code / linux / torvalds / linux / e2cf67f6689a218b4d8e606e90a12491a9cfa366 / . / include / linux / radix-tree.h

/* SPDX-License-Identifier: GPL-2.0-or-later */ | |

/* | |

* Copyright (C) 2001 Momchil Velikov | |

* Portions Copyright (C) 2001 Christoph Hellwig | |

* Copyright (C) 2006 Nick Piggin | |

* Copyright (C) 2012 Konstantin Khlebnikov | |

*/ | |

#ifndef _LINUX_RADIX_TREE_H | |

#define _LINUX_RADIX_TREE_H | |

#include <linux/bitops.h> | |

#include <linux/kernel.h> | |

#include <linux/list.h> | |

#include <linux/preempt.h> | |

#include <linux/rcupdate.h> | |

#include <linux/spinlock.h> | |

#include <linux/types.h> | |

#include <linux/xarray.h> | |

/* Keep unconverted code working */ | |

#define radix_tree_root xarray | |

#define radix_tree_node xa_node | |

/* | |

* The bottom two bits of the slot determine how the remaining bits in the | |

* slot are interpreted: | |

* | |

* 00 - data pointer | |

* 10 - internal entry | |

* x1 - value entry | |

* | |

* The internal entry may be a pointer to the next level in the tree, a | |

* sibling entry, or an indicator that the entry in this slot has been moved | |

* to another location in the tree and the lookup should be restarted. While | |

* NULL fits the 'data pointer' pattern, it means that there is no entry in | |

* the tree for this index (no matter what level of the tree it is found at). | |

* This means that storing a NULL entry in the tree is the same as deleting | |

* the entry from the tree. | |

*/ | |

#define RADIX_TREE_ENTRY_MASK 3UL | |

#define RADIX_TREE_INTERNAL_NODE 2UL | |

static inline bool radix_tree_is_internal_node(void *ptr) | |

{ | |

return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) == | |

RADIX_TREE_INTERNAL_NODE; | |

} | |

/*** radix-tree API starts here ***/ | |

#define RADIX_TREE_MAP_SHIFT XA_CHUNK_SHIFT | |

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

#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1) | |

#define RADIX_TREE_MAX_TAGS XA_MAX_MARKS | |

#define RADIX_TREE_TAG_LONGS XA_MARK_LONGS | |

#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)) | |

/* The IDR tag is stored in the low bits of xa_flags */ | |

#define ROOT_IS_IDR ((__force gfp_t)4) | |

/* The top bits of xa_flags are used to store the root tags */ | |

#define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT) | |

#define RADIX_TREE_INIT(name, mask) XARRAY_INIT(name, mask) | |

#define RADIX_TREE(name, mask) \ | |

struct radix_tree_root name = RADIX_TREE_INIT(name, mask) | |

#define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask) | |

static inline bool radix_tree_empty(const struct radix_tree_root *root) | |

{ | |

return root->xa_head == NULL; | |

} | |

/** | |

* struct radix_tree_iter - radix tree iterator state | |

* | |

* @index: index of current slot | |

* @next_index: one beyond the last index for this chunk | |

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

* @node: node that contains current slot | |

* | |

* 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; | |

struct radix_tree_node *node; | |

}; | |

/** | |

* 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_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 | |

* @slot: slot pointer, returned by radix_tree_lookup_slot | |

* | |

* 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. | |

* | |

* Return: entry stored in that slot. | |

*/ | |

static inline void *radix_tree_deref_slot(void __rcu **slot) | |

{ | |

return rcu_dereference(*slot); | |

} | |

/** | |

* radix_tree_deref_slot_protected - dereference a slot with tree lock held | |

* @slot: slot pointer, returned by radix_tree_lookup_slot | |

* | |

* Similar to radix_tree_deref_slot. The caller does not hold the RCU read | |

* lock but it must hold the tree lock to prevent parallel updates. | |

* | |

* Return: entry stored in that slot. | |

*/ | |

static inline void *radix_tree_deref_slot_protected(void __rcu **slot, | |

spinlock_t *treelock) | |

{ | |

return rcu_dereference_protected(*slot, 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(radix_tree_is_internal_node(arg)); | |

} | |

/** | |

* 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_ENTRY_MASK); | |

} | |

int radix_tree_insert(struct radix_tree_root *, unsigned long index, | |

void *); | |

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

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

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

void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *, | |

unsigned long index); | |

void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *, | |

void __rcu **slot, void *entry); | |

void radix_tree_iter_replace(struct radix_tree_root *, | |

const struct radix_tree_iter *, void __rcu **slot, void *entry); | |

void radix_tree_replace_slot(struct radix_tree_root *, | |

void __rcu **slot, void *entry); | |

void radix_tree_iter_delete(struct radix_tree_root *, | |

struct radix_tree_iter *iter, void __rcu **slot); | |

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(const struct radix_tree_root *, | |

void **results, 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 *, | |

unsigned long index, unsigned int tag); | |

void *radix_tree_tag_clear(struct radix_tree_root *, | |

unsigned long index, unsigned int tag); | |

int radix_tree_tag_get(const struct radix_tree_root *, | |

unsigned long index, unsigned int tag); | |

void radix_tree_iter_tag_clear(struct radix_tree_root *, | |

const struct radix_tree_iter *iter, unsigned int tag); | |

unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *, | |

void **results, unsigned long first_index, | |

unsigned int max_items, unsigned int tag); | |

unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *, | |

void __rcu ***results, unsigned long first_index, | |

unsigned int max_items, unsigned int tag); | |

int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag); | |

static inline void radix_tree_preload_end(void) | |

{ | |

preempt_enable(); | |

} | |

void __rcu **idr_get_free(struct radix_tree_root *root, | |

struct radix_tree_iter *iter, gfp_t gfp, | |

unsigned long max); | |

enum { | |

RADIX_TREE_ITER_TAG_MASK = 0x0f, /* tag index in lower nybble */ | |

RADIX_TREE_ITER_TAGGED = 0x10, /* lookup tagged slots */ | |

RADIX_TREE_ITER_CONTIG = 0x20, /* 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 __rcu ** | |

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 __rcu **radix_tree_next_chunk(const struct radix_tree_root *, | |

struct radix_tree_iter *iter, unsigned flags); | |

/** | |

* radix_tree_iter_lookup - look up an index in the radix tree | |

* @root: radix tree root | |

* @iter: iterator state | |

* @index: key to look up | |

* | |

* If @index is present in the radix tree, this function returns the slot | |

* containing it and updates @iter to describe the entry. If @index is not | |

* present, it returns NULL. | |

*/ | |

static inline void __rcu ** | |

radix_tree_iter_lookup(const struct radix_tree_root *root, | |

struct radix_tree_iter *iter, unsigned long index) | |

{ | |

radix_tree_iter_init(iter, index); | |

return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG); | |

} | |

/** | |

* radix_tree_iter_retry - retry this chunk of the iteration | |

* @iter: iterator state | |

* | |

* If we iterate over a tree protected only by the RCU lock, a race | |

* against deletion or creation may result in seeing a slot for which | |

* radix_tree_deref_retry() returns true. If so, call this function | |

* and continue the iteration. | |

*/ | |

static inline __must_check | |

void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter) | |

{ | |

iter->next_index = iter->index; | |

iter->tags = 0; | |

return NULL; | |

} | |

static inline unsigned long | |

__radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots) | |

{ | |

return iter->index + slots; | |

} | |

/** | |

* radix_tree_iter_resume - resume iterating when the chunk may be invalid | |

* @slot: pointer to current slot | |

* @iter: iterator state | |

* Returns: New slot pointer | |

* | |

* If the iterator needs to release then reacquire a lock, the chunk may | |

* have been invalidated by an insertion or deletion. Call this function | |

* before releasing the lock to continue the iteration from the next index. | |

*/ | |

void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot, | |

struct radix_tree_iter *iter); | |

/** | |

* radix_tree_chunk_size - get current chunk size | |

* | |

* @iter: pointer to radix tree iterator | |

* Returns: current chunk size | |

*/ | |

static __always_inline long | |

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. | |

* | |

* There are several cases where 'slot' can be passed in as NULL to this | |

* function. These cases result from the use of radix_tree_iter_resume() or | |

* radix_tree_iter_retry(). In these cases we don't end up dereferencing | |

* 'slot' because either: | |

* a) we are doing tagged iteration and iter->tags has been set to 0, or | |

* b) we are doing non-tagged iteration, and iter->index and iter->next_index | |

* have been set up so that radix_tree_chunk_size() returns 1 or 0. | |

*/ | |

static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot, | |

struct radix_tree_iter *iter, unsigned flags) | |

{ | |

if (flags & RADIX_TREE_ITER_TAGGED) { | |

iter->tags >>= 1; | |

if (unlikely(!iter->tags)) | |

return NULL; | |

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

iter->index = __radix_tree_iter_add(iter, 1); | |

slot++; | |

goto found; | |

} | |

if (!(flags & RADIX_TREE_ITER_CONTIG)) { | |

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

iter->tags >>= offset++; | |

iter->index = __radix_tree_iter_add(iter, offset); | |

slot += offset; | |

goto found; | |

} | |

} else { | |

long count = radix_tree_chunk_size(iter); | |

while (--count > 0) { | |

slot++; | |

iter->index = __radix_tree_iter_add(iter, 1); | |

if (likely(*slot)) | |

goto found; | |

if (flags & RADIX_TREE_ITER_CONTIG) { | |

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

iter->next_index = 0; | |

break; | |

} | |

} | |

} | |

return NULL; | |

found: | |

return slot; | |

} | |

/** | |

* 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_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 | tag)) | |

#endif /* _LINUX_RADIX_TREE_H */ |