// SPDX-License-Identifier: GPL-2.0-only/* * Resizable, Scalable, Concurrent Hash Table * * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch> * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net> * * Code partially derived from nft_hash * Rewritten with rehash code from br_multicast plus single list * pointer as suggested by Josh Triplett */ #include <linux/atomic.h>#include <linux/kernel.h>#include <linux/init.h>#include <linux/log2.h>#include <linux/sched.h>#include <linux/rculist.h>#include <linux/slab.h>#include <linux/vmalloc.h>#include <linux/mm.h>#include <linux/jhash.h>#include <linux/random.h>#include <linux/rhashtable.h>#include <linux/err.h>#include <linux/export.h> #define HASH_DEFAULT_SIZE 64UL#define HASH_MIN_SIZE 4U union nested_table { union nested_table __rcu *table; struct rhash_lock_head *bucket;}; static u32 head_hashfn(struct rhashtable *ht, const struct bucket_table *tbl, const struct rhash_head *he){ return rht_head_hashfn(ht, tbl, he, ht->p);} #ifdef CONFIG_PROVE_LOCKING#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT)) int lockdep_rht_mutex_is_held(struct rhashtable *ht){ 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){ if (!debug_locks) return 1; if (unlikely(tbl->nest)) return 1; return bit_spin_is_locked(0, (unsigned long *)&tbl->buckets[hash]);}EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);#else#define ASSERT_RHT_MUTEX(HT)#endif static void nested_table_free(union nested_table *ntbl, unsigned int size){ const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *)); const unsigned int len = 1 << shift; unsigned int i; ntbl = rcu_dereference_raw(ntbl->table); if (!ntbl) return; if (size > len) { size >>= shift; for (i = 0; i < len; i++) nested_table_free(ntbl + i, size); } kfree(ntbl);} static void nested_bucket_table_free(const struct bucket_table *tbl){ unsigned int size = tbl->size >> tbl->nest; unsigned int len = 1 << tbl->nest; union nested_table *ntbl; unsigned int i; ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]); for (i = 0; i < len; i++) nested_table_free(ntbl + i, size); kfree(ntbl);} static void bucket_table_free(const struct bucket_table *tbl){ if (tbl->nest) nested_bucket_table_free(tbl); kvfree(tbl);} static void bucket_table_free_rcu(struct rcu_head *head){ bucket_table_free(container_of(head, struct bucket_table, rcu));} static union nested_table *nested_table_alloc(struct rhashtable *ht, union nested_table __rcu **prev, bool leaf){ union nested_table *ntbl; int i; ntbl = rcu_dereference(*prev); if (ntbl) return ntbl; ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC); if (ntbl && leaf) { for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++) INIT_RHT_NULLS_HEAD(ntbl[i].bucket); } if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL) return ntbl; /* Raced with another thread. */ kfree(ntbl); return rcu_dereference(*prev);} static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht, size_t nbuckets, gfp_t gfp){ const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *)); struct bucket_table *tbl; size_t size; if (nbuckets < (1 << (shift + 1))) return NULL; size = sizeof(*tbl) + sizeof(tbl->buckets[0]); tbl = kzalloc(size, gfp); if (!tbl) return NULL; if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets, false)) { kfree(tbl); return NULL; } tbl->nest = (ilog2(nbuckets) - 1) % shift + 1; return tbl;} static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, size_t nbuckets, gfp_t gfp){ struct bucket_table *tbl = NULL; size_t size; int i; static struct lock_class_key __key; tbl = kvzalloc(struct_size(tbl, buckets, nbuckets), gfp); size = nbuckets; if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) { tbl = nested_bucket_table_alloc(ht, nbuckets, gfp); nbuckets = 0; } if (tbl == NULL) return NULL; lockdep_init_map(&tbl->dep_map, "rhashtable_bucket", &__key, 0); tbl->size = size; rcu_head_init(&tbl->rcu); INIT_LIST_HEAD(&tbl->walkers); tbl->hash_rnd = get_random_u32(); for (i = 0; i < nbuckets; i++) INIT_RHT_NULLS_HEAD(tbl->buckets[i]); return tbl;} static struct bucket_table *rhashtable_last_table(struct rhashtable *ht, struct bucket_table *tbl){ struct bucket_table *new_tbl; do { new_tbl = tbl; tbl = rht_dereference_rcu(tbl->future_tbl, ht); } while (tbl); return new_tbl;} static int rhashtable_rehash_one(struct rhashtable *ht, struct rhash_lock_head **bkt, unsigned int old_hash){ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl); int err = -EAGAIN; struct rhash_head *head, *next, *entry; struct rhash_head __rcu **pprev = NULL; unsigned int new_hash; if (new_tbl->nest) goto out; err = -ENOENT; rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash), old_tbl, old_hash) { err = 0; next = rht_dereference_bucket(entry->next, old_tbl, old_hash); if (rht_is_a_nulls(next)) break; pprev = &entry->next; } if (err) goto out; new_hash = head_hashfn(ht, new_tbl, entry); rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash], SINGLE_DEPTH_NESTING); head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash); RCU_INIT_POINTER(entry->next, head); rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry); if (pprev) rcu_assign_pointer(*pprev, next); else /* Need to preserved the bit lock. */ rht_assign_locked(bkt, next); out: return err;} static int rhashtable_rehash_chain(struct rhashtable *ht, unsigned int old_hash){ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); struct rhash_lock_head **bkt = rht_bucket_var(old_tbl, old_hash); int err; if (!bkt) return 0; rht_lock(old_tbl, bkt); while (!(err = rhashtable_rehash_one(ht, bkt, old_hash))) ; if (err == -ENOENT) err = 0; rht_unlock(old_tbl, bkt); return err;} static int rhashtable_rehash_attach(struct rhashtable *ht, struct bucket_table *old_tbl, struct bucket_table *new_tbl){ /* Make insertions go into the new, empty table right away. Deletions * and lookups will be attempted in both tables until we synchronize. * As cmpxchg() provides strong barriers, we do not need * rcu_assign_pointer(). */ if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL, new_tbl) != NULL) return -EEXIST; return 0;} static int rhashtable_rehash_table(struct rhashtable *ht){ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); struct bucket_table *new_tbl; struct rhashtable_walker *walker; unsigned int old_hash; int err; new_tbl = rht_dereference(old_tbl->future_tbl, ht); if (!new_tbl) return 0; for (old_hash = 0; old_hash < old_tbl->size; old_hash++) { err = rhashtable_rehash_chain(ht, old_hash); if (err) return err; cond_resched(); } /* Publish the new table pointer. */ rcu_assign_pointer(ht->tbl, new_tbl); spin_lock(&ht->lock); list_for_each_entry(walker, &old_tbl->walkers, list) walker->tbl = NULL; /* 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;} static int rhashtable_rehash_alloc(struct rhashtable *ht, struct bucket_table *old_tbl, unsigned int size){ struct bucket_table *new_tbl; int err; ASSERT_RHT_MUTEX(ht); new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL); if (new_tbl == NULL) return -ENOMEM; err = rhashtable_rehash_attach(ht, old_tbl, new_tbl); if (err) bucket_table_free(new_tbl); return err;} /** * rhashtable_shrink - Shrink hash table while allowing concurrent lookups * @ht: the hash table to shrink * * This function shrinks the hash table to fit, i.e., the smallest * size would not cause it to expand right away automatically. * * 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. */static int rhashtable_shrink(struct rhashtable *ht){ struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); unsigned int nelems = atomic_read(&ht->nelems); unsigned int size = 0; if (nelems) size = roundup_pow_of_two(nelems * 3 / 2); if (size < ht->p.min_size) size = ht->p.min_size; if (old_tbl->size <= size) return 0; if (rht_dereference(old_tbl->future_tbl, ht)) return -EEXIST; return rhashtable_rehash_alloc(ht, old_tbl, size);} static void rht_deferred_worker(struct work_struct *work){ struct rhashtable *ht; struct bucket_table *tbl; int err = 0; ht = container_of(work, struct rhashtable, run_work); mutex_lock(&ht->mutex); tbl = rht_dereference(ht->tbl, ht); tbl = rhashtable_last_table(ht, tbl); if (rht_grow_above_75(ht, tbl)) err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2); else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl)) err = rhashtable_shrink(ht); else if (tbl->nest) err = rhashtable_rehash_alloc(ht, tbl, tbl->size); if (!err || err == -EEXIST) { int nerr; nerr = rhashtable_rehash_table(ht); err = err ?: nerr; } mutex_unlock(&ht->mutex); if (err) schedule_work(&ht->run_work);} static int rhashtable_insert_rehash(struct rhashtable *ht, struct bucket_table *tbl){ struct bucket_table *old_tbl; struct bucket_table *new_tbl; unsigned int size; int err; old_tbl = rht_dereference_rcu(ht->tbl, ht); size = tbl->size; err = -EBUSY; if (rht_grow_above_75(ht, tbl)) size *= 2; /* Do not schedule more than one rehash */ else if (old_tbl != tbl) goto fail; err = -ENOMEM; new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN); if (new_tbl == NULL) goto fail; err = rhashtable_rehash_attach(ht, tbl, new_tbl); if (err) { bucket_table_free(new_tbl); if (err == -EEXIST) err = 0; } else schedule_work(&ht->run_work); return err; fail: /* Do not fail the insert if someone else did a rehash. */ if (likely(rcu_access_pointer(tbl->future_tbl))) return 0; /* Schedule async rehash to retry allocation in process context. */ if (err == -ENOMEM) schedule_work(&ht->run_work); return err;} static void *rhashtable_lookup_one(struct rhashtable *ht, struct rhash_lock_head **bkt, 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 = NULL; struct rhash_head *head; int elasticity; elasticity = RHT_ELASTICITY; rht_for_each_from(head, rht_ptr(bkt, tbl, hash), 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)))) {Lines 1–500 of 1235. 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// SPDX-License-Identifier: GPL-2.0-only /* * Resizable, Scalable, Concurrent Hash Table * * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch> * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net> * * Code partially derived from nft_hash * Rewritten with rehash code from br_multicast plus single list * pointer as suggested by Josh Triplett */ #include <linux/atomic.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/log2.h> #include <linux/sched.h> #include <linux/rculist.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/mm.h> #include <linux/jhash.h> #include <linux/random.h> #include <linux/rhashtable.h> #include <linux/err.h> #include <linux/export.h> #define HASH_DEFAULT_SIZE 64UL #define HASH_MIN_SIZE 4U union nested_table { union nested_table __rcu *table; struct rhash_lock_head *bucket; }; static u32 head_hashfn(struct rhashtable *ht, const struct bucket_table *tbl, const struct rhash_head *he) { return rht_head_hashfn(ht, tbl, he, ht->p); } #ifdef CONFIG_PROVE_LOCKING #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT)) int lockdep_rht_mutex_is_held(struct rhashtable *ht) { 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) { if (!debug_locks) return 1; if (unlikely(tbl->nest)) return 1; return bit_spin_is_locked(0, (unsigned long *)&tbl->buckets[hash]); } EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held); #else #define ASSERT_RHT_MUTEX(HT) #endif static void nested_table_free(union nested_table *ntbl, unsigned int size) { const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *)); const unsigned int len = 1 << shift; unsigned int i; ntbl = rcu_dereference_raw(ntbl->table); if (!ntbl) return; if (size > len) { size >>= shift; for (i = 0; i < len; i++) nested_table_free(ntbl + i, size); } kfree(ntbl); } static void nested_bucket_table_free(const struct bucket_table *tbl) { unsigned int size = tbl->size >> tbl->nest; unsigned int len = 1 << tbl->nest; union nested_table *ntbl; unsigned int i; ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]); for (i = 0; i < len; i++) nested_table_free(ntbl + i, size); kfree(ntbl); } static void bucket_table_free(const struct bucket_table *tbl) { if (tbl->nest) nested_bucket_table_free(tbl); kvfree(tbl); } static void bucket_table_free_rcu(struct rcu_head *head) { bucket_table_free(container_of(head, struct bucket_table, rcu)); } static union nested_table *nested_table_alloc(struct rhashtable *ht, union nested_table __rcu **prev, bool leaf) { union nested_table *ntbl; int i; ntbl = rcu_dereference(*prev); if (ntbl) return ntbl; ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC); if (ntbl && leaf) { for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++) INIT_RHT_NULLS_HEAD(ntbl[i].bucket); } if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL) return ntbl; /* Raced with another thread. */ kfree(ntbl); return rcu_dereference(*prev); } static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht, size_t nbuckets, gfp_t gfp) { const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *)); struct bucket_table *tbl; size_t size; if (nbuckets < (1 << (shift + 1))) return NULL; size = sizeof(*tbl) + sizeof(tbl->buckets[0]); tbl = kzalloc(size, gfp); if (!tbl) return NULL; if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets, false)) { kfree(tbl); return NULL; } tbl->nest = (ilog2(nbuckets) - 1) % shift + 1; return tbl; } static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, size_t nbuckets, gfp_t gfp) { struct bucket_table *tbl = NULL; size_t size; int i; static struct lock_class_key __key; tbl = kvzalloc(struct_size(tbl, buckets, nbuckets), gfp); size = nbuckets; if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) { tbl = nested_bucket_table_alloc(ht, nbuckets, gfp); nbuckets = 0; } if (tbl == NULL) return NULL; lockdep_init_map(&tbl->dep_map, "rhashtable_bucket", &__key, 0); tbl->size = size; rcu_head_init(&tbl->rcu); INIT_LIST_HEAD(&tbl->walkers); tbl->hash_rnd = get_random_u32(); for (i = 0; i < nbuckets; i++) INIT_RHT_NULLS_HEAD(tbl->buckets[i]); return tbl; } static struct bucket_table *rhashtable_last_table(struct rhashtable *ht, struct bucket_table *tbl) { struct bucket_table *new_tbl; do { new_tbl = tbl; tbl = rht_dereference_rcu(tbl->future_tbl, ht); } while (tbl); return new_tbl; } static int rhashtable_rehash_one(struct rhashtable *ht, struct rhash_lock_head **bkt, unsigned int old_hash) { struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl); int err = -EAGAIN; struct rhash_head *head, *next, *entry; struct rhash_head __rcu **pprev = NULL; unsigned int new_hash; if (new_tbl->nest) goto out; err = -ENOENT; rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash), old_tbl, old_hash) { err = 0; next = rht_dereference_bucket(entry->next, old_tbl, old_hash); if (rht_is_a_nulls(next)) break; pprev = &entry->next; } if (err) goto out; new_hash = head_hashfn(ht, new_tbl, entry); rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash], SINGLE_DEPTH_NESTING); head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash); RCU_INIT_POINTER(entry->next, head); rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry); if (pprev) rcu_assign_pointer(*pprev, next); else /* Need to preserved the bit lock. */ rht_assign_locked(bkt, next); out: return err; } static int rhashtable_rehash_chain(struct rhashtable *ht, unsigned int old_hash) { struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); struct rhash_lock_head **bkt = rht_bucket_var(old_tbl, old_hash); int err; if (!bkt) return 0; rht_lock(old_tbl, bkt); while (!(err = rhashtable_rehash_one(ht, bkt, old_hash))) ; if (err == -ENOENT) err = 0; rht_unlock(old_tbl, bkt); return err; } static int rhashtable_rehash_attach(struct rhashtable *ht, struct bucket_table *old_tbl, struct bucket_table *new_tbl) { /* Make insertions go into the new, empty table right away. Deletions * and lookups will be attempted in both tables until we synchronize. * As cmpxchg() provides strong barriers, we do not need * rcu_assign_pointer(). */ if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL, new_tbl) != NULL) return -EEXIST; return 0; } static int rhashtable_rehash_table(struct rhashtable *ht) { struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); struct bucket_table *new_tbl; struct rhashtable_walker *walker; unsigned int old_hash; int err; new_tbl = rht_dereference(old_tbl->future_tbl, ht); if (!new_tbl) return 0; for (old_hash = 0; old_hash < old_tbl->size; old_hash++) { err = rhashtable_rehash_chain(ht, old_hash); if (err) return err; cond_resched(); } /* Publish the new table pointer. */ rcu_assign_pointer(ht->tbl, new_tbl); spin_lock(&ht->lock); list_for_each_entry(walker, &old_tbl->walkers, list) walker->tbl = NULL; /* 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; } static int rhashtable_rehash_alloc(struct rhashtable *ht, struct bucket_table *old_tbl, unsigned int size) { struct bucket_table *new_tbl; int err; ASSERT_RHT_MUTEX(ht); new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL); if (new_tbl == NULL) return -ENOMEM; err = rhashtable_rehash_attach(ht, old_tbl, new_tbl); if (err) bucket_table_free(new_tbl); return err; } /** * rhashtable_shrink - Shrink hash table while allowing concurrent lookups * @ht: the hash table to shrink * * This function shrinks the hash table to fit, i.e., the smallest * size would not cause it to expand right away automatically. * * 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. */ static int rhashtable_shrink(struct rhashtable *ht) { struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht); unsigned int nelems = atomic_read(&ht->nelems); unsigned int size = 0; if (nelems) size = roundup_pow_of_two(nelems * 3 / 2); if (size < ht->p.min_size) size = ht->p.min_size; if (old_tbl->size <= size) return 0; if (rht_dereference(old_tbl->future_tbl, ht)) return -EEXIST; return rhashtable_rehash_alloc(ht, old_tbl, size); } static void rht_deferred_worker(struct work_struct *work) { struct rhashtable *ht; struct bucket_table *tbl; int err = 0; ht = container_of(work, struct rhashtable, run_work); mutex_lock(&ht->mutex); tbl = rht_dereference(ht->tbl, ht); tbl = rhashtable_last_table(ht, tbl); if (rht_grow_above_75(ht, tbl)) err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2); else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl)) err = rhashtable_shrink(ht); else if (tbl->nest) err = rhashtable_rehash_alloc(ht, tbl, tbl->size); if (!err || err == -EEXIST) { int nerr; nerr = rhashtable_rehash_table(ht); err = err ?: nerr; } mutex_unlock(&ht->mutex); if (err) schedule_work(&ht->run_work); } static int rhashtable_insert_rehash(struct rhashtable *ht, struct bucket_table *tbl) { struct bucket_table *old_tbl; struct bucket_table *new_tbl; unsigned int size; int err; old_tbl = rht_dereference_rcu(ht->tbl, ht); size = tbl->size; err = -EBUSY; if (rht_grow_above_75(ht, tbl)) size *= 2; /* Do not schedule more than one rehash */ else if (old_tbl != tbl) goto fail; err = -ENOMEM; new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN); if (new_tbl == NULL) goto fail; err = rhashtable_rehash_attach(ht, tbl, new_tbl); if (err) { bucket_table_free(new_tbl); if (err == -EEXIST) err = 0; } else schedule_work(&ht->run_work); return err; fail: /* Do not fail the insert if someone else did a rehash. */ if (likely(rcu_access_pointer(tbl->future_tbl))) return 0; /* Schedule async rehash to retry allocation in process context. */ if (err == -ENOMEM) schedule_work(&ht->run_work); return err; } static void *rhashtable_lookup_one(struct rhashtable *ht, struct rhash_lock_head **bkt, 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 = NULL; struct rhash_head *head; int elasticity; elasticity = RHT_ELASTICITY; rht_for_each_from(head, rht_ptr(bkt, tbl, hash), 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)))) {