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authorHerbert Xu <herbert@gondor.apana.org.au>2016-09-19 14:00:09 +0300
committerDavid S. Miller <davem@davemloft.net>2016-09-20 11:43:36 +0300
commitca26893f05e86497a86732768ec53cd38c0819ca (patch)
tree218c887b7aeff5ff30bdd0fe9fecc37ffc1f6935 /lib
parentfd07160bb7180cdd0afeb089d8cdfd66002f17e6 (diff)
downloadlinux-ca26893f05e86497a86732768ec53cd38c0819ca.tar.xz
rhashtable: Add rhlist interface
The insecure_elasticity setting is an ugly wart brought out by users who need to insert duplicate objects (that is, distinct objects with identical keys) into the same table. In fact, those users have a much bigger problem. Once those duplicate objects are inserted, they don't have an interface to find them (unless you count the walker interface which walks over the entire table). Some users have resorted to doing a manual walk over the hash table which is of course broken because they don't handle the potential existence of multiple hash tables. The result is that they will break sporadically when they encounter a hash table resize/rehash. This patch provides a way out for those users, at the expense of an extra pointer per object. Essentially each object is now a list of objects carrying the same key. The hash table will only see the lists so nothing changes as far as rhashtable is concerned. To use this new interface, you need to insert a struct rhlist_head into your objects instead of struct rhash_head. While the hash table is unchanged, for type-safety you'll need to use struct rhltable instead of struct rhashtable. All the existing interfaces have been duplicated for rhlist, including the hash table walker. One missing feature is nulls marking because AFAIK the only potential user of it does not need duplicate objects. Should anyone need this it shouldn't be too hard to add. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
-rw-r--r--lib/rhashtable.c258
1 files changed, 206 insertions, 52 deletions
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 06c28728bb53..32d0ad058380 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -378,22 +378,8 @@ static void rht_deferred_worker(struct work_struct *work)
schedule_work(&ht->run_work);
}
-static bool rhashtable_check_elasticity(struct rhashtable *ht,
- struct bucket_table *tbl,
- unsigned int hash)
-{
- unsigned int elasticity = ht->elasticity;
- struct rhash_head *head;
-
- rht_for_each(head, tbl, hash)
- if (!--elasticity)
- return true;
-
- return false;
-}
-
-int rhashtable_insert_rehash(struct rhashtable *ht,
- struct bucket_table *tbl)
+static int rhashtable_insert_rehash(struct rhashtable *ht,
+ struct bucket_table *tbl)
{
struct bucket_table *old_tbl;
struct bucket_table *new_tbl;
@@ -439,57 +425,165 @@ fail:
return err;
}
-EXPORT_SYMBOL_GPL(rhashtable_insert_rehash);
-struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
- const void *key,
- struct rhash_head *obj,
- struct bucket_table *tbl,
- void **data)
+static void *rhashtable_lookup_one(struct rhashtable *ht,
+ struct bucket_table *tbl, unsigned int hash,
+ const void *key, struct rhash_head *obj)
{
+ struct rhashtable_compare_arg arg = {
+ .ht = ht,
+ .key = key,
+ };
+ struct rhash_head __rcu **pprev;
struct rhash_head *head;
- unsigned int hash;
- int err;
+ int elasticity;
- tbl = rhashtable_last_table(ht, tbl);
- hash = head_hashfn(ht, tbl, obj);
- spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
-
- err = -EEXIST;
- if (key) {
- *data = rhashtable_lookup_fast(ht, key, ht->p);
- if (*data)
- goto exit;
+ elasticity = ht->elasticity;
+ pprev = &tbl->buckets[hash];
+ rht_for_each(head, tbl, hash) {
+ struct rhlist_head *list;
+ struct rhlist_head *plist;
+
+ elasticity--;
+ if (!key ||
+ (ht->p.obj_cmpfn ?
+ ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
+ rhashtable_compare(&arg, rht_obj(ht, head))))
+ continue;
+
+ if (!ht->rhlist)
+ return rht_obj(ht, head);
+
+ list = container_of(obj, struct rhlist_head, rhead);
+ plist = container_of(head, struct rhlist_head, rhead);
+
+ RCU_INIT_POINTER(list->next, plist);
+ head = rht_dereference_bucket(head->next, tbl, hash);
+ RCU_INIT_POINTER(list->rhead.next, head);
+ rcu_assign_pointer(*pprev, obj);
+
+ return NULL;
}
- err = -E2BIG;
- if (unlikely(rht_grow_above_max(ht, tbl)))
- goto exit;
+ if (elasticity <= 0)
+ return ERR_PTR(-EAGAIN);
+
+ return ERR_PTR(-ENOENT);
+}
+
+static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
+ 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);
- err = -EAGAIN;
- if (rhashtable_check_elasticity(ht, tbl, hash) ||
- rht_grow_above_100(ht, tbl))
- goto exit;
+ if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
+ return ERR_CAST(data);
- err = 0;
+ new_tbl = rcu_dereference(tbl->future_tbl);
+ 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_dereference_bucket(tbl->buckets[hash], 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);
+ }
rcu_assign_pointer(tbl->buckets[hash], obj);
atomic_inc(&ht->nelems);
+ if (rht_grow_above_75(ht, tbl))
+ schedule_work(&ht->run_work);
-exit:
- spin_unlock(rht_bucket_lock(tbl, hash));
+ return NULL;
+}
- if (err == 0)
- return NULL;
- else if (err == -EAGAIN)
- return tbl;
- else
- return ERR_PTR(err);
+static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
+ struct rhash_head *obj)
+{
+ struct bucket_table *new_tbl;
+ struct bucket_table *tbl;
+ unsigned int hash;
+ spinlock_t *lock;
+ void *data;
+
+ tbl = rcu_dereference(ht->tbl);
+
+ /* All insertions must grab the oldest table containing
+ * the hashed bucket that is yet to be rehashed.
+ */
+ for (;;) {
+ hash = rht_head_hashfn(ht, tbl, obj, ht->p);
+ lock = rht_bucket_lock(tbl, hash);
+ spin_lock_bh(lock);
+
+ if (tbl->rehash <= hash)
+ break;
+
+ spin_unlock_bh(lock);
+ tbl = rcu_dereference(tbl->future_tbl);
+ }
+
+ data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
+ new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
+ if (PTR_ERR(new_tbl) != -EEXIST)
+ data = ERR_CAST(new_tbl);
+
+ while (!IS_ERR_OR_NULL(new_tbl)) {
+ tbl = new_tbl;
+ hash = rht_head_hashfn(ht, tbl, obj, ht->p);
+ spin_lock_nested(rht_bucket_lock(tbl, hash),
+ SINGLE_DEPTH_NESTING);
+
+ data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
+ new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
+ if (PTR_ERR(new_tbl) != -EEXIST)
+ data = ERR_CAST(new_tbl);
+
+ spin_unlock(rht_bucket_lock(tbl, hash));
+ }
+
+ spin_unlock_bh(lock);
+
+ 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);
@@ -593,11 +687,16 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_start);
void *rhashtable_walk_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 (p) {
- p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);
+ if (!rhlist || !(list = rcu_dereference(list->next))) {
+ p = rcu_dereference(p->next);
+ list = container_of(p, struct rhlist_head, rhead);
+ }
goto next;
}
@@ -605,6 +704,18 @@ void *rhashtable_walk_next(struct rhashtable_iter *iter)
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--;
@@ -614,7 +725,8 @@ next:
if (!rht_is_a_nulls(p)) {
iter->skip++;
iter->p = p;
- return rht_obj(ht, p);
+ iter->list = list;
+ return rht_obj(ht, rhlist ? &list->rhead : p);
}
iter->skip = 0;
@@ -803,6 +915,48 @@ int rhashtable_init(struct rhashtable *ht,
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;
+
+ /* No rhlist NULLs marking for now. */
+ if (params->nulls_base)
+ return -EINVAL;
+
+ 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
@@ -839,7 +993,7 @@ void rhashtable_free_and_destroy(struct rhashtable *ht,
pos = next,
next = !rht_is_a_nulls(pos) ?
rht_dereference(pos->next, ht) : NULL)
- free_fn(rht_obj(ht, pos), arg);
+ rhashtable_free_one(ht, pos, free_fn, arg);
}
}