// SPDX-License-Identifier: GPL-2.0-only
/*
* Resizable, Scalable, Concurrent Hash Table
*
* Copyright (c) 2015 Herbert Xu <[email protected]>
* Copyright (c) 2014-2015 Thomas Graf <[email protected]>
* Copyright (c) 2008-2014 Patrick McHardy <[email protected]>
*
* Code partially derived from nft_hash
* Rewritten with rehash code from br_multicast plus single list
* pointer as suggested by Josh Triplett
*/
#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/log2.h>
#include <linux/sched.h>
#include <linux/rculist.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/jhash.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
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,
const struct rhash_head *he)
{
return rht_head_hashfn(ht, tbl, he, ht->p);
}
#ifdef CONFIG_PROVE_LOCKING
#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
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);
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
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);
}
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);
}
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(const struct bucket_table *tbl)
{
if (tbl->nest)
nested_bucket_table_free(tbl);
kvfree(tbl);
}
static void bucket_table_free_rcu(struct rcu_head *head)
{
bucket_table_free(container_of(head, struct bucket_table, rcu));
}
static union nested_table *nested_table_alloc(struct rhashtable *ht,
union nested_table __rcu **prev,
bool leaf)
{
union nested_table *ntbl;
int i;
ntbl = rcu_dereference(*prev);
if (ntbl)
return ntbl;
ntbl = alloc_hooks_tag(ht->alloc_tag,
kmalloc_noprof(PAGE_SIZE, GFP_ATOMIC|__GFP_ZERO));
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 = alloc_hooks_tag(ht->alloc_tag,
kmalloc_noprof(size, gfp|__GFP_ZERO));
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)
{
struct bucket_table *tbl = NULL;
size_t size;
int i;
static struct lock_class_key __key;
tbl = alloc_hooks_tag(ht->alloc_tag,
kvmalloc_node_noprof(struct_size(tbl, buckets, nbuckets),
gfp|__GFP_ZERO, NUMA_NO_NODE));
size = nbuckets;
if (tbl == NULL && !gfpflags_allow_blocking(gfp)) {
tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
nbuckets = 0;
}
if (tbl == NULL)
return NULL;
lockdep_init_map(&tbl->dep_map, "rhashtable_bucket", &__key, 0);
tbl->size = size;
rcu_head_init(&tbl->rcu);
INIT_LIST_HEAD(&tbl->walkers);
tbl->hash_rnd = get_random_u32();
for (i = 0; i < nbuckets; i++)
INIT_RHT_NULLS_HEAD(tbl->buckets[i]);
return tbl;
}
static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
struct bucket_table *tbl)
{
struct bucket_table *new_tbl;
do {
new_tbl = tbl;
tbl = rht_dereference_rcu(tbl->future_tbl, ht);
} while (tbl);
return new_tbl;
}
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, old_tbl);
int err = -EAGAIN;
struct rhash_head *head, *next, *entry;
struct rhash_head __rcu **pprev = NULL;
unsigned int new_hash;
unsigned long flags;
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);
if (rht_is_a_nulls(next))
break;
pprev = &entry->next;
}
if (err)
goto out;
new_hash = head_hashfn(ht, new_tbl, entry);
flags = rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash],
SINGLE_DEPTH_NESTING);
head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
RCU_INIT_POINTER(entry->next, head);
rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry, flags);
if (pprev)
rcu_assign_pointer(*pprev, next);
else
/* Need to preserved the bit lock. */
rht_assign_locked(bkt, next);
out:
return err;
}
static int rhashtable_rehash_chain(struct rhashtable *ht,
unsigned int old_hash)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
unsigned long flags;
int err;
if (!bkt)
return 0;
flags = rht_lock(old_tbl, bkt);
while (!(err = rhashtable_rehash_one(ht, bkt, old_hash)))
;
if (err == -ENOENT)
err = 0;
rht_unlock(old_tbl, bkt, flags);
return err;
}
static int rhashtable_rehash_attach(struct rhashtable *ht,
struct bucket_table *old_tbl,
struct bucket_table *new_tbl)
{
/* 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().
*/
if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL,
new_tbl) != NULL)
return -EEXIST;
return 0;
}
static int rhashtable_rehash_table(struct rhashtable *ht)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
struct bucket_table *new_tbl;
struct rhashtable_walker *walker;
unsigned int old_hash;
int err;
new_tbl = rht_dereference(old_tbl->future_tbl, ht);
if (!new_tbl)
return 0;
for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
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;
/* 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_rehash_alloc(struct rhashtable *ht,
struct bucket_table *old_tbl,
unsigned int size)
{
struct bucket_table *new_tbl;
int err;
ASSERT_RHT_MUTEX(ht);
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;
}
/**
* 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 *old_tbl = rht_dereference(ht->tbl, ht);
unsigned int nelems = atomic_read(&ht->nelems);
unsigned int size = 0;
if (nelems)
size = roundup_pow_of_two(nelems * 3 / 2);
if (size < ht->p.min_size)
size = ht->p.min_size;
if (old_tbl->size <= size)
return 0;
if (rht_dereference(old_tbl->future_tbl, ht))
return -EEXIST;
return rhashtable_rehash_alloc(ht, old_tbl, size);
}
static void rht_deferred_worker(struct work_struct *work)
{
struct rhashtable *ht;
struct bucket_table *tbl;
int err = 0;
ht = container_of(work, struct rhashtable, run_work);
mutex_lock(&ht->mutex);
tbl = rht_dereference(ht->tbl, ht);
tbl = rhashtable_last_table(ht, tbl);
if (rht_grow_above_75(ht, tbl))
err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
err = rhashtable_shrink(ht);
else if (tbl->nest)
err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
if (!err || err == -EEXIST) {
int nerr;
nerr = rhashtable_rehash_table(ht);
err = err ?: nerr;
}
mutex_unlock(&ht->mutex);
if (err)
schedule_work(&ht->run_work);
}
static int rhashtable_insert_rehash(struct rhashtable *ht,
struct bucket_table *tbl)
{
struct bucket_table *old_tbl;
struct bucket_table *new_tbl;
unsigned int size;
int err;
old_tbl = rht_dereference_rcu(ht->tbl, ht);
size = tbl->size;
err = -EBUSY;
if (rht_grow_above_75(ht, tbl))
size *= 2;
/* Do not schedule more than one rehash */
else if (old_tbl != tbl)
goto fail;
err = -ENOMEM;
new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
if (new_tbl == NULL)
goto fail;
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 err;
fail:
/* Do not fail the insert if someone else did a rehash. */
if (likely(rcu_access_pointer(tbl->future_tbl)))
return 0;
/* Schedule async rehash to retry allocation in process context. */
if (err == -ENOMEM)
schedule_work(&ht->run_work);
return err;
}
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;
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;
}
if (!ht->rhlist)
return rht_obj(ht, head);
list = container_of(obj, struct rhlist_head, rhead);
plist = container_of(head, struct rhlist_head, rhead);
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);
if (unlikely(rht_grow_above_max(ht, tbl)))
return ERR_PTR(-E2BIG);
if (unlikely(rht_grow_above_100(ht, tbl)))
return ERR_PTR(-EAGAIN);
head = rht_ptr(bkt, tbl, hash);
RCU_INIT_POINTER(obj->next, head);
if (ht->rhlist) {
struct rhlist_head *list;
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 long flags;
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 {
flags = 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, flags);
}
} 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);
return data;
}
EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
/**
* 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 occurred. 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;
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
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)
{
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_noprof(struct rhashtable *ht,
const struct rhashtable_params *params)
{
struct bucket_table *tbl;
size_t size;
if ((!params->key_len && !params->obj_hashfn) ||
(params->obj_hashfn && !params->obj_cmpfn))
return -EINVAL;
memset(ht, 0, sizeof(*ht));
mutex_init(&ht->mutex);
spin_lock_init(&ht->lock);
memcpy(&ht->p, params, sizeof(*params));
alloc_tag_record(ht->alloc_tag);
if (params->min_size)
ht->p.min_size = roundup_pow_of_two(params->min_size);
/* Cap total entries at 2^31 to avoid nelems overflow. */
ht->max_elems = 1u << 31;
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;
}
ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
size = rounded_hashtable_size(&ht->p);
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;
}
}
/*
* 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 (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);
RCU_INIT_POINTER(ht->tbl, tbl);
INIT_WORK(&ht->run_work, rht_deferred_worker);
return 0;
}
EXPORT_SYMBOL_GPL(rhashtable_init_noprof);
/**
* 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_noprof(struct rhltable *hlt, const struct rhashtable_params *params)
{
int err;
err = rhashtable_init_noprof(&hlt->ht, params);
hlt->ht.rhlist = true;
return err;
}
EXPORT_SYMBOL_GPL(rhltable_init_noprof);
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);
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