diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/rhashtable.c | 750 |
1 files changed, 539 insertions, 211 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 6c3c723e902b..aca699813ba9 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -26,15 +26,47 @@ #define HASH_DEFAULT_SIZE 64UL #define HASH_MIN_SIZE 4UL +#define BUCKET_LOCKS_PER_CPU 128UL + +/* Base bits plus 1 bit for nulls marker */ +#define HASH_RESERVED_SPACE (RHT_BASE_BITS + 1) + +enum { + RHT_LOCK_NORMAL, + RHT_LOCK_NESTED, + RHT_LOCK_NESTED2, +}; + +/* The bucket lock is selected based on the hash and protects mutations + * on a group of hash buckets. + * + * IMPORTANT: When holding the bucket lock of both the old and new table + * during expansions and shrinking, the old bucket lock must always be + * acquired first. + */ +static spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash) +{ + return &tbl->locks[hash & tbl->locks_mask]; +} #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT)) +#define ASSERT_BUCKET_LOCK(TBL, HASH) \ + BUG_ON(!lockdep_rht_bucket_is_held(TBL, HASH)) #ifdef CONFIG_PROVE_LOCKING -int lockdep_rht_mutex_is_held(const struct rhashtable *ht) +int lockdep_rht_mutex_is_held(struct rhashtable *ht) { - return ht->p.mutex_is_held(ht->p.parent); + return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1; } EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held); + +int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash) +{ + spinlock_t *lock = bucket_lock(tbl, hash); + + return (debug_locks) ? lockdep_is_held(lock) : 1; +} +EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held); #endif static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he) @@ -42,75 +74,101 @@ static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he) return (void *) he - ht->p.head_offset; } -static u32 __hashfn(const struct rhashtable *ht, const void *key, - u32 len, u32 hsize) +static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash) { - u32 h; + return hash & (tbl->size - 1); +} - h = ht->p.hashfn(key, len, ht->p.hash_rnd); +static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr) +{ + u32 hash; + + if (unlikely(!ht->p.key_len)) + hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd); + else + hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len, + ht->p.hash_rnd); - return h & (hsize - 1); + return hash >> HASH_RESERVED_SPACE; } -/** - * rhashtable_hashfn - compute hash for key of given length - * @ht: hash table to compute for - * @key: pointer to key - * @len: length of key - * - * Computes the hash value using the hash function provided in the 'hashfn' - * of struct rhashtable_params. The returned value is guaranteed to be - * smaller than the number of buckets in the hash table. - */ -u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len) +static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len) { struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); + u32 hash; - return __hashfn(ht, key, len, tbl->size); + hash = ht->p.hashfn(key, len, ht->p.hash_rnd); + hash >>= HASH_RESERVED_SPACE; + + return rht_bucket_index(tbl, hash); } -EXPORT_SYMBOL_GPL(rhashtable_hashfn); -static u32 obj_hashfn(const struct rhashtable *ht, const void *ptr, u32 hsize) +static u32 head_hashfn(const struct rhashtable *ht, + const struct bucket_table *tbl, + const struct rhash_head *he) { - if (unlikely(!ht->p.key_len)) { - u32 h; + return rht_bucket_index(tbl, obj_raw_hashfn(ht, rht_obj(ht, he))); +} - h = ht->p.obj_hashfn(ptr, ht->p.hash_rnd); +static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n) +{ + struct rhash_head __rcu **pprev; - return h & (hsize - 1); - } + for (pprev = &tbl->buckets[n]; + !rht_is_a_nulls(rht_dereference_bucket(*pprev, tbl, n)); + pprev = &rht_dereference_bucket(*pprev, tbl, n)->next) + ; - return __hashfn(ht, ptr + ht->p.key_offset, ht->p.key_len, hsize); + return pprev; } -/** - * rhashtable_obj_hashfn - compute hash for hashed object - * @ht: hash table to compute for - * @ptr: pointer to hashed object - * - * Computes the hash value using the hash function `hashfn` respectively - * 'obj_hashfn' depending on whether the hash table is set up to work with - * a fixed length key. The returned value is guaranteed to be smaller than - * the number of buckets in the hash table. - */ -u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr) +static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl) { - struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); + unsigned int i, size; +#if defined(CONFIG_PROVE_LOCKING) + unsigned int nr_pcpus = 2; +#else + unsigned int nr_pcpus = num_possible_cpus(); +#endif + + nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL); + size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul); + + /* Never allocate more than one lock per bucket */ + size = min_t(unsigned int, size, tbl->size); + + if (sizeof(spinlock_t) != 0) { +#ifdef CONFIG_NUMA + if (size * sizeof(spinlock_t) > PAGE_SIZE) + tbl->locks = vmalloc(size * sizeof(spinlock_t)); + else +#endif + tbl->locks = kmalloc_array(size, sizeof(spinlock_t), + GFP_KERNEL); + if (!tbl->locks) + return -ENOMEM; + for (i = 0; i < size; i++) + spin_lock_init(&tbl->locks[i]); + } + tbl->locks_mask = size - 1; - return obj_hashfn(ht, ptr, tbl->size); + return 0; } -EXPORT_SYMBOL_GPL(rhashtable_obj_hashfn); -static u32 head_hashfn(const struct rhashtable *ht, - const struct rhash_head *he, u32 hsize) +static void bucket_table_free(const struct bucket_table *tbl) { - return obj_hashfn(ht, rht_obj(ht, he), hsize); + if (tbl) + kvfree(tbl->locks); + + kvfree(tbl); } -static struct bucket_table *bucket_table_alloc(size_t nbuckets) +static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, + size_t nbuckets) { struct bucket_table *tbl; size_t size; + int i; size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]); tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); @@ -122,12 +180,15 @@ static struct bucket_table *bucket_table_alloc(size_t nbuckets) tbl->size = nbuckets; - return tbl; -} + if (alloc_bucket_locks(ht, tbl) < 0) { + bucket_table_free(tbl); + return NULL; + } -static void bucket_table_free(const struct bucket_table *tbl) -{ - kvfree(tbl); + for (i = 0; i < nbuckets; i++) + INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i); + + return tbl; } /** @@ -138,7 +199,8 @@ static void bucket_table_free(const struct bucket_table *tbl) bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size) { /* Expand table when exceeding 75% load */ - return ht->nelems > (new_size / 4 * 3); + return atomic_read(&ht->nelems) > (new_size / 4 * 3) && + (ht->p.max_shift && atomic_read(&ht->shift) < ht->p.max_shift); } EXPORT_SYMBOL_GPL(rht_grow_above_75); @@ -150,41 +212,60 @@ EXPORT_SYMBOL_GPL(rht_grow_above_75); bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size) { /* Shrink table beneath 30% load */ - return ht->nelems < (new_size * 3 / 10); + return atomic_read(&ht->nelems) < (new_size * 3 / 10) && + (atomic_read(&ht->shift) > ht->p.min_shift); } EXPORT_SYMBOL_GPL(rht_shrink_below_30); static void hashtable_chain_unzip(const struct rhashtable *ht, const struct bucket_table *new_tbl, - struct bucket_table *old_tbl, size_t n) + struct bucket_table *old_tbl, + size_t old_hash) { struct rhash_head *he, *p, *next; - unsigned int h; + spinlock_t *new_bucket_lock, *new_bucket_lock2 = NULL; + unsigned int new_hash, new_hash2; + + ASSERT_BUCKET_LOCK(old_tbl, old_hash); /* Old bucket empty, no work needed. */ - p = rht_dereference(old_tbl->buckets[n], ht); - if (!p) + p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl, + old_hash); + if (rht_is_a_nulls(p)) return; + new_hash = new_hash2 = head_hashfn(ht, new_tbl, p); + new_bucket_lock = bucket_lock(new_tbl, new_hash); + /* Advance the old bucket pointer one or more times until it * reaches a node that doesn't hash to the same bucket as the * previous node p. Call the previous node p; */ - h = head_hashfn(ht, p, new_tbl->size); - rht_for_each(he, p->next, ht) { - if (head_hashfn(ht, he, new_tbl->size) != h) + rht_for_each_continue(he, p->next, old_tbl, old_hash) { + new_hash2 = head_hashfn(ht, new_tbl, he); + if (new_hash != new_hash2) break; p = he; } - RCU_INIT_POINTER(old_tbl->buckets[n], p->next); + rcu_assign_pointer(old_tbl->buckets[old_hash], p->next); + + spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); + + /* If we have encountered an entry that maps to a different bucket in + * the new table, lock down that bucket as well as we might cut off + * the end of the chain. + */ + new_bucket_lock2 = bucket_lock(new_tbl, new_hash); + if (new_bucket_lock != new_bucket_lock2) + spin_lock_bh_nested(new_bucket_lock2, RHT_LOCK_NESTED2); /* Find the subsequent node which does hash to the same * bucket as node P, or NULL if no such node exists. */ - next = NULL; - if (he) { - rht_for_each(he, he->next, ht) { - if (head_hashfn(ht, he, new_tbl->size) == h) { + INIT_RHT_NULLS_HEAD(next, ht, old_hash); + if (!rht_is_a_nulls(he)) { + rht_for_each_continue(he, he->next, old_tbl, old_hash) { + if (head_hashfn(ht, new_tbl, he) == new_hash) { next = he; break; } @@ -194,7 +275,23 @@ static void hashtable_chain_unzip(const struct rhashtable *ht, /* Set p's next pointer to that subsequent node pointer, * bypassing the nodes which do not hash to p's bucket */ - RCU_INIT_POINTER(p->next, next); + rcu_assign_pointer(p->next, next); + + if (new_bucket_lock != new_bucket_lock2) + spin_unlock_bh(new_bucket_lock2); + spin_unlock_bh(new_bucket_lock); +} + +static void link_old_to_new(struct bucket_table *new_tbl, + unsigned int new_hash, struct rhash_head *entry) +{ + spinlock_t *new_bucket_lock; + + new_bucket_lock = bucket_lock(new_tbl, new_hash); + + spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); + rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry); + spin_unlock_bh(new_bucket_lock); } /** @@ -207,43 +304,56 @@ static void hashtable_chain_unzip(const struct rhashtable *ht, * This function may only be called in a context where it is safe to call * synchronize_rcu(), e.g. not within a rcu_read_lock() section. * - * The caller must ensure that no concurrent table mutations take place. - * It is however valid to have concurrent lookups if they are RCU protected. + * The caller must ensure that no concurrent resizing occurs by holding + * ht->mutex. + * + * It is valid to have concurrent insertions and deletions protected by per + * bucket locks or concurrent RCU protected lookups and traversals. */ int rhashtable_expand(struct rhashtable *ht) { struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht); struct rhash_head *he; - unsigned int i, h; - bool complete; + spinlock_t *old_bucket_lock; + unsigned int new_hash, old_hash; + bool complete = false; ASSERT_RHT_MUTEX(ht); - if (ht->p.max_shift && ht->shift >= ht->p.max_shift) - return 0; - - new_tbl = bucket_table_alloc(old_tbl->size * 2); + new_tbl = bucket_table_alloc(ht, old_tbl->size * 2); if (new_tbl == NULL) return -ENOMEM; - ht->shift++; + atomic_inc(&ht->shift); + + /* Make insertions go into the new, empty table right away. Deletions + * and lookups will be attempted in both tables until we synchronize. + * The synchronize_rcu() guarantees for the new table to be picked up + * so no new additions go into the old table while we relink. + */ + rcu_assign_pointer(ht->future_tbl, new_tbl); + synchronize_rcu(); - /* For each new bucket, search the corresponding old bucket - * for the first entry that hashes to the new bucket, and - * link the new bucket to that entry. Since all the entries - * which will end up in the new bucket appear in the same - * old bucket, this constructs an entirely valid new hash - * table, but with multiple buckets "zipped" together into a - * single imprecise chain. + /* For each new bucket, search the corresponding old bucket for the + * first entry that hashes to the new bucket, and link the end of + * newly formed bucket chain (containing entries added to future + * table) to that entry. Since all the entries which will end up in + * the new bucket appear in the same old bucket, this constructs an + * entirely valid new hash table, but with multiple buckets + * "zipped" together into a single imprecise chain. */ - for (i = 0; i < new_tbl->size; i++) { - h = i & (old_tbl->size - 1); - rht_for_each(he, old_tbl->buckets[h], ht) { - if (head_hashfn(ht, he, new_tbl->size) == i) { - RCU_INIT_POINTER(new_tbl->buckets[i], he); + for (new_hash = 0; new_hash < new_tbl->size; new_hash++) { + old_hash = rht_bucket_index(old_tbl, new_hash); + old_bucket_lock = bucket_lock(old_tbl, old_hash); + + spin_lock_bh(old_bucket_lock); + rht_for_each(he, old_tbl, old_hash) { + if (head_hashfn(ht, new_tbl, he) == new_hash) { + link_old_to_new(new_tbl, new_hash, he); break; } } + spin_unlock_bh(old_bucket_lock); } /* Publish the new table pointer. Lookups may now traverse @@ -253,7 +363,7 @@ int rhashtable_expand(struct rhashtable *ht) rcu_assign_pointer(ht->tbl, new_tbl); /* Unzip interleaved hash chains */ - do { + while (!complete && !ht->being_destroyed) { /* Wait for readers. All new readers will see the new * table, and thus no references to the old table will * remain. @@ -265,12 +375,21 @@ int rhashtable_expand(struct rhashtable *ht) * table): ... */ complete = true; - for (i = 0; i < old_tbl->size; i++) { - hashtable_chain_unzip(ht, new_tbl, old_tbl, i); - if (old_tbl->buckets[i] != NULL) + for (old_hash = 0; old_hash < old_tbl->size; old_hash++) { + struct rhash_head *head; + + old_bucket_lock = bucket_lock(old_tbl, old_hash); + spin_lock_bh(old_bucket_lock); + + hashtable_chain_unzip(ht, new_tbl, old_tbl, old_hash); + head = rht_dereference_bucket(old_tbl->buckets[old_hash], + old_tbl, old_hash); + if (!rht_is_a_nulls(head)) complete = false; + + spin_unlock_bh(old_bucket_lock); } - } while (!complete); + } bucket_table_free(old_tbl); return 0; @@ -284,45 +403,71 @@ EXPORT_SYMBOL_GPL(rhashtable_expand); * This function may only be called in a context where it is safe to call * synchronize_rcu(), e.g. not within a rcu_read_lock() section. * + * The caller must ensure that no concurrent resizing occurs by holding + * ht->mutex. + * * The caller must ensure that no concurrent table mutations take place. * It is however valid to have concurrent lookups if they are RCU protected. + * + * It is valid to have concurrent insertions and deletions protected by per + * bucket locks or concurrent RCU protected lookups and traversals. */ int rhashtable_shrink(struct rhashtable *ht) { - struct bucket_table *ntbl, *tbl = rht_dereference(ht->tbl, ht); - struct rhash_head __rcu **pprev; - unsigned int i; + struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht); + spinlock_t *new_bucket_lock, *old_bucket_lock1, *old_bucket_lock2; + unsigned int new_hash; ASSERT_RHT_MUTEX(ht); - if (ht->shift <= ht->p.min_shift) - return 0; - - ntbl = bucket_table_alloc(tbl->size / 2); - if (ntbl == NULL) + new_tbl = bucket_table_alloc(ht, tbl->size / 2); + if (new_tbl == NULL) return -ENOMEM; - ht->shift--; + rcu_assign_pointer(ht->future_tbl, new_tbl); + synchronize_rcu(); - /* Link each bucket in the new table to the first bucket - * in the old table that contains entries which will hash - * to the new bucket. + /* Link the first entry in the old bucket to the end of the + * bucket in the new table. As entries are concurrently being + * added to the new table, lock down the new bucket. As we + * always divide the size in half when shrinking, each bucket + * in the new table maps to exactly two buckets in the old + * table. + * + * As removals can occur concurrently on the old table, we need + * to lock down both matching buckets in the old table. */ - for (i = 0; i < ntbl->size; i++) { - ntbl->buckets[i] = tbl->buckets[i]; + for (new_hash = 0; new_hash < new_tbl->size; new_hash++) { + old_bucket_lock1 = bucket_lock(tbl, new_hash); + old_bucket_lock2 = bucket_lock(tbl, new_hash + new_tbl->size); + new_bucket_lock = bucket_lock(new_tbl, new_hash); + + spin_lock_bh(old_bucket_lock1); - /* Link each bucket in the new table to the first bucket - * in the old table that contains entries which will hash - * to the new bucket. + /* Depending on the lock per buckets mapping, the bucket in + * the lower and upper region may map to the same lock. */ - for (pprev = &ntbl->buckets[i]; *pprev != NULL; - pprev = &rht_dereference(*pprev, ht)->next) - ; - RCU_INIT_POINTER(*pprev, tbl->buckets[i + ntbl->size]); + if (old_bucket_lock1 != old_bucket_lock2) { + spin_lock_bh_nested(old_bucket_lock2, RHT_LOCK_NESTED); + spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED2); + } else { + spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); + } + + rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), + tbl->buckets[new_hash]); + rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), + tbl->buckets[new_hash + new_tbl->size]); + + spin_unlock_bh(new_bucket_lock); + if (old_bucket_lock1 != old_bucket_lock2) + spin_unlock_bh(old_bucket_lock2); + spin_unlock_bh(old_bucket_lock1); } /* Publish the new, valid hash table */ - rcu_assign_pointer(ht->tbl, ntbl); + 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. @@ -335,59 +480,88 @@ int rhashtable_shrink(struct rhashtable *ht) } EXPORT_SYMBOL_GPL(rhashtable_shrink); -/** - * rhashtable_insert - insert object into hash hash table - * @ht: hash table - * @obj: pointer to hash head inside object - * - * Will automatically grow the table via rhashtable_expand() if the the - * grow_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. - */ -void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj) +static void rht_deferred_worker(struct work_struct *work) { - struct bucket_table *tbl = rht_dereference(ht->tbl, ht); - u32 hash; - - ASSERT_RHT_MUTEX(ht); + struct rhashtable *ht; + struct bucket_table *tbl; - hash = head_hashfn(ht, obj, tbl->size); - RCU_INIT_POINTER(obj->next, tbl->buckets[hash]); - rcu_assign_pointer(tbl->buckets[hash], obj); - ht->nelems++; + ht = container_of(work, struct rhashtable, run_work.work); + mutex_lock(&ht->mutex); + tbl = rht_dereference(ht->tbl, ht); if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size)) rhashtable_expand(ht); + else if (ht->p.shrink_decision && ht->p.shrink_decision(ht, tbl->size)) + rhashtable_shrink(ht); + + mutex_unlock(&ht->mutex); +} + +static void rhashtable_wakeup_worker(struct rhashtable *ht) +{ + struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); + struct bucket_table *new_tbl = rht_dereference_rcu(ht->future_tbl, ht); + size_t size = tbl->size; + + /* Only adjust the table if no resizing is currently in progress. */ + if (tbl == new_tbl && + ((ht->p.grow_decision && ht->p.grow_decision(ht, size)) || + (ht->p.shrink_decision && ht->p.shrink_decision(ht, size)))) + schedule_delayed_work(&ht->run_work, 0); +} + +static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj, + struct bucket_table *tbl, u32 hash) +{ + struct rhash_head *head = rht_dereference_bucket(tbl->buckets[hash], + 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); + + rhashtable_wakeup_worker(ht); } -EXPORT_SYMBOL_GPL(rhashtable_insert); /** - * rhashtable_remove_pprev - remove object from hash table given previous element + * rhashtable_insert - insert object into hash table * @ht: hash table * @obj: pointer to hash head inside object - * @pprev: pointer to previous element * - * Identical to rhashtable_remove() but caller is alreayd aware of the element - * in front of the element to be deleted. This is in particular useful for - * deletion when combined with walking or lookup. + * 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_remove_pprev(struct rhashtable *ht, struct rhash_head *obj, - struct rhash_head __rcu **pprev) +void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj) { - struct bucket_table *tbl = rht_dereference(ht->tbl, ht); + struct bucket_table *tbl; + spinlock_t *lock; + unsigned hash; - ASSERT_RHT_MUTEX(ht); + rcu_read_lock(); - RCU_INIT_POINTER(*pprev, obj->next); - ht->nelems--; + tbl = rht_dereference_rcu(ht->future_tbl, ht); + hash = head_hashfn(ht, tbl, obj); + lock = bucket_lock(tbl, hash); - if (ht->p.shrink_decision && - ht->p.shrink_decision(ht, tbl->size)) - rhashtable_shrink(ht); + spin_lock_bh(lock); + __rhashtable_insert(ht, obj, tbl, hash); + spin_unlock_bh(lock); + + rcu_read_unlock(); } -EXPORT_SYMBOL_GPL(rhashtable_remove_pprev); +EXPORT_SYMBOL_GPL(rhashtable_insert); /** * rhashtable_remove - remove object from hash table @@ -398,7 +572,7 @@ EXPORT_SYMBOL_GPL(rhashtable_remove_pprev); * 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 the + * 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 @@ -406,30 +580,70 @@ EXPORT_SYMBOL_GPL(rhashtable_remove_pprev); */ bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj) { - struct bucket_table *tbl = rht_dereference(ht->tbl, ht); + struct bucket_table *tbl; struct rhash_head __rcu **pprev; struct rhash_head *he; - u32 h; + spinlock_t *lock; + unsigned int hash; - ASSERT_RHT_MUTEX(ht); + rcu_read_lock(); + tbl = rht_dereference_rcu(ht->tbl, ht); + hash = head_hashfn(ht, tbl, obj); - h = head_hashfn(ht, obj, tbl->size); + lock = bucket_lock(tbl, hash); + spin_lock_bh(lock); - pprev = &tbl->buckets[h]; - rht_for_each(he, tbl->buckets[h], ht) { +restart: + pprev = &tbl->buckets[hash]; + rht_for_each(he, tbl, hash) { if (he != obj) { pprev = &he->next; continue; } - rhashtable_remove_pprev(ht, he, pprev); + rcu_assign_pointer(*pprev, obj->next); + atomic_dec(&ht->nelems); + + spin_unlock_bh(lock); + + rhashtable_wakeup_worker(ht); + + rcu_read_unlock(); + return true; } + if (tbl != rht_dereference_rcu(ht->future_tbl, ht)) { + spin_unlock_bh(lock); + + tbl = rht_dereference_rcu(ht->future_tbl, ht); + hash = head_hashfn(ht, tbl, obj); + + lock = bucket_lock(tbl, hash); + spin_lock_bh(lock); + goto restart; + } + + spin_unlock_bh(lock); + rcu_read_unlock(); + return false; } 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 @@ -439,65 +653,165 @@ EXPORT_SYMBOL_GPL(rhashtable_remove); * 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 - * paramter set). It will BUG() if used inappropriately. + * parameter set). It will BUG() if used inappropriately. * - * Lookups may occur in parallel with hash mutations as long as the lookup is - * guarded by rcu_read_lock(). The caller must take care of this. + * Lookups may occur in parallel with hashtable mutations and resizing. */ -void *rhashtable_lookup(const struct rhashtable *ht, const void *key) +void *rhashtable_lookup(struct rhashtable *ht, const void *key) { - const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); - struct rhash_head *he; - u32 h; + struct rhashtable_compare_arg arg = { + .ht = ht, + .key = key, + }; BUG_ON(!ht->p.key_len); - h = __hashfn(ht, key, ht->p.key_len, tbl->size); - rht_for_each_rcu(he, tbl->buckets[h], ht) { - if (memcmp(rht_obj(ht, he) + ht->p.key_offset, key, - ht->p.key_len)) - continue; - return (void *) he - ht->p.head_offset; - } - - return NULL; + 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 - * @hash: hash value of desired entry + * @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 hash mutations as long as the lookup is - * guarded by rcu_read_lock(). The caller must take care of this. + * 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(const struct rhashtable *ht, u32 hash, +void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key, bool (*compare)(void *, void *), void *arg) { - const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); + const struct bucket_table *tbl, *old_tbl; struct rhash_head *he; + u32 hash; - if (unlikely(hash >= tbl->size)) - return NULL; + rcu_read_lock(); - rht_for_each_rcu(he, tbl->buckets[hash], ht) { + 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; - return (void *) he - ht->p.head_offset; + 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; + spinlock_t *new_bucket_lock, *old_bucket_lock; + u32 new_hash, old_hash; + bool success = true; + + BUG_ON(!ht->p.key_len); + + rcu_read_lock(); + + old_tbl = rht_dereference_rcu(ht->tbl, ht); + old_hash = head_hashfn(ht, old_tbl, obj); + old_bucket_lock = bucket_lock(old_tbl, old_hash); + spin_lock_bh(old_bucket_lock); + + new_tbl = rht_dereference_rcu(ht->future_tbl, ht); + new_hash = head_hashfn(ht, new_tbl, obj); + new_bucket_lock = bucket_lock(new_tbl, new_hash); + if (unlikely(old_tbl != new_tbl)) + spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); + + 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, new_hash); + +exit: + if (unlikely(old_tbl != new_tbl)) + spin_unlock_bh(new_bucket_lock); + spin_unlock_bh(old_bucket_lock); + + rcu_read_unlock(); + + return success; +} +EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert); + static size_t rounded_hashtable_size(struct rhashtable_params *params) { return max(roundup_pow_of_two(params->nelem_hint * 4 / 3), @@ -525,9 +839,7 @@ static size_t rounded_hashtable_size(struct rhashtable_params *params) * .key_offset = offsetof(struct test_obj, key), * .key_len = sizeof(int), * .hashfn = jhash, - * #ifdef CONFIG_PROVE_LOCKING - * .mutex_is_held = &my_mutex_is_held, - * #endif + * .nulls_base = (1U << RHT_BASE_SHIFT), * }; * * Configuration Example 2: Variable length keys @@ -547,9 +859,6 @@ static size_t rounded_hashtable_size(struct rhashtable_params *params) * .head_offset = offsetof(struct test_obj, node), * .hashfn = jhash, * .obj_hashfn = my_hash_fn, - * #ifdef CONFIG_PROVE_LOCKING - * .mutex_is_held = &my_mutex_is_held, - * #endif * }; */ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) @@ -563,24 +872,39 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) (!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); - tbl = bucket_table_alloc(size); + memset(ht, 0, sizeof(*ht)); + mutex_init(&ht->mutex); + memcpy(&ht->p, params, sizeof(*params)); + + 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; - memset(ht, 0, sizeof(*ht)); - ht->shift = ilog2(tbl->size); - memcpy(&ht->p, params, sizeof(*params)); + 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)); + if (ht->p.grow_decision || ht->p.shrink_decision) + INIT_DEFERRABLE_WORK(&ht->run_work, rht_deferred_worker); + return 0; } EXPORT_SYMBOL_GPL(rhashtable_init); @@ -593,9 +917,16 @@ EXPORT_SYMBOL_GPL(rhashtable_init); * 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(const struct rhashtable *ht) +void rhashtable_destroy(struct rhashtable *ht) { - bucket_table_free(ht->tbl); + ht->being_destroyed = true; + + mutex_lock(&ht->mutex); + + cancel_delayed_work(&ht->run_work); + bucket_table_free(rht_dereference(ht->tbl, ht)); + + mutex_unlock(&ht->mutex); } EXPORT_SYMBOL_GPL(rhashtable_destroy); @@ -610,13 +941,6 @@ EXPORT_SYMBOL_GPL(rhashtable_destroy); #define TEST_PTR ((void *) 0xdeadbeef) #define TEST_NEXPANDS 4 -#ifdef CONFIG_PROVE_LOCKING -static int test_mutex_is_held(void *parent) -{ - return 1; -} -#endif - struct test_obj { void *ptr; int value; @@ -656,6 +980,7 @@ static int __init test_rht_lookup(struct rhashtable *ht) static void test_bucket_stats(struct rhashtable *ht, bool quiet) { unsigned int cnt, rcu_cnt, i, total = 0; + struct rhash_head *pos; struct test_obj *obj; struct bucket_table *tbl; @@ -666,14 +991,14 @@ static void test_bucket_stats(struct rhashtable *ht, bool quiet) if (!quiet) pr_info(" [%#4x/%zu]", i, tbl->size); - rht_for_each_entry_rcu(obj, tbl->buckets[i], node) { + rht_for_each_entry_rcu(obj, pos, tbl, i, node) { cnt++; total++; if (!quiet) pr_cont(" [%p],", obj); } - rht_for_each_entry_rcu(obj, tbl->buckets[i], node) + rht_for_each_entry_rcu(obj, pos, tbl, i, node) rcu_cnt++; if (rcu_cnt != cnt) @@ -685,17 +1010,18 @@ static void test_bucket_stats(struct rhashtable *ht, bool quiet) i, tbl->buckets[i], cnt); } - pr_info(" Traversal complete: counted=%u, nelems=%zu, entries=%d\n", - total, ht->nelems, TEST_ENTRIES); + pr_info(" Traversal complete: counted=%u, nelems=%u, entries=%d\n", + total, atomic_read(&ht->nelems), TEST_ENTRIES); - if (total != ht->nelems || total != TEST_ENTRIES) + if (total != atomic_read(&ht->nelems) || total != TEST_ENTRIES) pr_warn("Test failed: Total count mismatch ^^^"); } static int __init test_rhashtable(struct rhashtable *ht) { struct bucket_table *tbl; - struct test_obj *obj, *next; + struct test_obj *obj; + struct rhash_head *pos, *next; int err; unsigned int i; @@ -726,7 +1052,9 @@ static int __init test_rhashtable(struct rhashtable *ht) for (i = 0; i < TEST_NEXPANDS; i++) { pr_info(" Table expansion iteration %u...\n", i); + mutex_lock(&ht->mutex); rhashtable_expand(ht); + mutex_unlock(&ht->mutex); rcu_read_lock(); pr_info(" Verifying lookups...\n"); @@ -736,7 +1064,9 @@ static int __init test_rhashtable(struct rhashtable *ht) for (i = 0; i < TEST_NEXPANDS; i++) { pr_info(" Table shrinkage iteration %u...\n", i); + mutex_lock(&ht->mutex); rhashtable_shrink(ht); + mutex_unlock(&ht->mutex); rcu_read_lock(); pr_info(" Verifying lookups...\n"); @@ -764,7 +1094,7 @@ static int __init test_rhashtable(struct rhashtable *ht) error: tbl = rht_dereference_rcu(ht->tbl, ht); for (i = 0; i < tbl->size; i++) - rht_for_each_entry_safe(obj, next, tbl->buckets[i], ht, node) + rht_for_each_entry_safe(obj, pos, next, tbl, i, node) kfree(obj); return err; @@ -779,9 +1109,7 @@ static int __init test_rht_init(void) .key_offset = offsetof(struct test_obj, value), .key_len = sizeof(int), .hashfn = jhash, -#ifdef CONFIG_PROVE_LOCKING - .mutex_is_held = &test_mutex_is_held, -#endif + .nulls_base = (3U << RHT_BASE_SHIFT), .grow_decision = rht_grow_above_75, .shrink_decision = rht_shrink_below_30, }; |