Am 26.08.2017 um 09:19 schrieb Felix Kuehling:
> This adds a closed hash table implementation with low memory and CPU
> overhead. The API is inspired by kfifo.
>
> Storing, retrieving and deleting data does not involve any dynamic
> memory management, which makes it ideal for use in interrupt context.
> Memory overhead per entry is the 32 or 64 bit hash key, two bits for
> free/used tracking and whatever value size is stored in the table.
> No list heads or pointers, therefore this data structure should be
> quite cache-friendly, too.
>
> After entries are removed, free space maintenance is necessary. At
> the same time, entries that had hash collisions on insertion can be
> relocated to speed up future lookups. This is done incrementally and
> opportunistically to avoid long stalls.
>
> CPU overhead is very small as long as the table doesn't fill up more
> than about 50%. It's still quite efficient up to 90% full. The less
> free space is in the table, the more likely collisions get, and the
> more maintenance overhead is required to maintain free space and
> efficiency.
>
> Change-Id: I86e72510941969e7523df11f9e68926f46ef7af1
> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
Acked-by: Christian König <christian.koenig at amd.com>
Please also send to the LKML cause that really needs a wider audience.
Regards,
Christian.
> ---
> include/linux/chash.h | 349 +++++++++++++++++++++++++++++++++
> lib/Kconfig | 8 +
> lib/Makefile | 2 +
> lib/chash.c | 521 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 880 insertions(+)
> create mode 100644 include/linux/chash.h
> create mode 100644 lib/chash.c
>
> diff --git a/include/linux/chash.h b/include/linux/chash.h
> new file mode 100644
> index 0000000..3835575
> --- /dev/null
> +++ b/include/linux/chash.h
> @@ -0,0 +1,349 @@
> +/*
> + * Copyright 2017 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + */
> +
> +#ifndef _LINUX_CHASH_H
> +#define _LINUX_CHASH_H
> +
> +#include <linux/types.h>
> +#include <linux/hash.h>
> +#include <linux/bug.h>
> +#include <linux/bitops.h>
> +
> +struct __chash_table {
> + u8 bits;
> + u8 key_size;
> + unsigned int value_size;
> + u32 size_mask;
> + unsigned long *occup_bitmap, *valid_bitmap;
> + union {
> + u32 *keys32;
> + u64 *keys64;
> + };
> + u8 *values;
> +
> +#define CHASH_STATS
> +#ifdef CHASH_STATS
> + u64 total_add_calls, total_add_steps;
> + u64 total_find_calls, total_find_steps;
> + u64 total_not_find_calls, total_not_find_steps;
> + u64 total_relocations, total_relocation_distance;
> +#endif
> +};
> +
> +#define __CHASH_BITMAP_SIZE(bits) \
> + (((1 << (bits)) + BITS_PER_LONG - 1) / BITS_PER_LONG)
> +#define __CHASH_ARRAY_SIZE(bits, size) \
> + ((((size) << (bits)) + sizeof(long) - 1) / sizeof(long))
> +
> +#define __CHASH_DATA_SIZE(bits, key_size, value_size) \
> + (__CHASH_BITMAP_SIZE(bits) * 2 + \
> + __CHASH_ARRAY_SIZE(bits, key_size) + \
> + __CHASH_ARRAY_SIZE(bits, value_size))
> +
> +#define STRUCT_CHASH_TABLE(bits, key_size, value_size) \
> + struct { \
> + struct __chash_table table; \
> + unsigned long data[ \
> + __CHASH_DATA_SIZE(bits, key_size, value_size)]; \
> + }
> +
> +/**
> + * struct chash_table - Dynamically allocated closed hash table
> + *
> + * Use this struct for dynamically allocated hash tables (using
> + * chash_table_alloc and chash_table_free), where the size is
> + * determined at runtime.
> + */
> +struct chash_table {
> + struct __chash_table table;
> + unsigned long *data;
> +};
> +
> +/**
> + * DECLARE_CHASH_TABLE - macro to declare a closed hash table
> + * @table: name of the declared hash table
> + * @bts: Table size will be 2^bits entries
> + * @key_sz: Size of hash keys in bytes, 4 or 8
> + * @val_sz: Size of data values in bytes, can be 0
> + *
> + * This declares the hash table variable with a static size.
> + *
> + * The closed hash table stores key-value pairs with low memory and
> + * lookup overhead. In operation it performs no dynamic memory
> + * management. The data being stored does not require any
> + * list_heads. The hash table performs best with small @val_sz and as
> + * long as some space (about 50%) is left free in the table. But the
> + * table can still work reasonably efficiently even when filled up to
> + * about 90%. If bigger data items need to be stored and looked up,
> + * store the pointer to it as value in the hash table.
> + *
> + * @val_sz may be 0. This can be useful when all the stored
> + * information is contained in the key itself and the fact that it is
> + * in the hash table (or not).
> + */
> +#define DECLARE_CHASH_TABLE(table, bts, key_sz, val_sz) \
> + STRUCT_CHASH_TABLE(bts, key_sz, val_sz) table
> +
> +#ifdef CHASH_STATS
> +#define __CHASH_STATS_INIT(prefix) , \
> + prefix.total_add_calls = 0, \
> + prefix.total_add_steps = 0, \
> + prefix.total_find_calls = 0, \
> + prefix.total_find_steps = 0, \
> + prefix.total_not_find_calls = 0, \
> + prefix.total_not_find_steps = 0, \
> + prefix.total_relocations = 0, \
> + prefix.total_relocation_distance = 0
> +#else
> +#define __CHASH_STATS_INIT(prefix)
> +#endif
> +
> +#define __CHASH_TABLE_INIT(prefix, data, bts, key_sz, val_sz) \
> + prefix.bits = (bts), \
> + prefix.key_size = (key_sz), \
> + prefix.value_size = (val_sz), \
> + prefix.size_mask = ((1 << bts) - 1), \
> + prefix.occup_bitmap = &data[0], \
> + prefix.valid_bitmap = &data[ \
> + __CHASH_BITMAP_SIZE(bts)], \
> + prefix.keys64 = (u64 *)&data[ \
> + __CHASH_BITMAP_SIZE(bts) * 2], \
> + prefix.values = (u8 *)&data[ \
> + __CHASH_BITMAP_SIZE(bts) * 2 + \
> + __CHASH_ARRAY_SIZE(bts, key_sz)] \
> + __CHASH_STATS_INIT(prefix)
> +
> +/**
> + * DEFINE_CHASH_TABLE - macro to define and initialize a closed hash table
> + * @tbl: name of the declared hash table
> + * @bts: Table size will be 2^bits entries
> + * @key_sz: Size of hash keys in bytes, 4 or 8
> + * @val_sz: Size of data values in bytes, can be 0
> + *
> + * Note: the macro can be used for global and local hash table variables.
> + */
> +#define DEFINE_CHASH_TABLE(tbl, bts, key_sz, val_sz) \
> + DECLARE_CHASH_TABLE(tbl, bts, key_sz, val_sz) = { \
> + .table = { \
> + __CHASH_TABLE_INIT(, (tbl).data, bts, key_sz, val_sz) \
> + }, \
> + .data = {0} \
> + }
> +
> +/**
> + * INIT_CHASH_TABLE - Initialize a hash table declared by DECLARE_CHASH_TABLE
> + * @tbl: name of the declared hash table
> + * @bts: Table size will be 2^bits entries
> + * @key_sz: Size of hash keys in bytes, 4 or 8
> + * @val_sz: Size of data values in bytes, can be 0
> + */
> +#define INIT_CHASH_TABLE(tbl, bts, key_sz, val_sz) \
> + __CHASH_TABLE_INIT(((tbl).table), (tbl).data, bts, key_sz, val_sz)
> +
> +int chash_table_alloc(struct chash_table *table, u8 bits, u8 key_size,
> + unsigned int value_size, gfp_t gfp_mask);
> +void chash_table_free(struct chash_table *table);
> +
> +/**
> + * chash_table_dump_stats - Dump statistics of a closed hash table
> + * @tbl: Pointer to the table structure
> + *
> + * Dumps some performance statistics of the table gathered in operation.
> + */
> +#ifdef CHASH_STATS
> +#define chash_table_dump_stats(tbl) __chash_table_dump_stats(&(*tbl).table)
> +
> +void __chash_table_dump_stats(struct __chash_table *table);
> +#else
> +#define chash_table_dump_stats(tbl)
> +#endif
> +
> +/**
> + * chash_table_copy_in - Copy a new value into the hash table
> + * @tbl: Pointer to the table structure
> + * @key: Key of the entry to add or update
> + * @value: Pointer to value to copy, may be NULL
> + *
> + * If @key already has an entry, its value is replaced. Otherwise a
> + * new entry is added. If @value is NULL, the value is left unchanged
> + * or uninitialized. Returns 1 if an entry already existed, 0 if a new
> + * entry was added or %-ENOMEM if there was no free space in the
> + * table.
> + */
> +#define chash_table_copy_in(tbl, key, value) \
> + __chash_table_copy_in(&(*tbl).table, key, value)
> +
> +int __chash_table_copy_in(struct __chash_table *table, u64 key,
> + const void *value);
> +
> +/**
> + * chash_table_copy_out - Copy a value out of the hash table
> + * @tbl: Pointer to the table structure
> + * @key: Key of the entry to find
> + * @value: Pointer to value to copy, may be NULL
> + *
> + * If @value is not NULL and the table has a non-0 value_size, the
> + * value at @key is copied to @value. Returns the slot index of the
> + * entry or %-EINVAL if @key was not found.
> + */
> +#define chash_table_copy_out(tbl, key, value) \
> + __chash_table_copy_out(&(*tbl).table, key, value, false)
> +
> +int __chash_table_copy_out(struct __chash_table *table, u64 key,
> + void *value, bool remove);
> +
> +/**
> + * chash_table_remove - Remove an entry from the hash table
> + * @tbl: Pointer to the table structure
> + * @key: Key of the entry to find
> + * @value: Pointer to value to copy, may be NULL
> + *
> + * If @value is not NULL and the table has a non-0 value_size, the
> + * value at @key is copied to @value. The entry is removed from the
> + * table. Returns the slot index of the removed entry or %-EINVAL if
> + * @key was not found.
> + */
> +#define chash_table_remove(tbl, key, value) \
> + __chash_table_copy_out(&(*tbl).table, key, value, true)
> +
> +#define CHASH_SELF_TEST
> +#ifdef CHASH_SELF_TEST
> +int chash_self_test(u8 bits, u8 key_size, int min_fill, int max_fill,
> + u64 iterations);
> +#endif
> +
> +/*
> + * Low level iterator API used internally by the above functions.
> + */
> +struct chash_iter {
> + struct __chash_table *table;
> + unsigned long mask;
> + int slot;
> +};
> +
> +/**
> + * CHASH_ITER_INIT - Initialize a hash table iterator
> + * @tbl: Pointer to hash table to iterate over
> + * @s: Initial slot number
> + */
> +#define CHASH_ITER_INIT(table, s) { \
> + table, \
> + 1UL << ((s) & (BITS_PER_LONG - 1)), \
> + s \
> + }
> +/**
> + * CHASH_ITER_SET - Set hash table iterator to new slot
> + * @iter: Iterator
> + * @s: Slot number
> + */
> +#define CHASH_ITER_SET(iter, s) \
> + (iter).mask = 1UL << ((s) & (BITS_PER_LONG - 1)), \
> + (iter).slot = (s)
> +/**
> + * CHASH_ITER_INC - Increment hash table iterator
> + * @table: Hash table to iterate over
> + *
> + * Wraps around at the end.
> + */
> +#define CHASH_ITER_INC(iter) do { \
> + (iter).mask = (iter).mask << 1 | \
> + (iter).mask >> (BITS_PER_LONG - 1); \
> + (iter).slot = ((iter).slot + 1) & (iter).table->size_mask; \
> + } while (0)
> +
> +static inline bool chash_iter_is_valid(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + return !!(iter.table->valid_bitmap[iter.slot >> _BITOPS_LONG_SHIFT] &
> + iter.mask);
> +}
> +static inline bool chash_iter_is_empty(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + return !(iter.table->occup_bitmap[iter.slot >> _BITOPS_LONG_SHIFT] &
> + iter.mask);
> +}
> +
> +static inline void chash_iter_set_valid(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + iter.table->valid_bitmap[iter.slot >> _BITOPS_LONG_SHIFT] |= iter.mask;
> + iter.table->occup_bitmap[iter.slot >> _BITOPS_LONG_SHIFT] |= iter.mask;
> +}
> +static inline void chash_iter_set_invalid(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + iter.table->valid_bitmap[iter.slot >> _BITOPS_LONG_SHIFT] &= ~iter.mask;
> +}
> +static inline void chash_iter_set_empty(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + iter.table->occup_bitmap[iter.slot >> _BITOPS_LONG_SHIFT] &= ~iter.mask;
> +}
> +
> +static inline u32 chash_iter_key32(const struct chash_iter iter)
> +{
> + BUG_ON(iter.table->key_size != 4);
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + return iter.table->keys32[iter.slot];
> +}
> +static inline u64 chash_iter_key64(const struct chash_iter iter)
> +{
> + BUG_ON(iter.table->key_size != 8);
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + return iter.table->keys64[iter.slot];
> +}
> +static inline u64 chash_iter_key(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + return (iter.table->key_size == 4) ?
> + iter.table->keys32[iter.slot] : iter.table->keys64[iter.slot];
> +}
> +
> +static inline u32 chash_iter_hash32(const struct chash_iter iter)
> +{
> + BUG_ON(iter.table->key_size != 4);
> + return hash_32(chash_iter_key32(iter), iter.table->bits);
> +}
> +
> +static inline u32 chash_iter_hash64(const struct chash_iter iter)
> +{
> + BUG_ON(iter.table->key_size != 8);
> + return hash_64(chash_iter_key64(iter), iter.table->bits);
> +}
> +
> +static inline u32 chash_iter_hash(const struct chash_iter iter)
> +{
> + return (iter.table->key_size == 4) ?
> + hash_32(chash_iter_key32(iter), iter.table->bits) :
> + hash_64(chash_iter_key64(iter), iter.table->bits);
> +}
> +
> +static inline void *chash_iter_value(const struct chash_iter iter)
> +{
> + BUG_ON((unsigned)iter.slot >= (1 << iter.table->bits));
> + return iter.table->values +
> + ((unsigned long)iter.slot * iter.table->value_size);
> +}
> +
> +#endif /* _LINUX_CHASH_H */
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 0c8b78a..e5e1438 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -564,4 +564,12 @@ config PARMAN
> config PRIME_NUMBERS
> tristate
>
> +#
> +# Closed hash table
> +#
> +config CHASH
> + tristate "Closed hash table"
> + help
> + Closed hash table implementation with low memory and CPU overhead.
> +
> endmenu
> diff --git a/lib/Makefile b/lib/Makefile
> index 0166fbc..a44ec9f 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -243,3 +243,5 @@ UBSAN_SANITIZE_ubsan.o := n
> obj-$(CONFIG_SBITMAP) += sbitmap.o
>
> obj-$(CONFIG_PARMAN) += parman.o
> +
> +obj-$(CONFIG_CHASH) += chash.o
> diff --git a/lib/chash.c b/lib/chash.c
> new file mode 100644
> index 0000000..08cdac1
> --- /dev/null
> +++ b/lib/chash.c
> @@ -0,0 +1,521 @@
> +/*
> + * Copyright 2017 Advanced Micro Devices, Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + *
> + */
> +
> +#include <linux/types.h>
> +#include <linux/hash.h>
> +#include <linux/bug.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/chash.h>
> +
> +/**
> + * chash_table_alloc - Allocate closed hash table
> + * @table: Pointer to the table structure
> + * @bits: Table size will be 2^bits entries
> + * @key_size: Size of hash keys in bytes, 4 or 8
> + * @value_size: Size of data values in bytes, can be 0
> + */
> +int chash_table_alloc(struct chash_table *table, u8 bits, u8 key_size,
> + unsigned value_size, gfp_t gfp_mask)
> +{
> + if (bits > 31)
> + return -EINVAL;
> +
> + if (key_size != 4 && key_size != 8)
> + return -EINVAL;
> +
> + table->data = kcalloc(__CHASH_DATA_SIZE(bits, key_size, value_size),
> + sizeof(long), gfp_mask);
> + if (!table->data)
> + return -ENOMEM;
> +
> + __CHASH_TABLE_INIT(table->table, table->data, bits, key_size, value_size);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(chash_table_alloc);
> +
> +/**
> + * chash_table_free - Free closed hash table
> + * @table: Pointer to the table structure
> + */
> +void chash_table_free(struct chash_table *table)
> +{
> + kfree(table->data);
> +}
> +EXPORT_SYMBOL(chash_table_free);
> +
> +#ifdef CHASH_STATS
> +
> +#define DIV_FRAC(nom, denom, quot, frac, frac_digits) do { \
> + (quot) = (nom) / (denom); \
> + (frac) = ((nom) % (denom) * (frac_digits) + \
> + (denom) / 2) / (denom); \
> + } while (0)
> +
> +void __chash_table_dump_stats(struct __chash_table *table)
> +{
> + struct chash_iter iter = CHASH_ITER_INIT(table, 0);
> + u32 filled = 0, empty = 0, tombstones = 0;
> + u32 quot, frac;
> + u32 quot2, frac2;
> +
> + do {
> + if (chash_iter_is_valid(iter))
> + filled++;
> + else if (chash_iter_is_empty(iter))
> + empty++;
> + else
> + tombstones++;
> + CHASH_ITER_INC(iter);
> + } while (iter.slot);
> +
> + pr_info("Hash table key size %d, value size %d\n",
> + table->key_size, table->value_size);
> + pr_info(" Slots total/filled/empty/tombstones: %u / %u / %u / %u\n",
> + 1 << table->bits, filled, empty, tombstones);
> + pr_info(" Avg number of search steps for:\n");
> + if (table->total_add_calls > 0)
> + DIV_FRAC(table->total_add_steps, table->total_add_calls,
> + quot, frac, 1000);
> + else
> + quot = frac = 0;
> + pr_info(" Add : %u.%03u\n", quot, frac);
> + if (table->total_find_calls > 0)
> + DIV_FRAC(table->total_find_steps,
> + table->total_find_calls, quot, frac, 1000);
> + else
> + quot = frac = 0;
> + if (table->total_not_find_calls > 0)
> + DIV_FRAC(table->total_not_find_steps,
> + table->total_not_find_calls, quot2, frac2, 1000);
> + else
> + quot2 = frac2 = 0;
> + pr_info(" Find(hit/miss): %u.%03u / %u.%03u\n", quot, frac, quot2, frac2);
> + if (table->total_relocations) {
> + u64 quot64;
> +
> + DIV_FRAC(table->total_find_calls + table->total_not_find_calls,
> + table->total_relocations, quot64, frac, 1000);
> + DIV_FRAC(table->total_relocation_distance,
> + table->total_relocations, quot2, frac2, 1000);
> + pr_info(" Relocations (freq/avg.dist): 1:%llu.%03u / %u.%03u\n",
> + quot64, frac, quot2, frac2);
> + } else {
> + pr_info(" No relocations\n");
> + }
> +}
> +EXPORT_SYMBOL(__chash_table_dump_stats);
> +
> +#undef DIV_FRAC
> +#endif
> +
> +#define CHASH_INC(table, a) ((a) = ((a) + 1) & (table)->size_mask)
> +#define CHASH_ADD(table, a, b) (((a) + (b)) & (table)->size_mask)
> +#define CHASH_SUB(table, a, b) (((a) - (b)) & (table)->size_mask)
> +#define CHASH_IN_RANGE(table, slot, first, last) \
> + (CHASH_SUB(table, slot, first) <= CHASH_SUB(table, last, first))
> +
> +/*#define CHASH_DEBUG Uncomment this to enable verbose debug output*/
> +#ifdef CHASH_DEBUG
> +static void chash_table_dump(struct __chash_table *table)
> +{
> + struct chash_iter iter = CHASH_ITER_INIT(table, 0);
> +
> + do {
> + if ((iter.slot & 3) == 0)
> + pr_debug("%04x: ", iter.slot);
> +
> + if (chash_iter_is_valid(iter))
> + pr_debug("[%016llx] ", chash_iter_key(iter));
> + else if (chash_iter_is_empty(iter))
> + pr_debug("[ <empty> ] ");
> + else
> + pr_debug("[ <tombstone> ] ");
> +
> + if ((iter.slot & 3) == 3)
> + pr_debug("\n");
> +
> + CHASH_ITER_INC(iter);
> + } while (iter.slot);
> +
> + if ((iter.slot & 3) != 0)
> + pr_debug("\n");
> +}
> +
> +static int chash_table_check(struct __chash_table *table)
> +{
> + u32 hash;
> + struct chash_iter iter = CHASH_ITER_INIT(table, 0);
> + struct chash_iter cur = CHASH_ITER_INIT(table, 0);
> +
> + do {
> + if (!chash_iter_is_valid(iter)) {
> + CHASH_ITER_INC(iter);
> + continue;
> + }
> +
> + hash = chash_iter_hash(iter);
> + CHASH_ITER_SET(cur, hash);
> + while (cur.slot != iter.slot) {
> + if (chash_iter_is_empty(cur)) {
> + pr_err("Path to element at %x with hash %x broken at slot %x\n",
> + iter.slot, hash, cur.slot);
> + chash_table_dump(table);
> + return -EINVAL;
> + }
> + CHASH_ITER_INC(cur);
> + }
> +
> + CHASH_ITER_INC(iter);
> + } while (iter.slot);
> +
> + return 0;
> +}
> +#endif
> +
> +static void chash_iter_relocate(struct chash_iter dst, struct chash_iter src)
> +{
> + BUG_ON(src.table == dst.table && src.slot == dst.slot);
> + BUG_ON(src.table->key_size != src.table->key_size);
> + BUG_ON(src.table->value_size != src.table->value_size);
> +
> + if (dst.table->key_size == 4)
> + dst.table->keys32[dst.slot] = src.table->keys32[src.slot];
> + else
> + dst.table->keys64[dst.slot] = src.table->keys64[src.slot];
> +
> + if (dst.table->value_size)
> + memcpy(chash_iter_value(dst), chash_iter_value(src),
> + dst.table->value_size);
> +
> + chash_iter_set_valid(dst);
> + chash_iter_set_invalid(src);
> +
> +#ifdef CHASH_STATS
> + if (src.table == dst.table) {
> + dst.table->total_relocations++;
> + dst.table->total_relocation_distance +=
> + CHASH_SUB(dst.table, src.slot, dst.slot);
> + }
> +#endif
> +}
> +
> +/**
> + * __chash_table_find - Helper for looking up a hash table entry
> + * @iter: Pointer to hash table iterator
> + * @key: Key of the entry to find
> + * @for_removal: set to true if the element will be removed soon
> + *
> + * Searches for an entry in the hash table with a given key. iter must
> + * be initialized by the caller to point to the home position of the
> + * hypothetical entry, i.e. it must be initialized with the hash table
> + * and the key's hash as the initial slot for the search.
> + *
> + * This function also does some local clean-up to speed up future
> + * look-ups by relocating entries to better slots and removing
> + * tombstones that are no longer needed.
> + *
> + * If @for_removal is true, the function avoids relocating the entry
> + * that is being returned.
> + *
> + * Returns 0 if the search is successful. In this case iter is updated
> + * to point to the found entry. Otherwise %-EINVAL is returned and the
> + * iter is updated to point to the first available slot for the given
> + * key. If the table is full, the slot is set to -1.
> + */
> +static int chash_table_find(struct chash_iter *iter, u64 key,
> + bool for_removal)
> +{
> + u32 hash = iter->slot;
> + struct chash_iter first_redundant = CHASH_ITER_INIT(iter->table, -1);
> + int first_avail = (for_removal ? -2 : -1);
> +
> + while (!chash_iter_is_valid(*iter) || chash_iter_key(*iter) != key) {
> + if (chash_iter_is_empty(*iter)) {
> + /* Found an empty slot, which ends the
> + * search. Clean up any preceding tombstones
> + * that are no longer needed because they lead
> + * to no-where
> + */
> + if ((int)first_redundant.slot < 0)
> + goto not_found;
> + while (first_redundant.slot != iter->slot) {
> + if (!chash_iter_is_valid(first_redundant))
> + chash_iter_set_empty(first_redundant);
> + CHASH_ITER_INC(first_redundant);
> + }
> +#ifdef CHASH_DEBUG
> + chash_table_check(iter->table);
> +#endif
> + goto not_found;
> + } else if (!chash_iter_is_valid(*iter)) {
> + /* Found a tombstone. Remember it as candidate
> + * for relocating the entry we're looking for
> + * or for adding a new entry with the given key
> + */
> + if (first_avail == -1)
> + first_avail = iter->slot;
> + /* Or mark it as the start of a series of
> + * potentially redundant tombstones
> + */
> + else if (first_redundant.slot == -1)
> + CHASH_ITER_SET(first_redundant, iter->slot);
> + } else if (first_redundant.slot >= 0) {
> + /* Found a valid, occupied slot with a
> + * preceding series of tombstones. Relocate it
> + * to a better position that no longer depends
> + * on those tombstones
> + */
> + u32 cur_hash = chash_iter_hash(*iter);
> +
> + if (!CHASH_IN_RANGE(iter->table, cur_hash,
> + first_redundant.slot + 1,
> + iter->slot)) {
> + /* This entry has a hash at or before
> + * the first tombstone we found. We
> + * can relocate it to that tombstone
> + * and advance to the next tombstone
> + */
> + chash_iter_relocate(first_redundant, *iter);
> + do {
> + CHASH_ITER_INC(first_redundant);
> + } while (chash_iter_is_valid(first_redundant));
> + } else if (cur_hash != iter->slot) {
> + /* Relocate entry to its home position
> + * or a close as possible so it no
> + * longer depends on any preceding
> + * tombstones
> + */
> + struct chash_iter new_iter =
> + CHASH_ITER_INIT(iter->table, cur_hash);
> +
> + while (new_iter.slot != iter->slot &&
> + chash_iter_is_valid(new_iter))
> + CHASH_ITER_INC(new_iter);
> +
> + if (new_iter.slot != iter->slot)
> + chash_iter_relocate(new_iter, *iter);
> + }
> + }
> +
> + CHASH_ITER_INC(*iter);
> + if (iter->slot == hash) {
> + iter->slot = -1;
> + goto not_found;
> + }
> + }
> +
> +#ifdef CHASH_STATS
> + iter->table->total_find_calls++;
> + iter->table->total_find_steps +=
> + CHASH_SUB(iter->table, iter->slot, hash) + 1;
> +#endif
> +
> + if (first_avail >= 0) {
> + CHASH_ITER_SET(first_redundant, first_avail);
> + chash_iter_relocate(first_redundant, *iter);
> + iter->slot = first_redundant.slot;
> + iter->mask = first_redundant.mask;
> + }
> +
> + return 0;
> +
> +not_found:
> +#ifdef CHASH_STATS
> + iter->table->total_not_find_calls++;
> + iter->table->total_not_find_steps += (iter->slot < 0) ?
> + (1 << iter->table->bits) :
> + CHASH_SUB(iter->table, iter->slot, hash) + 1;
> +#endif
> + if (first_avail >= 0)
> + CHASH_ITER_SET(*iter, first_avail);
> + return -EINVAL;
> +}
> +
> +int __chash_table_copy_in(struct __chash_table *table, u64 key,
> + const void *value)
> +{
> + u32 hash = (table->key_size == 4) ?
> + hash_32(key, table->bits) : hash_64(key, table->bits);
> + struct chash_iter iter = CHASH_ITER_INIT(table, hash);
> + int r = chash_table_find(&iter, key, false);
> +
> + /* Found an existing entry */
> + if (!r) {
> + if (value && table->value_size)
> + memcpy(chash_iter_value(iter), value,
> + table->value_size);
> + return 1;
> + }
> +
> + /* Is there a place to add a new entry? */
> + if (iter.slot < 0) {
> + pr_err("Hash table overflow\n");
> + return -ENOMEM;
> + }
> +
> + chash_iter_set_valid(iter);
> +
> + if (table->key_size == 4)
> + table->keys32[iter.slot] = key;
> + else
> + table->keys64[iter.slot] = key;
> + if (value && table->value_size)
> + memcpy(chash_iter_value(iter), value, table->value_size);
> +
> +#ifdef CHASH_STATS
> + table->total_add_calls++;
> + table->total_add_steps += CHASH_SUB(table, iter.slot, hash) + 1;
> +#endif
> + return 0;
> +}
> +EXPORT_SYMBOL(__chash_table_copy_in);
> +
> +int __chash_table_copy_out(struct __chash_table *table, u64 key,
> + void *value, bool remove)
> +{
> + u32 hash = (table->key_size == 4) ?
> + hash_32(key, table->bits) : hash_64(key, table->bits);
> + struct chash_iter iter = CHASH_ITER_INIT(table, hash);
> + int r = chash_table_find(&iter, key, remove);
> +
> + if (r < 0)
> + return r;
> +
> + if (value && table->value_size)
> + memcpy(value, chash_iter_value(iter), table->value_size);
> +
> + if (remove)
> + chash_iter_set_invalid(iter);
> +
> + return iter.slot;
> +}
> +EXPORT_SYMBOL(__chash_table_copy_out);
> +
> +#ifdef CHASH_SELF_TEST
> +/**
> + * chash_self_test - Run a self-test of the hash table implementation
> + * @bits: Table size will be 2^bits entries
> + * @key_size: Size of hash keys in bytes, 4 or 8
> + * @min_fill: Minimum fill level during the test
> + * @max_fill: Maximum fill level during the test
> + * @iterations: Number of test iterations
> + *
> + * The test adds and removes entries from a hash table, cycling the
> + * fill level between min_fill and max_fill entries. Also tests lookup
> + * and value retrieval.
> + */
> +int chash_self_test(u8 bits, u8 key_size, int min_fill, int max_fill,
> + u64 iterations)
> +{
> + struct chash_table table;
> + int ret;
> + u64 add_count, rmv_count;
> + u64 value;
> +
> + if (key_size == 4 && iterations > 0xffffffff)
> + return -EINVAL;
> + if (min_fill >= max_fill)
> + return -EINVAL;
> +
> + ret = chash_table_alloc(&table, bits, key_size, sizeof(u64),
> + GFP_KERNEL);
> + if (ret) {
> + pr_err("chash_table_alloc failed: %d\n", ret);
> + return ret;
> + }
> +
> + for (add_count = 0, rmv_count = 0; add_count < iterations;
> + add_count++) {
> + /* When we hit the max_fill level, remove entries down
> + * to min_fill */
> + if (add_count - rmv_count == max_fill) {
> + u64 find_count = rmv_count;
> +
> + /* First try to find all entries that we're
> + * about to remove, confirm their value, test
> + * writing them back a second time. */
> + for (; add_count - find_count > min_fill;
> + find_count++) {
> + ret = chash_table_copy_out(&table, find_count,
> + &value);
> + if (ret < 0) {
> + pr_err("chash_table_copy_out failed: %d\n",
> + ret);
> + goto out;
> + }
> + if (value != ~find_count) {
> + pr_err("Wrong value retrieved for key 0x%llx, expected 0x%llx got 0x%llx\n",
> + find_count, ~find_count, value);
> +#ifdef CHASH_DEBUG
> + chash_table_dump(&table.table);
> +#endif
> + ret = -EFAULT;
> + goto out;
> + }
> + ret = chash_table_copy_in(&table, find_count,
> + &value);
> + if (ret != 1) {
> + pr_err("copy_in second time returned %d, expected 1\n",
> + ret);
> + ret = -EFAULT;
> + goto out;
> + }
> + }
> + /* Remove them until we hit min_fill level */
> + for (; add_count - rmv_count > min_fill; rmv_count++) {
> + ret = chash_table_remove(&table, rmv_count, NULL);
> + if (ret < 0) {
> + pr_err("chash_table_remove failed: %d\n",
> + ret);
> + goto out;
> + }
> + }
> + }
> +
> + /* Add a new value */
> + value = ~add_count;
> + ret = chash_table_copy_in(&table, add_count, &value);
> + if (ret != 0) {
> + pr_err("copy_in first time returned %d, expected 0\n",
> + ret);
> + ret = -EFAULT;
> + goto out;
> + }
> + }
> +
> +#ifdef CHASH_STATS
> + chash_table_dump_stats(&table);
> +#endif
> +
> +out:
> + chash_table_free(&table);
> + return ret;
> +}
> +EXPORT_SYMBOL(chash_self_test);
> +
> +#endif /* CHASH_SELF_TEST */
> +
> +MODULE_DESCRIPTION("Closed hash table");
> +MODULE_LICENSE("GPL and additional rights");
