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authorDavid S. Miller <davem@davemloft.net>2019-03-21 14:01:10 -0700
committerDavid S. Miller <davem@davemloft.net>2019-03-21 14:01:10 -0700
commit143eb9ac9fd90a1b3d1b35504fabe849af732e42 (patch)
treeef06326ec2416d68d576a92ba3ed5b2be45f14b7
parentMerge branch 'net-phy-Move-Omega-PHY-entry-to-Cygnus-PHY-driver' (diff)
parentrhashtable: rename rht_for_each*continue as *from. (diff)
downloadlinux-dev-143eb9ac9fd90a1b3d1b35504fabe849af732e42.tar.xz
linux-dev-143eb9ac9fd90a1b3d1b35504fabe849af732e42.zip
Merge branch 'rhashtable-cleanups'
NeilBrown says: ==================== Two clean-ups for rhashtable. These two patches make small improvements to rhashtable, but are otherwise unrelated. Thanks to Herbert, Miguel, and Paul for the review. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--.clang-format8
-rw-r--r--include/linux/rhashtable.h53
-rw-r--r--lib/rhashtable.c54
3 files changed, 41 insertions, 74 deletions
diff --git a/.clang-format b/.clang-format
index f49620f506f1..3a4c8220df2f 100644
--- a/.clang-format
+++ b/.clang-format
@@ -366,14 +366,14 @@ ForEachMacros:
- 'rhl_for_each_entry_rcu'
- 'rhl_for_each_rcu'
- 'rht_for_each'
- - 'rht_for_each_continue'
+ - 'rht_for_each_from'
- 'rht_for_each_entry'
- - 'rht_for_each_entry_continue'
+ - 'rht_for_each_entry_from'
- 'rht_for_each_entry_rcu'
- - 'rht_for_each_entry_rcu_continue'
+ - 'rht_for_each_entry_rcu_from'
- 'rht_for_each_entry_safe'
- 'rht_for_each_rcu'
- - 'rht_for_each_rcu_continue'
+ - 'rht_for_each_rcu_from'
- '__rq_for_each_bio'
- 'rq_for_each_segment'
- 'scsi_for_each_prot_sg'
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index ae9c0f71f311..86dfa417848d 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;
@@ -307,13 +306,13 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
}
/**
- * rht_for_each_continue - continue iterating over hash chain
+ * rht_for_each_from - iterate over hash chain from given head
* @pos: the &struct rhash_head to use as a loop cursor.
- * @head: the previous &struct rhash_head to continue from
+ * @head: the &struct rhash_head to start from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
*/
-#define rht_for_each_continue(pos, head, tbl, hash) \
+#define rht_for_each_from(pos, head, tbl, hash) \
for (pos = rht_dereference_bucket(head, tbl, hash); \
!rht_is_a_nulls(pos); \
pos = rht_dereference_bucket((pos)->next, tbl, hash))
@@ -325,18 +324,18 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
* @hash: the hash value / bucket index
*/
#define rht_for_each(pos, tbl, hash) \
- rht_for_each_continue(pos, *rht_bucket(tbl, hash), tbl, hash)
+ rht_for_each_from(pos, *rht_bucket(tbl, hash), tbl, hash)
/**
- * rht_for_each_entry_continue - continue iterating over hash chain
+ * rht_for_each_entry_from - iterate over hash chain from given head
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
- * @head: the previous &struct rhash_head to continue from
+ * @head: the &struct rhash_head to start from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct rhash_head within the hashable struct.
*/
-#define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
+#define rht_for_each_entry_from(tpos, pos, head, tbl, hash, member) \
for (pos = rht_dereference_bucket(head, tbl, hash); \
(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
pos = rht_dereference_bucket((pos)->next, tbl, hash))
@@ -350,7 +349,7 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
* @member: name of the &struct rhash_head within the hashable struct.
*/
#define rht_for_each_entry(tpos, pos, tbl, hash, member) \
- rht_for_each_entry_continue(tpos, pos, *rht_bucket(tbl, hash), \
+ rht_for_each_entry_from(tpos, pos, *rht_bucket(tbl, hash), \
tbl, hash, member)
/**
@@ -375,9 +374,9 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
rht_dereference_bucket(pos->next, tbl, hash) : NULL)
/**
- * rht_for_each_rcu_continue - continue iterating over rcu hash chain
+ * rht_for_each_rcu_from - iterate over rcu hash chain from given head
* @pos: the &struct rhash_head to use as a loop cursor.
- * @head: the previous &struct rhash_head to continue from
+ * @head: the &struct rhash_head to start from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
*
@@ -385,7 +384,7 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
* the _rcu mutation primitives such as rhashtable_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
-#define rht_for_each_rcu_continue(pos, head, tbl, hash) \
+#define rht_for_each_rcu_from(pos, head, tbl, hash) \
for (({barrier(); }), \
pos = rht_dereference_bucket_rcu(head, tbl, hash); \
!rht_is_a_nulls(pos); \
@@ -402,13 +401,13 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_rcu(pos, tbl, hash) \
- rht_for_each_rcu_continue(pos, *rht_bucket(tbl, hash), tbl, hash)
+ rht_for_each_rcu_from(pos, *rht_bucket(tbl, hash), tbl, hash)
/**
- * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
+ * rht_for_each_entry_rcu_from - iterated over rcu hash chain from given head
* @tpos: the type * to use as a loop cursor.
* @pos: the &struct rhash_head to use as a loop cursor.
- * @head: the previous &struct rhash_head to continue from
+ * @head: the &struct rhash_head to start from
* @tbl: the &struct bucket_table
* @hash: the hash value / bucket index
* @member: name of the &struct rhash_head within the hashable struct.
@@ -417,7 +416,7 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
* the _rcu mutation primitives such as rhashtable_insert() as long as the
* traversal is guarded by rcu_read_lock().
*/
-#define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
+#define rht_for_each_entry_rcu_from(tpos, pos, head, tbl, hash, member) \
for (({barrier(); }), \
pos = rht_dereference_bucket_rcu(head, tbl, hash); \
(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
@@ -436,7 +435,7 @@ static inline struct rhash_head __rcu **rht_bucket_insert(
* traversal is guarded by rcu_read_lock().
*/
#define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
- rht_for_each_entry_rcu_continue(tpos, pos, *rht_bucket(tbl, hash), \
+ rht_for_each_entry_rcu_from(tpos, pos, *rht_bucket(tbl, hash), \
tbl, hash, member)
/**
@@ -492,7 +491,7 @@ restart:
hash = rht_key_hashfn(ht, tbl, key, params);
head = rht_bucket(tbl, hash);
do {
- rht_for_each_rcu_continue(he, *head, tbl, hash) {
+ rht_for_each_rcu_from(he, *head, tbl, hash) {
if (params.obj_cmpfn ?
params.obj_cmpfn(&arg, rht_obj(ht, he)) :
rhashtable_compare(&arg, rht_obj(ht, he)))
@@ -626,7 +625,7 @@ slow_path:
if (!pprev)
goto out;
- rht_for_each_continue(head, *pprev, tbl, hash) {
+ rht_for_each_from(head, *pprev, tbl, hash) {
struct rhlist_head *plist;
struct rhlist_head *list;
@@ -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
@@ -903,7 +890,7 @@ static inline int __rhashtable_remove_fast_one(
spin_lock_bh(lock);
pprev = rht_bucket_var(tbl, hash);
- rht_for_each_continue(he, *pprev, tbl, hash) {
+ rht_for_each_from(he, *pprev, tbl, hash) {
struct rhlist_head *list;
list = container_of(he, struct rhlist_head, rhead);
@@ -1055,7 +1042,7 @@ static inline int __rhashtable_replace_fast(
spin_lock_bh(lock);
pprev = rht_bucket_var(tbl, hash);
- rht_for_each_continue(he, *pprev, tbl, hash) {
+ rht_for_each_from(he, *pprev, tbl, hash) {
if (he != obj_old) {
pprev = &he->next;
continue;
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 0a105d4af166..f65e43fb1ff8 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;
}
@@ -487,7 +490,7 @@ static void *rhashtable_lookup_one(struct rhashtable *ht,
elasticity = RHT_ELASTICITY;
pprev = rht_bucket_var(tbl, hash);
- rht_for_each_continue(head, *pprev, tbl, hash) {
+ rht_for_each_from(head, *pprev, tbl, hash) {
struct rhlist_head *list;
struct rhlist_head *plist;
@@ -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: