Permalink
Fetching contributors…
Cannot retrieve contributors at this time
573 lines (528 sloc) 19.8 KB
/*
* 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/bitops.h>
#include <linux/preempt.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
/*
* The bottom two bits of the slot determine how the remaining bits in the
* slot are interpreted:
*
* 00 - data pointer
* 01 - internal entry
* 10 - exceptional entry
* 11 - this bit combination is currently unused/reserved
*
* 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 you cannot store NULL in the tree as a value for the index.
*/
#define RADIX_TREE_ENTRY_MASK 3UL
#define RADIX_TREE_INTERNAL_NODE 1UL
/*
* Most users of the radix tree store pointers but shmem/tmpfs stores swap
* entries in the same tree. They are marked as exceptional entries to
* distinguish them from pointers to struct page.
* 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 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_MAX_TAGS 3
#ifndef RADIX_TREE_MAP_SHIFT
#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
#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))
/*
* @count is the count of every non-NULL element in the ->slots array
* whether that is an exceptional entry, a retry entry, a user pointer,
* a sibling entry or a pointer to the next level of the tree.
* @exceptional is the count of every element in ->slots which is
* either radix_tree_exceptional_entry() or is a sibling entry for an
* exceptional entry.
*/
struct radix_tree_node {
unsigned char shift; /* Bits remaining in each slot */
unsigned char offset; /* Slot offset in parent */
unsigned char count; /* Total entry count */
unsigned char exceptional; /* Exceptional entry count */
struct radix_tree_node *parent; /* Used when ascending tree */
void *private_data; /* For tree user */
union {
struct list_head private_list; /* For tree user */
struct rcu_head rcu_head; /* Used when freeing node */
};
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 {
gfp_t gfp_mask;
struct radix_tree_node __rcu *rnode;
};
#define RADIX_TREE_INIT(mask) { \
.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)->gfp_mask = (mask); \
(root)->rnode = NULL; \
} while (0)
static inline bool radix_tree_empty(struct radix_tree_root *root)
{
return root->rnode == 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
* @shift: shift for the node that holds our slots
*
* 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;
#ifdef CONFIG_RADIX_TREE_MULTIORDER
unsigned int shift;
#endif
};
static inline unsigned int iter_shift(const struct radix_tree_iter *iter)
{
#ifdef CONFIG_RADIX_TREE_MULTIORDER
return iter->shift;
#else
return 0;
#endif
}
/**
* 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 8 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(radix_tree_is_internal_node(arg));
}
/**
* 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_ENTRY_MASK);
}
int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
unsigned order, struct radix_tree_node **nodep,
void ***slotp);
int __radix_tree_insert(struct radix_tree_root *, unsigned long index,
unsigned order, void *);
static inline int radix_tree_insert(struct radix_tree_root *root,
unsigned long index, void *entry)
{
return __radix_tree_insert(root, index, 0, entry);
}
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);
typedef void (*radix_tree_update_node_t)(struct radix_tree_node *, void *);
void __radix_tree_replace(struct radix_tree_root *root,
struct radix_tree_node *node,
void **slot, void *item,
radix_tree_update_node_t update_node, void *private);
void radix_tree_iter_replace(struct radix_tree_root *,
const struct radix_tree_iter *, void **slot, void *item);
void radix_tree_replace_slot(struct radix_tree_root *root,
void **slot, void *item);
void __radix_tree_delete_node(struct radix_tree_root *root,
struct radix_tree_node *node,
radix_tree_update_node_t update_node,
void *private);
void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_delete(struct radix_tree_root *, unsigned long);
void radix_tree_clear_tags(struct radix_tree_root *root,
struct radix_tree_node *node,
void **slot);
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);
int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order);
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);
void radix_tree_iter_tag_set(struct radix_tree_root *root,
const struct radix_tree_iter *iter, 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);
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
static inline void radix_tree_preload_end(void)
{
preempt_enable();
}
int radix_tree_split_preload(unsigned old_order, unsigned new_order, gfp_t);
int radix_tree_split(struct radix_tree_root *, unsigned long index,
unsigned new_order);
int radix_tree_join(struct radix_tree_root *, unsigned long index,
unsigned new_order, void *);
#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_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 **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 << iter_shift(iter));
}
/**
* 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 **__must_check radix_tree_iter_resume(void **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) >> iter_shift(iter);
}
#ifdef CONFIG_RADIX_TREE_MULTIORDER
void ** __radix_tree_next_slot(void **slot, struct radix_tree_iter *iter,
unsigned flags);
#else
/* Can't happen without sibling entries, but the compiler can't tell that */
static inline void ** __radix_tree_next_slot(void **slot,
struct radix_tree_iter *iter, unsigned flags)
{
return slot;
}
#endif
/**
* 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 **
radix_tree_next_slot(void **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:
if (unlikely(radix_tree_is_internal_node(*slot)))
return __radix_tree_next_slot(slot, iter, flags);
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_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 | tag))
#endif /* _LINUX_RADIX_TREE_H */