1 files changed, 360 insertions, 662 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index b5344ef4c684..4898442b837f 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
@@ -27,121 +27,18 @@
 #include <linux/err.h>
 
 #define HASH_DEFAULT_SIZE       64UL
-#define HASH_MIN_SIZE           4UL
+#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)
-
-enum {
-        RHT_LOCK_NORMAL,
-        RHT_LOCK_NESTED,
-};
-
-/* 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 & (tbl->size - 1);
-}
-
-static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr)
-{
-        u32 hash;
-
-        if (unlikely(!ht->p.key_len))
-                hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd);
-        else
-                hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len,
-                                    ht->p.hash_rnd);
-
-        return hash >> HASH_RESERVED_SPACE;
-}
-
-static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len)
-{
-        return ht->p.hashfn(key, len, ht->p.hash_rnd) >> HASH_RESERVED_SPACE;
-}
-
-static u32 head_hashfn(const struct rhashtable *ht,
+static u32 head_hashfn(struct rhashtable *ht,
                        const struct bucket_table *tbl,
                        const struct rhash_head *he)
 {
-        return rht_bucket_index(tbl, obj_raw_hashfn(ht, rht_obj(ht, he)));
+        return rht_head_hashfn(ht, tbl, he, ht->p);
 }
 
 #ifdef CONFIG_PROVE_LOCKING
-static void debug_dump_buckets(const struct rhashtable *ht,
-                               const struct bucket_table *tbl)
-{
-        struct rhash_head *he;
-        unsigned int i, hash;
-
-        for (i = 0; i < tbl->size; i++) {
-                pr_warn(" [Bucket %d] ", i);
-                rht_for_each_rcu(he, tbl, i) {
-                        hash = head_hashfn(ht, tbl, he);
-                        pr_cont("[hash = %#x, lock = %p] ",
-                                hash, bucket_lock(tbl, hash));
-                }
-                pr_cont("\n");
-        }
-
-}
-
-static void debug_dump_table(struct rhashtable *ht,
-                             const struct bucket_table *tbl,
-                             unsigned int hash)
-{
-        struct bucket_table *old_tbl, *future_tbl;
-
-        pr_emerg("BUG: lock for hash %#x in table %p not held\n",
-                 hash, tbl);
-
-        rcu_read_lock();
-        future_tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        old_tbl = rht_dereference_rcu(ht->tbl, ht);
-        if (future_tbl != old_tbl) {
-                pr_warn("Future table %p (size: %zd)\n",
-                        future_tbl, future_tbl->size);
-                debug_dump_buckets(ht, future_tbl);
-        }
-
-        pr_warn("Table %p (size: %zd)\n", old_tbl, old_tbl->size);
-        debug_dump_buckets(ht, old_tbl);
-
-        rcu_read_unlock();
-}
-
 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
-#define ASSERT_BUCKET_LOCK(HT, TBL, HASH)                               \
-        do {                                                            \
-                if (unlikely(!lockdep_rht_bucket_is_held(TBL, HASH))) { \
-                        debug_dump_table(HT, TBL, HASH);                \
-                        BUG();                                          \
-                }                                                       \
-        } while (0)
 
 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
 {
@@ -151,30 +48,18 @@ 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;
 }
 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
 #else
 #define ASSERT_RHT_MUTEX(HT)
-#define ASSERT_BUCKET_LOCK(HT, TBL, HASH)
 #endif
 
 
-static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n)
-{
-        struct rhash_head __rcu **pprev;
-
-        for (pprev = &tbl->buckets[n];
-             !rht_is_a_nulls(rht_dereference_bucket(*pprev, tbl, n));
-             pprev = &rht_dereference_bucket(*pprev, tbl, n)->next)
-                ;
-
-        return pprev;
-}
-
-static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl)
+static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
+                              gfp_t gfp)
 {
         unsigned int i, size;
 #if defined(CONFIG_PROVE_LOCKING)
@@ -191,12 +76,13 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl)
 
         if (sizeof(spinlock_t) != 0) {
 #ifdef CONFIG_NUMA
-                if (size * sizeof(spinlock_t) > PAGE_SIZE)
+                if (size * sizeof(spinlock_t) > PAGE_SIZE &&
+                    gfp == GFP_KERNEL)
                         tbl->locks = vmalloc(size * sizeof(spinlock_t));
                 else
 #endif
                 tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
-                                           GFP_KERNEL);
+                                           gfp);
                 if (!tbl->locks)
                         return -ENOMEM;
                 for (i = 0; i < size; i++)
@@ -215,153 +101,181 @@ static void bucket_table_free(const struct bucket_table *tbl)
         kvfree(tbl);
 }
 
+static void bucket_table_free_rcu(struct rcu_head *head)
+{
+        bucket_table_free(container_of(head, struct bucket_table, rcu));
+}
+
 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
-                                               size_t nbuckets)
+                                               size_t nbuckets,
+                                               gfp_t gfp)
 {
         struct bucket_table *tbl = NULL;
         size_t size;
         int i;
 
         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
-        if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
-                tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY);
-        if (tbl == NULL)
+        if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) ||
+            gfp != GFP_KERNEL)
+                tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
+        if (tbl == NULL && gfp == GFP_KERNEL)
                 tbl = vzalloc(size);
         if (tbl == NULL)
                 return NULL;
 
         tbl->size = nbuckets;
 
-        if (alloc_bucket_locks(ht, tbl) < 0) {
+        if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
                 bucket_table_free(tbl);
                 return NULL;
         }
 
+        INIT_LIST_HEAD(&tbl->walkers);
+
+        get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
+
         for (i = 0; i < nbuckets; i++)
                 INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
 
         return tbl;
 }
 
-/**
- * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
- * @ht:         hash table
- * @new_size:   new table size
- */
-static bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
+static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
+                                                  struct bucket_table *tbl)
 {
-        /* Expand table when exceeding 75% load */
-        return atomic_read(&ht->nelems) > (new_size / 4 * 3) &&
-               (!ht->p.max_shift || atomic_read(&ht->shift) < ht->p.max_shift);
-}
+        struct bucket_table *new_tbl;
 
-/**
- * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
- * @ht:         hash table
- * @new_size:   new table size
- */
-static bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
-{
-        /* Shrink table beneath 30% load */
-        return atomic_read(&ht->nelems) < (new_size * 3 / 10) &&
-               (atomic_read(&ht->shift) > ht->p.min_shift);
-}
+        do {
+                new_tbl = tbl;
+                tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+        } while (tbl);
 
-static void lock_buckets(struct bucket_table *new_tbl,
-                         struct bucket_table *old_tbl, unsigned int hash)
-        __acquires(old_bucket_lock)
-{
-        spin_lock_bh(bucket_lock(old_tbl, hash));
-        if (new_tbl != old_tbl)
-                spin_lock_bh_nested(bucket_lock(new_tbl, hash),
-                                    RHT_LOCK_NESTED);
+        return new_tbl;
 }
 
-static void unlock_buckets(struct bucket_table *new_tbl,
-                           struct bucket_table *old_tbl, unsigned int hash)
-        __releases(old_bucket_lock)
+static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
 {
-        if (new_tbl != old_tbl)
-                spin_unlock_bh(bucket_lock(new_tbl, hash));
-        spin_unlock_bh(bucket_lock(old_tbl, 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 *head, *next, *entry;
+        spinlock_t *new_bucket_lock;
+        unsigned int new_hash;
+
+        rht_for_each(entry, old_tbl, old_hash) {
+                err = 0;
+                next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
+
+                if (rht_is_a_nulls(next))
+                        break;
+
+                pprev = &entry->next;
+        }
+
+        if (err)
+                goto out;
+
+        new_hash = head_hashfn(ht, new_tbl, entry);
+
+        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],
+                                      new_tbl, new_hash);
+
+        if (rht_is_a_nulls(head))
+                INIT_RHT_NULLS_HEAD(entry->next, ht, new_hash);
+        else
+                RCU_INIT_POINTER(entry->next, head);
+
+        rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
+        spin_unlock(new_bucket_lock);
+
+        rcu_assign_pointer(*pprev, next);
+
+out:
+        return err;
 }
 
-/**
- * Unlink entries on bucket which hash to different bucket.
- *
- * Returns true if no more work needs to be performed on the bucket.
- */
-static bool hashtable_chain_unzip(struct rhashtable *ht,
-                                  const struct bucket_table *new_tbl,
-                                  struct bucket_table *old_tbl,
-                                  size_t old_hash)
+static void rhashtable_rehash_chain(struct rhashtable *ht,
+                                    unsigned int old_hash)
 {
-        struct rhash_head *he, *p, *next;
-        unsigned int new_hash, new_hash2;
-
-        ASSERT_BUCKET_LOCK(ht, old_tbl, old_hash);
+        struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
+        spinlock_t *old_bucket_lock;
 
-        /* Old bucket empty, no work needed. */
-        p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl,
-                                   old_hash);
-        if (rht_is_a_nulls(p))
-                return false;
+        old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
 
-        new_hash = head_hashfn(ht, new_tbl, p);
-        ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash);
+        spin_lock_bh(old_bucket_lock);
+        while (!rhashtable_rehash_one(ht, old_hash))
+                ;
+        old_tbl->rehash++;
+        spin_unlock_bh(old_bucket_lock);
+}
 
-        /* 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;
-         */
-        rht_for_each_continue(he, p->next, old_tbl, old_hash) {
-                new_hash2 = head_hashfn(ht, new_tbl, he);
-                ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash2);
+static int rhashtable_rehash_attach(struct rhashtable *ht,
+                                    struct bucket_table *old_tbl,
+                                    struct bucket_table *new_tbl)
+{
+        /* Protect future_tbl using the first bucket lock. */
+        spin_lock_bh(old_tbl->locks);
 
-                if (new_hash != new_hash2)
-                        break;
-                p = he;
+        /* Did somebody beat us to it? */
+        if (rcu_access_pointer(old_tbl->future_tbl)) {
+                spin_unlock_bh(old_tbl->locks);
+                return -EEXIST;
         }
-        rcu_assign_pointer(old_tbl->buckets[old_hash], p->next);
 
-        /* Find the subsequent node which does hash to the same
-         * bucket as node P, or NULL if no such node exists.
+        /* Make insertions go into the new, empty table right away. Deletions
+         * and lookups will be attempted in both tables until we synchronize.
          */
-        INIT_RHT_NULLS_HEAD(next, ht, old_hash);
-        if (!rht_is_a_nulls(he)) {
-                rht_for_each_continue(he, he->next, old_tbl, old_hash) {
-                        if (head_hashfn(ht, new_tbl, he) == new_hash) {
-                                next = he;
-                                break;
-                        }
-                }
-        }
+        rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
 
-        /* Set p's next pointer to that subsequent node pointer,
-         * bypassing the nodes which do not hash to p's bucket
-         */
-        rcu_assign_pointer(p->next, next);
+        /* Ensure the new table is visible to readers. */
+        smp_wmb();
 
-        p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl,
-                                   old_hash);
+        spin_unlock_bh(old_tbl->locks);
 
-        return !rht_is_a_nulls(p);
+        return 0;
 }
 
-static void link_old_to_new(struct rhashtable *ht, struct bucket_table *new_tbl,
-                            unsigned int new_hash, struct rhash_head *entry)
+static int rhashtable_rehash_table(struct rhashtable *ht)
 {
-        ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash);
+        struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
+        struct bucket_table *new_tbl;
+        struct rhashtable_walker *walker;
+        unsigned int old_hash;
+
+        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);
+
+        /* Publish the new table pointer. */
+        rcu_assign_pointer(ht->tbl, new_tbl);
+
+        spin_lock(&ht->lock);
+        list_for_each_entry(walker, &old_tbl->walkers, list)
+                walker->tbl = NULL;
+        spin_unlock(&ht->lock);
 
-        rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry);
+        /* Wait for readers. All new readers will see the new
+         * table, and thus no references to the old table will
+         * remain.
+         */
+        call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
+
+        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
- * while keeping them on both lists until the end of the RCU grace period.
+ * 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.
@@ -372,89 +286,32 @@ static void link_old_to_new(struct rhashtable *ht, struct bucket_table *new_tbl,
  * 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)
+static int rhashtable_expand(struct rhashtable *ht)
 {
         struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
-        struct rhash_head *he;
-        unsigned int new_hash, old_hash;
-        bool complete = false;
+        int err;
 
         ASSERT_RHT_MUTEX(ht);
 
-        new_tbl = bucket_table_alloc(ht, old_tbl->size * 2);
+        old_tbl = rhashtable_last_table(ht, old_tbl);
+
+        new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
         if (new_tbl == NULL)
                 return -ENOMEM;
 
-        atomic_inc(&ht->shift);
-
-        /* 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 (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
-                old_hash = rht_bucket_index(old_tbl, new_hash);
-                lock_buckets(new_tbl, old_tbl, new_hash);
-                rht_for_each(he, old_tbl, old_hash) {
-                        if (head_hashfn(ht, new_tbl, he) == new_hash) {
-                                link_old_to_new(ht, new_tbl, new_hash, he);
-                                break;
-                        }
-                }
-                unlock_buckets(new_tbl, old_tbl, new_hash);
-                cond_resched();
-        }
-
-        /* Unzip interleaved hash chains */
-        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.
-                 */
-                synchronize_rcu();
-
-                /* For each bucket in the old table (each of which
-                 * contains items from multiple buckets of the new
-                 * table): ...
-                 */
-                complete = true;
-                for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
-                        lock_buckets(new_tbl, old_tbl, old_hash);
-
-                        if (hashtable_chain_unzip(ht, new_tbl, old_tbl,
-                                                  old_hash))
-                                complete = false;
-
-                        unlock_buckets(new_tbl, old_tbl, old_hash);
-                        cond_resched();
-                }
-        }
+        err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
+        if (err)
+                bucket_table_free(new_tbl);
 
-        rcu_assign_pointer(ht->tbl, new_tbl);
-        synchronize_rcu();
-
-        bucket_table_free(old_tbl);
-        return 0;
+        return err;
 }
-EXPORT_SYMBOL_GPL(rhashtable_expand);
 
 /**
  * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
  * @ht:         the hash table to shrink
  *
- * 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.
+ * This function shrinks the hash table to fit, i.e., the smallest
+ * size would not cause it to expand right away automatically.
  *
  * The caller must ensure that no concurrent resizing occurs by holding
  * ht->mutex.
@@ -465,395 +322,146 @@ EXPORT_SYMBOL_GPL(rhashtable_expand);
  * 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)
+static int rhashtable_shrink(struct rhashtable *ht)
 {
-        struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht);
-        unsigned int new_hash;
+        struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+        unsigned int size;
+        int err;
 
         ASSERT_RHT_MUTEX(ht);
 
-        new_tbl = bucket_table_alloc(ht, tbl->size / 2);
-        if (new_tbl == NULL)
-                return -ENOMEM;
-
-        rcu_assign_pointer(ht->future_tbl, new_tbl);
-        synchronize_rcu();
-
-        /* 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.
-         */
-        for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
-                lock_buckets(new_tbl, tbl, new_hash);
-
-                rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
-                                   tbl->buckets[new_hash]);
-                ASSERT_BUCKET_LOCK(ht, tbl, new_hash + new_tbl->size);
-                rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
-                                   tbl->buckets[new_hash + new_tbl->size]);
+        size = roundup_pow_of_two(atomic_read(&ht->nelems) * 3 / 2);
+        if (size < ht->p.min_size)
+                size = ht->p.min_size;
 
-                unlock_buckets(new_tbl, tbl, new_hash);
-                cond_resched();
-        }
+        if (old_tbl->size <= size)
+                return 0;
 
-        /* Publish the new, valid hash table */
-        rcu_assign_pointer(ht->tbl, new_tbl);
-        atomic_dec(&ht->shift);
+        if (rht_dereference(old_tbl->future_tbl, ht))
+                return -EEXIST;
 
-        /* Wait for readers. No new readers will have references to the
-         * old hash table.
-         */
-        synchronize_rcu();
+        new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
+        if (new_tbl == NULL)
+                return -ENOMEM;
 
-        bucket_table_free(tbl);
+        err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
+        if (err)
+                bucket_table_free(new_tbl);
 
-        return 0;
+        return err;
 }
-EXPORT_SYMBOL_GPL(rhashtable_shrink);
 
 static void rht_deferred_worker(struct work_struct *work)
 {
         struct rhashtable *ht;
         struct bucket_table *tbl;
-        struct rhashtable_walker *walker;
+        int err = 0;
 
         ht = container_of(work, struct rhashtable, run_work);
         mutex_lock(&ht->mutex);
-        if (ht->being_destroyed)
-                goto unlock;
 
         tbl = rht_dereference(ht->tbl, ht);
+        tbl = rhashtable_last_table(ht, tbl);
 
-        list_for_each_entry(walker, &ht->walkers, list)
-                walker->resize = true;
-
-        if (rht_grow_above_75(ht, tbl->size))
+        if (rht_grow_above_75(ht, tbl))
                 rhashtable_expand(ht);
-        else if (rht_shrink_below_30(ht, tbl->size))
+        else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
                 rhashtable_shrink(ht);
-unlock:
-        mutex_unlock(&ht->mutex);
-}
 
-static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
-                                struct bucket_table *tbl,
-                                const struct bucket_table *old_tbl, u32 hash)
-{
-        bool no_resize_running = tbl == old_tbl;
-        struct rhash_head *head;
+        err = rhashtable_rehash_table(ht);
 
-        hash = rht_bucket_index(tbl, hash);
-        head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
-
-        ASSERT_BUCKET_LOCK(ht, tbl, hash);
-
-        if (rht_is_a_nulls(head))
-                INIT_RHT_NULLS_HEAD(obj->next, ht, hash);
-        else
-                RCU_INIT_POINTER(obj->next, head);
-
-        rcu_assign_pointer(tbl->buckets[hash], obj);
+        mutex_unlock(&ht->mutex);
 
-        atomic_inc(&ht->nelems);
-        if (no_resize_running && rht_grow_above_75(ht, tbl->size))
+        if (err)
                 schedule_work(&ht->run_work);
 }
 
-/**
- * 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)
+static bool rhashtable_check_elasticity(struct rhashtable *ht,
+                                        struct bucket_table *tbl,
+                                        unsigned int hash)
 {
-        struct bucket_table *tbl, *old_tbl;
-        unsigned hash;
-
-        rcu_read_lock();
-
-        tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        old_tbl = rht_dereference_rcu(ht->tbl, ht);
-        hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
+        unsigned int elasticity = ht->elasticity;
+        struct rhash_head *head;
 
-        lock_buckets(tbl, old_tbl, hash);
-        __rhashtable_insert(ht, obj, tbl, old_tbl, hash);
-        unlock_buckets(tbl, old_tbl, hash);
+        rht_for_each(head, tbl, hash)
+                if (!--elasticity)
+                        return true;
 
-        rcu_read_unlock();
+        return false;
 }
-EXPORT_SYMBOL_GPL(rhashtable_insert);
 
-/**
- * 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)
+int rhashtable_insert_rehash(struct rhashtable *ht)
 {
-        struct bucket_table *tbl, *new_tbl, *old_tbl;
-        struct rhash_head __rcu **pprev;
-        struct rhash_head *he, *he2;
-        unsigned int hash, new_hash;
-        bool ret = false;
+        struct bucket_table *old_tbl;
+        struct bucket_table *new_tbl;
+        struct bucket_table *tbl;
+        unsigned int size;
+        int err;
 
-        rcu_read_lock();
         old_tbl = rht_dereference_rcu(ht->tbl, ht);
-        tbl = new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        new_hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
-
-        lock_buckets(new_tbl, old_tbl, new_hash);
-restart:
-        hash = rht_bucket_index(tbl, new_hash);
-        pprev = &tbl->buckets[hash];
-        rht_for_each(he, tbl, hash) {
-                if (he != obj) {
-                        pprev = &he->next;
-                        continue;
-                }
-
-                ASSERT_BUCKET_LOCK(ht, tbl, hash);
-
-                if (old_tbl->size > new_tbl->size && tbl == old_tbl &&
-                    !rht_is_a_nulls(obj->next) &&
-                    head_hashfn(ht, tbl, obj->next) != hash) {
-                        rcu_assign_pointer(*pprev, (struct rhash_head *) rht_marker(ht, hash));
-                } else if (unlikely(old_tbl->size < new_tbl->size && tbl == new_tbl)) {
-                        rht_for_each_continue(he2, obj->next, tbl, hash) {
-                                if (head_hashfn(ht, tbl, he2) == hash) {
-                                        rcu_assign_pointer(*pprev, he2);
-                                        goto found;
-                                }
-                        }
-
-                        rcu_assign_pointer(*pprev, (struct rhash_head *) rht_marker(ht, hash));
-                } else {
-                        rcu_assign_pointer(*pprev, obj->next);
-                }
-
-found:
-                ret = true;
-                break;
-        }
-
-        /* The entry may be linked in either 'tbl', 'future_tbl', or both.
-         * 'future_tbl' only exists for a short period of time during
-         * resizing. Thus traversing both is fine and the added cost is
-         * very rare.
-         */
-        if (tbl != old_tbl) {
-                tbl = old_tbl;
-                goto restart;
-        }
-
-        unlock_buckets(new_tbl, old_tbl, new_hash);
-
-        if (ret) {
-                bool no_resize_running = new_tbl == old_tbl;
-
-                atomic_dec(&ht->nelems);
-                if (no_resize_running && rht_shrink_below_30(ht, new_tbl->size))
-                        schedule_work(&ht->run_work);
-        }
-
-        rcu_read_unlock();
+        tbl = rhashtable_last_table(ht, old_tbl);
 
-        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, *old_tbl;
-        struct rhash_head *he;
-        u32 hash;
+        size = tbl->size;
 
-        rcu_read_lock();
+        if (rht_grow_above_75(ht, tbl))
+                size *= 2;
+        /* More than two rehashes (not resizes) detected. */
+        else if (WARN_ON(old_tbl != tbl && old_tbl->size == size))
+                return -EBUSY;
 
-        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 (!compare(rht_obj(ht, he), arg))
-                        continue;
-                rcu_read_unlock();
-                return rht_obj(ht, he);
-        }
+        new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
+        if (new_tbl == NULL)
+                return -ENOMEM;
 
-        if (unlikely(tbl != old_tbl)) {
-                tbl = old_tbl;
-                goto restart;
-        }
-        rcu_read_unlock();
+        err = rhashtable_rehash_attach(ht, tbl, new_tbl);
+        if (err) {
+                bucket_table_free(new_tbl);
+                if (err == -EEXIST)
+                        err = 0;
+        } else
+                schedule_work(&ht->run_work);
 
-        return NULL;
+        return err;
 }
-EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
+EXPORT_SYMBOL_GPL(rhashtable_insert_rehash);
 
-/**
- * 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)
+int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
+                           struct rhash_head *obj,
+                           struct bucket_table *tbl)
 {
-        struct rhashtable_compare_arg arg = {
-                .ht = ht,
-                .key = rht_obj(ht, obj) + ht->p.key_offset,
-        };
+        struct rhash_head *head;
+        unsigned int hash;
+        int err;
 
-        BUG_ON(!ht->p.key_len);
+        tbl = rhashtable_last_table(ht, tbl);
+        hash = head_hashfn(ht, tbl, obj);
+        spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
 
-        return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare,
-                                                &arg);
-}
-EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
+        err = -EEXIST;
+        if (key && rhashtable_lookup_fast(ht, key, ht->p))
+                goto exit;
 
-/**
- * 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)
-{
-        struct bucket_table *new_tbl, *old_tbl;
-        u32 new_hash;
-        bool success = true;
+        err = -EAGAIN;
+        if (rhashtable_check_elasticity(ht, tbl, hash) ||
+            rht_grow_above_100(ht, tbl))
+                goto exit;
 
-        BUG_ON(!ht->p.key_len);
+        err = 0;
 
-        rcu_read_lock();
-        old_tbl = rht_dereference_rcu(ht->tbl, ht);
-        new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        new_hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
+        head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
 
-        lock_buckets(new_tbl, old_tbl, new_hash);
+        RCU_INIT_POINTER(obj->next, head);
 
-        if (rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset,
-                                      compare, arg)) {
-                success = false;
-                goto exit;
-        }
+        rcu_assign_pointer(tbl->buckets[hash], obj);
 
-        __rhashtable_insert(ht, obj, new_tbl, old_tbl, new_hash);
+        atomic_inc(&ht->nelems);
 
 exit:
-        unlock_buckets(new_tbl, old_tbl, new_hash);
-        rcu_read_unlock();
+        spin_unlock(rht_bucket_lock(tbl, hash));
 
-        return success;
+        return err;
 }
-EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert);
+EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
 
 /**
  * rhashtable_walk_init - Initialise an iterator
@@ -887,11 +495,9 @@ int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
         if (!iter->walker)
                 return -ENOMEM;
 
-        INIT_LIST_HEAD(&iter->walker->list);
-        iter->walker->resize = false;
-
         mutex_lock(&ht->mutex);
-        list_add(&iter->walker->list, &ht->walkers);
+        iter->walker->tbl = rht_dereference(ht->tbl, ht);
+        list_add(&iter->walker->list, &iter->walker->tbl->walkers);
         mutex_unlock(&ht->mutex);
 
         return 0;
@@ -907,7 +513,8 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_init);
 void rhashtable_walk_exit(struct rhashtable_iter *iter)
 {
         mutex_lock(&iter->ht->mutex);
-        list_del(&iter->walker->list);
+        if (iter->walker->tbl)
+                list_del(&iter->walker->list);
         mutex_unlock(&iter->ht->mutex);
         kfree(iter->walker);
 }
@@ -928,13 +535,21 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
  * by calling rhashtable_walk_next.
  */
 int rhashtable_walk_start(struct rhashtable_iter *iter)
+        __acquires(RCU)
 {
+        struct rhashtable *ht = iter->ht;
+
+        mutex_lock(&ht->mutex);
+
+        if (iter->walker->tbl)
+                list_del(&iter->walker->list);
+
         rcu_read_lock();
 
-        if (iter->walker->resize) {
-                iter->slot = 0;
-                iter->skip = 0;
-                iter->walker->resize = false;
+        mutex_unlock(&ht->mutex);
+
+        if (!iter->walker->tbl) {
+                iter->walker->tbl = rht_dereference_rcu(ht->tbl, ht);
                 return -EAGAIN;
         }
 
@@ -956,13 +571,11 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_start);
  */
 void *rhashtable_walk_next(struct rhashtable_iter *iter)
 {
-        const struct bucket_table *tbl;
+        struct bucket_table *tbl = iter->walker->tbl;
         struct rhashtable *ht = iter->ht;
         struct rhash_head *p = iter->p;
         void *obj = NULL;
 
-        tbl = rht_dereference_rcu(ht->tbl, ht);
-
         if (p) {
                 p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);
                 goto next;
@@ -988,17 +601,20 @@ next:
                 iter->skip = 0;
         }
 
-        iter->p = NULL;
+        /* Ensure we see any new tables. */
+        smp_rmb();
 
-out:
-        if (iter->walker->resize) {
-                iter->p = NULL;
+        iter->walker->tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+        if (iter->walker->tbl) {
                 iter->slot = 0;
                 iter->skip = 0;
-                iter->walker->resize = false;
                 return ERR_PTR(-EAGAIN);
         }
 
+        iter->p = NULL;
+
+out:
+
         return obj;
 }
 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
@@ -1010,16 +626,39 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_next);
  * Finish a hash table walk.
  */
 void rhashtable_walk_stop(struct rhashtable_iter *iter)
+        __releases(RCU)
 {
-        rcu_read_unlock();
+        struct rhashtable *ht;
+        struct bucket_table *tbl = iter->walker->tbl;
+
+        if (!tbl)
+                goto out;
+
+        ht = iter->ht;
+
+        spin_lock(&ht->lock);
+        if (tbl->rehash < tbl->size)
+                list_add(&iter->walker->list, &tbl->walkers);
+        else
+                iter->walker->tbl = NULL;
+        spin_unlock(&ht->lock);
+
         iter->p = NULL;
+
+out:
+        rcu_read_unlock();
 }
 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),
-                   1UL << params->min_shift);
+                   (unsigned long)params->min_size);
+}
+
+static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
+{
+        return jhash2(key, length, seed);
 }
 
 /**
@@ -1052,7 +691,7 @@ static size_t rounded_hashtable_size(struct rhashtable_params *params)
  *      struct rhash_head       node;
  * };
  *
- * u32 my_hash_fn(const void *data, u32 seed)
+ * u32 my_hash_fn(const void *data, u32 len, u32 seed)
  * {
  *      struct test_obj *obj = data;
  *
@@ -1065,47 +704,74 @@ 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->obj_hashfn) ||
+            (params->obj_hashfn && !params->obj_cmpfn))
                 return -EINVAL;
 
         if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
                 return -EINVAL;
 
-        params->min_shift = max_t(size_t, params->min_shift,
-                                  ilog2(HASH_MIN_SIZE));
-
         if (params->nelem_hint)
                 size = rounded_hashtable_size(params);
 
         memset(ht, 0, sizeof(*ht));
         mutex_init(&ht->mutex);
+        spin_lock_init(&ht->lock);
         memcpy(&ht->p, params, sizeof(*params));
-        INIT_LIST_HEAD(&ht->walkers);
+
+        if (params->min_size)
+                ht->p.min_size = roundup_pow_of_two(params->min_size);
+
+        if (params->max_size)
+                ht->p.max_size = rounddown_pow_of_two(params->max_size);
+
+        ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
+
+        /* The maximum (not average) chain length grows with the
+         * size of the hash table, at a rate of (log N)/(log log N).
+         * The value of 16 is selected so that even if the hash
+         * table grew to 2^32 you would not expect the maximum
+         * chain length to exceed it unless we are under attack
+         * (or extremely unlucky).
+         *
+         * As this limit is only to detect attacks, we don't need
+         * to set it to a lower value as you'd need the chain
+         * length to vastly exceed 16 to have any real effect
+         * on the system.
+         */
+        if (!params->insecure_elasticity)
+                ht->elasticity = 16;
 
         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);
+        ht->key_len = ht->p.key_len;
+        if (!params->hashfn) {
+                ht->p.hashfn = jhash;
+
+                if (!(ht->key_len & (sizeof(u32) - 1))) {
+                        ht->key_len /= sizeof(u32);
+                        ht->p.hashfn = rhashtable_jhash2;
+                }
+        }
+
+        tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
         if (tbl == NULL)
                 return -ENOMEM;
 
         atomic_set(&ht->nelems, 0);
-        atomic_set(&ht->shift, ilog2(tbl->size));
-        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));
+        RCU_INIT_POINTER(ht->tbl, tbl);
 
         INIT_WORK(&ht->run_work, rht_deferred_worker);
 
@@ -1114,21 +780,53 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
 EXPORT_SYMBOL_GPL(rhashtable_init);
 
 /**
- * rhashtable_destroy - destroy hash table
+ * rhashtable_free_and_destroy - free elements and destroy hash table
  * @ht:         the hash table to destroy
+ * @free_fn:    callback to release resources of element
+ * @arg:        pointer passed to free_fn
+ *
+ * Stops an eventual async resize. If defined, invokes free_fn for each
+ * element to releasal resources. Please note that RCU protected
+ * readers may still be accessing the elements. Releasing of resources
+ * must occur in a compatible manner. Then frees the bucket array.
  *
- * Frees the bucket array. This function is not rcu safe, therefore the caller
- * has to make sure that no resizing may happen by unpublishing the hashtable
- * and waiting for the quiescent cycle before releasing the bucket array.
+ * This function will eventually sleep to wait for an async resize
+ * to complete. The caller is responsible that no further write operations
+ * occurs in parallel.
  */
-void rhashtable_destroy(struct rhashtable *ht)
+void rhashtable_free_and_destroy(struct rhashtable *ht,
+                                 void (*free_fn)(void *ptr, void *arg),
+                                 void *arg)
 {
-        ht->being_destroyed = true;
+        const struct bucket_table *tbl;
+        unsigned int i;
 
         cancel_work_sync(&ht->run_work);
 
         mutex_lock(&ht->mutex);
-        bucket_table_free(rht_dereference(ht->tbl, ht));
+        tbl = rht_dereference(ht->tbl, ht);
+        if (free_fn) {
+                for (i = 0; i < tbl->size; i++) {
+                        struct rhash_head *pos, *next;
+
+                        for (pos = rht_dereference(tbl->buckets[i], ht),
+                             next = !rht_is_a_nulls(pos) ?
+                                        rht_dereference(pos->next, ht) : NULL;
+                             !rht_is_a_nulls(pos);
+                             pos = next,
+                             next = !rht_is_a_nulls(pos) ?
+                                        rht_dereference(pos->next, ht) : NULL)
+                                free_fn(rht_obj(ht, pos), arg);
+                }
+        }
+
+        bucket_table_free(tbl);
         mutex_unlock(&ht->mutex);
 }
+EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
+
+void rhashtable_destroy(struct rhashtable *ht)
+{
+        return rhashtable_free_and_destroy(ht, NULL, NULL);
+}
 EXPORT_SYMBOL_GPL(rhashtable_destroy);