1 files changed, 220 insertions, 50 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 32d0ad058380..172454e6b979 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -32,6 +32,11 @@
 #define HASH_MIN_SIZE		4U
 #define BUCKET_LOCKS_PER_CPU	32UL
 
+union nested_table {
+	union nested_table __rcu *table;
+	struct rhash_head __rcu *bucket;
+};
+
 static u32 head_hashfn(struct rhashtable *ht,
 		       const struct bucket_table *tbl,
 		       const struct rhash_head *he)
@@ -76,6 +81,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
 	/* Never allocate more than 0.5 locks per bucket */
 	size = min_t(unsigned int, size, tbl->size >> 1);
 
+	if (tbl->nest)
+		size = min(size, 1U << tbl->nest);
+
 	if (sizeof(spinlock_t) != 0) {
 		tbl->locks = NULL;
 #ifdef CONFIG_NUMA
@@ -99,8 +107,45 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
 	return 0;
 }
 
+static void nested_table_free(union nested_table *ntbl, unsigned int size)
+{
+	const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+	const unsigned int len = 1 << shift;
+	unsigned int i;
+
+	ntbl = rcu_dereference_raw(ntbl->table);
+	if (!ntbl)
+		return;
+
+	if (size > len) {
+		size >>= shift;
+		for (i = 0; i < len; i++)
+			nested_table_free(ntbl + i, size);
+	}
+
+	kfree(ntbl);
+}
+
+static void nested_bucket_table_free(const struct bucket_table *tbl)
+{
+	unsigned int size = tbl->size >> tbl->nest;
+	unsigned int len = 1 << tbl->nest;
+	union nested_table *ntbl;
+	unsigned int i;
+
+	ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
+
+	for (i = 0; i < len; i++)
+		nested_table_free(ntbl + i, size);
+
+	kfree(ntbl);
+}
+
 static void bucket_table_free(const struct bucket_table *tbl)
 {
+	if (tbl->nest)
+		nested_bucket_table_free(tbl);
+
 	if (tbl)
 		kvfree(tbl->locks);
 
@@ -112,6 +157,59 @@ static void bucket_table_free_rcu(struct rcu_head *head)
 	bucket_table_free(container_of(head, struct bucket_table, rcu));
 }
 
+static union nested_table *nested_table_alloc(struct rhashtable *ht,
+					      union nested_table __rcu **prev,
+					      unsigned int shifted,
+					      unsigned int nhash)
+{
+	union nested_table *ntbl;
+	int i;
+
+	ntbl = rcu_dereference(*prev);
+	if (ntbl)
+		return ntbl;
+
+	ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
+
+	if (ntbl && shifted) {
+		for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0].bucket); i++)
+			INIT_RHT_NULLS_HEAD(ntbl[i].bucket, ht,
+					    (i << shifted) | nhash);
+	}
+
+	rcu_assign_pointer(*prev, ntbl);
+
+	return ntbl;
+}
+
+static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
+						      size_t nbuckets,
+						      gfp_t gfp)
+{
+	const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+	struct bucket_table *tbl;
+	size_t size;
+
+	if (nbuckets < (1 << (shift + 1)))
+		return NULL;
+
+	size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
+
+	tbl = kzalloc(size, gfp);
+	if (!tbl)
+		return NULL;
+
+	if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
+				0, 0)) {
+		kfree(tbl);
+		return NULL;
+	}
+
+	tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
+
+	return tbl;
+}
+
 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
 					       size_t nbuckets,
 					       gfp_t gfp)
@@ -126,10 +224,17 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
 		tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
 	if (tbl == NULL && gfp == GFP_KERNEL)
 		tbl = vzalloc(size);
+
+	size = nbuckets;
+
+	if (tbl == NULL && gfp != GFP_KERNEL) {
+		tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
+		nbuckets = 0;
+	}
 	if (tbl == NULL)
 		return NULL;
 
-	tbl->size = nbuckets;
+	tbl->size = size;
 
 	if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
 		bucket_table_free(tbl);
@@ -164,12 +269,17 @@ static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
 	struct bucket_table *new_tbl = rhashtable_last_table(ht,
 		rht_dereference_rcu(old_tbl->future_tbl, ht));
-	struct rhash_head __rcu **pprev = &old_tbl->buckets[old_hash];
-	int err = -ENOENT;
+	struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
+	int err = -EAGAIN;
 	struct rhash_head *head, *next, *entry;
 	spinlock_t *new_bucket_lock;
 	unsigned int new_hash;
 
+	if (new_tbl->nest)
+		goto out;
+
+	err = -ENOENT;
+
 	rht_for_each(entry, old_tbl, old_hash) {
 		err = 0;
 		next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
@@ -202,19 +312,26 @@ out:
 	return err;
 }
 
-static void rhashtable_rehash_chain(struct rhashtable *ht,
+static int rhashtable_rehash_chain(struct rhashtable *ht,
 				    unsigned int old_hash)
 {
 	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
 	spinlock_t *old_bucket_lock;
+	int err;
 
 	old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
 
 	spin_lock_bh(old_bucket_lock);
-	while (!rhashtable_rehash_one(ht, old_hash))
+	while (!(err = rhashtable_rehash_one(ht, old_hash)))
 		;
-	old_tbl->rehash++;
+
+	if (err == -ENOENT) {
+		old_tbl->rehash++;
+		err = 0;
+	}
 	spin_unlock_bh(old_bucket_lock);
+
+	return err;
 }
 
 static int rhashtable_rehash_attach(struct rhashtable *ht,
@@ -246,13 +363,17 @@ static int rhashtable_rehash_table(struct rhashtable *ht)
 	struct bucket_table *new_tbl;
 	struct rhashtable_walker *walker;
 	unsigned int old_hash;
+	int err;
 
 	new_tbl = rht_dereference(old_tbl->future_tbl, ht);
 	if (!new_tbl)
 		return 0;
 
-	for (old_hash = 0; old_hash < old_tbl->size; old_hash++)
-		rhashtable_rehash_chain(ht, old_hash);
+	for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
+		err = rhashtable_rehash_chain(ht, old_hash);
+		if (err)
+			return err;
+	}
 
 	/* Publish the new table pointer. */
 	rcu_assign_pointer(ht->tbl, new_tbl);
@@ -271,31 +392,16 @@ static int rhashtable_rehash_table(struct rhashtable *ht)
 	return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
 }
 
-/**
- * rhashtable_expand - Expand hash table while allowing concurrent lookups
- * @ht:		the hash table to expand
- *
- * A secondary bucket array is allocated and the hash entries are migrated.
- *
- * This function may only be called in a context where it is safe to call
- * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
- *
- * The caller must ensure that no concurrent resizing occurs by holding
- * ht->mutex.
- *
- * It is valid to have concurrent insertions and deletions protected by per
- * bucket locks or concurrent RCU protected lookups and traversals.
- */
-static int rhashtable_expand(struct rhashtable *ht)
+static int rhashtable_rehash_alloc(struct rhashtable *ht,
+				   struct bucket_table *old_tbl,
+				   unsigned int size)
 {
-	struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+	struct bucket_table *new_tbl;
 	int err;
 
 	ASSERT_RHT_MUTEX(ht);
 
-	old_tbl = rhashtable_last_table(ht, old_tbl);
-
-	new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
+	new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
 	if (new_tbl == NULL)
 		return -ENOMEM;
 
@@ -324,12 +430,9 @@ static int rhashtable_expand(struct rhashtable *ht)
  */
 static int rhashtable_shrink(struct rhashtable *ht)
 {
-	struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+	struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
 	unsigned int nelems = atomic_read(&ht->nelems);
 	unsigned int size = 0;
-	int err;
-
-	ASSERT_RHT_MUTEX(ht);
 
 	if (nelems)
 		size = roundup_pow_of_two(nelems * 3 / 2);
@@ -342,15 +445,7 @@ static int rhashtable_shrink(struct rhashtable *ht)
 	if (rht_dereference(old_tbl->future_tbl, ht))
 		return -EEXIST;
 
-	new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
-	if (new_tbl == NULL)
-		return -ENOMEM;
-
-	err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
-	if (err)
-		bucket_table_free(new_tbl);
-
-	return err;
+	return rhashtable_rehash_alloc(ht, old_tbl, size);
 }
 
 static void rht_deferred_worker(struct work_struct *work)
@@ -366,11 +461,14 @@ static void rht_deferred_worker(struct work_struct *work)
 	tbl = rhashtable_last_table(ht, tbl);
 
 	if (rht_grow_above_75(ht, tbl))
-		rhashtable_expand(ht);
+		err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
 	else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
-		rhashtable_shrink(ht);
+		err = rhashtable_shrink(ht);
+	else if (tbl->nest)
+		err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
 
-	err = rhashtable_rehash_table(ht);
+	if (!err)
+		err = rhashtable_rehash_table(ht);
 
 	mutex_unlock(&ht->mutex);
 
@@ -439,8 +537,8 @@ static void *rhashtable_lookup_one(struct rhashtable *ht,
 	int elasticity;
 
 	elasticity = ht->elasticity;
-	pprev = &tbl->buckets[hash];
-	rht_for_each(head, tbl, hash) {
+	pprev = rht_bucket_var(tbl, hash);
+	rht_for_each_continue(head, *pprev, tbl, hash) {
 		struct rhlist_head *list;
 		struct rhlist_head *plist;
 
@@ -477,6 +575,7 @@ static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
 						  struct rhash_head *obj,
 						  void *data)
 {
+	struct rhash_head __rcu **pprev;
 	struct bucket_table *new_tbl;
 	struct rhash_head *head;
 
@@ -499,7 +598,11 @@ static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
 	if (unlikely(rht_grow_above_100(ht, tbl)))
 		return ERR_PTR(-EAGAIN);
 
-	head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
+	pprev = rht_bucket_insert(ht, tbl, hash);
+	if (!pprev)
+		return ERR_PTR(-ENOMEM);
+
+	head = rht_dereference_bucket(*pprev, tbl, hash);
 
 	RCU_INIT_POINTER(obj->next, head);
 	if (ht->rhlist) {
@@ -509,7 +612,7 @@ static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
 		RCU_INIT_POINTER(list->next, NULL);
 	}
 
-	rcu_assign_pointer(tbl->buckets[hash], obj);
+	rcu_assign_pointer(*pprev, obj);
 
 	atomic_inc(&ht->nelems);
 	if (rht_grow_above_75(ht, tbl))
@@ -975,7 +1078,7 @@ void rhashtable_free_and_destroy(struct rhashtable *ht,
 				 void (*free_fn)(void *ptr, void *arg),
 				 void *arg)
 {
-	const struct bucket_table *tbl;
+	struct bucket_table *tbl;
 	unsigned int i;
 
 	cancel_work_sync(&ht->run_work);
@@ -986,7 +1089,7 @@ void rhashtable_free_and_destroy(struct rhashtable *ht,
 		for (i = 0; i < tbl->size; i++) {
 			struct rhash_head *pos, *next;
 
-			for (pos = rht_dereference(tbl->buckets[i], ht),
+			for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
 			     next = !rht_is_a_nulls(pos) ?
 					rht_dereference(pos->next, ht) : NULL;
 			     !rht_is_a_nulls(pos);
@@ -1007,3 +1110,70 @@ void rhashtable_destroy(struct rhashtable *ht)
 	return rhashtable_free_and_destroy(ht, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(rhashtable_destroy);
+
+struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
+					    unsigned int hash)
+{
+	const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+	static struct rhash_head __rcu *rhnull =
+		(struct rhash_head __rcu *)NULLS_MARKER(0);
+	unsigned int index = hash & ((1 << tbl->nest) - 1);
+	unsigned int size = tbl->size >> tbl->nest;
+	unsigned int subhash = hash;
+	union nested_table *ntbl;
+
+	ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
+	ntbl = rht_dereference_bucket(ntbl[index].table, tbl, hash);
+	subhash >>= tbl->nest;
+
+	while (ntbl && size > (1 << shift)) {
+		index = subhash & ((1 << shift) - 1);
+		ntbl = rht_dereference_bucket(ntbl[index].table, tbl, hash);
+		size >>= shift;
+		subhash >>= shift;
+	}
+
+	if (!ntbl)
+		return &rhnull;
+
+	return &ntbl[subhash].bucket;
+
+}
+EXPORT_SYMBOL_GPL(rht_bucket_nested);
+
+struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
+						   struct bucket_table *tbl,
+						   unsigned int hash)
+{
+	const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+	unsigned int index = hash & ((1 << tbl->nest) - 1);
+	unsigned int size = tbl->size >> tbl->nest;
+	union nested_table *ntbl;
+	unsigned int shifted;
+	unsigned int nhash;
+
+	ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
+	hash >>= tbl->nest;
+	nhash = index;
+	shifted = tbl->nest;
+	ntbl = nested_table_alloc(ht, &ntbl[index].table,
+				  size <= (1 << shift) ? shifted : 0, nhash);
+
+	while (ntbl && size > (1 << shift)) {
+		index = hash & ((1 << shift) - 1);
+		size >>= shift;
+		hash >>= shift;
+		nhash |= index << shifted;
+		shifted += shift;
+		ntbl = nested_table_alloc(ht, &ntbl[index].table,
+					  size <= (1 << shift) ? shifted : 0,
+					  nhash);
+	}
+
+	if (!ntbl)
+		return NULL;
+
+	return &ntbl[hash].bucket;
+
+}
+EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);