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-rw-r--r--include/linux/rhashtable.h13
-rw-r--r--lib/rhashtable.c52
2 files changed, 16 insertions, 49 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index ae9c0f71f311..3864193d5e2e 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -63,7 +63,6 @@
struct bucket_table {
unsigned int size;
unsigned int nest;
- unsigned int rehash;
u32 hash_rnd;
unsigned int locks_mask;
spinlock_t *locks;
@@ -776,12 +775,6 @@ static inline int rhltable_insert(
* @obj: pointer to hash head inside object
* @params: hash table parameters
*
- * 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.
*
@@ -837,12 +830,6 @@ static inline void *rhashtable_lookup_get_insert_fast(
* @obj: pointer to hash head inside object
* @params: hash table parameters
*
- * 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 residency in the
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 0a105d4af166..776b3a82d3a1 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -197,6 +197,7 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
return NULL;
}
+ rcu_head_init(&tbl->rcu);
INIT_LIST_HEAD(&tbl->walkers);
tbl->hash_rnd = get_random_u32();
@@ -280,10 +281,9 @@ static int rhashtable_rehash_chain(struct rhashtable *ht,
while (!(err = rhashtable_rehash_one(ht, old_hash)))
;
- if (err == -ENOENT) {
- old_tbl->rehash++;
+ if (err == -ENOENT)
err = 0;
- }
+
spin_unlock_bh(old_bucket_lock);
return err;
@@ -330,13 +330,16 @@ static int rhashtable_rehash_table(struct rhashtable *ht)
spin_lock(&ht->lock);
list_for_each_entry(walker, &old_tbl->walkers, list)
walker->tbl = NULL;
- spin_unlock(&ht->lock);
/* Wait for readers. All new readers will see the new
* table, and thus no references to the old table will
* remain.
+ * We do this inside the locked region so that
+ * rhashtable_walk_stop() can use rcu_head_after_call_rcu()
+ * to check if it should not re-link the table.
*/
call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
+ spin_unlock(&ht->lock);
return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
}
@@ -578,46 +581,22 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
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 = rht_dereference_rcu(tbl->future_tbl, ht);
- }
-
- 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);
+ new_tbl = rcu_dereference(ht->tbl);
- while (!IS_ERR_OR_NULL(new_tbl)) {
+ do {
tbl = new_tbl;
hash = rht_head_hashfn(ht, tbl, obj, ht->p);
- spin_lock_nested(rht_bucket_lock(tbl, hash),
- SINGLE_DEPTH_NESTING);
+ spin_lock_bh(rht_bucket_lock(tbl, hash));
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);
+ spin_unlock_bh(rht_bucket_lock(tbl, hash));
+ } while (!IS_ERR_OR_NULL(new_tbl));
if (PTR_ERR(data) == -EAGAIN)
data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
@@ -939,10 +918,11 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter)
ht = iter->ht;
spin_lock(&ht->lock);
- if (tbl->rehash < tbl->size)
- list_add(&iter->walker.list, &tbl->walkers);
- else
+ if (rcu_head_after_call_rcu(&tbl->rcu, bucket_table_free_rcu))
+ /* This bucket table is being freed, don't re-link it. */
iter->walker.tbl = NULL;
+ else
+ list_add(&iter->walker.list, &tbl->walkers);
spin_unlock(&ht->lock);
out: