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![Steve Hodgson](/assets/img/avatar_default.png)
The btree_for_each API is implemented with macros that internally call btree_get_prev(), so if btree_get_prev() isn't exported then modules fail to link if they try to use one of the btree_for_each macros. Since the rest of the btree API is exported, we should keep things orthogonal and make this work too. Signed-off-by: Roland Dreier <roland@purestorage.com> Signed-off-by: Steve Hodgson <steve@purestorage.com> Acked-by: Joern Engel <joern@logfs.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
799 lines
19 KiB
C
799 lines
19 KiB
C
/*
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* lib/btree.c - Simple In-memory B+Tree
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*
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* As should be obvious for Linux kernel code, license is GPLv2
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*
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* Copyright (c) 2007-2008 Joern Engel <joern@logfs.org>
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* Bits and pieces stolen from Peter Zijlstra's code, which is
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* Copyright 2007, Red Hat Inc. Peter Zijlstra <pzijlstr@redhat.com>
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* GPLv2
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*
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* see http://programming.kicks-ass.net/kernel-patches/vma_lookup/btree.patch
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*
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* A relatively simple B+Tree implementation. I have written it as a learning
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* exercise to understand how B+Trees work. Turned out to be useful as well.
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*
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* B+Trees can be used similar to Linux radix trees (which don't have anything
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* in common with textbook radix trees, beware). Prerequisite for them working
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* well is that access to a random tree node is much faster than a large number
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* of operations within each node.
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*
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* Disks have fulfilled the prerequisite for a long time. More recently DRAM
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* has gained similar properties, as memory access times, when measured in cpu
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* cycles, have increased. Cacheline sizes have increased as well, which also
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* helps B+Trees.
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*
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* Compared to radix trees, B+Trees are more efficient when dealing with a
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* sparsely populated address space. Between 25% and 50% of the memory is
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* occupied with valid pointers. When densely populated, radix trees contain
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* ~98% pointers - hard to beat. Very sparse radix trees contain only ~2%
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* pointers.
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*
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* This particular implementation stores pointers identified by a long value.
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* Storing NULL pointers is illegal, lookup will return NULL when no entry
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* was found.
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*
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* A tricks was used that is not commonly found in textbooks. The lowest
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* values are to the right, not to the left. All used slots within a node
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* are on the left, all unused slots contain NUL values. Most operations
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* simply loop once over all slots and terminate on the first NUL.
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*/
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#include <linux/btree.h>
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#include <linux/cache.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#define MAX(a, b) ((a) > (b) ? (a) : (b))
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#define NODESIZE MAX(L1_CACHE_BYTES, 128)
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struct btree_geo {
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int keylen;
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int no_pairs;
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int no_longs;
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};
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struct btree_geo btree_geo32 = {
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.keylen = 1,
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.no_pairs = NODESIZE / sizeof(long) / 2,
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.no_longs = NODESIZE / sizeof(long) / 2,
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};
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EXPORT_SYMBOL_GPL(btree_geo32);
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#define LONG_PER_U64 (64 / BITS_PER_LONG)
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struct btree_geo btree_geo64 = {
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.keylen = LONG_PER_U64,
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.no_pairs = NODESIZE / sizeof(long) / (1 + LONG_PER_U64),
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.no_longs = LONG_PER_U64 * (NODESIZE / sizeof(long) / (1 + LONG_PER_U64)),
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};
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EXPORT_SYMBOL_GPL(btree_geo64);
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struct btree_geo btree_geo128 = {
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.keylen = 2 * LONG_PER_U64,
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.no_pairs = NODESIZE / sizeof(long) / (1 + 2 * LONG_PER_U64),
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.no_longs = 2 * LONG_PER_U64 * (NODESIZE / sizeof(long) / (1 + 2 * LONG_PER_U64)),
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};
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EXPORT_SYMBOL_GPL(btree_geo128);
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static struct kmem_cache *btree_cachep;
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void *btree_alloc(gfp_t gfp_mask, void *pool_data)
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{
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return kmem_cache_alloc(btree_cachep, gfp_mask);
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}
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EXPORT_SYMBOL_GPL(btree_alloc);
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void btree_free(void *element, void *pool_data)
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{
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kmem_cache_free(btree_cachep, element);
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}
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EXPORT_SYMBOL_GPL(btree_free);
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static unsigned long *btree_node_alloc(struct btree_head *head, gfp_t gfp)
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{
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unsigned long *node;
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node = mempool_alloc(head->mempool, gfp);
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if (likely(node))
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memset(node, 0, NODESIZE);
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return node;
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}
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static int longcmp(const unsigned long *l1, const unsigned long *l2, size_t n)
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{
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size_t i;
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for (i = 0; i < n; i++) {
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if (l1[i] < l2[i])
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return -1;
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if (l1[i] > l2[i])
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return 1;
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}
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return 0;
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}
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static unsigned long *longcpy(unsigned long *dest, const unsigned long *src,
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size_t n)
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{
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size_t i;
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for (i = 0; i < n; i++)
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dest[i] = src[i];
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return dest;
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}
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static unsigned long *longset(unsigned long *s, unsigned long c, size_t n)
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{
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size_t i;
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for (i = 0; i < n; i++)
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s[i] = c;
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return s;
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}
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static void dec_key(struct btree_geo *geo, unsigned long *key)
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{
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unsigned long val;
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int i;
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for (i = geo->keylen - 1; i >= 0; i--) {
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val = key[i];
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key[i] = val - 1;
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if (val)
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break;
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}
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}
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static unsigned long *bkey(struct btree_geo *geo, unsigned long *node, int n)
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{
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return &node[n * geo->keylen];
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}
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static void *bval(struct btree_geo *geo, unsigned long *node, int n)
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{
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return (void *)node[geo->no_longs + n];
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}
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static void setkey(struct btree_geo *geo, unsigned long *node, int n,
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unsigned long *key)
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{
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longcpy(bkey(geo, node, n), key, geo->keylen);
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}
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static void setval(struct btree_geo *geo, unsigned long *node, int n,
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void *val)
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{
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node[geo->no_longs + n] = (unsigned long) val;
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}
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static void clearpair(struct btree_geo *geo, unsigned long *node, int n)
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{
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longset(bkey(geo, node, n), 0, geo->keylen);
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node[geo->no_longs + n] = 0;
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}
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static inline void __btree_init(struct btree_head *head)
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{
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head->node = NULL;
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head->height = 0;
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}
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void btree_init_mempool(struct btree_head *head, mempool_t *mempool)
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{
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__btree_init(head);
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head->mempool = mempool;
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}
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EXPORT_SYMBOL_GPL(btree_init_mempool);
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int btree_init(struct btree_head *head)
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{
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__btree_init(head);
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head->mempool = mempool_create(0, btree_alloc, btree_free, NULL);
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if (!head->mempool)
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return -ENOMEM;
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return 0;
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}
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EXPORT_SYMBOL_GPL(btree_init);
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void btree_destroy(struct btree_head *head)
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{
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mempool_destroy(head->mempool);
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head->mempool = NULL;
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}
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EXPORT_SYMBOL_GPL(btree_destroy);
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void *btree_last(struct btree_head *head, struct btree_geo *geo,
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unsigned long *key)
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{
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int height = head->height;
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unsigned long *node = head->node;
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if (height == 0)
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return NULL;
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for ( ; height > 1; height--)
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node = bval(geo, node, 0);
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longcpy(key, bkey(geo, node, 0), geo->keylen);
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return bval(geo, node, 0);
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}
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EXPORT_SYMBOL_GPL(btree_last);
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static int keycmp(struct btree_geo *geo, unsigned long *node, int pos,
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unsigned long *key)
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{
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return longcmp(bkey(geo, node, pos), key, geo->keylen);
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}
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static int keyzero(struct btree_geo *geo, unsigned long *key)
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{
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int i;
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for (i = 0; i < geo->keylen; i++)
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if (key[i])
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return 0;
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return 1;
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}
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void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
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unsigned long *key)
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{
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int i, height = head->height;
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unsigned long *node = head->node;
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if (height == 0)
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return NULL;
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for ( ; height > 1; height--) {
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for (i = 0; i < geo->no_pairs; i++)
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if (keycmp(geo, node, i, key) <= 0)
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break;
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if (i == geo->no_pairs)
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return NULL;
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node = bval(geo, node, i);
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if (!node)
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return NULL;
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}
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if (!node)
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return NULL;
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for (i = 0; i < geo->no_pairs; i++)
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if (keycmp(geo, node, i, key) == 0)
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return bval(geo, node, i);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(btree_lookup);
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int btree_update(struct btree_head *head, struct btree_geo *geo,
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unsigned long *key, void *val)
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{
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int i, height = head->height;
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unsigned long *node = head->node;
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if (height == 0)
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return -ENOENT;
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for ( ; height > 1; height--) {
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for (i = 0; i < geo->no_pairs; i++)
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if (keycmp(geo, node, i, key) <= 0)
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break;
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if (i == geo->no_pairs)
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return -ENOENT;
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node = bval(geo, node, i);
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if (!node)
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return -ENOENT;
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}
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if (!node)
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return -ENOENT;
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for (i = 0; i < geo->no_pairs; i++)
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if (keycmp(geo, node, i, key) == 0) {
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setval(geo, node, i, val);
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return 0;
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}
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return -ENOENT;
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}
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EXPORT_SYMBOL_GPL(btree_update);
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/*
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* Usually this function is quite similar to normal lookup. But the key of
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* a parent node may be smaller than the smallest key of all its siblings.
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* In such a case we cannot just return NULL, as we have only proven that no
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* key smaller than __key, but larger than this parent key exists.
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* So we set __key to the parent key and retry. We have to use the smallest
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* such parent key, which is the last parent key we encountered.
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*/
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void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
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unsigned long *__key)
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{
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int i, height;
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unsigned long *node, *oldnode;
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unsigned long *retry_key = NULL, key[geo->keylen];
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if (keyzero(geo, __key))
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return NULL;
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if (head->height == 0)
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return NULL;
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retry:
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longcpy(key, __key, geo->keylen);
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dec_key(geo, key);
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node = head->node;
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for (height = head->height ; height > 1; height--) {
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for (i = 0; i < geo->no_pairs; i++)
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if (keycmp(geo, node, i, key) <= 0)
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break;
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if (i == geo->no_pairs)
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goto miss;
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oldnode = node;
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node = bval(geo, node, i);
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if (!node)
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goto miss;
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retry_key = bkey(geo, oldnode, i);
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}
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if (!node)
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goto miss;
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for (i = 0; i < geo->no_pairs; i++) {
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if (keycmp(geo, node, i, key) <= 0) {
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if (bval(geo, node, i)) {
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longcpy(__key, bkey(geo, node, i), geo->keylen);
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return bval(geo, node, i);
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} else
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goto miss;
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}
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}
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miss:
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if (retry_key) {
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__key = retry_key;
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retry_key = NULL;
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goto retry;
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}
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return NULL;
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}
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EXPORT_SYMBOL_GPL(btree_get_prev);
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static int getpos(struct btree_geo *geo, unsigned long *node,
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unsigned long *key)
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{
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int i;
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for (i = 0; i < geo->no_pairs; i++) {
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if (keycmp(geo, node, i, key) <= 0)
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break;
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}
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return i;
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}
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static int getfill(struct btree_geo *geo, unsigned long *node, int start)
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{
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int i;
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for (i = start; i < geo->no_pairs; i++)
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if (!bval(geo, node, i))
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break;
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return i;
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}
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/*
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* locate the correct leaf node in the btree
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*/
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static unsigned long *find_level(struct btree_head *head, struct btree_geo *geo,
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unsigned long *key, int level)
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{
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unsigned long *node = head->node;
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int i, height;
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for (height = head->height; height > level; height--) {
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for (i = 0; i < geo->no_pairs; i++)
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if (keycmp(geo, node, i, key) <= 0)
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break;
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if ((i == geo->no_pairs) || !bval(geo, node, i)) {
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/* right-most key is too large, update it */
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/* FIXME: If the right-most key on higher levels is
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* always zero, this wouldn't be necessary. */
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i--;
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setkey(geo, node, i, key);
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}
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BUG_ON(i < 0);
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node = bval(geo, node, i);
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}
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BUG_ON(!node);
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return node;
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}
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static int btree_grow(struct btree_head *head, struct btree_geo *geo,
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gfp_t gfp)
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{
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unsigned long *node;
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int fill;
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node = btree_node_alloc(head, gfp);
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if (!node)
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return -ENOMEM;
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if (head->node) {
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fill = getfill(geo, head->node, 0);
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setkey(geo, node, 0, bkey(geo, head->node, fill - 1));
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setval(geo, node, 0, head->node);
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}
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head->node = node;
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head->height++;
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return 0;
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}
|
|
|
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static void btree_shrink(struct btree_head *head, struct btree_geo *geo)
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{
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unsigned long *node;
|
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int fill;
|
|
|
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if (head->height <= 1)
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return;
|
|
|
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node = head->node;
|
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fill = getfill(geo, node, 0);
|
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BUG_ON(fill > 1);
|
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head->node = bval(geo, node, 0);
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head->height--;
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mempool_free(node, head->mempool);
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}
|
|
|
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static int btree_insert_level(struct btree_head *head, struct btree_geo *geo,
|
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unsigned long *key, void *val, int level,
|
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gfp_t gfp)
|
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{
|
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unsigned long *node;
|
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int i, pos, fill, err;
|
|
|
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BUG_ON(!val);
|
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if (head->height < level) {
|
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err = btree_grow(head, geo, gfp);
|
|
if (err)
|
|
return err;
|
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}
|
|
|
|
retry:
|
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node = find_level(head, geo, key, level);
|
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pos = getpos(geo, node, key);
|
|
fill = getfill(geo, node, pos);
|
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/* two identical keys are not allowed */
|
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BUG_ON(pos < fill && keycmp(geo, node, pos, key) == 0);
|
|
|
|
if (fill == geo->no_pairs) {
|
|
/* need to split node */
|
|
unsigned long *new;
|
|
|
|
new = btree_node_alloc(head, gfp);
|
|
if (!new)
|
|
return -ENOMEM;
|
|
err = btree_insert_level(head, geo,
|
|
bkey(geo, node, fill / 2 - 1),
|
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new, level + 1, gfp);
|
|
if (err) {
|
|
mempool_free(new, head->mempool);
|
|
return err;
|
|
}
|
|
for (i = 0; i < fill / 2; i++) {
|
|
setkey(geo, new, i, bkey(geo, node, i));
|
|
setval(geo, new, i, bval(geo, node, i));
|
|
setkey(geo, node, i, bkey(geo, node, i + fill / 2));
|
|
setval(geo, node, i, bval(geo, node, i + fill / 2));
|
|
clearpair(geo, node, i + fill / 2);
|
|
}
|
|
if (fill & 1) {
|
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setkey(geo, node, i, bkey(geo, node, fill - 1));
|
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setval(geo, node, i, bval(geo, node, fill - 1));
|
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clearpair(geo, node, fill - 1);
|
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}
|
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goto retry;
|
|
}
|
|
BUG_ON(fill >= geo->no_pairs);
|
|
|
|
/* shift and insert */
|
|
for (i = fill; i > pos; i--) {
|
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setkey(geo, node, i, bkey(geo, node, i - 1));
|
|
setval(geo, node, i, bval(geo, node, i - 1));
|
|
}
|
|
setkey(geo, node, pos, key);
|
|
setval(geo, node, pos, val);
|
|
|
|
return 0;
|
|
}
|
|
|
|
int btree_insert(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long *key, void *val, gfp_t gfp)
|
|
{
|
|
return btree_insert_level(head, geo, key, val, 1, gfp);
|
|
}
|
|
EXPORT_SYMBOL_GPL(btree_insert);
|
|
|
|
static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long *key, int level);
|
|
static void merge(struct btree_head *head, struct btree_geo *geo, int level,
|
|
unsigned long *left, int lfill,
|
|
unsigned long *right, int rfill,
|
|
unsigned long *parent, int lpos)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < rfill; i++) {
|
|
/* Move all keys to the left */
|
|
setkey(geo, left, lfill + i, bkey(geo, right, i));
|
|
setval(geo, left, lfill + i, bval(geo, right, i));
|
|
}
|
|
/* Exchange left and right child in parent */
|
|
setval(geo, parent, lpos, right);
|
|
setval(geo, parent, lpos + 1, left);
|
|
/* Remove left (formerly right) child from parent */
|
|
btree_remove_level(head, geo, bkey(geo, parent, lpos), level + 1);
|
|
mempool_free(right, head->mempool);
|
|
}
|
|
|
|
static void rebalance(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long *key, int level, unsigned long *child, int fill)
|
|
{
|
|
unsigned long *parent, *left = NULL, *right = NULL;
|
|
int i, no_left, no_right;
|
|
|
|
if (fill == 0) {
|
|
/* Because we don't steal entries from a neighbour, this case
|
|
* can happen. Parent node contains a single child, this
|
|
* node, so merging with a sibling never happens.
|
|
*/
|
|
btree_remove_level(head, geo, key, level + 1);
|
|
mempool_free(child, head->mempool);
|
|
return;
|
|
}
|
|
|
|
parent = find_level(head, geo, key, level + 1);
|
|
i = getpos(geo, parent, key);
|
|
BUG_ON(bval(geo, parent, i) != child);
|
|
|
|
if (i > 0) {
|
|
left = bval(geo, parent, i - 1);
|
|
no_left = getfill(geo, left, 0);
|
|
if (fill + no_left <= geo->no_pairs) {
|
|
merge(head, geo, level,
|
|
left, no_left,
|
|
child, fill,
|
|
parent, i - 1);
|
|
return;
|
|
}
|
|
}
|
|
if (i + 1 < getfill(geo, parent, i)) {
|
|
right = bval(geo, parent, i + 1);
|
|
no_right = getfill(geo, right, 0);
|
|
if (fill + no_right <= geo->no_pairs) {
|
|
merge(head, geo, level,
|
|
child, fill,
|
|
right, no_right,
|
|
parent, i);
|
|
return;
|
|
}
|
|
}
|
|
/*
|
|
* We could also try to steal one entry from the left or right
|
|
* neighbor. By not doing so we changed the invariant from
|
|
* "all nodes are at least half full" to "no two neighboring
|
|
* nodes can be merged". Which means that the average fill of
|
|
* all nodes is still half or better.
|
|
*/
|
|
}
|
|
|
|
static void *btree_remove_level(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long *key, int level)
|
|
{
|
|
unsigned long *node;
|
|
int i, pos, fill;
|
|
void *ret;
|
|
|
|
if (level > head->height) {
|
|
/* we recursed all the way up */
|
|
head->height = 0;
|
|
head->node = NULL;
|
|
return NULL;
|
|
}
|
|
|
|
node = find_level(head, geo, key, level);
|
|
pos = getpos(geo, node, key);
|
|
fill = getfill(geo, node, pos);
|
|
if ((level == 1) && (keycmp(geo, node, pos, key) != 0))
|
|
return NULL;
|
|
ret = bval(geo, node, pos);
|
|
|
|
/* remove and shift */
|
|
for (i = pos; i < fill - 1; i++) {
|
|
setkey(geo, node, i, bkey(geo, node, i + 1));
|
|
setval(geo, node, i, bval(geo, node, i + 1));
|
|
}
|
|
clearpair(geo, node, fill - 1);
|
|
|
|
if (fill - 1 < geo->no_pairs / 2) {
|
|
if (level < head->height)
|
|
rebalance(head, geo, key, level, node, fill - 1);
|
|
else if (fill - 1 == 1)
|
|
btree_shrink(head, geo);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
void *btree_remove(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long *key)
|
|
{
|
|
if (head->height == 0)
|
|
return NULL;
|
|
|
|
return btree_remove_level(head, geo, key, 1);
|
|
}
|
|
EXPORT_SYMBOL_GPL(btree_remove);
|
|
|
|
int btree_merge(struct btree_head *target, struct btree_head *victim,
|
|
struct btree_geo *geo, gfp_t gfp)
|
|
{
|
|
unsigned long key[geo->keylen];
|
|
unsigned long dup[geo->keylen];
|
|
void *val;
|
|
int err;
|
|
|
|
BUG_ON(target == victim);
|
|
|
|
if (!(target->node)) {
|
|
/* target is empty, just copy fields over */
|
|
target->node = victim->node;
|
|
target->height = victim->height;
|
|
__btree_init(victim);
|
|
return 0;
|
|
}
|
|
|
|
/* TODO: This needs some optimizations. Currently we do three tree
|
|
* walks to remove a single object from the victim.
|
|
*/
|
|
for (;;) {
|
|
if (!btree_last(victim, geo, key))
|
|
break;
|
|
val = btree_lookup(victim, geo, key);
|
|
err = btree_insert(target, geo, key, val, gfp);
|
|
if (err)
|
|
return err;
|
|
/* We must make a copy of the key, as the original will get
|
|
* mangled inside btree_remove. */
|
|
longcpy(dup, key, geo->keylen);
|
|
btree_remove(victim, geo, dup);
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(btree_merge);
|
|
|
|
static size_t __btree_for_each(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long *node, unsigned long opaque,
|
|
void (*func)(void *elem, unsigned long opaque,
|
|
unsigned long *key, size_t index,
|
|
void *func2),
|
|
void *func2, int reap, int height, size_t count)
|
|
{
|
|
int i;
|
|
unsigned long *child;
|
|
|
|
for (i = 0; i < geo->no_pairs; i++) {
|
|
child = bval(geo, node, i);
|
|
if (!child)
|
|
break;
|
|
if (height > 1)
|
|
count = __btree_for_each(head, geo, child, opaque,
|
|
func, func2, reap, height - 1, count);
|
|
else
|
|
func(child, opaque, bkey(geo, node, i), count++,
|
|
func2);
|
|
}
|
|
if (reap)
|
|
mempool_free(node, head->mempool);
|
|
return count;
|
|
}
|
|
|
|
static void empty(void *elem, unsigned long opaque, unsigned long *key,
|
|
size_t index, void *func2)
|
|
{
|
|
}
|
|
|
|
void visitorl(void *elem, unsigned long opaque, unsigned long *key,
|
|
size_t index, void *__func)
|
|
{
|
|
visitorl_t func = __func;
|
|
|
|
func(elem, opaque, *key, index);
|
|
}
|
|
EXPORT_SYMBOL_GPL(visitorl);
|
|
|
|
void visitor32(void *elem, unsigned long opaque, unsigned long *__key,
|
|
size_t index, void *__func)
|
|
{
|
|
visitor32_t func = __func;
|
|
u32 *key = (void *)__key;
|
|
|
|
func(elem, opaque, *key, index);
|
|
}
|
|
EXPORT_SYMBOL_GPL(visitor32);
|
|
|
|
void visitor64(void *elem, unsigned long opaque, unsigned long *__key,
|
|
size_t index, void *__func)
|
|
{
|
|
visitor64_t func = __func;
|
|
u64 *key = (void *)__key;
|
|
|
|
func(elem, opaque, *key, index);
|
|
}
|
|
EXPORT_SYMBOL_GPL(visitor64);
|
|
|
|
void visitor128(void *elem, unsigned long opaque, unsigned long *__key,
|
|
size_t index, void *__func)
|
|
{
|
|
visitor128_t func = __func;
|
|
u64 *key = (void *)__key;
|
|
|
|
func(elem, opaque, key[0], key[1], index);
|
|
}
|
|
EXPORT_SYMBOL_GPL(visitor128);
|
|
|
|
size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long opaque,
|
|
void (*func)(void *elem, unsigned long opaque,
|
|
unsigned long *key,
|
|
size_t index, void *func2),
|
|
void *func2)
|
|
{
|
|
size_t count = 0;
|
|
|
|
if (!func2)
|
|
func = empty;
|
|
if (head->node)
|
|
count = __btree_for_each(head, geo, head->node, opaque, func,
|
|
func2, 0, head->height, 0);
|
|
return count;
|
|
}
|
|
EXPORT_SYMBOL_GPL(btree_visitor);
|
|
|
|
size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
|
|
unsigned long opaque,
|
|
void (*func)(void *elem, unsigned long opaque,
|
|
unsigned long *key,
|
|
size_t index, void *func2),
|
|
void *func2)
|
|
{
|
|
size_t count = 0;
|
|
|
|
if (!func2)
|
|
func = empty;
|
|
if (head->node)
|
|
count = __btree_for_each(head, geo, head->node, opaque, func,
|
|
func2, 1, head->height, 0);
|
|
__btree_init(head);
|
|
return count;
|
|
}
|
|
EXPORT_SYMBOL_GPL(btree_grim_visitor);
|
|
|
|
static int __init btree_module_init(void)
|
|
{
|
|
btree_cachep = kmem_cache_create("btree_node", NODESIZE, 0,
|
|
SLAB_HWCACHE_ALIGN, NULL);
|
|
return 0;
|
|
}
|
|
|
|
static void __exit btree_module_exit(void)
|
|
{
|
|
kmem_cache_destroy(btree_cachep);
|
|
}
|
|
|
|
/* If core code starts using btree, initialization should happen even earlier */
|
|
module_init(btree_module_init);
|
|
module_exit(btree_module_exit);
|
|
|
|
MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
|
|
MODULE_AUTHOR("Johannes Berg <johannes@sipsolutions.net>");
|
|
MODULE_LICENSE("GPL");
|