -EEXIST;
 
-	spin_lock_bh(old_lock);
-
-	/* Because we have already taken the bucket lock in old_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 old_tbl because until the
-	 * rehash completes ht->tbl won't be changed.
-	 */
-	tbl = rht_dereference_rcu(old_tbl->future_tbl, ht) ?: old_tbl;
-	if (tbl != old_tbl) {
-		hash = head_hashfn(ht, tbl, obj);
-		spin_lock_nested(bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
-	}
+	hash = head_hashfn(ht, tbl, obj);
+	spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
 
-	if (compare &&
-	    rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset,
-				      compare, arg)) {
-		success = false;
+	if (key && rhashtable_lookup_fast(ht, key, ht->p))
 		goto exit;
-	}
 
-	no_resize_running = tbl == old_tbl;
+	err = 0;
 
 	head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
 
-	if (rht_is_a_nulls(head))
-		INIT_RHT_NULLS_HEAD(obj->next, ht, hash);
-	else
-		RCU_INIT_POINTER(obj->next, head);
+	RCU_INIT_POINTER(obj->next, head);
 
 	rcu_assign_pointer(tbl->buckets[hash], obj);
 
 	atomic_inc(&ht->nelems);
-	if (no_resize_running && rht_grow_above_75(ht, tbl))
-		schedule_work(&ht->run_work);
 
 exit:
-	if (tbl != old_tbl)
-		spin_unlock(bucket_lock(tbl, hash));
-
-	spin_unlock_bh(old_lock);
-
-	rcu_read_unlock();
-
-	return success;
-}
-
-/**
- * rhashtable_insert - insert object into hash table
- * @ht:		hash table
- * @obj:	pointer to hash head inside object
- *
- * 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().
- */
-void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
-{
-	__rhashtable_insert(ht, obj, NULL, NULL);
-}
-EXPORT_SYMBOL_GPL(rhashtable_insert);
-
-static bool __rhashtable_remove(struct rhashtable *ht,
-				struct bucket_table *tbl,
-				struct rhash_head *obj)
-{
-	struct rhash_head __rcu **pprev;
-	struct rhash_head *he;
-	spinlock_t * lock;
-	unsigned hash;
-	bool ret = false;
-
-	hash = head_hashfn(ht, tbl, obj);
-	lock = 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);
-		ret = true;
-		break;
-	}
-
-	spin_unlock_bh(lock);
-
-	return ret;
-}
-
-/**
- * rhashtable_remove - remove object from hash table
- * @ht:		hash table
- * @obj:	pointer to hash head inside object
- *
- * 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.
- *
- * The caller must ensure that no concurrent table mutations occur. It is
- * however valid to have concurrent lookups if they are RCU protected.
- */
-bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
-{
-	struct bucket_table *tbl;
-	bool ret;
-
-	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 (!(ret = __rhashtable_remove(ht, tbl, obj)) &&
-	       (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
-		;
-
-	if (ret) {
-		atomic_dec(&ht->nelems);
-		if (rht_shrink_below_30(ht, tbl))
-			schedule_work(&ht->run_work);
-	}
-
-	rcu_read_unlock();
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(rhashtable_remove);
-
-struct rhashtable_compare_arg {
-	struct rhashtable *ht;
-	const void *key;
-};
-
-static bool rhashtable_compare(void *ptr, void *arg)
-{
-	struct rhashtable_compare_arg *x = arg;
-	struct rhashtable *ht = x->ht;
-
-	return !memcmp(ptr + ht->p.key_offset, x->key, ht->p.key_len);
-}
-
-/**
- * rhashtable_lookup - lookup key in hash table
- * @ht:		hash table
- * @key:	pointer to key
- *
- * 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.
- *
- * This lookup function may only be used for fixed key hash table (key_len
- * parameter set). It will BUG() if used inappropriately.
- *
- * Lookups may occur in parallel with hashtable mutations and resizing.
- */
-void *rhashtable_lookup(struct rhashtable *ht, const void *key)
-{
-	struct rhashtable_compare_arg arg = {
-		.ht = ht,
-		.key = key,
-	};
-
-	BUG_ON(!ht->p.key_len);
-
-	return rhashtable_lookup_compare(ht, key, &rhashtable_compare, &arg);
-}
-EXPORT_SYMBOL_GPL(rhashtable_lookup);
-
-/**
- * rhashtable_lookup_compare - search hash table with compare function
- * @ht:		hash table
- * @key:	the pointer to the key
- * @compare:	compare function, must return true on match
- * @arg:	argument passed on to compare function
- *
- * Traverses the bucket chain behind the provided hash value and calls the
- * specified compare function for each entry.
- *
- * Lookups may occur in parallel with hashtable mutations and resizing.
- *
- * Returns the first entry on which the compare function returned true.
- */
-void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
-				bool (*compare)(void *, void *), void *arg)
-{
-	const struct bucket_table *tbl;
-	struct rhash_head *he;
-	u32 hash;
-
-	rcu_read_lock();
-
-	tbl = rht_dereference_rcu(ht->tbl, ht);
-restart:
-	hash = key_hashfn(ht, tbl, key);
-	rht_for_each_rcu(he, tbl, hash) {
-		if (!compare(rht_obj(ht, he), arg))
-			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;
-}
-EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
+	spin_unlock(rht_bucket_lock(tbl, hash));
 
-/**
- * rhashtable_lookup_insert - lookup and insert object into hash table
- * @ht:		hash table
- * @obj:	pointer to hash head inside object
- *
- * 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().
- */
-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)
-{
-	BUG_ON(!ht->p.key_len);
-
-	return __rhashtable_insert(ht, obj, compare, arg);
+	return err;
 }
-EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert);
+EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
 
 /**
  * rhashtable_walk_init - Initialise an iterator
@@ -870,7 +523,7 @@ out:
 }
 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
 
-static size_t rounded_hashtable_size(struct rhashtable_params *params)
+static size_t rounded_hashtable_size(const struct rhashtable_params *params)
 {
 	return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
 		   (unsigned long)params->min_size);
@@ -919,15 +572,16 @@ static size_t rounded_hashtable_size(struct rhashtable_params *params)
  *	.obj_hashfn = my_hash_fn,
  * };
  */
-int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
+int rhashtable_init(struct rhashtable *ht,
+		    const struct rhashtable_params *params)
 {
 	struct bucket_table *tbl;
 	size_t size;
 
 	size = HASH_DEFAULT_SIZE;
 
-	if ((params->key_len && !params->hashfn) ||
-	    (!params->key_len && !params->obj_hashfn))
+	if ((!(params->key_len && params->hashfn) && !params->obj_hashfn) ||
+	    (params->obj_hashfn && !params->obj_cmpfn))
 		return -EINVAL;
 
 	if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
@@ -946,7 +600,7 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
 	if (params->max_size)
 		ht->p.max_size = rounddown_pow_of_two(params->max_size);
 
-	ht->p.min_size = max(params->min_size, HASH_MIN_SIZE);
+	ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
 
 	if (params->locks_mul)
 		ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 2bc403d8f9ee..a2ba6adb60a2 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -38,6 +38,16 @@ struct test_obj {
 	struct rhash_head	node;
 };
 
+static const struct rhashtable_params test_rht_params = {
+	.nelem_hint = TEST_HT_SIZE,
+	.head_offset = offsetof(struct test_obj, node),
+	.key_offset = offsetof(struct test_obj, value),
+	.key_len = sizeof(int),
+	.hashfn = jhash,
+	.max_size = 2, /* we expand/shrink manually here */
+	.nulls_base = (3U << RHT_BASE_SHIFT),
+};
+
 static int __init test_rht_lookup(struct rhashtable *ht)
 {
 	unsigned int i;
@@ -47,7 +57,7 @@ static int __init test_rht_lookup(struct rhashtable *ht)
 		bool expected = !(i % 2);
 		u32 key = i;
 
-		obj = rhashtable_lookup(ht, &key);
+		obj = rhashtable_lookup_fast(ht, &key, test_rht_params);
 
 		if (expected && !obj) {
 			pr_warn("Test failed: Could not find key %u\n", key);
@@ -133,7 +143,11 @@ static int __init test_rhashtable(struct rhashtable *ht)
 		obj->ptr = TEST_PTR;
 		obj->value = i * 2;
 
-		rhashtable_insert(ht, &obj->node);
+		err = rhashtable_insert_fast(ht, &obj->node, test_rht_params);
+		if (err) {
+			kfree(obj);
+			goto error;
+		}
 	}
 
 	rcu_read_lock();
@@ -173,10 +187,10 @@ static int __init test_rhashtable(struct rhashtable *ht)
 	for (i = 0; i < TEST_ENTRIES; i++) {
 		u32 key = i * 2;
 
-		obj = rhashtable_lookup(ht, &key);
+		obj = rhashtable_lookup_fast(ht, &key, test_rht_params);
 		BUG_ON(!obj);
 
-		rhashtable_remove(ht, &obj->node);
+		rhashtable_remove_fast(ht, &obj->node, test_rht_params);
 		kfree(obj);
 	}
 
@@ -195,20 +209,11 @@ static struct rhashtable ht;
 
 static int __init test_rht_init(void)
 {
-	struct rhashtable_params params = {
-		.nelem_hint = TEST_HT_SIZE,
-		.head_offset = offsetof(struct test_obj, node),
-		.key_offset = offsetof(struct test_obj, value),
-		.key_len = sizeof(int),
-		.hashfn = jhash,
-		.max_size = 2, /* we expand/shrink manually here */
-		.nulls_base = (3U << RHT_BASE_SHIFT),
-	};
 	int err;
 
 	pr_info("Running resizable hashtable tests...\n");
 
-	err = rhashtable_init(&ht, &params);
+	err = rhashtable_init(&ht, &test_rht_params);
 	if (err < 0) {
 		pr_warn("Test failed: Unable to initialize hashtable: %d\n",
 			err);