/* SPDX-License-Identifier: GPL-2.0+ */
#ifndef _LINUX_MAPLE_TREE_H
#define _LINUX_MAPLE_TREE_H
/*
* Maple Tree - An RCU-safe adaptive tree for storing ranges
* Copyright (c) 2018-2022 Oracle
* Authors: Liam R. Howlett <Liam.Howlett@Oracle.com>
* Matthew Wilcox <willy@infradead.org>
*/
#include <linux/kernel.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
/* #define CONFIG_MAPLE_RCU_DISABLED */
/* #define CONFIG_DEBUG_MAPLE_TREE_VERBOSE */
/*
* Allocated nodes are mutable until they have been inserted into the tree,
* at which time they cannot change their type until they have been removed
* from the tree and an RCU grace period has passed.
*
* Removed nodes have their ->parent set to point to themselves. RCU readers
* check ->parent before relying on the value that they loaded from the
* slots array. This lets us reuse the slots array for the RCU head.
*
* Nodes in the tree point to their parent unless bit 0 is set.
*/
#if defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64)
/* 64bit sizes */
#define MAPLE_NODE_SLOTS 31 /* 256 bytes including ->parent */
#define MAPLE_RANGE64_SLOTS 16 /* 256 bytes */
#define MAPLE_ARANGE64_SLOTS 10 /* 240 bytes */
#define MAPLE_ARANGE64_META_MAX 15 /* Out of range for metadata */
#define MAPLE_ALLOC_SLOTS (MAPLE_NODE_SLOTS - 1)
#else
/* 32bit sizes */
#define MAPLE_NODE_SLOTS 63 /* 256 bytes including ->parent */
#define MAPLE_RANGE64_SLOTS 32 /* 256 bytes */
#define MAPLE_ARANGE64_SLOTS 21 /* 240 bytes */
#define MAPLE_ARANGE64_META_MAX 31 /* Out of range for metadata */
#define MAPLE_ALLOC_SLOTS (MAPLE_NODE_SLOTS - 2)
#endif /* defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64) */
#define MAPLE_NODE_MASK 255UL
/*
* The node->parent of the root node has bit 0 set and the rest of the pointer
* is a pointer to the tree itself. No more bits are available in this pointer
* (on m68k, the data structure may only be 2-byte aligned).
*
* Internal non-root nodes can only have maple_range_* nodes as parents. The
* parent pointer is 256B aligned like all other tree nodes. When storing a 32
* or 64 bit values, the offset can fit into 4 bits. The 16 bit values need an
* extra bit to store the offset. This extra bit comes from a reuse of the last
* bit in the node type. This is possible by using bit 1 to indicate if bit 2
* is part of the type or the slot.
*
* Once the type is decided, the decision of an allocation range type or a range
* type is done by examining the immutable tree flag for the MAPLE_ALLOC_RANGE
* flag.
*
* Node types:
* 0x??1 = Root
* 0x?00 = 16 bit nodes
* 0x010 = 32 bit nodes
* 0x110 = 64 bit nodes
*
* Slot size and location in the parent pointer:
* type : slot location
* 0x??1 : Root
* 0x?00 : 16 bit values, type in 0-1, slot in 2-6
* 0x010 : 32 bit values, type in 0-2, slot in 3-6
* 0x110 : 64 bit values, type in 0-2, slot in 3-6
*/
/*
* This metadata is used to optimize the gap updating code and in reverse
* searching for gaps or any other code that needs to find the end of the data.
*/
struct maple_metadata {
unsigned char end;
unsigned char gap;
};
/*
* Leaf nodes do not store pointers to nodes, they store user data. Users may
* store almost any bit pattern. As noted above, the optimisation of storing an
* entry at 0 in the root pointer cannot be done for data which have the bottom
* two bits set to '10'. We also reserve values with the bottom two bits set to
* '10' which are below 4096 (ie 2, 6, 10 .. 4094) for internal use. Some APIs
* return errnos as a negative errno shifted right by two bits and the bottom
* two bits set to '10', and while choosing to store these values in the array
* is not an error, it may lead to confusion if you're testing for an error with
* mas_is_err().
*
* Non-leaf nodes store the type of the node pointed to (enum maple_type in bits
* 3-6), bit 2 is reserved. That leaves bits 0-1 unused for now.
*
* In regular B-Tree terms, pivots are called keys. The term pivot is used to
* indicate that the tree is specifying ranges, Pivots may appear in the
* subtree with an entry attached to the value whereas keys are unique to a
* specific position of a B-tree. Pivot values are inclusive of the slot with
* the same index.
*/
struct maple_range_64 {
struct maple_pnode *parent;
unsigned long pivot[MAPLE_RANGE64_SLOTS - 1];
union {
void __rcu *slot[MAPLE_RANGE64_SLOTS];
struct {
void __rcu *pad[MAPLE_RANGE64_SLOTS - 1];
struct maple_metadata meta;
};
};
};
/*
* At tree creation time, the user can specify that they're willing to trade off
* storing fewer entries in a tree in return for storing more information in
* each node.
*
* The maple tree supports recording the largest range of NULL entries available
* in this node, also called gaps. This optimises the tree for allocating a
* range.
*/
struct maple_arange_64 {
struct maple_pnode *parent;
unsigned long pivot[MAPLE_ARANGE64_SLOTS - 1];
void __rcu *slot[MAPLE_ARANGE64_SLOTS];
unsigned long gap[MAPLE_ARANGE64_SLOTS];
struct maple_metadata meta;
};
struct maple_alloc {
unsigned long total;
unsigned char node_count;
unsigned int request_count;
struct maple_alloc *slot[MAPLE_ALLOC_SLOTS];
};
struct maple_topiary {
struct maple_pnode *parent;
struct maple_enode *next; /* Overlaps the pivot */
};
enum maple_type {
maple_dense,
maple_leaf_64,
maple_range_64,
maple_arange_64,
};
/**
* DOC: Maple tree flags
*
* * MT_FLAGS_ALLOC_RANGE - Track gaps in this tree
* * MT_FLAGS_USE_RCU - Operate in RCU mode
* * MT_FLAGS_HEIGHT_OFFSET - The position of the tree height in the flags
* * MT_FLAGS_HEIGHT_MASK - The mask for the maple tree height value
* * MT_FLAGS_LOCK_MASK - How the mt_lock is used
* * MT_FLAGS_LOCK_IRQ - Acquired irq-safe
* * MT_FLAGS_LOCK_BH - Acquired bh-safe
* * MT_FLAGS_LOCK_EXTERN - mt_lock is not used
*
* MAPLE_HEIGHT_MAX The largest height that can be stored
*/
#define MT_FLAGS_ALLOC_RANGE 0x01
#define MT_FLAGS_USE_RCU 0x02
#define MT_FLAGS_HEIGHT_OFFSET 0x02
#define MT_FLAGS_HEIGHT_MASK 0x7C
#define MT_FLAGS_LOCK_MASK 0x300
#define MT_FLAGS_LOCK_IRQ 0x100
#define MT_FLAGS_LOCK_BH 0x200
#define MT_FLAGS_LOCK_EXTERN 0x300
#define MAPLE_HEIGHT_MAX 31
#define MAPLE_NODE_TYPE_MASK 0x0F
#define MAPLE_NODE_TYPE_SHIFT 0x03
#define MAPLE_RESERVED_RANGE 4096
#ifdef CONFIG_LOCKDEP
typedef struct lockdep_map *lockdep_map_p;
#define mt_lock_is_held(mt) lock_is_held(mt->ma_external_lock)
#define mt_set_external_lock(mt, lock) \
(mt)->ma_external_lock = &(lock)->dep_map
#else
typedef struct { /* nothing */ } lockdep_map_p;
#define mt_lock_is_held(mt) 1
#define mt_set_external_lock(mt, lock) do { } while (0)
#endif
/*
* If the tree contains a single entry at index 0, it is usually stored in
* tree->ma_root. To optimise for the page cache, an entry which ends in '00',
* '01' or '11' is stored in the root, but an entry which ends in '10' will be
* stored in a node. Bits 3-6 are used to store enum maple_type.
*
* The flags are used both to store some immutable information about this tree
* (set at tree creation time) and dynamic information set under the spinlock.
*
* Another use of flags are to indicate global states of the tree. This is the
* case with the MAPLE_USE_RCU flag, which indicates the tree is currently in
* RCU mode. This mode was added to allow the tree to reuse nodes instead of
* re-allocating and RCU freeing nodes when there is a single user.
*/
struct maple_tree {
union {
spinlock_t ma_lock;
lockdep_map_p ma_external_lock;
};
void __rcu *ma_root;
unsigned int ma_flags;
};
/**
* MTREE_INIT() - Initialize a maple tree
* @name: The maple tree name
* @__flags: The maple tree flags
*
*/
#define MTREE_INIT(name, __flags) { \
.ma_lock = __SPIN_LOCK_UNLOCKED((name).ma_lock), \
.ma_flags = __flags, \
.ma_root = NULL, \
}
/**
* MTREE_INIT_EXT() - Initialize a maple tree with an external lock.
* @name: The tree name
* @__flags: The maple tree flags
* @__lock: The external lock
*/
#ifdef CONFIG_LOCKDEP
#define MTREE_INIT_EXT(name, __flags, __lock) { \
.ma_external_lock = &(__lock).dep_map, \
.ma_flags = (__flags), \
.ma_root = NULL, \
}
#else
#define MTREE_INIT_EXT(name, __flags, __lock) MTREE_INIT(name, __flags)
#endif
#define DEFINE_MTREE(name) \
struct maple_tree name = MTREE_INIT(name, 0)
#define mtree_lock(mt) spin_lock((&(mt)->ma_lock))
#define mtree_unlock(mt) spin_unlock((&(mt)->ma_lock))
/*
* The Maple Tree squeezes various bits in at various points which aren't
* necessarily obvious. Usually, this is done by observing that pointers are
* N-byte aligned and thus the bottom log_2(N) bits are available for use. We
* don't use the high bits of pointers to store additional information because
* we don't know what bits are unused on any given architecture.
*
* Nodes are 256 bytes in size and are also aligned to 256 bytes, giving us 8
* low bits for our own purposes. Nodes are currently of 4 types:
* 1. Single pointer (Range is 0-0)
* 2. Non-leaf Allocation Range nodes
* 3. Non-leaf Range nodes
* 4. Leaf Range nodes All nodes consist of a number of node slots,
* pivots, and a parent pointer.
*/
struct maple_node {
union {
struct {
struct maple_pnode *parent;
void __rcu *slot[MAPLE_NODE_SLOTS];
};
struct {
void *pad;
struct rcu_head rcu;
struct maple_enode *piv_parent;
unsigned char parent_slot;
enum maple_type type;
unsigned char slot_len;
unsigned int ma_flags;
};
struct maple_range_64 mr64;
struct maple_arange_64 ma64;
struct maple_alloc alloc;
};
};
/*
* More complicated stores can cause two nodes to become one or three and
* potentially alter the height of the tree. Either half of the tree may need
* to be rebalanced against the other. The ma_topiary struct is used to track
* which nodes have been 'cut' from the tree so that the change can be done
* safely at a later date. This is done to support RCU.
*/
struct ma_topiary {
struct maple_enode *head;
struct maple_enode *tail;
struct maple_tree *mtree;
};
void *mtree_load(struct maple_tree *mt, unsigned long index);
int mtree_insert(struct maple_tree *mt, unsigned long index,
void *entry, gfp_t gfp);
int mtree_insert_range(struct maple_tree *mt, unsigned long first,
unsigned long last, void *entry, gfp_t gfp);
int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
void *entry, unsigned long size, unsigned long min,
unsigned long max, gfp_t gfp);
int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
void *entry, unsigned long size, unsigned long min,
unsigned long max, gfp_t gfp);
int mtree_store_range(struct maple_tree *mt, unsigned long first,
unsigned long last, void *entry, gfp_t gfp);
int mtree_store(struct maple_tree *mt, unsigned long index,
void *entry, gfp_t gfp);
void *mtree_erase(struct maple_tree *mt, unsigned long index);
void mtree_destroy(struct maple_tree *mt);
void __mt_destroy(struct maple_tree *mt);
/**
* mtree_empty() - Determine if a tree has any present entries.
* @mt: Maple Tree.
*
* Context: Any context.
* Return: %true if the tree contains only NULL pointers.
*/
static inline bool mtree_empty(const struct maple_tree *mt)
{
return mt->ma_root == NULL;
}
/* Advanced API */
/*
* The maple state is defined in the struct ma_state and is used to keep track
* of information during operations, and even between operations when using the
* advanced API.
*
* If state->node has bit 0 set then it references a tree location which is not
* a node (eg the root). If bit 1 is set, the rest of the bits are a negative
* errno. Bit 2 (the 'unallocated slots' bit) is clear. Bits 3-6 indicate the
* node type.
*
* state->alloc either has a request number of nodes or an allocated node. If
* stat->alloc has a requested number of nodes, the first bit will be set (0x1)
* and the remaining bits are the value. If state->alloc is a node, then the
* node will be of type maple_alloc. maple_alloc has MAPLE_NODE_SLOTS - 1 for
* storing more allocated nodes, a total number of nodes allocated, and the
* node_count in this node. node_count is the number of allocated nodes in this
* node. The scaling beyond MAPLE_NODE_SLOTS - 1 is handled by storing further
* nodes into state->alloc->slot[0]'s node. Nodes are taken from state->alloc
* by removing a node from the state->alloc node until state->alloc->node_count
* is 1, when state->alloc is returned and the state->alloc->slot[0] is promoted
* to state->alloc. Nodes are pushed onto state->alloc by putting the current
* state->alloc into the pushed node's slot[0].
*
* The state also contains the implied min/max of the state->node, the depth of
* this search, and the offset. The implied min/max are either from the parent
* node or are 0-oo for the root node. The depth is incremented or decremented
* every time a node is walked down or up. The offset is the slot/pivot of
* interest in the node - either for reading or writing.
*
* When returning a value the maple state index and last respectively contain
* the start and end of the range for the entry. Ranges are inclusive in the
* Maple Tree.
*/
struct ma_state {
struct maple_tree *tree; /* The tree we're operating in */
unsigned long index; /* The index we're operating on - range start */
unsigned long last; /* The last index we're operating on - range end */
struct maple_enode *node; /* The node containing this entry */
unsigned long min; /* The minimum index of this node - implied pivot min */
unsigned long max; /* The maximum index of this node - implied pivot max */
struct maple_alloc *alloc; /* Allocated nodes for this operation */
unsigned char depth; /* depth of tree descent during write */
unsigned char offset;
unsigned char mas_flags;
};
struct ma_wr_state {
struct ma_state *mas;
struct maple_node *node; /* Decoded mas->node */
unsigned long r_min; /* range min */
unsigned long r_max; /* range max */
enum maple_type type; /* mas->node type */
unsigned char offset_end; /* The offset where the write ends */
unsigned char node_end; /* mas->node end */
unsigned long *pivots; /* mas->node->pivots pointer */
unsigned long end_piv; /* The pivot at the offset end */
void __rcu **slots; /* mas->node->slots pointer */
void *entry; /* The entry to write */
void *content; /* The existing entry that is being overwritten */
};
#define mas_lock(mas) spin_lock(&((mas)->tree->ma_lock))
#define mas_unlock(mas) spin_unlock(&((mas)->tree->ma_lock))
/*
* Special values for ma_state.node.
* MAS_START means we have not searched the tree.
* MAS_ROOT means we have searched the tree and the entry we found lives in
* the root of the tree (ie it has index 0, length 1 and is the only entry in
* the tree).
* MAS_NONE means we have searched the tree and there is no node in the
* tree for this entry. For example, we searched for index 1 in an empty
* tree. Or we have a tree which points to a full leaf node and we
* searched for an entry which is larger than can be contained in that
* leaf node.
* MA_ERROR represents an errno. After dropping the lock and attempting
* to resolve the error, the walk would have to be restarted from the
* top of the tree as the tree may have been modified.
*/
#define MAS_START ((struct maple_enode *)1UL)
#define MAS_ROOT ((struct maple_enode *)5UL)
#define MAS_NONE ((struct maple_enode *)9UL)
#define MAS_PAUSE ((struct maple_enode *)17UL)
#define MA_ERROR(err) \
((struct maple_enode *)(((unsigned long)err << 2) | 2UL))
#define MA_STATE(name, mt, first, end) \
struct ma_state name = { \
.tree = mt, \
.index = first, \
.last = end, \
.node = MAS_START, \
.min = 0, \
.max = ULONG_MAX, \
.alloc = NULL, \
}
#define MA_WR_STATE(name, ma_state, wr_entry) \
struct ma_wr_state name = { \
.mas = ma_state, \
.content = NULL, \
.entry = wr_entry, \
}
#define MA_TOPIARY(name, tree) \
struct ma_topiary name = { \
.head = NULL, \
.tail = NULL, \
.mtree = tree, \
}
void *mas_walk(struct ma_state *mas);
void *mas_store(struct ma_state *mas, void *entry);
void *mas_erase(struct ma_state *mas);
int mas_store_gfp(struct ma_state *mas, void *entry, gfp_t gfp);
void mas_store_prealloc(struct ma_state *mas, void *entry);
void *mas_find(struct ma_state *mas, unsigned long max);
void *mas_find_rev(struct ma_state *mas, unsigned long min);
int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp);
bool mas_is_err(struct ma_state *mas);
bool mas_nomem(struct ma_state *mas, gfp_t gfp);
void mas_pause(struct ma_state *mas);
void maple_tree_init(void);
void mas_destroy(struct ma_state *mas);
int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries);
void *mas_prev(struct ma_state *mas, unsigned long min);
void *mas_next(struct ma_state *mas, unsigned long max);
int mas_empty_area(struct ma_state *mas, unsigned long min, unsigned long max,
unsigned long size);
/* Checks if a mas has not found anything */
static inline bool mas_is_none(struct ma_state *mas)
{
return mas->node == MAS_NONE;
}
/* Checks if a mas has been paused */
static inline bool mas_is_paused(struct ma_state *mas)
{
return mas->node == MAS_PAUSE;
}
void mas_dup_tree(struct ma_state *oldmas, struct ma_state *mas);
void mas_dup_store(struct ma_state *mas, void *entry);
/*
* This finds an empty area from the highest address to the lowest.
* AKA "Topdown" version,
*/
int mas_empty_area_rev(struct ma_state *mas, unsigned long min,
unsigned long max, unsigned long size);
/**
* mas_reset() - Reset a Maple Tree operation state.
* @mas: Maple Tree operation state.
*
* Resets the error or walk state of the @mas so future walks of the
* array will start from the root. Use this if you have dropped the
* lock and want to reuse the ma_state.
*
* Context: Any context.
*/
static inline void mas_reset(struct ma_state *mas)
{
mas->node = MAS_START;
}
/**
* mas_for_each() - Iterate over a range of the maple tree.
* @__mas: Maple Tree operation state (maple_state)
* @__entry: Entry retrieved from the tree
* @__max: maximum index to retrieve from the tree
*
* When returned, mas->index and mas->last will hold the entire range for the
* entry.
*
* Note: may return the zero entry.
*
*/
#define mas_for_each(__mas, __entry, __max) \
while (((__entry) = mas_find((__mas), (__max))) != NULL)
/**
* mas_set_range() - Set up Maple Tree operation state for a different index.
* @mas: Maple Tree operation state.
* @start: New start of range in the Maple Tree.
* @last: New end of range in the Maple Tree.
*
* Move the operation state to refer to a different range. This will
* have the effect of starting a walk from the top; see mas_next()
* to move to an adjacent index.
*/
static inline
void mas_set_range(struct ma_state *mas, unsigned long start, unsigned long last)
{
mas->index = start;
mas->last = last;
mas->node = MAS_START;
}
/**
* mas_set() - Set up Maple Tree operation state for a different index.
* @mas: Maple Tree operation state.
* @index: New index into the Maple Tree.
*
* Move the operation state to refer to a different index. This will
* have the effect of starting a walk from the top; see mas_next()
* to move to an adjacent index.
*/
static inline void mas_set(struct ma_state *mas, unsigned long index)
{
mas_set_range(mas, index, index);
}
static inline bool mt_external_lock(const struct maple_tree *mt)
{
return (mt->ma_flags & MT_FLAGS_LOCK_MASK) == MT_FLAGS_LOCK_EXTERN;
}
/**
* mt_init_flags() - Initialise an empty maple tree with flags.
* @mt: Maple Tree
* @flags: maple tree flags.
*
* If you need to initialise a Maple Tree with special flags (eg, an
* allocation tree), use this function.
*
* Context: Any context.
*/
static inline void mt_init_flags(struct maple_tree *mt, unsigned int flags)
{
mt->ma_flags = flags;
if (!mt_external_lock(mt))
spin_lock_init(&mt->ma_lock);
rcu_assign_pointer(mt->ma_root, NULL);
}
/**
* mt_init() - Initialise an empty maple tree.
* @mt: Maple Tree
*
* An empty Maple Tree.
*
* Context: Any context.
*/
static inline void mt_init(struct maple_tree *mt)
{
mt_init_flags(mt, 0);
}
static inline bool mt_in_rcu(struct maple_tree *mt)
{
#ifdef CONFIG_MAPLE_RCU_DISABLED
return false;
#endif
return mt->ma_flags & MT_FLAGS_USE_RCU;
}
/**
* mt_clear_in_rcu() - Switch the tree to non-RCU mode.
* @mt: The Maple Tree
*/
static inline void mt_clear_in_rcu(struct maple_tree *mt)
{
if (!mt_in_rcu(mt))
return;
if (mt_external_lock(mt)) {
BUG_ON(!mt_lock_is_held(mt));
mt->ma_flags &= ~MT_FLAGS_USE_RCU;
} else {
mtree_lock(mt);
mt->ma_flags &= ~MT_FLAGS_USE_RCU;
mtree_unlock(mt);
}
}
/**
* mt_set_in_rcu() - Switch the tree to RCU safe mode.
* @mt: The Maple Tree
*/
static inline void mt_set_in_rcu(struct maple_tree *mt)
{
if (mt_in_rcu(mt))
return;
if (mt_external_lock(mt)) {
BUG_ON(!mt_lock_is_held(mt));
mt->ma_flags |= MT_FLAGS_USE_RCU;
} else {
mtree_lock(mt);
mt->ma_flags |= MT_FLAGS_USE_RCU;
mtree_unlock(mt);
}
}
static inline unsigned int mt_height(const struct maple_tree *mt)
{
return (mt->ma_flags & MT_FLAGS_HEIGHT_MASK) >> MT_FLAGS_HEIGHT_OFFSET;
}
void *mt_find(struct maple_tree *mt, unsigned long *index, unsigned long max);
void *mt_find_after(struct maple_tree *mt, unsigned long *index,
unsigned long max);
void *mt_prev(struct maple_tree *mt, unsigned long index, unsigned long min);
void *mt_next(struct maple_tree *mt, unsigned long index, unsigned long max);
/**
* mt_for_each - Iterate over each entry starting at index until max.
* @__tree: The Maple Tree
* @__entry: The current entry
* @__index: The index to update to track the location in the tree
* @__max: The maximum limit for @index
*
* Note: Will not return the zero entry.
*/
#define mt_for_each(__tree, __entry, __index, __max) \
for (__entry = mt_find(__tree, &(__index), __max); \
__entry; __entry = mt_find_after(__tree, &(__index), __max))
#ifdef CONFIG_DEBUG_MAPLE_TREE
extern atomic_t maple_tree_tests_run;
extern atomic_t maple_tree_tests_passed;
void mt_dump(const struct maple_tree *mt);
void mt_validate(struct maple_tree *mt);
void mt_cache_shrink(void);
#define MT_BUG_ON(__tree, __x) do { \
atomic_inc(&maple_tree_tests_run); \
if (__x) { \
pr_info("BUG at %s:%d (%u)\n", \
__func__, __LINE__, __x); \
mt_dump(__tree); \
pr_info("Pass: %u Run:%u\n", \
atomic_read(&maple_tree_tests_passed), \
atomic_read(&maple_tree_tests_run)); \
dump_stack(); \
} else { \
atomic_inc(&maple_tree_tests_passed); \
} \
} while (0)
#else
#define MT_BUG_ON(__tree, __x) BUG_ON(__x)
#endif /* CONFIG_DEBUG_MAPLE_TREE */
#endif /*_LINUX_MAPLE_TREE_H */
