+// SPDX-License-Identifier: GPL-2.0-only
/*
* Resizable, Scalable, Concurrent Hash Table
*
* 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
- * published by the Free Software Foundation.
*/
#include <linux/atomic.h>
-#include <linux/cpumask.h>
#include <linux/kernel.h>
#include <linux/log2.h>
#include <linux/sched.h>
+#include <linux/rculist.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/jhash.h>
+#include <linux/overflow.h>
#include <linux/random.h>
#include <linux/rhashtable.h>
#include <linux/err.h>
+#include <linux/export.h>
#define HASH_DEFAULT_SIZE 64UL
#define HASH_MIN_SIZE 4U
-#define BUCKET_LOCKS_PER_CPU 32UL
+
+union nested_table {
+ union nested_table __rcu *table;
+ struct rhash_lock_head __rcu *bucket;
+};
static u32 head_hashfn(struct rhashtable *ht,
const struct bucket_table *tbl,
return rht_head_hashfn(ht, tbl, he, ht->p);
}
-static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
- gfp_t gfp)
-{
- unsigned int i, size;
- unsigned int nr_pcpus = num_possible_cpus();
+#ifdef CONFIG_PROVE_LOCKING
+#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
- nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
- size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
+int lockdep_rht_mutex_is_held(struct rhashtable *ht)
+{
+ return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
+}
+EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
- /* Never allocate more than 0.5 locks per bucket */
- size = min_t(unsigned int, size, tbl->size >> 1);
+int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
+{
+ if (!debug_locks)
+ return 1;
+ if (unlikely(tbl->nest))
+ return 1;
+ return bit_spin_is_locked(0, (unsigned long *)&tbl->buckets[hash]);
+}
+EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
+#else
+#define ASSERT_RHT_MUTEX(HT)
+#endif
- if (sizeof(spinlock_t) != 0) {
- tbl->locks = NULL;
- if (gfp != GFP_KERNEL)
- gfp |= __GFP_NOWARN | __GFP_NORETRY;
+static inline union nested_table *nested_table_top(
+ const struct bucket_table *tbl)
+{
+ /* The top-level bucket entry does not need RCU protection
+ * because it's set at the same time as tbl->nest.
+ */
+ return (void *)rcu_dereference_protected(tbl->buckets[0], 1);
+}
- if (!tbl->locks)
- tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
- gfp);
- if (!tbl->locks)
- return -ENOMEM;
- for (i = 0; i < size; i++)
- spin_lock_init(&tbl->locks[i]);
+static void nested_table_free(union nested_table *ntbl, unsigned int size)
+{
+ const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+ const unsigned int len = 1 << shift;
+ unsigned int i;
+
+ ntbl = rcu_dereference_protected(ntbl->table, 1);
+ if (!ntbl)
+ return;
+
+ if (size > len) {
+ size >>= shift;
+ for (i = 0; i < len; i++)
+ nested_table_free(ntbl + i, size);
}
- tbl->locks_mask = size - 1;
- return 0;
+ kfree(ntbl);
+}
+
+static void nested_bucket_table_free(const struct bucket_table *tbl)
+{
+ unsigned int size = tbl->size >> tbl->nest;
+ unsigned int len = 1 << tbl->nest;
+ union nested_table *ntbl;
+ unsigned int i;
+
+ ntbl = nested_table_top(tbl);
+
+ for (i = 0; i < len; i++)
+ nested_table_free(ntbl + i, size);
+
+ kfree(ntbl);
}
static void bucket_table_free(struct bucket_table *tbl)
{
- if (tbl)
- kvfree(tbl->locks);
+ if (tbl->nest)
+ nested_bucket_table_free(tbl);
kvfree(tbl);
}
bucket_table_free(container_of(head, struct bucket_table, rcu));
}
+static union nested_table *nested_table_alloc(struct rhashtable *ht,
+ union nested_table __rcu **prev,
+ bool leaf)
+{
+ union nested_table *ntbl;
+ int i;
+
+ ntbl = rcu_dereference(*prev);
+ if (ntbl)
+ return ntbl;
+
+ ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
+
+ if (ntbl && leaf) {
+ for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++)
+ INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
+ }
+
+ if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL)
+ return ntbl;
+ /* Raced with another thread. */
+ kfree(ntbl);
+ return rcu_dereference(*prev);
+}
+
+static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
+ size_t nbuckets,
+ gfp_t gfp)
+{
+ const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+ struct bucket_table *tbl;
+ size_t size;
+
+ if (nbuckets < (1 << (shift + 1)))
+ return NULL;
+
+ size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
+
+ tbl = kzalloc(size, gfp);
+ if (!tbl)
+ return NULL;
+
+ if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
+ false)) {
+ kfree(tbl);
+ return NULL;
+ }
+
+ tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
+
+ return tbl;
+}
+
static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
size_t nbuckets,
gfp_t gfp)
size_t size;
int i;
- size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
- 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 = kvzalloc(struct_size(tbl, buckets, nbuckets), gfp);
- tbl->size = nbuckets;
+ size = nbuckets;
- if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
- bucket_table_free(tbl);
- return NULL;
+ if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) {
+ tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
+ nbuckets = 0;
}
+ if (tbl == NULL)
+ return NULL;
+
+ tbl->size = size;
+
+ rcu_head_init(&tbl->rcu);
INIT_LIST_HEAD(&tbl->walkers);
- get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
+ tbl->hash_rnd = get_random_u32();
for (i = 0; i < nbuckets; i++)
- INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
+ INIT_RHT_NULLS_HEAD(tbl->buckets[i]);
return tbl;
}
return new_tbl;
}
-static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
+static int rhashtable_rehash_one(struct rhashtable *ht,
+ struct rhash_lock_head __rcu **bkt,
+ unsigned int old_hash)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
- struct bucket_table *new_tbl = rhashtable_last_table(ht,
- rht_dereference_rcu(old_tbl->future_tbl, ht));
- struct rhash_head __rcu **pprev = &old_tbl->buckets[old_hash];
- int err = -ENOENT;
+ struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl);
+ int err = -EAGAIN;
struct rhash_head *head, *next, *entry;
- spinlock_t *new_bucket_lock;
+ struct rhash_head __rcu **pprev = NULL;
unsigned int new_hash;
- rht_for_each(entry, old_tbl, old_hash) {
+ if (new_tbl->nest)
+ goto out;
+
+ err = -ENOENT;
+
+ rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash),
+ old_tbl, old_hash) {
err = 0;
next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
new_hash = head_hashfn(ht, new_tbl, entry);
- new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
+ rht_lock(new_tbl, &new_tbl->buckets[new_hash]);
- spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
- head = rht_dereference_bucket(new_tbl->buckets[new_hash],
- new_tbl, new_hash);
+ head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
RCU_INIT_POINTER(entry->next, head);
- rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
- spin_unlock(new_bucket_lock);
+ rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry);
- rcu_assign_pointer(*pprev, next);
+ if (pprev)
+ rcu_assign_pointer(*pprev, next);
+ else
+ /* Need to preserved the bit lock. */
+ rht_assign_locked(bkt, next);
out:
return err;
}
-static void rhashtable_rehash_chain(struct rhashtable *ht,
+static int rhashtable_rehash_chain(struct rhashtable *ht,
unsigned int old_hash)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
- spinlock_t *old_bucket_lock;
+ struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
+ int err;
- old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
+ if (!bkt)
+ return 0;
+ rht_lock(old_tbl, bkt);
- spin_lock_bh(old_bucket_lock);
- while (!rhashtable_rehash_one(ht, old_hash))
+ while (!(err = rhashtable_rehash_one(ht, bkt, old_hash)))
;
- old_tbl->rehash++;
- spin_unlock_bh(old_bucket_lock);
+
+ if (err == -ENOENT)
+ err = 0;
+ rht_unlock(old_tbl, bkt);
+
+ return err;
}
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);
-
- /* Did somebody beat us to it? */
- if (rcu_access_pointer(old_tbl->future_tbl)) {
- spin_unlock_bh(old_tbl->locks);
- return -EEXIST;
- }
-
/* Make insertions go into the new, empty table right away. Deletions
* and lookups will be attempted in both tables until we synchronize.
+ * As cmpxchg() provides strong barriers, we do not need
+ * rcu_assign_pointer().
*/
- rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
- spin_unlock_bh(old_tbl->locks);
+ if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL,
+ new_tbl) != NULL)
+ return -EEXIST;
return 0;
}
struct bucket_table *new_tbl;
struct rhashtable_walker *walker;
unsigned int old_hash;
+ int err;
new_tbl = rht_dereference(old_tbl->future_tbl, ht);
if (!new_tbl)
return 0;
- for (old_hash = 0; old_hash < old_tbl->size; old_hash++)
- rhashtable_rehash_chain(ht, old_hash);
+ for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
+ err = rhashtable_rehash_chain(ht, old_hash);
+ if (err)
+ return err;
+ cond_resched();
+ }
/* 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);
/* Wait for readers. All new readers will see the new
* table, and thus no references to the old table will
* remain.
+ * We do this inside the locked region so that
+ * rhashtable_walk_stop() can use rcu_head_after_call_rcu()
+ * to check if it should not re-link the table.
*/
call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
+ spin_unlock(&ht->lock);
return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
}
-static int rhashtable_expand(struct rhashtable *ht)
+static int rhashtable_rehash_alloc(struct rhashtable *ht,
+ struct bucket_table *old_tbl,
+ unsigned int size)
{
- struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+ struct bucket_table *new_tbl;
int err;
- old_tbl = rhashtable_last_table(ht, old_tbl);
+ ASSERT_RHT_MUTEX(ht);
- new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
+ new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
if (new_tbl == NULL)
return -ENOMEM;
return err;
}
+/**
+ * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
+ * @ht: the hash table to shrink
+ *
+ * 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.
+ *
+ * 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.
+ */
static int rhashtable_shrink(struct rhashtable *ht)
{
- struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
+ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
unsigned int nelems = atomic_read(&ht->nelems);
unsigned int size = 0;
- int err;
if (nelems)
size = roundup_pow_of_two(nelems * 3 / 2);
if (rht_dereference(old_tbl->future_tbl, ht))
return -EEXIST;
- new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
- if (new_tbl == NULL)
- return -ENOMEM;
-
- err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
- if (err)
- bucket_table_free(new_tbl);
-
- return err;
+ return rhashtable_rehash_alloc(ht, old_tbl, size);
}
static void rht_deferred_worker(struct work_struct *work)
tbl = rhashtable_last_table(ht, tbl);
if (rht_grow_above_75(ht, tbl))
- rhashtable_expand(ht);
+ err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
- rhashtable_shrink(ht);
+ err = rhashtable_shrink(ht);
+ else if (tbl->nest)
+ err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
+
+ if (!err || err == -EEXIST) {
+ int nerr;
- err = rhashtable_rehash_table(ht);
+ nerr = rhashtable_rehash_table(ht);
+ err = err ?: nerr;
+ }
mutex_unlock(&ht->mutex);
schedule_work(&ht->run_work);
}
-static bool rhashtable_check_elasticity(struct rhashtable *ht,
- struct bucket_table *tbl,
- unsigned int hash)
-{
- unsigned int elasticity = ht->elasticity;
- struct rhash_head *head;
-
- rht_for_each(head, tbl, hash)
- if (!--elasticity)
- return true;
-
- return false;
-}
-
-int rhashtable_insert_rehash(struct rhashtable *ht,
- struct bucket_table *tbl)
+static int rhashtable_insert_rehash(struct rhashtable *ht,
+ struct bucket_table *tbl)
{
struct bucket_table *old_tbl;
struct bucket_table *new_tbl;
err = -ENOMEM;
- new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
+ new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
if (new_tbl == NULL)
goto fail;
fail:
/* Do not fail the insert if someone else did a rehash. */
- if (likely(rcu_dereference_raw(tbl->future_tbl)))
+ if (likely(rcu_access_pointer(tbl->future_tbl)))
return 0;
/* Schedule async rehash to retry allocation in process context. */
return err;
}
-struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
- const void *key,
- struct rhash_head *obj,
- struct bucket_table *tbl)
+static void *rhashtable_lookup_one(struct rhashtable *ht,
+ struct rhash_lock_head __rcu **bkt,
+ struct bucket_table *tbl, unsigned int hash,
+ const void *key, struct rhash_head *obj)
{
+ struct rhashtable_compare_arg arg = {
+ .ht = ht,
+ .key = key,
+ };
+ struct rhash_head __rcu **pprev = NULL;
struct rhash_head *head;
- unsigned int hash;
- int err;
+ int elasticity;
+
+ elasticity = RHT_ELASTICITY;
+ rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {
+ struct rhlist_head *list;
+ struct rhlist_head *plist;
+
+ elasticity--;
+ if (!key ||
+ (ht->p.obj_cmpfn ?
+ ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
+ rhashtable_compare(&arg, rht_obj(ht, head)))) {
+ pprev = &head->next;
+ continue;
+ }
- tbl = rhashtable_last_table(ht, tbl);
- hash = head_hashfn(ht, tbl, obj);
- spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
+ if (!ht->rhlist)
+ return rht_obj(ht, head);
- err = -EEXIST;
- if (key && rhashtable_lookup_fast(ht, key, ht->p))
- goto exit;
+ list = container_of(obj, struct rhlist_head, rhead);
+ plist = container_of(head, struct rhlist_head, rhead);
- err = -E2BIG;
- if (unlikely(rht_grow_above_max(ht, tbl)))
- goto exit;
+ RCU_INIT_POINTER(list->next, plist);
+ head = rht_dereference_bucket(head->next, tbl, hash);
+ RCU_INIT_POINTER(list->rhead.next, head);
+ if (pprev)
+ rcu_assign_pointer(*pprev, obj);
+ else
+ /* Need to preserve the bit lock */
+ rht_assign_locked(bkt, obj);
+
+ return NULL;
+ }
+
+ if (elasticity <= 0)
+ return ERR_PTR(-EAGAIN);
+
+ return ERR_PTR(-ENOENT);
+}
+
+static struct bucket_table *rhashtable_insert_one(
+ struct rhashtable *ht, struct rhash_lock_head __rcu **bkt,
+ struct bucket_table *tbl, unsigned int hash, struct rhash_head *obj,
+ void *data)
+{
+ struct bucket_table *new_tbl;
+ struct rhash_head *head;
+
+ if (!IS_ERR_OR_NULL(data))
+ return ERR_PTR(-EEXIST);
+
+ if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
+ return ERR_CAST(data);
+
+ new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ if (new_tbl)
+ return new_tbl;
+
+ if (PTR_ERR(data) != -ENOENT)
+ return ERR_CAST(data);
- err = -EAGAIN;
- if (rhashtable_check_elasticity(ht, tbl, hash) ||
- rht_grow_above_100(ht, tbl))
- goto exit;
+ if (unlikely(rht_grow_above_max(ht, tbl)))
+ return ERR_PTR(-E2BIG);
- err = 0;
+ if (unlikely(rht_grow_above_100(ht, tbl)))
+ return ERR_PTR(-EAGAIN);
- head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
+ head = rht_ptr(bkt, tbl, hash);
RCU_INIT_POINTER(obj->next, head);
+ if (ht->rhlist) {
+ struct rhlist_head *list;
- rcu_assign_pointer(tbl->buckets[hash], obj);
+ list = container_of(obj, struct rhlist_head, rhead);
+ RCU_INIT_POINTER(list->next, NULL);
+ }
+
+ /* bkt is always the head of the list, so it holds
+ * the lock, which we need to preserve
+ */
+ rht_assign_locked(bkt, obj);
atomic_inc(&ht->nelems);
+ if (rht_grow_above_75(ht, tbl))
+ schedule_work(&ht->run_work);
+
+ return NULL;
+}
+
+static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
+ struct rhash_head *obj)
+{
+ struct bucket_table *new_tbl;
+ struct bucket_table *tbl;
+ struct rhash_lock_head __rcu **bkt;
+ unsigned int hash;
+ void *data;
+
+ new_tbl = rcu_dereference(ht->tbl);
+
+ do {
+ tbl = new_tbl;
+ hash = rht_head_hashfn(ht, tbl, obj, ht->p);
+ if (rcu_access_pointer(tbl->future_tbl))
+ /* Failure is OK */
+ bkt = rht_bucket_var(tbl, hash);
+ else
+ bkt = rht_bucket_insert(ht, tbl, hash);
+ if (bkt == NULL) {
+ new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ data = ERR_PTR(-EAGAIN);
+ } else {
+ rht_lock(tbl, bkt);
+ data = rhashtable_lookup_one(ht, bkt, tbl,
+ hash, key, obj);
+ new_tbl = rhashtable_insert_one(ht, bkt, tbl,
+ hash, obj, data);
+ if (PTR_ERR(new_tbl) != -EEXIST)
+ data = ERR_CAST(new_tbl);
+
+ rht_unlock(tbl, bkt);
+ }
+ } while (!IS_ERR_OR_NULL(new_tbl));
+
+ if (PTR_ERR(data) == -EAGAIN)
+ data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
+ -EAGAIN);
+
+ return data;
+}
+
+void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
+ struct rhash_head *obj)
+{
+ void *data;
+
+ do {
+ rcu_read_lock();
+ data = rhashtable_try_insert(ht, key, obj);
+ rcu_read_unlock();
+ } while (PTR_ERR(data) == -EAGAIN);
-exit:
- spin_unlock(rht_bucket_lock(tbl, hash));
+ return data;
+}
+EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
- if (err == 0)
+/**
+ * rhashtable_walk_enter - Initialise an iterator
+ * @ht: Table to walk over
+ * @iter: Hash table Iterator
+ *
+ * This function prepares a hash table walk.
+ *
+ * Note that if you restart a walk after rhashtable_walk_stop you
+ * may see the same object twice. Also, you may miss objects if
+ * there are removals in between rhashtable_walk_stop and the next
+ * call to rhashtable_walk_start.
+ *
+ * For a completely stable walk you should construct your own data
+ * structure outside the hash table.
+ *
+ * This function may be called from any process context, including
+ * non-preemptable context, but cannot be called from softirq or
+ * hardirq context.
+ *
+ * You must call rhashtable_walk_exit after this function returns.
+ */
+void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
+{
+ iter->ht = ht;
+ iter->p = NULL;
+ iter->slot = 0;
+ iter->skip = 0;
+ iter->end_of_table = 0;
+
+ spin_lock(&ht->lock);
+ iter->walker.tbl =
+ rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
+ list_add(&iter->walker.list, &iter->walker.tbl->walkers);
+ spin_unlock(&ht->lock);
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
+
+/**
+ * rhashtable_walk_exit - Free an iterator
+ * @iter: Hash table Iterator
+ *
+ * This function frees resources allocated by rhashtable_walk_enter.
+ */
+void rhashtable_walk_exit(struct rhashtable_iter *iter)
+{
+ spin_lock(&iter->ht->lock);
+ if (iter->walker.tbl)
+ list_del(&iter->walker.list);
+ spin_unlock(&iter->ht->lock);
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
+
+/**
+ * rhashtable_walk_start_check - Start a hash table walk
+ * @iter: Hash table iterator
+ *
+ * Start a hash table walk at the current iterator position. Note that we take
+ * the RCU lock in all cases including when we return an error. So you must
+ * always call rhashtable_walk_stop to clean up.
+ *
+ * Returns zero if successful.
+ *
+ * Returns -EAGAIN if resize event occured. Note that the iterator
+ * will rewind back to the beginning and you may use it immediately
+ * by calling rhashtable_walk_next.
+ *
+ * rhashtable_walk_start is defined as an inline variant that returns
+ * void. This is preferred in cases where the caller would ignore
+ * resize events and always continue.
+ */
+int rhashtable_walk_start_check(struct rhashtable_iter *iter)
+ __acquires(RCU)
+{
+ struct rhashtable *ht = iter->ht;
+ bool rhlist = ht->rhlist;
+
+ rcu_read_lock();
+
+ spin_lock(&ht->lock);
+ if (iter->walker.tbl)
+ list_del(&iter->walker.list);
+ spin_unlock(&ht->lock);
+
+ if (iter->end_of_table)
+ return 0;
+ if (!iter->walker.tbl) {
+ iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
+ iter->slot = 0;
+ iter->skip = 0;
+ return -EAGAIN;
+ }
+
+ if (iter->p && !rhlist) {
+ /*
+ * We need to validate that 'p' is still in the table, and
+ * if so, update 'skip'
+ */
+ struct rhash_head *p;
+ int skip = 0;
+ rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
+ skip++;
+ if (p == iter->p) {
+ iter->skip = skip;
+ goto found;
+ }
+ }
+ iter->p = NULL;
+ } else if (iter->p && rhlist) {
+ /* Need to validate that 'list' is still in the table, and
+ * if so, update 'skip' and 'p'.
+ */
+ struct rhash_head *p;
+ struct rhlist_head *list;
+ int skip = 0;
+ rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
+ for (list = container_of(p, struct rhlist_head, rhead);
+ list;
+ list = rcu_dereference(list->next)) {
+ skip++;
+ if (list == iter->list) {
+ iter->p = p;
+ iter->skip = skip;
+ goto found;
+ }
+ }
+ }
+ iter->p = NULL;
+ }
+found:
+ return 0;
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
+
+/**
+ * __rhashtable_walk_find_next - Find the next element in a table (or the first
+ * one in case of a new walk).
+ *
+ * @iter: Hash table iterator
+ *
+ * Returns the found object or NULL when the end of the table is reached.
+ *
+ * Returns -EAGAIN if resize event occurred.
+ */
+static void *__rhashtable_walk_find_next(struct rhashtable_iter *iter)
+{
+ struct bucket_table *tbl = iter->walker.tbl;
+ struct rhlist_head *list = iter->list;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+ bool rhlist = ht->rhlist;
+
+ if (!tbl)
return NULL;
- else if (err == -EAGAIN)
- return tbl;
+
+ for (; iter->slot < tbl->size; iter->slot++) {
+ int skip = iter->skip;
+
+ rht_for_each_rcu(p, tbl, iter->slot) {
+ if (rhlist) {
+ list = container_of(p, struct rhlist_head,
+ rhead);
+ do {
+ if (!skip)
+ goto next;
+ skip--;
+ list = rcu_dereference(list->next);
+ } while (list);
+
+ continue;
+ }
+ if (!skip)
+ break;
+ skip--;
+ }
+
+next:
+ if (!rht_is_a_nulls(p)) {
+ iter->skip++;
+ iter->p = p;
+ iter->list = list;
+ return rht_obj(ht, rhlist ? &list->rhead : p);
+ }
+
+ iter->skip = 0;
+ }
+
+ iter->p = NULL;
+
+ /* Ensure we see any new tables. */
+ smp_rmb();
+
+ iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+ if (iter->walker.tbl) {
+ iter->slot = 0;
+ iter->skip = 0;
+ return ERR_PTR(-EAGAIN);
+ } else {
+ iter->end_of_table = true;
+ }
+
+ return NULL;
+}
+
+/**
+ * rhashtable_walk_next - Return the next object and advance the iterator
+ * @iter: Hash table iterator
+ *
+ * Note that you must call rhashtable_walk_stop when you are finished
+ * with the walk.
+ *
+ * Returns the next object or NULL when the end of the table is reached.
+ *
+ * Returns -EAGAIN if resize event occurred. Note that the iterator
+ * will rewind back to the beginning and you may continue to use it.
+ */
+void *rhashtable_walk_next(struct rhashtable_iter *iter)
+{
+ struct rhlist_head *list = iter->list;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+ bool rhlist = ht->rhlist;
+
+ if (p) {
+ if (!rhlist || !(list = rcu_dereference(list->next))) {
+ p = rcu_dereference(p->next);
+ list = container_of(p, struct rhlist_head, rhead);
+ }
+ if (!rht_is_a_nulls(p)) {
+ iter->skip++;
+ iter->p = p;
+ iter->list = list;
+ return rht_obj(ht, rhlist ? &list->rhead : p);
+ }
+
+ /* At the end of this slot, switch to next one and then find
+ * next entry from that point.
+ */
+ iter->skip = 0;
+ iter->slot++;
+ }
+
+ return __rhashtable_walk_find_next(iter);
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_next);
+
+/**
+ * rhashtable_walk_peek - Return the next object but don't advance the iterator
+ * @iter: Hash table iterator
+ *
+ * Returns the next object or NULL when the end of the table is reached.
+ *
+ * Returns -EAGAIN if resize event occurred. Note that the iterator
+ * will rewind back to the beginning and you may continue to use it.
+ */
+void *rhashtable_walk_peek(struct rhashtable_iter *iter)
+{
+ struct rhlist_head *list = iter->list;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+
+ if (p)
+ return rht_obj(ht, ht->rhlist ? &list->rhead : p);
+
+ /* No object found in current iter, find next one in the table. */
+
+ if (iter->skip) {
+ /* A nonzero skip value points to the next entry in the table
+ * beyond that last one that was found. Decrement skip so
+ * we find the current value. __rhashtable_walk_find_next
+ * will restore the original value of skip assuming that
+ * the table hasn't changed.
+ */
+ iter->skip--;
+ }
+
+ return __rhashtable_walk_find_next(iter);
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
+
+/**
+ * rhashtable_walk_stop - Finish a hash table walk
+ * @iter: Hash table iterator
+ *
+ * Finish a hash table walk. Does not reset the iterator to the start of the
+ * hash table.
+ */
+void rhashtable_walk_stop(struct rhashtable_iter *iter)
+ __releases(RCU)
+{
+ struct rhashtable *ht;
+ struct bucket_table *tbl = iter->walker.tbl;
+
+ if (!tbl)
+ goto out;
+
+ ht = iter->ht;
+
+ spin_lock(&ht->lock);
+ if (rcu_head_after_call_rcu(&tbl->rcu, bucket_table_free_rcu))
+ /* This bucket table is being freed, don't re-link it. */
+ iter->walker.tbl = NULL;
else
- return ERR_PTR(err);
+ list_add(&iter->walker.list, &tbl->walkers);
+ spin_unlock(&ht->lock);
+
+out:
+ rcu_read_unlock();
}
+EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
static size_t rounded_hashtable_size(const struct rhashtable_params *params)
{
- return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
- (unsigned long)params->min_size);
+ size_t retsize;
+
+ if (params->nelem_hint)
+ retsize = max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
+ (unsigned long)params->min_size);
+ else
+ retsize = max(HASH_DEFAULT_SIZE,
+ (unsigned long)params->min_size);
+
+ return retsize;
}
static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
return jhash2(key, length, seed);
}
+/**
+ * rhashtable_init - initialize a new hash table
+ * @ht: hash table to be initialized
+ * @params: configuration parameters
+ *
+ * Initializes a new hash table based on the provided configuration
+ * parameters. A table can be configured either with a variable or
+ * fixed length key:
+ *
+ * Configuration Example 1: Fixed length keys
+ * struct test_obj {
+ * int key;
+ * void * my_member;
+ * struct rhash_head node;
+ * };
+ *
+ * struct rhashtable_params params = {
+ * .head_offset = offsetof(struct test_obj, node),
+ * .key_offset = offsetof(struct test_obj, key),
+ * .key_len = sizeof(int),
+ * .hashfn = jhash,
+ * };
+ *
+ * Configuration Example 2: Variable length keys
+ * struct test_obj {
+ * [...]
+ * struct rhash_head node;
+ * };
+ *
+ * u32 my_hash_fn(const void *data, u32 len, u32 seed)
+ * {
+ * struct test_obj *obj = data;
+ *
+ * return [... hash ...];
+ * }
+ *
+ * struct rhashtable_params params = {
+ * .head_offset = offsetof(struct test_obj, node),
+ * .hashfn = jhash,
+ * .obj_hashfn = my_hash_fn,
+ * };
+ */
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->obj_hashfn) ||
(params->obj_hashfn && !params->obj_cmpfn))
return -EINVAL;
- if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
- return -EINVAL;
-
memset(ht, 0, sizeof(*ht));
mutex_init(&ht->mutex);
spin_lock_init(&ht->lock);
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);
+ /* Cap total entries at 2^31 to avoid nelems overflow. */
+ ht->max_elems = 1u << 31;
- if (params->insecure_max_entries)
- ht->p.insecure_max_entries =
- rounddown_pow_of_two(params->insecure_max_entries);
- else
- ht->p.insecure_max_entries = ht->p.max_size * 2;
-
- ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
+ if (params->max_size) {
+ ht->p.max_size = rounddown_pow_of_two(params->max_size);
+ if (ht->p.max_size < ht->max_elems / 2)
+ ht->max_elems = ht->p.max_size * 2;
+ }
- if (params->nelem_hint)
- size = rounded_hashtable_size(&ht->p);
-
- /* 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;
+ ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
- if (params->locks_mul)
- ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
- else
- ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
+ size = rounded_hashtable_size(&ht->p);
ht->key_len = ht->p.key_len;
if (!params->hashfn) {
}
}
+ /*
+ * This is api initialization and thus we need to guarantee the
+ * initial rhashtable allocation. Upon failure, retry with the
+ * smallest possible size with __GFP_NOFAIL semantics.
+ */
tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
- if (tbl == NULL)
- return -ENOMEM;
+ if (unlikely(tbl == NULL)) {
+ size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
+ tbl = bucket_table_alloc(ht, size, GFP_KERNEL | __GFP_NOFAIL);
+ }
atomic_set(&ht->nelems, 0);
return 0;
}
+EXPORT_SYMBOL_GPL(rhashtable_init);
-void rhashtable_destroy(struct rhashtable *ht)
+/**
+ * rhltable_init - initialize a new hash list table
+ * @hlt: hash list table to be initialized
+ * @params: configuration parameters
+ *
+ * Initializes a new hash list table.
+ *
+ * See documentation for rhashtable_init.
+ */
+int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
{
- struct bucket_table *tbl;
+ int err;
+
+ err = rhashtable_init(&hlt->ht, params);
+ hlt->ht.rhlist = true;
+ return err;
+}
+EXPORT_SYMBOL_GPL(rhltable_init);
+
+static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
+ void (*free_fn)(void *ptr, void *arg),
+ void *arg)
+{
+ struct rhlist_head *list;
+
+ if (!ht->rhlist) {
+ free_fn(rht_obj(ht, obj), arg);
+ return;
+ }
+
+ list = container_of(obj, struct rhlist_head, rhead);
+ do {
+ obj = &list->rhead;
+ list = rht_dereference(list->next, ht);
+ free_fn(rht_obj(ht, obj), arg);
+ } while (list);
+}
+
+/**
+ * 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.
+ *
+ * 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_free_and_destroy(struct rhashtable *ht,
+ void (*free_fn)(void *ptr, void *arg),
+ void *arg)
+{
+ struct bucket_table *tbl, *next_tbl;
+ unsigned int i;
cancel_work_sync(&ht->run_work);
mutex_lock(&ht->mutex);
tbl = rht_dereference(ht->tbl, ht);
+restart:
+ if (free_fn) {
+ for (i = 0; i < tbl->size; i++) {
+ struct rhash_head *pos, *next;
+
+ cond_resched();
+ for (pos = rht_ptr_exclusive(rht_bucket(tbl, i)),
+ 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)
+ rhashtable_free_one(ht, pos, free_fn, arg);
+ }
+ }
+
+ next_tbl = rht_dereference(tbl->future_tbl, ht);
bucket_table_free(tbl);
+ if (next_tbl) {
+ tbl = next_tbl;
+ goto restart;
+ }
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);
+
+struct rhash_lock_head __rcu **__rht_bucket_nested(
+ const struct bucket_table *tbl, unsigned int hash)
+{
+ const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+ unsigned int index = hash & ((1 << tbl->nest) - 1);
+ unsigned int size = tbl->size >> tbl->nest;
+ unsigned int subhash = hash;
+ union nested_table *ntbl;
+
+ ntbl = nested_table_top(tbl);
+ ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
+ subhash >>= tbl->nest;
+
+ while (ntbl && size > (1 << shift)) {
+ index = subhash & ((1 << shift) - 1);
+ ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
+ tbl, hash);
+ size >>= shift;
+ subhash >>= shift;
+ }
+
+ if (!ntbl)
+ return NULL;
+
+ return &ntbl[subhash].bucket;
+
+}
+EXPORT_SYMBOL_GPL(__rht_bucket_nested);
+
+struct rhash_lock_head __rcu **rht_bucket_nested(
+ const struct bucket_table *tbl, unsigned int hash)
+{
+ static struct rhash_lock_head __rcu *rhnull;
+
+ if (!rhnull)
+ INIT_RHT_NULLS_HEAD(rhnull);
+ return __rht_bucket_nested(tbl, hash) ?: &rhnull;
+}
+EXPORT_SYMBOL_GPL(rht_bucket_nested);
+
+struct rhash_lock_head __rcu **rht_bucket_nested_insert(
+ struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash)
+{
+ const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
+ unsigned int index = hash & ((1 << tbl->nest) - 1);
+ unsigned int size = tbl->size >> tbl->nest;
+ union nested_table *ntbl;
+
+ ntbl = nested_table_top(tbl);
+ hash >>= tbl->nest;
+ ntbl = nested_table_alloc(ht, &ntbl[index].table,
+ size <= (1 << shift));
+
+ while (ntbl && size > (1 << shift)) {
+ index = hash & ((1 << shift) - 1);
+ size >>= shift;
+ hash >>= shift;
+ ntbl = nested_table_alloc(ht, &ntbl[index].table,
+ size <= (1 << shift));
+ }
+
+ if (!ntbl)
+ return NULL;
+
+ return &ntbl[hash].bucket;
+
+}
+EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);
projects / bcachefs-tools-debian / blobdiff