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![Herbert Xu](/assets/img/avatar_default.png)
This patch deals with the complaint that we make indirect function calls on the fast paths unnecessarily in rhashtable. We resolve it by moving the fast paths into inline functions that take struct rhashtable_param (which obviously must be the same set of parameters supplied to rhashtable_init) as an argument. The only remaining indirect call is to obj_hashfn (or key_hashfn it obj_hashfn is unset) on the rehash as well as the insert-during- rehash slow path. This patch also extends the support of vairable-length keys to include those where the key is fixed but scattered in the object. For example, in netlink we want to key off the namespace and the portid but they're not next to each other. This patch does this by directly using the object hash function as the indicator of whether the key is accessible or not. It also adds a new function obj_cmpfn to compare a key against an object. This means that the caller no longer needs to supply explicit compare functions. All this is done in a backwards compatible manner so no existing users are affected until they convert to the new interface. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
745 lines
23 KiB
C
745 lines
23 KiB
C
/*
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* Resizable, Scalable, Concurrent Hash Table
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*
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* Copyright (c) 2014 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 by Josh Triplett, Paul E. McKenney
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* and Jonathan Walpole:
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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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#ifndef _LINUX_RHASHTABLE_H
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#define _LINUX_RHASHTABLE_H
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#include <linux/compiler.h>
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#include <linux/list_nulls.h>
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#include <linux/workqueue.h>
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#include <linux/mutex.h>
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#include <linux/rcupdate.h>
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/*
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* The end of the chain is marked with a special nulls marks which has
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* the following format:
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*
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* +-------+-----------------------------------------------------+-+
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* | Base | Hash |1|
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* +-------+-----------------------------------------------------+-+
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*
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* Base (4 bits) : Reserved to distinguish between multiple tables.
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* Specified via &struct rhashtable_params.nulls_base.
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* Hash (27 bits): Full hash (unmasked) of first element added to bucket
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* 1 (1 bit) : Nulls marker (always set)
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*
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* The remaining bits of the next pointer remain unused for now.
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*/
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#define RHT_BASE_BITS 4
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#define RHT_HASH_BITS 27
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#define RHT_BASE_SHIFT RHT_HASH_BITS
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/* Base bits plus 1 bit for nulls marker */
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#define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
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struct rhash_head {
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struct rhash_head __rcu *next;
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};
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/**
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* struct bucket_table - Table of hash buckets
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* @size: Number of hash buckets
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* @rehash: Current bucket being rehashed
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* @hash_rnd: Random seed to fold into hash
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* @locks_mask: Mask to apply before accessing locks[]
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* @locks: Array of spinlocks protecting individual buckets
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* @walkers: List of active walkers
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* @rcu: RCU structure for freeing the table
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* @future_tbl: Table under construction during rehashing
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* @buckets: size * hash buckets
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*/
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struct bucket_table {
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unsigned int size;
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unsigned int rehash;
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u32 hash_rnd;
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unsigned int locks_mask;
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spinlock_t *locks;
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struct list_head walkers;
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struct rcu_head rcu;
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struct bucket_table __rcu *future_tbl;
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struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
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};
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/**
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* struct rhashtable_compare_arg - Key for the function rhashtable_compare
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* @ht: Hash table
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* @key: Key to compare against
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*/
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struct rhashtable_compare_arg {
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struct rhashtable *ht;
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const void *key;
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};
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typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
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typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 seed);
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typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg,
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const void *obj);
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struct rhashtable;
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/**
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* struct rhashtable_params - Hash table construction parameters
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* @nelem_hint: Hint on number of elements, should be 75% of desired size
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* @key_len: Length of key
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* @key_offset: Offset of key in struct to be hashed
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* @head_offset: Offset of rhash_head in struct to be hashed
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* @max_size: Maximum size while expanding
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* @min_size: Minimum size while shrinking
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* @nulls_base: Base value to generate nulls marker
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* @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
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* @hashfn: Function to hash key
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* @obj_hashfn: Function to hash object
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* @obj_cmpfn: Function to compare key with object
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*/
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struct rhashtable_params {
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size_t nelem_hint;
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size_t key_len;
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size_t key_offset;
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size_t head_offset;
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unsigned int max_size;
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unsigned int min_size;
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u32 nulls_base;
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size_t locks_mul;
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rht_hashfn_t hashfn;
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rht_obj_hashfn_t obj_hashfn;
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rht_obj_cmpfn_t obj_cmpfn;
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};
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/**
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* struct rhashtable - Hash table handle
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* @tbl: Bucket table
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* @nelems: Number of elements in table
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* @p: Configuration parameters
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* @run_work: Deferred worker to expand/shrink asynchronously
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* @mutex: Mutex to protect current/future table swapping
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* @being_destroyed: True if table is set up for destruction
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*/
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struct rhashtable {
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struct bucket_table __rcu *tbl;
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atomic_t nelems;
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bool being_destroyed;
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struct rhashtable_params p;
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struct work_struct run_work;
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struct mutex mutex;
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};
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/**
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* struct rhashtable_walker - Hash table walker
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* @list: List entry on list of walkers
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* @tbl: The table that we were walking over
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*/
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struct rhashtable_walker {
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struct list_head list;
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struct bucket_table *tbl;
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};
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/**
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* struct rhashtable_iter - Hash table iterator, fits into netlink cb
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* @ht: Table to iterate through
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* @p: Current pointer
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* @walker: Associated rhashtable walker
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* @slot: Current slot
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* @skip: Number of entries to skip in slot
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*/
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struct rhashtable_iter {
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struct rhashtable *ht;
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struct rhash_head *p;
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struct rhashtable_walker *walker;
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unsigned int slot;
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unsigned int skip;
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};
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static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
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{
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return NULLS_MARKER(ht->p.nulls_base + hash);
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}
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#define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
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((ptr) = (typeof(ptr)) rht_marker(ht, hash))
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static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
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{
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return ((unsigned long) ptr & 1);
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}
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static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
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{
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return ((unsigned long) ptr) >> 1;
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}
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static inline void *rht_obj(const struct rhashtable *ht,
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const struct rhash_head *he)
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{
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return (char *)he - ht->p.head_offset;
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}
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static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
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unsigned int hash)
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{
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return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1);
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}
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static inline unsigned int rht_key_hashfn(
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struct rhashtable *ht, const struct bucket_table *tbl,
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const void *key, const struct rhashtable_params params)
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{
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return rht_bucket_index(tbl, params.hashfn(key, params.key_len ?:
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ht->p.key_len,
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tbl->hash_rnd));
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}
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static inline unsigned int rht_head_hashfn(
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struct rhashtable *ht, const struct bucket_table *tbl,
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const struct rhash_head *he, const struct rhashtable_params params)
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{
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const char *ptr = rht_obj(ht, he);
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return likely(params.obj_hashfn) ?
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rht_bucket_index(tbl, params.obj_hashfn(ptr, tbl->hash_rnd)) :
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rht_key_hashfn(ht, tbl, ptr + params.key_offset, params);
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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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* @tbl: current table
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*/
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static inline bool rht_grow_above_75(const struct rhashtable *ht,
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const struct bucket_table *tbl)
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{
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/* Expand table when exceeding 75% load */
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return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
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(!ht->p.max_size || tbl->size < ht->p.max_size);
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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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* @tbl: current table
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*/
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static inline bool rht_shrink_below_30(const struct rhashtable *ht,
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const struct bucket_table *tbl)
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{
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/* Shrink table beneath 30% load */
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return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
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tbl->size > ht->p.min_size;
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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 inline spinlock_t *rht_bucket_lock(const struct bucket_table *tbl,
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unsigned int hash)
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{
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return &tbl->locks[hash & tbl->locks_mask];
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}
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#ifdef CONFIG_PROVE_LOCKING
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int lockdep_rht_mutex_is_held(struct rhashtable *ht);
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int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
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#else
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static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
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{
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return 1;
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}
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static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
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u32 hash)
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{
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return 1;
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}
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#endif /* CONFIG_PROVE_LOCKING */
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int rhashtable_init(struct rhashtable *ht,
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const struct rhashtable_params *params);
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int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
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struct rhash_head *obj,
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struct bucket_table *old_tbl);
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void rhashtable_insert(struct rhashtable *ht, struct rhash_head *node);
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bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *node);
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int rhashtable_expand(struct rhashtable *ht);
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int rhashtable_shrink(struct rhashtable *ht);
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void *rhashtable_lookup(struct rhashtable *ht, const void *key);
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void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
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bool (*compare)(void *, void *), void *arg);
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bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
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bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
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struct rhash_head *obj,
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bool (*compare)(void *, void *),
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void *arg);
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int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
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void rhashtable_walk_exit(struct rhashtable_iter *iter);
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int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
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void *rhashtable_walk_next(struct rhashtable_iter *iter);
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void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
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void rhashtable_destroy(struct rhashtable *ht);
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#define rht_dereference(p, ht) \
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rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
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#define rht_dereference_rcu(p, ht) \
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rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
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#define rht_dereference_bucket(p, tbl, hash) \
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rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
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#define rht_dereference_bucket_rcu(p, tbl, hash) \
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rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
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#define rht_entry(tpos, pos, member) \
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({ tpos = container_of(pos, typeof(*tpos), member); 1; })
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/**
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* rht_for_each_continue - continue iterating over hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*/
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#define rht_for_each_continue(pos, head, tbl, hash) \
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for (pos = rht_dereference_bucket(head, tbl, hash); \
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!rht_is_a_nulls(pos); \
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pos = rht_dereference_bucket((pos)->next, tbl, hash))
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/**
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* rht_for_each - iterate over hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*/
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#define rht_for_each(pos, tbl, hash) \
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rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
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/**
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* rht_for_each_entry_continue - continue iterating over hash chain
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*/
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#define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
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for (pos = rht_dereference_bucket(head, tbl, hash); \
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(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
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pos = rht_dereference_bucket((pos)->next, tbl, hash))
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/**
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* rht_for_each_entry - iterate over hash chain of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*/
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#define rht_for_each_entry(tpos, pos, tbl, hash, member) \
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rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
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tbl, hash, member)
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/**
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* rht_for_each_entry_safe - safely iterate over hash chain of given type
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @next: the &struct rhash_head to use as next in loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*
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* This hash chain list-traversal primitive allows for the looped code to
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* remove the loop cursor from the list.
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*/
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#define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
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for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
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next = !rht_is_a_nulls(pos) ? \
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rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
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(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
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pos = next, \
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next = !rht_is_a_nulls(pos) ? \
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rht_dereference_bucket(pos->next, tbl, hash) : NULL)
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/**
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* rht_for_each_rcu_continue - continue iterating over rcu hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_rcu_continue(pos, head, tbl, hash) \
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for (({barrier(); }), \
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pos = rht_dereference_bucket_rcu(head, tbl, hash); \
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!rht_is_a_nulls(pos); \
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pos = rcu_dereference_raw(pos->next))
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/**
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* rht_for_each_rcu - iterate over rcu hash chain
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_rcu(pos, tbl, hash) \
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rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
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/**
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* rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
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* @tpos: the type * to use as a loop cursor.
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* @pos: the &struct rhash_head to use as a loop cursor.
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* @head: the previous &struct rhash_head to continue from
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* @tbl: the &struct bucket_table
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* @hash: the hash value / bucket index
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* @member: name of the &struct rhash_head within the hashable struct.
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*
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* This hash chain list-traversal primitive may safely run concurrently with
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* the _rcu mutation primitives such as rhashtable_insert() as long as the
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* traversal is guarded by rcu_read_lock().
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*/
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#define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
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for (({barrier(); }), \
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pos = rht_dereference_bucket_rcu(head, tbl, hash); \
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(!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
|
|
pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
|
|
|
|
/**
|
|
* rht_for_each_entry_rcu - iterate over rcu hash chain of given type
|
|
* @tpos: the type * to use as a loop cursor.
|
|
* @pos: the &struct rhash_head to use as a loop cursor.
|
|
* @tbl: the &struct bucket_table
|
|
* @hash: the hash value / bucket index
|
|
* @member: name of the &struct rhash_head within the hashable struct.
|
|
*
|
|
* This hash chain list-traversal primitive may safely run concurrently with
|
|
* 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(tpos, pos, tbl, hash, member) \
|
|
rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
|
|
tbl, hash, member)
|
|
|
|
static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
|
|
const void *obj)
|
|
{
|
|
struct rhashtable *ht = arg->ht;
|
|
const char *ptr = obj;
|
|
|
|
return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_lookup_fast - search hash table, inlined version
|
|
* @ht: hash table
|
|
* @key: the pointer to the key
|
|
* @params: hash table parameters
|
|
*
|
|
* 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.
|
|
*
|
|
* Returns the first entry on which the compare function returned true.
|
|
*/
|
|
static inline void *rhashtable_lookup_fast(
|
|
struct rhashtable *ht, const void *key,
|
|
const struct rhashtable_params params)
|
|
{
|
|
struct rhashtable_compare_arg arg = {
|
|
.ht = ht,
|
|
.key = key,
|
|
};
|
|
const struct bucket_table *tbl;
|
|
struct rhash_head *he;
|
|
unsigned hash;
|
|
|
|
rcu_read_lock();
|
|
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
restart:
|
|
hash = rht_key_hashfn(ht, tbl, key, params);
|
|
rht_for_each_rcu(he, tbl, hash) {
|
|
if (params.obj_cmpfn ?
|
|
params.obj_cmpfn(&arg, rht_obj(ht, he)) :
|
|
rhashtable_compare(&arg, rht_obj(ht, he)))
|
|
continue;
|
|
rcu_read_unlock();
|
|
return rht_obj(ht, he);
|
|
}
|
|
|
|
/* Ensure we see any new tables. */
|
|
smp_rmb();
|
|
|
|
tbl = rht_dereference_rcu(tbl->future_tbl, ht);
|
|
if (unlikely(tbl))
|
|
goto restart;
|
|
rcu_read_unlock();
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static inline int __rhashtable_insert_fast(
|
|
struct rhashtable *ht, const void *key, struct rhash_head *obj,
|
|
const struct rhashtable_params params)
|
|
{
|
|
struct rhashtable_compare_arg arg = {
|
|
.ht = ht,
|
|
.key = key,
|
|
};
|
|
int err = -EEXIST;
|
|
struct bucket_table *tbl, *new_tbl;
|
|
struct rhash_head *head;
|
|
spinlock_t *lock;
|
|
unsigned hash;
|
|
|
|
rcu_read_lock();
|
|
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
hash = rht_head_hashfn(ht, tbl, obj, params);
|
|
lock = rht_bucket_lock(tbl, hash);
|
|
|
|
spin_lock_bh(lock);
|
|
|
|
/* Because we have already taken the bucket lock in tbl,
|
|
* if we find that future_tbl is not yet visible then
|
|
* that guarantees all other insertions of the same entry
|
|
* will also grab the bucket lock in tbl because until
|
|
* the rehash completes ht->tbl won't be changed.
|
|
*/
|
|
new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
|
|
if (unlikely(new_tbl)) {
|
|
err = rhashtable_insert_slow(ht, key, obj, new_tbl);
|
|
goto out;
|
|
}
|
|
|
|
if (!key)
|
|
goto skip_lookup;
|
|
|
|
rht_for_each(head, tbl, hash) {
|
|
if (unlikely(!(params.obj_cmpfn ?
|
|
params.obj_cmpfn(&arg, rht_obj(ht, head)) :
|
|
rhashtable_compare(&arg, rht_obj(ht, head)))))
|
|
goto out;
|
|
}
|
|
|
|
skip_lookup:
|
|
err = 0;
|
|
|
|
head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
|
|
|
|
RCU_INIT_POINTER(obj->next, head);
|
|
|
|
rcu_assign_pointer(tbl->buckets[hash], obj);
|
|
|
|
atomic_inc(&ht->nelems);
|
|
if (rht_grow_above_75(ht, tbl))
|
|
schedule_work(&ht->run_work);
|
|
|
|
out:
|
|
spin_unlock_bh(lock);
|
|
rcu_read_unlock();
|
|
|
|
return err;
|
|
}
|
|
|
|
/**
|
|
* rhashtable_insert_fast - insert object into hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
* @params: hash table parameters
|
|
*
|
|
* 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().
|
|
*/
|
|
static inline int rhashtable_insert_fast(
|
|
struct rhashtable *ht, struct rhash_head *obj,
|
|
const struct rhashtable_params params)
|
|
{
|
|
return __rhashtable_insert_fast(ht, NULL, obj, params);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_lookup_insert_fast - lookup and insert object into hash table
|
|
* @ht: hash table
|
|
* @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.
|
|
*
|
|
* 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().
|
|
*/
|
|
static inline int rhashtable_lookup_insert_fast(
|
|
struct rhashtable *ht, struct rhash_head *obj,
|
|
const struct rhashtable_params params)
|
|
{
|
|
const char *key = rht_obj(ht, obj);
|
|
|
|
BUG_ON(ht->p.obj_hashfn);
|
|
|
|
return __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj,
|
|
params);
|
|
}
|
|
|
|
/**
|
|
* rhashtable_lookup_insert_key - search and insert object to hash table
|
|
* with explicit key
|
|
* @ht: hash table
|
|
* @key: key
|
|
* @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 the size grows
|
|
* beyond the watermark indicated by grow_decision() which can be passed
|
|
* to rhashtable_init().
|
|
*
|
|
* Returns zero on success.
|
|
*/
|
|
static inline int rhashtable_lookup_insert_key(
|
|
struct rhashtable *ht, const void *key, struct rhash_head *obj,
|
|
const struct rhashtable_params params)
|
|
{
|
|
BUG_ON(!ht->p.obj_hashfn || !key);
|
|
|
|
return __rhashtable_insert_fast(ht, key, obj, params);
|
|
}
|
|
|
|
static inline int __rhashtable_remove_fast(
|
|
struct rhashtable *ht, struct bucket_table *tbl,
|
|
struct rhash_head *obj, const struct rhashtable_params params)
|
|
{
|
|
struct rhash_head __rcu **pprev;
|
|
struct rhash_head *he;
|
|
spinlock_t * lock;
|
|
unsigned hash;
|
|
int err = -ENOENT;
|
|
|
|
hash = rht_head_hashfn(ht, tbl, obj, params);
|
|
lock = rht_bucket_lock(tbl, hash);
|
|
|
|
spin_lock_bh(lock);
|
|
|
|
pprev = &tbl->buckets[hash];
|
|
rht_for_each(he, tbl, hash) {
|
|
if (he != obj) {
|
|
pprev = &he->next;
|
|
continue;
|
|
}
|
|
|
|
rcu_assign_pointer(*pprev, obj->next);
|
|
err = 0;
|
|
break;
|
|
}
|
|
|
|
spin_unlock_bh(lock);
|
|
|
|
return err;
|
|
}
|
|
|
|
/**
|
|
* rhashtable_remove_fast - remove object from hash table
|
|
* @ht: hash table
|
|
* @obj: pointer to hash head inside object
|
|
* @params: hash table parameters
|
|
*
|
|
* 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.
|
|
*
|
|
* Returns zero on success, -ENOENT if the entry could not be found.
|
|
*/
|
|
static inline int rhashtable_remove_fast(
|
|
struct rhashtable *ht, struct rhash_head *obj,
|
|
const struct rhashtable_params params)
|
|
{
|
|
struct bucket_table *tbl;
|
|
int err;
|
|
|
|
rcu_read_lock();
|
|
|
|
tbl = rht_dereference_rcu(ht->tbl, ht);
|
|
|
|
/* Because we have already taken (and released) the bucket
|
|
* lock in old_tbl, if we find that future_tbl is not yet
|
|
* visible then that guarantees the entry to still be in
|
|
* the old tbl if it exists.
|
|
*/
|
|
while ((err = __rhashtable_remove_fast(ht, tbl, obj, params)) &&
|
|
(tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
|
|
;
|
|
|
|
if (err)
|
|
goto out;
|
|
|
|
atomic_dec(&ht->nelems);
|
|
if (rht_shrink_below_30(ht, tbl))
|
|
schedule_work(&ht->run_work);
|
|
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return err;
|
|
}
|
|
|
|
#endif /* _LINUX_RHASHTABLE_H */
|