1 files changed, 344 insertions, 114 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index e6b85c4a5828..312e3437c7bc 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -26,19 +26,42 @@
 
 #define HASH_DEFAULT_SIZE       64UL
 #define HASH_MIN_SIZE           4UL
+#define BUCKET_LOCKS_PER_CPU   128UL
+
+enum {
+        RHT_LOCK_NORMAL,
+        RHT_LOCK_NESTED,
+        RHT_LOCK_NESTED2,
+};
+
+/* The bucket lock is selected based on the hash and protects mutations
+ * on a group of hash buckets.
+ *
+ * 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];
+}
 
 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
+#define ASSERT_BUCKET_LOCK(TBL, HASH) \
+        BUG_ON(!lockdep_rht_bucket_is_held(TBL, HASH))
 
 #ifdef CONFIG_PROVE_LOCKING
-int lockdep_rht_mutex_is_held(const struct rhashtable *ht)
+int lockdep_rht_mutex_is_held(struct rhashtable *ht)
 {
-        return ht->p.mutex_is_held(ht->p.parent);
+        return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
 }
 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
 
 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
 {
-        return 1;
+        spinlock_t *lock = bucket_lock(tbl, hash);
+
+        return (debug_locks) ? lockdep_is_held(lock) : 1;
 }
 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
 #endif
@@ -66,7 +89,7 @@ static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr)
         return hash;
 }
 
-static u32 key_hashfn(const struct rhashtable *ht, const void *key, u32 len)
+static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len)
 {
         struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
         u32 hash;
@@ -95,7 +118,49 @@ static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n)
         return pprev;
 }
 
-static struct bucket_table *bucket_table_alloc(size_t nbuckets)
+static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl)
+{
+        unsigned int i, size;
+#if defined(CONFIG_PROVE_LOCKING)
+        unsigned int nr_pcpus = 2;
+#else
+        unsigned int nr_pcpus = num_possible_cpus();
+#endif
+
+        nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL);
+        size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
+
+        /* Never allocate more than one lock per bucket */
+        size = min_t(unsigned int, size, tbl->size);
+
+        if (sizeof(spinlock_t) != 0) {
+#ifdef CONFIG_NUMA
+                if (size * sizeof(spinlock_t) > PAGE_SIZE)
+                        tbl->locks = vmalloc(size * sizeof(spinlock_t));
+                else
+#endif
+                tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
+                                           GFP_KERNEL);
+                if (!tbl->locks)
+                        return -ENOMEM;
+                for (i = 0; i < size; i++)
+                        spin_lock_init(&tbl->locks[i]);
+        }
+        tbl->locks_mask = size - 1;
+
+        return 0;
+}
+
+static void bucket_table_free(const struct bucket_table *tbl)
+{
+        if (tbl)
+                kvfree(tbl->locks);
+
+        kvfree(tbl);
+}
+
+static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
+                                               size_t nbuckets)
 {
         struct bucket_table *tbl;
         size_t size;
@@ -110,12 +175,12 @@ static struct bucket_table *bucket_table_alloc(size_t nbuckets)
 
         tbl->size = nbuckets;
 
-        return tbl;
-}
+        if (alloc_bucket_locks(ht, tbl) < 0) {
+                bucket_table_free(tbl);
+                return NULL;
+        }
 
-static void bucket_table_free(const struct bucket_table *tbl)
-{
-        kvfree(tbl);
+        return tbl;
 }
 
 /**
@@ -126,7 +191,7 @@ static void bucket_table_free(const struct bucket_table *tbl)
 bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
 {
         /* Expand table when exceeding 75% load */
-        return ht->nelems > (new_size / 4 * 3);
+        return atomic_read(&ht->nelems) > (new_size / 4 * 3);
 }
 EXPORT_SYMBOL_GPL(rht_grow_above_75);
 
@@ -138,41 +203,59 @@ EXPORT_SYMBOL_GPL(rht_grow_above_75);
 bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
 {
         /* Shrink table beneath 30% load */
-        return ht->nelems < (new_size * 3 / 10);
+        return atomic_read(&ht->nelems) < (new_size * 3 / 10);
 }
 EXPORT_SYMBOL_GPL(rht_shrink_below_30);
 
 static void hashtable_chain_unzip(const struct rhashtable *ht,
                                   const struct bucket_table *new_tbl,
-                                  struct bucket_table *old_tbl, size_t n)
+                                  struct bucket_table *old_tbl,
+                                  size_t old_hash)
 {
         struct rhash_head *he, *p, *next;
-        unsigned int h;
+        spinlock_t *new_bucket_lock, *new_bucket_lock2 = NULL;
+        unsigned int new_hash, new_hash2;
+
+        ASSERT_BUCKET_LOCK(old_tbl, old_hash);
 
         /* Old bucket empty, no work needed. */
-        p = rht_dereference(old_tbl->buckets[n], ht);
+        p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl,
+                                   old_hash);
         if (!p)
                 return;
 
+        new_hash = new_hash2 = head_hashfn(ht, new_tbl, p);
+        new_bucket_lock = bucket_lock(new_tbl, new_hash);
+
         /* Advance the old bucket pointer one or more times until it
          * reaches a node that doesn't hash to the same bucket as the
          * previous node p. Call the previous node p;
          */
-        h = head_hashfn(ht, new_tbl, p);
-        rht_for_each_continue(he, p->next, old_tbl, n) {
-                if (head_hashfn(ht, new_tbl, he) != h)
+        rht_for_each_continue(he, p->next, old_tbl, old_hash) {
+                new_hash2 = head_hashfn(ht, new_tbl, he);
+                if (new_hash != new_hash2)
                         break;
                 p = he;
         }
-        RCU_INIT_POINTER(old_tbl->buckets[n], p->next);
+        rcu_assign_pointer(old_tbl->buckets[old_hash], p->next);
+
+        spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
+
+        /* If we have encountered an entry that maps to a different bucket in
+         * the new table, lock down that bucket as well as we might cut off
+         * the end of the chain.
+         */
+        new_bucket_lock2 = bucket_lock(new_tbl, new_hash);
+        if (new_bucket_lock != new_bucket_lock2)
+                spin_lock_bh_nested(new_bucket_lock2, RHT_LOCK_NESTED2);
 
         /* Find the subsequent node which does hash to the same
          * bucket as node P, or NULL if no such node exists.
          */
         next = NULL;
         if (he) {
-                rht_for_each_continue(he, he->next, old_tbl, n) {
-                        if (head_hashfn(ht, new_tbl, he) == h) {
+                rht_for_each_continue(he, he->next, old_tbl, old_hash) {
+                        if (head_hashfn(ht, new_tbl, he) == new_hash) {
                                 next = he;
                                 break;
                         }
@@ -182,7 +265,23 @@ static void hashtable_chain_unzip(const struct rhashtable *ht,
         /* Set p's next pointer to that subsequent node pointer,
          * bypassing the nodes which do not hash to p's bucket
          */
-        RCU_INIT_POINTER(p->next, next);
+        rcu_assign_pointer(p->next, next);
+
+        if (new_bucket_lock != new_bucket_lock2)
+                spin_unlock_bh(new_bucket_lock2);
+        spin_unlock_bh(new_bucket_lock);
+}
+
+static void link_old_to_new(struct bucket_table *new_tbl,
+                            unsigned int new_hash, struct rhash_head *entry)
+{
+        spinlock_t *new_bucket_lock;
+
+        new_bucket_lock = bucket_lock(new_tbl, new_hash);
+
+        spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
+        rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry);
+        spin_unlock_bh(new_bucket_lock);
 }
 
 /**
@@ -195,43 +294,59 @@ static void hashtable_chain_unzip(const struct rhashtable *ht,
  * 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 table mutations take place.
- * It is however valid to have concurrent lookups if they are RCU protected.
+ * 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.
  */
 int rhashtable_expand(struct rhashtable *ht)
 {
         struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
         struct rhash_head *he;
-        unsigned int i, h;
-        bool complete;
+        spinlock_t *old_bucket_lock;
+        unsigned int new_hash, old_hash;
+        bool complete = false;
 
         ASSERT_RHT_MUTEX(ht);
 
         if (ht->p.max_shift && ht->shift >= ht->p.max_shift)
                 return 0;
 
-        new_tbl = bucket_table_alloc(old_tbl->size * 2);
+        new_tbl = bucket_table_alloc(ht, old_tbl->size * 2);
         if (new_tbl == NULL)
                 return -ENOMEM;
 
         ht->shift++;
 
-        /* For each new bucket, search the corresponding old bucket
-         * for the first entry that hashes to the new bucket, and
-         * link the new bucket to that entry. Since all the entries
-         * which will end up in the new bucket appear in the same
-         * old bucket, this constructs an entirely valid new hash
-         * table, but with multiple buckets "zipped" together into a
-         * single imprecise chain.
+        /* Make insertions go into the new, empty table right away. Deletions
+         * and lookups will be attempted in both tables until we synchronize.
+         * The synchronize_rcu() guarantees for the new table to be picked up
+         * so no new additions go into the old table while we relink.
+         */
+        rcu_assign_pointer(ht->future_tbl, new_tbl);
+        synchronize_rcu();
+
+        /* For each new bucket, search the corresponding old bucket for the
+         * first entry that hashes to the new bucket, and link the end of
+         * newly formed bucket chain (containing entries added to future
+         * table) to that entry. Since all the entries which will end up in
+         * the new bucket appear in the same old bucket, this constructs an
+         * entirely valid new hash table, but with multiple buckets
+         * "zipped" together into a single imprecise chain.
          */
-        for (i = 0; i < new_tbl->size; i++) {
-                h = rht_bucket_index(old_tbl, i);
-                rht_for_each(he, old_tbl, h) {
-                        if (head_hashfn(ht, new_tbl, he) == i) {
-                                RCU_INIT_POINTER(new_tbl->buckets[i], he);
+        for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
+                old_hash = rht_bucket_index(old_tbl, new_hash);
+                old_bucket_lock = bucket_lock(old_tbl, old_hash);
+
+                spin_lock_bh(old_bucket_lock);
+                rht_for_each(he, old_tbl, old_hash) {
+                        if (head_hashfn(ht, new_tbl, he) == new_hash) {
+                                link_old_to_new(new_tbl, new_hash, he);
                                 break;
                         }
                 }
+                spin_unlock_bh(old_bucket_lock);
         }
 
         /* Publish the new table pointer. Lookups may now traverse
@@ -241,7 +356,7 @@ int rhashtable_expand(struct rhashtable *ht)
         rcu_assign_pointer(ht->tbl, new_tbl);
 
         /* Unzip interleaved hash chains */
-        do {
+        while (!complete && !ht->being_destroyed) {
                 /* Wait for readers. All new readers will see the new
                  * table, and thus no references to the old table will
                  * remain.
@@ -253,12 +368,17 @@ int rhashtable_expand(struct rhashtable *ht)
                  * table): ...
                  */
                 complete = true;
-                for (i = 0; i < old_tbl->size; i++) {
-                        hashtable_chain_unzip(ht, new_tbl, old_tbl, i);
-                        if (old_tbl->buckets[i] != NULL)
+                for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
+                        old_bucket_lock = bucket_lock(old_tbl, old_hash);
+                        spin_lock_bh(old_bucket_lock);
+
+                        hashtable_chain_unzip(ht, new_tbl, old_tbl, old_hash);
+                        if (old_tbl->buckets[old_hash] != NULL)
                                 complete = false;
+
+                        spin_unlock_bh(old_bucket_lock);
                 }
-        } while (!complete);
+        }
 
         bucket_table_free(old_tbl);
         return 0;
@@ -272,38 +392,65 @@ EXPORT_SYMBOL_GPL(rhashtable_expand);
  * 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.
+ *
  * The caller must ensure that no concurrent table mutations take place.
  * It is however valid to have concurrent lookups if they are RCU protected.
+ *
+ * It is valid to have concurrent insertions and deletions protected by per
+ * bucket locks or concurrent RCU protected lookups and traversals.
  */
 int rhashtable_shrink(struct rhashtable *ht)
 {
-        struct bucket_table *ntbl, *tbl = rht_dereference(ht->tbl, ht);
-        unsigned int i;
+        struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht);
+        spinlock_t *new_bucket_lock, *old_bucket_lock1, *old_bucket_lock2;
+        unsigned int new_hash;
 
         ASSERT_RHT_MUTEX(ht);
 
         if (ht->shift <= ht->p.min_shift)
                 return 0;
 
-        ntbl = bucket_table_alloc(tbl->size / 2);
-        if (ntbl == NULL)
+        new_tbl = bucket_table_alloc(ht, tbl->size / 2);
+        if (new_tbl == NULL)
                 return -ENOMEM;
 
-        ht->shift--;
+        rcu_assign_pointer(ht->future_tbl, new_tbl);
+        synchronize_rcu();
 
-        /* Link each bucket in the new table to the first bucket
-         * in the old table that contains entries which will hash
-         * to the new bucket.
+        /* Link the first entry in the old bucket to the end of the
+         * bucket in the new table. As entries are concurrently being
+         * added to the new table, lock down the new bucket. As we
+         * always divide the size in half when shrinking, each bucket
+         * in the new table maps to exactly two buckets in the old
+         * table.
+         *
+         * As removals can occur concurrently on the old table, we need
+         * to lock down both matching buckets in the old table.
          */
-        for (i = 0; i < ntbl->size; i++) {
-                ntbl->buckets[i] = tbl->buckets[i];
-                RCU_INIT_POINTER(*bucket_tail(ntbl, i),
-                                 tbl->buckets[i + ntbl->size]);
-
+        for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
+                old_bucket_lock1 = bucket_lock(tbl, new_hash);
+                old_bucket_lock2 = bucket_lock(tbl, new_hash + new_tbl->size);
+                new_bucket_lock = bucket_lock(new_tbl, new_hash);
+
+                spin_lock_bh(old_bucket_lock1);
+                spin_lock_bh_nested(old_bucket_lock2, RHT_LOCK_NESTED);
+                spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED2);
+
+                rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
+                                   tbl->buckets[new_hash]);
+                rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
+                                   tbl->buckets[new_hash + new_tbl->size]);
+
+                spin_unlock_bh(new_bucket_lock);
+                spin_unlock_bh(old_bucket_lock2);
+                spin_unlock_bh(old_bucket_lock1);
         }
 
         /* Publish the new, valid hash table */
-        rcu_assign_pointer(ht->tbl, ntbl);
+        rcu_assign_pointer(ht->tbl, new_tbl);
+        ht->shift--;
 
         /* Wait for readers. No new readers will have references to the
          * old hash table.
@@ -316,31 +463,63 @@ int rhashtable_shrink(struct rhashtable *ht)
 }
 EXPORT_SYMBOL_GPL(rhashtable_shrink);
 
+static void rht_deferred_worker(struct work_struct *work)
+{
+        struct rhashtable *ht;
+        struct bucket_table *tbl;
+
+        ht = container_of(work, struct rhashtable, run_work.work);
+        mutex_lock(&ht->mutex);
+        tbl = rht_dereference(ht->tbl, ht);
+
+        if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
+                rhashtable_expand(ht);
+        else if (ht->p.shrink_decision && ht->p.shrink_decision(ht, tbl->size))
+                rhashtable_shrink(ht);
+
+        mutex_unlock(&ht->mutex);
+}
+
 /**
  * rhashtable_insert - insert object into hash hash table
  * @ht:         hash table
  * @obj:        pointer to hash head inside object
  *
- * Will automatically grow the table via rhashtable_expand() if the the
- * grow_decision function specified at rhashtable_init() returns true.
+ * 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.
  *
- * The caller must ensure that no concurrent table mutations occur. It is
- * however valid to have concurrent lookups if they are RCU protected.
+ * 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)
 {
-        struct bucket_table *tbl = rht_dereference(ht->tbl, ht);
-        u32 hash;
+        struct bucket_table *tbl;
+        spinlock_t *lock;
+        unsigned hash;
 
-        ASSERT_RHT_MUTEX(ht);
+        rcu_read_lock();
 
+        tbl = rht_dereference_rcu(ht->future_tbl, ht);
         hash = head_hashfn(ht, tbl, obj);
+        lock = bucket_lock(tbl, hash);
+
+        spin_lock_bh(lock);
         RCU_INIT_POINTER(obj->next, tbl->buckets[hash]);
         rcu_assign_pointer(tbl->buckets[hash], obj);
-        ht->nelems++;
+        spin_unlock_bh(lock);
 
-        if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
-                rhashtable_expand(ht);
+        atomic_inc(&ht->nelems);
+
+        /* Only grow the table if no resizing is currently in progress. */
+        if (ht->tbl != ht->future_tbl &&
+            ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
+                schedule_delayed_work(&ht->run_work, 0);
+
+        rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(rhashtable_insert);
 
@@ -361,32 +540,56 @@ EXPORT_SYMBOL_GPL(rhashtable_insert);
  */
 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
 {
-        struct bucket_table *tbl = rht_dereference(ht->tbl, ht);
+        struct bucket_table *tbl;
         struct rhash_head __rcu **pprev;
         struct rhash_head *he;
-        u32 h;
+        spinlock_t *lock;
+        unsigned int hash;
 
-        ASSERT_RHT_MUTEX(ht);
+        rcu_read_lock();
+        tbl = rht_dereference_rcu(ht->tbl, ht);
+        hash = head_hashfn(ht, tbl, obj);
 
-        h = head_hashfn(ht, tbl, obj);
+        lock = bucket_lock(tbl, hash);
+        spin_lock_bh(lock);
 
-        pprev = &tbl->buckets[h];
-        rht_for_each(he, tbl, h) {
+restart:
+        pprev = &tbl->buckets[hash];
+        rht_for_each(he, tbl, hash) {
                 if (he != obj) {
                         pprev = &he->next;
                         continue;
                 }
 
-                RCU_INIT_POINTER(*pprev, he->next);
-                ht->nelems--;
+                rcu_assign_pointer(*pprev, obj->next);
+                atomic_dec(&ht->nelems);
 
-                if (ht->p.shrink_decision &&
+                spin_unlock_bh(lock);
+
+                if (ht->tbl != ht->future_tbl &&
+                    ht->p.shrink_decision &&
                     ht->p.shrink_decision(ht, tbl->size))
-                        rhashtable_shrink(ht);
+                        schedule_delayed_work(&ht->run_work, 0);
+
+                rcu_read_unlock();
 
                 return true;
         }
 
+        if (tbl != rht_dereference_rcu(ht->tbl, ht)) {
+                spin_unlock_bh(lock);
+
+                tbl = rht_dereference_rcu(ht->tbl, ht);
+                hash = head_hashfn(ht, tbl, obj);
+
+                lock = bucket_lock(tbl, hash);
+                spin_lock_bh(lock);
+                goto restart;
+        }
+
+        spin_unlock_bh(lock);
+        rcu_read_unlock();
+
         return false;
 }
 EXPORT_SYMBOL_GPL(rhashtable_remove);
@@ -402,25 +605,35 @@ EXPORT_SYMBOL_GPL(rhashtable_remove);
  * This lookup function may only be used for fixed key hash table (key_len
  * paramter set). It will BUG() if used inappropriately.
  *
- * Lookups may occur in parallel with hash mutations as long as the lookup is
- * guarded by rcu_read_lock(). The caller must take care of this.
+ * Lookups may occur in parallel with hashtable mutations and resizing.
  */
-void *rhashtable_lookup(const struct rhashtable *ht, const void *key)
+void *rhashtable_lookup(struct rhashtable *ht, const void *key)
 {
-        const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
+        const struct bucket_table *tbl, *old_tbl;
         struct rhash_head *he;
-        u32 h;
+        u32 hash;
 
         BUG_ON(!ht->p.key_len);
 
-        h = key_hashfn(ht, key, ht->p.key_len);
-        rht_for_each_rcu(he, tbl, h) {
+        rcu_read_lock();
+        old_tbl = rht_dereference_rcu(ht->tbl, ht);
+        tbl = rht_dereference_rcu(ht->future_tbl, ht);
+        hash = key_hashfn(ht, key, ht->p.key_len);
+restart:
+        rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) {
                 if (memcmp(rht_obj(ht, he) + ht->p.key_offset, key,
                            ht->p.key_len))
                         continue;
+                rcu_read_unlock();
                 return rht_obj(ht, he);
         }
 
+        if (unlikely(tbl != old_tbl)) {
+                tbl = old_tbl;
+                goto restart;
+        }
+
+        rcu_read_unlock();
         return NULL;
 }
 EXPORT_SYMBOL_GPL(rhashtable_lookup);
@@ -435,25 +648,36 @@ EXPORT_SYMBOL_GPL(rhashtable_lookup);
  * Traverses the bucket chain behind the provided hash value and calls the
  * specified compare function for each entry.
  *
- * Lookups may occur in parallel with hash mutations as long as the lookup is
- * guarded by rcu_read_lock(). The caller must take care of this.
+ * 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(const struct rhashtable *ht, const void *key,
+void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
                                 bool (*compare)(void *, void *), void *arg)
 {
-        const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
+        const struct bucket_table *tbl, *old_tbl;
         struct rhash_head *he;
         u32 hash;
 
+        rcu_read_lock();
+
+        old_tbl = rht_dereference_rcu(ht->tbl, ht);
+        tbl = rht_dereference_rcu(ht->future_tbl, ht);
         hash = key_hashfn(ht, key, ht->p.key_len);
-        rht_for_each_rcu(he, tbl, hash) {
+restart:
+        rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) {
                 if (!compare(rht_obj(ht, he), arg))
                         continue;
+                rcu_read_unlock();
                 return rht_obj(ht, he);
         }
 
+        if (unlikely(tbl != old_tbl)) {
+                tbl = old_tbl;
+                goto restart;
+        }
+        rcu_read_unlock();
+
         return NULL;
 }
 EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
@@ -485,9 +709,6 @@ static size_t rounded_hashtable_size(struct rhashtable_params *params)
  *      .key_offset = offsetof(struct test_obj, key),
  *      .key_len = sizeof(int),
  *      .hashfn = jhash,
- * #ifdef CONFIG_PROVE_LOCKING
- *      .mutex_is_held = &my_mutex_is_held,
- * #endif
  * };
  *
  * Configuration Example 2: Variable length keys
@@ -507,9 +728,6 @@ static size_t rounded_hashtable_size(struct rhashtable_params *params)
  *      .head_offset = offsetof(struct test_obj, node),
  *      .hashfn = jhash,
  *      .obj_hashfn = my_hash_fn,
- * #ifdef CONFIG_PROVE_LOCKING
- *      .mutex_is_held = &my_mutex_is_held,
- * #endif
  * };
  */
 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
@@ -529,18 +747,29 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
         if (params->nelem_hint)
                 size = rounded_hashtable_size(params);
 
-        tbl = bucket_table_alloc(size);
+        memset(ht, 0, sizeof(*ht));
+        mutex_init(&ht->mutex);
+        memcpy(&ht->p, params, sizeof(*params));
+
+        if (params->locks_mul)
+                ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
+        else
+                ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
+
+        tbl = bucket_table_alloc(ht, size);
         if (tbl == NULL)
                 return -ENOMEM;
 
-        memset(ht, 0, sizeof(*ht));
         ht->shift = ilog2(tbl->size);
-        memcpy(&ht->p, params, sizeof(*params));
         RCU_INIT_POINTER(ht->tbl, tbl);
+        RCU_INIT_POINTER(ht->future_tbl, tbl);
 
         if (!ht->p.hash_rnd)
                 get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));
 
+        if (ht->p.grow_decision || ht->p.shrink_decision)
+                INIT_DEFERRABLE_WORK(&ht->run_work, rht_deferred_worker);
+
         return 0;
 }
 EXPORT_SYMBOL_GPL(rhashtable_init);
@@ -553,9 +782,16 @@ EXPORT_SYMBOL_GPL(rhashtable_init);
  * has to make sure that no resizing may happen by unpublishing the hashtable
  * and waiting for the quiescent cycle before releasing the bucket array.
  */
-void rhashtable_destroy(const struct rhashtable *ht)
+void rhashtable_destroy(struct rhashtable *ht)
 {
-        bucket_table_free(ht->tbl);
+        ht->being_destroyed = true;
+
+        mutex_lock(&ht->mutex);
+
+        cancel_delayed_work(&ht->run_work);
+        bucket_table_free(rht_dereference(ht->tbl, ht));
+
+        mutex_unlock(&ht->mutex);
 }
 EXPORT_SYMBOL_GPL(rhashtable_destroy);
 
@@ -570,13 +806,6 @@ EXPORT_SYMBOL_GPL(rhashtable_destroy);
 #define TEST_PTR        ((void *) 0xdeadbeef)
 #define TEST_NEXPANDS   4
 
-#ifdef CONFIG_PROVE_LOCKING
-static int test_mutex_is_held(void *parent)
-{
-        return 1;
-}
-#endif
-
 struct test_obj {
         void                    *ptr;
         int                     value;
@@ -646,10 +875,10 @@ static void test_bucket_stats(struct rhashtable *ht, bool quiet)
                                 i, tbl->buckets[i], cnt);
         }
 
-        pr_info("  Traversal complete: counted=%u, nelems=%zu, entries=%d\n",
-                total, ht->nelems, TEST_ENTRIES);
+        pr_info("  Traversal complete: counted=%u, nelems=%u, entries=%d\n",
+                total, atomic_read(&ht->nelems), TEST_ENTRIES);
 
-        if (total != ht->nelems || total != TEST_ENTRIES)
+        if (total != atomic_read(&ht->nelems) || total != TEST_ENTRIES)
                 pr_warn("Test failed: Total count mismatch ^^^");
 }
 
@@ -688,7 +917,9 @@ static int __init test_rhashtable(struct rhashtable *ht)
 
         for (i = 0; i < TEST_NEXPANDS; i++) {
                 pr_info("  Table expansion iteration %u...\n", i);
+                mutex_lock(&ht->mutex);
                 rhashtable_expand(ht);
+                mutex_unlock(&ht->mutex);
 
                 rcu_read_lock();
                 pr_info("  Verifying lookups...\n");
@@ -698,7 +929,9 @@ static int __init test_rhashtable(struct rhashtable *ht)
 
         for (i = 0; i < TEST_NEXPANDS; i++) {
                 pr_info("  Table shrinkage iteration %u...\n", i);
+                mutex_lock(&ht->mutex);
                 rhashtable_shrink(ht);
+                mutex_unlock(&ht->mutex);
 
                 rcu_read_lock();
                 pr_info("  Verifying lookups...\n");
@@ -741,9 +974,6 @@ static int __init test_rht_init(void)
                 .key_offset = offsetof(struct test_obj, value),
                 .key_len = sizeof(int),
                 .hashfn = jhash,
-#ifdef CONFIG_PROVE_LOCKING
-                .mutex_is_held = &test_mutex_is_held,
-#endif
                 .grow_decision = rht_grow_above_75,
                 .shrink_decision = rht_shrink_below_30,
         };