/* | |

* Copyright (C) 2001 Momchil Velikov | |

* Portions Copyright (C) 2001 Christoph Hellwig | |

* Copyright (C) 2006 Nick Piggin | |

* Copyright (C) 2012 Konstantin Khlebnikov | |

* | |

* 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/bug.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 | |

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 | |

#ifdef __KERNEL__ | |

#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6) | |

#else | |

#define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */ | |

#endif | |

#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT) | |

#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1) | |

#define RADIX_TREE_TAG_LONGS \ | |

((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG) | |

#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) | |

#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \ | |

RADIX_TREE_MAP_SHIFT)) | |

/* Height component in node->path */ | |

#define RADIX_TREE_HEIGHT_SHIFT (RADIX_TREE_MAX_PATH + 1) | |

#define RADIX_TREE_HEIGHT_MASK ((1UL << RADIX_TREE_HEIGHT_SHIFT) - 1) | |

/* Internally used bits of node->count */ | |

#define RADIX_TREE_COUNT_SHIFT (RADIX_TREE_MAP_SHIFT + 1) | |

#define RADIX_TREE_COUNT_MASK ((1UL << RADIX_TREE_COUNT_SHIFT) - 1) | |

struct radix_tree_node { | |

unsigned int path; /* Offset in parent & height from the bottom */ | |

unsigned int count; | |

union { | |

struct { | |

/* Used when ascending tree */ | |

struct radix_tree_node *parent; | |

/* For tree user */ | |

void *private_data; | |

}; | |

/* Used when freeing node */ | |

struct rcu_head rcu_head; | |

}; | |

/* For tree user */ | |

struct list_head private_list; | |

void __rcu *slots[RADIX_TREE_MAP_SIZE]; | |

unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS]; | |

}; | |

/* 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 | |

* 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_create(struct radix_tree_root *root, unsigned long index, | |

struct radix_tree_node **nodep, void ***slotp); | |

int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); | |

void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index, | |

struct radix_tree_node **nodep, void ***slotp); | |

void *radix_tree_lookup(struct radix_tree_root *, unsigned long); | |

void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); | |

bool __radix_tree_delete_node(struct radix_tree_root *root, | |

struct radix_tree_node *node); | |

void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *); | |

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); | |

int radix_tree_preload(gfp_t gfp_mask); | |

int radix_tree_maybe_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(); | |

} | |

/** | |

* struct radix_tree_iter - radix tree iterator state | |

* | |

* @index: index of current slot | |

* @next_index: next-to-last index for this chunk | |

* @tags: bit-mask for tag-iterating | |

* | |

* This radix tree iterator works in terms of "chunks" of slots. A chunk is a | |

* subinterval of slots contained within one radix tree leaf node. It is | |

* described by a pointer to its first slot and a struct radix_tree_iter | |

* which holds the chunk's position in the tree and its size. For tagged | |

* iteration radix_tree_iter also holds the slots' bit-mask for one chosen | |

* radix tree tag. | |

*/ | |

struct radix_tree_iter { | |

unsigned long index; | |

unsigned long next_index; | |

unsigned long tags; | |

}; | |

#define RADIX_TREE_ITER_TAG_MASK 0x00FF /* tag index in lower byte */ | |

#define RADIX_TREE_ITER_TAGGED 0x0100 /* lookup tagged slots */ | |

#define RADIX_TREE_ITER_CONTIG 0x0200 /* stop at first hole */ | |

/** | |

* radix_tree_iter_init - initialize radix tree iterator | |

* | |

* @iter: pointer to iterator state | |

* @start: iteration starting index | |

* Returns: NULL | |

*/ | |

static __always_inline void ** | |

radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start) | |

{ | |

/* | |

* Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it | |

* in the case of a successful tagged chunk lookup. If the lookup was | |

* unsuccessful or non-tagged then nobody cares about ->tags. | |

* | |

* Set index to zero to bypass next_index overflow protection. | |

* See the comment in radix_tree_next_chunk() for details. | |

*/ | |

iter->index = 0; | |

iter->next_index = start; | |

return NULL; | |

} | |

/** | |

* radix_tree_next_chunk - find next chunk of slots for iteration | |

* | |

* @root: radix tree root | |

* @iter: iterator state | |

* @flags: RADIX_TREE_ITER_* flags and tag index | |

* Returns: pointer to chunk first slot, or NULL if there no more left | |

* | |

* This function looks up the next chunk in the radix tree starting from | |

* @iter->next_index. It returns a pointer to the chunk's first slot. | |

* Also it fills @iter with data about chunk: position in the tree (index), | |

* its end (next_index), and constructs a bit mask for tagged iterating (tags). | |

*/ | |

void **radix_tree_next_chunk(struct radix_tree_root *root, | |

struct radix_tree_iter *iter, unsigned flags); | |

/** | |

* radix_tree_chunk_size - get current chunk size | |

* | |

* @iter: pointer to radix tree iterator | |

* Returns: current chunk size | |

*/ | |

static __always_inline unsigned | |

radix_tree_chunk_size(struct radix_tree_iter *iter) | |

{ | |

return iter->next_index - iter->index; | |

} | |

/** | |

* radix_tree_next_slot - find next slot in chunk | |

* | |

* @slot: pointer to current slot | |

* @iter: pointer to interator state | |

* @flags: RADIX_TREE_ITER_*, should be constant | |

* Returns: pointer to next slot, or NULL if there no more left | |

* | |

* This function updates @iter->index in the case of a successful lookup. | |

* For tagged lookup it also eats @iter->tags. | |

*/ | |

static __always_inline void ** | |

radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags) | |

{ | |

if (flags & RADIX_TREE_ITER_TAGGED) { | |

iter->tags >>= 1; | |

if (likely(iter->tags & 1ul)) { | |

iter->index++; | |

return slot + 1; | |

} | |

if (!(flags & RADIX_TREE_ITER_CONTIG) && likely(iter->tags)) { | |

unsigned offset = __ffs(iter->tags); | |

iter->tags >>= offset; | |

iter->index += offset + 1; | |

return slot + offset + 1; | |

} | |

} else { | |

unsigned size = radix_tree_chunk_size(iter) - 1; | |

while (size--) { | |

slot++; | |

iter->index++; | |

if (likely(*slot)) | |

return slot; | |

if (flags & RADIX_TREE_ITER_CONTIG) { | |

/* forbid switching to the next chunk */ | |

iter->next_index = 0; | |

break; | |

} | |

} | |

} | |

return NULL; | |

} | |

/** | |

* radix_tree_for_each_chunk - iterate over chunks | |

* | |

* @slot: the void** variable for pointer to chunk first slot | |

* @root: the struct radix_tree_root pointer | |

* @iter: the struct radix_tree_iter pointer | |

* @start: iteration starting index | |

* @flags: RADIX_TREE_ITER_* and tag index | |

* | |

* Locks can be released and reacquired between iterations. | |

*/ | |

#define radix_tree_for_each_chunk(slot, root, iter, start, flags) \ | |

for (slot = radix_tree_iter_init(iter, start) ; \ | |

(slot = radix_tree_next_chunk(root, iter, flags)) ;) | |

/** | |

* radix_tree_for_each_chunk_slot - iterate over slots in one chunk | |

* | |

* @slot: the void** variable, at the beginning points to chunk first slot | |

* @iter: the struct radix_tree_iter pointer | |

* @flags: RADIX_TREE_ITER_*, should be constant | |

* | |

* This macro is designed to be nested inside radix_tree_for_each_chunk(). | |

* @slot points to the radix tree slot, @iter->index contains its index. | |

*/ | |

#define radix_tree_for_each_chunk_slot(slot, iter, flags) \ | |

for (; slot ; slot = radix_tree_next_slot(slot, iter, flags)) | |

/** | |

* radix_tree_for_each_slot - iterate over non-empty slots | |

* | |

* @slot: the void** variable for pointer to slot | |

* @root: the struct radix_tree_root pointer | |

* @iter: the struct radix_tree_iter pointer | |

* @start: iteration starting index | |

* | |

* @slot points to radix tree slot, @iter->index contains its index. | |

*/ | |

#define radix_tree_for_each_slot(slot, root, iter, start) \ | |

for (slot = radix_tree_iter_init(iter, start) ; \ | |

slot || (slot = radix_tree_next_chunk(root, iter, 0)) ; \ | |

slot = radix_tree_next_slot(slot, iter, 0)) | |

/** | |

* radix_tree_for_each_contig - iterate over contiguous slots | |

* | |

* @slot: the void** variable for pointer to slot | |

* @root: the struct radix_tree_root pointer | |

* @iter: the struct radix_tree_iter pointer | |

* @start: iteration starting index | |

* | |

* @slot points to radix tree slot, @iter->index contains its index. | |

*/ | |

#define radix_tree_for_each_contig(slot, root, iter, start) \ | |

for (slot = radix_tree_iter_init(iter, start) ; \ | |

slot || (slot = radix_tree_next_chunk(root, iter, \ | |

RADIX_TREE_ITER_CONTIG)) ; \ | |

slot = radix_tree_next_slot(slot, iter, \ | |

RADIX_TREE_ITER_CONTIG)) | |

/** | |

* radix_tree_for_each_tagged - iterate over tagged slots | |

* | |

* @slot: the void** variable for pointer to slot | |

* @root: the struct radix_tree_root pointer | |

* @iter: the struct radix_tree_iter pointer | |

* @start: iteration starting index | |

* @tag: tag index | |

* | |

* @slot points to radix tree slot, @iter->index contains its index. | |

*/ | |

#define radix_tree_for_each_tagged(slot, root, iter, start, tag) \ | |

for (slot = radix_tree_iter_init(iter, start) ; \ | |

slot || (slot = radix_tree_next_chunk(root, iter, \ | |

RADIX_TREE_ITER_TAGGED | tag)) ; \ | |

slot = radix_tree_next_slot(slot, iter, \ | |

RADIX_TREE_ITER_TAGGED)) | |

#endif /* _LINUX_RADIX_TREE_H */ |