/* SPDX-License-Identifier: GPL-2.0 */ #ifndef BTREE_H #define BTREE_H #include <linux/kernel.h> #include <linux/mempool.h> /** * DOC: B+Tree basics * * A B+Tree is a data structure for looking up arbitrary (currently allowing * unsigned long, u32, u64 and 2 * u64) keys into pointers. The data structure * is described at https://en.wikipedia.org/wiki/B-tree, we currently do not * use binary search to find the key on lookups. * * Each B+Tree consists of a head, that contains bookkeeping information and * a variable number (starting with zero) nodes. Each node contains the keys * and pointers to sub-nodes, or, for leaf nodes, the keys and values for the * tree entries. * * Each node in this implementation has the following layout: * [key1, key2, ..., keyN] [val1, val2, ..., valN] * * Each key here is an array of unsigned longs, geo->no_longs in total. The * number of keys and values (N) is geo->no_pairs. */ /** * struct btree_head - btree head * * @node: the first node in the tree * @mempool: mempool used for node allocations * @height: current of the tree */ struct btree_head { … }; /* btree geometry */ struct btree_geo; /** * btree_alloc - allocate function for the mempool * @gfp_mask: gfp mask for the allocation * @pool_data: unused */ void *btree_alloc(gfp_t gfp_mask, void *pool_data); /** * btree_free - free function for the mempool * @element: the element to free * @pool_data: unused */ void btree_free(void *element, void *pool_data); /** * btree_init_mempool - initialise a btree with given mempool * * @head: the btree head to initialise * @mempool: the mempool to use * * When this function is used, there is no need to destroy * the mempool. */ void btree_init_mempool(struct btree_head *head, mempool_t *mempool); /** * btree_init - initialise a btree * * @head: the btree head to initialise * * This function allocates the memory pool that the * btree needs. Returns zero or a negative error code * (-%ENOMEM) when memory allocation fails. * */ int __must_check btree_init(struct btree_head *head); /** * btree_destroy - destroy mempool * * @head: the btree head to destroy * * This function destroys the internal memory pool, use only * when using btree_init(), not with btree_init_mempool(). */ void btree_destroy(struct btree_head *head); /** * btree_lookup - look up a key in the btree * * @head: the btree to look in * @geo: the btree geometry * @key: the key to look up * * This function returns the value for the given key, or %NULL. */ void *btree_lookup(struct btree_head *head, struct btree_geo *geo, unsigned long *key); /** * btree_insert - insert an entry into the btree * * @head: the btree to add to * @geo: the btree geometry * @key: the key to add (must not already be present) * @val: the value to add (must not be %NULL) * @gfp: allocation flags for node allocations * * This function returns 0 if the item could be added, or an * error code if it failed (may fail due to memory pressure). */ int __must_check btree_insert(struct btree_head *head, struct btree_geo *geo, unsigned long *key, void *val, gfp_t gfp); /** * btree_update - update an entry in the btree * * @head: the btree to update * @geo: the btree geometry * @key: the key to update * @val: the value to change it to (must not be %NULL) * * This function returns 0 if the update was successful, or * -%ENOENT if the key could not be found. */ int btree_update(struct btree_head *head, struct btree_geo *geo, unsigned long *key, void *val); /** * btree_remove - remove an entry from the btree * * @head: the btree to update * @geo: the btree geometry * @key: the key to remove * * This function returns the removed entry, or %NULL if the key * could not be found. */ void *btree_remove(struct btree_head *head, struct btree_geo *geo, unsigned long *key); /** * btree_merge - merge two btrees * * @target: the tree that gets all the entries * @victim: the tree that gets merged into @target * @geo: the btree geometry * @gfp: allocation flags * * The two trees @target and @victim may not contain the same keys, * that is a bug and triggers a BUG(). This function returns zero * if the trees were merged successfully, and may return a failure * when memory allocation fails, in which case both trees might have * been partially merged, i.e. some entries have been moved from * @victim to @target. */ int btree_merge(struct btree_head *target, struct btree_head *victim, struct btree_geo *geo, gfp_t gfp); /** * btree_last - get last entry in btree * * @head: btree head * @geo: btree geometry * @key: last key * * Returns the last entry in the btree, and sets @key to the key * of that entry; returns NULL if the tree is empty, in that case * key is not changed. */ void *btree_last(struct btree_head *head, struct btree_geo *geo, unsigned long *key); /** * btree_get_prev - get previous entry * * @head: btree head * @geo: btree geometry * @key: pointer to key * * The function returns the next item right before the value pointed to by * @key, and updates @key with its key, or returns %NULL when there is no * entry with a key smaller than the given key. */ void *btree_get_prev(struct btree_head *head, struct btree_geo *geo, unsigned long *key); /* internal use, use btree_visitor{l,32,64,128} */ 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); /* internal use, use btree_grim_visitor{l,32,64,128} */ 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); #include <linux/btree-128.h> extern struct btree_geo btree_geo32; #define BTREE_TYPE_SUFFIX … #define BTREE_TYPE_BITS … #define BTREE_TYPE_GEO … #define BTREE_KEYTYPE … #include <linux/btree-type.h> #define btree_for_each_safel(head, key, val) … #define BTREE_TYPE_SUFFIX … #define BTREE_TYPE_BITS … #define BTREE_TYPE_GEO … #define BTREE_KEYTYPE … #include <linux/btree-type.h> #define btree_for_each_safe32(head, key, val) … extern struct btree_geo btree_geo64; #define BTREE_TYPE_SUFFIX … #define BTREE_TYPE_BITS … #define BTREE_TYPE_GEO … #define BTREE_KEYTYPE … #include <linux/btree-type.h> #define btree_for_each_safe64(head, key, val) … #endif
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