libcfs/include/libcfs/libcfs_hash.h

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * GPL HEADER START
   5  *
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 only,
  10  * as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License version 2 for more details (a copy is included
  16  * in the LICENSE file that accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * version 2 along with this program; If not, see
  20  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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  24  * have any questions.
  25  *
  26  * GPL HEADER END
  27  */
  28 /*
  29  * Copyright  2008 Sun Microsystems, Inc. All rights reserved
  30  * Use is subject to license terms.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * libcfs/include/libcfs/libcfs_hash.h
  37  *
  38  * Hashing routines
  39  *
  40  */
  41
  42 #ifndef __LIBCFS_HASH_H__
  43 #define __LIBCFS_HASH_H__
  44 /*
  45  * Knuth recommends primes in approximately golden ratio to the maximum
  46  * integer representable by a machine word for multiplicative hashing.
  47  * Chuck Lever verified the effectiveness of this technique:
  48  * http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf
  49  *
  50  * These primes are chosen to be bit-sparse, that is operations on
  51  * them can use shifts and additions instead of multiplications for
  52  * machines where multiplications are slow.
  53  */
  54 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
  55 #define CFS_GOLDEN_RATIO_PRIME_32 0x9e370001UL
  56 /*  2^63 + 2^61 - 2^57 + 2^54 - 2^51 - 2^18 + 1 */
  57 #define CFS_GOLDEN_RATIO_PRIME_64 0x9e37fffffffc0001ULL
  58
  59 /*
  60  * Ideally we would use HAVE_HASH_LONG for this, but on linux we configure
  61  * the linux kernel and user space at the same time, so we need to differentiate
  62  * between them explicitely. If this is not needed on other architectures, then
  63  * we'll need to move the functions to archi specific headers.
  64  */
  65
  66 #if (defined __linux__ && defined __KERNEL__)
  67 #include <linux/hash.h>
  68
  69 #define cfs_hash_long(val, bits)    hash_long(val, bits)
  70 #else
  71 /* Fast hashing routine for a long.
  72    (C) 2002 William Lee Irwin III, IBM */
  73
  74 #if BITS_PER_LONG == 32
  75 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
  76 #define CFS_GOLDEN_RATIO_PRIME          CFS_GOLDEN_RATIO_PRIME_32
  77 #elif BITS_PER_LONG == 64
  78 /*  2^63 + 2^61 - 2^57 + 2^54 - 2^51 - 2^18 + 1 */
  79 #define CFS_GOLDEN_RATIO_PRIME          CFS_GOLDEN_RATIO_PRIME_64
  80 #else
  81 #error Define CFS_GOLDEN_RATIO_PRIME for your wordsize.
  82 #endif
  83
  84 static inline unsigned long cfs_hash_long(unsigned long val, unsigned int bits)
  85 {
  86         unsigned long hash = val;
  87
  88 #if BITS_PER_LONG == 64
  89         /*  Sigh, gcc can't optimise this alone like it does for 32 bits. */
  90         unsigned long n = hash;
  91         n <<= 18;
  92         hash -= n;
  93         n <<= 33;
  94         hash -= n;
  95         n <<= 3;
  96         hash += n;
  97         n <<= 3;
  98         hash -= n;
  99         n <<= 4;
 100         hash += n;
 101         n <<= 2;
 102         hash += n;
 103 #else
 104         /* On some cpus multiply is faster, on others gcc will do shifts */
 105         hash *= CFS_GOLDEN_RATIO_PRIME;
 106 #endif
 107
 108         /* High bits are more random, so use them. */
 109         return hash >> (BITS_PER_LONG - bits);
 110 }
 111 #if 0
 112 static inline unsigned long hash_ptr(void *ptr, unsigned int bits)
 113 {
 114         return cfs_hash_long((unsigned long)ptr, bits);
 115 }
 116 #endif
 117
 118 /* !(__linux__ && __KERNEL__) */
 119 #endif
 120
 121 struct cfs_hash_ops;
 122
 123 typedef struct cfs_hash_bucket {
 124         cfs_hlist_head_t            hsb_head;       /* entries list */
 125         cfs_atomic_t                hsb_count;      /* current entries */
 126         cfs_rwlock_t                hsb_rwlock;     /* cfs_hash_bucket */
 127 } cfs_hash_bucket_t;
 128
 129 #define CFS_MAX_HASH_NAME 16
 130
 131 typedef struct cfs_hash {
 132         int                         hs_cur_bits;    /* current hash bits */
 133         int                         hs_cur_mask;    /* current hash mask */
 134         int                         hs_min_bits;    /* min hash bits */
 135         int                         hs_max_bits;    /* max hash bits */
 136         int                         hs_min_theta;   /* resize min threshold */
 137         int                         hs_max_theta;   /* resize max threshold */
 138         int                         hs_flags;       /* hash flags */
 139         cfs_atomic_t                hs_count;       /* current entries */
 140         cfs_atomic_t                hs_rehash_count;/* resize count */
 141         struct cfs_hash_bucket    **hs_buckets;     /* hash buckets */
 142         struct cfs_hash_ops        *hs_ops;         /* hash operations */
 143         cfs_rwlock_t                hs_rwlock;      /* cfs_hash */
 144         cfs_atomic_t                hs_refcount;
 145         char                        hs_name[CFS_MAX_HASH_NAME];
 146 } cfs_hash_t;
 147
 148 typedef struct cfs_hash_ops {
 149         unsigned (*hs_hash)(cfs_hash_t *hs, void *key, unsigned mask);
 150         void *   (*hs_key)(cfs_hlist_node_t *hnode);
 151         int      (*hs_compare)(void *key, cfs_hlist_node_t *hnode);
 152         void *   (*hs_get)(cfs_hlist_node_t *hnode);
 153         void *   (*hs_put)(cfs_hlist_node_t *hnode);
 154         void     (*hs_exit)(cfs_hlist_node_t *hnode);
 155 } cfs_hash_ops_t;
 156
 157 #define CFS_HASH_DEBUG          0x0001  /* Enable expensive debug checks */
 158 #define CFS_HASH_REHASH         0x0002  /* Enable dynamic hash resizing */
 159
 160 #define CFS_HO(hs)             (hs)->hs_ops
 161 #define CFS_HOP(hs, op)        (hs)->hs_ops->hs_ ## op
 162
 163 static inline unsigned
 164 cfs_hash_id(cfs_hash_t *hs, void *key, unsigned mask)
 165 {
 166         LASSERT(hs);
 167         LASSERT(CFS_HO(hs));
 168         LASSERT(CFS_HOP(hs, hash));
 169
 170         return CFS_HOP(hs, hash)(hs, key, mask);
 171 }
 172
 173 static inline void *
 174 cfs_hash_key(cfs_hash_t *hs, cfs_hlist_node_t *hnode)
 175 {
 176         LASSERT(hs);
 177         LASSERT(hnode);
 178         LASSERT(CFS_HO(hs));
 179         LASSERT(CFS_HOP(hs, key));
 180
 181         return CFS_HOP(hs, key)(hnode);
 182 }
 183
 184 /* Returns 1 on a match,
 185  * XXX: This would be better if it returned, -1, 0, or 1 for
 186  *      <, =, > respectivly.  It could then be used to implement
 187  *      a CFS_HASH_SORT feature flags which could keep each hash
 188  *      bucket in order.  This would increase insertion times
 189  *      but could reduce lookup times for deep chains.  Ideally,
 190  *      the rehash should keep chain depth short but if that
 191  *      ends up not being the case this would be a nice feature.
 192  */
 193 static inline int
 194 cfs_hash_compare(cfs_hash_t *hs, void *key, cfs_hlist_node_t *hnode)
 195 {
 196         LASSERT(hs);
 197         LASSERT(hnode);
 198         LASSERT(CFS_HO(hs));
 199
 200         if (CFS_HOP(hs, compare))
 201                 return CFS_HOP(hs, compare)(key, hnode);
 202
 203         return -EOPNOTSUPP;
 204 }
 205
 206 static inline void *
 207 cfs_hash_get(cfs_hash_t *hs, cfs_hlist_node_t *hnode)
 208 {
 209         LASSERT(hs);
 210         LASSERT(hnode);
 211         LASSERT(CFS_HO(hs));
 212
 213         if (CFS_HOP(hs, get))
 214                 return CFS_HOP(hs, get)(hnode);
 215
 216         return NULL;
 217 }
 218
 219 static inline void *
 220 cfs_hash_put(cfs_hash_t *hs, cfs_hlist_node_t *hnode)
 221 {
 222         LASSERT(hs);
 223         LASSERT(hnode);
 224         LASSERT(CFS_HO(hs));
 225
 226         if (CFS_HOP(hs, put))
 227                 return CFS_HOP(hs, put)(hnode);
 228
 229         return NULL;
 230 }
 231
 232 static inline void
 233 cfs_hash_exit(cfs_hash_t *hs, cfs_hlist_node_t *hnode)
 234 {
 235         LASSERT(hs);
 236         LASSERT(hnode);
 237         LASSERT(CFS_HO(hs));
 238
 239         if (CFS_HOP(hs, exit))
 240                 return CFS_HOP(hs, exit)(hnode);
 241 }
 242
 243 /* Validate hnode references the correct key */
 244 static inline void
 245 __cfs_hash_key_validate(cfs_hash_t *hs, void *key,
 246                         cfs_hlist_node_t *hnode)
 247 {
 248         if (unlikely(hs->hs_flags & CFS_HASH_DEBUG))
 249                 LASSERT(cfs_hash_compare(hs, key, hnode) > 0);
 250 }
 251
 252 /* Validate hnode is in the correct bucket */
 253 static inline void
 254 __cfs_hash_bucket_validate(cfs_hash_t *hs, cfs_hash_bucket_t *hsb,
 255                            cfs_hlist_node_t *hnode)
 256 {
 257         unsigned i;
 258
 259         if (unlikely(hs->hs_flags & CFS_HASH_DEBUG)) {
 260                 i = cfs_hash_id(hs, cfs_hash_key(hs, hnode), hs->hs_cur_mask);
 261                 LASSERT(hs->hs_buckets[i] == hsb);
 262         }
 263 }
 264
 265 static inline cfs_hlist_node_t *
 266 __cfs_hash_bucket_lookup(cfs_hash_t *hs,
 267                          cfs_hash_bucket_t *hsb, void *key)
 268 {
 269         cfs_hlist_node_t *hnode;
 270
 271         cfs_hlist_for_each(hnode, &hsb->hsb_head)
 272                 if (cfs_hash_compare(hs, key, hnode) > 0)
 273                         return hnode;
 274
 275         return NULL;
 276 }
 277
 278 static inline void *
 279 __cfs_hash_bucket_add(cfs_hash_t *hs,
 280                       cfs_hash_bucket_t *hsb,
 281                       cfs_hlist_node_t *hnode)
 282 {
 283         cfs_hlist_add_head(hnode, &(hsb->hsb_head));
 284         cfs_atomic_inc(&hsb->hsb_count);
 285         cfs_atomic_inc(&hs->hs_count);
 286
 287         return cfs_hash_get(hs, hnode);
 288 }
 289
 290 static inline void *
 291 __cfs_hash_bucket_del(cfs_hash_t *hs,
 292                       cfs_hash_bucket_t *hsb,
 293                       cfs_hlist_node_t *hnode)
 294 {
 295         cfs_hlist_del_init(hnode);
 296         LASSERT(cfs_atomic_read(&hsb->hsb_count) > 0);
 297         cfs_atomic_dec(&hsb->hsb_count);
 298         LASSERT(cfs_atomic_read(&hs->hs_count) > 0);
 299         cfs_atomic_dec(&hs->hs_count);
 300
 301         return cfs_hash_put(hs, hnode);
 302 }
 303
 304 /* Hash init/cleanup functions */
 305 cfs_hash_t *cfs_hash_create(char *name, unsigned int cur_bits,
 306                             unsigned int max_bits,
 307                             cfs_hash_ops_t *ops, int flags);
 308 cfs_hash_t *cfs_hash_getref(cfs_hash_t *hs);
 309 void cfs_hash_putref(cfs_hash_t *hs);
 310
 311 /* Hash addition functions */
 312 void cfs_hash_add(cfs_hash_t *hs, void *key,
 313                   cfs_hlist_node_t *hnode);
 314 int cfs_hash_add_unique(cfs_hash_t *hs, void *key,
 315                         cfs_hlist_node_t *hnode);
 316 void *cfs_hash_findadd_unique(cfs_hash_t *hs, void *key,
 317                               cfs_hlist_node_t *hnode);
 318
 319 /* Hash deletion functions */
 320 void *cfs_hash_del(cfs_hash_t *hs, void *key, cfs_hlist_node_t *hnode);
 321 void *cfs_hash_del_key(cfs_hash_t *hs, void *key);
 322
 323 /* Hash lookup/for_each functions */
 324 void *cfs_hash_lookup(cfs_hash_t *hs, void *key);
 325 typedef void (*cfs_hash_for_each_cb_t)(void *obj, void *data);
 326 void cfs_hash_for_each(cfs_hash_t *hs, cfs_hash_for_each_cb_t, void *data);
 327 void cfs_hash_for_each_safe(cfs_hash_t *hs, cfs_hash_for_each_cb_t, void *data);
 328 void cfs_hash_for_each_empty(cfs_hash_t *hs, cfs_hash_for_each_cb_t, void *data);
 329 void cfs_hash_for_each_key(cfs_hash_t *hs, void *key,
 330                            cfs_hash_for_each_cb_t, void *data);
 331
 332 /*
 333  * Rehash - Theta is calculated to be the average chained
 334  * hash depth assuming a perfectly uniform hash funcion.
 335  */
 336 int cfs_hash_rehash(cfs_hash_t *hs, int bits);
 337 void cfs_hash_rehash_key(cfs_hash_t *hs, void *old_key,
 338                          void *new_key, cfs_hlist_node_t *hnode);
 339
 340
 341 #define CFS_HASH_THETA_BITS  10
 342
 343 /* Return integer component of theta */
 344 static inline int __cfs_hash_theta_int(int theta)
 345 {
 346         return (theta >> CFS_HASH_THETA_BITS);
 347 }
 348
 349 /* Return a fractional value between 0 and 999 */
 350 static inline int __cfs_hash_theta_frac(int theta)
 351 {
 352         return ((theta * 1000) >> CFS_HASH_THETA_BITS) -
 353                (__cfs_hash_theta_int(theta) * 1000);
 354 }
 355
 356 static inline int __cfs_hash_theta(cfs_hash_t *hs)
 357 {
 358         return (cfs_atomic_read(&hs->hs_count) <<
 359                 CFS_HASH_THETA_BITS) >> hs->hs_cur_bits;
 360 }
 361
 362 static inline void __cfs_hash_set_theta(cfs_hash_t *hs, int min, int max)
 363 {
 364         LASSERT(min < max);
 365         hs->hs_min_theta = min;
 366         hs->hs_max_theta = max;
 367 }
 368
 369 /* Generic debug formatting routines mainly for proc handler */
 370 int cfs_hash_debug_header(char *str, int size);
 371 int cfs_hash_debug_str(cfs_hash_t *hs, char *str, int size);
 372
 373 /*
 374  * Generic djb2 hash algorithm for character arrays.
 375  */
 376 static inline unsigned
 377 cfs_hash_djb2_hash(void *key, size_t size, unsigned mask)
 378 {
 379         unsigned i, hash = 5381;
 380
 381         LASSERT(key != NULL);
 382
 383         for (i = 0; i < size; i++)
 384                 hash = hash * 33 + ((char *)key)[i];
 385
 386         return (hash & mask);
 387 }
 388
 389 /*
 390  * Generic u32 hash algorithm.
 391  */
 392 static inline unsigned
 393 cfs_hash_u32_hash(__u32 key, unsigned mask)
 394 {
 395         return ((key * CFS_GOLDEN_RATIO_PRIME_32) & mask);
 396 }
 397
 398 /*
 399  * Generic u64 hash algorithm.
 400  */
 401 static inline unsigned
 402 cfs_hash_u64_hash(__u64 key, unsigned mask)
 403 {
 404         return ((unsigned)(key * CFS_GOLDEN_RATIO_PRIME_64) & mask);
 405 }
 406
 407 #define cfs_hash_for_each_bucket(hs, hsb, pos)   \
 408         for (pos = 0;                            \
 409              pos <= hs->hs_cur_mask &&           \
 410              (hsb = hs->hs_buckets[pos]);       \
 411              pos++)
 412
 413 #define cfs_hash_for_each_bucket_restart(hs, hsb, pos)  \
 414         for (/* pos=0 done once by caller */;           \
 415              pos <= hs->hs_cur_mask &&                  \
 416              (hsb = hs->hs_buckets[pos]);              \
 417              pos++)
 418 /* !__LIBCFS__HASH_H__ */
 419 #endif