![Eric Dumazet](/assets/img/avatar_default.png)
If a hash table has 128 slots and 16384 elems, expand to 256 slots takes more than one second. For larger sets, a soft lockup is detected. Holding cpu for that long, even in a work queue is a show stopper for non preemptable kernels. cond_resched() at strategic points to allow process scheduler to reschedule us. Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
1135 lines
30 KiB
C
1135 lines
30 KiB
C
/*
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* Resizable, Scalable, Concurrent Hash Table
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*
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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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* Based on the following paper:
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* https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
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*
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* Code partially derived from nft_hash
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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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/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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#define HASH_DEFAULT_SIZE 64UL
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#define HASH_MIN_SIZE 4UL
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#define BUCKET_LOCKS_PER_CPU 128UL
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/* Base bits plus 1 bit for nulls marker */
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#define HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
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enum {
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RHT_LOCK_NORMAL,
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RHT_LOCK_NESTED,
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};
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/* The bucket lock is selected based on the hash and protects mutations
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* on a group of hash buckets.
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*
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* A maximum of tbl->size/2 bucket locks is allocated. This ensures that
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* a single lock always covers both buckets which may both contains
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* entries which link to the same bucket of the old table during resizing.
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* This allows to simplify the locking as locking the bucket in both
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* tables during resize always guarantee protection.
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*
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* IMPORTANT: When holding the bucket lock of both the old and new table
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* during expansions and shrinking, the old bucket lock must always be
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* acquired first.
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*/
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static spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash)
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{
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return &tbl->locks[hash & tbl->locks_mask];
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}
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static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he)
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{
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return (void *) he - ht->p.head_offset;
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}
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static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash)
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{
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return hash & (tbl->size - 1);
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}
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static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr)
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{
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u32 hash;
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if (unlikely(!ht->p.key_len))
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hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd);
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else
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hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len,
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ht->p.hash_rnd);
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return hash >> HASH_RESERVED_SPACE;
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}
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static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len)
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{
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return ht->p.hashfn(key, len, ht->p.hash_rnd) >> HASH_RESERVED_SPACE;
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}
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static u32 head_hashfn(const 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_bucket_index(tbl, obj_raw_hashfn(ht, rht_obj(ht, he)));
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}
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#ifdef CONFIG_PROVE_LOCKING
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static void debug_dump_buckets(const struct rhashtable *ht,
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const struct bucket_table *tbl)
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{
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struct rhash_head *he;
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unsigned int i, hash;
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for (i = 0; i < tbl->size; i++) {
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pr_warn(" [Bucket %d] ", i);
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rht_for_each_rcu(he, tbl, i) {
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hash = head_hashfn(ht, tbl, he);
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pr_cont("[hash = %#x, lock = %p] ",
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hash, bucket_lock(tbl, hash));
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}
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pr_cont("\n");
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}
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}
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static void debug_dump_table(struct rhashtable *ht,
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const struct bucket_table *tbl,
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unsigned int hash)
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{
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struct bucket_table *old_tbl, *future_tbl;
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pr_emerg("BUG: lock for hash %#x in table %p not held\n",
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hash, tbl);
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rcu_read_lock();
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future_tbl = rht_dereference_rcu(ht->future_tbl, ht);
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old_tbl = rht_dereference_rcu(ht->tbl, ht);
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if (future_tbl != old_tbl) {
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pr_warn("Future table %p (size: %zd)\n",
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future_tbl, future_tbl->size);
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debug_dump_buckets(ht, future_tbl);
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}
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pr_warn("Table %p (size: %zd)\n", old_tbl, old_tbl->size);
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debug_dump_buckets(ht, old_tbl);
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rcu_read_unlock();
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}
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#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
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#define ASSERT_BUCKET_LOCK(HT, TBL, HASH) \
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do { \
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if (unlikely(!lockdep_rht_bucket_is_held(TBL, HASH))) { \
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debug_dump_table(HT, TBL, HASH); \
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BUG(); \
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} \
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} while (0)
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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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spinlock_t *lock = bucket_lock(tbl, hash);
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return (debug_locks) ? lockdep_is_held(lock) : 1;
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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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#define ASSERT_BUCKET_LOCK(HT, TBL, HASH)
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#endif
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static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n)
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{
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struct rhash_head __rcu **pprev;
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for (pprev = &tbl->buckets[n];
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!rht_is_a_nulls(rht_dereference_bucket(*pprev, tbl, n));
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pprev = &rht_dereference_bucket(*pprev, tbl, n)->next)
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;
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return pprev;
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}
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static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl)
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{
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unsigned int i, size;
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#if defined(CONFIG_PROVE_LOCKING)
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unsigned int nr_pcpus = 2;
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#else
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unsigned int nr_pcpus = num_possible_cpus();
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#endif
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nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL);
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size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
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/* Never allocate more than 0.5 locks per bucket */
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size = min_t(unsigned int, size, tbl->size >> 1);
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if (sizeof(spinlock_t) != 0) {
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#ifdef CONFIG_NUMA
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if (size * sizeof(spinlock_t) > PAGE_SIZE)
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tbl->locks = vmalloc(size * sizeof(spinlock_t));
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else
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#endif
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tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
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GFP_KERNEL);
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if (!tbl->locks)
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return -ENOMEM;
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for (i = 0; i < size; i++)
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spin_lock_init(&tbl->locks[i]);
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}
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tbl->locks_mask = size - 1;
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return 0;
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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)
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kvfree(tbl->locks);
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kvfree(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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{
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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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size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
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if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
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tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY);
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if (tbl == NULL)
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tbl = vzalloc(size);
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if (tbl == NULL)
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return NULL;
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tbl->size = nbuckets;
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if (alloc_bucket_locks(ht, tbl) < 0) {
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bucket_table_free(tbl);
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return NULL;
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}
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for (i = 0; i < nbuckets; i++)
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INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
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return tbl;
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}
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/**
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* rht_grow_above_75 - returns true if nelems > 0.75 * table-size
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* @ht: hash table
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* @new_size: new table size
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*/
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static bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
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{
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/* Expand table when exceeding 75% load */
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return atomic_read(&ht->nelems) > (new_size / 4 * 3) &&
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(!ht->p.max_shift || atomic_read(&ht->shift) < ht->p.max_shift);
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}
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/**
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* rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
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* @ht: hash table
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* @new_size: new table size
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*/
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static bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
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{
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/* Shrink table beneath 30% load */
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return atomic_read(&ht->nelems) < (new_size * 3 / 10) &&
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(atomic_read(&ht->shift) > ht->p.min_shift);
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}
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static void lock_buckets(struct bucket_table *new_tbl,
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struct bucket_table *old_tbl, unsigned int hash)
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__acquires(old_bucket_lock)
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{
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spin_lock_bh(bucket_lock(old_tbl, hash));
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if (new_tbl != old_tbl)
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spin_lock_bh_nested(bucket_lock(new_tbl, hash),
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RHT_LOCK_NESTED);
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}
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static void unlock_buckets(struct bucket_table *new_tbl,
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struct bucket_table *old_tbl, unsigned int hash)
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__releases(old_bucket_lock)
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{
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if (new_tbl != old_tbl)
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spin_unlock_bh(bucket_lock(new_tbl, hash));
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spin_unlock_bh(bucket_lock(old_tbl, hash));
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}
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/**
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* Unlink entries on bucket which hash to different bucket.
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*
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* Returns true if no more work needs to be performed on the bucket.
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*/
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static bool hashtable_chain_unzip(struct rhashtable *ht,
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const struct bucket_table *new_tbl,
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struct bucket_table *old_tbl,
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size_t old_hash)
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{
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struct rhash_head *he, *p, *next;
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unsigned int new_hash, new_hash2;
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ASSERT_BUCKET_LOCK(ht, old_tbl, old_hash);
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/* Old bucket empty, no work needed. */
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p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl,
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old_hash);
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if (rht_is_a_nulls(p))
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return false;
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new_hash = head_hashfn(ht, new_tbl, p);
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ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash);
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/* Advance the old bucket pointer one or more times until it
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* reaches a node that doesn't hash to the same bucket as the
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* previous node p. Call the previous node p;
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*/
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rht_for_each_continue(he, p->next, old_tbl, old_hash) {
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new_hash2 = head_hashfn(ht, new_tbl, he);
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ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash2);
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if (new_hash != new_hash2)
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break;
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p = he;
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}
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rcu_assign_pointer(old_tbl->buckets[old_hash], p->next);
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/* Find the subsequent node which does hash to the same
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* bucket as node P, or NULL if no such node exists.
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*/
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INIT_RHT_NULLS_HEAD(next, ht, old_hash);
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if (!rht_is_a_nulls(he)) {
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rht_for_each_continue(he, he->next, old_tbl, old_hash) {
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if (head_hashfn(ht, new_tbl, he) == new_hash) {
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next = he;
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break;
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}
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}
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}
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/* Set p's next pointer to that subsequent node pointer,
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* bypassing the nodes which do not hash to p's bucket
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*/
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rcu_assign_pointer(p->next, next);
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p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl,
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old_hash);
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return !rht_is_a_nulls(p);
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}
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static void link_old_to_new(struct rhashtable *ht, struct bucket_table *new_tbl,
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unsigned int new_hash, struct rhash_head *entry)
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{
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ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash);
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rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry);
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}
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/**
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* rhashtable_expand - Expand hash table while allowing concurrent lookups
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* @ht: the hash table to expand
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*
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* A secondary bucket array is allocated and the hash entries are migrated
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* while keeping them on both lists until the end of the RCU grace period.
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*
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* This function may only be called in a context where it is safe to call
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* synchronize_rcu(), e.g. not within a rcu_read_lock() section.
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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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* 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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int rhashtable_expand(struct rhashtable *ht)
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{
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struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
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struct rhash_head *he;
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unsigned int new_hash, old_hash;
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bool complete = false;
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ASSERT_RHT_MUTEX(ht);
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new_tbl = bucket_table_alloc(ht, old_tbl->size * 2);
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if (new_tbl == NULL)
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return -ENOMEM;
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atomic_inc(&ht->shift);
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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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* The synchronize_rcu() guarantees for the new table to be picked up
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* so no new additions go into the old table while we relink.
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*/
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rcu_assign_pointer(ht->future_tbl, new_tbl);
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synchronize_rcu();
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/* For each new bucket, search the corresponding old bucket for the
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* first entry that hashes to the new bucket, and link the end of
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* newly formed bucket chain (containing entries added to future
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* table) to that entry. Since all the entries which will end up in
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* the new bucket appear in the same old bucket, this constructs an
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* entirely valid new hash table, but with multiple buckets
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* "zipped" together into a single imprecise chain.
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*/
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for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
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old_hash = rht_bucket_index(old_tbl, new_hash);
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lock_buckets(new_tbl, old_tbl, new_hash);
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rht_for_each(he, old_tbl, old_hash) {
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if (head_hashfn(ht, new_tbl, he) == new_hash) {
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link_old_to_new(ht, new_tbl, new_hash, he);
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break;
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}
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}
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unlock_buckets(new_tbl, old_tbl, new_hash);
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cond_resched();
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}
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/* Unzip interleaved hash chains */
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while (!complete && !ht->being_destroyed) {
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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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*/
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synchronize_rcu();
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/* For each bucket in the old table (each of which
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* contains items from multiple buckets of the new
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* table): ...
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*/
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complete = true;
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for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
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lock_buckets(new_tbl, old_tbl, old_hash);
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if (hashtable_chain_unzip(ht, new_tbl, old_tbl,
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old_hash))
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complete = false;
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unlock_buckets(new_tbl, old_tbl, old_hash);
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cond_resched();
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}
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}
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rcu_assign_pointer(ht->tbl, new_tbl);
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synchronize_rcu();
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bucket_table_free(old_tbl);
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return 0;
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}
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EXPORT_SYMBOL_GPL(rhashtable_expand);
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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 may only be called in a context where it is safe to call
|
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* synchronize_rcu(), e.g. not within a rcu_read_lock() section.
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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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int rhashtable_shrink(struct rhashtable *ht)
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{
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struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht);
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unsigned int new_hash;
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ASSERT_RHT_MUTEX(ht);
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new_tbl = bucket_table_alloc(ht, tbl->size / 2);
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if (new_tbl == NULL)
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return -ENOMEM;
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rcu_assign_pointer(ht->future_tbl, new_tbl);
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synchronize_rcu();
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/* Link the first entry in the old bucket to the end of the
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* bucket in the new table. As entries are concurrently being
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* added to the new table, lock down the new bucket. As we
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* always divide the size in half when shrinking, each bucket
|
|
* in the new table maps to exactly two buckets in the old
|
|
* table.
|
|
*/
|
|
for (new_hash = 0; new_hash < new_tbl->size; new_hash++) {
|
|
lock_buckets(new_tbl, tbl, new_hash);
|
|
|
|
rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
|
|
tbl->buckets[new_hash]);
|
|
ASSERT_BUCKET_LOCK(ht, tbl, new_hash + new_tbl->size);
|
|
rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
|
|
tbl->buckets[new_hash + new_tbl->size]);
|
|
|
|
unlock_buckets(new_tbl, tbl, new_hash);
|
|
cond_resched();
|
|
}
|
|
|
|
/* Publish the new, valid hash table */
|
|
rcu_assign_pointer(ht->tbl, new_tbl);
|
|
atomic_dec(&ht->shift);
|
|
|
|
/* Wait for readers. No new readers will have references to the
|
|
* old hash table.
|
|
*/
|
|
synchronize_rcu();
|
|
|
|
bucket_table_free(tbl);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_shrink);
|
|
|
|
static void rht_deferred_worker(struct work_struct *work)
|
|
{
|
|
struct rhashtable *ht;
|
|
struct bucket_table *tbl;
|
|
struct rhashtable_walker *walker;
|
|
|
|
ht = container_of(work, struct rhashtable, run_work);
|
|
mutex_lock(&ht->mutex);
|
|
if (ht->being_destroyed)
|
|
goto unlock;
|
|
|
|
tbl = rht_dereference(ht->tbl, ht);
|
|
|
|
list_for_each_entry(walker, &ht->walkers, list)
|
|
walker->resize = true;
|
|
|
|
if (rht_grow_above_75(ht, tbl->size))
|
|
rhashtable_expand(ht);
|
|
else if (rht_shrink_below_30(ht, tbl->size))
|
|
rhashtable_shrink(ht);
|
|
unlock:
|
|
mutex_unlock(&ht->mutex);
|
|
}
|
|
|
|
static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
|
|
struct bucket_table *tbl,
|
|
const struct bucket_table *old_tbl, u32 hash)
|
|
{
|
|
bool no_resize_running = tbl == old_tbl;
|
|
struct rhash_head *head;
|
|
|
|
hash = rht_bucket_index(tbl, hash);
|
|
head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
|
|
|
|
ASSERT_BUCKET_LOCK(ht, tbl, hash);
|
|
|
|
if (rht_is_a_nulls(head))
|
|
INIT_RHT_NULLS_HEAD(obj->next, ht, hash);
|
|
else
|
|
RCU_INIT_POINTER(obj->next, head);
|
|
|
|
rcu_assign_pointer(tbl->buckets[hash], obj);
|
|
|
|
atomic_inc(&ht->nelems);
|
|
if (no_resize_running && rht_grow_above_75(ht, tbl->size))
|
|
schedule_work(&ht->run_work);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_insert - insert object into hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
*
|
|
* Will take a per bucket spinlock to protect against mutual mutations
|
|
* on the same bucket. Multiple insertions may occur in parallel unless
|
|
* they map to the same bucket lock.
|
|
*
|
|
* It is safe to call this function from atomic context.
|
|
*
|
|
* Will trigger an automatic deferred table resizing if the size grows
|
|
* beyond the watermark indicated by grow_decision() which can be passed
|
|
* to rhashtable_init().
|
|
*/
|
|
void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
|
|
{
|
|
struct bucket_table *tbl, *old_tbl;
|
|
unsigned hash;
|
|
|
|
rcu_read_lock();
|
|
|
|
tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
old_tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
|
|
|
|
lock_buckets(tbl, old_tbl, hash);
|
|
__rhashtable_insert(ht, obj, tbl, old_tbl, hash);
|
|
unlock_buckets(tbl, old_tbl, hash);
|
|
|
|
rcu_read_unlock();
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_insert);
|
|
|
|
/**
|
|
* rhashtable_remove - remove object from hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
*
|
|
* Since the hash chain is single linked, the removal operation needs to
|
|
* walk the bucket chain upon removal. The removal operation is thus
|
|
* considerable slow if the hash table is not correctly sized.
|
|
*
|
|
* Will automatically shrink the table via rhashtable_expand() if the
|
|
* shrink_decision function specified at rhashtable_init() returns true.
|
|
*
|
|
* The caller must ensure that no concurrent table mutations occur. It is
|
|
* however valid to have concurrent lookups if they are RCU protected.
|
|
*/
|
|
bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
|
|
{
|
|
struct bucket_table *tbl, *new_tbl, *old_tbl;
|
|
struct rhash_head __rcu **pprev;
|
|
struct rhash_head *he, *he2;
|
|
unsigned int hash, new_hash;
|
|
bool ret = false;
|
|
|
|
rcu_read_lock();
|
|
old_tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
tbl = new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
new_hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
|
|
|
|
lock_buckets(new_tbl, old_tbl, new_hash);
|
|
restart:
|
|
hash = rht_bucket_index(tbl, new_hash);
|
|
pprev = &tbl->buckets[hash];
|
|
rht_for_each(he, tbl, hash) {
|
|
if (he != obj) {
|
|
pprev = &he->next;
|
|
continue;
|
|
}
|
|
|
|
ASSERT_BUCKET_LOCK(ht, tbl, hash);
|
|
|
|
if (old_tbl->size > new_tbl->size && tbl == old_tbl &&
|
|
!rht_is_a_nulls(obj->next) &&
|
|
head_hashfn(ht, tbl, obj->next) != hash) {
|
|
rcu_assign_pointer(*pprev, (struct rhash_head *) rht_marker(ht, hash));
|
|
} else if (unlikely(old_tbl->size < new_tbl->size && tbl == new_tbl)) {
|
|
rht_for_each_continue(he2, obj->next, tbl, hash) {
|
|
if (head_hashfn(ht, tbl, he2) == hash) {
|
|
rcu_assign_pointer(*pprev, he2);
|
|
goto found;
|
|
}
|
|
}
|
|
|
|
rcu_assign_pointer(*pprev, (struct rhash_head *) rht_marker(ht, hash));
|
|
} else {
|
|
rcu_assign_pointer(*pprev, obj->next);
|
|
}
|
|
|
|
found:
|
|
ret = true;
|
|
break;
|
|
}
|
|
|
|
/* The entry may be linked in either 'tbl', 'future_tbl', or both.
|
|
* 'future_tbl' only exists for a short period of time during
|
|
* resizing. Thus traversing both is fine and the added cost is
|
|
* very rare.
|
|
*/
|
|
if (tbl != old_tbl) {
|
|
tbl = old_tbl;
|
|
goto restart;
|
|
}
|
|
|
|
unlock_buckets(new_tbl, old_tbl, new_hash);
|
|
|
|
if (ret) {
|
|
bool no_resize_running = new_tbl == old_tbl;
|
|
|
|
atomic_dec(&ht->nelems);
|
|
if (no_resize_running && rht_shrink_below_30(ht, new_tbl->size))
|
|
schedule_work(&ht->run_work);
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_remove);
|
|
|
|
struct rhashtable_compare_arg {
|
|
struct rhashtable *ht;
|
|
const void *key;
|
|
};
|
|
|
|
static bool rhashtable_compare(void *ptr, void *arg)
|
|
{
|
|
struct rhashtable_compare_arg *x = arg;
|
|
struct rhashtable *ht = x->ht;
|
|
|
|
return !memcmp(ptr + ht->p.key_offset, x->key, ht->p.key_len);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_lookup - lookup key in hash table
|
|
* @ht: hash table
|
|
* @key: pointer to key
|
|
*
|
|
* Computes the hash value for the key and traverses the bucket chain looking
|
|
* for a entry with an identical key. The first matching entry is returned.
|
|
*
|
|
* This lookup function may only be used for fixed key hash table (key_len
|
|
* parameter set). It will BUG() if used inappropriately.
|
|
*
|
|
* Lookups may occur in parallel with hashtable mutations and resizing.
|
|
*/
|
|
void *rhashtable_lookup(struct rhashtable *ht, const void *key)
|
|
{
|
|
struct rhashtable_compare_arg arg = {
|
|
.ht = ht,
|
|
.key = key,
|
|
};
|
|
|
|
BUG_ON(!ht->p.key_len);
|
|
|
|
return rhashtable_lookup_compare(ht, key, &rhashtable_compare, &arg);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_lookup);
|
|
|
|
/**
|
|
* rhashtable_lookup_compare - search hash table with compare function
|
|
* @ht: hash table
|
|
* @key: the pointer to the key
|
|
* @compare: compare function, must return true on match
|
|
* @arg: argument passed on to compare function
|
|
*
|
|
* Traverses the bucket chain behind the provided hash value and calls the
|
|
* specified compare function for each entry.
|
|
*
|
|
* Lookups may occur in parallel with hashtable mutations and resizing.
|
|
*
|
|
* Returns the first entry on which the compare function returned true.
|
|
*/
|
|
void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
|
|
bool (*compare)(void *, void *), void *arg)
|
|
{
|
|
const struct bucket_table *tbl, *old_tbl;
|
|
struct rhash_head *he;
|
|
u32 hash;
|
|
|
|
rcu_read_lock();
|
|
|
|
old_tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
hash = key_hashfn(ht, key, ht->p.key_len);
|
|
restart:
|
|
rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) {
|
|
if (!compare(rht_obj(ht, he), arg))
|
|
continue;
|
|
rcu_read_unlock();
|
|
return rht_obj(ht, he);
|
|
}
|
|
|
|
if (unlikely(tbl != old_tbl)) {
|
|
tbl = old_tbl;
|
|
goto restart;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
|
|
|
|
/**
|
|
* rhashtable_lookup_insert - lookup and insert object into hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
*
|
|
* Locks down the bucket chain in both the old and new table if a resize
|
|
* is in progress to ensure that writers can't remove from the old table
|
|
* and can't insert to the new table during the atomic operation of search
|
|
* and insertion. Searches for duplicates in both the old and new table if
|
|
* a resize is in progress.
|
|
*
|
|
* This lookup function may only be used for fixed key hash table (key_len
|
|
* parameter set). It will BUG() if used inappropriately.
|
|
*
|
|
* It is safe to call this function from atomic context.
|
|
*
|
|
* Will trigger an automatic deferred table resizing if the size grows
|
|
* beyond the watermark indicated by grow_decision() which can be passed
|
|
* to rhashtable_init().
|
|
*/
|
|
bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
|
|
{
|
|
struct rhashtable_compare_arg arg = {
|
|
.ht = ht,
|
|
.key = rht_obj(ht, obj) + ht->p.key_offset,
|
|
};
|
|
|
|
BUG_ON(!ht->p.key_len);
|
|
|
|
return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare,
|
|
&arg);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
|
|
|
|
/**
|
|
* rhashtable_lookup_compare_insert - search and insert object to hash table
|
|
* with compare function
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
* @compare: compare function, must return true on match
|
|
* @arg: argument passed on to compare function
|
|
*
|
|
* Locks down the bucket chain in both the old and new table if a resize
|
|
* is in progress to ensure that writers can't remove from the old table
|
|
* and can't insert to the new table during the atomic operation of search
|
|
* and insertion. Searches for duplicates in both the old and new table if
|
|
* a resize is in progress.
|
|
*
|
|
* Lookups may occur in parallel with hashtable mutations and resizing.
|
|
*
|
|
* Will trigger an automatic deferred table resizing if the size grows
|
|
* beyond the watermark indicated by grow_decision() which can be passed
|
|
* to rhashtable_init().
|
|
*/
|
|
bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
|
|
struct rhash_head *obj,
|
|
bool (*compare)(void *, void *),
|
|
void *arg)
|
|
{
|
|
struct bucket_table *new_tbl, *old_tbl;
|
|
u32 new_hash;
|
|
bool success = true;
|
|
|
|
BUG_ON(!ht->p.key_len);
|
|
|
|
rcu_read_lock();
|
|
old_tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
|
|
new_hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
|
|
|
|
lock_buckets(new_tbl, old_tbl, new_hash);
|
|
|
|
if (rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset,
|
|
compare, arg)) {
|
|
success = false;
|
|
goto exit;
|
|
}
|
|
|
|
__rhashtable_insert(ht, obj, new_tbl, old_tbl, new_hash);
|
|
|
|
exit:
|
|
unlock_buckets(new_tbl, old_tbl, new_hash);
|
|
rcu_read_unlock();
|
|
|
|
return success;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert);
|
|
|
|
/**
|
|
* rhashtable_walk_init - 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 sleep so you must not call it from interrupt
|
|
* context or with spin locks held.
|
|
*
|
|
* You must call rhashtable_walk_exit if this function returns
|
|
* successfully.
|
|
*/
|
|
int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
|
|
{
|
|
iter->ht = ht;
|
|
iter->p = NULL;
|
|
iter->slot = 0;
|
|
iter->skip = 0;
|
|
|
|
iter->walker = kmalloc(sizeof(*iter->walker), GFP_KERNEL);
|
|
if (!iter->walker)
|
|
return -ENOMEM;
|
|
|
|
INIT_LIST_HEAD(&iter->walker->list);
|
|
iter->walker->resize = false;
|
|
|
|
mutex_lock(&ht->mutex);
|
|
list_add(&iter->walker->list, &ht->walkers);
|
|
mutex_unlock(&ht->mutex);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_walk_init);
|
|
|
|
/**
|
|
* rhashtable_walk_exit - Free an iterator
|
|
* @iter: Hash table Iterator
|
|
*
|
|
* This function frees resources allocated by rhashtable_walk_init.
|
|
*/
|
|
void rhashtable_walk_exit(struct rhashtable_iter *iter)
|
|
{
|
|
mutex_lock(&iter->ht->mutex);
|
|
list_del(&iter->walker->list);
|
|
mutex_unlock(&iter->ht->mutex);
|
|
kfree(iter->walker);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
|
|
|
|
/**
|
|
* rhashtable_walk_start - Start a hash table walk
|
|
* @iter: Hash table iterator
|
|
*
|
|
* Start a hash table walk. 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.
|
|
*/
|
|
int rhashtable_walk_start(struct rhashtable_iter *iter)
|
|
{
|
|
rcu_read_lock();
|
|
|
|
if (iter->walker->resize) {
|
|
iter->slot = 0;
|
|
iter->skip = 0;
|
|
iter->walker->resize = false;
|
|
return -EAGAIN;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_walk_start);
|
|
|
|
/**
|
|
* 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 occured. 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)
|
|
{
|
|
const struct bucket_table *tbl;
|
|
struct rhashtable *ht = iter->ht;
|
|
struct rhash_head *p = iter->p;
|
|
void *obj = NULL;
|
|
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
|
|
if (p) {
|
|
p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);
|
|
goto next;
|
|
}
|
|
|
|
for (; iter->slot < tbl->size; iter->slot++) {
|
|
int skip = iter->skip;
|
|
|
|
rht_for_each_rcu(p, tbl, iter->slot) {
|
|
if (!skip)
|
|
break;
|
|
skip--;
|
|
}
|
|
|
|
next:
|
|
if (!rht_is_a_nulls(p)) {
|
|
iter->skip++;
|
|
iter->p = p;
|
|
obj = rht_obj(ht, p);
|
|
goto out;
|
|
}
|
|
|
|
iter->skip = 0;
|
|
}
|
|
|
|
iter->p = NULL;
|
|
|
|
out:
|
|
if (iter->walker->resize) {
|
|
iter->p = NULL;
|
|
iter->slot = 0;
|
|
iter->skip = 0;
|
|
iter->walker->resize = false;
|
|
return ERR_PTR(-EAGAIN);
|
|
}
|
|
|
|
return obj;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_walk_next);
|
|
|
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/**
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|
* rhashtable_walk_stop - Finish a hash table walk
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|
* @iter: Hash table iterator
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|
*
|
|
* Finish a hash table walk.
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|
*/
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|
void rhashtable_walk_stop(struct rhashtable_iter *iter)
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|
{
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|
rcu_read_unlock();
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|
iter->p = NULL;
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|
}
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|
EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
|
|
|
|
static size_t rounded_hashtable_size(struct rhashtable_params *params)
|
|
{
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|
return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
|
|
1UL << params->min_shift);
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|
}
|
|
|
|
/**
|
|
* 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,
|
|
* .nulls_base = (1U << RHT_BASE_SHIFT),
|
|
* };
|
|
*
|
|
* Configuration Example 2: Variable length keys
|
|
* struct test_obj {
|
|
* [...]
|
|
* struct rhash_head node;
|
|
* };
|
|
*
|
|
* u32 my_hash_fn(const void *data, 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, struct rhashtable_params *params)
|
|
{
|
|
struct bucket_table *tbl;
|
|
size_t size;
|
|
|
|
size = HASH_DEFAULT_SIZE;
|
|
|
|
if ((params->key_len && !params->hashfn) ||
|
|
(!params->key_len && !params->obj_hashfn))
|
|
return -EINVAL;
|
|
|
|
if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
|
|
return -EINVAL;
|
|
|
|
params->min_shift = max_t(size_t, params->min_shift,
|
|
ilog2(HASH_MIN_SIZE));
|
|
|
|
if (params->nelem_hint)
|
|
size = rounded_hashtable_size(params);
|
|
|
|
memset(ht, 0, sizeof(*ht));
|
|
mutex_init(&ht->mutex);
|
|
memcpy(&ht->p, params, sizeof(*params));
|
|
INIT_LIST_HEAD(&ht->walkers);
|
|
|
|
if (params->locks_mul)
|
|
ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
|
|
else
|
|
ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
|
|
|
|
tbl = bucket_table_alloc(ht, size);
|
|
if (tbl == NULL)
|
|
return -ENOMEM;
|
|
|
|
atomic_set(&ht->nelems, 0);
|
|
atomic_set(&ht->shift, ilog2(tbl->size));
|
|
RCU_INIT_POINTER(ht->tbl, tbl);
|
|
RCU_INIT_POINTER(ht->future_tbl, tbl);
|
|
|
|
if (!ht->p.hash_rnd)
|
|
get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));
|
|
|
|
INIT_WORK(&ht->run_work, rht_deferred_worker);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_init);
|
|
|
|
/**
|
|
* rhashtable_destroy - destroy hash table
|
|
* @ht: the hash table to destroy
|
|
*
|
|
* Frees the bucket array. This function is not rcu safe, therefore the caller
|
|
* has to make sure that no resizing may happen by unpublishing the hashtable
|
|
* and waiting for the quiescent cycle before releasing the bucket array.
|
|
*/
|
|
void rhashtable_destroy(struct rhashtable *ht)
|
|
{
|
|
ht->being_destroyed = true;
|
|
|
|
cancel_work_sync(&ht->run_work);
|
|
|
|
mutex_lock(&ht->mutex);
|
|
bucket_table_free(rht_dereference(ht->tbl, ht));
|
|
mutex_unlock(&ht->mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(rhashtable_destroy);
|