1/* 2 * Copyright (C) 2001 Momchil Velikov 3 * Portions Copyright (C) 2001 Christoph Hellwig 4 * Copyright (C) 2006 Nick Piggin 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation; either version 2, or (at 9 * your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, but 12 * WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 19 */ 20#ifndef _LINUX_RADIX_TREE_H 21#define _LINUX_RADIX_TREE_H 22 23#include <linux/preempt.h> 24#include <linux/types.h> 25#include <linux/kernel.h> 26#include <linux/rcupdate.h> 27 28/* 29 * An indirect pointer (root->rnode pointing to a radix_tree_node, rather 30 * than a data item) is signalled by the low bit set in the root->rnode 31 * pointer. 32 * 33 * In this case root->height is > 0, but the indirect pointer tests are 34 * needed for RCU lookups (because root->height is unreliable). The only 35 * time callers need worry about this is when doing a lookup_slot under 36 * RCU. 37 */ 38#define RADIX_TREE_INDIRECT_PTR 1 39#define RADIX_TREE_RETRY ((void *)-1UL) 40 41static inline void *radix_tree_ptr_to_indirect(void *ptr) 42{ 43 return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR); 44} 45 46static inline void *radix_tree_indirect_to_ptr(void *ptr) 47{ 48 return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); 49} 50 51static inline int radix_tree_is_indirect_ptr(void *ptr) 52{ 53 return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); 54} 55 56/*** radix-tree API starts here ***/ 57 58#define RADIX_TREE_MAX_TAGS 2 59 60/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */ 61struct radix_tree_root { 62 unsigned int height; 63 gfp_t gfp_mask; 64 struct radix_tree_node *rnode; 65}; 66 67#define RADIX_TREE_INIT(mask) { \ 68 .height = 0, \ 69 .gfp_mask = (mask), \ 70 .rnode = NULL, \ 71} 72 73#define RADIX_TREE(name, mask) \ 74 struct radix_tree_root name = RADIX_TREE_INIT(mask) 75 76#define INIT_RADIX_TREE(root, mask) \ 77do { \ 78 (root)->height = 0; \ 79 (root)->gfp_mask = (mask); \ 80 (root)->rnode = NULL; \ 81} while (0) 82 83/** 84 * Radix-tree synchronization 85 * 86 * The radix-tree API requires that users provide all synchronisation (with 87 * specific exceptions, noted below). 88 * 89 * Synchronization of access to the data items being stored in the tree, and 90 * management of their lifetimes must be completely managed by API users. 91 * 92 * For API usage, in general, 93 * - any function _modifying_ the tree or tags (inserting or deleting 94 * items, setting or clearing tags) must exclude other modifications, and 95 * exclude any functions reading the tree. 96 * - any function _reading_ the tree or tags (looking up items or tags, 97 * gang lookups) must exclude modifications to the tree, but may occur 98 * concurrently with other readers. 99 * 100 * The notable exceptions to this rule are the following functions: 101 * radix_tree_lookup 102 * radix_tree_lookup_slot 103 * radix_tree_tag_get 104 * radix_tree_gang_lookup 105 * radix_tree_gang_lookup_slot 106 * radix_tree_gang_lookup_tag 107 * radix_tree_gang_lookup_tag_slot 108 * radix_tree_tagged 109 * 110 * The first 7 functions are able to be called locklessly, using RCU. The 111 * caller must ensure calls to these functions are made within rcu_read_lock() 112 * regions. Other readers (lock-free or otherwise) and modifications may be 113 * running concurrently. 114 * 115 * It is still required that the caller manage the synchronization and lifetimes 116 * of the items. So if RCU lock-free lookups are used, typically this would mean 117 * that the items have their own locks, or are amenable to lock-free access; and 118 * that the items are freed by RCU (or only freed after having been deleted from 119 * the radix tree *and* a synchronize_rcu() grace period). 120 * 121 * (Note, rcu_assign_pointer and rcu_dereference are not needed to control 122 * access to data items when inserting into or looking up from the radix tree) 123 * 124 * radix_tree_tagged is able to be called without locking or RCU. 125 */ 126 127/** 128 * radix_tree_deref_slot - dereference a slot 129 * @pslot: pointer to slot, returned by radix_tree_lookup_slot 130 * Returns: item that was stored in that slot with any direct pointer flag 131 * removed. 132 * 133 * For use with radix_tree_lookup_slot(). Caller must hold tree at least read 134 * locked across slot lookup and dereference. More likely, will be used with 135 * radix_tree_replace_slot(), as well, so caller will hold tree write locked. 136 */ 137static inline void *radix_tree_deref_slot(void **pslot) 138{ 139 void *ret = rcu_dereference(*pslot); 140 if (unlikely(radix_tree_is_indirect_ptr(ret))) 141 ret = RADIX_TREE_RETRY; 142 return ret; 143} 144/** 145 * radix_tree_replace_slot - replace item in a slot 146 * @pslot: pointer to slot, returned by radix_tree_lookup_slot 147 * @item: new item to store in the slot. 148 * 149 * For use with radix_tree_lookup_slot(). Caller must hold tree write locked 150 * across slot lookup and replacement. 151 */ 152static inline void radix_tree_replace_slot(void **pslot, void *item) 153{ 154 BUG_ON(radix_tree_is_indirect_ptr(item)); 155 rcu_assign_pointer(*pslot, item); 156} 157 158int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); 159void *radix_tree_lookup(struct radix_tree_root *, unsigned long); 160void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); 161void *radix_tree_delete(struct radix_tree_root *, unsigned long); 162unsigned int 163radix_tree_gang_lookup(struct radix_tree_root *root, void **results, 164 unsigned long first_index, unsigned int max_items); 165unsigned int 166radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results, 167 unsigned long first_index, unsigned int max_items); 168unsigned long radix_tree_next_hole(struct radix_tree_root *root, 169 unsigned long index, unsigned long max_scan); 170unsigned long radix_tree_prev_hole(struct radix_tree_root *root, 171 unsigned long index, unsigned long max_scan); 172int radix_tree_preload(gfp_t gfp_mask); 173void radix_tree_init(void); 174void *radix_tree_tag_set(struct radix_tree_root *root, 175 unsigned long index, unsigned int tag); 176void *radix_tree_tag_clear(struct radix_tree_root *root, 177 unsigned long index, unsigned int tag); 178int radix_tree_tag_get(struct radix_tree_root *root, 179 unsigned long index, unsigned int tag); 180unsigned int 181radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, 182 unsigned long first_index, unsigned int max_items, 183 unsigned int tag); 184unsigned int 185radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, 186 unsigned long first_index, unsigned int max_items, 187 unsigned int tag); 188int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag); 189 190static inline void radix_tree_preload_end(void) 191{ 192 preempt_enable(); 193} 194 195#endif /* _LINUX_RADIX_TREE_H */ 196