Merge branch 'rhashtable-inlined-interface'

Herbert Xu says:

====================
rhashtable: Introduce inlined interface

This series of patches introduces the inlined rhashtable interface.

The idea is to make all the function pointers visible to the compiler
by providing the rhashtable_params structure explicitly to each
inline rhashtable function.  For example, instead of doing

	obj = rhashtable_lookup(ht, key);

you would now do

	obj = rhashtable_lookup_fast(ht, key, params);

Where params is the same data that you would give to rhashtable_init.
In particular, within rhashtable.c itself we would simply supply
ht->p.

So to convert users over, you simply have to make params globally
accessible, e.g., by placing it in a static const variable, which
can then be used at each inlined call site, as well as by the
rhashtable_init call.

The only ticky bit is that some users (i.e., netfilter) has a
dynamic key length.  This is dealt with by using params.key_len
in the inline functions when it is non-zero, and otherwise falling
back on ht->p.key_len.

Note that I've only tested this on one compiler, gcc 4.7.2.  So
please test this with your compilers as well and make sure that
the code is actually inlined without indirect function calls.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

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);