| /* |
| * Copyright (C) 2001 Momchil Velikov |
| * Portions Copyright (C) 2001 Christoph Hellwig |
| * Copyright (C) 2006 Nick Piggin |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation; either version 2, or (at |
| * your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| */ |
| #ifndef _LINUX_RADIX_TREE_H |
| #define _LINUX_RADIX_TREE_H |
| |
| #include <linux/preempt.h> |
| #include <linux/types.h> |
| #include <linux/kernel.h> |
| #include <linux/rcupdate.h> |
| |
| /* |
| * An indirect pointer (root->rnode pointing to a radix_tree_node, rather |
| * than a data item) is signalled by the low bit set in the root->rnode |
| * pointer. |
| * |
| * In this case root->height is > 0, but the indirect pointer tests are |
| * needed for RCU lookups (because root->height is unreliable). The only |
| * time callers need worry about this is when doing a lookup_slot under |
| * RCU. |
| * |
| * Indirect pointer in fact is also used to tag the last pointer of a node |
| * when it is shrunk, before we rcu free the node. See shrink code for |
| * details. |
| */ |
| #define RADIX_TREE_INDIRECT_PTR 1 |
| /* |
| * A common use of the radix tree is to store pointers to struct pages; |
| * but shmem/tmpfs needs also to store swap entries in the same tree: |
| * those are marked as exceptional entries to distinguish them. |
| * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it. |
| */ |
| #define RADIX_TREE_EXCEPTIONAL_ENTRY 2 |
| #define RADIX_TREE_EXCEPTIONAL_SHIFT 2 |
| |
| #define radix_tree_indirect_to_ptr(ptr) \ |
| radix_tree_indirect_to_ptr((void __force *)(ptr)) |
| |
| static inline int radix_tree_is_indirect_ptr(void *ptr) |
| { |
| return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); |
| } |
| |
| /*** radix-tree API starts here ***/ |
| |
| #define RADIX_TREE_MAX_TAGS 3 |
| |
| /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */ |
| struct radix_tree_root { |
| unsigned int height; |
| gfp_t gfp_mask; |
| struct radix_tree_node __rcu *rnode; |
| }; |
| |
| #define RADIX_TREE_INIT(mask) { \ |
| .height = 0, \ |
| .gfp_mask = (mask), \ |
| .rnode = NULL, \ |
| } |
| |
| #define RADIX_TREE(name, mask) \ |
| struct radix_tree_root name = RADIX_TREE_INIT(mask) |
| |
| #define INIT_RADIX_TREE(root, mask) \ |
| do { \ |
| (root)->height = 0; \ |
| (root)->gfp_mask = (mask); \ |
| (root)->rnode = NULL; \ |
| } while (0) |
| |
| /** |
| * Radix-tree synchronization |
| * |
| * The radix-tree API requires that users provide all synchronisation (with |
| * specific exceptions, noted below). |
| * |
| * Synchronization of access to the data items being stored in the tree, and |
| * management of their lifetimes must be completely managed by API users. |
| * |
| * For API usage, in general, |
| * - any function _modifying_ the tree or tags (inserting or deleting |
| * items, setting or clearing tags) must exclude other modifications, and |
| * exclude any functions reading the tree. |
| * - any function _reading_ the tree or tags (looking up items or tags, |
| * gang lookups) must exclude modifications to the tree, but may occur |
| * concurrently with other readers. |
| * |
| * The notable exceptions to this rule are the following functions: |
| * radix_tree_lookup |
| * radix_tree_lookup_slot |
| * radix_tree_tag_get |
| * radix_tree_gang_lookup |
| * radix_tree_gang_lookup_slot |
| * radix_tree_gang_lookup_tag |
| * radix_tree_gang_lookup_tag_slot |
| * radix_tree_tagged |
| * |
| * The first 7 functions are able to be called locklessly, using RCU. The |
| * caller must ensure calls to these functions are made within rcu_read_lock() |
| * regions. Other readers (lock-free or otherwise) and modifications may be |
| * running concurrently. |
| * |
| * It is still required that the caller manage the synchronization and lifetimes |
| * of the items. So if RCU lock-free lookups are used, typically this would mean |
| * that the items have their own locks, or are amenable to lock-free access; and |
| * that the items are freed by RCU (or only freed after having been deleted from |
| * the radix tree *and* a synchronize_rcu() grace period). |
| * |
| * (Note, rcu_assign_pointer and rcu_dereference are not needed to control |
| * access to data items when inserting into or looking up from the radix tree) |
| * |
| * Note that the value returned by radix_tree_tag_get() may not be relied upon |
| * if only the RCU read lock is held. Functions to set/clear tags and to |
| * delete nodes running concurrently with it may affect its result such that |
| * two consecutive reads in the same locked section may return different |
| * values. If reliability is required, modification functions must also be |
| * excluded from concurrency. |
| * |
| * radix_tree_tagged is able to be called without locking or RCU. |
| */ |
| |
| /** |
| * radix_tree_deref_slot - dereference a slot |
| * @pslot: pointer to slot, returned by radix_tree_lookup_slot |
| * Returns: item that was stored in that slot with any direct pointer flag |
| * removed. |
| * |
| * For use with radix_tree_lookup_slot(). Caller must hold tree at least read |
| * locked across slot lookup and dereference. Not required if write lock is |
| * held (ie. items cannot be concurrently inserted). |
| * |
| * radix_tree_deref_retry must be used to confirm validity of the pointer if |
| * only the read lock is held. |
| */ |
| static inline void *radix_tree_deref_slot(void **pslot) |
| { |
| return rcu_dereference(*pslot); |
| } |
| |
| /** |
| * radix_tree_deref_slot_protected - dereference a slot without RCU lock but with tree lock held |
| * @pslot: pointer to slot, returned by radix_tree_lookup_slot |
| * Returns: item that was stored in that slot with any direct pointer flag |
| * removed. |
| * |
| * Similar to radix_tree_deref_slot but only used during migration when a pages |
| * mapping is being moved. The caller does not hold the RCU read lock but it |
| * must hold the tree lock to prevent parallel updates. |
| */ |
| static inline void *radix_tree_deref_slot_protected(void **pslot, |
| spinlock_t *treelock) |
| { |
| return rcu_dereference_protected(*pslot, lockdep_is_held(treelock)); |
| } |
| |
| /** |
| * radix_tree_deref_retry - check radix_tree_deref_slot |
| * @arg: pointer returned by radix_tree_deref_slot |
| * Returns: 0 if retry is not required, otherwise retry is required |
| * |
| * radix_tree_deref_retry must be used with radix_tree_deref_slot. |
| */ |
| static inline int radix_tree_deref_retry(void *arg) |
| { |
| return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR); |
| } |
| |
| /** |
| * radix_tree_exceptional_entry - radix_tree_deref_slot gave exceptional entry? |
| * @arg: value returned by radix_tree_deref_slot |
| * Returns: 0 if well-aligned pointer, non-0 if exceptional entry. |
| */ |
| static inline int radix_tree_exceptional_entry(void *arg) |
| { |
| /* Not unlikely because radix_tree_exception often tested first */ |
| return (unsigned long)arg & RADIX_TREE_EXCEPTIONAL_ENTRY; |
| } |
| |
| /** |
| * radix_tree_exception - radix_tree_deref_slot returned either exception? |
| * @arg: value returned by radix_tree_deref_slot |
| * Returns: 0 if well-aligned pointer, non-0 if either kind of exception. |
| */ |
| static inline int radix_tree_exception(void *arg) |
| { |
| return unlikely((unsigned long)arg & |
| (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY)); |
| } |
| |
| /** |
| * radix_tree_replace_slot - replace item in a slot |
| * @pslot: pointer to slot, returned by radix_tree_lookup_slot |
| * @item: new item to store in the slot. |
| * |
| * For use with radix_tree_lookup_slot(). Caller must hold tree write locked |
| * across slot lookup and replacement. |
| */ |
| static inline void radix_tree_replace_slot(void **pslot, void *item) |
| { |
| BUG_ON(radix_tree_is_indirect_ptr(item)); |
| rcu_assign_pointer(*pslot, item); |
| } |
| |
| int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); |
| void *radix_tree_lookup(struct radix_tree_root *, unsigned long); |
| void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); |
| void *radix_tree_delete(struct radix_tree_root *, unsigned long); |
| unsigned int |
| radix_tree_gang_lookup(struct radix_tree_root *root, void **results, |
| unsigned long first_index, unsigned int max_items); |
| unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root, |
| void ***results, unsigned long *indices, |
| unsigned long first_index, unsigned int max_items); |
| unsigned long radix_tree_next_hole(struct radix_tree_root *root, |
| unsigned long index, unsigned long max_scan); |
| unsigned long radix_tree_prev_hole(struct radix_tree_root *root, |
| unsigned long index, unsigned long max_scan); |
| int radix_tree_preload(gfp_t gfp_mask); |
| void radix_tree_init(void); |
| void *radix_tree_tag_set(struct radix_tree_root *root, |
| unsigned long index, unsigned int tag); |
| void *radix_tree_tag_clear(struct radix_tree_root *root, |
| unsigned long index, unsigned int tag); |
| int radix_tree_tag_get(struct radix_tree_root *root, |
| unsigned long index, unsigned int tag); |
| unsigned int |
| radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, |
| unsigned long first_index, unsigned int max_items, |
| unsigned int tag); |
| unsigned int |
| radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, |
| unsigned long first_index, unsigned int max_items, |
| unsigned int tag); |
| unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, |
| unsigned long *first_indexp, unsigned long last_index, |
| unsigned long nr_to_tag, |
| unsigned int fromtag, unsigned int totag); |
| int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag); |
| unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item); |
| |
| static inline void radix_tree_preload_end(void) |
| { |
| preempt_enable(); |
| } |
| |
| #endif /* _LINUX_RADIX_TREE_H */ |