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36 * libcfs/include/libcfs/libcfs_hash.h
42 #ifndef __LIBCFS_HASH_H__
43 #define __LIBCFS_HASH_H__
45 #include <linux/hash.h>
48 * Knuth recommends primes in approximately golden ratio to the maximum
49 * integer representable by a machine word for multiplicative hashing.
50 * Chuck Lever verified the effectiveness of this technique:
51 * http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf
53 * These primes are chosen to be bit-sparse, that is operations on
54 * them can use shifts and additions instead of multiplications for
55 * machines where multiplications are slow.
57 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
58 #define CFS_GOLDEN_RATIO_PRIME_32 0x9e370001UL
59 /* 2^63 + 2^61 - 2^57 + 2^54 - 2^51 - 2^18 + 1 */
60 #define CFS_GOLDEN_RATIO_PRIME_64 0x9e37fffffffc0001ULL
63 #define CFS_HASH_DEBUG_NONE 0
64 /** record hash depth and output to console when it's too deep,
65 * computing overhead is low but consume more memory */
66 #define CFS_HASH_DEBUG_1 1
67 /** expensive, check key validation */
68 #define CFS_HASH_DEBUG_2 2
70 #define CFS_HASH_DEBUG_LEVEL CFS_HASH_DEBUG_NONE
73 struct cfs_hash_lock_ops;
74 struct cfs_hash_hlist_ops;
77 rwlock_t rw; /**< rwlock */
78 spinlock_t spin; /**< spinlock */
82 * cfs_hash_bucket is a container of:
84 * - array of hash-head starting from hsb_head[0], hash-head can be one of
85 * . struct cfs_hash_head
86 * . struct cfs_hash_head_dep
87 * . struct cfs_hash_dhead
88 * . struct cfs_hash_dhead_dep
89 * which depends on requirement of user
90 * - some extra bytes (caller can require it while creating hash)
92 struct cfs_hash_bucket {
93 union cfs_hash_lock hsb_lock; /**< bucket lock */
94 __u32 hsb_count; /**< current entries */
95 __u32 hsb_version; /**< change version */
96 unsigned int hsb_index; /**< index of bucket */
97 int hsb_depmax; /**< max depth on bucket */
98 long hsb_head[0]; /**< hash-head array */
102 * cfs_hash bucket descriptor, it's normally in stack of caller
105 /**< address of bucket */
106 struct cfs_hash_bucket *bd_bucket;
107 /**< offset in bucket */
108 unsigned int bd_offset;
111 #define CFS_HASH_NAME_LEN 16 /**< default name length */
112 #define CFS_HASH_BIGNAME_LEN 64 /**< bigname for param tree */
114 #define CFS_HASH_BKT_BITS 3 /**< default bits of bucket */
115 #define CFS_HASH_BITS_MAX 30 /**< max bits of bucket */
116 #define CFS_HASH_BITS_MIN CFS_HASH_BKT_BITS
119 * common hash attributes.
123 * don't need any lock, caller will protect operations with it's
124 * own lock. With this flag:
125 * . CFS_HASH_NO_BKTLOCK, CFS_HASH_RW_BKTLOCK, CFS_HASH_SPIN_BKTLOCK
127 * . Some functions will be disabled with this flag, i.e:
128 * cfs_hash_for_each_empty, cfs_hash_rehash
130 CFS_HASH_NO_LOCK = 1 << 0,
131 /** no bucket lock, use one spinlock to protect the whole hash */
132 CFS_HASH_NO_BKTLOCK = 1 << 1,
133 /** rwlock to protect bucket */
134 CFS_HASH_RW_BKTLOCK = 1 << 2,
135 /** spinlock to protect bucket */
136 CFS_HASH_SPIN_BKTLOCK = 1 << 3,
137 /** always add new item to tail */
138 CFS_HASH_ADD_TAIL = 1 << 4,
139 /** hash-table doesn't have refcount on item */
140 CFS_HASH_NO_ITEMREF = 1 << 5,
141 /** big name for param-tree */
142 CFS_HASH_BIGNAME = 1 << 6,
143 /** track global count */
144 CFS_HASH_COUNTER = 1 << 7,
145 /** rehash item by new key */
146 CFS_HASH_REHASH_KEY = 1 << 8,
147 /** Enable dynamic hash resizing */
148 CFS_HASH_REHASH = 1 << 9,
149 /** can shrink hash-size */
150 CFS_HASH_SHRINK = 1 << 10,
151 /** assert hash is empty on exit */
152 CFS_HASH_ASSERT_EMPTY = 1 << 11,
153 /** record hlist depth */
154 CFS_HASH_DEPTH = 1 << 12,
156 * rehash is always scheduled in a different thread, so current
157 * change on hash table is non-blocking
159 CFS_HASH_NBLK_CHANGE = 1 << 13,
160 /** NB, we typed hs_flags as __u16, please change it
161 * if you need to extend >=16 flags */
164 /** most used attributes */
165 #define CFS_HASH_DEFAULT (CFS_HASH_RW_BKTLOCK | \
166 CFS_HASH_COUNTER | CFS_HASH_REHASH)
169 * cfs_hash is a hash-table implementation for general purpose, it can support:
170 * . two refcount modes
171 * hash-table with & without refcount
173 * nolock, one-spinlock, rw-bucket-lock, spin-bucket-lock
174 * . general operations
175 * lookup, add(add_tail or add_head), delete
179 * locked iteration and unlocked iteration
181 * support long name hash
183 * trace max searching depth
186 * When the htable grows or shrinks, a separate task (cfs_hash_rehash_worker)
187 * is spawned to handle the rehash in the background, it's possible that other
188 * processes can concurrently perform additions, deletions, and lookups
189 * without being blocked on rehash completion, because rehash will release
190 * the global wrlock for each bucket.
192 * rehash and iteration can't run at the same time because it's too tricky
193 * to keep both of them safe and correct.
194 * As they are relatively rare operations, so:
195 * . if iteration is in progress while we try to launch rehash, then
196 * it just giveup, iterator will launch rehash at the end.
197 * . if rehash is in progress while we try to iterate the hash table,
198 * then we just wait (shouldn't be very long time), anyway, nobody
199 * should expect iteration of whole hash-table to be non-blocking.
201 * During rehashing, a (key,object) pair may be in one of two buckets,
202 * depending on whether the worker task has yet to transfer the object
203 * to its new location in the table. Lookups and deletions need to search both
204 * locations; additions must take care to only insert into the new bucket.
208 /** serialize with rehash, or serialize all operations if
209 * the hash-table has CFS_HASH_NO_BKTLOCK */
210 union cfs_hash_lock hs_lock;
211 /** hash operations */
212 struct cfs_hash_ops *hs_ops;
213 /** hash lock operations */
214 struct cfs_hash_lock_ops *hs_lops;
215 /** hash list operations */
216 struct cfs_hash_hlist_ops *hs_hops;
217 /** hash buckets-table */
218 struct cfs_hash_bucket **hs_buckets;
219 /** total number of items on this hash-table */
221 /** hash flags, see cfs_hash_tag for detail */
223 /** # of extra-bytes for bucket, for user saving extended attributes */
224 __u16 hs_extra_bytes;
225 /** wants to iterate */
227 /** hash-table is dying */
229 /** current hash bits */
235 /** bits for rehash */
237 /** bits for each bucket */
239 /** resize min threshold */
241 /** resize max threshold */
244 __u32 hs_rehash_count;
245 /** # of iterators (caller of cfs_hash_for_each_*) */
247 /** rehash workitem */
248 struct cfs_workitem hs_rehash_wi;
249 /** refcount on this hash table */
250 atomic_t hs_refcount;
251 /** rehash buckets-table */
252 struct cfs_hash_bucket **hs_rehash_buckets;
253 #if CFS_HASH_DEBUG_LEVEL >= CFS_HASH_DEBUG_1
254 /** serialize debug members */
255 spinlock_t hs_dep_lock;
257 unsigned int hs_dep_max;
258 /** id of the deepest bucket */
259 unsigned int hs_dep_bkt;
260 /** offset in the deepest bucket */
261 unsigned int hs_dep_off;
262 /** bits when we found the max depth */
263 unsigned int hs_dep_bits;
264 /** workitem to output max depth */
265 struct cfs_workitem hs_dep_wi;
267 /** name of htable */
271 struct cfs_hash_lock_ops {
272 /** lock the hash table */
273 void (*hs_lock)(union cfs_hash_lock *lock, int exclusive);
274 /** unlock the hash table */
275 void (*hs_unlock)(union cfs_hash_lock *lock, int exclusive);
276 /** lock the hash bucket */
277 void (*hs_bkt_lock)(union cfs_hash_lock *lock, int exclusive);
278 /** unlock the hash bucket */
279 void (*hs_bkt_unlock)(union cfs_hash_lock *lock, int exclusive);
282 struct cfs_hash_hlist_ops {
283 /** return hlist_head of hash-head of @bd */
284 struct hlist_head *(*hop_hhead)(struct cfs_hash *hs, struct cfs_hash_bd *bd);
285 /** return hash-head size */
286 int (*hop_hhead_size)(struct cfs_hash *hs);
287 /** add @hnode to hash-head of @bd */
288 int (*hop_hnode_add)(struct cfs_hash *hs, struct cfs_hash_bd *bd,
289 struct hlist_node *hnode);
290 /** remove @hnode from hash-head of @bd */
291 int (*hop_hnode_del)(struct cfs_hash *hs, struct cfs_hash_bd *bd,
292 struct hlist_node *hnode);
295 struct cfs_hash_ops {
296 /** return hashed value from @key */
297 unsigned (*hs_hash)(struct cfs_hash *hs, const void *key, unsigned mask);
298 /** return key address of @hnode */
299 void * (*hs_key)(struct hlist_node *hnode);
300 /** copy key from @hnode to @key */
301 void (*hs_keycpy)(struct hlist_node *hnode, void *key);
303 * compare @key with key of @hnode
304 * returns 1 on a match
306 int (*hs_keycmp)(const void *key, struct hlist_node *hnode);
307 /** return object address of @hnode, i.e: container_of(...hnode) */
308 void * (*hs_object)(struct hlist_node *hnode);
309 /** get refcount of item, always called with holding bucket-lock */
310 void (*hs_get)(struct cfs_hash *hs, struct hlist_node *hnode);
311 /** release refcount of item */
312 void (*hs_put)(struct cfs_hash *hs, struct hlist_node *hnode);
313 /** release refcount of item, always called with holding bucket-lock */
314 void (*hs_put_locked)(struct cfs_hash *hs, struct hlist_node *hnode);
315 /** it's called before removing of @hnode */
316 void (*hs_exit)(struct cfs_hash *hs, struct hlist_node *hnode);
319 /** total number of buckets in @hs */
320 #define CFS_HASH_NBKT(hs) \
321 (1U << ((hs)->hs_cur_bits - (hs)->hs_bkt_bits))
323 /** total number of buckets in @hs while rehashing */
324 #define CFS_HASH_RH_NBKT(hs) \
325 (1U << ((hs)->hs_rehash_bits - (hs)->hs_bkt_bits))
327 /** number of hlist for in bucket */
328 #define CFS_HASH_BKT_NHLIST(hs) (1U << (hs)->hs_bkt_bits)
330 /** total number of hlist in @hs */
331 #define CFS_HASH_NHLIST(hs) (1U << (hs)->hs_cur_bits)
333 /** total number of hlist in @hs while rehashing */
334 #define CFS_HASH_RH_NHLIST(hs) (1U << (hs)->hs_rehash_bits)
337 cfs_hash_with_no_lock(struct cfs_hash *hs)
339 /* caller will serialize all operations for this hash-table */
340 return (hs->hs_flags & CFS_HASH_NO_LOCK) != 0;
344 cfs_hash_with_no_bktlock(struct cfs_hash *hs)
346 /* no bucket lock, one single lock to protect the hash-table */
347 return (hs->hs_flags & CFS_HASH_NO_BKTLOCK) != 0;
351 cfs_hash_with_rw_bktlock(struct cfs_hash *hs)
353 /* rwlock to protect hash bucket */
354 return (hs->hs_flags & CFS_HASH_RW_BKTLOCK) != 0;
358 cfs_hash_with_spin_bktlock(struct cfs_hash *hs)
360 /* spinlock to protect hash bucket */
361 return (hs->hs_flags & CFS_HASH_SPIN_BKTLOCK) != 0;
365 cfs_hash_with_add_tail(struct cfs_hash *hs)
367 return (hs->hs_flags & CFS_HASH_ADD_TAIL) != 0;
371 cfs_hash_with_no_itemref(struct cfs_hash *hs)
373 /* hash-table doesn't keep refcount on item,
374 * item can't be removed from hash unless it's
376 return (hs->hs_flags & CFS_HASH_NO_ITEMREF) != 0;
380 cfs_hash_with_bigname(struct cfs_hash *hs)
382 return (hs->hs_flags & CFS_HASH_BIGNAME) != 0;
386 cfs_hash_with_counter(struct cfs_hash *hs)
388 return (hs->hs_flags & CFS_HASH_COUNTER) != 0;
392 cfs_hash_with_rehash(struct cfs_hash *hs)
394 return (hs->hs_flags & CFS_HASH_REHASH) != 0;
398 cfs_hash_with_rehash_key(struct cfs_hash *hs)
400 return (hs->hs_flags & CFS_HASH_REHASH_KEY) != 0;
404 cfs_hash_with_shrink(struct cfs_hash *hs)
406 return (hs->hs_flags & CFS_HASH_SHRINK) != 0;
410 cfs_hash_with_assert_empty(struct cfs_hash *hs)
412 return (hs->hs_flags & CFS_HASH_ASSERT_EMPTY) != 0;
416 cfs_hash_with_depth(struct cfs_hash *hs)
418 return (hs->hs_flags & CFS_HASH_DEPTH) != 0;
422 cfs_hash_with_nblk_change(struct cfs_hash *hs)
424 return (hs->hs_flags & CFS_HASH_NBLK_CHANGE) != 0;
428 cfs_hash_is_exiting(struct cfs_hash *hs)
429 { /* cfs_hash_destroy is called */
430 return hs->hs_exiting;
434 cfs_hash_is_rehashing(struct cfs_hash *hs)
435 { /* rehash is launched */
436 return hs->hs_rehash_bits != 0;
440 cfs_hash_is_iterating(struct cfs_hash *hs)
441 { /* someone is calling cfs_hash_for_each_* */
442 return hs->hs_iterating || hs->hs_iterators != 0;
446 cfs_hash_bkt_size(struct cfs_hash *hs)
448 return offsetof(struct cfs_hash_bucket, hsb_head[0]) +
449 hs->hs_hops->hop_hhead_size(hs) * CFS_HASH_BKT_NHLIST(hs) +
453 static inline unsigned
454 cfs_hash_id(struct cfs_hash *hs, const void *key, unsigned mask)
456 return hs->hs_ops->hs_hash(hs, key, mask);
460 cfs_hash_key(struct cfs_hash *hs, struct hlist_node *hnode)
462 return hs->hs_ops->hs_key(hnode);
466 cfs_hash_keycpy(struct cfs_hash *hs, struct hlist_node *hnode, void *key)
468 if (hs->hs_ops->hs_keycpy != NULL)
469 hs->hs_ops->hs_keycpy(hnode, key);
473 * Returns 1 on a match,
476 cfs_hash_keycmp(struct cfs_hash *hs, const void *key, struct hlist_node *hnode)
478 return hs->hs_ops->hs_keycmp(key, hnode);
482 cfs_hash_object(struct cfs_hash *hs, struct hlist_node *hnode)
484 return hs->hs_ops->hs_object(hnode);
488 cfs_hash_get(struct cfs_hash *hs, struct hlist_node *hnode)
490 return hs->hs_ops->hs_get(hs, hnode);
494 cfs_hash_put_locked(struct cfs_hash *hs, struct hlist_node *hnode)
496 return hs->hs_ops->hs_put_locked(hs, hnode);
500 cfs_hash_put(struct cfs_hash *hs, struct hlist_node *hnode)
502 return hs->hs_ops->hs_put(hs, hnode);
506 cfs_hash_exit(struct cfs_hash *hs, struct hlist_node *hnode)
508 if (hs->hs_ops->hs_exit)
509 hs->hs_ops->hs_exit(hs, hnode);
512 static inline void cfs_hash_lock(struct cfs_hash *hs, int excl)
514 hs->hs_lops->hs_lock(&hs->hs_lock, excl);
517 static inline void cfs_hash_unlock(struct cfs_hash *hs, int excl)
519 hs->hs_lops->hs_unlock(&hs->hs_lock, excl);
522 static inline int cfs_hash_dec_and_lock(struct cfs_hash *hs,
525 LASSERT(cfs_hash_with_no_bktlock(hs));
526 return atomic_dec_and_lock(condition, &hs->hs_lock.spin);
529 static inline void cfs_hash_bd_lock(struct cfs_hash *hs,
530 struct cfs_hash_bd *bd, int excl)
532 hs->hs_lops->hs_bkt_lock(&bd->bd_bucket->hsb_lock, excl);
535 static inline void cfs_hash_bd_unlock(struct cfs_hash *hs,
536 struct cfs_hash_bd *bd, int excl)
538 hs->hs_lops->hs_bkt_unlock(&bd->bd_bucket->hsb_lock, excl);
542 * operations on cfs_hash bucket (bd: bucket descriptor),
543 * they are normally for hash-table without rehash
545 void cfs_hash_bd_get(struct cfs_hash *hs, const void *key,
546 struct cfs_hash_bd *bd);
549 cfs_hash_bd_get_and_lock(struct cfs_hash *hs, const void *key,
550 struct cfs_hash_bd *bd, int excl)
552 cfs_hash_bd_get(hs, key, bd);
553 cfs_hash_bd_lock(hs, bd, excl);
556 static inline unsigned
557 cfs_hash_bd_index_get(struct cfs_hash *hs, struct cfs_hash_bd *bd)
559 return bd->bd_offset | (bd->bd_bucket->hsb_index << hs->hs_bkt_bits);
563 cfs_hash_bd_index_set(struct cfs_hash *hs, unsigned index,
564 struct cfs_hash_bd *bd)
566 bd->bd_bucket = hs->hs_buckets[index >> hs->hs_bkt_bits];
567 bd->bd_offset = index & (CFS_HASH_BKT_NHLIST(hs) - 1U);
571 cfs_hash_bd_extra_get(struct cfs_hash *hs, struct cfs_hash_bd *bd)
573 return (void *)bd->bd_bucket +
574 cfs_hash_bkt_size(hs) - hs->hs_extra_bytes;
578 cfs_hash_bd_version_get(struct cfs_hash_bd *bd)
580 /* need hold cfs_hash_bd_lock */
581 return bd->bd_bucket->hsb_version;
585 cfs_hash_bd_count_get(struct cfs_hash_bd *bd)
587 /* need hold cfs_hash_bd_lock */
588 return bd->bd_bucket->hsb_count;
592 cfs_hash_bd_depmax_get(struct cfs_hash_bd *bd)
594 return bd->bd_bucket->hsb_depmax;
598 cfs_hash_bd_compare(struct cfs_hash_bd *bd1, struct cfs_hash_bd *bd2)
600 if (bd1->bd_bucket->hsb_index != bd2->bd_bucket->hsb_index)
601 return bd1->bd_bucket->hsb_index - bd2->bd_bucket->hsb_index;
603 if (bd1->bd_offset != bd2->bd_offset)
604 return bd1->bd_offset - bd2->bd_offset;
609 void cfs_hash_bd_add_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd,
610 struct hlist_node *hnode);
611 void cfs_hash_bd_del_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd,
612 struct hlist_node *hnode);
613 void cfs_hash_bd_move_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd_old,
614 struct cfs_hash_bd *bd_new,
615 struct hlist_node *hnode);
618 cfs_hash_bd_dec_and_lock(struct cfs_hash *hs, struct cfs_hash_bd *bd,
621 LASSERT(cfs_hash_with_spin_bktlock(hs));
622 return atomic_dec_and_lock(condition, &bd->bd_bucket->hsb_lock.spin);
625 static inline struct hlist_head *
626 cfs_hash_bd_hhead(struct cfs_hash *hs, struct cfs_hash_bd *bd)
628 return hs->hs_hops->hop_hhead(hs, bd);
632 cfs_hash_bd_lookup_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd,
635 cfs_hash_bd_peek_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd,
638 cfs_hash_bd_findadd_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd,
639 const void *key, struct hlist_node *hnode,
642 cfs_hash_bd_finddel_locked(struct cfs_hash *hs, struct cfs_hash_bd *bd,
643 const void *key, struct hlist_node *hnode);
646 * operations on cfs_hash bucket (bd: bucket descriptor),
647 * they are safe for hash-table with rehash
649 void cfs_hash_dual_bd_get(struct cfs_hash *hs, const void *key,
650 struct cfs_hash_bd *bds);
651 void cfs_hash_dual_bd_lock(struct cfs_hash *hs, struct cfs_hash_bd *bds,
653 void cfs_hash_dual_bd_unlock(struct cfs_hash *hs, struct cfs_hash_bd *bds,
657 cfs_hash_dual_bd_get_and_lock(struct cfs_hash *hs, const void *key,
658 struct cfs_hash_bd *bds, int excl)
660 cfs_hash_dual_bd_get(hs, key, bds);
661 cfs_hash_dual_bd_lock(hs, bds, excl);
665 cfs_hash_dual_bd_lookup_locked(struct cfs_hash *hs, struct cfs_hash_bd *bds,
668 cfs_hash_dual_bd_findadd_locked(struct cfs_hash *hs, struct cfs_hash_bd *bds,
669 const void *key, struct hlist_node *hnode,
672 cfs_hash_dual_bd_finddel_locked(struct cfs_hash *hs, struct cfs_hash_bd *bds,
673 const void *key, struct hlist_node *hnode);
675 /* Hash init/cleanup functions */
677 cfs_hash_create(char *name, unsigned cur_bits, unsigned max_bits,
678 unsigned bkt_bits, unsigned extra_bytes,
679 unsigned min_theta, unsigned max_theta,
680 struct cfs_hash_ops *ops, unsigned flags);
682 struct cfs_hash *cfs_hash_getref(struct cfs_hash *hs);
683 void cfs_hash_putref(struct cfs_hash *hs);
685 /* Hash addition functions */
686 void cfs_hash_add(struct cfs_hash *hs, const void *key,
687 struct hlist_node *hnode);
688 int cfs_hash_add_unique(struct cfs_hash *hs, const void *key,
689 struct hlist_node *hnode);
690 void *cfs_hash_findadd_unique(struct cfs_hash *hs, const void *key,
691 struct hlist_node *hnode);
693 /* Hash deletion functions */
694 void *cfs_hash_del(struct cfs_hash *hs, const void *key,
695 struct hlist_node *hnode);
696 void *cfs_hash_del_key(struct cfs_hash *hs, const void *key);
698 /* Hash lookup/for_each functions */
699 #define CFS_HASH_LOOP_HOG 1024
701 typedef int (*cfs_hash_for_each_cb_t)(struct cfs_hash *hs,
702 struct cfs_hash_bd *bd,
703 struct hlist_node *node,
706 cfs_hash_lookup(struct cfs_hash *hs, const void *key);
708 cfs_hash_for_each(struct cfs_hash *hs, cfs_hash_for_each_cb_t, void *data);
710 cfs_hash_for_each_safe(struct cfs_hash *hs, cfs_hash_for_each_cb_t, void *data);
712 cfs_hash_for_each_nolock(struct cfs_hash *hs, cfs_hash_for_each_cb_t,
713 void *data, int start);
715 cfs_hash_for_each_empty(struct cfs_hash *hs, cfs_hash_for_each_cb_t,
718 cfs_hash_for_each_key(struct cfs_hash *hs, const void *key,
719 cfs_hash_for_each_cb_t, void *data);
720 typedef int (*cfs_hash_cond_opt_cb_t)(void *obj, void *data);
722 cfs_hash_cond_del(struct cfs_hash *hs, cfs_hash_cond_opt_cb_t, void *data);
725 cfs_hash_hlist_for_each(struct cfs_hash *hs, unsigned hindex,
726 cfs_hash_for_each_cb_t, void *data);
727 int cfs_hash_is_empty(struct cfs_hash *hs);
728 __u64 cfs_hash_size_get(struct cfs_hash *hs);
731 * Rehash - Theta is calculated to be the average chained
732 * hash depth assuming a perfectly uniform hash function.
734 void cfs_hash_rehash_cancel_locked(struct cfs_hash *hs);
735 void cfs_hash_rehash_cancel(struct cfs_hash *hs);
736 int cfs_hash_rehash(struct cfs_hash *hs, int do_rehash);
737 void cfs_hash_rehash_key(struct cfs_hash *hs, const void *old_key,
738 void *new_key, struct hlist_node *hnode);
740 #if CFS_HASH_DEBUG_LEVEL > CFS_HASH_DEBUG_1
741 /* Validate hnode references the correct key */
743 cfs_hash_key_validate(struct cfs_hash *hs, const void *key,
744 struct hlist_node *hnode)
746 LASSERT(cfs_hash_keycmp(hs, key, hnode));
749 /* Validate hnode is in the correct bucket */
751 cfs_hash_bucket_validate(struct cfs_hash *hs, struct cfs_hash_bd *bd,
752 struct hlist_node *hnode)
754 struct cfs_hash_bd bds[2];
756 cfs_hash_dual_bd_get(hs, cfs_hash_key(hs, hnode), bds);
757 LASSERT(bds[0].bd_bucket == bd->bd_bucket ||
758 bds[1].bd_bucket == bd->bd_bucket);
761 #else /* CFS_HASH_DEBUG_LEVEL > CFS_HASH_DEBUG_1 */
764 cfs_hash_key_validate(struct cfs_hash *hs, const void *key,
765 struct hlist_node *hnode) {}
768 cfs_hash_bucket_validate(struct cfs_hash *hs, struct cfs_hash_bd *bd,
769 struct hlist_node *hnode) {}
771 #endif /* CFS_HASH_DEBUG_LEVEL */
773 #define CFS_HASH_THETA_BITS 10
774 #define CFS_HASH_MIN_THETA (1U << (CFS_HASH_THETA_BITS - 1))
775 #define CFS_HASH_MAX_THETA (1U << (CFS_HASH_THETA_BITS + 1))
777 /* Return integer component of theta */
778 static inline int __cfs_hash_theta_int(int theta)
780 return (theta >> CFS_HASH_THETA_BITS);
783 /* Return a fractional value between 0 and 999 */
784 static inline int __cfs_hash_theta_frac(int theta)
786 return ((theta * 1000) >> CFS_HASH_THETA_BITS) -
787 (__cfs_hash_theta_int(theta) * 1000);
790 static inline int __cfs_hash_theta(struct cfs_hash *hs)
792 return (atomic_read(&hs->hs_count) <<
793 CFS_HASH_THETA_BITS) >> hs->hs_cur_bits;
797 __cfs_hash_set_theta(struct cfs_hash *hs, int min, int max)
800 hs->hs_min_theta = (__u16)min;
801 hs->hs_max_theta = (__u16)max;
804 /* Generic debug formatting routines mainly for proc handler */
806 void cfs_hash_debug_header(struct seq_file *m);
807 void cfs_hash_debug_str(struct cfs_hash *hs, struct seq_file *m);
810 * Generic djb2 hash algorithm for character arrays.
812 static inline unsigned
813 cfs_hash_djb2_hash(const void *key, size_t size, unsigned mask)
815 unsigned i, hash = 5381;
817 LASSERT(key != NULL);
819 for (i = 0; i < size; i++)
820 hash = hash * 33 + ((char *)key)[i];
822 return (hash & mask);
826 * Generic u32 hash algorithm.
828 static inline unsigned
829 cfs_hash_u32_hash(const __u32 key, unsigned mask)
831 return ((key * CFS_GOLDEN_RATIO_PRIME_32) & mask);
835 * Generic u64 hash algorithm.
837 static inline unsigned
838 cfs_hash_u64_hash(const __u64 key, unsigned mask)
840 return ((unsigned)(key * CFS_GOLDEN_RATIO_PRIME_64) & mask);
843 /** iterate over all buckets in @bds (array of struct cfs_hash_bd) */
844 #define cfs_hash_for_each_bd(bds, n, i) \
845 for (i = 0; i < n && (bds)[i].bd_bucket != NULL; i++)
847 /** iterate over all buckets of @hs */
848 #define cfs_hash_for_each_bucket(hs, bd, pos) \
850 pos < CFS_HASH_NBKT(hs) && \
851 ((bd)->bd_bucket = (hs)->hs_buckets[pos]) != NULL; pos++)
853 /** iterate over all hlist of bucket @bd */
854 #define cfs_hash_bd_for_each_hlist(hs, bd, hlist) \
855 for ((bd)->bd_offset = 0; \
856 (bd)->bd_offset < CFS_HASH_BKT_NHLIST(hs) && \
857 (hlist = cfs_hash_bd_hhead(hs, bd)) != NULL; \
860 /* !__LIBCFS__HASH_H__ */