/*
* 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
#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)
{
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)
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++)
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.
* 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.
* 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
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;
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);
}
* 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;
}
*/
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;
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);
* 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);
}
/**
* 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;
*
* .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);
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);
git.openpandora.org / pandora-kernel.git / blobdiff