245 lines
6.8 KiB
C
245 lines
6.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BTREE_H
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#define BTREE_H
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#include <linux/kernel.h>
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#include <linux/mempool.h>
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/**
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* DOC: B+Tree basics
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*
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* A B+Tree is a data structure for looking up arbitrary (currently allowing
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* unsigned long, u32, u64 and 2 * u64) keys into pointers. The data structure
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* is described at https://en.wikipedia.org/wiki/B-tree, we currently do not
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* use binary search to find the key on lookups.
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*
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* Each B+Tree consists of a head, that contains bookkeeping information and
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* a variable number (starting with zero) nodes. Each node contains the keys
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* and pointers to sub-nodes, or, for leaf nodes, the keys and values for the
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* tree entries.
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*
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* Each node in this implementation has the following layout:
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* [key1, key2, ..., keyN] [val1, val2, ..., valN]
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*
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* Each key here is an array of unsigned longs, geo->no_longs in total. The
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* number of keys and values (N) is geo->no_pairs.
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*/
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/**
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* struct btree_head - btree head
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*
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* @node: the first node in the tree
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* @mempool: mempool used for node allocations
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* @height: current of the tree
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*/
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struct btree_head {
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unsigned long *node;
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mempool_t *mempool;
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int height;
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};
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/* btree geometry */
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struct btree_geo;
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/**
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* btree_alloc - allocate function for the mempool
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* @gfp_mask: gfp mask for the allocation
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* @pool_data: unused
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*/
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void *btree_alloc(gfp_t gfp_mask, void *pool_data);
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/**
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* btree_free - free function for the mempool
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* @element: the element to free
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* @pool_data: unused
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*/
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void btree_free(void *element, void *pool_data);
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/**
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* btree_init_mempool - initialise a btree with given mempool
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*
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* @head: the btree head to initialise
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* @mempool: the mempool to use
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*
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* When this function is used, there is no need to destroy
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* the mempool.
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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 - initialise a btree
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*
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* @head: the btree head to initialise
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*
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* This function allocates the memory pool that the
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* btree needs. Returns zero or a negative error code
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* (-%ENOMEM) when memory allocation fails.
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*
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*/
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int __must_check btree_init(struct btree_head *head);
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/**
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* btree_destroy - destroy mempool
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*
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* @head: the btree head to destroy
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*
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* This function destroys the internal memory pool, use only
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* when using btree_init(), not with btree_init_mempool().
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*/
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void btree_destroy(struct btree_head *head);
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/**
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* btree_lookup - look up a key in the btree
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*
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* @head: the btree to look in
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* @geo: the btree geometry
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* @key: the key to look up
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*
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* This function returns the value for the given key, or %NULL.
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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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* btree_insert - insert an entry into the btree
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*
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* @head: the btree to add to
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* @geo: the btree geometry
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* @key: the key to add (must not already be present)
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* @val: the value to add (must not be %NULL)
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* @gfp: allocation flags for node allocations
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*
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* This function returns 0 if the item could be added, or an
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* error code if it failed (may fail due to memory pressure).
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*/
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int __must_check btree_insert(struct btree_head *head, struct btree_geo *geo,
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unsigned long *key, void *val, gfp_t gfp);
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/**
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* btree_update - update an entry in the btree
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*
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* @head: the btree to update
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* @geo: the btree geometry
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* @key: the key to update
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* @val: the value to change it to (must not be %NULL)
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*
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* This function returns 0 if the update was successful, or
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* -%ENOENT if the key could not be found.
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*/
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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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* btree_remove - remove an entry from the btree
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*
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* @head: the btree to update
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* @geo: the btree geometry
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* @key: the key to remove
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*
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* This function returns the removed entry, or %NULL if the key
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* could not be found.
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*/
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void *btree_remove(struct btree_head *head, struct btree_geo *geo,
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unsigned long *key);
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/**
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* btree_merge - merge two btrees
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*
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* @target: the tree that gets all the entries
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* @victim: the tree that gets merged into @target
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* @geo: the btree geometry
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* @gfp: allocation flags
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*
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* The two trees @target and @victim may not contain the same keys,
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* that is a bug and triggers a BUG(). This function returns zero
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* if the trees were merged successfully, and may return a failure
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* when memory allocation fails, in which case both trees might have
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* been partially merged, i.e. some entries have been moved from
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* @victim to @target.
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*/
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int btree_merge(struct btree_head *target, struct btree_head *victim,
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struct btree_geo *geo, gfp_t gfp);
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/**
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* btree_last - get last entry in btree
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*
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* @head: btree head
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* @geo: btree geometry
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* @key: last key
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*
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* Returns the last entry in the btree, and sets @key to the key
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* of that entry; returns NULL if the tree is empty, in that case
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* key is not changed.
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*/
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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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* btree_get_prev - get previous entry
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*
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* @head: btree head
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* @geo: btree geometry
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* @key: pointer to key
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*
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* The function returns the next item right before the value pointed to by
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* @key, and updates @key with its key, or returns %NULL when there is no
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* entry with a key smaller than the given key.
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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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/* internal use, use btree_visitor{l,32,64,128} */
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size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
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unsigned long opaque,
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void (*func)(void *elem, unsigned long opaque,
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unsigned long *key, size_t index,
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void *func2),
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void *func2);
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/* internal use, use btree_grim_visitor{l,32,64,128} */
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size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
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unsigned long opaque,
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void (*func)(void *elem, unsigned long opaque,
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unsigned long *key,
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size_t index, void *func2),
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void *func2);
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#include <linux/btree-128.h>
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extern struct btree_geo btree_geo32;
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#define BTREE_TYPE_SUFFIX l
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#define BTREE_TYPE_BITS BITS_PER_LONG
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#define BTREE_TYPE_GEO &btree_geo32
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#define BTREE_KEYTYPE unsigned long
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#include <linux/btree-type.h>
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#define btree_for_each_safel(head, key, val) \
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for (val = btree_lastl(head, &key); \
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val; \
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val = btree_get_prevl(head, &key))
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#define BTREE_TYPE_SUFFIX 32
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#define BTREE_TYPE_BITS 32
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#define BTREE_TYPE_GEO &btree_geo32
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#define BTREE_KEYTYPE u32
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#include <linux/btree-type.h>
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#define btree_for_each_safe32(head, key, val) \
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for (val = btree_last32(head, &key); \
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val; \
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val = btree_get_prev32(head, &key))
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extern struct btree_geo btree_geo64;
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#define BTREE_TYPE_SUFFIX 64
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#define BTREE_TYPE_BITS 64
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#define BTREE_TYPE_GEO &btree_geo64
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#define BTREE_KEYTYPE u64
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#include <linux/btree-type.h>
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#define btree_for_each_safe64(head, key, val) \
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for (val = btree_last64(head, &key); \
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val; \
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val = btree_get_prev64(head, &key))
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#endif
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