/* 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 <[email protected]> * Matthew Wilcox <[email protected]> */ #include <linux/kernel.h> #include <linux/rcupdate.h> #include <linux/spinlock.h> /* #define CONFIG_MAPLE_RCU_DISABLED */ /* * 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 … #define MAPLE_RANGE64_SLOTS … #define MAPLE_ARANGE64_SLOTS … #define MAPLE_ALLOC_SLOTS … #else /* 32bit sizes */ #define MAPLE_NODE_SLOTS … #define MAPLE_RANGE64_SLOTS … #define MAPLE_ARANGE64_SLOTS … #define MAPLE_ALLOC_SLOTS … #endif /* defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64) */ #define MAPLE_NODE_MASK … /* * 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 * MT_FLAGS_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 { … }; /* * 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 { … }; /* * 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_alloc { … }; struct maple_topiary { … }; enum maple_type { … }; enum store_type { … }; /** * 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 … #define MT_FLAGS_USE_RCU … #define MT_FLAGS_HEIGHT_OFFSET … #define MT_FLAGS_HEIGHT_MASK … #define MT_FLAGS_LOCK_MASK … #define MT_FLAGS_LOCK_IRQ … #define MT_FLAGS_LOCK_BH … #define MT_FLAGS_LOCK_EXTERN … #define MT_FLAGS_ALLOC_WRAPPED … #define MAPLE_HEIGHT_MAX … #define MAPLE_NODE_TYPE_MASK … #define MAPLE_NODE_TYPE_SHIFT … #define MAPLE_RESERVED_RANGE … #ifdef CONFIG_LOCKDEP lockdep_map_p; #define mt_lock_is_held(mt) … #define mt_write_lock_is_held(mt) … #define mt_set_external_lock(mt, lock) … #define mt_on_stack(mt) … #else typedef struct { /* nothing */ } lockdep_map_p; #define mt_lock_is_held … #define mt_write_lock_is_held … #define mt_set_external_lock … #define mt_on_stack … #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 { … }; /** * MTREE_INIT() - Initialize a maple tree * @name: The maple tree name * @__flags: The maple tree flags * */ #define MTREE_INIT(name, __flags) … /** * 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) … #else #define MTREE_INIT_EXT … #endif #define DEFINE_MTREE(name) … #define mtree_lock(mt) … #define mtree_lock_nested(mas, subclass) … #define mtree_unlock(mt) … /* * 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 { … }; /* * 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 { … }; 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_cyclic(struct maple_tree *mt, unsigned long *startp, void *entry, unsigned long range_lo, unsigned long range_hi, unsigned long *next, 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); int mtree_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp); int __mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp); 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) { … } /* Advanced API */ /* * Maple State Status * ma_active means the maple state is pointing to a node and offset and can * continue operating on the tree. * ma_start means we have not searched the tree. * ma_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). * ma_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_pause means the data within the maple state may be stale, restart the * operation * ma_overflow means the search has reached the upper limit of the search * ma_underflow means the search has reached the lower limit of the search * ma_error means there was an error, check the node for the error number. */ enum maple_status { … }; /* * 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. * * The status of the state is used to determine how the next action should treat * the state. For instance, if the status is ma_start then the next action * should start at the root of the tree and walk down. If the status is * ma_pause then the node may be stale data and should be discarded. If the * status is ma_overflow, then the last action hit the upper limit. * */ struct ma_state { … }; struct ma_wr_state { … }; #define mas_lock(mas) … #define mas_lock_nested(mas, subclass) … #define mas_unlock(mas) … /* * Special values for ma_state.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 MA_ERROR(err) … #define MA_STATE(name, mt, first, end) … #define MA_WR_STATE(name, ma_state, wr_entry) … #define MA_TOPIARY(name, 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_range(struct ma_state *mas, unsigned long max); void *mas_find_rev(struct ma_state *mas, unsigned long min); void *mas_find_range_rev(struct ma_state *mas, unsigned long max); int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp); int mas_alloc_cyclic(struct ma_state *mas, unsigned long *startp, void *entry, unsigned long range_lo, unsigned long range_hi, unsigned long *next, gfp_t gfp); 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_prev_range(struct ma_state *mas, unsigned long max); void *mas_next(struct ma_state *mas, unsigned long max); void *mas_next_range(struct ma_state *mas, unsigned long max); int mas_empty_area(struct ma_state *mas, unsigned long min, unsigned long max, unsigned long size); /* * 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); static inline void mas_init(struct ma_state *mas, struct maple_tree *tree, unsigned long addr) { … } static inline bool mas_is_active(struct ma_state *mas) { … } static inline bool mas_is_err(struct ma_state *mas) { … } /** * 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 __always_inline void mas_reset(struct ma_state *mas) { … } /** * 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) … #ifdef CONFIG_DEBUG_MAPLE_TREE enum mt_dump_format { … }; extern atomic_t maple_tree_tests_run; extern atomic_t maple_tree_tests_passed; void mt_dump(const struct maple_tree *mt, enum mt_dump_format format); void mas_dump(const struct ma_state *mas); void mas_wr_dump(const struct ma_wr_state *wr_mas); void mt_validate(struct maple_tree *mt); void mt_cache_shrink(void); #define MT_BUG_ON(__tree, __x) … #define MAS_BUG_ON(__mas, __x) … #define MAS_WR_BUG_ON(__wrmas, __x) … #define MT_WARN_ON(__tree, __x) … #define MAS_WARN_ON(__mas, __x) … #define MAS_WR_WARN_ON(__wrmas, __x) … #else #define MT_BUG_ON … #define MAS_BUG_ON … #define MAS_WR_BUG_ON … #define MT_WARN_ON … #define MAS_WARN_ON … #define MAS_WR_WARN_ON … #endif /* CONFIG_DEBUG_MAPLE_TREE */ /** * __mas_set_range() - Set up Maple Tree operation state to a sub-range of the * current location. * @mas: Maple Tree operation state. * @start: New start of range in the Maple Tree. * @last: New end of range in the Maple Tree. * * set the internal maple state values to a sub-range. * Please use mas_set_range() if you do not know where you are in the tree. */ static inline void __mas_set_range(struct ma_state *mas, unsigned long start, unsigned long last) { … } /** * 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_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) { … } static inline bool mt_external_lock(const struct maple_tree *mt) { … } /** * 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_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) { … } static inline bool mt_in_rcu(struct maple_tree *mt) { … } /** * 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) { … } /** * 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) { … } static inline unsigned int mt_height(const struct maple_tree *mt) { … } 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 start the search from. Subsequently used as iterator. * @__max: The maximum limit for @index * * This iterator skips all entries, which resolve to a NULL pointer, * e.g. entries which has been reserved with XA_ZERO_ENTRY. */ #define mt_for_each(__tree, __entry, __index, __max) … #endif /*_LINUX_MAPLE_TREE_H */
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