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![Tejun Heo](/assets/img/avatar_default.png)
rhashtable currently only does bh-safe synchronization making it impossible to use from irq-safe contexts. Switch it to use irq-safe synchronization to remove the restriction. v2: Update the lock functions to return the ulong flags value and unlock functions to take the value directly instead of passing around the pointer. Suggested by Linus. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: David Vernet <dvernet@meta.com> Acked-by: Josh Don <joshdon@google.com> Acked-by: Hao Luo <haoluo@google.com> Acked-by: Barret Rhoden <brho@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
1245 lines
30 KiB
C
1245 lines
30 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Resizable, Scalable, Concurrent Hash Table
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*
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* Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
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* Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
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* Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
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*
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* Code partially derived from nft_hash
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* Rewritten with rehash code from br_multicast plus single list
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* pointer as suggested by Josh Triplett
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*/
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#include <linux/atomic.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/log2.h>
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#include <linux/sched.h>
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#include <linux/rculist.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/mm.h>
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#include <linux/jhash.h>
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#include <linux/random.h>
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#include <linux/rhashtable.h>
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#include <linux/err.h>
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#include <linux/export.h>
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#define HASH_DEFAULT_SIZE 64UL
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#define HASH_MIN_SIZE 4U
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union nested_table {
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union nested_table __rcu *table;
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struct rhash_lock_head __rcu *bucket;
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};
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static u32 head_hashfn(struct rhashtable *ht,
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const struct bucket_table *tbl,
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const struct rhash_head *he)
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{
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return rht_head_hashfn(ht, tbl, he, ht->p);
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}
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#ifdef CONFIG_PROVE_LOCKING
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#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
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int lockdep_rht_mutex_is_held(struct rhashtable *ht)
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{
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return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
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}
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EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
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int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
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{
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if (!debug_locks)
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return 1;
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if (unlikely(tbl->nest))
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return 1;
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return bit_spin_is_locked(0, (unsigned long *)&tbl->buckets[hash]);
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}
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EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
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#else
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#define ASSERT_RHT_MUTEX(HT)
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#endif
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static inline union nested_table *nested_table_top(
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const struct bucket_table *tbl)
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{
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/* The top-level bucket entry does not need RCU protection
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* because it's set at the same time as tbl->nest.
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*/
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return (void *)rcu_dereference_protected(tbl->buckets[0], 1);
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}
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static void nested_table_free(union nested_table *ntbl, unsigned int size)
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{
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const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
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const unsigned int len = 1 << shift;
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unsigned int i;
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ntbl = rcu_dereference_protected(ntbl->table, 1);
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if (!ntbl)
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return;
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if (size > len) {
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size >>= shift;
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for (i = 0; i < len; i++)
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nested_table_free(ntbl + i, size);
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}
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kfree(ntbl);
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}
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static void nested_bucket_table_free(const struct bucket_table *tbl)
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{
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unsigned int size = tbl->size >> tbl->nest;
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unsigned int len = 1 << tbl->nest;
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union nested_table *ntbl;
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unsigned int i;
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ntbl = nested_table_top(tbl);
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for (i = 0; i < len; i++)
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nested_table_free(ntbl + i, size);
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kfree(ntbl);
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}
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static void bucket_table_free(const struct bucket_table *tbl)
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{
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if (tbl->nest)
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nested_bucket_table_free(tbl);
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kvfree(tbl);
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}
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static void bucket_table_free_rcu(struct rcu_head *head)
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{
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bucket_table_free(container_of(head, struct bucket_table, rcu));
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}
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static union nested_table *nested_table_alloc(struct rhashtable *ht,
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union nested_table __rcu **prev,
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bool leaf)
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{
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union nested_table *ntbl;
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int i;
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ntbl = rcu_dereference(*prev);
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if (ntbl)
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return ntbl;
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ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
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if (ntbl && leaf) {
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for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++)
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INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
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}
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if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL)
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return ntbl;
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/* Raced with another thread. */
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kfree(ntbl);
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return rcu_dereference(*prev);
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}
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static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
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size_t nbuckets,
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gfp_t gfp)
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{
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const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
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struct bucket_table *tbl;
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size_t size;
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if (nbuckets < (1 << (shift + 1)))
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return NULL;
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size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
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tbl = kzalloc(size, gfp);
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if (!tbl)
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return NULL;
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if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
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false)) {
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kfree(tbl);
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return NULL;
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}
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tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
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return tbl;
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}
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static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
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size_t nbuckets,
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gfp_t gfp)
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{
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struct bucket_table *tbl = NULL;
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size_t size;
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int i;
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static struct lock_class_key __key;
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tbl = kvzalloc(struct_size(tbl, buckets, nbuckets), gfp);
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size = nbuckets;
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if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) {
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tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
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nbuckets = 0;
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}
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if (tbl == NULL)
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return NULL;
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lockdep_init_map(&tbl->dep_map, "rhashtable_bucket", &__key, 0);
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tbl->size = size;
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rcu_head_init(&tbl->rcu);
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INIT_LIST_HEAD(&tbl->walkers);
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tbl->hash_rnd = get_random_u32();
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for (i = 0; i < nbuckets; i++)
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INIT_RHT_NULLS_HEAD(tbl->buckets[i]);
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return tbl;
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}
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static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
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struct bucket_table *tbl)
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{
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struct bucket_table *new_tbl;
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do {
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new_tbl = tbl;
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tbl = rht_dereference_rcu(tbl->future_tbl, ht);
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} while (tbl);
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return new_tbl;
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}
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static int rhashtable_rehash_one(struct rhashtable *ht,
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struct rhash_lock_head __rcu **bkt,
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unsigned int old_hash)
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{
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struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
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struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl);
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int err = -EAGAIN;
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struct rhash_head *head, *next, *entry;
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struct rhash_head __rcu **pprev = NULL;
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unsigned int new_hash;
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unsigned long flags;
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if (new_tbl->nest)
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goto out;
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err = -ENOENT;
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rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash),
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old_tbl, old_hash) {
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err = 0;
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next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
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if (rht_is_a_nulls(next))
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break;
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pprev = &entry->next;
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}
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if (err)
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goto out;
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new_hash = head_hashfn(ht, new_tbl, entry);
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flags = rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash],
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SINGLE_DEPTH_NESTING);
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head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
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RCU_INIT_POINTER(entry->next, head);
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rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry, flags);
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if (pprev)
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rcu_assign_pointer(*pprev, next);
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else
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/* Need to preserved the bit lock. */
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rht_assign_locked(bkt, next);
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out:
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return err;
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}
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static int rhashtable_rehash_chain(struct rhashtable *ht,
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unsigned int old_hash)
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{
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struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
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struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
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unsigned long flags;
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int err;
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if (!bkt)
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return 0;
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flags = rht_lock(old_tbl, bkt);
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while (!(err = rhashtable_rehash_one(ht, bkt, old_hash)))
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;
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if (err == -ENOENT)
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err = 0;
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rht_unlock(old_tbl, bkt, flags);
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return err;
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}
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static int rhashtable_rehash_attach(struct rhashtable *ht,
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struct bucket_table *old_tbl,
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struct bucket_table *new_tbl)
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{
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/* Make insertions go into the new, empty table right away. Deletions
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* and lookups will be attempted in both tables until we synchronize.
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* As cmpxchg() provides strong barriers, we do not need
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* rcu_assign_pointer().
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*/
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if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL,
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new_tbl) != NULL)
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return -EEXIST;
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return 0;
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}
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static int rhashtable_rehash_table(struct rhashtable *ht)
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{
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struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
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struct bucket_table *new_tbl;
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struct rhashtable_walker *walker;
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unsigned int old_hash;
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int err;
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new_tbl = rht_dereference(old_tbl->future_tbl, ht);
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if (!new_tbl)
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return 0;
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for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
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err = rhashtable_rehash_chain(ht, old_hash);
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if (err)
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return err;
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cond_resched();
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}
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/* Publish the new table pointer. */
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rcu_assign_pointer(ht->tbl, new_tbl);
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spin_lock(&ht->lock);
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list_for_each_entry(walker, &old_tbl->walkers, list)
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walker->tbl = NULL;
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/* Wait for readers. All new readers will see the new
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* table, and thus no references to the old table will
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* remain.
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* We do this inside the locked region so that
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* rhashtable_walk_stop() can use rcu_head_after_call_rcu()
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* to check if it should not re-link the table.
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*/
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call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
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spin_unlock(&ht->lock);
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return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
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}
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static int rhashtable_rehash_alloc(struct rhashtable *ht,
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struct bucket_table *old_tbl,
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unsigned int size)
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{
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struct bucket_table *new_tbl;
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int err;
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ASSERT_RHT_MUTEX(ht);
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new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
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if (new_tbl == NULL)
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return -ENOMEM;
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err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
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if (err)
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bucket_table_free(new_tbl);
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return err;
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}
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/**
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* rhashtable_shrink - Shrink hash table while allowing concurrent lookups
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* @ht: the hash table to shrink
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*
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* This function shrinks the hash table to fit, i.e., the smallest
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* size would not cause it to expand right away automatically.
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*
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* The caller must ensure that no concurrent resizing occurs by holding
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* ht->mutex.
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*
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* The caller must ensure that no concurrent table mutations take place.
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* It is however valid to have concurrent lookups if they are RCU protected.
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*
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* It is valid to have concurrent insertions and deletions protected by per
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* bucket locks or concurrent RCU protected lookups and traversals.
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*/
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static int rhashtable_shrink(struct rhashtable *ht)
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{
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struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
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unsigned int nelems = atomic_read(&ht->nelems);
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unsigned int size = 0;
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if (nelems)
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size = roundup_pow_of_two(nelems * 3 / 2);
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if (size < ht->p.min_size)
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size = ht->p.min_size;
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if (old_tbl->size <= size)
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return 0;
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if (rht_dereference(old_tbl->future_tbl, ht))
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return -EEXIST;
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return rhashtable_rehash_alloc(ht, old_tbl, size);
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}
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static void rht_deferred_worker(struct work_struct *work)
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{
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struct rhashtable *ht;
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struct bucket_table *tbl;
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int err = 0;
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ht = container_of(work, struct rhashtable, run_work);
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mutex_lock(&ht->mutex);
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tbl = rht_dereference(ht->tbl, ht);
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tbl = rhashtable_last_table(ht, tbl);
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if (rht_grow_above_75(ht, tbl))
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err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
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else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
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err = rhashtable_shrink(ht);
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else if (tbl->nest)
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err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
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if (!err || err == -EEXIST) {
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int nerr;
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nerr = rhashtable_rehash_table(ht);
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err = err ?: nerr;
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}
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mutex_unlock(&ht->mutex);
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if (err)
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schedule_work(&ht->run_work);
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}
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static int rhashtable_insert_rehash(struct rhashtable *ht,
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struct bucket_table *tbl)
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{
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struct bucket_table *old_tbl;
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struct bucket_table *new_tbl;
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unsigned int size;
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int err;
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old_tbl = rht_dereference_rcu(ht->tbl, ht);
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size = tbl->size;
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err = -EBUSY;
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if (rht_grow_above_75(ht, tbl))
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size *= 2;
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/* Do not schedule more than one rehash */
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else if (old_tbl != tbl)
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goto fail;
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err = -ENOMEM;
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new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
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if (new_tbl == NULL)
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goto fail;
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err = rhashtable_rehash_attach(ht, tbl, new_tbl);
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if (err) {
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bucket_table_free(new_tbl);
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if (err == -EEXIST)
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err = 0;
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} else
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schedule_work(&ht->run_work);
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return err;
|
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|
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fail:
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/* Do not fail the insert if someone else did a rehash. */
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if (likely(rcu_access_pointer(tbl->future_tbl)))
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return 0;
|
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|
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/* Schedule async rehash to retry allocation in process context. */
|
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if (err == -ENOMEM)
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schedule_work(&ht->run_work);
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|
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return err;
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}
|
|
|
|
static void *rhashtable_lookup_one(struct rhashtable *ht,
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struct rhash_lock_head __rcu **bkt,
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struct bucket_table *tbl, unsigned int hash,
|
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const void *key, struct rhash_head *obj)
|
|
{
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struct rhashtable_compare_arg arg = {
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.ht = ht,
|
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.key = key,
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};
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struct rhash_head __rcu **pprev = NULL;
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struct rhash_head *head;
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int elasticity;
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|
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elasticity = RHT_ELASTICITY;
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rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {
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struct rhlist_head *list;
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struct rhlist_head *plist;
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|
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elasticity--;
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if (!key ||
|
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(ht->p.obj_cmpfn ?
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ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
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rhashtable_compare(&arg, rht_obj(ht, head)))) {
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pprev = &head->next;
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continue;
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}
|
|
|
|
if (!ht->rhlist)
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return rht_obj(ht, head);
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|
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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(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));
|
|
|
|
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);
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
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);
|